IPAC2015 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOXGB2	Commissioning and Operation of 12 GeV CEBAF	linac, operation, cryomodule, SRF	1
	A. Freyberger JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 The Continuous Electron Beam Accelerator Facility (CEBAF) located at the Thomas Jefferson National Accelerator Laboratory (JLab) has been recently upgraded to deliver continuous electron beams to the experimental users at a maximum energy of 12 GeV, three times the original design energy of 4 GeV. This paper will present an overview of the upgrade, referred to as the 12GeV upgrade, and highlights from recent beam commissioning results.
	Slides MOXGB2 [4.359 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOXGB2
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MOBB2	Fabrication of TESLA-shape 9-cell Cavities at KEK for Studies on Mass-Production in Collaboration with Industries	SRF, cryomodule, status, controls	31
	T. Saeki, H. Hayano KEK, Ibaraki, Japan
	The construction of the new Center-of-Innovation (COI) buiding started at KEK from 2014 for the studies of mass-production of Superconducting-RF accelerators in collaboration with industries. The COI buiding is sitting next to the existing KEK-STF building and will include various Superconducting-RF facilities like clean-room for cavity-string assembly, cryomodule-assembly facility, cryogenic system, vertical-test facility, cryomodule-test facility, input-coupler processing facility, cavity Electro-Polishing (EP) facility, and control-room/office-rooms in the dimension of 80 m x 30 m. The purpose of this new SRF facilities is to establish a close collaboration between SRF researchers and industries in order to prepare for the upcoming large-scale future SRF project, like ILC. This article reports the fabricaion of four TESLA-shape 9-cell cavities for the commisioning of these new facilities. Details of the fabrication of these four cavities will be presented.
	Slides MOBB2 [3.983 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOBB2
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MOAD1	Development of High Gradient RF System for J-PARC Upgrade	impedance, operation, proton, acceleration	50
	C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii KEK, Ibaraki, Japan M. Nomura, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan A. Schnase GSI, Darmstadt, Germany
	A new 5-cell cavity has been developed for the upgrade of the J-PARC Main Ring. In the cavity, high impedance magnetic alloy - Finemet FT3L, cores are loaded. The cavity was installed and has been used for the 250 kW beam operation. The cavity is operated with the RF voltage of 70 kV which is two times higher voltage than the present cavities. Eight more cavities will be assembled and installed in the next two years to increase the repetition rate of the Main Ring. This paper describes status of cavity operation under the beam loading and status of the mass productions of the cavities.
	Slides MOAD1 [2.551 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOAD1
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MOAD2	RF Breakdown of 805 MHz Cavities in Strong Magnetic Fields	Windows, operation, controls, klystron	53
	D.L. Bowring, A.V. Kochemirovskiy, M.A. Leonova, A. Moretti, M.A. Palmer, D.W. Peterson, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA A.A. Haase SLAC, Menlo Park, California, USA P.G. Lane, Y. Torun Illinois Institute of Technology, Chicago, Illinois, USA D. Stratakis BNL, Upton, Long Island, New York, USA
	Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. We have measured the breakdown rate in several RF cavities operating at several frequencies. Cavities operating within solenoidal magnetic fields B > 0.25 T show an increased RF breakdown rate at lower gradients compared with similar operation when B = 0 T. Ultimately, this breakdown behavior limits the maximum safe operating gradient of the cavity. Beyond ionization cooling, this issue affects the design of photoinjectors and klystrons, among other applications. We have built an 805 MHz pillbox-type RF cavity to serve as an experimental testbed for this phenomenon. This cavity is designed to study the problem of RF breakdown in strong magnetic fields using various cavity materials and surface treatments, and with precise control over sources of systematic error. We present results from tests in which the cavity was run with all copper surfaces in a variety of magnetic fields.
	Slides MOAD2 [10.792 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOAD2
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MOBD2	Design and Prototyping of HL-LHC Double Quarter Wave Crab Cavities for SPS Test	luminosity, proton, simulation, HOM	64
	S. Verdú-Andrés, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, Q. Wu, B. P. Xiao BNL, Upton, Long Island, New York, USA L. Alberty, K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, N. Kuder, R. Leuxe, C. Zanoni CERN, Geneva, Switzerland S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA Z. Li SLAC, Menlo Park, California, USA A. Ratti LBNL, Berkeley, California, USA
	Funding: Work supported by US DOE via US LARP program, through BSA LLC contract No.DE-AC02-98CH10886 and by EU FP7 HiLumi LHC grant No.284404. Used NERSC resources by US DOE contract No.DE-AC02-05CH11231. The LHC high luminosity project envisages the use of the crabbing technique for increasing and levelling the LHC luminosity. Double-Quarter Wave (DQW) resonators are compact cavities especially designed to meet the technical and performance requirements for LHC beam crabbing. A couple of DQW crab cavities are under preparation and will be tested with beam in the Super Proton Synchrotron (SPS) of CERN by 2017. This paper describes the design and prototyping of DQW crab cavities for the SPS test.
	Slides MOBD2 [6.909 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOBD2
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MOBD3	Development of a 9 MHz 15 kW Solid-state CW Amplifier for RHIC	impedance, network, resonance, feedback	67
	S.C. Dillon Tomco Technologies, Stepney, South Australia, Australia
	This paper describes the technical details of the development of a high-power solid-state amplifier for Brookhaven Laboratory. The amplifier must withstand short duration events of 100% full-power reflection, and also must guarantee delivery of continuous power into any load impedance at any angle.
	Slides MOBD3 [10.800 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOBD3
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MOPWA008	Status of TraceWin Code	simulation, linac, space-charge, diagnostics	92
	D. Uriot, N. Pichoff CEA/DSM/IRFU, France
	Well known in the community of high-intensity linear accelerators, the transport code TraceWin * is able to simulate a beam from the source to the target using either simple linear model or multiparticle simulations including 2D or 3D space-charge. Continuously developed at CEA Saclay since 15 years, it is today the reference code for projects such IFMIF, ESS, MYRRHA, SPIRAL2, IPHI … The accuracy of his predictions associated with an original and powerful GUI and its numerous features have made its success, with a community of 200 users worldwide. It is now used on a larger perimeter that its initial skills. The aim of this paper is to summarize the TraceWin capabilities, including implemented last ones. * http://irfu.cea.fr/Sacm/logiciels/
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MOPWA022	Influence of Transient Beam Loading on the Longitudinal Beam Dynamics at BESSY VSR	beam-loading, synchrotron, damping, simulation	141
	M. Ruprecht, P. Goslawski, A. Jankowiak, A. Neumann, M. Ries, G. Wüstefeld HZB, Berlin, Germany T. Weis DELTA, Dortmund, Germany
	BESSY VSR, a scheme where 1.7 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring has recently been proposed . The strong longitudinal bunch focusing is achieved by superconducting high gradient RF cavities. If the bunch fill pattern exhibits a significant inhomogeneity, e.g. due to gaps, transient beam loading causes a distortion of the longitudinal phase space which is different for each bunch. The result are variations along the fill pattern in synchronous phase, synchrotron frequency and bunch shape. This paper presents investigations of transient beam loading and depicts the consequences on bunch length, phase stability and longitudinal multi-bunch oscillations for the projected setup of BESSY VSR. G. Wüstefeld, A. Jankowiak, J. Knobloch, M. Ries, Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proceedings of IPAC2011, San Sebastián, Spain
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MOPWA027	Generic Settings Generation for FAIR: First Experience at SIS18	resonance, framework, controls, operation	156
	D. Ondreka, J. Fitzek, H. Liebermann, R. Müller GSI, Darmstadt, Germany
	The accelerators of the FAIR facility will be operated using a new control system presently under design at GSI. One of its major components, the module for settings generation and management, is based on the framework LSA developed at CERN. Its task is the provision and administration of set values for all devices in the FAIR facility. The set values for any accelerator are derived from a machine model, implemented by accelerator physicists using the features of the LSA framework. In view of the large number of accelerators in the FAIR facility, the aim is to develop a generic model, applicable to any of those machines. This requires the introduction of an additional logical layer on top of the LSA framework, ensuring the coherence of the modeling strategy across all accelerators. Following this design concept, a prototype of the FAIR settings management system has been realized at GSI, providing support for a large number of operation modes relevant for the later operation of FAIR. The prototype has been used extensively during recent machine experiments with the synchrotron SIS18, performed both to benchmark the machine model and to support further machine developments for FAIR.
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MOPWA031	A New Approach for Resistive Wakefield Calculations in Time Domain	wakefield, impedance, simulation, controls	168
	A.V. Tsakanian, H. De Gersem, E. Gjonaj, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany M. Dohlus, I. Zagorodnov DESY, Hamburg, Germany
	We report on a new numerical technique for the computation of the wakefields excited by ultra-short bunches in the structures with walls of finite conductivity. The developed 3D numerical method is fully time domain. It is based on special Staggered Finite Volume Time Domain (SFVTD) method and has no numerical dispersion in all three axial directions simultaneously. This results in large saving in computational time as well as improved accuracy. The resistive boundary model applies Surface Impedance Boundary Condition (SIBC) evaluation in time domain and covers boundary effects like frequency dependent conductivity, surface roughness and metal oxidation. A good agreement between numerical simulation and perturbation theory is obtained. In addition the new method allows implementation of moving mesh approach that considerably reduces requirements on computational resources. The developed method is especially effective for short range resistive wakefield calculations excited by ultra-short bunches used in FEL based LINACs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA031
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MOPWA032	Aspects of SRF Cavity Optimization for BESSY-VSR Upgrade	HOM, SRF, higher-order-mode, storage-ring	171
	T. Galek, K. Brackebusch, T. Flisgen, J. Heller, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany B.D. Isbarn, B. Riemann, M. Sommer, T. Weis DELTA, Dortmund, Germany
	Funding: Work supported by Federal Ministry for Research and Education BMBF under contract 05K13HR1. In this work we present a preliminary study of a long chain of cavities and some aspects involved in the optimization procedure. It is important to numerically model and optimize the SRF cavities with respect to external quality factors of the most dangerous higher order modes. BESSY-VSR is an upgrade scheme for the existing BESSY II storage ring aiming to simultaneously support variable electron pulse lengths. Currently, BESSY II supports long 15 ps bunches in the standard user optics configuration and short 1.5 ps bunches in a so-called low-α optics mode. In order to develop BESSY II into a variable electron pulse length storage ring, additional two sets of SRF higher-harmonic cavities will be installed. The present RF acceleration system operates at 0.5 GHz and the additional 3rd harmonic and 3rd sub-harmonic cavities will operate at 1.5 GHz and 1.75 GHz, respectively. These cavities are essential to produce short 1.5 ps bunches with a design current of up to 0.8 mA per bunch. The total current in the storage ring is limited by the higher order mode damping capabilities of the SRF cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA032
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MOPWA033	Yacs - A New 2.5D FEM Eigenmode Solver for Axisymmetric RF-Structures	multipole, dipole, quadrupole, software	175
	B.D. Isbarn, B. Riemann, M. Sommer, T. Weis DELTA, Dortmund, Germany
	Funding: Work supported by the BMBF under contract no. 05K13PEB Most feasibility studies for modern accelerator concepts, including superconducting multicell RF-cavity-resonators in circular accelerators, depend on computing a large number of eigenmode frequencies and field patterns to obtain typical figures of merit. This task includes computational intensive numerical studies. To obtain the full eigenfrequency spectra most of these studies are performed in 3D, require a great amount of computation resources and thus are limited to a few hundred or thousand eigenmodes. To overcome this issue, some codes make use of the axisymmetric geometry of most of the RF-cavity-resonator structures and solve the problem in 2D. Solving in 2D however reduces the eigenmode spectra to eigenmodes with no azimuthal dependencies (so called monopole-modes). Due to the lack of freely available and easy to use 2.5D eigenmode solvers which are able to solve for the full 3D field in a reduced 2.5 dimensional problem, we developed yet another cavity solver (Yacs), a simple FEM based solver capable of solving for the full 3D eigenmodes of axisymmetric problems while only requiring a fraction of the computation resources required by most modern 3D codes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA033
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MOPWA037	Mirror Symmetric Chicane-Type Emittance Exchange Beamline with Two Deflecting Cavities	quadrupole, emittance, focusing, dipole	190
	V. Balandin, W. Decking, N. Golubeva DESY, Hamburg, Germany
	Among optical systems for transverse-to-longitudinal emittance exchange (EEX) chicane-type beamlines are of keen interest, because they do not alter the beam propagation direction. Several designs of such beamlines involving a single dipole-mode cavity (TDC) are known. In this paper we present a chicane-type EEX beamline utilizing two TDCs instead of one. The advantages of this beamline are that it is mirror symmetric and does not require an additional accelerating mode cavity for compensation of the so-called thick-lens effect, and, in the compact design, it allows better control of the beam focusing in the non-bending plane than known beamlines with one TDC.
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MOPWA040	Virtual Cavity Probe Generation using Calibrated Forward and Reflected Signals	coupling, controls, flattop, laser	200
	S. Pfeiffer, V. Ayvazyan, J. Branlard, L. Butkowski, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany R. Rybaniec Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
	The European X-ray free electron laser requires a high-precision control of accelerating fields to ensure a stable photon generation. Its low level radio frequency system, based on the MicroTCA.4 standard, detects the probe, forward and reflected signals for each cavity. While the probe signal is used to control the accelerating fields, a combination of the forward and reflected signals can be used to compute a virtual probe, whose accuracy is comparable to the directly sampled probe. This requires the removal of cross-coupling effects between the forward and reflected signals. This paper presents the precise generation of a virtual probe using an extended method of least squares. The virtual probe can then be used for precise field control in case the probe signal is missing or corrupted. It can also be used to detect any deviation from the nominal probe profile.
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MOPWA056	Transverse Multi-Pass Beam Breakup Simulation for KEK ERL Light Source	HOM, simulation, linac, cryomodule	248
	S. Chen, N. Nakamura, M. Shimada, D. Zhou KEK, Ibaraki, Japan S. Huang, K.X. Liu PKU, Beijing, People's Republic of China
	In this paper, the multi-pass BBU of such a high energy ERL is studied based on the simulation on a 3 GeV ERL light source proposed by KEK.
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MOPWA058	Measurement Results of the Impedance of the RF-cavity at the RCS in J-PARC	impedance, injection, kicker, proton	255
	Y. Shobuda, H. Harada, H. Hotchi JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The kicker impedance dominates at the RCS in J-PARC. Recently, we observe beam instabilities, which are not explained by the kicker. As a candidate causing the beam instability, the impedance of the RF-cavity is measured. The longitudinal impedance is measured by stretching a single-wire inside the cavity. On the other hand, the measurement of the transverse impedance is done by horizontally shifting the single-wire, due to the accuracy problem. The measured impedance is too low to explain the beam instability.
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MOPWA072	Emittance Exchange Beam Line Design In THU Accelerator Lab	emittance, quadrupole, simulation, electron	285
	Q. Gao, H.B. Chen, Y.-C. Du, W.-H. Huang, J. Shi TUB, Beijing, People's Republic of China W. Gai ANL, Argonne, Illinois, USA
	Funding: National Natural Science Foundation of China Emittance exchange (EEX) provides a novel tool to enhance the phase space manipulation techniques. Based on Tsinghua Thomson scattering experimental platform, this study presented a beam line design for exchanging the transverse and longitudinal emittance of an electron bunch. This beam line consists of a 2.856 GHz half-one-half cell deflecting cavity with no axis offset and two doglegs. In this paper, by optimizing the beam envelope parameter for Tsinghua Thomson scattering source, we report the theoretical analysis and a good particle tracking simulation result about emittance exchange and longitudinal shaping.
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MOPJE019	Categorization and Estimation of Possible Deformation in Emittance Exchange based Current Profile Shaping	emittance, wakefield, acceleration, collective-effects	317
	G. Ha, M.-H. Cho, W. Namkung POSTECH, Pohang, Kyungbuk, Republic of Korea W. Gai, G. Ha, K.-J. Kim, J.G. Power ANL, Argonne, Illinois, USA
	Funding: This work is partly supported by POSTECH BK²¹⁺ program and Argonne National Laboratory Shaping the current profile is one of the important issues in collinear wakefield acceleration. In the emittance exchange based shaping technique, the shaped current profile seriously depends on the incoming beam and beam line parameters. To design the beam and beam line properly, it is important to estimate the deformation in the shaped current profile. There are several different deformation types whose level depend on deformation parameter. We categorize the possible deformation types and observe the deformation patterns of the current profile depending on its type and the deformation parameter.
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MOPJE020	High Resolution Longitudinal Property Measurement using Emittance Exchange Beam Line	emittance, quadrupole, space-charge, collective-effects	320
	G. Ha, M.-H. Cho, W. Namkung POSTECH, Pohang, Kyungbuk, Republic of Korea W. Gai, G. Ha, K.-J. Kim, J.G. Power ANL, Argonne, Illinois, USA
	Most of longitudinal measurement techniques introduce the transverse-longitudinal correlation because it is very hard to measure the longitudinal properties directly. This correlation is necessary to observe the longitudinal property through the transverse screen, but initial transverse components of the beam restrict the measurement. It is possible to overcome this intrinsic limit using emittance exchange beam line which makes transverse properties at the downstream only depend on longitudinal properties at the upstream. We present the new idea to measure the longitudinal properties using the emittance exchange beam line and preliminary simulation results.
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MOPJE031	Field Map Model for the ESS Linac Simulator	linac, proton, framework, space-charge	348
	E. Laface ESS, Lund, Sweden I. List Cosylab, Ljubljana, Slovenia
	The proton beam driving the spallation process at the European Spallation Source, in Lund, will be accelerated and delivered onto a tungsten target by a linac. This linac is composed of four different families of accelerating structures: adrift tube linac, a section of spoke resonators and two sections of elliptical cavities for the particles’ medium and high relativistic β. These structures provide 99.8% of the total energy gained by the beam along the accelerator. It is necessary, then, to have an accurate model describing the physics of the cavities in the ESS Linac Simulator (ELS), which isthe online model that will simulate the accelerator during operation. Here, we present an RF-cavity model based on the field maps that we implemented in ELS, showing a maximum 10% deviation from TraceWin in the horizontal, vertical and longitudinal planes.
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MOPJE037	Study and Comparison of Mode Damping Strategies for the UA9 Cherenkov Detector Tank	damping, vacuum, detector, resonance	366
	A. Danisi, F. Caspers, R. Losito, A. Masi, B. Salvant, C. Vollinger CERN, Geneva, Switzerland T. Demma, P. Lepercq LAL, Orsay, France
	In the framework of the UA9 experiment, the Cherenkov detector is useful to measure the amount of particles deflected by a bent crystal, proving the crystal collimation principle. The tank used to host this device is taken as a case study for an in-depth analysis of different damping strategies for electromagnetic modes which otherwise would give rise to important beam-coupling impedance contributions. Such strategies involve the use of ferrite, damping resistors and a mode-coupler, a solution which intercepts the modes inside the cavity but damps the related power outside the vacuum tank (potentially avoiding heating). Such solutions are discussed through experimental measurements and the relative quality factor is taken as a figure of merit.
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MOPJE053	NSLS-II Beam Lifetime Measurements and Modeling	scattering, emittance, coupling, lattice	416
	B. Podobedov, W.X. Cheng, Y. Hidaka, H.-C. Hseuh, G.M. Wang BNL, Upton, Long Island, New York, USA
	NSLS-II is a recently constructed 3 GeV synchrotron light source with design horizontal emittance values in sub-nm range. Achieving good beam lifetime is critically important for NSLS-II as it is closely tied in to such important operational aspects as top-off injection frequency, injector components wear, radiation protection and control, and others. In this paper we present lifetime-related commissioning results, describe our present understanding of beam lifetime at NSLS-II and extrapolate our models to the fully built-up machine operating at 500 mA design beam current.
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MOPJE059	Tests of Wakefield-Free Steering at ATF2	wakefield, emittance, extraction, alignment	438
	A. Latina, J. Pfingstner, D. Schulte CERN, Geneva, Switzerland E. Adli University of Oslo, Oslo, Norway N. Fuster-Martínez IFIC, Valencia, Spain J. Snuverink JAI, Egham, Surrey, United Kingdom
	Charge-dependent effects on the orbit and on the beam size affect the performance of the Accelerator Test Facility (ATF2) in a non-negligible way. Until now small beam sizes have only been achieved running with a beam charge significantly smaller than the nominal value. These detrimental effects on the beam have been attributed to wakefields, in the cavity BPMs, in the multi-Optical Transition Radiation (OTR) systems as well as in other components of the beamline. The successful tests of a Wakefield-free Steering (WFS) algorithm at FACET have encouraged performing tests of the same correction scheme at ATF2. The performance of the algorithm has been simulated in detail, including several realistic imperfection scenarios, including charge-dependent BPMs resolution, and incoming injection error and position jitters, which are described in this paper. Tests of WFS have been performed at ATF2 during December 2014. The results are discussed here.
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MOPJE064	Beam Impedance Optimization of the TOTEM Roman Pots	impedance, detector, simulation, vacuum	452
	N. Minafra CERN, Geneva, Switzerland
	The TOTEM experiment has been designed to measure the total proton-proton cross section and to study elastic and diffractive scattering at the LHC energy. The measurement requires detecting protons at distances as small as 1 mm from the beam center: TOTEM uses Roman Pots (RP), special beam pipe insertions, to move silicon detectors close to the beams to detect particles very near the beam axis. In the first period of running of the LHC no problems were detected with retracted Roman Pots and during insertions in special runs; however, during close insertions to highest intensity beam, impedance heating has been observed. After the LS1 the LHC beam current will increase and the equipment that can interact with the beam needed to be optimized. A new RP, optimized to minimize the beam coupling, has been designed with the help of CST Particle Studio; a prototype has been used to test the simulation results in the laboratory with wire and probe measurements. Furthermore, in both the old and the new RPs, new ferrites have been installed. The new ferrite material has a higher Curie temperature than the one used before LS1 and a thermal treatment at 1000°C has been applied to reduce the out-gassing.
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MOPJE069	General Functionality for Turn-Dependent Element Properties in SixTrack	simulation, HOM, collimation, optics	468
	K.N. Sjobak, H. Burkhardt, R. De Maria, A. Mereghetti, A. Santamaría García CERN, Geneva, Switzerland
	In order to facilitate studies of how dynamically changing element attributes affect the dynamics of the beam and beam losses, the functionality for dynamic kicks (DYNK) of SixTrack has been significantly extended. This functionality can be used for the simulation of dynamic scenarios, such as when crab cavities are switched on, orbit bumps are applied, optics are changed, or failures occur. The functionality has been extended with a more general and flexible implementation, such that arbitrary time-dependent functions can be defined and applied to different attributes of families or individual elements, directly from the user input files. This removes the need for source code manipulation, and it is compatible with LHC@Home which offers substantial computing resources from volunteers. In this paper, the functionality and implementation of DYNK is discussed, along with examples of application to the HL-LHC crab cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE069
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MOPJE072	Simulations and Measurements of Longitudinal Coupled-bunch Instabilities in the CERN PS	feedback, synchrotron, luminosity, impedance	479
	L. Ventura, H. Damerau, M. Migliorati, G. Sterbini CERN, Geneva, Switzerland M. Migliorati, L. Ventura INFN-Roma1, Rome, Italy M. Migliorati University of Rome La Sapienza, Rome, Italy L. Ventura University of Rome "La Sapienza", Rome, Italy
	Among various and challenging objectives of the LHC Injectors Upgrade project (LIU), one aim is to double the beam intensity of the CERN Proton Synchrotron (PS) in order to achieve the integrated luminosity target of the High-Luminosity LHC project (HL-LHC). A known limitation to reach the required high intensity is caused by the longitudinal coupled-bunch oscillations developing above the transition energy. The unwanted oscillations induce large bunch-to-bunch intensity variations not compatible with the specifications of the future LHC-type beams. A wide-band longitudinal damper has been installed in the PS to suppress these instabilities and is going to be commissioned. A measurement campaign of coupled-bunch oscillations has been launched to substantiate the extrapolations and predictions for the future High Luminosity LHC beam with the final aim to determine the maximum intensity that could be provided to the LHC. In parallel a Simulink© model of the PS is going to be implemented to predict the machine behavior in the parameter space of LIU and to be used during the beam commissioning and optimization of the feedback system.
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MOPJE076	Multi-objective Genetic Optimization with the General Particle Tracer (GPT) Code	solenoid, emittance, factory, target	492
	S.B. van der Geer, M.J. de Loos Pulsar Physics, Eindhoven, The Netherlands
	In a typical design process there are a large number of variables, external constraints, and multiple conflicting objectives. Examples of the latter are short pulse, high charge, low emittance and low price. The classical solution to handle such problems is to combine all objectives into one merit function. This however implicitly assumes that the tradeoffs between all objectives are a-priori known. Especially in the early design stages this is hardly ever the case. A popular solution to this problem is to switch to multi-objective genetic optimization algorithms. This class of algorithms solves the problem by genetically optimising an entire population of sample solutions. Selection and recombination operators are defined such that the output, the so-called Pareto front, only includes solutions that are fully optimized where no objective can be improved without degrading any other. Here we present numerical studies and practical test runs of the genetic optimizer built into the General Particle Tracer (GPT) code.
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MOPJE081	Longitudinal Stability in Multi-Harmonic Accelerating Cavities	acceleration, accelerating-gradient, cathode, controls	506
	R.M. Jones, L.R. Carver UMAN, Manchester, United Kingdom J.L. Hirshfield Yale University, Physics Department, New Haven, CT, USA Y. Jiang Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
	Accelerating cavities that excite multiple modes at integer harmonics of the fundamental frequency can potentially be used to limit the effects of rf breakdown and pulsed surface heating at high accelerating gradients. Understanding the longitudinal stability and the acceptance of such a cavity is important to their development and use. The general Hamiltonian for longitudinal stability in multi harmonic cavities is derived and the particle dynamics are explored.
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MOPJE083	Implications of Manufacturing Errors on Higher Order Modes and on Beam Dynamics in the ESS Linac	HOM, coupling, linac, wakefield	514
	A. Farricker, R.M. Jones UMAN, Manchester, United Kingdom S. Molloy ESS, Lund, Sweden
	The European Spallation Source (ESS) in Lund, Sweden, will be a facility for fundamental physics studies of atomic structure using a spallation source of unparalleled brightness. To achieve this end, protons will be accelerated up to 2 GeV using a suite of cavities. Here we focus on the Medium Beta (β =0.67) elliptical superconducting cavities and we assess the influence of potential errors in fabrication to shift eigenmode frequencies onto an harmonic of the bunch frequency. If this occurs, and countermeasures are not adopted, the beam quality will be appreciably diluted . We provide details on the geometrical parameters which are particularly sensitive to frequency errors from intensive finite element simulations of the electromagnetic fields. A circuit model is also employed to rapidly assess the shift in the eigenmodes from their anticipated design values due a variety of potential errors. Aaron Farricker et al, Physics Procedia, Proceedings of HOMSC14 (in press), 2014.
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MOPMA006	Modeling RF Feedback in Elegant for Bunch-Lengthening Studies for the Advanced Photon Source Upgrade	feedback, injection, storage-ring, impedance	540
	T.G. Berenc, M. Borland ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice includes a passive bunch-lengthening cavity to alleviate lifetime and emittance concerns. Feedback in the main radio-frequency (rf) system affects the overall impedance presented to the beam in this double rf system. To aid beam stability studies, a realistic model of rf feedback has been developed and implemented in elegant and Pelegant.
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MOPMA007	Tracking Studies of a Higher-Harmonic Bunch-Lengthening Cavity for the Advanced Photon Source Upgrade	simulation, feedback, timing, impedance	543
	M. Borland, T.G. Berenc, R.R. Lindberg, A. Xiao ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source (APS) multi-bend achromat (MBA) lattice will require a bunch-lengthening cavity to decrease the effects of Touschek scattering on the beam lifetime and of intrabeam scattering on the beam emittance. Using ELEGANT, we've performed tracking studies of a passive, i.e. beam-driven, fourth-harmonic cavity in the MBA lattice, including the predicted longitudinal impedance of the ring. The studies include an exploration of the required detuning and loaded Q of the main rf cavities and the harmonic cavity in order to stabilize the beam and achieve significant lengthening. We also studied the effects of bunch population variation and missing bunches. The computed bunch profiles are used for computation of the Touschek lifetime, verifying the beneficial effects in detail.
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MOPMA009	Improvements in Modeling of Collective Effects in ELEGANT	simulation, collective-effects, lattice, impedance	549
	M. Borland, R.R. Lindberg, A. Xiao ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. ELEGANT has long had the ability to model collective effects in various ways, including beam-driven cavity modes, short-range wakes, and coherent synchrotron radiation. Recently, we made improvements specifically targeting simulations that require multiple bunches in storage rings. The ability to simulate long-range, non-resonant wakes was added, which can be used for example to study the effect of the resistive wall wake and multibunch instabilities. We also improved the implementation of short-range and resonant wakes to make them more efficient for multibunch simulations. Finally, improvements in the parallel efficiency were made that allow taking advantage of larger parallel resources.
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MOPMA016	Coupler RF Kick in the Input 1.3 GHz Accelerating Cavity of the LCLS-II Linac	focusing, HOM, accelerating-gradient, emittance	571
	A. Lunin, N. Solyak, A.I. Sukhanov, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Main and HOM couplers break the cavity axial symmetry, distort RF field and, thus, create a transverse kick, even for a particle moving along the cavity axes. Dependence of a kick on the RF phase causes a beam emittance dilution and degrade the FEL radiation quality. The transverse kick is most dangerous for a beam passing through the first accelerating structure of a linac, where particles energy and their relativistic mass are low. In the paper we analyze the coupler RF kick in the first accelerating structure of the LCSL-II linac.
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MOPMA018	Simulation of Multipacting in SC Low Beta Cavities at FNAL	simulation, niobium, operation, linac	579
	G.V. Romanov, P. Berrutti, T.N. Khabiboulline Fermilab, Batavia, Illinois, USA
	Proton Improvement Plan-II at Fermilab is a plan for improvements to the accelerator complex aimed at providing a beam power capability of at least 1 MW on target at the initiation of LBNE (Long Base Neutrino Experiment) operations. The central element of the PIP-II is a new 800 MeV superconducting linac, injecting into the existing Booster. Multipacting affects superconducting RF cavities in the entire range from high energy elliptical cavities to coaxial resonators for low-beta applications. This work is focused on multipacting study in the low-beta 325 MHz spoke cavities; namely SSR1 and SSR2, which are especially susceptible to the phenomena. The extensive simulations of multipacting in the cavities with updated material properties and comparison of the results with experimental data helped us to improve overall reliability and accuracy of these simulations. Our practical approach to the simulations is described in details. For SSR2, which has a high multipacting barrier right at the operating power level, some changes of the cavity shape to mitigate this harmful phenomenon are proposed.
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MOPMA026	Proposed Cavity for Reduced Slip-Stacking Loss	booster, injection, emittance, beam-loading	600
	J.S. Eldred Indiana University, Bloomington, Indiana, USA J.S. Eldred, R.M. Zwaska Fermilab, Batavia, Illinois, USA
	This paper employs a novel dynamical mechanism to improve the performance of slip-stacking. Slip-stacking in an accumulation technique used at Fermilab since 2004 which nearly double the proton intensity. During slip-stacking, the Recycler or the Main Injector stores two particles beams that spatially overlap but have different momenta. The two particle beams are longitudinally focused by two 53 MHz 100 kV RF cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV RF cavity, with a frequency at the double the average of the upper and lower main RF frequencies. In simulation, we find the proposed RF cavity significantly enhances the stable bucket area and reduces slip-stacking losses under reasonable injection scenarios. We quantify and map the stability of the parameter space for any accelerator implementing slip-stacking with the addition of a harmonic RF cavity.
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MOPMA047	Nonlinear Beam Dynamics Studies of the Next Generation Strong Focusing Cyclotrons as Compact High Brightness, Low Emittance Drivers	cyclotron, focusing, proton, wakefield	656
	S. Assadi, P.M. McIntyre, A. Sattarov Texas A&M University, College Station, Texas, USA N. Pogue PSI, Villigen, Villigen, Switzerland
	Funding: Work is partially supported by grants from the State of Texas (ASE) & the Michelle foundation. The Strong Focusing Cyclotron development at Texas A&M University has evolved from stacks of cyclotrons to a single layer high brightness, low emittance to produce greater than 10 mA of proton beam to a desired target at 800 MeV. The latest design has a major geometric design optimization of strong focusing quadrupoles and a modified algorithm of high gradient cavities to address the small turn separation, and interaction of radially neighboring bunches and reduced the number of turns necessary to reach the desired final energy under control conditions. In this paper, we present the new design, physics of nonlinear synchrobetratron coupling, mνh+nνv=p causing beam blow-up in other form of cyclotrons and how we have resolved it. The cavity beam loading and space charge effects of multi turns at low energies to reduce losses are discussed.
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MOPMN002	Advances in Parallel Finite Element Code Suite ACE3P	simulation, radiation, SRF, electron	702
	C.-K. Ng, L. Ge, C. Ko, O. Kononenko, Z. Li, L. Xiao SLAC, Menlo Park, California, USA J. Qiang LBNL, Berkeley, California, USA
	Funding: Work supported by the US DOE under contract DE-AC02-76SF00515. New capabilities in SLAC's parallel finite element electromagnetics simulation suite ACE3P are reported. These include integrated electromagnetic (Omega3P), thermal and mechanical (TEM3P) modules for multi-physics modeling, an interface to particle-material interaction codes for calculation of radiation effects due to dark current generation (Track3P), and coupled electromagnetic (ACE3P) and beam dynamics (IMPACT) simulation. Results from these applications are presented.
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MOPMN013	Simulation of Beam-Induced Plasma in Gas Filled Cavities	plasma, ion, simulation, electron	731
	K. Yu, V. Samulyak SBU, Stony Brook, USA M. Chung UNIST, Ulsan, Republic of Korea B.T. Freemire IIT, Chicago, Illinois, USA V. Samulyak BNL, Upton, Long Island, New York, USA A.V. Tollestrup, K. Yonehara Fermilab, Batavia, Illinois, USA
	Understanding of the interaction of muon beams with plasma in muon cooling devices is important for the optimization of the muon cooling process. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code, is used for the simulation support of the experimental program on the hydrogen gas filled RF cavity in the Mucool Test Area (MTA) at Fermilab. We have investigated the plasma dynamics in the RF cavity including the process of power dump by plasma (plasma loading), recombination of plasma, and plasma interaction with dopant material. By comparison with experiments in the MTA, simulations suggest several unknown properties of plasma such as the effective recombination rate, the electron attachment time on dopant molecule, and the ion - ion recombination rate in the plasma.
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MOPHA003	Status of ATF2 IP-BPM Project	feedback, electronics, operation, status	777
	O.R. Blanco-García, P. Bambade, F. Bogard, P. Cornebise, S. Wallon LAL, Orsay, France D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich JAI, Oxford, United Kingdom P. Burrows, G.B. Christian, C. Perry Oxford University, Physics Department, Oxford, Oxon, United Kingdom Y. Honda, K. Kubo, S. Kuroda, T. Naito, T. Okugi, T.T. Tauchi, N. Terunuma KEK, Ibaraki, Japan S.W. Jang, E.-S. Kim KNU, Deagu, Republic of Korea
	The efforts during the second half of 2014 towards nano-metric beam position measurement and stabilization at the Interaction Point (IP) section of the Accelerator Test Facility (ATF) at KEK are presented. Recent improvements to the beam position monitor (BPM) data analysis and processing electronics, as well as the installation of a new set of C-Band BPMs, are reviewed.
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MOPHA010	RF Feedback and Detuning Studies for the BESSY Variable Pulse Length Storage Ring Higher Harmonic SC Cavities	beam-loading, feedback, synchrotron, operation	798
	A. Neumann, P. Echevarria, P. Goslawski, M. Ries, M. Ruprecht, A.V. Vélez, G. Wüstefeld HZB, Berlin, Germany
	For the feasibility of the BESSY VSR upgrade project of BESSY II two higher harmonic systems at a factor of 3 and 3.5 of the ring's RF fundamental of 500 MHz will be installed in the ring. Operating in continuous wave at high average accelerating field of 20 MV/m and phased at zero-crossing, the superconducting cavities have to be detuned within tight margins to ensure stable operation and low power consumption at a loaded Q of 5·10⁷. The field variation of the cavities is mainly driven by the repetitive transient beam-loading of the envisaged complex bunch fill pattern in the ring. Within this work combined LLRF-cavity and longitudinal beam dynamics simulation will demonstrate the limits for stable operation, especially the coupling between synchrotron oscillation and RF feedback settings. Further impact by beam current decay and top-up injection shots are being simulated. * G. Wüstefeld et al., IPAC 11, San Sebastiàn, Spain, p. 2936.
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MOPHA013	Superconducting Radio Frequency Cavity Degradation Due to Errant Beam	ion, ion-source, linac, vacuum	805
	C.C. Peters, D. Curry, G.D. Johns ORNL RAD, Oak Ridge, Tennessee, USA A.V. Aleksandrov, W. Blokland, M.T. Crofford, C. Deibele, G.W. Dodson, J. Galambos, T.A. Justice, S.-H. Kim, T.A. Pelaia II, M.A. Plum, A.P. Shishlo ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05- 00OR22725 for the U.S. Department of Energy. In 2009, the Superconducting Radio Frequency (SRF) cavities at the Spallation Neutron Source (SNS) began to experience significant operational degradation [1]. The source of the degradation was found to be repeated striking of cavity surfaces with errant beam pulses. The Machine Protection System (MPS) was designed to turn the beam off during a fault condition in less than 20 μseconds [2] as these errant beam pulses were not unexpected. Unfortunately an improperly operating MPS was not turning off the beam within the designed 20 μseconds, and the SRF cavities were being damaged. The MPS issues were corrected, and the SRF performance was restored with cavity thermal cycling and RF processing. However, the SRF cavity performance has continued to degrade, though at a reduced rate compared to 2009. This paper will detail further study of errant beam frequency, amount lost per event, causes, and the corrective actions imposed since the initial event.
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MOPHA019	Implementation of a High Level Phase Controller for the Superconducting Injector of the S-DALINAC	electron, controls, EPICS, injection	814
	T. Bahlo, C. Burandt, F. Hug, N. Pietralla TU Darmstadt, Darmstadt, Germany
	Funding: This work has been supported by the DFG through CRC 634 The Superconducting DArmstadt LINear Accelerator S‑DALINAC is a recirculating electron accelerator with a design energy of 130 MeV. It operates in cw-mode at a radio frequency of 3 GHz and provides either unpolarized or polarized electron beams. Before entering the main accelerator the electron beam passes both, a normal-conducting injector beamline for beam preparation and a superconducting 10 MeV injector beamline for preacceleration. The phase of the beam which is injected into the 40 MeV main accelerator is crucial for the efficiency of the acceleration process and the minimization of the energy spread. Due to thermal drifts of the normal-conducting injector cavities this injection phase varies by about 0.2 degree over a timescale of an hour. In order to compensate these drifts, a high level phase controller has been implemented. It adjusts the phase measured at an rf-monitor at the exit of the superconducting injector by changing the phase of a prebuncher in the normal-conducting injector beamline. We will present the used hardware, the control algorithm as well as measurements showing the phase stabilization achieved by this controller.
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MOPHA021	Bunch-by-Bunch Longitudinal RF Feedback for Beam Stabilization at FAIR	feedback, LLRF, controls, synchrotron	820
	K. Groß, H. Klingbeil TEMF, TU Darmstadt, Darmstadt, Germany U. Hartel, H. Klingbeil, U. Laier, D.E.M. Lens, K.-P. Ningel, S. Schäfer, B. Zipfel GSI, Darmstadt, Germany
	Funding: Work supported by the German Federal Ministry of Education and Research (BMBF) under the project 05P12RDRBF. To damp undesired longitudinal oscillations of bunched beams, the main synchrotron SIS100 of FAIR (Facility for Antiproton and Ion Research) will be equipped with a bunch-by-bunch feedback system. This helps to stabilize the beam, to keep longitudinal emittance blow-up low and to minimize beam losses. The proposed LLRF (low level radio frequency) topology of the closed loop feedback system is described. In some aspects, it is similar to the beam phase control system* developed at GSI Helmholtzzentrum für Schwerionenforschung GmbH. The differences and challenges are pointed out, which are mainly the bunch-by-bunch signal processing followed by the generation of a correction voltage in dedicated feedback cavities. The adapted topology was verified at SIS18 during beam time in 2014 using LLRF prototype subsystems and the two existing ferrite-loaded acceleration cavities. The experimental setup to damp coherent longitudinal dipole oscillations is presented and evaluated with focus on the realized modifications, including ongoing and pending investigations. Finally, the current status of the longitudinal feedback system for FAIR is summarized. * Klingbeil et al., IEEE Trans. Nuc. Sci., Vol. 54, No. 6, 2007.
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MOPHA024	A Novel Transverse Deflecting Cavity for Slice Diagnostics at BERLinPro	polarization, SRF, emittance, low-level-rf	827
	A. Ferrarotto, B. Riemann, T. Weis DELTA, Dortmund, Germany H.-W. Glock, T. Kamps, J. Völker HZB, Berlin, Germany
	Funding: Work supported by BMBF under contract no. 05K10PEA BERLinPro is an energy-recovery linac project to be realized at the Helmholtz-Zentrum Berlin (HZB) for an electron beam with 1mm mrad normalized emittance and 100 mA average current. The initial beam parameters are determined by the performance of the electron source, an SRF photo-electron injector. The development auf this SRF photon-electron injector is a main task of BERLinPro. Especially the beam emittance is basically defined by the SRF photogun. For beam diagnostics time dependent effects from the RF curvature and space charge must be taken into account and a sophisticated slice diagnostics is required. To perform this type of diagnostics a transverse deflecting cavity has been designed, characterized and is presently under construction.. This single cell cavity operates in a TM110-like mode at 1.3 GHz optimized for high transverse shuntimpedance of appr. 3.2 MOhm by a concentration of fields near the beam axis. The cavity has a novel geometry that allows for an operation with both polarizations of the TM110-Mode. The layout of the deflecting cavity will be presented together with the results of the low RF characterization.
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MOPHA028	Operation of Normal Conducting RF Guns with MicroTCA.4	gun, LLRF, feedback, operation	841
	M. Hoffmann, V. Ayvazyan, J. Branlard, L. Butkowski, M.K. Grecki, U. Mavrič, M. Omet, S. Pfeiffer, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany W. Fornal, R. Rybaniec Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland A. Piotrowski FastLogic Sp. z o.o., Łódź, Poland
	During the last half year, the MicroTCA.4 based single cavity LLRF control system was installed and commissioned at several normal conducting facilities at DESY (FLASH RF gun, REGAE, PITZ RF gun, and XFEL RF gun). First tests during the last year show promising results in optimizing the system for high speed digital LLRF feedbacks, i.e. reducing system latency, increasing the internal controller processing speed, testing new control schemes, and optimizing controller parameters. In this contribution we will present results and gained experience from the commissioning phase and the first time period of real operation.
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MOPHA033	Physical Parameter Identification of Cross-Coupled Gun and Buncher Cavity at REGAE	gun, resonance, coupling, higher-order-mode	857
	A.S. Nawaz, H. Werner TUHH, Hamburg, Germany M. Hoffmann, S. Pfeiffer, H. Schlarb DESY, Hamburg, Germany
	A reasonable description of the system dynamics is one of the key elements to achieve high performance control for accelerating modules. This paper depicts the system identification of a cross-coupled pair of cavities for the Relativistic Electron Gun for Atomic Exploration - REGAE. Two normal conducting copper cavities driven by a single RF source accelerate and compress a low charge electron bunch with sub 10 fs length at a repetition rate up to 50 Hz. It is shown how the model parameters of the cavities and the attached radio frequency subsystem are identified from data generated at the REGAE facility.
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MOPHA045	Developments and Performance of the LLRF System of the S-Band FERMI Linac	LLRF, klystron, feedback, controls	891
	A. Fabris, F. Gelmetti, M. Milloch, M. Predonzani Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	The requirements on beam quality on the FERMI Free Electron Laser (FEL) linac impose challenging specifications on the stability of the RF fields that can only be met by using high reliable and high performance state of the art LLRF systems. The system installed in FERMI has met these requirements and is routinely operational for the machine on a 24/7 basis. The completion of the deployment of the LLRF units in 2015 increases the capabilities of the system, adding further measurement channels and monitoring, and allowing new functionalities. This paper provides an overview of the results achieved with the LLRF system of FERMI and an outlook of the further developments that are being implemented or planned.
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MOPHA052	Optimization of ILC Cryomodule Design Using Explosion Welding Technology	cryomodule, niobium, cryogenics, neutron	913
	A. Basti University of Pisa and INFN, Pisa, Italy F. Bedeschi INFN-Pisa, Pisa, Italy Ju. Boudagov, B.M. Sabirov, G. Shirkov, Yu.V. Taran JINR, Dubna, Moscow Region, Russia A. Bryzgalin, L. Dobrushin, S. Illarionov, E. Pekar PWI, Kiev, Ukraine P. Fabbricatore INFN Genova, Genova, Italy
	Optimization of ILC cryomodule design using explosion welding technology. B.Sabirov, J.Budagov, G.Shirkov - JINR, Dubna, Russia A.Basti, F.Bedeschi, P.Fabbricatore - INFN, Pisa/Genova, Italy A.Bryzgalin, L.Dobrushin, S.Illarionov, E.Pekar - EWI, Kiev, Ukraine JINR activity in the ILC Project is the development, in association with INFN, of techniques to simplify and make cheaper the construction of the ILC cryomodules. In the current ILC TDR design both the helium vessel shell and the connected pipes are made of expensive titanium, one of the few metals that can be welded to niobium by the electron beam technique. We describe the construction and performance of transition elements, obtained by explosion welding, that can couple the niobium cavity with a stainless steel helium vessel. Several designs for these transitions have been produced and studied showing varying levels of reliability. Based on this experience a new design, including a minimal titanium intermediate layer, has been built. Preliminary tests yield impressive results, indicating a very strong resistance of the bon
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MOPHA053	Radiation Measurements of a Medical Particle Accelerator Through a Passive Resonant Cavity	linac, detector, coupling, radiation	917
	A. Leggieri, F. Di Paolo, D. Passi Università degli Studi di Roma "Tor Vergata", Roma, Italy A. Ciccotelli, S. De Stefano, G. Felici, F. Marangoni S.I.T., Aprilia, Italy
	Beam monitoring system are required by technical standards for the real time measurement of the dose delivered to the target while the beam is crossing them * . Traditional beam current monitoring systems are based on ionization chambers and requires high voltage biases * **. This study investigates on the measurements of the electron beam current emitted by a medical electron linear accelerator using the power exchange of the beam current with a passive resonant cavity *** placed at the output interface of the accelerator. The cavity is magnetically coupled with a coaxial transmission line loaded on a microwave envelope detector and its output signal has been documented while receiving several electron currents. This paper shows the complete equivalency, in terms of global performance, of the current revelation performed by exploiting the cavity-beam interaction principle with the classical technology, based on ionization chambers, however without need of high voltage. The most important point is that the resonant cavity system, by measuring the beam current, gives a direct measurement of a physical observable quantity directly related with the dose deposed by the beam. * EN 60601-2-1, 2009. A.P. Turner, 1979. * V.L. Uvarov, 1997. ** M. Ruf∗, 2014. *** J.B. Rosenzweig, 2003
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MOPHA056	Status of LLRF Control System for SuperKEKB Commissioning	controls, LLRF, beam-loading, klystron	924
	T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri KEK, Ibaraki, Japan H. Deguchi, K. Hayashi, T. Iwaki, M. Ryoshi Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo, Japan
	Beam commissioning of the SuperKEKB will be started in JFY2015. A new LLRF control system, which is an FPGA-based digital RF feedback control system on the MicroTCA platform, has been developed for high current beam operation of the SuperKEKB. The mass production and installation of the new systems has been completed as scheduled. The new LLRF control systems are applied to nine RF stations (klystron driving units) among existing thirty stations. As a new function, klystron phase lock loop was digitally implemented within the cavity FB control loop in the FPGA, and in the high power test it worked successfully to compensate for the klystron phase change. Beam loading was also simulated in the high power test by using an ARES cavity simulator, and then good performance in the cavity-voltage feedback control and the cavity tuning control was demonstrated to compensate the large beam loading for the SuperKEKB parameters. Fabrication of another new LLRF control system for damping ring which is required for low-emittance positron injection is scheduled in JFY2015.
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MOPTY008	Preliminary Hardware Implementation of Compensation Mechanism of Superconducting Cavity Failure in C-ADS Linac	FPGA, hardware, linac, proton	953
	Z. Xue, J.P. Dai IHEP, Beijing, People's Republic of China L. Cheng, Y. Yang SINANO, Suzhou, People's Republic of China
	For the proton linear accelerators used in applications such as ADS, due to the nature of the operation, it is essential to have beam failures at the rate several orders of magnitude lower than usual performance of similar accelerators. In order to achieve this extremely high performance reliability requirement, in addition to hardware improvement, a failure tolerant design is mandatory. A compensation mechanism to cope with hardware failure, mainly RF failures of superconducting cavities, will be in place in order to maintain the high uptime, short recovery time and extremely low frequency of beam loss. The hardware implementation of the mechanism poses high challenges due to the extremely tight timing constraints, high logic complexity, and mostly important, high flexibility and short turnaround time due to varying operation contexts. We will explore the hardware implementation of the scheme using fast electronic devices and Field Programmable Gate Array (FPGA). In order to achieve the goals of short recovery time and flexibility in compensation algorithms, an advanced hardware design methodology including high-level synthesis will be used.
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MOPTY014	An Experimental Study of Higher-Order Modes Excited by High Repetition Rate Electron Beam in an SRF Cavity	HOM, electron, SRF, experiment	965
	Y. Gao, J.E. Chen, L.W. Feng, J.K. Hao, S. Huang, L. Lin, K.X. Liu, X. Luo, S.W. Quan, F. Wang, Zh.W. Wang PKU, Beijing, People's Republic of China
	Funding: National Natural Science Foundation of China (No. 11275014) Higher-order modes (HOMs) excited by electron beam traversing a superconducting rf (SRF) cavity contain lots of information and can be used for intra-cavity electron beam diagnostics. Unlike single bunch, multiple bunches would excite HOMs with a much complicated spectrum. In this paper, we present our recent research on HOMs excited by a high repetition rate electron beam in an SRF cavity. Especially, we focus on the integer multiple frequency peaks in the HOM spectrum, which are determined by the nearest eigen HOM peaks. The experiments were carried out on the DC-SRF photoinjector, which was operated at MHz repetition rate. The results agree well with theoretic analysis.
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MOPTY016	Study of Diamond Detector Application at the Front End of a High Intensity Hadron Accelerator	detector, radiation, hadron, proton	972
	G. Ren, D.H. He, W. Li, Y. Li USTC/NSRL, Hefei, Anhui, People's Republic of China M. Zeng Tsinghua University, Beijing, People's Republic of China
	Diamond detectors function as beam loss or luminosity monitors for high energy accelerators, such as LHC, Babar, etc. Because of regular detectors‘ insufficient protection of the front end, diamond detectors owning significant characteristics, like time resolution in the nanosecond range, radiation hardness and negligible temperature dependence. Thus, diamond detectors have been becoming promising candidates for detecting BLMs of fully super-conducting hadron accelerator, such as C-ADS, FRIB. In this paper, the sensitivity of diamond detectors was simulated by Monte Carlo program FLUKA and GEAN4. Meanwhile, we tested the performance of a new prototype of CVD diamond detector, and compared it with Si-PIN and Bergoz detectors at the storage ring of the HLS II. The results of the diamond detector were consistent with other two detectors well. More evaluation of diamond detectors in low energy radiation field are ongoing.
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MOPTY025	High-current RFQ Design Study on RAON	rfq, emittance, ion, acceleration	990
	J. Bahng, E.-S. Kim Kyungpook National University, Daegu, Republic of Korea B.H. Choi IBS, Daejeon, Republic of Korea
	Rare isotope Accelerator Of Newness (RAON) heavy ion accelerator has been designed as a facility for a rare isotepe accelerator of the Rare Isotope Science Project (RISP). RAON provides 400 kW CW heavy ion beams from proton to uranium to support researches in various science fields. The RAON system consists of a few ECR ion source, low energy beam transport systems (LEBTs), CW radio frequency quadrupole (RFQ) accelerators, a medium energy beam transport and superconducting linac. We present the design study of the RFQ accelerator from 30 keV/u to 1.5 MeV/u of deuteron beam with meeting a requirement of over 15 mA beam at the target. We optimized the normal conducting CW RFQ accelerator that has a high transmission and a low longitudinal emittance. In this paper, we will present the design result of RFQ beam dynamics studies and its 2D and 3D EM analysis.
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MOPTY038	NSLS-II Digital RF Controller Logic and Applications	EPICS, FPGA, feedback, controls	1010
	B. Holub, F. Gao, J.G. Kulpin, C. Marques, J. Oliva, J. Rose, N.A. Towne BNL, Upton, New York, USA
	The National Synchrotron Light Source II accelerator consists of the Storage Ring, the Booster Ring, and Linac along with their associated cavities. NSLS II is committed to the use of digital RF controllers for controlling these cavities. Given the number, types and variety of functions of these cavities, we sought to limit the logic development effort by reuse of parameterized code on one hardware platform. Currently we have fielded six controllers in the NSLS II system. There are two controllers each in both the Storage ring and Booster. The first controller in each is used to control the cavity field and the second controller used for diagnostics. In the Linac a controller is provided which modulates the eGUN grid to generate the bunches. Lastly, in the Master Oscillator Distribution System a controller is used to make phase corrections to the outgoing master oscillator clock signal to account for thermal phase drifts along the distribution path.
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MOPTY042	ALBA LLRF Upgrades to Improve Beam Availability	LLRF, beam-loading, operation, synchrotron	1022
	A. Salom, B. Bravo, J. Marcos, F. Pérez ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	ALBA is a 3GeV synchrotron light source located in Barcelona and operating with users since May 2012. The RF system of the SR is composed of six cavities, each one powered by combining the power of two 80 kW IOTs through a Cavity Combiner (CaCo). At present, there are several RF interlocks per week. The redundancy given by the six cavities makes possible the survival of the beam after one of these trips. In these cases, the cavity has to be recovered with the circulating beam. An autorecovery process has been implemented in the digital LLRF system in order to recover the faulty RF plant after a trip. But these trips also create perturbations to the beam stability. In order to minimize the beam perturbations induced by these RF interlock, an additional feed-forward loop is being implemented. The functionally, main parameters and test results of these new algorithms will be presented.
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MOPTY052	Experimental and Simulation Studies of Hydrodynamic Tunneling of Ultra-Relativistic Protons	target, simulation, proton, experiment	1048
	F. Burkart, R. Schmidt, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland A.R. Piriz Universidad de Castilla-La Mancha, Ciudad Real, Spain A. Shutov IPCP, Chernogolovka, Moscow region, Russia N.A. Tahir GSI, Darmstadt, Germany
	The expected damage due to the release of the full LHC beam energy at a single aperture bottleneck has been studied. These studies have shown that the range of the 7 TeV LHC proton beam is significantly extended compared to that of a single proton due to hydrodynamic tunneling effect. For instance, it was evaluated that the protons and their showers will penetrate up to a length of 25 m in solid carbon compared to a static range of around 3 m. To check the validity of these simulations, beam- target heating experiments using the 440 GeV proton beam generated by the SPS were performed at the HiRadMat test facility at CERN . Solid copper targets were facially irradiated by the beam and measurements confirmed hydrodynamic tunneling of the protons and their showers. Simulations have been done by running the energy deposition code FLUKA and the 2D hydrodynamic code, BIG2, iteratively. Very good agreement has been found between the simulations and the experimental results * providing confidence in the validity of the studies for the LHC. This paper presents the simulation studies, the results of a benchmarking experiment, and the detailed target investigations. * N.A. Tahir et al., Phys. Rev. Special Topics Accel. Beams 15 (2012) 051003. ** R. Schmidt et al., Phys. Plasmas 21 (2014) 080701.
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MOPTY083	Progress towards Electron-beam Feedback at the Nanometre Level at the Accelerator Test Facility (ATF2) at KEK	feedback, kicker, extraction, electron	1133
	P. Burrows, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, G.B. Christian, M.R. Davis, C. Perry JAI, Oxford, United Kingdom D.R. Bett CERN, Geneva, Switzerland
	Ultra-low latency beam-based digital feedbacks have been developed by the Feedback On Nanosecond Timescales (FONT) Group and tested at the Accelerator Test Facility (ATF2) at KEK in a programme aimed at beam stabilisation at the nanometre level at the ATF2 final focus. Three prototypes were tested: 1) A feedback system based on high-resolution stripline BPMs was used to stabilise the beam orbit in the beamline region c. 50m upstream of the final focus. 2) Information from this system was used in a feed-forward mode to stabilise the beam locally at the final focus. 3) A final-focus local feedback system utilising cavity BPMs was deployed. In all three cases the degree of beam stabilisation was observed in high-precision cavity BPMs at the ATF2 interaction point. Latest results are reported on stabilising the beam position to below 100 nanometres.
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MOPWI021	The LCLS-II LLRF System	controls, LLRF, cryomodule, linac	1195
	C. Hovater, R. Bachimanchi JLab, Newport News, Virginia, USA S. Babel, B. Hong, D. Van Winkle SLAC, Menlo Park, California, USA B.E. Chase, E. Cullerton, P. Varghese Fermilab, Batavia, Illinois, USA L.R. Doolittle, G. Huang, A. Ratti, C. Serrano LBNL, Berkeley, California, USA
	Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515. The SLAC National Accelerator Laboratory is planning an upgrade (LCLS-II) to the Linear Coherent Light Source with a 4 GeV CW superconducting (SCRF) linac. The SCRF linac consists of 35 ILC style cryomodules (eight cavities each) for a total of 280 cavities. Expected cavity gradients are 16 MV/m with a loaded QL of ~ 4x10⁷. The RF system will have 3.8 kW solid state amplifiers driving single cavities. To ensure optimum field stability a single source single cavity control system has been chosen. It consists of a precision four channel cavity receiver and RF stations (Forward, Reflected and Drive signals). In order to regulate the resonant frequency variations of the cavities due to He pressure, the tuning of each cavity is controlled by a Piezo actuator and a slow stepper motor. In addition the system (LLRF-amplifier-cavity) is being modeled and cavity microphonic testing has started. This paper describes the LLRF system under consideration, including recent modeling and cavity tests.
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MOPWI025	Phase and Amplitude Tuning Algorithms for the FRIB Superconducting Cavities	linac, acceleration, simulation, SRF	1207
	Y. Zhang, P. Chu, Z.Q. He FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 FRIB driver linac will deliver all heavy ion beams up to uranium with energy above 200 MeV/u, and maximum beam power on target 400 kW for nuclear physics research. Phase and amplitude tuning of the FRIB superconducting cavities – totally about 330 of them, are important to the linac beam commissioning at low power and normal operation at high power. Because relatively low beam energy and high acceleration gradient, beam velocity changes significantly in the cavity RF gaps and the beam bunch cannot preserve perfectly in the further downstream beam diagnostics systems, beam longitudinal tuning algorithms are studied for different FRIB cavities and at different beam energy, which include the acceleration cavities as well as the re-buncher cavities.
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MOPWI028	Initial Experimental Results of a Machine Learning-Based Temperature Control System for an RF Gun	controls, gun, monitoring, network	1217
	A.L. Edelen, S. Biedron, S.V. Milton CSU, Fort Collins, Colorado, USA B.E. Chase, D.J. Crawford, N. Eddy, D.R. Edstrom, E.R. Harms, J. Ruan, J.K. Santucci, P. Stabile Fermilab, Batavia, Illinois, USA
	Colorado State University (CSU) and Fermi National Accelerator Laboratory (Fermilab) have been developing a control system to regulate the resonant frequency of an RF electron gun. As part of this effort, we present experimental results for a benchmark temperature controller that combines a machine learning-based model and a predictive control algorithm for improved settling time, overshoot, and disturbance rejection relative to conventional techniques. Such improvements have implications for machine up-time and management of reflected power. This work is part of an on-going effort to develop adaptive, machine learning-based tools specifically to address control challenges found in particle accelerator systems.
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MOPWI045	The CEBAF Element Database and Related Operational Software	database, hardware, controls, software	1256
	T. L. Larrieu, M.E. Joyce, M. Keesee, C.J. Slominski, R.J. Slominski, D.L. Turner JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The newly commissioned 12 GeV CEBAF accelerator relies on a flexible, scalable and comprehensive database to define the accelerator. This database delivers the configuration for CEBAF operational tools, including hardware checkout, the downloadable optics model, control screens, and much more. The presentation will describe the flexible design of the CEBAF Element Database (CED), its features and assorted use case examples.
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MOPWI047	Architectural Improvements and New Processing Tools for the Open XAL Online Model	simulation, hardware, software, coupling	1262
	C.K. Allen, T.A. Pelaia II ORNL, Oak Ridge, Tennessee, USA J.M. Freed University of South Carolina, Columbia, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. The Open XAL online model is the component of Open XAL* providing accelerator modeling dynamic synchronization to live hardware. Several significant architectural enhancements and feature additions have been made concerning the handling and processing of simulation data. The major structural change is the creation of a single class Trajectory<> that manages all simulation data. Another significant design change was the development of standard tools for processing simulation results. One may obtain machine parameters such as fixed orbit, phase advance, dispersion, etc., or beam-based calculations such as RMS size and centroid location simply by passing simulation results, i.e. a Trajectory<> object, to these computation tools. Finally, the ability to fully create composite modeling elements was implemented in the online model. Specifically, accelerator hardware can be modeled as a collection of constituent modeling elements. This sub-structure capability is extremely useful for modeling RF cavities consisting of coupled RF gaps coupled and drift spaces. We present an overview of the new architecture and how it is used when building applications. * http://xaldev.sourceforge.net/
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TUAC3	Optimization of Beam Loss Monitor Network for Fault Modes	detector, network, simulation, lattice	1356
	Z. Liu, Z.Q. He, S.M. Lidia, D. Liu, Q. Zhao FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 Beam Loss Monitoring (BLM) System is an essential part to protect accelerator from machine faults. Compared with the empirical or uniform BLM arrangement in most accelerators, our new optimization approach proposes a “minimum spatial distribution” for BLM network. In this distribution, BLMs shall be placed at a small set of “critical positions” that can detect all failure / FPS trigger-able events of each fault mode. In additional, to implement a more advanced function of fault diagnosis, BLM should also be placed at “discrimination points” for fault-induced loss pattern recognition. With examples of FRIB failure event simulations, the author demonstrates the proof of concept to locate these “critical positions” and “discrimination points” for the minimum spatial distribution of BLMs.
	Slides TUAC3 [2.341 MB]
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TUPWA009	50 MeV Electron Linac with a RF Gun and a Thermoionic Cathode	gun, linac, focusing, cathode	1413
	A.S. Setty, A.S. Chauchat, D. Fasse, D. Jousse, P. Sirot Thales Communications & Security (TCS), Gennevilliers Cedex, France
	The low energy part of our pre injectors is made up of a 90 kV DC themoionic trioode gun, followed by a 500 MHz sub harmonic prebuncher and a 3 GHz prebuncher. We propose a new design for a 50 MeV linac with a RF gun . this study will compare the beam dynamics simulations for the new design and for our previous pre injectors. A. Setty et al. "Study of a RF gun with a Thermoionic Cathode", Proceeding IPAC 2014, Germany, Dresden, June 2014.
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TUPWA018	Progress Report of the Berlin Energy Recovery Project BERLinPro	gun, SRF, booster, electron	1438
	M. Abo-Bakr, W. Anders, K.B. Bürkmann-Gehrlein, A. Burrill, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knobloch, J. Kolbe, J. Kühn, O. Kugeler, B.C. Kuske, P. Kuske, A.N. Matveenko, A. Meseck, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, D. Pflückhahn, J. Rahn, J. Rudolph, M. Schmeißer, O. Schüler, J. Völker HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association The Helmholtz Zentrum Berlin is constructing the Energy Recovery Linac Project BERLinPro on its site in Berlin Adlershof. The project is intended to expand the required accelerator physics and technology knowledge mandatory for the design, construction and operation of future synchrotron light sources. The project goal is the generation of a high current (100 mA), high brilliance (norm. emittance below 1 mm mrad) cw electron beamat 2~ps rms bunch duration or below. The planning phase of the project is completed and the design phase of most of the components is finished. Many of them have already been ordered. After some delay the construction of the building has started in February 2015. The status of the various subprojects as well as a summary of current and future activities will be given. Major project milestones and details of the project time line will be finally introduced.
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TUPWA020	BNL ATF II Beamlines Design	experiment, electron, laser, linac	1445
	M.G. Fedurin, Y.C. Jing, D. Stratakis, C. Swinson BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The Brookhaven National Lab. Accelerator Test Facility (BNL ATF) is currently undergoing a major upgrade (ATF-II). Together with a new location and much improved facilities, the ATF will see an upgrade in its major capabilities: electron beam energy and quality and CO2 laser power. The electron beam energy will be increased in stages, first to 100-150 MeV followed by a further increase to 500 MeV. Combined with the planned increase in CO2 laser power (from 1-100 TW), the ATF-II will be a powerful tool for Advanced Accelerator research. A high-brightness electron beam, produced by a photocathode gun, will be accelerated and optionally delivered to multiple beamlines. Besides the energy range (up to a possible 500 MeV in the final stage) the electron beam can be tailored to each experiment with options such as: small transverse beam size (<10 um), flat beam, short bunch length (<100 fs) and, combined short and small bunch options. This report gives a detailed overview of the ATF-II capabilities and beamlines configuration.
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TUPWA023	A Step Closer to the CW High Brilliant Beam with the ELBE SRF-Gun-II	gun, SRF, cathode, electron	1456
	R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany
	In order to achieve the CW electron beam with a high average current up to 1 mA and a very low emittance of 1 μm, an improved superconducting photo-injector (ELBE SRF-Gun-II) has been installed and commissioned at HZDR since 2014. This new gun replaces the first 3.5-cell SRF gun (SRF-Gun-I) at the SC Linac ELBE. The RF performance of the niobium cavity has been evaluated, the beam parameters for low charge bunches have been measured, and the first beam has been guided into the ELBE beam line. The results agree with the simulation very well. The photocathode transfer system has been installed for the first high current beam test planned in 2015. However, the unexpected strong degradation on the cavity and also on the photocathode was found soon after the first photocathode exchange. In this contribution the results of the SRF-Gun-II commissioning and the latest experiment will be presented in detail.
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TUPWA029	ARES: Accelerator Research Experiment at SINBAD	electron, bunching, experiment, linac	1469
	B. Marchetti, R.W. Aßmann, C. Behrens, R. Brinkmann, U. Dorda, K. Flöttmann, J. Grebenyuk, M. Hüning, Y.C. Nie, H. Schlarb, J. Zhu DESY, Hamburg, Germany
	ARES is a planned linear accelerator for R&D for production of ultra-short electron bunches. It will be hosted at the SINBAD facility, at DESY in Hamburg. The goal of ARES is to produce low charge (0.2-50pC), ultra-short (from few fs to sub-fs) bunches, with high arrival time stability (less than 10fs) for various applications, such as external injection for Laser Plasma Wake-Field acceleration. The baseline layout of the accelerator foresees an S-band photo-injector which compresses low charge electron bunches via velocity bunching and accelerates them to 100 MeV energy. In the second stage, it is planned to install a third S-band accelerating cavity to reach 200 MeV as well as two X-band cavities: One for the linearization of the longitudinal phase space (subsequently allowing an improved bunch compression) and another one as a transverse deflecting cavity for longitudinal beam diagnostics. Moreover a magnetic bunch compressor is envisaged allowing to cut out the central slice of the beam** or hybrid bunch compression. * R. Assmann et al., TUPME047, Proceedings of IPAC 2014. R. Assmann, J. Grebenyuk, TUOBB01, Proceedings of IPAC 2014. * P. Emma et al., PRL 92 7 (2004).
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TUPWA058	Study of a C-band Harmonic RF System to Optimize the RF Bunch Compression Process of the SPARC Beam	gun, linac, experiment, emittance	1552
	A. Gallo, D. Alesini, M. Bellaveglia, M. Ferrario INFN/LNF, Frascati (Roma), Italy A. Bacci, V. Petrillo, A.R. Rossi, L. Serafini Istituto Nazionale di Fisica Nucleare, Milano, Italy F. Cardelli, L. Piersanti INFN-Roma1, Rome, Italy B. Marchetti DESY, Hamburg, Germany M. Rossetti Conti Universita' degli Studi di Milano & INFN, Milano, Italy
	The SPARC linac at the INFN Frascati Labs is a high brilliance electron source with a wide scientific program including production of THz and Thomson backscattering radiation, FEL studies and plasma wave acceleration experiments. The linac is based on S-band RF and consists in an RF Gun followed by 3 accelerating structures, while an energy upgrade based on 2 C-band accelerating structures is ready to be implemented. Short bunches are ordinarily produced by using the linear RF bunch compression concept. A harmonic RF structure interposed between the Gun and the 1st accelerating structure can be used to optimize the RF compression by a longitudinal phase space pre-correction, allowing to reach shorter bunches, a much more uniform current distribution and in general to control better the whole compression process. Here we report the results of numerical studies on the SPARC bunch compression optimization through the use of a harmonic cavity, and the design of a C-band RF system to implement it. The proposed system consists in a multi-cell SW cavity powered by a moderate portion of the total RF power spilled from the C-band power plant already installed for the linac energy upgrade.
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TUPWA063	FEL Enhancement by Microbuch Structure Made with Phase-Space Rotation	FEL, laser, simulation, bunching	1570
	M. Kuriki, Y. Seimiya HU/AdSM, Higashi-Hiroshima, Japan S. Chen, K. Ohmi, J. Urakawa KEK, Ibaraki, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan R. Kato ISIR, Osaka, Japan
	Funding: This work is partly supported by MEXT/JSPS KAKENHI (Grant-in-Aid for scientic research) 25390126, Japan. FEL is one of the ideal radiation source over the wide range of wavelength region with a high brightness and a high coherence. Many methods to improve FEL gain has been proposed by introducing an active modulation on the bunch charge distribution. The transverse-longitudinal phase-space rotation is one of the promising method to realize the density modulation as the micro-bunch structure. Initially, a beam density modulation in the transverse direction made by a mechanical slit, is properly transformed into the density modulation in the longitudinal direction by the phase-space rotation. The micro-bunch structure made with this method has a large tunability by changing the slit geometry, the beam line design, and the beam dynamics tuning. For FEL, enegy chirp made by the emittance exchange and chromaticity made by this chirp should be properly corrected. Simulation results and possible applications are discussed.
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TUPWA065	Generation of Multi-bunch Beam with Beam Loading Compensation by Using RF Amplitude Modulation in Laser Undulator Compact X-ray (LUCX)	electron, laser, gun, booster	1576
	M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan K. Sakaue, M. Washio RISE, Tokyo, Japan
	We have developed a compact X-ray source based on inverse Compton scattering between an electron beam and a laser pulse stacked in an optical cavity at Laser Undulator Compact X-ray (LUCX) accelerator in KEK. The accelerator consists of a 3.6 cell photo-cathode rf-gun, a 12cell standing wave accelerating structure and a 4-mirror planar optical cavity. Our aim is to obtain a clear X-ray image in a shorter period of times and the target flux of X-ray is 1.7x10⁷ photons/pulse with 10% bandwidth at present. To achieve this target, it is necessary to increase the intensity of an electron beam to 500nC/pulse with 1000 bunches at 30 MeV. Presently, we have achieved the generation of 24MeV beam with total charge of 600nC in 1000bunches with beam-loading compensation by using the delta T method and the amplitude modulation of RF pulse. The bunch-by-bunch energy difference is within 1.3% peak to peak. We will report the results of the multi-bunch beam generation and acceleration in this accelerator. This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
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TUPWA066	Development of a High Average Power Laser for High Brightness X-ray Source and Imaging at cERL	laser, electron, detector, photon	1579
	A. Kosuge, T. Akagi, S. Araki, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan R. Hajima, M. Mori, T. Shizuma JAEA, Ibaraki-ken, Japan R. Nagai JAEA/ERL, Ibaraki, Japan
	Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan. High brightness X-rays via laser-Compton scattering (LCS) of laser photons stored in an optical cavity by a relativistic electron beam is useful for many scientific and industrial applications such as X-ray imaging. The construction of compact Energy Recovery Linac (cERL) is now in progress at KEK to generate low-emittance and high-current electron beams. In order to demonstrate the generation of high brightness LCS X-rays, it is necessary to develop a high average power injection laser and an optical four-mirror ring cavity with two concave mirrors which is used to produce a small spot laser beam inside the cavity. In this presentation, we will show the result of the development of the high average laser system, the LCS X-rays generation, and the X-ray imaging.
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TUPWA068	Simulation Study of Beam Halo and Loss for KEK Compact ERL	simulation, laser, gun, electron	1587
	O. Tanaka, T. Miyajima, N. Nakamura, S. Sakanaka, M. Shimada KEK, Ibaraki, Japan
	At the KEK Compact ERL (cERL) designed to operate at high-brilliance and high-current electron beams, the maximum averaged current was recorded at 6.5 muA for the beam energy of 20 MeV on March 2014 and should be increased up to 10 mA in a step-by-step manner in a few years. In order to increase the beam current by reducing the beam loss, we need to know the mechanism of the beam loss. For this purpose we investigate beam halo originated from characteristics and imperfections of an electron gun system, using the tracking code GPT (General Particle Tracer). The beam halo can be lost by the beam-pipe apertures and the collimators in the cERL beam line. In this paper, we will present the simulation results including the beam halo formation and the beam loss distribution along the beam line.
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TUPJE002	Demonstration of High-flux Photon Generation from an ERL-based Laser Compton Photon Source	laser, photon, electron, linac	1607
	R. Nagai, R. Hajima, M. Mori, T. Shizuma JAEA, Ibaraki-ken, Japan T. Akagi, S. Araki, Y. Honda, A. Kosuge, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	A high-flux photon source from the laser Compton scattering (LCS) by an electron beam in an energy-recovery linac (ERL) is a key technology for a nondestructive assay system to identify nuclear materials. In order to demonstrate accelerator and laser technologies required for a LCS photon generation, a LCS photon source is under construction at the Compact ERL (cERL). The LCS photon source consists of a mode-locked fiber laser and a laser enhancement cavity. Flux monitors and a data aqcuisition system are also under construction. The commissioning of the LCS photon source will be started in February 2015 and LCS photon generation is scheduled in March 2015. The demonstration result of the LCS photon source will be presented in detail.
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TUPJE003	Quasi-Traveling Wave RF Gun and Beam Commissioning for SuperKEKB	gun, laser, cathode, emittance	1610
	T. Natsui The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan Y. Ogawa, M. Yoshida, X. Zhou KEK, Ibaraki, Japan
	We are developing a new RF gun for SuperKEKB. High charge low emittance electron and positron beams are required for SuperKEKB. We will generate 7.0 GeV electron beam at 5 nC 20 mm-mrad by J-linac. In this linac, a photo cathode S-band RF gun will be used as the electron beam source. For this reason, we are developing an advanced RF gun which has two side coupled standing wave field. We call it quasi-traveling wave side couple RF gun. This gun has a strong focusing field at the cathode and the acceleration field distribution also has a focusing effect. This RF gun has been installed in the KEK J-linac. Beam commissioning with the RF gun is in progress.
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TUPJE009	Study on Frequency Multiplier of a Pulsed Laser Repetition using an Optical Cavity	laser, gun, electron, cathode	1629
	T. Kobayashi Waseda University, Tokyo, Japan
	We have been studying a compact electron accelerator based on an S-band Cs-Te photo-cathode rf gun at Waseda University. The system is using S-band rf of 2856MHz. When a repetition of the electron bunch is integral multiple of rf, it enables a lot of electron bunch acceleration for the rf gun. The repetition of the electron bunch generated by a photo-cathode rf gun depends on the oscillating frequency of the pulsed mode-locked laser. We have been developing a mode-locked Yb-doped fiber laser based on Non-Linear Polarization Rotation (NLPR). However, its repetition is limited by the fiber length to produce NLPR. Therefore, we have started to develop the external optical cavity which is multiplier of a pulsed laser repetition. It would enable the rf gun to generate high-dose electron beam in a very short time. In this conference, we will report design of the external optical cavity to multiply the pulsed laser repetition, the experimental results of the frequency multiplying of a mode-locked Yb-doped fiber laser, and the future prospects. Work supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
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TUPJE011	Laser-Compton Scattering X-ray Source Based on Normal Conducting Linac and Optical Enhancement Cavity	laser, electron, linac, photon	1635
	K. Sakaue, M. Washio Waseda University, Tokyo, Japan S. Araki, M.K. Fukuda, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	Funding: Work supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We have been developing a compact X-ray source via laser-Compton scattering (LCS) at KEK-LUCX (Laser Undulator Compact X-ray source) facility. The LUCX system is based on S-band normal conducting linac with an energy of 30 MeV and optical enhancement cavity for photon target. As a photon target, we invented a burst mode laser pulse storage technique for a normal conducting linac, which enables to store the high power laser pulses at the timing of electron bunchs. The peak storage power exceeds to more than 250 kW with 357 MHz repetition. Electron linac is under operation with multi-bunch mode, 1000 bunches/train with 600 pC charge in each bunches. We have succeeded to produce 1000 pulse/train LCS X-ray train. Combining high repetition rate electron linac and burst mode optical enhancement cavity, more than 10⁹ ph./sec/10%b.w. flux would be possible. In this conference, the introduction of our test facility LUCX, recent expermental results, and future prospective including normal conducting LCS X-ray source will be presented.
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TUPJE023	Consideration on the Future Major Upgrades of the SSRF Storage Ring	storage-ring, injection, emittance, optics	1672
	Z.T. Zhao, B.C. Jiang, Y.B. Leng, S.Q. Tian, L. Yin, M.Z. Zhang SINAP, Shanghai, People's Republic of China
	The SSRF storage ring was in operation from 2008, currently it is operating at the energy of 3.5GeV, the natural emittance of 3.9 nm-rad and the beam current of 240 mA, serving for 13 beamlines with 9 IDs. There will be around 40 operated beamlines around 2020, which need some upgrade of the storage ring existing performance, such as the new lattice with superbends. And looking for the future beyond, the major upgrade towards a diffraction limited storage ring is under consideration. This paper presents the initial investigation and the proposal on the ultimate storage ring upgrade for SSRF.
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TUPJE056	VELA Machine Development and Beam Characterisation	cathode, electron, gun, klystron	1752
	D.J. Scott, D. Angal-Kalinin, A.D. Brynes, F. Jackson, J.K. Jones, A. Kalinin, S.L. Mathisen, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, L.K. Rudge, E. Sneddon, M. Surman, R. Valizadeh, A.E. Wheelhouse, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S.D. Barrett, C.P. Topping, A. Wolski The University of Liverpool, Liverpool, United Kingdom A. Lyapin JAI, Egham, Surrey, United Kingdom M.D. Roper STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom C.P. Topping, A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom E. Yamakawa Royal Holloway, University of London, Surrey, United Kingdom
	Recent developments on the VELA (Versatile Electron Linear Accelerator) RF photo-injector at Daresbury Laboratory are presented. These are three-fold; commissioning/installation, characterising and providing beam to users. Measurements for characterising the dark current (DC), 4-D transverse emittance, lattice functions and photoinjector stability are presented. User beam set ups to provide beam for electron diffraction and Cavity Beam Position Monitor development are summarised.
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TUPJE058	Preparation of Polycrystalline and Thin Film Metal Photocathodes for Normal Conducting RF Guns	cathode, gun, electron, experiment	1759
	S. Mistry, M.D. Cropper Loughborough University, Leicestershre, United Kingdom A.N. Hannah, K.J. Middleman, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	A comparison of quantum efficiency (QE) and work function (wf) measurements of polycrystalline and thin film metal photocathodes for use in NCRF guns, similar to the S-band gun under development for CLARA project at Daresbury, are reported. Cu and Nb thin films were grown onto a Si substrate by magnetron sputtering and subsequently were prepared by annealing and Ar ion sputtering. To determine the surface chemistry, x-ray photoelectron spectroscopy was employed. QE measurements were enabled using a UV laser source giving 266 nm light. Wf measurements were carried out using a kelvin probe and ultraviolet photoelectron spectroscopy. Annealing the Cu thin film to 250°C yielded a QE of 1.2E-4; one order of magnitude higher than the QE for sputter cleaned and post annealed polycrystalline Cu. The optimum QE measurement for Nb thin film was 2.6·10^-4, which was found to be comparable to the results obtained for cleaned bulk Nb. Analysis of XPS data of these metals suggest surface composition and surface chemistry are main contributing factors to the QE and WF.
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TUPJE060	Development of Advanced Fourth Generation Light Sources for the Accelerator Science Laboratory	radiation, electron, simulation, laser	1765
	T. Chanwattana, R. Bartolini, A. Seryi JAI, Oxford, United Kingdom R. Bartolini DLS, Oxfordshire, United Kingdom E. Tsesmelis CERN, Geneva, Switzerland
	The John Adams Institute for Accelerator Science (JAI) has proposed the realisation of the Accelerator Science Laboratory (ASL) at the University of Oxford as a facility for the development of advanced compact light sources enabling accelerator science research and applications. The installation of a compact light source in the ASL is planned with two options for the accelerating technologies. Firstly, a conventional RF based accelerator is considered to be a driver for a short pulse THz coherent synchrotron radiation (CSR). The other option focusses on the radiation produced by a Laser Plasma Accelerator (LPA) advanced accelerator technique that will provide the possibility to shorten the length of the beamline. This paper presents results of the studies on beam dynamics for both options of compact light sources in the ASL.
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TUPJE076	Design Study of the Higher Harmonic Cavity for Advanced Photon Source Upgrade	operation, impedance, simulation, superconducting-cavity	1819

Paper

Title

Other Keywords

Page

MOXGB2

Commissioning and Operation of 12 GeV CEBAF

linac, operation, cryomodule, SRF

1

A. Freyberger
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The Continuous Electron Beam Accelerator Facility (CEBAF) located at the Thomas Jefferson National Accelerator Laboratory (JLab) has been recently upgraded to deliver continuous electron beams to the experimental users at a maximum energy of 12 GeV, three times the original design energy of 4 GeV. This paper will present an overview of the upgrade, referred to as the 12GeV upgrade, and highlights from recent beam commissioning results.

Slides MOXGB2 [4.359 MB]

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MOBB2

Fabrication of TESLA-shape 9-cell Cavities at KEK for Studies on Mass-Production in Collaboration with Industries

SRF, cryomodule, status, controls

31

T. Saeki, H. Hayano
KEK, Ibaraki, Japan

The construction of the new Center-of-Innovation (COI) buiding started at KEK from 2014 for the studies of mass-production of Superconducting-RF accelerators in collaboration with industries. The COI buiding is sitting next to the existing KEK-STF building and will include various Superconducting-RF facilities like clean-room for cavity-string assembly, cryomodule-assembly facility, cryogenic system, vertical-test facility, cryomodule-test facility, input-coupler processing facility, cavity Electro-Polishing (EP) facility, and control-room/office-rooms in the dimension of 80 m x 30 m. The purpose of this new SRF facilities is to establish a close collaboration between SRF researchers and industries in order to prepare for the upcoming large-scale future SRF project, like ILC. This article reports the fabricaion of four TESLA-shape 9-cell cavities for the commisioning of these new facilities. Details of the fabrication of these four cavities will be presented.

Slides MOBB2 [3.983 MB]

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MOAD1

Development of High Gradient RF System for J-PARC Upgrade

impedance, operation, proton, acceleration

50

C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii
KEK, Ibaraki, Japan
M. Nomura, T. Shimada, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan
A. Schnase
GSI, Darmstadt, Germany

A new 5-cell cavity has been developed for the upgrade of the J-PARC Main Ring. In the cavity, high impedance magnetic alloy - Finemet FT3L, cores are loaded. The cavity was installed and has been used for the 250 kW beam operation. The cavity is operated with the RF voltage of 70 kV which is two times higher voltage than the present cavities. Eight more cavities will be assembled and installed in the next two years to increase the repetition rate of the Main Ring. This paper describes status of cavity operation under the beam loading and status of the mass productions of the cavities.

Slides MOAD1 [2.551 MB]

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MOAD2

RF Breakdown of 805 MHz Cavities in Strong Magnetic Fields

Windows, operation, controls, klystron

53

D.L. Bowring, A.V. Kochemirovskiy, M.A. Leonova, A. Moretti, M.A. Palmer, D.W. Peterson, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
A.A. Haase
SLAC, Menlo Park, California, USA
P.G. Lane, Y. Torun
Illinois Institute of Technology, Chicago, Illinois, USA
D. Stratakis
BNL, Upton, Long Island, New York, USA

Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. We have measured the breakdown rate in several RF cavities operating at several frequencies. Cavities operating within solenoidal magnetic fields B > 0.25 T show an increased RF breakdown rate at lower gradients compared with similar operation when B = 0 T. Ultimately, this breakdown behavior limits the maximum safe operating gradient of the cavity. Beyond ionization cooling, this issue affects the design of photoinjectors and klystrons, among other applications. We have built an 805 MHz pillbox-type RF cavity to serve as an experimental testbed for this phenomenon. This cavity is designed to study the problem of RF breakdown in strong magnetic fields using various cavity materials and surface treatments, and with precise control over sources of systematic error. We present results from tests in which the cavity was run with all copper surfaces in a variety of magnetic fields.

Slides MOAD2 [10.792 MB]

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MOBD2

Design and Prototyping of HL-LHC Double Quarter Wave Crab Cavities for SPS Test

luminosity, proton, simulation, HOM

64

S. Verdú-Andrés, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA
L. Alberty, K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, N. Kuder, R. Leuxe, C. Zanoni
CERN, Geneva, Switzerland
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
Z. Li
SLAC, Menlo Park, California, USA
A. Ratti
LBNL, Berkeley, California, USA

Funding: Work supported by US DOE via US LARP program, through BSA LLC contract No.DE-AC02-98CH10886 and by EU FP7 HiLumi LHC grant No.284404. Used NERSC resources by US DOE contract No.DE-AC02-05CH11231.
The LHC high luminosity project envisages the use of the crabbing technique for increasing and levelling the LHC luminosity. Double-Quarter Wave (DQW) resonators are compact cavities especially designed to meet the technical and performance requirements for LHC beam crabbing. A couple of DQW crab cavities are under preparation and will be tested with beam in the Super Proton Synchrotron (SPS) of CERN by 2017. This paper describes the design and prototyping of DQW crab cavities for the SPS test.

Slides MOBD2 [6.909 MB]

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MOBD3

Development of a 9 MHz 15 kW Solid-state CW Amplifier for RHIC

impedance, network, resonance, feedback

67

S.C. Dillon
Tomco Technologies, Stepney, South Australia, Australia

This paper describes the technical details of the development of a high-power solid-state amplifier for Brookhaven Laboratory. The amplifier must withstand short duration events of 100% full-power reflection, and also must guarantee delivery of continuous power into any load impedance at any angle.

Slides MOBD3 [10.800 MB]

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MOPWA008

Status of TraceWin Code

simulation, linac, space-charge, diagnostics

92

D. Uriot, N. Pichoff
CEA/DSM/IRFU, France

Well known in the community of high-intensity linear accelerators, the transport code TraceWin * is able to simulate a beam from the source to the target using either simple linear model or multiparticle simulations including 2D or 3D space-charge. Continuously developed at CEA Saclay since 15 years, it is today the reference code for projects such IFMIF, ESS, MYRRHA, SPIRAL2, IPHI … The accuracy of his predictions associated with an original and powerful GUI and its numerous features have made its success, with a community of 200 users worldwide. It is now used on a larger perimeter that its initial skills. The aim of this paper is to summarize the TraceWin capabilities, including implemented last ones.
* http://irfu.cea.fr/Sacm/logiciels/

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MOPWA022

Influence of Transient Beam Loading on the Longitudinal Beam Dynamics at BESSY VSR

beam-loading, synchrotron, damping, simulation

141

M. Ruprecht, P. Goslawski, A. Jankowiak, A. Neumann, M. Ries, G. Wüstefeld
HZB, Berlin, Germany
T. Weis
DELTA, Dortmund, Germany

BESSY VSR, a scheme where 1.7 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring has recently been proposed *. The strong longitudinal bunch focusing is achieved by superconducting high gradient RF cavities. If the bunch fill pattern exhibits a significant inhomogeneity, e.g. due to gaps, transient beam loading causes a distortion of the longitudinal phase space which is different for each bunch. The result are variations along the fill pattern in synchronous phase, synchrotron frequency and bunch shape. This paper presents investigations of transient beam loading and depicts the consequences on bunch length, phase stability and longitudinal multi-bunch oscillations for the projected setup of BESSY VSR.
* G. Wüstefeld, A. Jankowiak, J. Knobloch, M. Ries, Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proceedings of IPAC2011, San Sebastián, Spain

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MOPWA027

Generic Settings Generation for FAIR: First Experience at SIS18

resonance, framework, controls, operation

156

D. Ondreka, J. Fitzek, H. Liebermann, R. Müller
GSI, Darmstadt, Germany

The accelerators of the FAIR facility will be operated using a new control system presently under design at GSI. One of its major components, the module for settings generation and management, is based on the framework LSA developed at CERN. Its task is the provision and administration of set values for all devices in the FAIR facility. The set values for any accelerator are derived from a machine model, implemented by accelerator physicists using the features of the LSA framework. In view of the large number of accelerators in the FAIR facility, the aim is to develop a generic model, applicable to any of those machines. This requires the introduction of an additional logical layer on top of the LSA framework, ensuring the coherence of the modeling strategy across all accelerators. Following this design concept, a prototype of the FAIR settings management system has been realized at GSI, providing support for a large number of operation modes relevant for the later operation of FAIR. The prototype has been used extensively during recent machine experiments with the synchrotron SIS18, performed both to benchmark the machine model and to support further machine developments for FAIR.

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MOPWA031

A New Approach for Resistive Wakefield Calculations in Time Domain

wakefield, impedance, simulation, controls

168

A.V. Tsakanian, H. De Gersem, E. Gjonaj, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany
M. Dohlus, I. Zagorodnov
DESY, Hamburg, Germany

We report on a new numerical technique for the computation of the wakefields excited by ultra-short bunches in the structures with walls of finite conductivity. The developed 3D numerical method is fully time domain. It is based on special Staggered Finite Volume Time Domain (SFVTD) method and has no numerical dispersion in all three axial directions simultaneously. This results in large saving in computational time as well as improved accuracy. The resistive boundary model applies Surface Impedance Boundary Condition (SIBC) evaluation in time domain and covers boundary effects like frequency dependent conductivity, surface roughness and metal oxidation. A good agreement between numerical simulation and perturbation theory is obtained. In addition the new method allows implementation of moving mesh approach that considerably reduces requirements on computational resources. The developed method is especially effective for short range resistive wakefield calculations excited by ultra-short bunches used in FEL based LINACs.

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MOPWA032

Aspects of SRF Cavity Optimization for BESSY-VSR Upgrade

HOM, SRF, higher-order-mode, storage-ring

171

T. Galek, K. Brackebusch, T. Flisgen, J. Heller, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
B.D. Isbarn, B. Riemann, M. Sommer, T. Weis
DELTA, Dortmund, Germany

Funding: Work supported by Federal Ministry for Research and Education BMBF under contract 05K13HR1.
In this work we present a preliminary study of a long chain of cavities and some aspects involved in the optimization procedure. It is important to numerically model and optimize the SRF cavities with respect to external quality factors of the most dangerous higher order modes. BESSY-VSR is an upgrade scheme for the existing BESSY II storage ring aiming to simultaneously support variable electron pulse lengths. Currently, BESSY II supports long 15 ps bunches in the standard user optics configuration and short 1.5 ps bunches in a so-called low-α optics mode. In order to develop BESSY II into a variable electron pulse length storage ring, additional two sets of SRF higher-harmonic cavities will be installed. The present RF acceleration system operates at 0.5 GHz and the additional 3rd harmonic and 3rd sub-harmonic cavities will operate at 1.5 GHz and 1.75 GHz, respectively. These cavities are essential to produce short 1.5 ps bunches with a design current of up to 0.8 mA per bunch. The total current in the storage ring is limited by the higher order mode damping capabilities of the SRF cavities.

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MOPWA033

Yacs - A New 2.5D FEM Eigenmode Solver for Axisymmetric RF-Structures

multipole, dipole, quadrupole, software

175

B.D. Isbarn, B. Riemann, M. Sommer, T. Weis
DELTA, Dortmund, Germany

Funding: Work supported by the BMBF under contract no. 05K13PEB
Most feasibility studies for modern accelerator concepts, including superconducting multicell RF-cavity-resonators in circular accelerators, depend on computing a large number of eigenmode frequencies and field patterns to obtain typical figures of merit. This task includes computational intensive numerical studies. To obtain the full eigenfrequency spectra most of these studies are performed in 3D, require a great amount of computation resources and thus are limited to a few hundred or thousand eigenmodes. To overcome this issue, some codes make use of the axisymmetric geometry of most of the RF-cavity-resonator structures and solve the problem in 2D. Solving in 2D however reduces the eigenmode spectra to eigenmodes with no azimuthal dependencies (so called monopole-modes). Due to the lack of freely available and easy to use 2.5D eigenmode solvers which are able to solve for the full 3D field in a reduced 2.5 dimensional problem, we developed yet another cavity solver (Yacs), a simple FEM based solver capable of solving for the full 3D eigenmodes of axisymmetric problems while only requiring a fraction of the computation resources required by most modern 3D codes.

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MOPWA037

Mirror Symmetric Chicane-Type Emittance Exchange Beamline with Two Deflecting Cavities

quadrupole, emittance, focusing, dipole

190

V. Balandin, W. Decking, N. Golubeva
DESY, Hamburg, Germany

Among optical systems for transverse-to-longitudinal emittance exchange (EEX) chicane-type beamlines are of keen interest, because they do not alter the beam propagation direction. Several designs of such beamlines involving a single dipole-mode cavity (TDC) are known. In this paper we present a chicane-type EEX beamline utilizing two TDCs instead of one. The advantages of this beamline are that it is mirror symmetric and does not require an additional accelerating mode cavity for compensation of the so-called thick-lens effect, and, in the compact design, it allows better control of the beam focusing in the non-bending plane than known beamlines with one TDC.

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MOPWA040

Virtual Cavity Probe Generation using Calibrated Forward and Reflected Signals

coupling, controls, flattop, laser

200

S. Pfeiffer, V. Ayvazyan, J. Branlard, L. Butkowski, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
R. Rybaniec
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

The European X-ray free electron laser requires a high-precision control of accelerating fields to ensure a stable photon generation. Its low level radio frequency system, based on the MicroTCA.4 standard, detects the probe, forward and reflected signals for each cavity. While the probe signal is used to control the accelerating fields, a combination of the forward and reflected signals can be used to compute a virtual probe, whose accuracy is comparable to the directly sampled probe. This requires the removal of cross-coupling effects between the forward and reflected signals. This paper presents the precise generation of a virtual probe using an extended method of least squares. The virtual probe can then be used for precise field control in case the probe signal is missing or corrupted. It can also be used to detect any deviation from the nominal probe profile.

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MOPWA056

Transverse Multi-Pass Beam Breakup Simulation for KEK ERL Light Source

HOM, simulation, linac, cryomodule

248

S. Chen, N. Nakamura, M. Shimada, D. Zhou
KEK, Ibaraki, Japan
S. Huang, K.X. Liu
PKU, Beijing, People's Republic of China

In this paper, the multi-pass BBU of such a high energy ERL is studied based on the simulation on a 3 GeV ERL light source proposed by KEK.

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MOPWA058

Measurement Results of the Impedance of the RF-cavity at the RCS in J-PARC

impedance, injection, kicker, proton

255

Y. Shobuda, H. Harada, H. Hotchi
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The kicker impedance dominates at the RCS in J-PARC. Recently, we observe beam instabilities, which are not explained by the kicker. As a candidate causing the beam instability, the impedance of the RF-cavity is measured. The longitudinal impedance is measured by stretching a single-wire inside the cavity. On the other hand, the measurement of the transverse impedance is done by horizontally shifting the single-wire, due to the accuracy problem. The measured impedance is too low to explain the beam instability.

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MOPWA072

Emittance Exchange Beam Line Design In THU Accelerator Lab

emittance, quadrupole, simulation, electron

285

Q. Gao, H.B. Chen, Y.-C. Du, W.-H. Huang, J. Shi
TUB, Beijing, People's Republic of China
W. Gai
ANL, Argonne, Illinois, USA

Funding: National Natural Science Foundation of China
Emittance exchange (EEX) provides a novel tool to enhance the phase space manipulation techniques. Based on Tsinghua Thomson scattering experimental platform, this study presented a beam line design for exchanging the transverse and longitudinal emittance of an electron bunch. This beam line consists of a 2.856 GHz half-one-half cell deflecting cavity with no axis offset and two doglegs. In this paper, by optimizing the beam envelope parameter for Tsinghua Thomson scattering source, we report the theoretical analysis and a good particle tracking simulation result about emittance exchange and longitudinal shaping.

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MOPJE019

Categorization and Estimation of Possible Deformation in Emittance Exchange based Current Profile Shaping

emittance, wakefield, acceleration, collective-effects

317

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
W. Gai, G. Ha, K.-J. Kim, J.G. Power
ANL, Argonne, Illinois, USA

Funding: This work is partly supported by POSTECH BK²¹⁺ program and Argonne National Laboratory
Shaping the current profile is one of the important issues in collinear wakefield acceleration. In the emittance exchange based shaping technique, the shaped current profile seriously depends on the incoming beam and beam line parameters. To design the beam and beam line properly, it is important to estimate the deformation in the shaped current profile. There are several different deformation types whose level depend on deformation parameter. We categorize the possible deformation types and observe the deformation patterns of the current profile depending on its type and the deformation parameter.

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MOPJE020

High Resolution Longitudinal Property Measurement using Emittance Exchange Beam Line

emittance, quadrupole, space-charge, collective-effects

320

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
W. Gai, G. Ha, K.-J. Kim, J.G. Power
ANL, Argonne, Illinois, USA

Most of longitudinal measurement techniques introduce the transverse-longitudinal correlation because it is very hard to measure the longitudinal properties directly. This correlation is necessary to observe the longitudinal property through the transverse screen, but initial transverse components of the beam restrict the measurement. It is possible to overcome this intrinsic limit using emittance exchange beam line which makes transverse properties at the downstream only depend on longitudinal properties at the upstream. We present the new idea to measure the longitudinal properties using the emittance exchange beam line and preliminary simulation results.

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MOPJE031

Field Map Model for the ESS Linac Simulator

linac, proton, framework, space-charge

348

E. Laface
ESS, Lund, Sweden
I. List
Cosylab, Ljubljana, Slovenia

The proton beam driving the spallation process at the European Spallation Source, in Lund, will be accelerated and delivered onto a tungsten target by a linac. This linac is composed of four different families of accelerating structures: adrift tube linac, a section of spoke resonators and two sections of elliptical cavities for the particles’ medium and high relativistic β. These structures provide 99.8% of the total energy gained by the beam along the accelerator. It is necessary, then, to have an accurate model describing the physics of the cavities in the ESS Linac Simulator (ELS), which isthe online model that will simulate the accelerator during operation. Here, we present an RF-cavity model based on the field maps that we implemented in ELS, showing a maximum 10% deviation from TraceWin in the horizontal, vertical and longitudinal planes.

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MOPJE037

Study and Comparison of Mode Damping Strategies for the UA9 Cherenkov Detector Tank

damping, vacuum, detector, resonance

366

A. Danisi, F. Caspers, R. Losito, A. Masi, B. Salvant, C. Vollinger
CERN, Geneva, Switzerland
T. Demma, P. Lepercq
LAL, Orsay, France

In the framework of the UA9 experiment, the Cherenkov detector is useful to measure the amount of particles deflected by a bent crystal, proving the crystal collimation principle. The tank used to host this device is taken as a case study for an in-depth analysis of different damping strategies for electromagnetic modes which otherwise would give rise to important beam-coupling impedance contributions. Such strategies involve the use of ferrite, damping resistors and a mode-coupler, a solution which intercepts the modes inside the cavity but damps the related power outside the vacuum tank (potentially avoiding heating). Such solutions are discussed through experimental measurements and the relative quality factor is taken as a figure of merit.

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MOPJE053

NSLS-II Beam Lifetime Measurements and Modeling

scattering, emittance, coupling, lattice

416

B. Podobedov, W.X. Cheng, Y. Hidaka, H.-C. Hseuh, G.M. Wang
BNL, Upton, Long Island, New York, USA

NSLS-II is a recently constructed 3 GeV synchrotron light source with design horizontal emittance values in sub-nm range. Achieving good beam lifetime is critically important for NSLS-II as it is closely tied in to such important operational aspects as top-off injection frequency, injector components wear, radiation protection and control, and others. In this paper we present lifetime-related commissioning results, describe our present understanding of beam lifetime at NSLS-II and extrapolate our models to the fully built-up machine operating at 500 mA design beam current.

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MOPJE059

Tests of Wakefield-Free Steering at ATF2

wakefield, emittance, extraction, alignment

438

A. Latina, J. Pfingstner, D. Schulte
CERN, Geneva, Switzerland
E. Adli
University of Oslo, Oslo, Norway
N. Fuster-Martínez
IFIC, Valencia, Spain
J. Snuverink
JAI, Egham, Surrey, United Kingdom

Charge-dependent effects on the orbit and on the beam size affect the performance of the Accelerator Test Facility (ATF2) in a non-negligible way. Until now small beam sizes have only been achieved running with a beam charge significantly smaller than the nominal value. These detrimental effects on the beam have been attributed to wakefields, in the cavity BPMs, in the multi-Optical Transition Radiation (OTR) systems as well as in other components of the beamline. The successful tests of a Wakefield-free Steering (WFS) algorithm at FACET have encouraged performing tests of the same correction scheme at ATF2. The performance of the algorithm has been simulated in detail, including several realistic imperfection scenarios, including charge-dependent BPMs resolution, and incoming injection error and position jitters, which are described in this paper. Tests of WFS have been performed at ATF2 during December 2014. The results are discussed here.

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MOPJE064

Beam Impedance Optimization of the TOTEM Roman Pots

impedance, detector, simulation, vacuum

452

N. Minafra
CERN, Geneva, Switzerland

The TOTEM experiment has been designed to measure the total proton-proton cross section and to study elastic and diffractive scattering at the LHC energy. The measurement requires detecting protons at distances as small as 1 mm from the beam center: TOTEM uses Roman Pots (RP), special beam pipe insertions, to move silicon detectors close to the beams to detect particles very near the beam axis. In the first period of running of the LHC no problems were detected with retracted Roman Pots and during insertions in special runs; however, during close insertions to highest intensity beam, impedance heating has been observed. After the LS1 the LHC beam current will increase and the equipment that can interact with the beam needed to be optimized. A new RP, optimized to minimize the beam coupling, has been designed with the help of CST Particle Studio; a prototype has been used to test the simulation results in the laboratory with wire and probe measurements. Furthermore, in both the old and the new RPs, new ferrites have been installed. The new ferrite material has a higher Curie temperature than the one used before LS1 and a thermal treatment at 1000°C has been applied to reduce the out-gassing.

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MOPJE069

General Functionality for Turn-Dependent Element Properties in SixTrack

simulation, HOM, collimation, optics

468

K.N. Sjobak, H. Burkhardt, R. De Maria, A. Mereghetti, A. Santamaría García
CERN, Geneva, Switzerland

In order to facilitate studies of how dynamically changing element attributes affect the dynamics of the beam and beam losses, the functionality for dynamic kicks (DYNK) of SixTrack has been significantly extended. This functionality can be used for the simulation of dynamic scenarios, such as when crab cavities are switched on, orbit bumps are applied, optics are changed, or failures occur. The functionality has been extended with a more general and flexible implementation, such that arbitrary time-dependent functions can be defined and applied to different attributes of families or individual elements, directly from the user input files. This removes the need for source code manipulation, and it is compatible with LHC@Home which offers substantial computing resources from volunteers. In this paper, the functionality and implementation of DYNK is discussed, along with examples of application to the HL-LHC crab cavities.

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MOPJE072

Simulations and Measurements of Longitudinal Coupled-bunch Instabilities in the CERN PS

feedback, synchrotron, luminosity, impedance

479

L. Ventura, H. Damerau, M. Migliorati, G. Sterbini
CERN, Geneva, Switzerland
M. Migliorati, L. Ventura
INFN-Roma1, Rome, Italy
M. Migliorati
University of Rome La Sapienza, Rome, Italy
L. Ventura
University of Rome "La Sapienza", Rome, Italy

Among various and challenging objectives of the LHC Injectors Upgrade project (LIU), one aim is to double the beam intensity of the CERN Proton Synchrotron (PS) in order to achieve the integrated luminosity target of the High-Luminosity LHC project (HL-LHC). A known limitation to reach the required high intensity is caused by the longitudinal coupled-bunch oscillations developing above the transition energy. The unwanted oscillations induce large bunch-to-bunch intensity variations not compatible with the specifications of the future LHC-type beams. A wide-band longitudinal damper has been installed in the PS to suppress these instabilities and is going to be commissioned. A measurement campaign of coupled-bunch oscillations has been launched to substantiate the extrapolations and predictions for the future High Luminosity LHC beam with the final aim to determine the maximum intensity that could be provided to the LHC. In parallel a Simulink© model of the PS is going to be implemented to predict the machine behavior in the parameter space of LIU and to be used during the beam commissioning and optimization of the feedback system.

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MOPJE076

Multi-objective Genetic Optimization with the General Particle Tracer (GPT) Code

solenoid, emittance, factory, target

492

S.B. van der Geer, M.J. de Loos
Pulsar Physics, Eindhoven, The Netherlands

In a typical design process there are a large number of variables, external constraints, and multiple conflicting objectives. Examples of the latter are short pulse, high charge, low emittance and low price. The classical solution to handle such problems is to combine all objectives into one merit function. This however implicitly assumes that the tradeoffs between all objectives are a-priori known. Especially in the early design stages this is hardly ever the case. A popular solution to this problem is to switch to multi-objective genetic optimization algorithms. This class of algorithms solves the problem by genetically optimising an entire population of sample solutions. Selection and recombination operators are defined such that the output, the so-called Pareto front, only includes solutions that are fully optimized where no objective can be improved without degrading any other. Here we present numerical studies and practical test runs of the genetic optimizer built into the General Particle Tracer (GPT) code.

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MOPJE081

Longitudinal Stability in Multi-Harmonic Accelerating Cavities

acceleration, accelerating-gradient, cathode, controls

506

R.M. Jones, L.R. Carver
UMAN, Manchester, United Kingdom
J.L. Hirshfield
Yale University, Physics Department, New Haven, CT, USA
Y. Jiang
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA

Accelerating cavities that excite multiple modes at integer harmonics of the fundamental frequency can potentially be used to limit the effects of rf breakdown and pulsed surface heating at high accelerating gradients. Understanding the longitudinal stability and the acceptance of such a cavity is important to their development and use. The general Hamiltonian for longitudinal stability in multi harmonic cavities is derived and the particle dynamics are explored.

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MOPJE083

Implications of Manufacturing Errors on Higher Order Modes and on Beam Dynamics in the ESS Linac

HOM, coupling, linac, wakefield

514

A. Farricker, R.M. Jones
UMAN, Manchester, United Kingdom
S. Molloy
ESS, Lund, Sweden

The European Spallation Source (ESS) in Lund, Sweden, will be a facility for fundamental physics studies of atomic structure using a spallation source of unparalleled brightness. To achieve this end, protons will be accelerated up to 2 GeV using a suite of cavities. Here we focus on the Medium Beta (β =0.67) elliptical superconducting cavities and we assess the influence of potential errors in fabrication to shift eigenmode frequencies onto an harmonic of the bunch frequency. If this occurs, and countermeasures are not adopted, the beam quality will be appreciably diluted *. We provide details on the geometrical parameters which are particularly sensitive to frequency errors from intensive finite element simulations of the electromagnetic fields. A circuit model is also employed to rapidly assess the shift in the eigenmodes from their anticipated design values due a variety of potential errors.
* Aaron Farricker et al, Physics Procedia, Proceedings of HOMSC14 (in press), 2014.

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MOPMA006

Modeling RF Feedback in Elegant for Bunch-Lengthening Studies for the Advanced Photon Source Upgrade

feedback, injection, storage-ring, impedance

540

T.G. Berenc, M. Borland
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice includes a passive bunch-lengthening cavity to alleviate lifetime and emittance concerns. Feedback in the main radio-frequency (rf) system affects the overall impedance presented to the beam in this double rf system. To aid beam stability studies, a realistic model of rf feedback has been developed and implemented in elegant and Pelegant.

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MOPMA007

Tracking Studies of a Higher-Harmonic Bunch-Lengthening Cavity for the Advanced Photon Source Upgrade

simulation, feedback, timing, impedance

543

M. Borland, T.G. Berenc, R.R. Lindberg, A. Xiao
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) multi-bend achromat (MBA) lattice will require a bunch-lengthening cavity to decrease the effects of Touschek scattering on the beam lifetime and of intrabeam scattering on the beam emittance. Using ELEGANT, we've performed tracking studies of a passive, i.e. beam-driven, fourth-harmonic cavity in the MBA lattice, including the predicted longitudinal impedance of the ring. The studies include an exploration of the required detuning and loaded Q of the main rf cavities and the harmonic cavity in order to stabilize the beam and achieve significant lengthening. We also studied the effects of bunch population variation and missing bunches. The computed bunch profiles are used for computation of the Touschek lifetime, verifying the beneficial effects in detail.

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MOPMA009

Improvements in Modeling of Collective Effects in ELEGANT

simulation, collective-effects, lattice, impedance

549

M. Borland, R.R. Lindberg, A. Xiao
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
ELEGANT has long had the ability to model collective effects in various ways, including beam-driven cavity modes, short-range wakes, and coherent synchrotron radiation. Recently, we made improvements specifically targeting simulations that require multiple bunches in storage rings. The ability to simulate long-range, non-resonant wakes was added, which can be used for example to study the effect of the resistive wall wake and multibunch instabilities. We also improved the implementation of short-range and resonant wakes to make them more efficient for multibunch simulations. Finally, improvements in the parallel efficiency were made that allow taking advantage of larger parallel resources.

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MOPMA016

Coupler RF Kick in the Input 1.3 GHz Accelerating Cavity of the LCLS-II Linac

focusing, HOM, accelerating-gradient, emittance

571

A. Lunin, N. Solyak, A.I. Sukhanov, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Main and HOM couplers break the cavity axial symmetry, distort RF field and, thus, create a transverse kick, even for a particle moving along the cavity axes. Dependence of a kick on the RF phase causes a beam emittance dilution and degrade the FEL radiation quality. The transverse kick is most dangerous for a beam passing through the first accelerating structure of a linac, where particles energy and their relativistic mass are low. In the paper we analyze the coupler RF kick in the first accelerating structure of the LCSL-II linac.

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MOPMA018

Simulation of Multipacting in SC Low Beta Cavities at FNAL

simulation, niobium, operation, linac

579

G.V. Romanov, P. Berrutti, T.N. Khabiboulline
Fermilab, Batavia, Illinois, USA

Proton Improvement Plan-II at Fermilab is a plan for improvements to the accelerator complex aimed at providing a beam power capability of at least 1 MW on target at the initiation of LBNE (Long Base Neutrino Experiment) operations. The central element of the PIP-II is a new 800 MeV superconducting linac, injecting into the existing Booster. Multipacting affects superconducting RF cavities in the entire range from high energy elliptical cavities to coaxial resonators for low-beta applications. This work is focused on multipacting study in the low-beta 325 MHz spoke cavities; namely SSR1 and SSR2, which are especially susceptible to the phenomena. The extensive simulations of multipacting in the cavities with updated material properties and comparison of the results with experimental data helped us to improve overall reliability and accuracy of these simulations. Our practical approach to the simulations is described in details. For SSR2, which has a high multipacting barrier right at the operating power level, some changes of the cavity shape to mitigate this harmful phenomenon are proposed.

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MOPMA026

Proposed Cavity for Reduced Slip-Stacking Loss

booster, injection, emittance, beam-loading

600

J.S. Eldred
Indiana University, Bloomington, Indiana, USA
J.S. Eldred, R.M. Zwaska
Fermilab, Batavia, Illinois, USA

This paper employs a novel dynamical mechanism to improve the performance of slip-stacking. Slip-stacking in an accumulation technique used at Fermilab since 2004 which nearly double the proton intensity. During slip-stacking, the Recycler or the Main Injector stores two particles beams that spatially overlap but have different momenta. The two particle beams are longitudinally focused by two 53 MHz 100 kV RF cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV RF cavity, with a frequency at the double the average of the upper and lower main RF frequencies. In simulation, we find the proposed RF cavity significantly enhances the stable bucket area and reduces slip-stacking losses under reasonable injection scenarios. We quantify and map the stability of the parameter space for any accelerator implementing slip-stacking with the addition of a harmonic RF cavity.

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MOPMA047

Nonlinear Beam Dynamics Studies of the Next Generation Strong Focusing Cyclotrons as Compact High Brightness, Low Emittance Drivers

cyclotron, focusing, proton, wakefield

656

S. Assadi, P.M. McIntyre, A. Sattarov
Texas A&M University, College Station, Texas, USA
N. Pogue
PSI, Villigen, Villigen, Switzerland

Funding: Work is partially supported by grants from the State of Texas (ASE) & the Michelle foundation.
The Strong Focusing Cyclotron development at Texas A&M University has evolved from stacks of cyclotrons to a single layer high brightness, low emittance to produce greater than 10 mA of proton beam to a desired target at 800 MeV. The latest design has a major geometric design optimization of strong focusing quadrupoles and a modified algorithm of high gradient cavities to address the small turn separation, and interaction of radially neighboring bunches and reduced the number of turns necessary to reach the desired final energy under control conditions. In this paper, we present the new design, physics of nonlinear synchrobetratron coupling, mνh+nνv=p causing beam blow-up in other form of cyclotrons and how we have resolved it. The cavity beam loading and space charge effects of multi turns at low energies to reduce losses are discussed.

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MOPMN002

Advances in Parallel Finite Element Code Suite ACE3P

simulation, radiation, SRF, electron

702

C.-K. Ng, L. Ge, C. Ko, O. Kononenko, Z. Li, L. Xiao
SLAC, Menlo Park, California, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
New capabilities in SLAC's parallel finite element electromagnetics simulation suite ACE3P are reported. These include integrated electromagnetic (Omega3P), thermal and mechanical (TEM3P) modules for multi-physics modeling, an interface to particle-material interaction codes for calculation of radiation effects due to dark current generation (Track3P), and coupled electromagnetic (ACE3P) and beam dynamics (IMPACT) simulation. Results from these applications are presented.

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MOPMN013

Simulation of Beam-Induced Plasma in Gas Filled Cavities

plasma, ion, simulation, electron

731

K. Yu, V. Samulyak
SBU, Stony Brook, USA
M. Chung
UNIST, Ulsan, Republic of Korea
B.T. Freemire
IIT, Chicago, Illinois, USA
V. Samulyak
BNL, Upton, Long Island, New York, USA
A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, Illinois, USA

Understanding of the interaction of muon beams with plasma in muon cooling devices is important for the optimization of the muon cooling process. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code, is used for the simulation support of the experimental program on the hydrogen gas filled RF cavity in the Mucool Test Area (MTA) at Fermilab. We have investigated the plasma dynamics in the RF cavity including the process of power dump by plasma (plasma loading), recombination of plasma, and plasma interaction with dopant material. By comparison with experiments in the MTA, simulations suggest several unknown properties of plasma such as the effective recombination rate, the electron attachment time on dopant molecule, and the ion - ion recombination rate in the plasma.

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MOPHA003

Status of ATF2 IP-BPM Project

feedback, electronics, operation, status

777

O.R. Blanco-García, P. Bambade, F. Bogard, P. Cornebise, S. Wallon
LAL, Orsay, France
D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich
JAI, Oxford, United Kingdom
P. Burrows, G.B. Christian, C. Perry
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
Y. Honda, K. Kubo, S. Kuroda, T. Naito, T. Okugi, T.T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan
S.W. Jang, E.-S. Kim
KNU, Deagu, Republic of Korea

The efforts during the second half of 2014 towards nano-metric beam position measurement and stabilization at the Interaction Point (IP) section of the Accelerator Test Facility (ATF) at KEK are presented. Recent improvements to the beam position monitor (BPM) data analysis and processing electronics, as well as the installation of a new set of C-Band BPMs, are reviewed.

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MOPHA010

RF Feedback and Detuning Studies for the BESSY Variable Pulse Length Storage Ring Higher Harmonic SC Cavities

beam-loading, feedback, synchrotron, operation

798

A. Neumann, P. Echevarria, P. Goslawski, M. Ries, M. Ruprecht, A.V. Vélez, G. Wüstefeld
HZB, Berlin, Germany

For the feasibility of the BESSY VSR upgrade project of BESSY II two higher harmonic systems at a factor of 3 and 3.5 of the ring's RF fundamental of 500 MHz will be installed in the ring. Operating in continuous wave at high average accelerating field of 20 MV/m and phased at zero-crossing, the superconducting cavities have to be detuned within tight margins to ensure stable operation and low power consumption at a loaded Q of 5·10⁷. The field variation of the cavities is mainly driven by the repetitive transient beam-loading of the envisaged complex bunch fill pattern in the ring. Within this work combined LLRF-cavity and longitudinal beam dynamics simulation will demonstrate the limits for stable operation, especially the coupling between synchrotron oscillation and RF feedback settings. Further impact by beam current decay and top-up injection shots are being simulated.
* G. Wüstefeld et al., IPAC 11, San Sebastiàn, Spain, p. 2936.

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MOPHA013

Superconducting Radio Frequency Cavity Degradation Due to Errant Beam

ion, ion-source, linac, vacuum

805

C.C. Peters, D. Curry, G.D. Johns
ORNL RAD, Oak Ridge, Tennessee, USA
A.V. Aleksandrov, W. Blokland, M.T. Crofford, C. Deibele, G.W. Dodson, J. Galambos, T.A. Justice, S.-H. Kim, T.A. Pelaia II, M.A. Plum, A.P. Shishlo
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05- 00OR22725 for the U.S. Department of Energy.
In 2009, the Superconducting Radio Frequency (SRF) cavities at the Spallation Neutron Source (SNS) began to experience significant operational degradation [1]. The source of the degradation was found to be repeated striking of cavity surfaces with errant beam pulses. The Machine Protection System (MPS) was designed to turn the beam off during a fault condition in less than 20 μseconds [2] as these errant beam pulses were not unexpected. Unfortunately an improperly operating MPS was not turning off the beam within the designed 20 μseconds, and the SRF cavities were being damaged. The MPS issues were corrected, and the SRF performance was restored with cavity thermal cycling and RF processing. However, the SRF cavity performance has continued to degrade, though at a reduced rate compared to 2009. This paper will detail further study of errant beam frequency, amount lost per event, causes, and the corrective actions imposed since the initial event.

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MOPHA019

Implementation of a High Level Phase Controller for the Superconducting Injector of the S-DALINAC

electron, controls, EPICS, injection

814

T. Bahlo, C. Burandt, F. Hug, N. Pietralla
TU Darmstadt, Darmstadt, Germany

Funding: This work has been supported by the DFG through CRC 634
The Superconducting DArmstadt LINear Accelerator S‑DALINAC is a recirculating electron accelerator with a design energy of 130 MeV. It operates in cw-mode at a radio frequency of 3 GHz and provides either unpolarized or polarized electron beams. Before entering the main accelerator the electron beam passes both, a normal-conducting injector beamline for beam preparation and a superconducting 10 MeV injector beamline for preacceleration. The phase of the beam which is injected into the 40 MeV main accelerator is crucial for the efficiency of the acceleration process and the minimization of the energy spread. Due to thermal drifts of the normal-conducting injector cavities this injection phase varies by about 0.2 degree over a timescale of an hour. In order to compensate these drifts, a high level phase controller has been implemented. It adjusts the phase measured at an rf-monitor at the exit of the superconducting injector by changing the phase of a prebuncher in the normal-conducting injector beamline. We will present the used hardware, the control algorithm as well as measurements showing the phase stabilization achieved by this controller.

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MOPHA021

Bunch-by-Bunch Longitudinal RF Feedback for Beam Stabilization at FAIR

feedback, LLRF, controls, synchrotron

820

K. Groß, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
U. Hartel, H. Klingbeil, U. Laier, D.E.M. Lens, K.-P. Ningel, S. Schäfer, B. Zipfel
GSI, Darmstadt, Germany

Funding: Work supported by the German Federal Ministry of Education and Research (BMBF) under the project 05P12RDRBF.
To damp undesired longitudinal oscillations of bunched beams, the main synchrotron SIS100 of FAIR (Facility for Antiproton and Ion Research) will be equipped with a bunch-by-bunch feedback system. This helps to stabilize the beam, to keep longitudinal emittance blow-up low and to minimize beam losses. The proposed LLRF (low level radio frequency) topology of the closed loop feedback system is described. In some aspects, it is similar to the beam phase control system* developed at GSI Helmholtzzentrum für Schwerionenforschung GmbH. The differences and challenges are pointed out, which are mainly the bunch-by-bunch signal processing followed by the generation of a correction voltage in dedicated feedback cavities. The adapted topology was verified at SIS18 during beam time in 2014 using LLRF prototype subsystems and the two existing ferrite-loaded acceleration cavities. The experimental setup to damp coherent longitudinal dipole oscillations is presented and evaluated with focus on the realized modifications, including ongoing and pending investigations. Finally, the current status of the longitudinal feedback system for FAIR is summarized.
* Klingbeil et al., IEEE Trans. Nuc. Sci., Vol. 54, No. 6, 2007.

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MOPHA024

A Novel Transverse Deflecting Cavity for Slice Diagnostics at BERLinPro

polarization, SRF, emittance, low-level-rf

827

A. Ferrarotto, B. Riemann, T. Weis
DELTA, Dortmund, Germany
H.-W. Glock, T. Kamps, J. Völker
HZB, Berlin, Germany

Funding: Work supported by BMBF under contract no. 05K10PEA
BERLinPro is an energy-recovery linac project to be realized at the Helmholtz-Zentrum Berlin (HZB) for an electron beam with 1mm mrad normalized emittance and 100 mA average current. The initial beam parameters are determined by the performance of the electron source, an SRF photo-electron injector. The development auf this SRF photon-electron injector is a main task of BERLinPro. Especially the beam emittance is basically defined by the SRF photogun. For beam diagnostics time dependent effects from the RF curvature and space charge must be taken into account and a sophisticated slice diagnostics is required. To perform this type of diagnostics a transverse deflecting cavity has been designed, characterized and is presently under construction.. This single cell cavity operates in a TM110-like mode at 1.3 GHz optimized for high transverse shuntimpedance of appr. 3.2 MOhm by a concentration of fields near the beam axis. The cavity has a novel geometry that allows for an operation with both polarizations of the TM110-Mode. The layout of the deflecting cavity will be presented together with the results of the low RF characterization.

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MOPHA028

Operation of Normal Conducting RF Guns with MicroTCA.4

gun, LLRF, feedback, operation

841

M. Hoffmann, V. Ayvazyan, J. Branlard, L. Butkowski, M.K. Grecki, U. Mavrič, M. Omet, S. Pfeiffer, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
W. Fornal, R. Rybaniec
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
A. Piotrowski
FastLogic Sp. z o.o., Łódź, Poland

During the last half year, the MicroTCA.4 based single cavity LLRF control system was installed and commissioned at several normal conducting facilities at DESY (FLASH RF gun, REGAE, PITZ RF gun, and XFEL RF gun). First tests during the last year show promising results in optimizing the system for high speed digital LLRF feedbacks, i.e. reducing system latency, increasing the internal controller processing speed, testing new control schemes, and optimizing controller parameters. In this contribution we will present results and gained experience from the commissioning phase and the first time period of real operation.

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MOPHA033

Physical Parameter Identification of Cross-Coupled Gun and Buncher Cavity at REGAE

gun, resonance, coupling, higher-order-mode

857

A.S. Nawaz, H. Werner
TUHH, Hamburg, Germany
M. Hoffmann, S. Pfeiffer, H. Schlarb
DESY, Hamburg, Germany

A reasonable description of the system dynamics is one of the key elements to achieve high performance control for accelerating modules. This paper depicts the system identification of a cross-coupled pair of cavities for the Relativistic Electron Gun for Atomic Exploration - REGAE. Two normal conducting copper cavities driven by a single RF source accelerate and compress a low charge electron bunch with sub 10 fs length at a repetition rate up to 50 Hz. It is shown how the model parameters of the cavities and the attached radio frequency subsystem are identified from data generated at the REGAE facility.

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MOPHA045

Developments and Performance of the LLRF System of the S-Band FERMI Linac

LLRF, klystron, feedback, controls

891

A. Fabris, F. Gelmetti, M. Milloch, M. Predonzani
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

The requirements on beam quality on the FERMI Free Electron Laser (FEL) linac impose challenging specifications on the stability of the RF fields that can only be met by using high reliable and high performance state of the art LLRF systems. The system installed in FERMI has met these requirements and is routinely operational for the machine on a 24/7 basis. The completion of the deployment of the LLRF units in 2015 increases the capabilities of the system, adding further measurement channels and monitoring, and allowing new functionalities. This paper provides an overview of the results achieved with the LLRF system of FERMI and an outlook of the further developments that are being implemented or planned.

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MOPHA052

Optimization of ILC Cryomodule Design Using Explosion Welding Technology

cryomodule, niobium, cryogenics, neutron

913

A. Basti
University of Pisa and INFN, Pisa, Italy
F. Bedeschi
INFN-Pisa, Pisa, Italy
Ju. Boudagov, B.M. Sabirov, G. Shirkov, Yu.V. Taran
JINR, Dubna, Moscow Region, Russia
A. Bryzgalin, L. Dobrushin, S. Illarionov, E. Pekar
PWI, Kiev, Ukraine
P. Fabbricatore
INFN Genova, Genova, Italy

Optimization of ILC cryomodule design using explosion welding technology. B.Sabirov, J.Budagov, G.Shirkov - JINR, Dubna, Russia A.Basti, F.Bedeschi, P.Fabbricatore - INFN, Pisa/Genova, Italy A.Bryzgalin, L.Dobrushin, S.Illarionov, E.Pekar - EWI, Kiev, Ukraine JINR activity in the ILC Project is the development, in association with INFN, of techniques to simplify and make cheaper the construction of the ILC cryomodules. In the current ILC TDR design both the helium vessel shell and the connected pipes are made of expensive titanium, one of the few metals that can be welded to niobium by the electron beam technique. We describe the construction and performance of transition elements, obtained by explosion welding, that can couple the niobium cavity with a stainless steel helium vessel. Several designs for these transitions have been produced and studied showing varying levels of reliability. Based on this experience a new design, including a minimal titanium intermediate layer, has been built. Preliminary tests yield impressive results, indicating a very strong resistance of the bon

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MOPHA053

Radiation Measurements of a Medical Particle Accelerator Through a Passive Resonant Cavity

linac, detector, coupling, radiation

917

A. Leggieri, F. Di Paolo, D. Passi
Università degli Studi di Roma "Tor Vergata", Roma, Italy
A. Ciccotelli, S. De Stefano, G. Felici, F. Marangoni
S.I.T., Aprilia, Italy

Beam monitoring system are required by technical standards for the real time measurement of the dose delivered to the target while the beam is crossing them * **. Traditional beam current monitoring systems are based on ionization chambers and requires high voltage biases *** ****. This study investigates on the measurements of the electron beam current emitted by a medical electron linear accelerator using the power exchange of the beam current with a passive resonant cavity ***** placed at the output interface of the accelerator. The cavity is magnetically coupled with a coaxial transmission line loaded on a microwave envelope detector and its output signal has been documented while receiving several electron currents. This paper shows the complete equivalency, in terms of global performance, of the current revelation performed by exploiting the cavity-beam interaction principle with the classical technology, based on ionization chambers, however without need of high voltage. The most important point is that the resonant cavity system, by measuring the beam current, gives a direct measurement of a physical observable quantity directly related with the dose deposed by the beam.
* EN 60601-2-1, 2009.
** A.P. Turner, 1979.
*** V.L. Uvarov, 1997.
**** M. Ruf∗, 2014.
***** J.B. Rosenzweig, 2003

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MOPHA056

Status of LLRF Control System for SuperKEKB Commissioning

controls, LLRF, beam-loading, klystron

924

T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri
KEK, Ibaraki, Japan
H. Deguchi, K. Hayashi, T. Iwaki, M. Ryoshi
Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo, Japan

Beam commissioning of the SuperKEKB will be started in JFY2015. A new LLRF control system, which is an FPGA-based digital RF feedback control system on the MicroTCA platform, has been developed for high current beam operation of the SuperKEKB. The mass production and installation of the new systems has been completed as scheduled. The new LLRF control systems are applied to nine RF stations (klystron driving units) among existing thirty stations. As a new function, klystron phase lock loop was digitally implemented within the cavity FB control loop in the FPGA, and in the high power test it worked successfully to compensate for the klystron phase change. Beam loading was also simulated in the high power test by using an ARES cavity simulator, and then good performance in the cavity-voltage feedback control and the cavity tuning control was demonstrated to compensate the large beam loading for the SuperKEKB parameters. Fabrication of another new LLRF control system for damping ring which is required for low-emittance positron injection is scheduled in JFY2015.

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MOPTY008

Preliminary Hardware Implementation of Compensation Mechanism of Superconducting Cavity Failure in C-ADS Linac

FPGA, hardware, linac, proton

953

Z. Xue, J.P. Dai
IHEP, Beijing, People's Republic of China
L. Cheng, Y. Yang
SINANO, Suzhou, People's Republic of China

For the proton linear accelerators used in applications such as ADS, due to the nature of the operation, it is essential to have beam failures at the rate several orders of magnitude lower than usual performance of similar accelerators. In order to achieve this extremely high performance reliability requirement, in addition to hardware improvement, a failure tolerant design is mandatory. A compensation mechanism to cope with hardware failure, mainly RF failures of superconducting cavities, will be in place in order to maintain the high uptime, short recovery time and extremely low frequency of beam loss. The hardware implementation of the mechanism poses high challenges due to the extremely tight timing constraints, high logic complexity, and mostly important, high flexibility and short turnaround time due to varying operation contexts. We will explore the hardware implementation of the scheme using fast electronic devices and Field Programmable Gate Array (FPGA). In order to achieve the goals of short recovery time and flexibility in compensation algorithms, an advanced hardware design methodology including high-level synthesis will be used.

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MOPTY014

An Experimental Study of Higher-Order Modes Excited by High Repetition Rate Electron Beam in an SRF Cavity

HOM, electron, SRF, experiment

965

Y. Gao, J.E. Chen, L.W. Feng, J.K. Hao, S. Huang, L. Lin, K.X. Liu, X. Luo, S.W. Quan, F. Wang, Zh.W. Wang
PKU, Beijing, People's Republic of China

Funding: National Natural Science Foundation of China (No. 11275014)
Higher-order modes (HOMs) excited by electron beam traversing a superconducting rf (SRF) cavity contain lots of information and can be used for intra-cavity electron beam diagnostics. Unlike single bunch, multiple bunches would excite HOMs with a much complicated spectrum. In this paper, we present our recent research on HOMs excited by a high repetition rate electron beam in an SRF cavity. Especially, we focus on the integer multiple frequency peaks in the HOM spectrum, which are determined by the nearest eigen HOM peaks. The experiments were carried out on the DC-SRF photoinjector, which was operated at MHz repetition rate. The results agree well with theoretic analysis.

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MOPTY016

Study of Diamond Detector Application at the Front End of a High Intensity Hadron Accelerator

detector, radiation, hadron, proton

972

G. Ren, D.H. He, W. Li, Y. Li
USTC/NSRL, Hefei, Anhui, People's Republic of China
M. Zeng
Tsinghua University, Beijing, People's Republic of China

Diamond detectors function as beam loss or luminosity monitors for high energy accelerators, such as LHC, Babar, etc. Because of regular detectors‘ insufficient protection of the front end, diamond detectors owning significant characteristics, like time resolution in the nanosecond range, radiation hardness and negligible temperature dependence. Thus, diamond detectors have been becoming promising candidates for detecting BLMs of fully super-conducting hadron accelerator, such as C-ADS, FRIB. In this paper, the sensitivity of diamond detectors was simulated by Monte Carlo program FLUKA and GEAN4. Meanwhile, we tested the performance of a new prototype of CVD diamond detector, and compared it with Si-PIN and Bergoz detectors at the storage ring of the HLS II. The results of the diamond detector were consistent with other two detectors well. More evaluation of diamond detectors in low energy radiation field are ongoing.

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MOPTY025

High-current RFQ Design Study on RAON

rfq, emittance, ion, acceleration

990

J. Bahng, E.-S. Kim
Kyungpook National University, Daegu, Republic of Korea
B.H. Choi
IBS, Daejeon, Republic of Korea

Rare isotope Accelerator Of Newness (RAON) heavy ion accelerator has been designed as a facility for a rare isotepe accelerator of the Rare Isotope Science Project (RISP). RAON provides 400 kW CW heavy ion beams from proton to uranium to support researches in various science fields. The RAON system consists of a few ECR ion source, low energy beam transport systems (LEBTs), CW radio frequency quadrupole (RFQ) accelerators, a medium energy beam transport and superconducting linac. We present the design study of the RFQ accelerator from 30 keV/u to 1.5 MeV/u of deuteron beam with meeting a requirement of over 15 mA beam at the target. We optimized the normal conducting CW RFQ accelerator that has a high transmission and a low longitudinal emittance. In this paper, we will present the design result of RFQ beam dynamics studies and its 2D and 3D EM analysis.

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MOPTY038

NSLS-II Digital RF Controller Logic and Applications

EPICS, FPGA, feedback, controls

1010

B. Holub, F. Gao, J.G. Kulpin, C. Marques, J. Oliva, J. Rose, N.A. Towne
BNL, Upton, New York, USA

The National Synchrotron Light Source II accelerator consists of the Storage Ring, the Booster Ring, and Linac along with their associated cavities. NSLS II is committed to the use of digital RF controllers for controlling these cavities. Given the number, types and variety of functions of these cavities, we sought to limit the logic development effort by reuse of parameterized code on one hardware platform. Currently we have fielded six controllers in the NSLS II system. There are two controllers each in both the Storage ring and Booster. The first controller in each is used to control the cavity field and the second controller used for diagnostics. In the Linac a controller is provided which modulates the eGUN grid to generate the bunches. Lastly, in the Master Oscillator Distribution System a controller is used to make phase corrections to the outgoing master oscillator clock signal to account for thermal phase drifts along the distribution path.

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MOPTY042

ALBA LLRF Upgrades to Improve Beam Availability

LLRF, beam-loading, operation, synchrotron

1022

A. Salom, B. Bravo, J. Marcos, F. Pérez
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

ALBA is a 3GeV synchrotron light source located in Barcelona and operating with users since May 2012. The RF system of the SR is composed of six cavities, each one powered by combining the power of two 80 kW IOTs through a Cavity Combiner (CaCo). At present, there are several RF interlocks per week. The redundancy given by the six cavities makes possible the survival of the beam after one of these trips. In these cases, the cavity has to be recovered with the circulating beam. An autorecovery process has been implemented in the digital LLRF system in order to recover the faulty RF plant after a trip. But these trips also create perturbations to the beam stability. In order to minimize the beam perturbations induced by these RF interlock, an additional feed-forward loop is being implemented. The functionally, main parameters and test results of these new algorithms will be presented.

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MOPTY052

Experimental and Simulation Studies of Hydrodynamic Tunneling of Ultra-Relativistic Protons

target, simulation, proton, experiment

1048

F. Burkart, R. Schmidt, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland
A.R. Piriz
Universidad de Castilla-La Mancha, Ciudad Real, Spain
A. Shutov
IPCP, Chernogolovka, Moscow region, Russia
N.A. Tahir
GSI, Darmstadt, Germany

The expected damage due to the release of the full LHC beam energy at a single aperture bottleneck has been studied. These studies have shown that the range of the 7 TeV LHC proton beam is significantly extended compared to that of a single proton due to hydrodynamic tunneling effect. For instance, it was evaluated that the protons and their showers will penetrate up to a length of 25 m in solid carbon compared to a static range of around 3 m. To check the validity of these simulations, beam- target heating experiments using the 440 GeV proton beam generated by the SPS were performed at the HiRadMat test facility at CERN *. Solid copper targets were facially irradiated by the beam and measurements confirmed hydrodynamic tunneling of the protons and their showers. Simulations have been done by running the energy deposition code FLUKA and the 2D hydrodynamic code, BIG2, iteratively. Very good agreement has been found between the simulations and the experimental results ** providing confidence in the validity of the studies for the LHC. This paper presents the simulation studies, the results of a benchmarking experiment, and the detailed target investigations.
* N.A. Tahir et al., Phys. Rev. Special Topics Accel. Beams 15 (2012) 051003.
** R. Schmidt et al., Phys. Plasmas 21 (2014) 080701.

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MOPTY083

Progress towards Electron-beam Feedback at the Nanometre Level at the Accelerator Test Facility (ATF2) at KEK

feedback, kicker, extraction, electron

1133

P. Burrows, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, G.B. Christian, M.R. Davis, C. Perry
JAI, Oxford, United Kingdom
D.R. Bett
CERN, Geneva, Switzerland

Ultra-low latency beam-based digital feedbacks have been developed by the Feedback On Nanosecond Timescales (FONT) Group and tested at the Accelerator Test Facility (ATF2) at KEK in a programme aimed at beam stabilisation at the nanometre level at the ATF2 final focus. Three prototypes were tested: 1) A feedback system based on high-resolution stripline BPMs was used to stabilise the beam orbit in the beamline region c. 50m upstream of the final focus. 2) Information from this system was used in a feed-forward mode to stabilise the beam locally at the final focus. 3) A final-focus local feedback system utilising cavity BPMs was deployed. In all three cases the degree of beam stabilisation was observed in high-precision cavity BPMs at the ATF2 interaction point. Latest results are reported on stabilising the beam position to below 100 nanometres.

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MOPWI021

The LCLS-II LLRF System

controls, LLRF, cryomodule, linac

1195

C. Hovater, R. Bachimanchi
JLab, Newport News, Virginia, USA
S. Babel, B. Hong, D. Van Winkle
SLAC, Menlo Park, California, USA
B.E. Chase, E. Cullerton, P. Varghese
Fermilab, Batavia, Illinois, USA
L.R. Doolittle, G. Huang, A. Ratti, C. Serrano
LBNL, Berkeley, California, USA

Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515.
The SLAC National Accelerator Laboratory is planning an upgrade (LCLS-II) to the Linear Coherent Light Source with a 4 GeV CW superconducting (SCRF) linac. The SCRF linac consists of 35 ILC style cryomodules (eight cavities each) for a total of 280 cavities. Expected cavity gradients are 16 MV/m with a loaded QL of ~ 4x10⁷. The RF system will have 3.8 kW solid state amplifiers driving single cavities. To ensure optimum field stability a single source single cavity control system has been chosen. It consists of a precision four channel cavity receiver and RF stations (Forward, Reflected and Drive signals). In order to regulate the resonant frequency variations of the cavities due to He pressure, the tuning of each cavity is controlled by a Piezo actuator and a slow stepper motor. In addition the system (LLRF-amplifier-cavity) is being modeled and cavity microphonic testing has started. This paper describes the LLRF system under consideration, including recent modeling and cavity tests.

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MOPWI025

Phase and Amplitude Tuning Algorithms for the FRIB Superconducting Cavities

linac, acceleration, simulation, SRF

1207

Y. Zhang, P. Chu, Z.Q. He
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
FRIB driver linac will deliver all heavy ion beams up to uranium with energy above 200 MeV/u, and maximum beam power on target 400 kW for nuclear physics research. Phase and amplitude tuning of the FRIB superconducting cavities – totally about 330 of them, are important to the linac beam commissioning at low power and normal operation at high power. Because relatively low beam energy and high acceleration gradient, beam velocity changes significantly in the cavity RF gaps and the beam bunch cannot preserve perfectly in the further downstream beam diagnostics systems, beam longitudinal tuning algorithms are studied for different FRIB cavities and at different beam energy, which include the acceleration cavities as well as the re-buncher cavities.

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MOPWI028

Initial Experimental Results of a Machine Learning-Based Temperature Control System for an RF Gun

controls, gun, monitoring, network

1217

A.L. Edelen, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA
B.E. Chase, D.J. Crawford, N. Eddy, D.R. Edstrom, E.R. Harms, J. Ruan, J.K. Santucci, P. Stabile
Fermilab, Batavia, Illinois, USA

Colorado State University (CSU) and Fermi National Accelerator Laboratory (Fermilab) have been developing a control system to regulate the resonant frequency of an RF electron gun. As part of this effort, we present experimental results for a benchmark temperature controller that combines a machine learning-based model and a predictive control algorithm for improved settling time, overshoot, and disturbance rejection relative to conventional techniques. Such improvements have implications for machine up-time and management of reflected power. This work is part of an on-going effort to develop adaptive, machine learning-based tools specifically to address control challenges found in particle accelerator systems.

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MOPWI045

The CEBAF Element Database and Related Operational Software

database, hardware, controls, software

1256

T. L. Larrieu, M.E. Joyce, M. Keesee, C.J. Slominski, R.J. Slominski, D.L. Turner
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The newly commissioned 12 GeV CEBAF accelerator relies on a flexible, scalable and comprehensive database to define the accelerator. This database delivers the configuration for CEBAF operational tools, including hardware checkout, the downloadable optics model, control screens, and much more. The presentation will describe the flexible design of the CEBAF Element Database (CED), its features and assorted use case examples.

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MOPWI047

Architectural Improvements and New Processing Tools for the Open XAL Online Model

simulation, hardware, software, coupling

1262

C.K. Allen, T.A. Pelaia II
ORNL, Oak Ridge, Tennessee, USA
J.M. Freed
University of South Carolina, Columbia, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
The Open XAL online model is the component of Open XAL* providing accelerator modeling dynamic synchronization to live hardware. Several significant architectural enhancements and feature additions have been made concerning the handling and processing of simulation data. The major structural change is the creation of a single class Trajectory<> that manages all simulation data. Another significant design change was the development of standard tools for processing simulation results. One may obtain machine parameters such as fixed orbit, phase advance, dispersion, etc., or beam-based calculations such as RMS size and centroid location simply by passing simulation results, i.e. a Trajectory<> object, to these computation tools. Finally, the ability to fully create composite modeling elements was implemented in the online model. Specifically, accelerator hardware can be modeled as a collection of constituent modeling elements. This sub-structure capability is extremely useful for modeling RF cavities consisting of coupled RF gaps coupled and drift spaces. We present an overview of the new architecture and how it is used when building applications.
* http://xaldev.sourceforge.net/

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TUAC3

Optimization of Beam Loss Monitor Network for Fault Modes

detector, network, simulation, lattice

1356

Z. Liu, Z.Q. He, S.M. Lidia, D. Liu, Q. Zhao
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
Beam Loss Monitoring (BLM) System is an essential part to protect accelerator from machine faults. Compared with the empirical or uniform BLM arrangement in most accelerators, our new optimization approach proposes a “minimum spatial distribution” for BLM network. In this distribution, BLMs shall be placed at a small set of “critical positions” that can detect all failure / FPS trigger-able events of each fault mode. In additional, to implement a more advanced function of fault diagnosis, BLM should also be placed at “discrimination points” for fault-induced loss pattern recognition. With examples of FRIB failure event simulations, the author demonstrates the proof of concept to locate these “critical positions” and “discrimination points” for the minimum spatial distribution of BLMs.

Slides TUAC3 [2.341 MB]

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TUPWA009

50 MeV Electron Linac with a RF Gun and a Thermoionic Cathode

gun, linac, focusing, cathode

1413

A.S. Setty, A.S. Chauchat, D. Fasse, D. Jousse, P. Sirot
Thales Communications & Security (TCS), Gennevilliers Cedex, France

The low energy part of our pre injectors is made up of a 90 kV DC themoionic trioode gun, followed by a 500 MHz sub harmonic prebuncher and a 3 GHz prebuncher. We propose a new design for a 50 MeV linac with a RF gun *. this study will compare the beam dynamics simulations for the new design and for our previous pre injectors.
* A. Setty et al. "Study of a RF gun with a Thermoionic Cathode", Proceeding IPAC 2014, Germany, Dresden, June 2014.

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TUPWA018

Progress Report of the Berlin Energy Recovery Project BERLinPro

gun, SRF, booster, electron

1438

M. Abo-Bakr, W. Anders, K.B. Bürkmann-Gehrlein, A. Burrill, A.B. Büchel, P. Echevarria, A. Frahm, H.-W. Glock, A. Jankowiak, C. Kalus, T. Kamps, G. Klemz, J. Knobloch, J. Kolbe, J. Kühn, O. Kugeler, B.C. Kuske, P. Kuske, A.N. Matveenko, A. Meseck, R. Müller, A. Neumann, N. Ohm, K. Ott, E. Panofski, F. Pflocksch, D. Pflückhahn, J. Rahn, J. Rudolph, M. Schmeißer, O. Schüler, J. Völker
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association
The Helmholtz Zentrum Berlin is constructing the Energy Recovery Linac Project BERLinPro on its site in Berlin Adlershof. The project is intended to expand the required accelerator physics and technology knowledge mandatory for the design, construction and operation of future synchrotron light sources. The project goal is the generation of a high current (100 mA), high brilliance (norm. emittance below 1 mm mrad) cw electron beamat 2~ps rms bunch duration or below. The planning phase of the project is completed and the design phase of most of the components is finished. Many of them have already been ordered. After some delay the construction of the building has started in February 2015. The status of the various subprojects as well as a summary of current and future activities will be given. Major project milestones and details of the project time line will be finally introduced.

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TUPWA020

BNL ATF II Beamlines Design

experiment, electron, laser, linac

1445

M.G. Fedurin, Y.C. Jing, D. Stratakis, C. Swinson
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Brookhaven National Lab. Accelerator Test Facility (BNL ATF) is currently undergoing a major upgrade (ATF-II). Together with a new location and much improved facilities, the ATF will see an upgrade in its major capabilities: electron beam energy and quality and CO2 laser power. The electron beam energy will be increased in stages, first to 100-150 MeV followed by a further increase to 500 MeV. Combined with the planned increase in CO2 laser power (from 1-100 TW), the ATF-II will be a powerful tool for Advanced Accelerator research. A high-brightness electron beam, produced by a photocathode gun, will be accelerated and optionally delivered to multiple beamlines. Besides the energy range (up to a possible 500 MeV in the final stage) the electron beam can be tailored to each experiment with options such as: small transverse beam size (<10 um), flat beam, short bunch length (<100 fs) and, combined short and small bunch options. This report gives a detailed overview of the ATF-II capabilities and beamlines configuration.

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TUPWA023

A Step Closer to the CW High Brilliant Beam with the ELBE SRF-Gun-II

gun, SRF, cathode, electron

1456

R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate
HZDR, Dresden, Germany

In order to achieve the CW electron beam with a high average current up to 1 mA and a very low emittance of 1 μm, an improved superconducting photo-injector (ELBE SRF-Gun-II) has been installed and commissioned at HZDR since 2014. This new gun replaces the first 3.5-cell SRF gun (SRF-Gun-I) at the SC Linac ELBE. The RF performance of the niobium cavity has been evaluated, the beam parameters for low charge bunches have been measured, and the first beam has been guided into the ELBE beam line. The results agree with the simulation very well. The photocathode transfer system has been installed for the first high current beam test planned in 2015. However, the unexpected strong degradation on the cavity and also on the photocathode was found soon after the first photocathode exchange. In this contribution the results of the SRF-Gun-II commissioning and the latest experiment will be presented in detail.

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TUPWA029

ARES: Accelerator Research Experiment at SINBAD

electron, bunching, experiment, linac

1469

B. Marchetti, R.W. Aßmann, C. Behrens, R. Brinkmann, U. Dorda, K. Flöttmann, J. Grebenyuk, M. Hüning, Y.C. Nie, H. Schlarb, J. Zhu
DESY, Hamburg, Germany

ARES is a planned linear accelerator for R&D for production of ultra-short electron bunches. It will be hosted at the SINBAD facility, at DESY in Hamburg*. The goal of ARES is to produce low charge (0.2-50pC), ultra-short (from few fs to sub-fs) bunches, with high arrival time stability (less than 10fs) for various applications, such as external injection for Laser Plasma Wake-Field acceleration**. The baseline layout of the accelerator foresees an S-band photo-injector which compresses low charge electron bunches via velocity bunching and accelerates them to 100 MeV energy. In the second stage, it is planned to install a third S-band accelerating cavity to reach 200 MeV as well as two X-band cavities: One for the linearization of the longitudinal phase space (subsequently allowing an improved bunch compression) and another one as a transverse deflecting cavity for longitudinal beam diagnostics. Moreover a magnetic bunch compressor is envisaged allowing to cut out the central slice of the beam*** or hybrid bunch compression.
* R. Assmann et al., TUPME047, Proceedings of IPAC 2014.
** R. Assmann, J. Grebenyuk, TUOBB01, Proceedings of IPAC 2014.
*** P. Emma et al., PRL 92 7 (2004).

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TUPWA058

Study of a C-band Harmonic RF System to Optimize the RF Bunch Compression Process of the SPARC Beam

gun, linac, experiment, emittance

1552

A. Gallo, D. Alesini, M. Bellaveglia, M. Ferrario
INFN/LNF, Frascati (Roma), Italy
A. Bacci, V. Petrillo, A.R. Rossi, L. Serafini
Istituto Nazionale di Fisica Nucleare, Milano, Italy
F. Cardelli, L. Piersanti
INFN-Roma1, Rome, Italy
B. Marchetti
DESY, Hamburg, Germany
M. Rossetti Conti
Universita' degli Studi di Milano & INFN, Milano, Italy

The SPARC linac at the INFN Frascati Labs is a high brilliance electron source with a wide scientific program including production of THz and Thomson backscattering radiation, FEL studies and plasma wave acceleration experiments. The linac is based on S-band RF and consists in an RF Gun followed by 3 accelerating structures, while an energy upgrade based on 2 C-band accelerating structures is ready to be implemented. Short bunches are ordinarily produced by using the linear RF bunch compression concept. A harmonic RF structure interposed between the Gun and the 1st accelerating structure can be used to optimize the RF compression by a longitudinal phase space pre-correction, allowing to reach shorter bunches, a much more uniform current distribution and in general to control better the whole compression process. Here we report the results of numerical studies on the SPARC bunch compression optimization through the use of a harmonic cavity, and the design of a C-band RF system to implement it. The proposed system consists in a multi-cell SW cavity powered by a moderate portion of the total RF power spilled from the C-band power plant already installed for the linac energy upgrade.

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TUPWA063

FEL Enhancement by Microbuch Structure Made with Phase-Space Rotation

FEL, laser, simulation, bunching

1570

M. Kuriki, Y. Seimiya
HU/AdSM, Higashi-Hiroshima, Japan
S. Chen, K. Ohmi, J. Urakawa
KEK, Ibaraki, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
R. Kato
ISIR, Osaka, Japan

Funding: This work is partly supported by MEXT/JSPS KAKENHI (Grant-in-Aid for scientic research) 25390126, Japan.
FEL is one of the ideal radiation source over the wide range of wavelength region with a high brightness and a high coherence. Many methods to improve FEL gain has been proposed by introducing an active modulation on the bunch charge distribution. The transverse-longitudinal phase-space rotation is one of the promising method to realize the density modulation as the micro-bunch structure. Initially, a beam density modulation in the transverse direction made by a mechanical slit, is properly transformed into the density modulation in the longitudinal direction by the phase-space rotation. The micro-bunch structure made with this method has a large tunability by changing the slit geometry, the beam line design, and the beam dynamics tuning. For FEL, enegy chirp made by the emittance exchange and chromaticity made by this chirp should be properly corrected. Simulation results and possible applications are discussed.

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TUPWA065

Generation of Multi-bunch Beam with Beam Loading Compensation by Using RF Amplitude Modulation in Laser Undulator Compact X-ray (LUCX)

electron, laser, gun, booster

1576

M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
K. Sakaue, M. Washio
RISE, Tokyo, Japan

We have developed a compact X-ray source based on inverse Compton scattering between an electron beam and a laser pulse stacked in an optical cavity at Laser Undulator Compact X-ray (LUCX) accelerator in KEK. The accelerator consists of a 3.6 cell photo-cathode rf-gun, a 12cell standing wave accelerating structure and a 4-mirror planar optical cavity. Our aim is to obtain a clear X-ray image in a shorter period of times and the target flux of X-ray is 1.7x10⁷ photons/pulse with 10% bandwidth at present. To achieve this target, it is necessary to increase the intensity of an electron beam to 500nC/pulse with 1000 bunches at 30 MeV. Presently, we have achieved the generation of 24MeV beam with total charge of 600nC in 1000bunches with beam-loading compensation by using the delta T method and the amplitude modulation of RF pulse. The bunch-by-bunch energy difference is within 1.3% peak to peak. We will report the results of the multi-bunch beam generation and acceleration in this accelerator.
This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

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TUPWA066

Development of a High Average Power Laser for High Brightness X-ray Source and Imaging at cERL

laser, electron, detector, photon

1579

A. Kosuge, T. Akagi, S. Araki, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
R. Hajima, M. Mori, T. Shizuma
JAEA, Ibaraki-ken, Japan
R. Nagai
JAEA/ERL, Ibaraki, Japan

Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan.
High brightness X-rays via laser-Compton scattering (LCS) of laser photons stored in an optical cavity by a relativistic electron beam is useful for many scientific and industrial applications such as X-ray imaging. The construction of compact Energy Recovery Linac (cERL) is now in progress at KEK to generate low-emittance and high-current electron beams. In order to demonstrate the generation of high brightness LCS X-rays, it is necessary to develop a high average power injection laser and an optical four-mirror ring cavity with two concave mirrors which is used to produce a small spot laser beam inside the cavity. In this presentation, we will show the result of the development of the high average laser system, the LCS X-rays generation, and the X-ray imaging.

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TUPWA068

Simulation Study of Beam Halo and Loss for KEK Compact ERL

simulation, laser, gun, electron

1587

O. Tanaka, T. Miyajima, N. Nakamura, S. Sakanaka, M. Shimada
KEK, Ibaraki, Japan

At the KEK Compact ERL (cERL) designed to operate at high-brilliance and high-current electron beams, the maximum averaged current was recorded at 6.5 muA for the beam energy of 20 MeV on March 2014 and should be increased up to 10 mA in a step-by-step manner in a few years. In order to increase the beam current by reducing the beam loss, we need to know the mechanism of the beam loss. For this purpose we investigate beam halo originated from characteristics and imperfections of an electron gun system, using the tracking code GPT (General Particle Tracer). The beam halo can be lost by the beam-pipe apertures and the collimators in the cERL beam line. In this paper, we will present the simulation results including the beam halo formation and the beam loss distribution along the beam line.

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TUPJE002

Demonstration of High-flux Photon Generation from an ERL-based Laser Compton Photon Source

laser, photon, electron, linac

1607

R. Nagai, R. Hajima, M. Mori, T. Shizuma
JAEA, Ibaraki-ken, Japan
T. Akagi, S. Araki, Y. Honda, A. Kosuge, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

A high-flux photon source from the laser Compton scattering (LCS) by an electron beam in an energy-recovery linac (ERL) is a key technology for a nondestructive assay system to identify nuclear materials. In order to demonstrate accelerator and laser technologies required for a LCS photon generation, a LCS photon source is under construction at the Compact ERL (cERL). The LCS photon source consists of a mode-locked fiber laser and a laser enhancement cavity. Flux monitors and a data aqcuisition system are also under construction. The commissioning of the LCS photon source will be started in February 2015 and LCS photon generation is scheduled in March 2015. The demonstration result of the LCS photon source will be presented in detail.

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TUPJE003

Quasi-Traveling Wave RF Gun and Beam Commissioning for SuperKEKB

gun, laser, cathode, emittance

1610

T. Natsui
The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
Y. Ogawa, M. Yoshida, X. Zhou
KEK, Ibaraki, Japan

We are developing a new RF gun for SuperKEKB. High charge low emittance electron and positron beams are required for SuperKEKB. We will generate 7.0 GeV electron beam at 5 nC 20 mm-mrad by J-linac. In this linac, a photo cathode S-band RF gun will be used as the electron beam source. For this reason, we are developing an advanced RF gun which has two side coupled standing wave field. We call it quasi-traveling wave side couple RF gun. This gun has a strong focusing field at the cathode and the acceleration field distribution also has a focusing effect. This RF gun has been installed in the KEK J-linac. Beam commissioning with the RF gun is in progress.

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TUPJE009

Study on Frequency Multiplier of a Pulsed Laser Repetition using an Optical Cavity

laser, gun, electron, cathode

1629

T. Kobayashi
Waseda University, Tokyo, Japan

We have been studying a compact electron accelerator based on an S-band Cs-Te photo-cathode rf gun at Waseda University. The system is using S-band rf of 2856MHz. When a repetition of the electron bunch is integral multiple of rf, it enables a lot of electron bunch acceleration for the rf gun. The repetition of the electron bunch generated by a photo-cathode rf gun depends on the oscillating frequency of the pulsed mode-locked laser. We have been developing a mode-locked Yb-doped fiber laser based on Non-Linear Polarization Rotation (NLPR). However, its repetition is limited by the fiber length to produce NLPR. Therefore, we have started to develop the external optical cavity which is multiplier of a pulsed laser repetition. It would enable the rf gun to generate high-dose electron beam in a very short time. In this conference, we will report design of the external optical cavity to multiply the pulsed laser repetition, the experimental results of the frequency multiplying of a mode-locked Yb-doped fiber laser, and the future prospects.
Work supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

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TUPJE011

Laser-Compton Scattering X-ray Source Based on Normal Conducting Linac and Optical Enhancement Cavity

laser, electron, linac, photon

1635

K. Sakaue, M. Washio
Waseda University, Tokyo, Japan
S. Araki, M.K. Fukuda, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Funding: Work supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
We have been developing a compact X-ray source via laser-Compton scattering (LCS) at KEK-LUCX (Laser Undulator Compact X-ray source) facility. The LUCX system is based on S-band normal conducting linac with an energy of 30 MeV and optical enhancement cavity for photon target. As a photon target, we invented a burst mode laser pulse storage technique for a normal conducting linac, which enables to store the high power laser pulses at the timing of electron bunchs. The peak storage power exceeds to more than 250 kW with 357 MHz repetition. Electron linac is under operation with multi-bunch mode, 1000 bunches/train with 600 pC charge in each bunches. We have succeeded to produce 1000 pulse/train LCS X-ray train. Combining high repetition rate electron linac and burst mode optical enhancement cavity, more than 10⁹ ph./sec/10%b.w. flux would be possible. In this conference, the introduction of our test facility LUCX, recent expermental results, and future prospective including normal conducting LCS X-ray source will be presented.

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TUPJE023

Consideration on the Future Major Upgrades of the SSRF Storage Ring

storage-ring, injection, emittance, optics

1672

Z.T. Zhao, B.C. Jiang, Y.B. Leng, S.Q. Tian, L. Yin, M.Z. Zhang
SINAP, Shanghai, People's Republic of China

The SSRF storage ring was in operation from 2008, currently it is operating at the energy of 3.5GeV, the natural emittance of 3.9 nm-rad and the beam current of 240 mA, serving for 13 beamlines with 9 IDs. There will be around 40 operated beamlines around 2020, which need some upgrade of the storage ring existing performance, such as the new lattice with superbends. And looking for the future beyond, the major upgrade towards a diffraction limited storage ring is under consideration. This paper presents the initial investigation and the proposal on the ultimate storage ring upgrade for SSRF.

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TUPJE056

VELA Machine Development and Beam Characterisation

cathode, electron, gun, klystron

1752

D.J. Scott, D. Angal-Kalinin, A.D. Brynes, F. Jackson, J.K. Jones, A. Kalinin, S.L. Mathisen, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, L.K. Rudge, E. Sneddon, M. Surman, R. Valizadeh, A.E. Wheelhouse, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S.D. Barrett, C.P. Topping, A. Wolski
The University of Liverpool, Liverpool, United Kingdom
A. Lyapin
JAI, Egham, Surrey, United Kingdom
M.D. Roper
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
C.P. Topping, A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom
E. Yamakawa
Royal Holloway, University of London, Surrey, United Kingdom

Recent developments on the VELA (Versatile Electron Linear Accelerator) RF photo-injector at Daresbury Laboratory are presented. These are three-fold; commissioning/installation, characterising and providing beam to users. Measurements for characterising the dark current (DC), 4-D transverse emittance, lattice functions and photoinjector stability are presented. User beam set ups to provide beam for electron diffraction and Cavity Beam Position Monitor development are summarised.

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TUPJE058

Preparation of Polycrystalline and Thin Film Metal Photocathodes for Normal Conducting RF Guns

cathode, gun, electron, experiment

1759

S. Mistry, M.D. Cropper
Loughborough University, Leicestershre, United Kingdom
A.N. Hannah, K.J. Middleman, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

A comparison of quantum efficiency (QE) and work function (wf) measurements of polycrystalline and thin film metal photocathodes for use in NCRF guns, similar to the S-band gun under development for CLARA project at Daresbury, are reported. Cu and Nb thin films were grown onto a Si substrate by magnetron sputtering and subsequently were prepared by annealing and Ar ion sputtering. To determine the surface chemistry, x-ray photoelectron spectroscopy was employed. QE measurements were enabled using a UV laser source giving 266 nm light. Wf measurements were carried out using a kelvin probe and ultraviolet photoelectron spectroscopy. Annealing the Cu thin film to 250°C yielded a QE of 1.2E-4; one order of magnitude higher than the QE for sputter cleaned and post annealed polycrystalline Cu. The optimum QE measurement for Nb thin film was 2.6·10^-4, which was found to be comparable to the results obtained for cleaned bulk Nb. Analysis of XPS data of these metals suggest surface composition and surface chemistry are main contributing factors to the QE and WF.

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TUPJE060

Development of Advanced Fourth Generation Light Sources for the Accelerator Science Laboratory

radiation, electron, simulation, laser

1765

T. Chanwattana, R. Bartolini, A. Seryi
JAI, Oxford, United Kingdom
R. Bartolini
DLS, Oxfordshire, United Kingdom
E. Tsesmelis
CERN, Geneva, Switzerland

The John Adams Institute for Accelerator Science (JAI) has proposed the realisation of the Accelerator Science Laboratory (ASL) at the University of Oxford as a facility for the development of advanced compact light sources enabling accelerator science research and applications. The installation of a compact light source in the ASL is planned with two options for the accelerating technologies. Firstly, a conventional RF based accelerator is considered to be a driver for a short pulse THz coherent synchrotron radiation (CSR). The other option focusses on the radiation produced by a Laser Plasma Accelerator (LPA) advanced accelerator technique that will provide the possibility to shorten the length of the beamline. This paper presents results of the studies on beam dynamics for both options of compact light sources in the ASL.

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TUPJE076

Design Study of the Higher Harmonic Cavity for Advanced Photon Source Upgrade

operation, impedance, simulation, superconducting-cavity

1819

S.H. Kim, T.G. Berenc, J. Carwardine, G. Decker, M.P. Kelly, P.N. Ostroumov
ANL, Argonne, Illinois, USA

Funding: Results in this report are derived from work performed at Argonne National Laboratory. Argonne is operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357.
A higher-harmonic cavity is planned for the proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice to increase the bunch length, improve the Touschek lifetime and increase the single-bunch current limit. We have investigated a range of options including 3rd, 4th, and 5th harmonics of the main radio frequency (RF) system, as well as configurations with and without external RF power couplers. The current baseline is a single 4th harmonic superconducting cavity with adjustable RF couplers and a slow tuner which provide the flexibility to operate over a wide range of beam currents. The cavity is designed to provide 0.84 MV at 1408 MHz for the nominal 6 GeV, 200 mA electron beam, and 4.1 MV main RF voltage. In this paper, we discuss the harmonic cavity parameters based on analytical calculations of the equilibrium bunch distribution and make comparisons to other options.

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TUPJE080

First Beam and High-Gradient Cryomodule Commissioning Results of the Advanced Superconducting Test Accelerator at Fermilab

cryomodule, dipole, accelerating-gradient, diagnostics

1831

D.J. Crawford, C.M. Baffes, D.R. Broemmelsiek, K. Carlson, B.E. Chase, E. Cullerton, J.S. Diamond, N. Eddy, D.R. Edstrom, E.R. Harms, A. Hocker, C.D. Joe, A.L. Klebaner, M.J. Kucera, J.R. Leibfritz, A.H. Lumpkin, J.N. Makara, S. Nagaitsev, O.A. Nezhevenko, D.J. Nicklaus, L.E. Nobrega, P. Piot, P.S. Prieto, J. Reid, J. Ruan, J.K. Santucci, W.M. Soyars, G. Stancari, D. Sun, R.M. Thurman-Keup, A. Valishev, A. Warner, S.J. Wesseln
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The advanced superconducting test accelerator at Fermilab has accelerated electrons to 20 MeV and, separately, the International Linear Collider (ILC) style 8-cavity cryomodule has achieved the ILC performance milestone of 31.5 MV/m per cavity. When fully completed, the accelerator will consist of a photoinjector, one ILC-type cryomodule, multiple accelerator R&D beamlines, and a downstream beamline to inject 300 MeV electrons into the Integrable Optics Test Accelerator (IOTA). We report on the results of first beam, the achievement of our cryomodule to ILC gradient specifications, and near-term future plans for the facility.

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TUPJE081

Model of Dark Current in SRF Linac

linac, electron, radiation, quadrupole

1834

A.I. Sukhanov, A. Saini, N. Solyak, I.S. Tropin
Fermilab, Batavia, Illinois, USA

Currently, few linacs based on 9-cell TESLA-type SRF cavities are being designed or bult, including XEFL, LCLS-II and ILC. Dark current electron generated by field emission in SRF cavities can be captured and accelerated in the linac up to hundreds MeV before they removed by focusing magnets. Lost dark current electrons interact with the materials surrounding SRF cavities and magnets, produce electromagnetic showers and contribute to the radiation in the linac tunnel. In this paper we present a model of dark current in a linac based on TESLA cavities. We show preliminary results of the simulation applied to ILC main linac.

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TUPMA018

An Improved Analytic Model of Electron Back-Bombardment in Thermionic Cathode RF Guns

simulation, gun, electron, cathode

1872

J.P. Edelen, S. Biedron, J.R. Harris, S.V. Milton
CSU, Fort Collins, Colorado, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

This paper describes work done at Colorado State University to improve upon the recent theory developed to predict the back-bombardment power in single-cell thermionic-cathode electron guns. The previous theory used a square-wave approximation of the time varying field to solve for the total kinetic energy deposited on the cathode due to the back-bombarded electrons. In addition the transit time factor was added as a correction to compensate for the non-sinusoidal field. By solving for the back-bombardment power using a sinusoidal field, the transit time factor can be removed and therefore a better overall model is produced. These alterations continue to accurately predict how back-bombardment varies as a function of the gun parameters and provides improvement when compared to the existing theory.

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TUPMA028

Feasibility Study for an X-ray FEL Oscillator at the LCLS-II

electron, FEL, undulator, laser

1897

T.J. Maxwell, J. Arthur, Y. Ding, W.M. Fawley, J.C. Frisch, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus
SLAC, Menlo Park, California, USA
W.M. Fawley
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
K.-J. Kim, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin
ANL, Argonne, Ilinois, USA

Funding: This work supported in part under US Department of Energy contract DE-AC02-76SF00515.
We show that a free-electron laser oscillator generating X-ray pulses with hard X-ray wavelengths of order 0.1 nm is feasible using the presently proposed FEL-quality electron beam within the space of existing LCLS-II infrastructure when combined with a low-loss X-ray crystal cavity. In an oscillator configuration driven by the 4 GeV energy electron beam lasing at the fifth harmonic, output x-ray bandwidths as small as a few meV are possible. The delivered average spectral flux is at least two orders of magnitude greater than present synchrotron-based sources with highly stable, coherent pulses of duration 1 ps or less for applications in Mössbauer spectroscopy and inelastic x-ray scattering.

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TUPMA047

Multipacting-free Quarter-wavelength Choke Joint Design for BNL SRF

cathode, gun, SRF, electron

1935

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, C.J. Liaw, G.T. McIntyre, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, D. Weiss, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA

The BNL SRF gun cavity was operated well at CW mode up to 2 MV. However, the performance suffered due to multipacting in the quarter-wavelength choke-joint. A new multipacting-free cathode stalk was designed and will be conditioned. This paper will describes RF and thermal design of new cathode stalk and conditioning results.
This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.

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TUPMA048

Experimental and Simulational Result of Multipactors in 112 MHz QWR Injector

gun, electron, cathode, simulation

1938

T. Xin
Stony Brook University, Stony Brook, USA
S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, V. Litvinenko, I. Pinayev, J. Skaritka, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: This work was carried out at Brookhaven Science Associates, LLC under Contracts No. DE-AC02-98CH10886 and at Stony Brook University under grant DE-SC0005713 with the U.S. DOE.
The first RF commissioning of 112 MHz QWR superconducting electron gun was done in late 2014. The coaxial Fundamental Power Coupler (FPC) and Cathode Stalk (stalk) were install and tested for the first time. During this experiment, we observed several multipacting barriers at varied gun voltage levels. The simulation work was done within the same range. The comparison between the experimental observation and the simulation results are presented in this paper. The observations during the test are consisted with the simulation predictions. We were able to overcome most of the multipacting barriers and reach 1.7 MV gun voltage under pulsed mode after several round of conditioning processes.

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TUPMA049

First Beam Commissioning at BNL ERL SRF Gun

cathode, SRF, gun, electron

1941

W. Xu, Z. Altinbas, S.A. Belomestnykh, I. Ben-Zvi, S. Deonarine, D.M. Gassner, H. Hahn, L.R. Hammons, T. Hayes, J.P. Jamilkowski, P. K. Kankiya, D. Kayran, N. Laloudakis, R.F. Lambiase, V. Litvinenko, L. Masi, G.T. McIntyre, K. Mernick, T.A. Miller, G. Narayan, D. Phillips, V. Ptitsyn, T. Rao, T. Seda, F. Severino, B. Sheehy, K.S. Smith, A.N. Steszyn, T.N. Tallerico, R. Than, J.E. Tuozzolo, E. Wang, D. Weiss, M. Wilinski, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, V. Ptitsyn
Stony Brook University, Stony Brook, USA

Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 704 MHz superconducting RF gun successfully generated the first photoemission beam on Nov. 17 2014. This paper will report the latest results of SRF beam commissioning, including the SRF cavity performance, cathode QE measurements, and beam parameter measurements. The beam commissioning setup is described in the paper as well.

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TUPMA052

NSLS-II Radio Frequency Systems

storage-ring, feedback, operation, booster

1947

J. Rose, F. Gao, B. Holub, J.G. Kulpin, C. Marques
BNL, Upton, Long Island, New York, USA
A. Goel
ANL, Argonne, Ilinois, USA
M. Yeddulla
Varian Medical Systems, Inc., Palo Alto, California, USA

Funding: Work supported by DOE contract DE-SC0012704
The National Synchrotron Light Source II is a 3 GeV X-ray user facility commissioned in 2014. The NSLS-II RF system consists of the master oscillator, digital low level RF controllers, linac, booster and storage ring RF sub-systems, as well as a supporting cryogenic system. Here we will report on RF commissioning and early operation experience of the system.

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TUPTY037

HLLHCV1.1 Optics Version for the HL-LHC Upgrade

optics, hardware, luminosity, quadrupole

2090

R. De Maria, S.D. Fartoukh, M. Fitterer
CERN, Geneva, Switzerland

Funding: The HiLumi LHC Design Study is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
The optics and layout of the HL-LHC are evolving as the new hardware is being studied and integrated, any additional requirements from the experiments detailed, and other constraints of different nature clarified. Here we present the changes of version 1.1 of the optics and layout with respect to the previous version 1.0, which include the current hardware choices and an outlook on the main resulting optics limitations and the possible future evolutions of the layout.

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TUPTY055

Optimization of the RF Design of the CLIC Main Linac Accelerating Structure

wakefield, linac, simulation, collider

2150

H. Zha, A. Grudiev
CERN, Geneva, Switzerland

We present a new optimized design of the accelerating structure for the main linac of CLIC (Compact Linear Collider). The new structure has lower surface magnetic fields and a significantly smaller transverse size compared to the baseline design described in the CLIC Concept Design Report (CDR). This new design should reach higher accelerating gradients and have a reduced manufacturing cost. The details of the RF design procedure and the obtained results are presented in this paper.

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TUPTY076

Beam-Beam Simulation of Crab Cavity White Noise for LHC Upgrade

luminosity, simulation, emittance, beam-beam-effects

2206

J. Qiang
LBNL, Berkeley, California, USA
J. Barranco García
EPFL, Lausanne, Switzerland
K. Ohmi
KEK, Ibaraki, Japan
T. Pieloni
CERN, Geneva, Switzerland

High luminosity LHC upgrade will improve the luminosity of the current LHC operation by an order of magnitude. Crab cavity as a critical component for compensating luminosity loss from large crossing angle collision and also providing luminosity leveling for the LHC upgrade is being actively pursued. In this paper, we will report on the study of potential effects of the crab cavity noise on the beam luminosity lifetime based on strong-strong beam-beam simulations.

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TUPTY082

Scanning Synchronization of Colliding Bunches for MEIC Project

ion, controls, electron, collider

2229

Y.S. Derbenev, V.P. Popov
JLab, Newport News, Virginia, USA
Y.D. Chernousov
ICKC, Novosibirsk, Russia
G.M. Kazakevich
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
Synchronization of colliding beams is one of the major issues of an electron-ion collider (EIC) design because of sensitivity of ion revolution frequency to beam energy. A conventional solution for this trouble is insertion of bent chicanes in the arcs space. In our report we consider a method to provide space coincidence of encountering bunches in the crab-crossing orbits Interaction Region (IR) while repetition rates of two beams do not coincide. The method utilizes pair of fast kickers realizing a bypass for the electron bunches as the way to equalize positions of the colliding bunches at the Interaction Point (IP). A dipole-mode warm or SRF cavities fed by the magnetron transmitters are used as fast kickers, allowing a broad-band phase and amplitude control. The proposed scanning synchronization method implies stabilization of luminosity at a maximum via a feedback loop. This synchronization method is evaluated as perspective for the Medium Energy Electron-Ion collider (MEIC) project of JLab with its very high bunch repetition rate.

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TUPWI008

RF Gun Based Ultrafast Electron Microscopy

electron, gun, emittance, cathode

2259

J. Yang, K. Tanimura, Y. Yoshida
ISIR, Osaka, Japan
J. Urakawa
KEK, Ibaraki, Japan

Ultrafast electron microscopy (UEM) would be a powerful tool for the direct visualization of structural dynamic processes in matter. The resolutions of the observation on femtosecond time scales over sub-nanometer (even atomic) spatial dimensions have long been a goal in science. To achieve such resolutions, we have designed and constructed a femtosecond time-resolved relativistic-energy electron microscopy using a photocathode radio-frequency (RF) electron gun (RF based UEM). The RF gun has successfully generated a high-brightness electron beam with bunch length of 100 fs and emittance of 0.2 mm-mrad, which are essential beam parameters for the achievement of nm-fs space-time resolution in the microscopy. Both the static measurements of both relativistic-energy electron diffraction and image have been succeeded. In this presentation, the activities on RF based UEM are introduced. The requirements and limitations of the beam parameters are reviewed. The concept and design of RF based UEM are reported. Finally, some demonstrations of the relativistic-energy UEM images are reported.

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TUPWI034

Capture, Acceleration and Bunching RF Systems for the MEIC Booster and Storage Rings

ion, collider, electron, bunching

2318

S. Wang, J. Guo, F. Lin, V.S. Morozov, R.A. Rimmer, H. Wang, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The MEIC, proposed by Jefferson Lab, consists of a series of accelerators. The electron collider ring accepts electrons from CEBAF at energies from 3 to 12 GeV. Protons and ions are delivered to a booster and captured in a long bunch before ramping and transfer to the ion collider ring. The ion collider ring accelerates a small number of long ion bunches to colliding energy before they are re-bunched into a high frequency train of very short bunches for colliding. Two sets of low frequency RF systems are needed for the long ion bunch energy ramping in the booster and ion collider ring. Another two sets of high frequency RF cavities are needed for re-bunching in the ion collider ring and compensating synchrotron radiation energy loss in the electron collider ring. The requirements from energy ramping, ion beam bunching, electron beam energy compensation, collective effects, beam loading and feedback capability, RF power capability, etc. are presented. The preliminary designs of these RF systems are presented. Concepts for the baseline cavity and RF station configurations are described, as well as some options that may allow more flexible injection and acceleration schemes.

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TUPWI059

Influence of Plasma Loading in a Hybrid Muon Cooling Channel

plasma, ion, electron, emittance

2381

D. Stratakis
BNL, Upton, Long Island, New York, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
K. Yonehara
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In a hybrid 6D cooling channel, cooling is accomplished by reducing the beam momentum through ionization energy loss in wedge absorbers and replenishing the momentum loss in the longitudinal direction with gas-filled rf cavities. While the gas acts as a buffer to prevent rf breakdown, gas ionization may also occur as the beam passes through a HPRF cavity. The resulting plasma, may gain substantial energy from the rf electric field which it can transfer via collisions to the gas, an effect known as plasma loading. In this paper, we investigate the influence of plasma loading on the cooling performance of a rectilinear hybrid channel. With the aid of numerical simulations we examine the sensitivity in cooling performance and plasma loading to key parameters such as the rf gradient and gas pressure.

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WEYC1

Technical Challenges of the LCLS-II

undulator, linac, gun, electron

2434

T.O. Raubenheimer
SLAC, Menlo Park, California, USA

The LCLS-II will be a CW X-ray FEL upgrade to the existing LCLS X-ray FEL at the SLAC National Accelerator Laboratory (SLAC). This paper describes the overall layout and the technical challenges that the upgrade project faces.

Slides WEYC1 [4.446 MB]

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WEYC3

Commissioning and Operation of the ARIEL Electron Linac at TRIUMF

linac, cryomodule, electron, TRIUMF

2444

M. Marchetto, F. Ames, Z.T. Ang, R.A. Baartman, I.V. Bylinskii, Y.-C. Chao, D. Dale, K. Fong, R. Iranmanesh, F.W. Jones, D. Kaltchev, J. Kavarskas, P. Kolb, S.R. Koscielniak, A. Koveshnikov, M.P. Laverty, R.E. Laxdal, L. Merminga, N. Muller, R.R. Nagimov, R.B. Nussbaumer, T. Planche, M. Rowe, S. Saminathan, V.A. Verzilov, Z.Y. Yao, Q. Zheng, V. Zvyagintsev
TRIUMF, Vancouver, Canada

Funding: Funded under a contribution agreement with NRC (National Research Council Canada). Capital funding from CFI (Canada Foundation for Innovation).
ARIEL is the new TRIUMF facility for production of radioactive ion beams that will enable the delivery of three simultaneous RIB beams to the ISAC experimental stations. Two additional target stations will produce beams by using either a 50 kW proton or from 500 kW electrons via photo-fission. The electron beam driver is going to be a 50 MeV 10 mA CW superconducting electron linac. The first stage of the e-linac installation is completed and commissioning is underway. The paper will present the e-linac design characteristics, installation, commissioning strategy and current results.

Slides WEYC3 [13.765 MB]

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WEPWA008

Measuring the Self-modulation Instability of Electron and Positron Bunches in Plasmas

plasma, electron, radiation, positron

2506

P. Muggli, O. Reimann
MPI-P, München, Germany
E. Adli, V.K.B. Olsen
University of Oslo, Oslo, Norway
J. Allen, S.J. Gessner, S.Z. Green, M.J. Hogan, M.D. Litos, B.D. O'Shea, V. Yakimenko
SLAC, Menlo Park, California, USA
L.D. Amorim
IST, Lisboa, Portugal
G. Andonian, C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi, O. Williams
UCLA, Los Angeles, California, USA
N.C. Lopes, L.O. Silva, J. Vieira
Instituto Superior Tecnico, Lisbon, Portugal

The self-modulation instability (SMI) * can be used to transform a long, charged particle bunch into a train of periodically spaced shorter bunches. The SMI occurs in a plasma when the plasma wake period is much shorter than the bunch length. The train of short bunches can then resonantly drive wakefields to much larger amplitude that the long bunch can. The SMI will be used in the AWAKE experiment at CERN, where the wakefields will be driven by a high-energy (400GeV) proton bunch. ** However, most of the SMI physics can be tested with the electron and positron bunches available at SLAC-FACET. *** In this case, the bunch is ~10 plasma wavelengths long, but can drive wakefields in the GV/m range. FACET has a meter-long plasma **** and is well equipped in terms of diagnostic for SMI detection: optical transition radiation for transverse bunch profile measurements, coherent transition radiation interferometry for radial modulation period measurements and energy spectrometer for energy loss and gain measurement of the drive bunch particles. The latest experimental results will be presented.
* N. Kumar et al., PRL 104, 255003 (2010)
** AWAKE Collaboration, PPCF 56 084013 (2014)
*** J. Vieira et al., PoP 19, 063105 (2012)
**** S.Z. Green et al., PPCF 56, 084011 (2014)

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WEPWA014

Low Temperature Properties of 20 K Cooled Test Cavity for C-band 2.6-cell Photocathode RF Gun

experiment, cryogenics, gun, resonance

2519

T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai
LEBRA, Funabashi, Japan
M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan
T.S. Shintomi
Nihon University, Tokyo, Japan

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
A cryogenic C-band 2.6-cell photocathode RF gun, which operates at 20 K, is under development at Nihon University for future possibility of use in a compact linac-driven X-ray source. The cavity material is 6N8 high purity copper, the RRR of which being expected to be higher than 3000. A 2.6-cell pi-mode test cavity was fabricated for investigation of the properties under low temperature of 20 K*. Ultraprecision machining and diffusion bonding of the cavity were carried out in KEK. The operating frequency of the RF gun cavity is 5712 MHz. The machining dimensions of the test cavity were determined by taking into account the contraction of copper from room temperature to 20 K by approximately 0.33 %. The resonant frequency observed at around 21 K was 5711.761 MHz, which is 185 kHz higher than the expected value that was deduced from the resonant frequency obtained at 23.5 degree C in vacuum and the linear expansion coefficient data for OFC copper by NIST**. The unloaded Q-value of 64500 obtained at 21 K is in agreement with the SUPERFISH calculation when the surface resistance of the RRR=3000 copper was specified with taking the anomalous skin effect into account.
* T. Tanaka et al., Proceedings of IPAC2014, 658-660, http://accelconf.web.cern.ch/AccelConf
/IPAC2014/papers/mopri030.pdf
** http://cryogenics.nist.gov/MPropsMAY/OFHC%20Copper/OFHC_Copper_rev.htm

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WEPWA015

RF Input Coupler for 20 K Cooled C-band 2.6-cell Photocathode RF Gun

simulation, gun, resonance, network

2522

T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai
LEBRA, Funabashi, Japan
M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan
T.S. Shintomi
Nihon University, Tokyo, Japan

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
For future use in a compact linac-driven X-ray source, a cryo-cooled C-band photocathode RF gun is under development. The RF experiment on the basic 2.6-cell test cavity has shown that the unloaded Q-value of the cavity at 20 K can be explained by the surface resistance based on the anomalous skin effect. Since the cavity was intended for preliminary experiments of the low temperature RF properties*, a new test cavity with an RF input coupler has been designed. The basic structure of the accelerating cells has not been changed from the previous cavity. Avoiding an element with a low cooling efficiency such as the inner electrode in a coaxial coupler, a simpler cylindrical input coupler has been designed. The coupler consists of a cylindrical TM01 mode waveguide and a mode converter from a rectangular TE10 mode, with both elements placed on the accelerating axis. The structure and the dimensions of the coupler have been determined using the 3-D simulation code CST Studio so that the resonant frequency of the whole system and the coupling coefficient of the coupler meet the specifications of the RF gun. The new test cavity will be completed early in 2015 at KEK.
* T. Tanaka et al., Proceedings of IPAC2014, 658-660, http://accelconf.web.cern.ch/AccelConf
/IPAC2014/papers/mopri030.pdf

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WEPWA023

Development of Muon LINAC for the Muon g-2/EDM Experiment at J-PARC

acceleration, target, rfq, experiment

2541

M. Otani, Y. Fukao, T. Mibe, N. Saito, M. Yoshida
KEK, Tsukuba, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
R. Kitamura
University of Tokyo, Tokyo, Japan
Y. Kondo
JAEA, Ibaraki-ken, Japan

The muon anomalous magnetic moment (g-2) and electric dipole moment (EDM) are one of the effective paths to beyond Standard Model of elementary particle physics. The E34 experiment aims to measure g-2 with a precision of 0.1 ppm and search EDM with a sensitivity to 10-21 e*cm with high intensity proton driver at J-PARC and a newly developed novel technique of the ultra-cold muon beam. The ultra-cold muons, which are generated from surface muons by the thermal muonium production and laser ionization, are accelerated to 300 MeV/c by muon linear accelerator. The muon LINAC consists of RFQ and following three types of the RF cavities. The muon acceleration to this energy will be the first case in the world. This poster reports about status of the initial acceleration test with RFQ and the development of the RF cavities, especially for the middle beta section.

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WEPWA024

Development of a C-band RF Gun with a Coniferous-tree-type Carbon Nanostructure Field Emission Cathode

cathode, gun, electron, radiation

2545

Y. Taira, H. Kato, R. Kuroda, H. Toyokawa
AIST, Tsukuba, Ibaraki, Japan

A C-band RF gun for compact radiation sources such as a high energy x-ray and a terahertz radiation is developed at AIST, which is designed to work at the frequency of 5.3 GHz*. A coniferous-tree-type carbon nanostructure (CCNS) is used for a field emission cathode in the C-band RF gun. A graphene sheet composed of carbon has a coniferous form, and the tip has a nanometer-size tubular structure that becomes thicker on the substrate side**. Owing to this configuration, the CCNS has a large field enhancement factor, and is considered to be more stable in high electric fields than Carbon nanotubes. We have fabricated the C-band RF gun of the single cell cavity. Emission current depending on the electric field strength on the CCNS cathode surface was measured. When the electric field strength was 30 MV/m, the total charge per a macro pulse was 30 nC. After applying a stronger electric field, a decline of the field enhancement factor was observed. We will present the experimental result of the field emission measurement of the CCNS and the simulation result of a beam trajectory using a C-band RF gun of a multi cell cavity.
* Y. Taira et al., Nucl. Instr. and Meth. Phys. Res. B 331 (2014) 27.
** R. Suzuki, Synthesiology 2 (3) (2009) 221.

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WEPWA035

Initial EEX-based Bunch Shaping Experiment Results at the Argonne Wakefield Accelerator Facility

experiment, dipole, simulation, emittance

2575

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
M.E. Conde, D.S. Doran, W. Gai, G. Ha, C.-J. Jing, K.-J. Kim, W. Liu, J.G. Power, Y.-E. Sun, C. Whiteford, E.E. Wisniewski, A. Zholents
ANL, Argonne, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Funding: This work is partly supported by POSTECH BK²¹⁺ and Argonne National Laboratory
A program is under development at Argonne National Laboratory to use an emittance exchange (EEX) beamline to perform longitudinal bunch shaping (LBS). The double dog-leg EEX beamline was recently installed at the Argonne Wakefield Accelerator (AWA) and the goals of the proof-of-principle experiment are to demonstrate LBS and characterize its deformations from the ideal shape due to higher-order and collective effects. The LBS beamline at the AWA consists of insert-able transverse masks mounted on an actuator and four quadrupoles (to manipulate the transverse phase space) before the EEX beamline, which consists of two identical dog-legs and a deflecting cavity. The mask and input beam parameters are varied during the experiment to explore the shaping capability and clarify the deformation sources and their mitigation. Progress on the commissioning of the LBS beamline, initial experimental data and benchmarks to GPT simulations will be presented.

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WEPWA046

Time Domain Simulations of Detuned Accelerating Cavities for Two Beam Applications

simulation, impedance, accelerating-gradient, cathode

2605

R.M. Jones, L.R. Carver
UMAN, Manchester, United Kingdom

A multi-harmonic accelerating cavity that has its fundamental and harmonic mode frequency detuned away from the bunch repetition frequency could provide the basis for a beam driven wakefield accelerator with high transformer ratios. The excitation of multiple harmonic eigenmodes will allow high gradients to be achieved without encouraging the onset of rf breakdown or pulsed surface heating. This accelerating cavity will be introduced, and time domain simulations verifying the theory will be shown.

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WEPWA062

Design and High-Power Testing of a Hybrid Photonic Band-Gap (PBG) Accelerator Structure at 17 GHz

simulation, lattice, coupling, flattop

2646

J.X. Zhang, A.M. Cook, B.J. Munroe, M.A. Shapiro, R.J. Temkin, H. Xu
MIT/PSFC, Cambridge, Massachusetts, USA

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics under Award Number DE-SC0010075.
An overmoded hybrid Photonic Band Gap (HPBG) structure used as an accelerator cavity has been theoretically designed and high power tested at 17.1 GHz. The HPBG structure consists of a triangular lattice of dielectric (sapphire) and metallic (copper) rods. Due to the frequency selectivity, the hybrid PBG cavity can be operated in a TM02 mode. The maximum surface fields are on the triple point of the innermost row of the sapphire rods. The relatively high value of the surface fields resulted in a high breakdown rate (BDR) at a low gradient in the HPBG structure. Breakdown damage on the triple point edge and the metallization of copper onto the sapphire surface have been observed in the post-testing images. An improved HPBG design, that reduces the peak fields, has been developed. It will be built and tested in an effort to improve the HPBG performance.

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WEPWA067

Acoustic Breakdown Localization in RF Cavities

simulation, experiment, timing, diagnostics

2658

P.G. Lane, P. Snopok, Y. Torun
Illinois Institute of Technology, Chicago, Illinois, USA
E. Behnke, I.Y. Levine
Indiana University South Bend, South Bend, USA
D.W. Peterson
Fermilab, Batavia, Illinois, USA

Funding: US Department of Energy
Current designs for muon cooling channels require high-gradient RF cavities to be placed in solenoidal magnetic fields in order to contain muons with large transverse emittances. It has been found that doing so reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields it would be helpful to have a diagnostic tool which can detect breakdown and localize the source of the breakdown inside the cavity. We report here on acoustic simulations and comparisons with experimental acoustic data of breakdown from several RF cavities. Included in this analysis are our most recent results from attempting to localize breakdown using these data.

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WEPMA001

Proposed Linac Upgrade with a SLED Cavity at the Australian Synchrotron, SLSA

klystron, linac, operation, injection

2738

K. Zingre, B. Mountford
ASCo, Clayton, Victoria, Australia
M.P. Atkinson, R.T. Dowd, G. LeBlanc
SLSA, Clayton, Australia
C.G. Hollwich
SPINNER GmbH, Westerham, Germany

The Australian Synchrotron Light Source has been operating successfully since 2007 and in top-up mode since 2012 while gradually being upgraded to reach an excellent beam availability exceeding 99 %. Considering the ageing of the equipment, effort is required in order to maintain the reliability at this level. The proposed upgrade of the linac with a SLED cavity has been chosen to mitigate the risks of single point of failure and lack of spare parts. The linac is normally fed from two independent 35 MW pulsed klystrons to reach 100 MeV beam energy and can be operated in single (SBM) or multi-bunch mode (MBM). The SLED cavity upgrade will allow remote selection of single klystron operation in SMB and possibly limited MBM without degradation of beam energy and reduce down time in case of a klystron failure. The proposal for the SLED cavity upgrade is shown and the linac designs are detailed.

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WEPMA009

3 GHz Single Cell Cavity Optimization Design

accelerating-gradient, linac, simulation, electron

2761

L. Garolfi, M. El Khaldi
LAL, Orsay, France
N. Faure
PMB-ALCEN, PEYNIER, France

In order to develop a high gradient S-band electron accelerating structure, an optimized travelling wave (TW) single-cell cavity operating at the frequency of 3 GHz with 2π/3 phase advance, is proposed. Starting from the well-known accelerating cells design developed by the Laboratoire de l'Accélérateur Linéaire (LAL) and the Stanford Linear Accelerator Centre (SLAC), for linear accelerators; it is possible to improve the main RF parameters, such as quality factor, shunt impedance, enhancement factor and group velocity, by choosing a suitable shape of the inner surface. Even though surface electric field is being considered as the only main quantity limiting the accelerating gradient; the importance of power flow and the modified Poynting vector*, has been highlighted from high-gradient experimental data. In this context, the new field quantity (Sc) is derived from a model describing the RF breakdown trigger phenomenon wherein field emission currents from potential breakdown sites produce local pulsed heating. In particular, the modified Poynting vector takes into account both active and reactive power flow travelling along the structure. The main results presented in this paper have been carried out with the 3D electromagnetic simulation codes: High Frequency Structural Simulator solver (HFSS) and CST MICROWAVE STUDIO (CST MWS).
* A. Grudiev et al., "New local field quantity describing the high gradient limit of accelerating structures", PRST:AB 12, 102001 (2009).

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WEPMA010

First Test Results of the BERLinPro 2-cell Booster Cavities

booster, cryomodule, SRF, linac

2765

A. Burrill, W. Anders, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany
G. Ciovati, W.A. Clemens, P. Kneisel, L. Turlington
JLab, Newport News, Virginia, USA

The BERLinPro Energy Recovery Linac (ERL) is currently being built at Helmholtz-Zentrum Berlin in order to study the physics of operating a high current, a 100 mA, 50 MeV ERL utilizing all SRF cavity technology. This machine will utilize three unique SRF cryomodules for the photoinjector, booster and linac cryomodules respectively. The focus of this paper will be on the cavities contained within the booster cryomodule. Here there will be three 2-cell SRF cavities, based on the original design by Cornell University, but optimized to meet the needs of the project. All of the cavity fabrication, processing and testing was carried out at Jefferson Laboratory where 4 cavities were produced and the 3 cavities with the best RF performance were fitted with helium vessels for installation in the cryomodule. This paper will report on the test results of the cavities as measured in the vertical testing dewar at JLab after fabrication and again after outfitting with the helium vessels.

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WEPMA011

First Horizontal Test Results of the HZB SRF Photoinjector for BERLinPro

SRF, operation, cryomodule, gun

2768

A. Burrill, W. Anders, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany
G. Ciovati, W.A. Clemens, P. Kneisel, L. Turlington
JLab, Newport News, Virginia, USA

The BERLinPro project, a small superconducting RF (SRF) c.w. energy recovery linac (ERL) is being built at Helmholtz-Zentrum Berlin in order to develop the technology required for operation of a high current, 100 mA, 50 MeV ERL. The electron source for the accelerator is a 1.4 cell SRF photoinjector fitted with a multi-alkali photocathode. As part of the HZB photoinjector development program three different SRF photoinjectors will be fabricated and tested. The photoinjector described herein is the second cavity that has been fabricated, and the first photoinjector designed for use with a multi-alkali photocathode. The photoinjector has been built and tested at JLab and subsequently shipped to HZB for testing in the horizontal test cryostat HoBiCaT prior to installation in the photoinjector cryomodule. This cryomodule will be used to measure the photocathode operation in a dedicated experiment called GunLab, the precursor to installation in the BERLinPro hall. This paper will report on the final results of the cavity installed in the helium vessel in the vertical testing dewar at Jefferson Lab as well as the first horizontal test in HoBiCaT

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WEPMA012

High-Q Cavity Operation: Study on the Thermoelectrically Induced Contribution to RF Surface Resistance

simulation, shielding, niobium, operation

2771

J.M. Köszegi, J. Knobloch, O. Kugeler, A. Neumann, A.V. Vélez
HZB, Berlin, Germany

We present a study concerning the operation of a superconducting RF cavity (non-doped niobium) in horizontal testing with the focus on understanding the thermoelectrically induced contribution to the surface resistance. Starting in 2009, we suggested a means of reducing the residual resistance by warming up a cavity after initial cooldown to about 20K and cooling it down again. In subsequent studies we used this technique to manipulate the residual resistance by more than a factor of 2. We postulated that thermocurrents during cooldown generate additional trapped magnetic flux that impacts the cavity quality factor. Since several questions remained open, we present here a more extensive study including measurement of two additional passband modes of the 9-cell cavity that confirms the effect. We also discuss simulations that substantiate the claim. While the layout of the cavity LHe tank system is cylindrically symmetric, we show that the temperature dependence of the material parameters result in a non-symmetric current distribution. Hence a significant amount of magnetic flux can be generated at the RF surface resulting in an increased surface resistance.

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WEPMA013

Hom Damping Optimization Design Studies for BESSY VSR Cavities

damping, HOM, impedance, SRF

2774

A.V. Vélez, H.-W. Glock, J. Knobloch, A. Neumann
HZB, Berlin, Germany

The BESSY VSR project is a future upgrade of the 3rd generation BESSY II light source. By using the same "standard" user optics, simultaneously long (ca. 15ps) and short (ca. 1.5ps) bunches will be stored. Thus, superconducting higher harmonic cavities of the fundamental 500 MHz at two frequencies need to be installed in the BESSY II storage ring. This work describes the optimizations studies for the Waveguide-based HOM dampers and the adjustable fundamental power coupler for the 1.5 GHz first SRF cavity prototype.

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WEPMA016

A New RF station for the ELSA Stretcher Ring

klystron, LLRF, electron, synchrotron

2783

M. Schedler, A. Dieckmann, P. Hänisch, W. Hillert
ELSA, Bonn, Germany

At the Electron Stretcher Facility ELSA of Bonn University, an increase of the maximum stored beam current from 20 mA to 200 mA is planned. The storage ring operates applying a fast energy ramp of 6 GeV/s from 1.2 GeV to 3.2 GeV and afterwards a slow extraction over a few seconds to the hadron physics experiments. The beam current is mainly limited due to missing RF power at highest energies in order to compensate for synchrotron radiation losses. The current stretcher ring's RF station is based on a single 200 kW klystron driving two 5-cell PETRA type cavities. To achieve the desired beam current at maximum energy two additional 7-cell PETRA type cavities, drivin by a second klystron, will be installed. With this upgrade, sufficient beam lifetime for slow beam extraction will be provided and thus ensure an adequate duty cycle of the external beam current. The general setup of the new RF station as well as the changes in operation when switching from one to two stations will be presented.

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WEPMA017

Alvarez DTL Cavity Design for the UNLAC Upgrade

electron, DTL, impedance, simulation

2786

X. Du, L. Groening, S. Mickat
GSI, Darmstadt, Germany
A. Seibel
IAP, Frankfurt am Main, Germany

The 10⁸.4 MHz drift tube linac (DTL) accelerator for GSI’s UNLAC upgrade project is in its initial design stage using CST-MWS code. Optimization criteria for cavity design are effective shunt impedance (ZTT), transit-time factor, and electrical breakdown limit. In geometrical op-timization we have aimed at increase of the energy gain in each RF gap of the DTL cells by maximizing ZTT per peak surface field with special designed tube profile. Mul-ti-pacting probability is evaluated for one gap of typical single cell. For the beta profile design, a code based on VBA macros of CST is developed to perform cell by cell design with pre-optimized 3D tube structures. With this code several beta profile designs are presented and com-pared for the balance of power consumption, ZTT, tank length, and breakdown possibility of the complete cavity. The stability of the field has been taken into account and for this the crossed stem arrangement is assessed. This paper gives a short introduction of the method, presents some important results. Possible countermeas-ures are discussed.

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WEPMA018

Status of the Ring RF Systems for FAIR

operation, antiproton, ion, PLC

2789

M. Frey, R. Balß, C. Christoph, O. Disser, G. Fleischmann, U. Hartel, P. Hülsmann, S. Jatta, A. Klaus, H. Klingbeil, H.G. König, U. Laier, D.E.M. Lens, D. Mondry, K.-P. Ningel, H. Richter, S. Schäfer, C. Thielmann, T. Winnefeld, B. Zipfel
GSI, Darmstadt, Germany
K. Groß, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany

For the FAIR (Facility for Antiproton and Ion Research) synchrotron SIS100 and the storage ring CR (Collector Ring), different RF cavity systems are currently being realized. In addition to the standard RF bucket generation and acceleration, these ring RF systems also allow more complex beam manipulations such as barrier bucket operation or bunch rotation in phase space. Depending on their purpose, the cavities are either loaded with ferrite material or with MA (Magnetic Alloy) ring cores. Independent of the type of cavity, a complete cavity system consists of the cavity itself, a tetrode-based power amplifier, a solid-state pre-amplifier, a supply unit including PLC (Programmable Logic Control), and an RF control system (so-called LLRF, low level RF system). In this contribution, the different systems are described, and their current status is presented.

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WEPMA022

Progress of the Klystron and Cavity Test Stand for the FAIR Proton Linac

klystron, linac, proton, operation

2802

A. Schnase, E. Plechov, J. Salvatore, G. Schreiber, W. Vinzenz
GSI, Darmstadt, Germany
C. Joly, J. Lesrel
IPN, Orsay, France

In collaboration between the FAIR project, GSI, and CNRS, the IPNO lab provided the high power RF components for a cavity and klystron test stand. For initial operation of the 3 MW Thales TH2181 klystron at 325.224 MHz we received a high voltage modulator from CERN Linac 4 as a loan. Here we report, how we integrated the combination of klystron, high voltage modulator, and auxiliaries to accumulate operating experience. RF operation of the klystron started on a water cooled load, soon the circulator will be included and then the prototype CH cavity in the radiation shielded area will be powered. The 45 kW amplifiers for the 3 buncher structures of the FAIR proton Linac were checked at the test stand, and the results are presented here.

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WEPMA026

Higher Order Mode Propagation and Damping Studies on Axisymmetric Superconducting Multicell RF-Resonators

factory, damping, higher-order-mode, coupling

2812

B.D. Isbarn, B. Riemann, M. Sommer, T. Weis
DELTA, Dortmund, Germany

Funding: Work supported by the BMBF under contract no. 05K13PEB
Higher order mode (HOM) propagation and damping is a major concern in feasibility studies regarding the upcoming upgrade of BESSY II, named BESSY-VSR*, which involves the utilization of superconducting multicell RF-resonators in a storage ring while maintaining a reasonably high beam current typical for third generation synchrotron radiation facilities. In addition to the computation of the typical figures of merit, we focus on studies of the mode propagation in axisymmetric structures. Due to the focus on axisymmetric studies we are able to use 2D codes to investigate in eigenmodes with substantial higher frequencies than usually considered with full 3D codes in parametric studies. In this work we present preliminary studies involving mode propagation in superconducting elliptical multicell cavities.
* G. Wüstefeld et al., Proc. of IPAC'11, San Sebastián, THPC014

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WEPMA029

Design of a Normal Conducting Cavity for Arrival Time Stabilization at FLASH

wakefield, coupling, simulation, HOM

2818

M. Fakhari, K. Flöttmann, S. Pfeiffer, H. Schlarb
DESY, Hamburg, Germany
J. Roßbach
Uni HH, Hamburg, Germany

It has been shown, that beam-based feedback loops stabilize the bunch arrival time in the femtoseconds range. However, further minimizing the bunch arrival time jitter requires a faster actuator that is a normal conducting cavity with higher bandwidth compared to narrow-band superconducting cavities. We present the design of a 4-cell normal conducting cavity that is going to be used in a fast beam-based feedback at free-electron laser FLASH at Hamburg. The input power will be injected to the cavity via a loop coupler from the side of the first cell. The operating frequency of the designed cavity is about 3 GHz with an adjustable bandwidth. The long range longitudinal wakefield calculation results are reported to investigate the cavity performance for multi-beam operation up to 3 MHz bunch repetition rate. The results declare that the influence of the long range wakefield on the arrival time jitter is less than 1 fs.

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WEPMA033

Utilizing Gas Filled Cavities for the Generation of an Intense Muon Source

target, proton, cyclotron, emittance

2829

D. Stratakis
BNL, Upton, Long Island, New York, USA
D.V. Neuffer
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
A key requirement for designing intense muon sources is operating rf cavities in multi-tesla magnetic fields. Recently, a proof-of-principle experiment demonstrated that an rf cavity filed with high pressure hydrogen gas could meet this goal. In this study, rigorous simulation is used to design and evaluate the performance of an intense muon source with gas filled cavities. We present a new lattice design and compare our results with conventional schemes. We detail the influence of gas pressure on the muon production rate.

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WEPMA035

Low- and High-Beta SRF Elliptical Cavity Stiffening

simulation, resonance, proton, SRF

2835

E.N. Zaplatin
FZJ, Jülich, Germany
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Elliptical SRF cavities are the main accelerating structures in many accelerators worldwide. Different types of external loads on the resonator walls predetermine the main working conditions of the SC cavities. The most important of them are very high electromagnetic fields that result in strong Lorentz forces and the pressure on cavity walls from the helium tank that also deforms the cavity shape. Also mechanical eigen resonances of cavities are the main source of the microphonics. To withstand any kind of external loads on the resonator walls different schemes of the cavity stiffening were applied. In the paper we report the basic investigations of the cavity stiffening using FNAL 650 MHz β=0.92 and 0.61 as an example. The single-cell investigation results were used as the reference to develop the ultimate scheme of the helium vessel structure to ensure the best resonator stability.

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WEPMA036

Double-Cell Notch Filter for SRF Gun Investigations

gun, cathode, SRF, simulation

2838

E.N. Zaplatin
FZJ, Jülich, Germany
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
J. Knobloch, A. Neumann
HZB, Berlin, Germany
V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Some projects of SRF guns apply the design where the cathode can be easily and quickly removed. One of the disadvantages of this design is the RF power leakage from the accelerating gun cavity cells to the cathode housing that results in the excessive cathode heating. To minimize the RF power leak different kinds of choke filters are used to protect the cathode structure. These choke filters represent resonant circuits with a zero input impedance and installed at the entrance of the cathode structure that shunt the cathode housing. Still, since the choke filter frequency shift under working conditions is bigger than its bandwidth a filter tuning during assembly only in the warm stage seems insufficient and requires also fine-tuning during operation. To eliminate the problems of the choke filter fine-tuning and hence ensure its stability during operation, a combination of the resonance choke elements can be implemented. In the paper we demonstrate advantages of the double-cell notch filter using BERLinPro SRF gun cavity as an example with its simple design modifications.

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WEPMA037

Manufacturing and First Test Results of Euclid SRF Conical Half-wave Resonator

niobium, vacuum, SRF, cryogenics

2841

E.N. Zaplatin
FZJ, Jülich, Germany
C.H. Boulware, T.L. Grimm, A. Rogacki
Niowave, Inc., Lansing, Michigan, USA
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: This Work is supported by the DOE SBIR Program, contract # DE-SC0006302.
Euclid TechLabs has developed a superconducting conical half-wave resonator (162.5 MHz β=v/c=0.11) for the high-intensity proton accelerator complex proposed at Fermi National Accelerator Laboratory. The main objective of this project is to provide a resonator design with high mechanical stability based on an idea of the balancing cavity frequency shifts caused by external loads. A unique cavity side-tuning option has been successfully implemented. Niowave, Inc. proposed a complete cavity production procedure including preparation of technical drawings, processing steps and resonator high-gradient tests. During manufacturing a series of cavity and helium vessel modifications to simplify their manufacturing were proposed. Following standard buffered chemical polish surface treatment and high-pressure rinse, a vertical test was carried out at Niowave’s facilities. Here we present the status of the project and the first high-gradient results.

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WEPMA044

25 Hz, Sub-mJ Ytterbium Laser Source of RF Gun for SuperKEKB Linac

laser, gun, polarization, electron

2862

X. Zhou, T. Natsui, Y. Ogawa, M. Yoshida, R. Zhang
KEK, Ibaraki, Japan

For injector linac of SuperKEKB project, the 5 nC electron beams with double-bunch is expected to be generated in the photocathode RF gun. For the repetition rate of electrum beam, the optional of 2 Hz, 5 Hz, 25 Hz and 50 Hz are requested. Although, more than 5 nC electron with single-bunch has been generated in the 2 Hz and 5 Hz, when the repetition rate increases to 25 Hz, the condition of the laser amplifier system such as the thermal lens effect is changed seriously. To correspond to 25 Hz repetition rate, the ytterbium-doped laser system was reformed. An AuSu (80:20) heat-dissipating solder is employed to reduce the thermal lens effect. Because of the damage threshold limitation of the thin-disk crystal and optical mirrors, Some improvement were performed to increase the quality of the pulses rather than the amplify power, which cause the SHG conversion efficiency is up to 60% and 30% with 2ω and 4ω respectively. More than 3 nC electron beam is obtained with 25 Hz.

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WEPMA046

Studies on Innovative Production methods of HOM Coupler for SRF 9-cell Cavity

HOM, SRF, controls, target

2869

K. Nohara, N. Kawabata, K. Miyajima, M. Shinohara
SPS, Funabashi-shi, Japan
H. Hayano, S. Kato, T. Saeki, A. Yamamoto, M. Yamanaka
KEK, Ibaraki, Japan

Pure Nb as the material of SRF cavity bears hard workability in general. This is why both the inner and outer conductors of HOM coupler for 9-cell cavity have been conventionally produced by full machining, backward extrusion accompanied with annealing and so on. However, in the mass production of 9-cell cavities in ILC, further cost reduction is required. We produced both the inner and outer conductors of HOM coupler for 9-cell cavity in the advanced press forming methods aiming at cost reduction. Press forming of a pure Nb sheet for the outer conductor of HOM coupler was performed with fewer processes free from intermediate annealing and primary machining. For the inner conductor of HOM coupler, water jet cutting and press cold-forging of a plate was performed. The above advanced press forming methods showed favored results, leading to a possibility of simple mass-production of components and cost reduction. The vertical test on a 9-cell cavity with the press formed HOM couplers achieved 36 MV/m that is beyond ILC qualification. The R＆D works are ongoing for further improvement.

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WEPMA048

Development for Mass Production of Superconducting Cavity by MHI

cryomodule, niobium, superconducting-RF, linac

2876

T. Yanagisawa, H. Hara, K. Kanaoka, K. Okihira, K. Sennyu
MHI, Hiroshima, Japan

Mitsubishi Heavy Industries (MHI) have developed manufacturing process of superconducting cavitis for a long time. In this presentation, recent progress will be reported.

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WEPMA052

Low Level RF Systems for J-PARC Linac 50-mA Operation

rfq, linac, operation, controls

2889

Z. Fang, Y. Fukui, K. Futatsukawa, T. Kobayashi, S. Michizono
KEK, Ibaraki, Japan
E. Chishiro, F. Sato, S. Shinozaki
JAEA/J-PARC, Tokai-mura, Japan

In the summer of 2014, lots of improvements were carried out in the J-PARC proton linac, including the ion source, the Radio Frequency Quadrupole linac (RFQ), and the medium-energy beam-transport line from the RFQ to the Drift Tube Linac (DTL) called as MEBT1. The output beam current of the ion source was upgraded from 20 to 50 mA. The previous RFQ with two RF power input ports was replaced by a newly developed RFQ with one input port. The RF power of the solid state amplifier for the rf cavities used in the MEBT1 section were upgraded; from 10 to 30 kW for both of the Buncher-1 and Buncher-2, and from 30 to 120 kW for the Chopper cavity. The old scraper used as dump of chopped beam after the Chopper cavity was also replaced by a new dump system using two scrapers; A new function of separating the chopped beam automatically to the two scrapers was developed by modifying the FPAG control program in the low level control systems. After those improvements, in the September 2014 the J-PARC linac was successfully upgraded for 50-mA beam operation. The details of the improvments, especially for the low level RF systems, will be reported in this paper.

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WEPMA053

Multipactor Simulations in 325 MHz Superconducting Spoke Cavity for an Electron Accelerator

electron, simulation, multipactoring, laser

2892

T. Kubo, T. Saeki
KEK, Ibaraki, Japan
E. Cenni, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
R. Hajima, M. Sawamura
JAEA, Ibaraki-ken, Japan

Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
In order to realize a compact industrial-use X-ray source with the laser-Compton scattering, a 325MHz superconducting spoke cavity for an electron accelerator operated at 4K is under development. After design-optimizations of the first cavity, we started fabrication process. In this paper, multipactor analyses carried out as parts of the design-optimization efforts are briefly summarized. Relations between cavity geometries and averaged secondary electron emission yield are discussed.

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WEPMA054

A Disturbance-Observer-based Controller for LLRF Systems

controls, LLRF, beam-loading, experiment

2895

F. Qiu, D.A. Arakawa, Y. Honda, H. Katagiri, T. Matsumoto, S. Michizono, T. Miura, T. Obina
KEK, Ibaraki, Japan
S.B. Wibowo
Sokendai, Ibaraki, Japan

Digital low-level radio frequency (LLRFs) systems have been developed and evaluated in the compact energy recovery linac (cERL) at KEK. The required RF stabilities are 0.1% rms in amplitude and 0.1° rms in phase. These requirements are satisfied by applying digital LLRF systems. To further enhance the control system and make it robust to disturbances such as large power supply (PS) ripples and high-intensity beams, we have designed and developed a disturbance observer (DOB)-based control method. This method utilizes the RF system model, which can be acquired using modern system identification methods. Experiments show that the proposed DOB-based controller is more effective in the presence of high disturbances compared with the conventional proportional and integral (PI) controller. In this paper, we present the preliminary results based on the experiments with DOB-based controller.

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WEPMA056

Development of Superconducting Spoke Cavities for Laser Compton Scattered X-ray Sources

electron, operation, linac, brightness

2902

R. Hajima, M. Sawamura
JAEA, Ibaraki-ken, Japan
E. Cenni, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
T. Kubo, T. Saeki
KEK, Ibaraki, Japan

Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan.
A 5-year research program on the development of superconducting spoke cavities for electron accelerators has been funded by MEXT, Japan since 2013. The purpose of our program is establishing design and fabrication processes of superconducting spoke cavity optimized for compact X-ray sources based on laser Compton scattering. The spoke cavity is expected to realize a compact industrial-use X-ray source with a reasonable cost and easy operation. We have chosen a cavity frequency at 325 MHz due to possible operation at 4 K and carried out cavity shape optimization in terms of electromagnetic and mechanical properties. Production of press-forming dies is also in progress. In this paper, we present overview and up-to-date status of the research program.

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WEPMA060

The Development of Cavity Frequency Tracking Type RF Control System for SRF-TEM

SRF, LLRF, acceleration, electron

2914

N. Higashi
The University of Tokyo, Graduate School of Science, Tokyo, Japan
A. Enomoto, Y. Funahashi, T. Furuya, X.J. Jin, Y. Kamiya, S. Michizono, M. Nishiwaki, H. Sakai, M. Sawabe, K. Ueno, M. Yamamoto
KEK, Ibaraki, Japan
M. Kuriki
HU/AdSM, Higashi-Hiroshima, Japan
S. Yamashita
ICEPP, Tokyo, Japan

Superconducting accelerating cavities used in high-energy accelerators can generate high electric fields of several 10 MV/m by supplying radio frequency waves (RF) with frequencies matched with resonant frequencies of the cavities. Generally, frequencies of input RFs are fixed, and resonant frequencies of cavities that are fluctuated by Lorentz force detuning and Microphonics are corrected by feedbacks of cavity frequency tuners and input RF power. Now, we aim to develop the cavity frequency tracking type RF control system where the frequency of input RF is not fixed and consistently modulated to match the varying resonant frequency of the cavity. In KEK (Tsukuba, Japan), we are developing SRF-TEM that is a new type of transmission electron microscope using special-shaped superconducting cavity. By applying our new RF control system to the SRF-TEM, it is expected to obtain stable accelerating fields so that we can acquire good spatial resolution. In this presentation, we will explain the required stabilities of accelerating fields for SRF-TEM and the feasibility of SRF-TEM in the case of applying the cavity frequency tracking type RF control system.

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WEPMN010

Analysis of the Electromagnetic Field in the Coupler of Normal Temperature Travelling-Wave Accelerating Tube

coupling, electromagnetic-fields, emittance, simulation

2934

X. He, M. Hou
IHEP, Beijing, People's Republic of China
S. Shu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

With the developed requirement of the beam quality in modern accelerators, rapid development of all kinds of accelerating structures with different frequencies and materials have been achieved. However, the normal temperature travelling-wave (TW) accelerating structures which are widely used in Free Electron Laser (FEL) are still indispensable. For reducing the beam emittance, it is very important to optimize the symmetry of the high-order electromagnetic field in the coupler of such accelerating structures. In this paper, the symmetry of the electromagnetic field in TW accelerator couplers using different coupling mechanisms was analysed. A lot of design optimization as well as the result analysis work has been done for the three kinds of commonly used waveguide-coupled TW accelerating structures: single-feed electrical-coupling, dual-feed electrical-coupling using magic tee in feeding waveguide and dual-feed magnetic-coupling using J-type feeding waveguide. Finally, basing on lots of simulation results and the performances during the fabrication, measurement and RF conditioning of these three kinds of structures, the J-type racetrack coupler type is regarded as the best choice.

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WEPMN011

RF Modulation Studies on the S-Band Pulse Compressor

coupling, flattop, klystron, simulation

2937

S. Shu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
F. Zhao
IHEP, Beijing, People's Republic of China

An S band SLED-type pulse compressor has been manufactured by IHEP to challenge the 100 MW maximum input power, which means the peak power around the coupling irises is about 500 MW at the phase reversal time. In order to deal with the breakdown problem, the dual side-wall coupling irises model was used. To further improve the reliability at very high power, RF phase modulation (PM) with flat-top output is considered. By using the CST Microwave Studio (MWS) transient solver, a new method was developed to simulate the time response of the pulse compressor. In addition, the theoretical and experimental results of the PM theory are also presented in this paper.

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WEPMN012

Cathode Stalk Optimization for a 325 MHz Superconducting QWR Electron Gun

cathode, gun, electron, impedance

2940

P.L. Fan, Y.M. Li, L. Lin, K.X. Liu, S.W. Quan, F. Zhu
PKU, Beijing, People's Republic of China

Funding: Work supported by National Basic Research Project (No. 2011CB808302)
The structure of cathode stalk is very important for the performance of a superconducting QWR (Quarter Wave Resonator) gun. With improper design, RF power dissipation on the surface of cathode stalk and its surrounding tube can lead to a serious decrease of quality factor for superconducting QWR injector. We present here an optimized design of the cathode stalk for the 325 MHz superconducting QWR gun and special considerations are taken to minimize the power dissipation. The details of microwave simulation, beam dynamic simulation of the cavity with cathode stalks in different length, diameter and position are presented in this paper.

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WEPMN013

Development of DC-SRF Injector at Peking University

SRF, laser, electron, cathode

2944

J.K. Hao, J.E. Chen, P.L. Fan, L.W. Feng, S. Huang, L. Lin, K.X. Liu, S.W. Quan, F. Wang, Zh.W. Wang, X.D. Wen, H.M. Xie, K. Zhao, F. Zhu
PKU, Beijing, People's Republic of China

DC-SRF electron injector, which combines a DC Pierce gun and a 3.5 cell 1.3 GHz superconductor cavity in a cryomodule, has been developed at Peking University. Based on the improvements of beam line, LLRF system and 2K cryogenic system, stable operation of the DC-SRF injector has been carried out recently. Electron beams with 3.4 MeV energy and the currents of ~1mA in a macro-pulse mode was obtained. As the first application of this DC-SRF injector, THz radiation produced with a 10 period undulator was also detected. The description of the experiment process and results will be presented in this paper.

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WEPMN014

A C-band Deflecting Cavity Design for High-precision Bunch Length Measurement

simulation, electron, electromagnetic-fields, coupling

2948

J. Jiang, H.B. Chen, J. Shi, P. Wang
TUB, Beijing, People's Republic of China

Funding: NSFC 11375098 and 11327902
A standing wave RF deflecting structure has been designed as a tool for high-precision bunch length measurement. This 3-cell deflecting cavity is designed to operate at a frequency of 5.712GHz. In this paper, the RF design and thermal analysis of the deflecting cavity are introduced. We study the electromagnetic field distribution inside the cavity. The coupler design is also discussed. And the beam dynamics simulation is shown.

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WEPMN024

Exploration of Multi-fold Symmetry Element-loaded Superconducting Radio Frequency Structure for Reliable Acceleration of Low- & Medium-Beta Ion Species

acceleration, SRF, RF-structure, ion

2978

S.C. Huang
IMP/CAS, Lanzhou, People's Republic of China
R.L. Geng
JLab, Newport News, Virginia, USA

Reliable acceleration of low- to medium-beta proton or heavy ion species is needed for future high current superconducting radio frequency accelerators. Due to the high-Q nature of a superconducting RF resonator, it is sensitive to many factors such as loading variation (from either the accelerated beam or from parasitic field emitted electrons), mechanical vibration, and liquid helium bath pressure fluctuation etc. To increase the stability against those factors, a mechanically strong and stable RF structure is desirable. Guided by this consideration, multi-fold symmetry element-loaded superconducting radio frequency structures, cylindrical tanks with multiple (n>=3) rod-shaped radial elements, are being explored. The top goal of its optimization is to improve mechanical stability. A natural consequence of this structure is a lowered ratio of the peak surface electromagnetic field to the acceleration gradient as compared to the traditional spoke cavity. A disadvantage of this new structure is an increased size for a fixed resonant frequency and optimal beta. This paper describes the optimization of EM design and preliminary mechanical analysis for such structures.

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WEPMN025

Harmonic Resonant Kicker Design for the MEIC Electron Circular Cooler Ring

electron, impedance, kicker, ion

2981

Y.L. Huang
IMP/CAS, Lanzhou, People's Republic of China
R.A. Rimmer, H. Wang, S. Wang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S.DOE Contract No. DE-AC05-06OR23177.
Bunched-beam electron cooling of the high-energy ion beam emittance may be a crucial technology for the proposed Medium energy Electron Ion Collider (MEIC) to achieve its design luminosity. A critical component is a fast kicker system in the Circular Ring (CR) that periodically switches electron bunches in and out of the ring from and to the driver Energy Recovery Linac (ERL). Compared to a conventional strip-line type kicker, a quarter wave resonator (QWR) based deflecting structure has a much higher shunt impedance and so requires much less RF power. The cavity has been designed to resonate simultaneously at many harmonic modes that are integer multiples of the fundamental mode. In this way the resulting waveform will kick only a subset of the circulating bunches. In this paper, analytical shunt impedance optimization, the electromagnetic simulations of this type of cavity, as well as tuner and coupler concept designs to produce 5 odd and 5 even harmonics of 47.63MHz will be presented, in order to kick every 10th bunch in a 476.3 MHz bunch train.

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WEPMN026

Development of Non-resonant Perturbing Method for Tuning Traveling Wave Deflecting Structures

simulation, network, higher-order-mode, dipole

2985

J.H. Tan, W. Fang, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
D.C. Tong
TUB, Beijing, People's Republic of China

For traveling wave accelerating structures, the tuning method assisted by bead pull technique based on non-resonant perturbation field distribution measurement has been widely used. Long periodic traveling wave deflecting structure, which operating at HEM11 mode, is difficult to use non-resonant perturbation method, and a improved method has been developed for measuring and tuning by "cage" type perturbing object at SINAP. The measurements on x-band traveling wave deflecting structure are presented in this paper.

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WEPMN030

Testing Procedures for Fast Frequency Tuners of XFEL Cavities

controls, LLRF, operation, cryomodule

2991

K.P. Przygoda, W. Cichalewski, T. Pożniak
TUL-DMCS, Łódź, Poland
J. Branlard, O. Hensler, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
K. Kasprzak
IFJ-PAN, Kraków, Poland

The XFEL accelerator will be equipped with 100 accelerating modules. Each accelerating module will host 8 superconducting cavities. Every single cavity will be equipped with a mechanical tuner. Coarse tuning will be supported by a step motor; fine tuning will be handled by double piezoelectric elements installed inside a single mechanical support, providing actuator and sensor functionality or redundancy. Before the main linac installation, all its subcomponents need to be tested and verified. The AMTF (Accelerator Module Test Facility) has been built at DESY to test all XFEL cryomodules. In total 1600 piezos need to be tested. Test procedures for fast frequency tuners have been developed to check their basic performance in cryogenic conditions (tuning range, polarity, acting and sensing abilities). High level applications perform fully automated tests including report generation. After the successful completion of the acceptance tests, the cryomodules will be prepared for tunnel installation.

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WEPMN031

Automated Quench Limit Test Procedure for Serial Production of XFEL RF Cavities

software, cryomodule, flattop, operation

2994

K. Kasprzak, D. Konwisorz, K. Krzysik, S. Myalski, J. Świerbleski, K. Turaj, M. Wiencek, A. Zwozniak
IFJ-PAN, Kraków, Poland
D. Kostin, K.P. Przygoda
DESY, Hamburg, Germany

In the Accelerator Module Test Facility (AMTF) at DESY in Hamburg RF cavities and accelerating cryomodules are tested for the European X-ray Free Electron Laser (XFEL). Measurements are done by a team of physicists, engineers and technicians from The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences in Kraków, Poland, as a part of Polish in-kind contribution to the XFEL. The testing procedures providing information about maximum available gradient and heat loads measurement are performed for the high gradients (up to 31MV/m). During these tests the cavity deformation caused by the Lorentz force is compensated by piezo (fast) tuners. For this purpose automated high level software was developed. This paper describes a method used to tune automatically the cavities during the RF tests. It was validated with the XFEL cryomodules. This improvement was implemented into the testing software and it is successfully used for testing of serial production cavities.

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WEPMN032

Microphonic Disturbances Prediction and Compensation in Pulsed Superconducting Accelerators

controls, linac, operation, flattop

2997

R. Rybaniec, L.J. Opalski
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
V. Ayvazyan, L. Butkowski, S. Pfeiffer, K.P. Przygoda, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany

Accelerators are affected by the cavities detuning variation caused by external mechanical disturbances (microphonics). The paper presents microphonics estimation and prediction methods applicable for superconducting accelerators operating in pulsed mode. A mathematical model is built using the estimates of detuning during previous RF pulses. The model can be used for predictions of disturbances for the future time step and setup of the fast tuners accordingly. The proposed method was successfully verified with measurements conducted at the FLASH linac.

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WEPMN033

The Fabrication of Prototype Normal Conducting Rebuncher for the MEBT in RISP

resonance, linac, controls, operation

3000

H.J. Kim, M.O. Hyun, B.-S. Park
IBS, Daejeon, Republic of Korea

The Medium Energy Beam Transport (MEBT) system of RAON consists of several quadrupole magnets for controlling the transverse beam parameter at the entrance of the low energy linac, three normal-conducting (NC) re-bunchers to match the longitudinal beam ellipse into the acceptance of the low energy linac and several diagnostic devices. The NC QWR re-buncher, which has a frequency of 81.25 MHz, a geometric beta factor of 0.032, and an effective length of 24 cm, has been fabricated and tested to demonstrate the frequency tuning by using slug tuner, power transmission and reflection with low input power, and pulsed high power transmission with cooling channels. In this presentation, we show the design and fabrication criteria for the high power, ~ 10 kW, re-buncher and its test results.

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WEPMN034

Electron Emission from Surface Roughness on Cavity in Low Temperature

electron, radiation, gun, vacuum

3003

H. Kim, H.J. Cha, S. Choi, W.K. Kim, G.-T. Park
IBS, Daejeon, Republic of Korea
Y. Chang
Hanshin University, Kyungki, Republic of Korea

Electron emission phenomenon from surface roughness on cavity is investigated. The distribution of the electric field from the surface roughness can be obtained on cavity surface. The field emission is calculated from the electric field distribution. The generalized electron emission from electric field and temperature effect is also calculated on the surface roughness of the cavity.

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WEPMN035

QWR and HWR Cryomodules for Heavy Ion Accelerator RAON

cryomodule, alignment, vacuum, radiation

3006

W.K. Kim, H.J. Cha, H. Kim, H.J. Kim, Y. Kim, M. Lee, G.-T. Park
IBS, Daejeon, Republic of Korea

The accelerator called RAON has five kinds of cryomodules such as QWR, HWR1, HWR2, SSR1 and SSR2. The QWR and HWR1 cryomodules are designed and fabricated. The cryomodules will be operated at 2 K and 4 K in order to operate the superconducting cavities. The static heat load of the system was analytically computed for each configuration. The functional requirement of the cryomodules and the static heat load measurement of the QWR and HWR1 cryomodules are presented in this research.

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WEPMN039

RF Accelerating Voltage of PLS-II Superconducting RF System for Stable Top-up Operation with Beam Current of 400 mA

vacuum, operation, LLRF, injection

3015

Y.D. Joo, M.-H. Chun, T. Ha, I. Hwang, B.-J. Lee, I.S. Park, S. Shin, Y.U. Sohn, I.H. Yu
PAL, Pohang, Kyungbuk, Republic of Korea

During the beam store test up to 400 mA in the storage ring, it was observed that the vacuum pressure around the RF window of the superconducting cavity rapidly increases over the interlock level limiting the availability of the maximum beam current storing. We investigated the cause of the window vacuum pressure increment by studying the changes in the electric field distribution at the superconducting cavity and waveguide according to the beam current. An equivalent physical modeling was developed using a finite-difference time-domain (FDTD) simulation and it revealed that the electric field amplitude at the RF window is exponentially increased as the beam current increases, thus this high electric field amplitude causes a RF breakdown at the RF window.

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WEPMN042

400 mA Beam Store with Superconducting RF Cavities at PLS-II

vacuum, SRF, operation, cryomodule

3021

Y.U. Sohn, M.-H. Chun, T. Ha, M.S. Hong, Y.D. Joo, H.-S. Kang, H.-G. Kim, K.R. Kim, T.-Y. Lee, C.D. Park, H.J. Park, I.S. Park, S. Shin, I.H. Yu, J.C. Yun
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: Minister of Science, ICT and Future Planning
Three superconducting RF cavities were commissioned with electron beam in way of one by one during the last 3 years, and now PLS-II is in user service on the way of beam current to 400mA, the target of PLS-II. The cavities and cryomodules were prepared with SRF standard technology and procedures, then vertical test, windows conditioning, cryogenic test in each cryomodule, horizontal power test, conditioning, and commissioning without and with beam at PLS-II tunnel by collaboration with industries. All the cavities showed stable performances as good as not-observing any RF instability from cavities, couplers and windows up to 400 mA beam store, but observing several cavity quenches and minor vacuum bursts by abrupt power with control and human errors. The initial beam current for user run were recorded as 150 mA with one cavity, 280 mA with two cavities and 320 mA with three cavities. The 400 mA beam was also achieved with two cavities by decay mode and also with three cavities by top-up mode. The stabilities of RF amplitude and phase are good enough not to induce beam instabilities.

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WEPMN043

The RF Stability of PLS-II Storage Ring RF System

controls, LLRF, EPICS, storage-ring

3024

I.H. Yu, M.-H. Chun, M.H. Jeong, Y.D. Joo, H.-S. Kang, H.-G. Kim, H.J. Park, I.S. Park, Y.U. Sohn
PAL, Pohang, Kyungbuk, Republic of Korea
Y.S. Lee
SKKU, Suwon, Republic of Korea

Funding: Minister of Science, ICT and Future Planing
The RF system for the Pohang Light Source (PLS) storage ring was greatly upgraded for PLS-II project of 400mA, 3.0GeV from 200mA, 2.5GeV. Three superconducting RF cavities with each 300kW maximum klystron amplifier were commissioned with electron beam in way of one by one during the last 3 years for beam current of 400mA to until March 2014. The RF system is designed to provide stable beam through precise RF phase and amplitude requirements to be less than 0.3% in amplitude and 0.3° in phase deviations. This paper describes the RF system configuration, design details and test results.

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WEPMN045

IOT Use as a Power Source for a Linear Accelerating Structure

coupling, klystron, proton, simulation

3027

E.A. Savin, S.V. Matsievskiy, N.P. Sobenin, I.D. Sokolov
MEPhI, Moscow, Russia
A.A. Zavadtsev
Nano, Moscow, Russia

Nowadays the interest of using compact and high efficiency power sources called Inductive Output Tubes (IOT) [1] for feeding accelerating structures with the required pulsed power around 1MW is increasing. In this article results of the beam dynamics and geometry calculations for the L-band IOT S-band IOT and accelerator-generator hybrid module are presented. Different concepts of the cavity have been proposed, but the most efficient has been chosen. The layout of the generator cell with biperiodic bunсher cells has been investigated. The hybrid structure composed from the generator cell and the compact SW accelerating section is proposed.
IOT, linear accelerator, power supply, klystrons

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WEPMN046

Compassion of Higher Order Modes Damping Techniques for Superconducting 9-Cell Structure

HOM, damping, quadrupole, dipole

3030

Ya.V. Shashkov, A.A. Mitrofanov, N.P. Sobenin
MEPhI, Moscow, Russia
V. Zvyagintsev
TRIUMF, Vancouver, Canada

Funding: Work supported by Ministry of Education and Science grant 3.245.2014/r
Modern types of accelerators, such as Energy recovery linacs, require low values of higher order modes (HOM) Qext. In accelerators with high current HOM could lead to high losses for the modes excitation, beam instability and beam break up. HOM couplers and waveguides are often used in such structures for HOM damping. Unfortunately they could lead to a violation of the axial symmetry of the accelerating field and negatively affect the beam emittance. Also these devices are subject for multipactor discharge and could be difficult in maintaining and fabrication. In this paper we examine several ways of HOM damping with ridged, fluted and corrugated drift tubes which are devoid of the above-mentioned drawbacks. The influence of the parameters of the drift tube on the HOM damping and on the parameters of the fundamental wave were analyzed.
Higher order modes, ERL, SRF

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WEPMN047

Suppression of Higher Order Modes in an Array of Cavities Using Waveguides

HOM, damping, impedance, wakefield

3033

Ya.V. Shashkov, N.P. Sobenin
MEPhI, Moscow, Russia
M. Zobov
INFN/LNF, Frascati (Roma), Italy

Funding: Work is supported by Ministry of Education and Science grant 3.245.2014/r и and by the EU FP7 HiLumi LHC - Grant Agreement 284404
In the frameworks of the High Luminosity LHC upgrade program an application of additional harmonic cavities operating at multiplies of the main RF system frequency of 400 MHz is currently under discussion. A structure consisting of two 800 MHz single cell superconducting cavities with grooved beam pipes coupled by drift tubes has been suggested for implementation. However, it is desirable to increase the number of single cells installed in one cryomodule in order to decrease the number of transitions between “warm” and “cold” parts of the collider vacuum chamber. Unfortunately it can lead to the appearance of higher order modes (HOM) trapped between the cavities. In order to solve this problem the methods of HOM damping with rectangular waveguides connected to the drift tubes were investigated and compared. In this paper we describe the results obtained for arrays of 2, 4 and 8 cavities.

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WEPMN049

Calibration of the Acceleration Voltage of Six Normal Conducting Cavities at ALBA

synchrotron, operation, coupling, pick-up

3036

B. Bravo, U. Iriso, J. Marcos, J.R. Ocampo, F. Pérez, A. Salom, P. Solans
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

ALBA is a 3Gev synchrotron light source located in Barcelona and operating with users since May 2012. The ALBA storage ring uses six room temperature cavities; each one fed by two 80kW IOTs amplifiers at 499.654 MHz. An accurate calibration of the RF voltage is required for the right adjustment of the beam synchronous phase. In addition, if the ring accommodates several RF cavities, these may not be optimally phased with respect to each other, complicating the calculation of the total RF voltage. In this paper, the steps to calibrate the accelerating voltage of the SR cavities will be presented and different methodologies to cross-check these calibrations.

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WEPMN052

A New RF Laboratory for Developing Accelerator Cavities at the University of Huelva

ion, heavy-ion, rfq, network

3046

I. Martel, C. Bonțoiu, J.A. Dueñas, D. Gordo-Yáñez, A.K. Orduz, J. Sanchez-Segovia
University of Huelva, Huelva, Spain

The University of Huelva is presently involved in R&D projects for developing RF accelerator cavities. Two types of cavities are presently under design, a prototype of room temperature RFQ injector and a quarter-wave resonator for high intensity heavy-ion linear accelerators. The laboratory is equipped with dedicated test-bench for RF measurements, which includes high-power RF generators, network analyzer, amplifiers and power meters. A clean room is also available having a dedicated space for high-precision mechanical metrology and cavity mounting, together with a vertical cryostat for superconducting cavity test.

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WEPMN056

High Power Testing of the First Re-buncher Cavity for LIPAC

vacuum, electron, radiation, low-level-rf

3051

F. Toral, D. Gavela, I. Podadera, D. Regidor, M. Weber, C. de la Morena
CIEMAT, Madrid, Spain
B. Bravo, R. Fos, J.R. Ocampo, F. Pérez, A. Salom, P. Solans
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

Funding: This work is partially supported by the Spanish Ministry of Economy and Competitiveness under projects AIC-A-2011-0654 and the Agreement as published in BOE, 16/01/2013, page 1988
Two re-buncher cavities will be installed at the Medium Energy Beam Transport (MEBT) of the LIPAc accelerator, presently being built at Rokkasho (Japan). They are IH-type cavities with 5 gaps and will provide an effective voltage of 350 kV at 175 MHz for deuterons at 5 MeV. The first prototype has been designed at CIEMAT and built by the Spanish industry. The high power tests and RF conditioning have been successfully performed at the ALBA/CELLS RF laboratory. A solid state power amplifier, which has been developed by CIEMAT and its partner companies at Spain for the LIPAc RF System, has been used for the tests. The cavity has shown a performance according to calculations, regarding the dissipated power, peak temperatures and coupling factor. RF conditioning was started with a duty cycle of 3%, which was increased gradually till continuous wave (CW), which is the nominal working mode in LIPAc.

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WEPMN057

Calculation and Design of a RF Cavity for a Novel Compact Superconducting Cyclotron for Radioisotope Production

cyclotron, focusing, simulation, ion

3055

D. Gavela, J. Calero, L. García-Tabarés, A. Guirao, D. Obradors-Campos, C. Oliver, J.M. Pérez Morales, I. Podadera, F. Toral
CIEMAT, Madrid, Spain

Funding: Work partially funded by CDTI and the Spanish Ministry of Economy and Competitiveness, under the subprogram CENIT, project AMIT, reference CEN-20101014
The AMIT cyclotron will be a 8.5 MeV, 10 microAmp, CW, H⁻ accelerator for the purpose of radioisotope production. It includes a superconducting, weak focusing, 4 T magnet, which allows for a low extraction radius and a compact design. The RF cavity design has to deal with challenging requirements: high electric fields created by the required accelerating voltage (60 kV – 70 kV) on a small gap, a small aperture of the magnet leading to high capacitances and thermal losses, and a requirement for a low overall size of the cavity. A quarter wave resonator with one dee (two acceleration gaps) design was chosen. Calculations with HFSS have been performed to compute the resonant frequency, tuners sensitivity, S-parameters, power losses and geometry for input coupler and pickup. A structural Ansys model has been used to analyze the stresses and the deformations of the cavity. A thermal Ansys model was used for the design of the cooling circuits and the calculation of the temperature distribution. Finally, the fluid dynamics of the cooling circuits have been carefully studied. The results of these calculations and the consequent design decisions are presented in this paper.

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WEPMN065

Progress at the FREIA Laboratory

linac, controls, cryogenics, EPICS

3072

M. Olvegård, A.K. Bhattacharyya, T.J.C. Ekelöf, J. Eriksson, K. Fransson, K.J. Gajewski, V.A. Goryashko, L. Hermansson, M. Holz, M. Jacewicz, M. Jobs, Å. Jönsson, H. Li, T. Lofnes, H. Nicander, R.J.M.Y. Ruber, R. Santiago Kern, R. Wedberg, V.G. Ziemann
Uppsala University, Uppsala, Sweden
D.S. Dancila, A. Rydberg
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
R.A. Yogi
ESS, Lund, Sweden

The FREIA Facility for Research Instrumentation and Accelerator Development at Uppsala University, Sweden, has reached the stage where the testing of superconducting cavities for the European Spallation Source (ESS) is starting. The new helium liquefaction plant has been commissioned and now supplies a custom-made, versatile horizontal cryostat, HNOSS, with liquid helium at up to 140 l/h. The cryostat has been designed and built to house up to two accelerating cavities, or, later on, other superconducting equipment such as magnets or crab cavities. A prototype cavity for the spoke section of the ESS linac will arrive mid 2015 for high-power testing in the horizontal cryostat. Two tetrode-based commercial RF power stations will deliver 400 kW peak power each, at 352 MHz, to the cavity through an RF distribution line developed at FREIA. In addition, significant progress has been made with in-house development of solid state amplifier modules and power combiners for future use in particle accelerators. We report here on these and other ongoing activities at the FREIA laboratory.

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WEPMN070

Measurement Techniques and Application of Combined Parallel/Orthogonal Magnetic Bias on a Ferrite Tuned Resonator in Low Frequency Range (3-10 MHz)

impedance, solenoid, power-supply, network

3087

G. Favia, F. Caspers, M. Morvillo, C. Rossi, C. Vollinger
CERN, Geneva, Switzerland

We present several measurement methods for evaluation of magnetic properties of magnetically biased and non-biased ferrite samples in a coaxial test fixture. One important aspect is the crosscheck of results obtained by using different and independent measurement and evaluation methods. Since a rather high DC bias current has to be applied, a dedicated network was designed that allows the passage of up to 50 A DC without degradation of the RF performance. With a combination of calibration methods and a compensating topology with two identical sample holders, a good performance was achieved. In this context, magnetic material parameters for about 10 different types of ferrite were obtained. The orthogonal magnetic bias was added by placing the entire test fixture into a large toroidal coil. Thus, the bias field can be supplied independently from, and in addition to the classical parallel bias. An optimal combination between the two biasing fields was found, resulting in a reduction of magnetic losses up to 50% on certain ferrites. We show that the mixed magnetization, normally used for garnets only, is beneficial also for other types of ferrites.

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WEPHA013

The Assembly Experience of the First Cryo-module for HIE-ISOLDE at CERN

vacuum, solenoid, instrumentation, linac

3131

Y. Leclercq, G. Barlow, J.A. Bousquet, A. Chrul, P. Demarest, J-B. Deschamps, J.A. Ferreira Somoza, J. Gayde, M. Gourragne, A. Harrison, G. Kautzmann, D. Mergelkuhl, V. Parma, M. Struik, M. Therasse, L.R. Williams
CERN, Geneva, Switzerland
J. Dequaire
Intitek, Lyon, France

The HIE ISOLDE project aims at increasing the energy of the radioactive ion beams of the existing REX ISOLDE facility from the present 3 MeV/u up to 10 MeV/u for A/q to 4.5. The upgrade includes the installation of a superconducting linac in successive phases, for a final layout containing two low-β and four high-β cryo-modules. The first phase involves the installation of two high-B cryo-modules, each housing five high- β superconducting cavities and one superconducting solenoid, aligned within tight tolerances. After having designed and procured the cryo-module components, the first units is now being assembled at CERN, in a dedicated facility including class100 (ISO5) clean rooms equipped with specific tooling. The assembly is foreseen to be ultimate and the cryo-module cold tested by May 2015. In this paper, after a brief description of the main design features of the cryo-module , we present the assembly of the first unit, including the methodology, special tools, assembly procedures and quality assurance aspects. We report on the experience from this first assembly, including tests results, and present prospects for the next-coming cryo-module assemblies.

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WEPHA015

Beam Tests Using a Wide Band RF System Prototype in the CERN PS Booster

acceleration, HLRF, electronics, booster

3134

M.M. Paoluzzi, M.E. Angoletta, A. Findlay, M. Haase, M. Jaussi, A.J. Jones, J.C. Molendijk, J. Sanchez-Quesada
CERN, Geneva, Switzerland

In the framework of the LHC Injectors Upgrade project (LIU) and in view of a complete replacement of the existing CERN PS Booster (PSB) RF systems, a small scale, wide band prototype cavity was installed in 2012 in the machine. Following the encouraging tests done using this limited set up, an almost full scale, RF system prototype has been built and installed in the PSB during the Long Shutdown 1 (LS1). This modular, Finemet® loaded system covers the band 0.5 / 4 MHz corresponding to the h=1 and h=2 frequency ranges. It uses solid-state power stages and includes fast RF feedback for beam loading compensation. New dedicated digital low level electronics have been implemented for all loops required for beam acceleration and interfaces with the general PSB control system. It allows using the new equipment at the fundamental and/or second harmonic of the beam revolution frequency as well as operating it in parallel with the existing RF systems. This paper describes the low level and power sections of the project and reports about the achieved results and experience built up so far.

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WEPHA019

Development and Production of Non-evaporable Getter Coatings for MAX IV

photon, cathode, electron, vacuum

3145

P. Costa Pinto, B. Bártová, B. Holliger, S. Marques Dos Santos, V. Nistor, A. Sapountzis, M. Taborelli, I. Wevers
CERN, Geneva, Switzerland
J. Ahlbäck, E. Al-Dmour, M.J. Grabski, C. Pasquino
MAX-lab, Lund, Sweden

MAX IV is presently under construction at Lund, Sweden, and the first beam for the production of synchrotron radiation is expected to circulate in 2016. The whole set of 3-GeV ring beam pipes is coated with Ti-Zr-V Non Evaporable Getter (NEG) thin film in order to fulfil the average pressure requirement of 1x10^-9 mbar, despite the compact magnet layout and the large aspect ratio of the vacuum chambers. In this work, we present the optimisations of the coating process performed at CERN to coat different geometries and mechanical assembling used for the MAX IV vacuum chambers; the morphology of the thin films is analysed by Scanning Electron Microscopy; the composition and thickness is measured by Energy Dispersive X-ray analysis; the activation of the NEG thin film is monitored by X-ray Photoemission Spectroscopy; the vacuum performance of the coated beam pipes is evaluated by the measurement of hydrogen sticking coefficient. The results of the coating production characterisation for the 84 units coated at CERN are presented.

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WEPHA021

Status of HIE-ISOLDE SC Linac Upgrade

cryomodule, linac, vacuum, niobium

3151

A. Sublet, L. Alberty, K. Artoos, S. Calatroni, O. Capatina, M.A. Fraser, N.M. Jecklin, Y. Kadi, P. Maesen, G.J. Rosaz, K.M. Schirm, M. Taborelli, M. Therasse, W. Venturini Delsolaro, P. Zhang
CERN, Geneva, Switzerland

The HIE-ISOLDE upgrade project at CERN aims at increasing the energy of radioactive beams from 3MeV/u up to 10 MeV/u with mass-to-charge ratio in the range 2.5-4.5. The objective is obtained by replacing part of the existing normal conducting linac with superconducting Nb/Cu cavities. The new accelerator requires the production of 32 superconducting cavities in three phases: 10 high-beta cavities for phase 1 (2016), 10 high-beta cavities for phase 2 (2017) and possibly 12 low-beta cavities for phase 3 (2020). Half of the phase 1 production is completed with 5 quarter-wave superconducting cavities ready to be installed in the first cryomodule. The status of the cavity production and the RF performance are presented. The optimal linac working configuration to minimize cryogenic load and maximize accelerating gradient is discussed.

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WEPHA022

Characterization of Nb Coating in HIE-ISOLDE QWR Superconducting Accelerating Cavities by means of SEM-FIB and TEM

interface, ion, electron, niobium

3155

B. Bártová, S. Calatroni, A. Sublet, M. Taborelli
CERN, Geneva, Switzerland
A.B. Aebersold, D.T.L. Alexander, M. Cantoni
EPFL, Lausanne, Switzerland

The Quarter Wave Resonators (QWR) high-β cavities (0.3m diameter and 0.9m height) are made from OFE 3D-forged copper and are coated by DC-bias diode sputtering with a thin superconducting layer of niobium. The Nb film thickness, morphology, purity and quality are critical parameters for RF performances of the cavity. They have been investigated in a detailed material study. The coating structure at different positions along a test cavity was observed by cross-section imaging using SEM-FIB instrument. The samples from the top of the cavity showed presence of unexpected porosities, whose volume was investigated using FIB tomography. TEM lamella was prepared for two samples (top part and inner conductor of the cavity) to study in detail the grain orientation in the coating, its chemical composition and structure. The 14-layer structure in thick coating was indeed evidenced by the TEM analysis. Chemical mapping revealed the presence of a few nm in size copper precipitates close to the Nb/Cu interface and a passivating oxide layer of 10 nm thickness on top of the coating and around porosities. However no impurities or interface layer along the coating profile were present.

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WEPHA023

Ferrite-tuner Development for 80 MHz Single-Cell RF-Cavity Using Orthogonally Biased Garnets

coupling, simulation, resonance, operation

3159

C. Vollinger, F. Caspers
CERN, Geneva, Switzerland

In the frame of the LHC Injector Upgrade program involving the existing 80 MHz cavities in the CERN PS accelerator, an orthogonally biased ferrite tuner is foreseen to complement the current motor-driven piston tuner. This ferrite tuner shall provide the possibility of a fast frequency shift of about 200 kHz on the fundamental mode, to allow a fast switching between proton and ion frequencies. In order to avoid water cooling and related issues, the challenge was to bring magnetic losses in the tuner to a minimum such that a forced air cooling scheme will be sufficient. The tuner was first designed with simulation tools, a prototype was built and low-power RF testing was performed on the tuner-cavity combination to evaluate tuning range, bandwidth, and stability. These tests were carried out on a single-cell copper RF cavity mock-up with a resonance frequency of 88 MHz, where the ferrite tuner is connected via a tuning loop and the perpendicular magnetic bias for ferrite tuner is provided by a DC bias supply. Simulations and test data will be presented.

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WEPHA024

Preliminary Design of a Perpendicular Biased Ferrite Loaded Accelerating Cavity

simulation, resonance, operation, factory

3163

J. Eberhardt, F. Caspers, C. Vollinger
CERN, Geneva, Switzerland

A ferrite loaded accelerating cavity with a frequency sweep of 18 to 40 MHz is studied for a possible upgrade of the CERN accelerator complex. The resonance frequency of a ferrite loaded cavity shifts by applying an external magnetic bias field to the ferrite material by means of changing the relative permeability. We present the electromagnetic design of such a cavity with a special emphasis on the modeling of the nonlinear, anisotropic and dispersive characteristics of the ferrite’s relative permeability above magnetic saturation. For experimental crosscheck, a ferrite loaded resonant test setup was built which provides results for the material performance in a magnetic bias field. A comparison of numerical simulations and experimental measurements is shown and calculations are benchmarked by measurement data. Based on this study a preliminary design of a ferrite loaded accelerating cavity is described.

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WEPHA045

Design and Construction of the RF Electronic System at Taiwan Photon Source

booster, controls, LLRF, detector

3215

F.-T. Chung, L.-H. Chang, M.H. Chang, L.J. Chen, PY. Chen, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.H. Tsai, Ch. Wang, M.-S. Yeh, T.-C. Yu
NSRRC, Hsinchu, Taiwan

The RF electronic system at NSRRC was made fully in house by the RF group from design through construction to completion. The first RF electronic system includes an analogue LLRF system, a step motor, and an ARC module of a Petra cavity. It was successfully integrated with a 100-kW RF transmitter, high-power RF transfer system, and a cooling system and applied to the booster of TPS. Two duplicated RF electronic system were then applied to the storage ring but integrated with the 300-KW transmitters. With these RF systems, the TPS storage ring achieved beam current 100 mA on 2015 March 26.

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WEPHA052

Test Cavity and Cryostat for SRF Thin Film Evaluation

vacuum, niobium, SRF, cryogenics

3232

O.B. Malyshev, P. Goudket, L. Gurran, D.O. Malyshev, S.M. Pattalwar, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt, L. Gurran
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
P. Goudket, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom
T.J. Jones, E.S. Jordan
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

In developing superconducting coatings for SRF cavities, the coated samples are tested using various techniques such as resistance measurements, AC and DC magnetometry which provide information about the superconducting properties of the films such as RRR, Hc1, Hc2 and vortex dynamics. However, these results do not allow the prediction of the superconducting properties at RF frequencies. A dedicated RF cavity was designed to evaluate surface resistive losses on a flat sample. The cavity contains two parts: a half-elliptical cell made of bulk Nb and a flat Nb disc. The two parts can be thermally and electrically isolated via a vacuum gap, whereas the electromagnetic fields are constrained through the use of RF chokes. Both parts are conduction cooled hence the system is cryogen free. The flat disk can be replaced with a sample, such as a Cu disc coated with Nb film. The RF test provide the cavity Q-factor and thermometrical measurements of the losses on the sample. The design advantages are that the sample disc can be easily installed and replaced; installing a new sample requires no brazing/welding/vacuum or RF seal, so the sample preparation is simple and inexpensive.

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WEPHA053

Surface Resistance RF Measurements of Materials Used for Accelerator Vacuum Chambers

coupling, factory, resonance, network

3235

P. Goudket, L. Gurran, O.B. Malyshev, M.D. Roper, R. Valizadeh, S. Wilde
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt, L. Gurran
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
P. Goudket, O.B. Malyshev, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom
S. Wilde
Loughborough University, Loughborough, Leicestershire, United Kingdom

The RF surface resistance of accelerator vacuum chamber walls can have a significant impact on the beam quality. There is a need to know how the use of a new material, surface coating or surface treatment can affect the RF surface resistance. ASTeC and Lancaster University have designed and built two test cavities where one face can be replaced with a sample in the form of a flat plate. The measurements are performed with a network analyser at the resonant frequency of approximately 7.8 GHz.

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WEPHA054

Commissioning of the Transverse Deflecting Cavity on VELA at Daresbury Laboratory

electron, klystron, vacuum, coupling

3239

A.E. Wheelhouse, R.K. Buckley, S.R. Buckley, L.S. Cowie, P. Goudket, L. Ma, J.W. McKenzie, A.J. Moss
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt, M. Jenkins
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

A 9-cell S-band transverse deflecting copper cavity (TDC) has been designed and built to provide a 5 MV transverse kick in order to perform longitudinal profile measurements of the electron bunch on the Versatile Electron Linear Accelerator (VELA) at Daresbury Laboratory. The cavity has been manufactured by industry and has been field flatness tuned using a beadpull system. The cavity has then been installed on to the VELA facility and commissioned for operation with the electron beam. This paper discusses the tuning and the RF conditioning of the cavity.

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WEPHA057

High Gradient Testing of an X-band Crab Cavity at XBox2

wakefield, klystron, electron, network

3242

B.J. Woolley, P.K. Ambattu, R. Apsimon, G. Burt, A.C. Dexter
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
A. Grudiev, I. Syratchev, R. Wegner, B.J. Woolley, W. Wuensch
CERN, Geneva, Switzerland

CERN’s Compact linear collider (CLIC) will require crab cavities to align the bunches to provide effective head-on collisions. An X-band quasi-TM11 deflecting cavity has been designed and manufactured for testing at CERN’s Xbox-2 high power standalone test stand. The cavity is currently under test and has reached an input power level in excess of 40MW, with a measured breakdown rate of better than 10^-5 breakdowns per pulse. This paper also describes surface field quantities which are important in assessing the expected BDR when designing high gradient structures.

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WEPTY008

Superconducting Harmonic Cavity for the Advanced Photon Source Upgrade

HOM, photon, cryomodule, SRF

3267

M.P. Kelly, A. Barcikowski, J. Carwardine, Z.A. Conway, D. Horan, S.H. Kim, P.N. Ostroumov, G.J. Waldschmidt
ANL, Argonne, Illinois, USA
J. Rathke, T. Schultheiss
AES, Medford, New York, USA

A new bunch lengthening cryomodule using a single-cell ‘higher-harmonic’ superconducting cavity (HHC) based on the TESLA shape and operating at the 4th harmonic (1408 MHz) of the main RF is under development at Argonne. The system will be used to improve the Touschek lifetime and increase the single-bunch current limit in the upgraded multibend achromat lattice of the Advanced Photon Source electron storage ring. The 4 K cryomodule will fit within one half of a straight section, ~2.5 meters, of the ring. The system will use a pair of moveable 20 kW (each) CW RF power couplers to adjust the loaded Q and extract power from the beam. This will provide the flexibility to adjust the impedance presented to the beam and run at various beam currents. Higher-order modes (HOMs) induced by the circulating electron beam will be extracted along the beam axis and damped using a pair of room temperature beam line absorbers. Engineering designs and the prototyping status for the cavity, power couplers and HOM absorbers are discussed.

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WEPTY009

Preservation of Quality Factor of Half Wave Resonator during Quenching in the Presence of Solenoid Field

solenoid, cryomodule, niobium, dipole

3270

S.H. Kim, D.M. Caldwell, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.W.T. MacDonald, P.N. Ostroumov, T. Reid
ANL, Argonne, Illinois, USA

Funding: This work was supported by the U.S. Department of energy, Offices of High-Energy Physics and Nuclear Physics, under Contract No. DE-AC02-76-CH03000 and DE-AC02-06CH11357.
The Proton Improvement Plan II at FNAL relies upon a 162.5 MHz superconducting half-wave resonator cryomodule to accelerate H⁻ beams from 2.1 to 10 MeV. This cryomodule contains 8 resonators with 8 superconducting solenoid magnets interspersed between them. X-Y steering coils are integrated with a package of the superconducting solenoid magnets. The center of the solenoids is located within ~50 cm of the high surface magnetic field of the half-wave resonators and in this study we assess whether or not magnetic flux generated by this magnet is trapped into the half-wave resonators niobium surface and increases the RF losses to liquid helium. To test this we assembled a solenoid with a 162.5 MHz half-wave resonator spaced as they will be in the cryomodule. We measured the quality factor of the cavity before and after the cavity quenched as a function of field level in the coils. No measurable change in the quality factor was observed. In this paper, we will present details of the measurements and discuss the magnetic field map.

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WEPTY010

Electropolishing for Low-Beta and Quasi-Waveguide SRF Cavities

cathode, SRF, niobium, controls

3273

T. Reid, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, P.N. Ostroumov
ANL, Argonne, Illinois, USA

Argonne National Laboratory (ANL) has extended high quality electropolishing techniques based on those developed for the International Linear Collider to several more complex superconducting RF cavities. These include the co-axial TEM-mode quarter-wave and half-wave cavities as well as a 2.8 GHz quasi-waveguide structure intended for beam bunch rotation. This system is an improved version of the one developed for 1.3 GHz 9-cell cavities and includes easy provision for direct water cooling using the helium jacket. The performance of these SRF cavities both in terms of RF fields and losses equals or exceeds that of most 9-cell elliptical cavities built and tested today.

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WEPTY017

Development of 650 MHz β=0.9 5-cell Elliptical Cavities for PIP-II

resonance, proton, linac, controls

3296

M.H. Awida, M.H. Foley, I.V. Gonin, C.J. Grimm, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

5-cell 650 MHz elliptical cavities are being developed for the Proton Improvement Plan II (PIP-II) of Fermilab. The cavities are designed to accelerate protons of relative group velocity β=0.9 at the high energy part of the linear particle accelerator. In this paper, we report the status of these cavities and summarize the results of the quality control measurements performed on four initial prototypes.

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WEPTY018

Analysis of a Quasi-waveguide Multicell Resonator for SPX

wakefield, resonance, higher-order-mode, niobium

3299

M.H. Awida, I.V. Gonin, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
A. Zholents
ANL, Argonne, Ilinois, USA

A compact deflecting cavity is needed for the Short Pulse X-rays (SPX) at the Advanced Photon Source (APS) of Argonne national laboratory. The deflecting cavity has to quite efficient providing a 2 MV kick voltage and satisfying stringent requirements on aperture size and total cavity length. Meanwhile, the cavity should allow operation up to 100 mT peak surface magnetic field before quenching. In this paper, we report on the latest analysis carried out on the cavity structure to investigate frequency sensitivity to pressure fluctuations, frequency sensitivity to tuning forces, modal frequency, and wakefield losses.

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WEPTY019

Transverse Field Perturbation For PIP-II SRF Cavities

quadrupole, multipole, linac, dipole

3302

P. Berrutti, T.N. Khabiboulline, V.A. Lebedev, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by D.O.E. Contract No. DE-AC02-07CH11359
Proton Improvement Plan II (PIP-II) consists in a plan for upgrading the Fermilab proton accelerator complex to a beam power capability of at least 1 MW delivered to the neutrino production target. A room temperature section accelerates H⁻ ions to 2.1 MeV and creates the desired bunch structure for injection into the superconducting (SC) linac. Five cavity types, operating at three different frequencies 162.5, 325 and 650 MHz, provide acceleration to 800 MeV. This paper presents the studies on transverse field perturbation on particle dynamic for all the superconducting cavities in the linac. The effects studied include quadrupole defocusing for coaxial resonators, and dipole kick due to couplers for elliptical cavities. A multipole expansion has been performed for each of the cavity designs including effects up to octupole.

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WEPTY020

Design of a Marx-Topology Modulator for FNAL Linac

feedback, linac, proton, flattop

3306

T.A. Butler, F.G. Garcia, M.R. Kufer, H. Pfeffer, D. Wolff
Fermilab, Batavia, Illinois, USA

The Fermilab Proton Improvement Plan (PIP) was formed in 2011 to address important and necessary upgrades to the Proton Source machines (Injector line, Linac and Booster). The goal is to increase the proton flux by doubling the Booster beam cycle rate while maintaining the same intensity per cycle, the same uptime, and the same residual activation on the accelerating structures. For Linac, the main focus within PIP is to address reliability. One of the main tasks is to replace the present hard-tube modulator used on the main 200MHz RF system. Plans to replace this high power system with a Marx-topology modulator, capable of providing the required waveform shaping to stable the accelerating gradient and compensate for beam loading, will be presented along with development data from the prototype unit.

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WEPTY021

Origin of Trapped Flux Caused by Quench in Superconducting Niobium Cavities

superconductivity, niobium, cryogenics, cryomodule

3309

M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
M. Checchin, M. Martinello
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
In this study we prove that the mechanism at the basis of quality factor degradation due to quench involves the entrapment of ambient magnetic field. The cavity quench in the absence of magnetic field does not introduce any extra losses, and a clear trend between the external field and the extra losses introduced by the quench was observed. It is demonstrated that the quality factor can be totally recovered by quenching in zero applied magnetic field. A dependence of the amount of quality factor degradation on the orientation of the magnetic field with respect to the cavity was also found.

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WEPTY022

Modifications of Superconducting Properties of Niobium Caused by Nitrogen Doping Recipes for High Q Cavities

niobium, SRF, superconductivity, vacuum

3312

A. Vostrikov, M. Checchin, A. Grassellino, A. Romanenko
Fermilab, Batavia, Illinois, USA
Y.K. Kim, A. Vostrikov
University of Chicago, Chicago, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Discovery at Fermilab of a drastic effect of nitrogen doping leading to unprecedented high Q values in niobium cavities * motivated a strong interest in revealing the physics underlying the effect. In this contribution we present new results obtained by DC magnetometry, AC susceptibility, resistivity and thermal properties measurements on nitrogen doped samples prepared by different recipes/doping levels, which shed light on the possible origin of the effect.
* A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001

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WEPTY028

Fermilab Linac Laser Notcher

laser, linac, booster, ion

3328

D.E. Johnson, K.L. Duel, M.H. Gardner, T.R. Johnson, V.E. Scarpine, R. Tesarek
Fermilab, Batavia, Illinois, USA

Synchrotrons or storage rings require a small section of their circumference devoid of any beam (i.e. a “notch”) to allow for the rise time of an extraction kicker device. In multi-turn injection schemes, this notch in the beam may be generated either in the linac pulse prior to injection or in the accelerator itself after injection. In the case of the Fermilab Booster, the notch is created in the ring near injection energy by the use of fast kickers, thus depositing the beam in a shielded collimation region within the accelerator tunnel. With increasing beam powers, it is desirable to create this notch at the lowest possible energy to minimize activation. Fermilab has undertaken an R&D project to build a laser system to create the notch within a linac beam pulse, immediately after the RFQ at 750 keV, where activation issues are negligible. We will describe the concept for the laser notcher and discuss our current status and future plans for installation of the device.

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WEPTY030

Breakdown Characterization in 805 MHz Pillbox-like Cavity in Strong Magnetic Fields

site, electron, pick-up, vacuum

3335

A.V. Kochemirovskiy, D.L. Bowring, A. Moretti, D.W. Peterson, K. Yonehara
Fermilab, Batavia, Illinois, USA
M. Chung
UNIST, Ulsan, Republic of Korea
G. Flanagan, G.M. Kazakevich
Muons, Inc, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

RF Breakdown in strong magnetic fields has a negative impact on a cavity performance. The MuCool Test Area at Fermilab has unique capabilities that that allow us to study the effects of static magnetic field on RF cavity operation. We have tested an 805 MHz pillbox-like cavity in external magnetic fields up to 5T. Results confirm our basic model of breakdown in strong magnetic fields. We have measured maximum achievable surface gradient dependence on external static magnetic field. Damage inspection of cavity walls revealed a unique observed breakdown pattern. We present the analysis of breakdown damage distribution and propose the hypothesis to explain certain features of this distribution

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WEPTY031

Estimation of Cryogenic Heat Loads in Cryomodule due to Thermal Radiation

niobium, radiation, cryomodule, cryogenics

3338

A. Saini, V.A. Lebedev, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Cryogenic system is one of major cost drivers in high intensity superconducting (SC) continuous wave (CW) accelerators. Thermal radiations coming through the warm-ends of cryomodule and room temperature parts of the power coupler result in additional cryogenic heat loads. Excessive heat load in 2K environment may degrade overall performance of the cavity. In this paper we present studies performed to estimate additional heat load at 2K due to thermal radiation in 650 MHz cavity cryomodule in high energy section of PIP-II SC linac.

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WEPTY032

MICE Cavity Installation and Commissioning/Operation at MTA

operation, instrumentation, solenoid, vacuum

3342

M.A. Leonova, M. Backfish, D.L. Bowring, A.V. Kochemirovskiy, A. Moretti, D.W. Peterson, M. Popovic, Y. Torun, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
C. Hunt
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
P.G. Lane
Illinois Institute of Technology, Chicago, Illinois, USA
T.H. Luo
LBNL, Berkeley, California, USA
D.C. Speirs, C.G. Whyte
USTRAT/SUPA, Glasgow, United Kingdom
T. Stanley
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

A first electropolished 201-MHz RF cavity for the international Muon Ionization Cooling Experiment (MICE) has been assembled inside a special vacuum vessel and installed at the Fermilab's MuCool Test Area (MTA). The cavity and the MTA hall have been equipped with numerous instrumentation to characterize cavity operation. The cavity has been commissioned to run at 14 MV/m gradient with no external magnetic field; it is also being commissioned in presence of fringe field of a multi-Tesla superconducting solenoid magnet, the condition in which cavity modules will be operated in the MICE cooling channel. The assembly, installation and operation of the Single-Cavity Module gave valuable experience for operation of full-size modules at MICE.

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WEPTY034

T-map Studies on Gradient-limiting Mechanism in Nitrogen Doped Cavities

niobium, superconductivity, factory, SRF

3348

M. Martinello, M. Checchin, A. Grassellino, A. Romanenko
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Nitrogen doping * results in ultra-high quality factors in SRF niobium cavities but currently achievable gradients in doped cavities are, on average, somewhat lower than in EP/120C baked cavities. The origin of this difference is explored in the reported work by detailed temperature mapping studies on several single cell nitrogen doped cavities.
* A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001

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WEPTY035

Design and Test of the Compact Tuner for Narrow Bandwidth SRF Cavities

cryogenics, operation, SRF, vacuum

3352

Y.M. Pischalnikov, E. Borissov, I.V. Gonin, J.P. Holzbauer, T.N. Khabiboulline, W. Schappert, S.J. Smith, J.C. Yun
Fermilab, Batavia, Illinois, USA

Funding: Fermi Research Alliance, LLC under Contract N. DE-AC02-07CH11359 with U.S. Department of Energy.
The design of the compact tuner for 1.3 GHz 9-cell elliptical cavity will be presented. This compact tuner is designed for future accelerators that will operate in CW and pulsed RF-power modes. The major design features include highly reliable active components (electromechanical actuators and piezo-actuators) and the ability to replace tuner active components through designated ports in the cryomodule vacuum vessel. Results of tuner testing with cold cavity will also be presented.

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WEPTY036

Progress at FNAL in the Field of the Active Resonance Control for Narrow Bandwidth SRF Cavities.

resonance, feedback, operation, controls

3355

W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA

Funding: Fermi Research Alliance, LLC under Contract N. DE-AC02-07CH11359 with U.S. Department of Energy.
Recent efforts at FNAL to actively compensate microphonics in narrow bandwidth cavities are discussed. Feed-forward compensation of Lorentz force detuning in combination with feedback of the forward/probe phase difference to a piezo actuator successfully stabilized the resonance of a 325 MHz spoke resonator to within 11 mHz of the frequency of the open-loop CW RF drive over a two hour interval.

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WEPTY037

A Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster

booster, simulation, solenoid, TRIUMF

3358

C.-Y. Tan, J.E. Dey, R.L. Madrak, W. Pellico, G.V. Romanov, D. Sun, I. Terechkine
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
A perpendicular biased 2nd harmonic cavity is currently being designed for the Fermilab Booster. Its purpose cavity is to flatten the bucket at injection and thus change the longitudinal beam distribution so that space charge effects are decreased. It can also work at transition to help beam cross it. The choice of perpendicular biasing over parallel biasing is that the Q of the cavity is much higher and thus allows the accelerating voltage to be a factor of 2 higher than a similar parallel biased cavity. This cavity will also provide a higher accelerating voltage per meter than the present folded transmission line cavity. However, this type of cavity presents technical challenges that need to be addressed. The two major issues are cooling of the garnet material from the effects of the RF and the cavity itself from eddy current heating because of the 15 Hz bias field ramp. This paper will address the technical challenge of preventing the garnet from overheating.

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WEPTY045

High-Intensity Proton RFQ Accelerator Fabrication Status for PXIE

rfq, vacuum, alignment, quadrupole

3375

A.R. Lambert, A.J. DeMello, M.D. Hoff, D. Li, T.H. Luo, J.W. Staples, S.P. Virostek
LBNL, Berkeley, California, USA
R. Andrews, C.M. Baffes, P. Berrutti, T.N. Khabiboulline, G.V. Romanov, D. Snee, J. Steimel
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC02-05CH11231
PXIE is a prototype front end system for the proposed PIP-II accelerator upgrade at Fermilab. An integral component of the front end is a 162.5 MHz, normal conducting, CW (continuous wave), radio-frequency quadrupole (RFQ) cavity that was designed and is being fabricated by LBNL. This RFQ will accelerate a continuous stream of up to 10mA of H⁻ ions from 30 keV to 2.1 MeV. The four-vane, 4.45 meter long RFQ consists of four modules, each constructed from 2 pairs of identical modulated vanes. Vane modulations are machined using a custom carbide cutter designed at LBNL. Other machined features include ports for slug tuners, pi-mode rods, sensing loops, vacuum pumps and RF couplers. Vanes at the entrance and exit possess cutbacks for RF matching to the end plates. The vanes and pi-mode rods are bonded via hydrogen brazing with Cusil wire alloy. The brazing process mechanically bonds the RFQ vanes together and vacuum seals the module along its length. Vane fabrication is successfully completed, and the braze process has proved successful. Delivery of the full RFQ beam-line is expected in the middle of 2015.

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WEPTY046

Progress on the MICE 201 MHz Cavities at LBNL

Windows, coupling, simulation, network

3378

T.H. Luo, A.J. DeMello, A.R. Lambert, D. Li, S. Prestemon, S.P. Virostek
LBNL, Berkeley, California, USA

The international Muon Ionization Cooling Experiment aims to demonstrate the transverse cooling of amuon beam by ionization in energy absorbers. The final MICE cooling channel configuration has two RF modules, each housing a 201 MHz RF cavity used to compensate the longitudinal energy loss in the absorbers. The LBNL team has designed and fabricated all MICE RF cavities. The cavities will be post-processed and RF measured before being installed in the RF modules. We present the recent progress on this work, including the low level RF measurement on cavity body and Be windows, the electro-polishing (EP) on the cavity surface, the numerical simulation on cavity Be window detuning, and the ongoing mechanical designing work of cavity components.

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WEPTY047

Thermal and Lorentz Force Analysis of Beryllium Windows for the Rectilinear Muon Cooling Channel

Windows, simulation, collider, emittance

3381

T.H. Luo, D. Li, S.P. Virostek
LBNL, Berkeley, California, USA
D.L. Bowring
Fermilab, Batavia, Illinois, USA
R.B. Palmer, D. Stratakis
BNL, Upton, Long Island, New York, USA

Reduction of the 6-dimensional phase-space of a muon beam by several orders of magnitude is a key requirement for a Muon Collider. Recently, a 12-stage rectilinear ionization cooling channel has been proposed to achieve that goal. The channel consists of a series of low frequency (325 MHz-650 MHz) normal conducting pillbox cavities, which are enclosed within thin beryllium windows (foils) to increase shunt impedance and give a higher field on-axis for a given amount of power. These windows are subject to ohmic heating from RF currents and Lorentz force from the EM field in the cavity, both of which will produce out of plane displacements that can detune the cavity frequency. In this study, using the TEM3P code, we report on a detailed thermal and mechanical analysis for the actual Be windows used on a 325 MHz cavity in a vacuum ionization cooling rectilinear channel for a Muon Collider.

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WEPTY050

Low Powered RF Measurements of Dielectric Materials for use in High Pressure Gas Filled RF Cavities

simulation, radio-frequency, factory, collider

3387

B.T. Freemire
IIT, Chicago, Illinois, USA
G. Arriaga
Northern Illinois Univerity, Dekalb, Illinois, USA
D.L. Bowring, A.V. Kochemirovskiy, A. Moretti, A.V. Tollestrup, Y. Torun, K. Yonehara
Fermilab, Batavia, Illinois, USA
H.D. Phan
McDaniel College, Westminster, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

The Helical Cooling Channel scheme envisioned for a Muon Collider or Neutrino Factory requires high pressure gas filled radio frequency cavities to operate in superconducting magnets. One method to shrink the radii of the cavities is to load them with a dielectric material. The dielectric constant, loss tangent, and dielectric strength are important in determining the most suitable material. Low powered RF measurements of the dielectric constant and loss tangent were taken for multiple purities of alumina and magnesium calcium titanate, as well as cordierite, forsterite, and aluminum nitride. Measurements of alumina were consistent with previously reported results. The results were used to design an insert for a high powered RF test that included sending beam through the cavity.

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WEPTY054

Grid Window Tests on an 805-MHz Pillbox Cavity

Windows, scattering, radiation, controls

3393

Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA
A. Moretti
Fermilab, Batavia, Illinois, USA

Funding: Supported by the US Department of Energy Office of Science through the Muon Accelerator Program.
Muon ionization cooling channel designs use pillbox shaped RF cavities for improved power efficiency and fine control over phasing of individual cavities. For minimum scattering of the muon beam, the ends should be made out of a small thickness of high radiation length material. Good electrical and thermal conductivity are required to reduce power dissipation and remove the heat efficiently. Thin curved beryllium windows with TiN coating have been used successfully in the past. We have built an alternative window set consisting of grids of tubes and tested these on a pillbox cavity previously used with both thin Be and thick Cu windows. The cavity was operated with a pair of grids as well as a single grid against a flat endplate.

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WEPTY055

Installation and Commissioning of the MICE RF Module Prototype

vacuum, Windows, operation, coupling

3395

Y. Torun, P.G. Lane
Illinois Institute of Technology, Chicago, Illlinois, USA
T.G. Anderson, D.L. Bowring, M. Chung, J.H. Gaynier, M.A. Leonova, A. Moretti, R.J. Pasquinelli, D.W. Peterson, R.P. Schultz
Fermilab, Batavia, Illinois, USA
A.J. DeMello, D. Li, S.P. Virostek
LBNL, Berkeley, California, USA
L. Somaschini
INFN-Pisa, Pisa, Italy

Funding: Supported by the US Department of Energy Office of Science through the Muon Accelerator Program.
A special vacuum vessel prototype was built to house the first production 201 MHz RF cavity for the International Muon Ionization Cooling Experiment (MICE). The resulting prototype RF module has been assembled, instrumented, installed and commissioned at Fermilab's MuCool Test Area and the effort has provided valuable experience for the design of modules that will be used in the cooling channel for the experiment.

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WEPTY060

Virtual Welding as a Tool for Superconducting Cavity Coarse Tuning

electron, target, proton, operation

3412

A. Facco, C. Compton, J. Popielarski, G.J. Velianoff
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
Reaching the final frequency in the construction of Superconducting Half-Wave Resonators (HWR), either coaxial or spoke, is often a painful and time consuming process which requires several intermediate frequency tests and parts machining between subsequent welding steps. In spite of that, the final frequency error after final welding is often far from the target due to difficult to predict material contraction and cavity deformation induced by electron beam welding (EBW). Final coarse tuning is required by plastic deformation or differential etching. In coaxial HWR, both can decrease the cavity frequency but are not easily suitable to increase it. A novel method developed at MSU is “virtual” welding, i.e. deformation of the cavity shape by applying systematically EBW on the cavity outer surface to induce controlled Nb material contraction in strategic positions. This technique allows to increase the cavity frequency with excellent precision and predictability, thus simplifying and making less expensive and more reliable HWR coarse tuning. Method and experimental results will be described and discussed.

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WEPTY062

Multipactor Breakdown Modelling Using an Averaged Version of Furman's SEY Model

multipactoring, simulation, electron, plasma

3419

S.A. Rice, J.P. Verboncoeur
Michigan State University, East Lansing, Michigan, USA

Funding: Work supported by a MSU Strategic Partnership Grant.
Furman's seconday electron yield model is commonly used for the simulation of multipactor in accelerating cavities and other resonant structures. While accurate, the stochastic model requires many Monte Carlo simulations in order to characterize susceptibility to multipactor. This paper generalizes our previous research in characterizing a reduced-order Furman model, in which we replace the stochastic Furman model with a deterministic model based upon the Furman model's underlying statistics. Favorable comparisons between the full Furman model and the reduced-order Furman model are shown for multipactor simulations in a coaxial cavity, and the results are expected to generalize to other geometries.

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WEPTY063

Co-Linear X-Band Energy Booster (XCEB) Cavity and RF System Details

electron, impedance, extraction, linac

3421

T. Sipahi, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA

Due to their higher intrinsic shunt impedance X-band accelerating structures offer significant gradients with relatively modest input powers. At the Colorado State University Accelerator Laboratory (CSUAL) we would like to adapt this technology to our 1.3-GHz, L-band accelerator system in order to increase our overall beam energy in a manner that does not require investment in an expensive, custom, high-power X-band klystron system. Here we provide the design details of the X-band structures that will allow us to achieve our goal of reaching the maximum practical net potential across the X-band accelerating structure while driven solely by the beam from the L-band system.

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WEPTY066

T-Maps Taken During Cool-down of an SRF cavity: a Tool to Understand Flux Trapping

SRF, superconductivity, data-analysis, operation

3431

R.G. Eichhorn, F. Furuta, G.M. Ge
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

During the past years the impact of cool-down procedures on the flux trapping properties of superconducting cavities have been under investigation. We have measured temperature distributions of a multi-cell cavity using a T-map set-up to understand the transition to superconductivity in detail. We will report how the spatial disorder is affected by the cool-down speed and relate our findings to data on flux pinning.

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WEPTY067

Thermal and Mechanical Analysis of a Waveguide to Coax Symmetric Coupler for Superconducting Cavities

electron, niobium, simulation, dipole

3434

R.G. Eichhorn, J.A. Robbins, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

As kicks from fundamental power couplers become a concern for low emittance future accelerators, a design for a symmetric coupler for superconducting accelerating cavities has been started. In this coupler, a rectangular waveguide transforms into a coaxial line inside the beam pipe to feed the cavity. So far the RF design revealed an extremely low transversal kick but concerns about cooling and the thermal stability of the coaxial transition line remained. Our contribution will address this. We will calculate heating, heat transfer and thermal stability of this coupler and evaluate the risk of quenching due to particle losses on the coupler.

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WEPTY068

Asymmetric Thermo-currents Diminishing SRF Cavity Performance

niobium, simulation, SRF, superconducting-cavity

3437

R.G. Eichhorn, J. May-Mann
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Over the past years it became evident that the quality factor of a superconducting cavity is not only determined by its surface preparation procedure, but is also influenced by the way the cavity is cooled down. In this paper we will present results from numerical field calculations of magnetic fields produced by thermo-currents, driven by temperature gradients and material transitions. We will show how they can impact the quality factor of a cavity by producing a magnetic field at the RF surface of the cavity.

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WEPTY069

Complection of the Cornell High Q CW Full Linac Cryo-module

linac, HOM, cryomodule, alignment

3440

R.G. Eichhorn, B. Bullock, B. Clasby, J.V. Conway, B. Elmore, F. Furuta, G.M. Ge, G.H. Hoffstaetter, M. Liepe, T.I. O'Connel, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Y. He
Fermilab, Batavia, Illinois, USA

Cornell University has finished building a 10 m long superconducting accelerator module as a prototype of the main linac of a proposed ERL facility. This module houses 6 superconducting cavities- operated at 1.8 K in continuous wave (CW) mode - with individual HOM absorbers and one magnet/ BPM section. In pushing the limits, a high quality factor of the cavities (2x10¹⁰) and high beam currents (100 mA accelerated plus 100 mA decelerated) were targeted. We will review the design shortly and present the results of the components tested before the assembly. This includes data of the quality-factors of all 6 cavities that we produced and treated in-house, the HOM absorber performance measured with beam on a test set-up as well as testing of the couplers and the tuners.

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WEPTY072

Update on Nitrogen-doped 9-cell Cavity Performance in the Cornell Horizontal Test Cryomodule

cryomodule, linac, SRF, operation

3446

D. Gonnella, R.G. Eichhorn, F. Furuta, G.M. Ge, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, J.T. Maniscalco, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A. Grassellino, C.J. Grimm, O.S. Melnychuk, A. Romanenko
Fermilab, Batavia, Illinois, USA

Funding: U.S. Department of Energy
The Linac Coherent Light Source-II (LCLS-II) is a new x-ray source that is planned to be constructed in the existing SLAC tunnel. To meet the quality factor specifications (2.7x 10¹⁰ at 2.0 K and 16 MV/m), nitrogen-doping has been proposed as a preparation method for the SRF cavities. In order to demonstrate the feasibility of these goals, four 9-cell cavity tests have been completed in the Cornell Horizontal Test Cryomodule (HTC), which serves as a test bench for the full LCLS-II cryomodule. Here we report on the most recent two cavity tests in the HTC: one cavity nitrogen-doped at Cornell and tested with high Q input coupler and then again tested with high power LCLS-II input coupler. Transition to test in horizontal cryomodule resulted in no degradation in Q0 from vertical test. Additionally, increased dissipated power due to the high power input coupler was small and in good agreement with simulations. These results represent a crucial step on the way to demonstrating technical readiness for LCLS-II.

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WEPTY073

Update on Nitrogen Doping: Quench Studies and Sample Analysis

niobium, vacuum, SRF, radiation

3450

D. Gonnella, F. Furuta, G.M. Ge, J.J. Kaufman, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: U.S. Department of Energy, NSF
Recently, nitrogen-doping of niobium has emerged as a promising preparation method for SRF cavities to reach higher intrinsic quality factors than can be reached with typical cavity preparation. Nitrogen-doped cavities prepared at Cornell have shown quality factors higher than 4x10¹⁰ at 2.0 K and 16 MV/m. While Q results have been very exciting, a reduced quench field currently limits nitrogen-doped cavities with quench typically occurring between 15 and 25 MV/m. Here we report on recent results from Cornell on single-cell and 9-cell cavities, focusing on new preparations and maximum and critical fields. First we discuss results from over-doping niobium with nitrgoen, baking nitrogen-doped cavities at 120C, and doping with Argon. For a subset of these cavities we show results from quench studies that have been completed using temperature mapping. Finally, we present the first measurements of the higher critical field, Hc2, for nitrogen-doped niobium samples.

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WEPTY074

Recent Studies on the Current Limitations of State-of-the-Art Nb3Sn Cavities

niobium, cryomodule, controls, accelerating-gradient

3454

D.L. Hall, M. Liepe, J.T. Maniscalco, S. Posen
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Th. Proslier
ANL, Argonne, Illinois, USA

Funding: NSF PHY-1305500 PHY-14116318 DOE ER41802
Recent advances in the study of Nb3Sn at Cornell University have yielded single-cell cavities that show excellent performance without the limiting Q-slope seen in previous work. This performance has been shown to be repeatable across multiple cavities. However, they are still limited by a quench field of approximately 16 MV/m, as well as residual resistance. In this work we present results quantifying the impact of ambient magnetic fields on Nb3Sn cavities, as well as discuss the impact of cavity cooldown procedures on cavity performance. Finally, we will briefly discuss XRD results that shed light on the composition of the Nb3Sn layer and how this relates to the current limits of these cavities.

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WEPTY076

RF Performance Studies of Thin-Film Superconductors Using a Sample Host Cavity

niobium, SRF, operation, background

3462

J.T. Maniscalco, D.L. Hall, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Thin-film superconductors have the potential for reduced cost and for improved SRF performance over traditional bulk niobium superconducting cavities. Materials such as Nb3Sn, multilayer NbN/MgO, and thin-film Nb are currently under investigation for cost reduction or possible improvements in RF losses and accelerating gradients. Due to the complex geometries of traditional RF cavities, it is preferable to use a sample host cavity to study flat samples of the novel materials. The Cornell sample host cavity has been commissioned and has now reached peak magnetic surface fields of 100 mT. We present updates on the recent performance of the cavity.

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WEPTY077

On Quench Propagation, Quench Detection, and Second Sound in SRF Cavities

niobium, simulation, SRF, radio-frequency

3464

S.R. Markham, R.G. Eichhorn
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The detection of a second sound wave, excited by a quench, has become a valuable tool in diagnosing hot spots and performance limitations of superconducting cavities. Several years ago, Cornell developed an oscillating super-leak transducer (OST) for these waves that nowadays are used world-wide. In a usual set-up, several OSTs surround the cavity, and the quench location is determined by triangulation of the different OST signals. Convenient as the method is there is a small remaining mystery: taking the well-known velocity of the second sound wave, the quench seems to come from a place slightly above the cavity’s outer surface. We will present a model based on numerical quench propagation simulations and analytic geometrical calculations that help explain the discrepancy.

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WEPTY078

High Q0 at Medium Fields in Nb3Sn SRF Cavities at 4.2 K

niobium, cryogenics, SRF, operation

3467

S. Posen, D.L. Hall, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Th. Proslier
ANL, Argonne, Illinois, USA

Nb3Sn has proven itself to be a very promising alternative SRF material. With twice the critical temperature of niobium cavities, 1.3 GHz Nb3Sn cavities can achieve quality factors on the order of 10¹⁰ even at 4.2 K, significantly reducing cryogenic infrastructure and operational costs. In addition, its large predicted superheating field may allow for maximum accelerating gradients up to twice that of niobium for high energy applications. In this work, we report on new cavity results from the Cornell Nb3Sn SRF program demonstrating a significant improvement in the maximum field achieved with high Q0 in a Nb3Sn cavity. At 4.2 K, accelerating gradients above 16 MV/m were obtained with Q0 of 8x10⁹, showing the potential of this material for future applications. In addition to this result, current limitations are discussed.

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WEPTY082

High Gradient Testing of the Five-cell Superconducting RF Module with a PBG Coupler Cell

HOM, linac, SRF, coupling

3471

S. Arsenyev, W.B. Haynes, D.Y. Shchegolkov, E.I. Simakov, T. Tajima
LANL, Los Alamos, New Mexico, USA
C.H. Boulware, T.L. Grimm, A. Rogacki
Niowave, Inc., Lansing, Michigan, USA

We report results of high-gradient testing of the first 5- cell superconducting radio frequency (SRF) module with a photonic band gap cell (PBG). Higher order mode (HOM) damping is vital for preserving the quality of high-current electron beams in novel SRF accelerators. Because HOMs are not confined by the PBG array, they can be effectively damped in order to raise the current threshold for beam instabilities. The PBG design increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of via the beam pipe at the ends of the cavity. A superconducting multi-cell cavity with a PBG damping cell is therefore an attractive option for high-current linacs. The first-ever SRF multi-cell cavity incorporating a PBG cell was designed a LANL and built at Niowave Inc. The cavity was tuned to a desired gradient profile and underwent surface treatment at Niowave. A vertical test (VTS) was then performed at LANL, demonstrating an abnormally low cavity quality factor in the accelerating mode of 1.6*10⁶. Future tests are proposed to determine the source of the losses and resolve the problem.

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WEPTY083

Five-cell Superconducting RF Module with a PBG Coupler Cell: Design and Cold Testing of the Copper Prototype

HOM, factory, damping, impedance

3475

S. Arsenyev, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
C.H. Boulware, T.L. Grimm, A. Rogacki
Niowave, Inc., Lansing, Michigan, USA

We report the design and experimental data for a copper prototype of a superconducting radio-frequency (SRF) accelerator module. The five-cell module has an incorporated photonic band gap (PBG) cell with couplers. The purpose of the PBG cell is to achieve better higher order mode (HOM) damping which is vital for preserving the quality of highcurrent electron beams. Better HOM damping raises the current threshold for beam instabilities in novel SRF accelerators. The PBG design also increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of on the beam pipe via complicated end assemblies. First, we will discuss the design and accelerating properties of the structure. The five-cell module was optimized to provide good HOM damping while maintaining the same accelerating properties as conventional elliptical-cell modules. We will then discuss the process of tuning the structure to obtain the desired accelerating gradient profile. Finally, we will list measured quality factors for the accelerating mode and the most dangerous HOMs.

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WEPTY084

Cooling Systems for the New 201.25 MHz Final Power Amplifiers at Los Alamos Neutron Science Center (LANSCE)

DTL, hardware, neutron, controls

3479

W.C. Barkley, C.E. Buechler, J.T.M. Lyles, A.C. Naranjo
LANL, Los Alamos, New Mexico, USA
D. Baca, R.E. Bratton
Compa Industries, Inc., Los Alamos, New Mexico, USA

Funding: Los Alamos National Laboratory, an affirmative action/equal opportunity employer, is operated by the University of California for the U.S. Department of Energy under contract W-7405-ENG-36.
Two new 201.25 MHz RF Final Power Amplifiers (FPAs) have been designed, fabricated, assembled, installed and successfully tested at the Los Alamos Neutron Science Center (LANSCE), in Module 2 of the Drift Tube Linac. These production units were fabricated at Continental Electronics Corporation. In this paper, we summarize the FPAs air and water cooling requirements and cooling systems.

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WEPWI001

An Overview of the MaRIE X-FEL and Electron Radiography Linac RF Systems

linac, klystron, electron, FEL

3482

J.T. Bradley III, D. Rees, A. Scheinker, R.L. Sheffield
LANL, Los Alamos, New Mexico, USA

The purpose of the Matter-Radiation Interactions in Extremes (MaRIE) facility at Los Alamos National Laboratory is to investigate the performance limits of materials in extreme environments. The MaRIE facility will utilize a 12 GeV linac to drive an X-ray FEL. Most of the same linac will also be used to perform electron radiography. The main linac is driven by two shorter linacs; one short linac optimized for X-FEL pulses and one for electron radiography. The RF systems have historically been the one of the largest single component costs of a linac. We will describe the details of the different types of RF systems required by each part of the linacs. Starting with the High Power RF system, we will present our methodology for the choice of RF system peak power and pulselength with respect to klystrons parameters, modulator parameters, performance requirements and relative costs. We will also present an overview of the low level RF systems that are proposed for MaRIE and briefly describe their use with some proposed control schemes. *
* A. Scheinker, "Adaptive Accelerator Tuning", Proc. of IPAC'15.

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WEPWI002

Installation and Operation of Replacement 201 MHz High Power RF System at LANSCE

DTL, linac, controls, electronics

3485

J.T.M. Lyles, W.C. Barkley, J. Davis, D. Rees, G. M. Sandoval, Jr.
LANL, Los Alamos, New Mexico, USA
R.E. Bratton, R.D. Summers
Compa Industries, Inc., Los Alamos, New Mexico, USA

Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE--AC52--06NA25396.
The LANSCE RM project has restored the linac to high power capability after the power tube manufacturer could no longer provide triodes that consistently met our high average power requirement. Diacrodes® now supply RF power to two of the four DTL tanks. These tetrodes reuse the existing infrastructure including water-cooling systems, coaxial transmission lines, high voltage power supplies and capacitor banks. The power amplifier system uses a combined pair of LANL-designed cavity amplifiers using the TH628L Diacrode® to produce up to 3.5 MW peak and 420 kW of mean power. Design and prototype testing was completed in 2012, with commercialization following in 2013. The first installation was completed in 2014 and a second installed system is ready to test. The remaining replacement will follow in 2016. Meanwhile, there is a hybrid of old/new amplifiers until the changeover is complete. Operating results of the replacement system are summarized, along with observations from the rapid--paced installation project.

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WEPWI003

Design of a Radial Klystron

klystron, electron, space-charge, bunching

3489

M. Dal Forno, A. Jensen, R.D. Ruth, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: Work supported by the US DOE under contract DEAC03-76SF00515.
The radial klystron is a multidimensional rf source where the beam is generated by a cylindrical gun and it propagates in the radial dimension. The advantage of this design is that the space charge effects are balanced in the azimuthal dimension and a lower magnetic fields is required to focus the electron beam. The bunching is made with concentric coaxial resonators, connected by drift tube. The electron beam interaction with the cavity fields has been analyzed by means of particle tracking software in order to evaluate the beam bunching and the beam dynamics. This paper shows the klystron design, optimizing the shape and the position of each cavity, in order to maximize the efficiency of the device.

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WEPWI004

FPC and Hi-Pass Filter HOM Coupler Design for the RF Dipole Crab Cavity for the LHC HiLumi Upgrade

HOM, dipole, coupling, damping

3492

Z. Li
SLAC, Menlo Park, California, USA
S.U. De Silva, J.R. Delayen, R.G. Olave, H. Park
ODU, Norfolk, Virginia, USA

Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515.
A 400-MHz compact RF dipole (RFD) crab cavity design was jointly developed by Old Dominion University and SLAC under the support of US LARP program for the LHC HiLumi upgrade. The RFD cavity design is consisted of a rounded-square tank and two ridged deflecting poles, operating with a TE11-like dipole mode, which is the lowest mode of the cavity. A prototype RFD cavity is being manufactured and will be tested on the SPS beam line at CERN. The coaxial fundamental Power Coupler (FPC) of the prototype cavity was re-optimized to minimizing the power heating on the coupler internal antenna. A hi-pass filter HOM damping coupler was developed to achieve the required wakefield damping while maintaining a compact size to fit into the beam line space. In this paper, we will discuss the details of the RF optimization and tolerance analyses of the FPC and HOM couplers.

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WEPWI007

TTF3 Power Coupler Thermal Analysis for LCLS-II CW Operation

simulation, operation, SRF, resonance

3503

L. Xiao, C. Adolphsen, Z. Li, C.D. Nantista, T.O. Raubenheimer
SLAC, Menlo Park, California, USA
I.V. Gonin, N. Solyak
Fermilab, Batavia, Illinois, USA

The TESLA 9-cell SRF cavity design has been adopted for use in the LCLS-II SRF Linac. Its TTF3 coaxial Fundamental Power Coupler (FPC), developed for pulsed operation in the European XFEL and ILC, requires modest changes to make it suitable for LCLS-II CW operation, in which it must be able to handle up to 7 kW of average power with the maximum temperature rise not to exceed 150 C. In order to improve TTF3 FPC cooling, an increased copper plating thickness will be used on the inner and outer conductor stainless steel RF surfaces. Fully 3D FPC thermal analysis with copper plating was performed using the SLAC developed parallel finite element code suite ACE3P with integrated electromagnetic, thermal and mechanical multi-physics simulation capabilities. In this paper, we present TTF3 FPC thermal analysis simulation results obtained using ACE3P as well as a comparison with measurement results.

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WEPWI009

Nitrogen Doping Study in Ingot Niobium Cavities

niobium, SRF, accelerating-gradient, radio-frequency

3506

P. Dhakal, G. Ciovati, P. Kneisel, G.R. Myneni
JLab, Newport News, Virginia, USA
J. Makita
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Thermal diffusion of nitrogen in superconducting radio frequency cavities at temperatures around 800C has resulted in the increase in quality factor with a low-field Q-rise. However, the maximum accelerating gradients of these doped cavities often reduces below the values achieved by standard treatments. In this contribution, we present the results of the nitrogen diffusion into ingot niobium cavities subjected to successive material removal from the inner cavity surface by electropolishing in an effort to explore the underlying cause for the gradient degradation.

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WEPWI010

Results from the First Single Cell Nb3Sn Cavity Coatings at JLab

niobium, network, accelerating-gradient, resonance

3509

G.V. Eremeev
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Nb3Sn is a promising superconducting material for SRF applications and has the potential to exceed the limitations of niobium. We have used the recently commissioned Nb3Sn coating system to investigate Nb3Sn coatings on several single cell cavities by applying the same coating procedure on several different single cells with different history and pre-coating surface preparation. We report on our findings with four 1.5 GHz CEBAF-shape single cell and one 1.3 GHz ILC-shape single cavities that were coated, inspected, and tested.

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WEPWI011

Commissioning Results of Nb3Sn Cavity Vapor Diffusion Deposition System at JLab

niobium, SRF, vacuum, network

3512

G.V. Eremeev, W.A. Clemens, K. Macha, H. Park, R.S. Williams
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Nb3Sn as a BCS superconductors with a superconducting critical temperature higher than that of niobium offers potential benefit in lower surface resistance at the same temperature and frequency for SRF cavities. A Nb3Sn vapor diffusion deposition system was built and commissioned at Jefferson Lab. As the part of the commissioning a single cell 1.5 GHz CEBAF-shaped cavity was coated in the built system. The cavity exhibited the superconducting transition at about 17.9 K. The low field quality factor was about 5x10⁹ at 4 K and 7x10⁹ at 2 K dropping with field to about 10⁹ at both temperatures at about 8 MV/m.

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WEPWI012

First Attempt of At-cavity X-ray Detection in a CEBAF Cryomodule for Field Emission Monitoring

cryomodule, cryogenics, electron, ion

3515

R.L. Geng, E. Daly, M.A. Drury, A.D. Palczewski
JLab, Newport News, Virginia, USA

We report on the first result of at-cavity X-ray detection in a CEBAF cryomodule for field emission monitoring. In the 8-cavity cryomodule F100, two silicon diodes were installed near the end flange of each cavity. Each cavity was individually tested during the cryomodule test in JLab’s cryomodule test facility. The behaviors of these at-cavity cryogenic X-ray detectors were compared with those of the standard “in air” Geiger-Muller tubes. Our initial experiments establish correlation between X-ray response of near diodes and the field emission source cavity in the 8-cavity string. For two out of these eight cavities, we also carried out at-cavity X-ray detection experiment during their vertical testing. The aim is to track field emission behavior uniquely from vertical cavity testing to horizontal cavity testing in the cryomodule.

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WEPWI013

New Results of Development on High Efficiency High Gradient Superconducting RF Cavities

SRF, linac, niobium, photon

3518

R.L. Geng
JLab, Newport News, Virginia, USA
C. Adolphsen, Z. Li
SLAC, Menlo Park, California, USA
J.K. Hao, K.X. Liu
PKU, Beijing, People's Republic of China
H.Y. Zhao
Ningxia Orient Tantalum Industry Co., Ltd., Dawukou District, Shizuishan city, People's Republic of China

We report on the latest results of development on high efficiency high gradient superconducting radio frequency (SRF) cavities. Several 1-cell cavities made of large-grain niobium (Nb) were built, processed and tested. Two of these cavities are of the Low Surface Field (LSF) shape. Series of tests were carried out following controlled thermal cycling. Experiments toward zero-field cooling were carried out. The best experimentally achieved results are Eacc = 41 MV/m at Q0 = 6.5×10¹⁰ at 1.4 K by a 1-cell 1.3 GHz large-grain Nb TTF shape cavity and Eacc = 49 MV/m at Q0 = 1.5×1010 at 1.8 K by a 1-cell 1.5 GHz large-grain Nb CEBAF upgrade low-loss shape cavity.

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WEPWI015

BNL 56 MHz HOM Damper Prototype Fabrication at JLab

niobium, HOM, network, vacuum

3521

N.A. Huque, W.A. Clemens, E. Daly
JLab, Newport News, Virginia, USA
S. Bellavia, G.T. McIntyre, S.K. Seberg, Q. Wu
BNL, Upton, Long Island, New York, USA

A prototype Higher-Order Mode (HOM) Damper was fabricated at JLab for the Relativistic Heavy-Ion Collider’s (RHIC) 56 MHz cavity at Brookhaven National Laboratory (BNL). Primarily constructed from high RRR Niobium and Sapphire, the coaxial damper presented significant challenges in electron-beam welding (EBW), brazing and machining via acid etching. The results of the prototype operation brought about changes in the damper design, due to overheating braze alloys and possible multi-pacting. Five production HOM dampers are currently being fabricated at JLab. This paper outlines the challenges faced in the fabrication process, and the solutions put in place.

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WEPWI016

Investigation of Differential Surface Removal due to Electropolishing at JLab

simulation, cathode, radio-frequency, SRF

3525

F. Marhauser, J. Follkie, C.E. Reece
JLab, Newport News, Virginia, USA

Surface chemistry carried out for Superconducting Radio Frequency (SRF) cavities such as Buffered Chemical Polishing (BCP) and Electropolishing (EP) aims to uniformly remove the internal surface of a cavity along the entire structure and within each cell from equator to iris in order to obtain an equally etched surface. A uniform removal however is not readily achievable due to the complex fluid flow and varying temperatures of the acid mixture, which can lead to differential etching. This needs to be considered when envisaging a certain surface damage removal throughout the interior. The process-specific differential etching influences the target frequency set at the manufacturing stage as well as the field flatness and length of the as-built cavity. We report on analyses of JLab's present EP system using experimental data for six nine-cell cavities that have been processed recently in the frame of the LCLS-II high-Q development plan. In conjunction with numerical simulations, the differential etching and the impact on field flatness is assessed.

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WEPWI019

Quench Studies of Six High Temperature Nitrogen Doped 9 Cell Cavities for Use in the LCLS-II Baseline Prototype Cryo-module at Jefferson Laboratory

SRF, cryomodule, niobium, injection

3528

A.D. Palczewski, G.V. Eremeev, R.L. Geng, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Jefferson Lab (JLab) processed six nine-cell cavities as part of a small-scale production for LCLS-II cavity processing development utilizing the promising nitrogen-doping process. [1] Various nitrogen-doping recipes have been scrutinized to optimize process parameters with the aim to guarantee an unloaded quality factor (Q 0) of 2.7·10¹⁰ at an accelerating field (Eacc) of 16 MV/m at 2.0 K in the cryomodule. During the R&D phase the characteristic Q0 vs. Eacc performance curve of the cavities has been measured in JLab’s vertical test area at 2 K. The findings showed the characteristic rise of the Q0 with Eacc as expected from nitrogen-doping. Initially, five cavities achieved an average Q0 of 3.3·10¹⁰ at the limiting Eacc averaging to 16.8 MV/m, while one cavity experienced an early quench accompanied by an unusual Q 0 vs. Eacc curve. The project accounts for a cavity performance loss from the vertical dewar test (with or without the helium vessel) to the horizontal performance in a cryomodule, such that these results leave no save margin to the cryomodule specification. Consequently, a refinement of the nitrogen-doping has been initiated to guarantee an average quench field above 20 MV/m without impeding the Q 0. This paper covers the refinement work performed for each cavity, which depends on the initial results, as well as a quench analysis carried out before and after the rework during the vertical RF tests as far as applicable.

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WEPWI021

An Analysis of the Temperature and Field Dependence of the RF Surface Resistance of Nitrogen-Doped Niobium SRF Cavities with Respect to Existing Theoretical Models

niobium, SRF, site, superconductivity

3532

C.E. Reece, A.D. Palczewski
JLab, Newport News, Virginia, USA
B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177
Recent progress with the reduction of rf surface resistance (Rs) of niobium SRF cavities via the use of high temperature surface doping by nitrogen has opened a new regime for energy efficient accelerator applications. For particular doping conditions one observes dramatic decreases in Rs with increasing surface magnetic fields. The observed variations as a function of temperature may be analyzed in the context of recent theoretical treatments in hopes of gaining insight into the underlying beneficial mechanism of the nitrogen treatment. Systematic data sets of Q0 vs. Eacc vs. temperature acquired during the high Q0 R&D work of the past year will be compared with theoretical model predictions. *
* B. P. Xiao et al., Physica C: Superconductivity 490 (0), 26-31 (2013) and
A. Gurevich, PRL 113 (8), 087001 (2014)

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WEPWI028

Simulation Study Using an Injection Phase-locked Magnetron as an Alternative Source for SRF Accelerators

controls, injection, klystron, SRF

3544

H. Wang, T. E. Plawski, R.A. Rimmer
JLab, Newport News, Virginia, USA

As a drop-in replacement for the CEBAF CW klystron system, a 1497 MHz, CW type high efficiency magnetron using injection phase lock and amplitude variation is attractive. Amplitude control using magnetic field trimming and anode voltage modulation has been studied using analytical models and MATLAB/Simulink simulations. Since the 1497 MHz magnetron has not been built yet, previously measured characteristics of a 2.45GHz cooker magnetron are used as reference. The results of linear responses to the amplitude and phase control of a superconducting RF (SRF) cavity, and the expected overall benefit for the current CEBAF and future MEIC RF systems are presented in this paper.

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WEPWI029

Cavity Design, Fabrication and Test Performance of 750 MHz, 4-Rod Separators for CEBAF 4-Hall Beam Delivery System

simulation, coupling, hardware, target

3548

H. Wang, G. Cheng, L. Turlington, M.J. Wissmann
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A short version of the original CEBAF normal conducting 4-rod separator cavity has been developed into a 750MHz one * since the concept of simultaneous 4-hall operation for CEBAF is introduced **. This work has been advanced further based on the EM design optimization, bench measurement and by conducting RF-thermal coupled simulation using CST and ANSYS to confirm the cavity tuning and thermal performance. The cavity fabrication used matured technology like copper plating and machining. The cavity flanges, couplers, tuners and cooling channels adopted consistent/compatible hardware with the existing 500MHz cavities. The electromagnetic and thermal design simulations have greatly reduced the prototyping and bench tuning time of the first prototype. Four production cavities have reached a typical 1.94MV kick voltage or 3.0kW wall loss on each cavity after a minor multipactoring or no processing, 7.5% overhead power than the design specification.
* R. Kazimi et al., IPAC2013, Shanghai, China, pp 2896-2898.
** R. Kazimi, IPAC2013, Shanghai, China, pp 3502-3504.

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WEPWI030

Injector Cavities Fabrication, Vertical Test Performance and Primary Cryomodule Design

cryomodule, HOM, dipole, impedance

3551

H. Wang, G. Cheng, W.A. Clemens, G.K. Davis, K. Macha, R.B. Overton, D. Spell
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
After the electromagnetic design * and the mechanical design ** of a β=0.6, 2-cell elliptical SRF cavity, the cavity has been fabricated. Then both 2-cell and 7-cell cavities have been bench tuned to the target values of frequency, coupling external Q and field flatness. After buffer chemistry polishing (BCP) and high pressure rinses (HPR), Vertical 2K cavity test results have been satisfied the specifications and ready for the string assembly. We will report the cavity performance including Lorenz Force Detuning (LFD) and Higher Order Modes (HOM) damping data. Its integration with cavity tuners to the cryomodule design will be reported.
* H. Wang, etc., Proceeding of IPAC2013, Shanghai, China, WEPWO073.
** G. Cheng, etc., Proceeding of PAC2013, Pasadena, CA, WEPAC47.

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WEPWI032

Mechanical Properties of Niobium Cavities

niobium, SRF, electron, cryogenics

3554

G. Ciovati, P. Dhakal, J. Matalevich, G.R. Myneni
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.

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WEPWI033

Effects of Plasma Processing on Secondary Electron Yield of Niobium Samples

electron, plasma, gun, vacuum

3558

M. Basovic, S. Popović, M. Tomovic, L. Vušković
ODU, Norfolk, Virginia, USA
F. Čučkov, A. Samolov
University of Massachusetts Boston, Boston, Massachusetts, USA

Impurities deposited on the surface of Nb during both the forming and welding of accelerator cavities add to the imperfections of the sheet metal, which then affects the overall performance of the cavities. This leads to a drop in the Q factor and limits the maximum acceleration gradient achievable per unit length of the cavities. The performance can be improved either by adjusting the fabrication and preparation parameters, or by mitigating the effects of fabrication and preparation techniques used. We have developed the experimental setup to determine Secondary Electron Yield (SEY) from the surface of Nb samples. Our aim is to show the effect of plasma processing on the SEY of Nb. The setup measures the secondary electron energy distribution at various incident angles as measured between the electron beam and the surface of the sample. The goal is to determine the SEY on non-treated and plasma treated surface of electron beam welded samples. Here we describe the experimental setup, plasma treatment device, and fabrication and processing of the Nb samples.

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WEPWI034

Effects of Crab Cavities' Multipole Content in an Electron-Ion Collider

dipole, sextupole, proton, multipole

3561

A. Castilla, J.R. Delayen, T. Satogata
ODU, Norfolk, Virginia, USA
A. Castilla, J.R. Delayen, V.S. Morozov, T. Satogata
JLab, Newport News, Virginia, USA
A. Castilla
DCI-UG, León, Mexico

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The impact on the beam dynamics of the Medium Energy Electron-Ion Colider (MEIC) due to the multipole content of the 750 MHz crab cavity was studied using thin multipole elements for 6D phase space particle tracking in ELEGANT. Target values of the sextupole component for the cavity’s field expansion were used to perform preliminary studies on the proton beam stability when compared to the case of pure dipole content of the rf kicks. Finally, important effects on the beam sizes due to non-linear components of the crab cavities’ fields were identified and some criteria for their future study were proposed.

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WEPWI035

Beam Dynamics Studies of 499 MHz Superconducting RF-Dipole Deflecting Cavity System

dipole, emittance, multipole, superconducting-RF

3564

S.U. De Silva, K.E. Deitrick, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA

A 499 MHz deflecting cavity has been designed as a three-way beam spreader to separate an electron beam into 3 beams. The rf tests carried out on the superconducting rf-dipole cavity have demonstrated that a transverse voltage of 4.2 MV can be achieved with a single cavity. This paper discusses the beam dynamics on a deflecting structure operating in continuous-wave mode with a relativistic beam. The study includes the analysis on emittance growth, energy spread, and change in bunch size including effects due to field non-uniformities.

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WEPWI036

Design and Prototyping of a 400 MHz RF-dipole Crabbing Cavity for the LHC High-Luminosity Upgrade

dipole, cryomodule, luminosity, HOM

3568

S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
T.H. Nicol
Fermilab, Batavia, Illinois, USA

LHC High Luminosity Upgrade is in need of two crabbing systems that deflects the beam in both horizontal and vertical planes. The 400 MHz rf-dipole crabbing cavity system is capable of crabbing the proton beam in both planes. At present we are focusing our efforts on a complete crabbing system in the horizontal plane. Prior to LHC installation the crabbing system will be installed for beam test at SPS. The crabbing system consists of two rf-dipole cavities in the cryomodule. This paper discusses the electromagnetic design and mechanical properties of the rf-dipole crabbing system for SPS beam test.

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WEPWI037

Imperfection and Tolerance Analysis of HOM Couplers for ODU/SLAC 400 MHz Crabbing Cavity

HOM, impedance, dipole, luminosity

3572

S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
R.G. Olave
Old Dominion University, Norfolk, Virginia, USA

In preparation for the LHC High Luminosity upgrade, a 400 MHz crab cavity has been developed jointly at ODU/SLAC, including two higher order mode couplers designed to dampen the wakefields in order to comply with the impedance budget specified for the LHC system. During fabrication, assembly, and processing of the couplers, a number of imperfections may arise that could modify the higher order mode spectrum and the associated impedance for each mode. We present here a detailed study of the imperfections of the horizontal- and vertical- HOM couplers, and the associated allowed tolerances for manufacture, assembly and processing.

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WEPWI038

Temperature Mapping of Nitrogen-doped Niobium Superconducting Radiofrequency Cavities

niobium, SRF, radio-frequency, cryogenics

3575

J. Makita
ODU, Norfolk, Virginia, USA
G. Ciovati, P. Dhakal
JLab, Newport News, Virginia, USA

It was recently shown that diffusing nitrogen on the inner surface of superconducting radiofrequency (SRF) cavities at high temperature can improve the quality factor of the niobium cavity. However, a reduction of the quench field is also typically found. To better understand the location of rf losses and quench, we used a thermometry system to map the temperature of the outer surface of ingot Nb cavities after nitrogen doping and electropolishing. Surface temperature of the cavities was recorded while increasing the rf power and also during the quenching. The results of thermal mapping showed no precursor heating on the cavities and quenching to be ignited near the equator where the surface magnetic field is maximum. Hot-spots at the equator area during multipacting were also detected by thermal mapping.

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WEPWI039

Engineering Study of Crab Cavity HOM Couplers for LHC High Luminosity Upgrade

HOM, niobium, damping, luminosity

3578

H. Park, S.U. De Silva, J.R. Delayen, R.G. Olave
ODU, Norfolk, Virginia, USA
T. Capelli
CERN, Geneva, Switzerland
S.U. De Silva, J.R. Delayen, H. Park
JLab, Newport News, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
T.H. Nicol
Fermilab, Batavia, Illinois, USA
N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The LHC is planning to employ crab cavities for the high luminosity upgrade. Old Dominion University and SLAC National Laboratory are developing the crab cavity completed with the HOM damping couplers. The HOM couplers are coaxial type and perform over broad band up to 2 GHz. The amount of extracted power requires active cooling using liquid helium. The electromagnetic study has provided expected power dissipation on the coupler. Correlations between the fabrication tolerance and its damping performance have been studied and the results are providing guidelines on how to manufacture the HOM couplers. This paper summarizes the engineering studies; mechanical strength as a part of pressure system, thermal stability, and fabrication method to ensure the required tolerance.

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WEPWI040

Experiment and Results on Plasma Etching of SRF Cavities

plasma, SRF, niobium, ion

3581

J. Upadhyay, J.J. Peshl, S. Popović, L. Vušković
ODU, Norfolk, Virginia, USA
D.S. Im
Old Dominion University, Norfolk, Virginia, USA
H.L. Phillips, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

The inner surfaces of SRF cavities are currently chemically treated (etched or electro polished) to achieve the state of the art RF performance. We designed an apparatus and developed a method for plasma etching of the inner surface for SRF cavities. The process parameters (pressure, power, gas concentration, diameter and shape of the inner electrode, temperature and positive dc bias at inner electrode) are optimized for cylindrical geometry. The etch rate non-uniformity has been overcome by simultaneous translation of the gas point-of-entry and the inner electrode during the processing. A single cell SRF cavity has been centrifugally barrel polished, chemically etched and RF tested to establish a baseline performance. This cavity is plasma etched and RF tested afterwards. The effect of plasma etching on the RF performance of this cavity will be presented and discussed.

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WEPWI044

High-Power Magnetron Transmitter for the Electron Collider Ring of the MEIC Facility

controls, SRF, electron, injection

3587

G.M. Kazakevich
Euclid TechLabs, LLC, Solon, Ohio, USA
B.E. Chase, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
Y.S. Derbenev
JLab, Newport News, Virginia, USA

Operation of the 3-12 GeV electron collider 8-shape ring of the MEIC facility causes a Synchrotron Radiation (SR) of electrons in arcs with energy loss of ~20 kW/m at beam current of ~3 A. The total SR loss up to 2 MW per a revolution is presumed to compensate by Superconducting RF (SRF) accelerating cavities. To minimize the beam emittance, each individual SRF cavity is proposed to feed by an individual and independent RF source allowing a wide-band control in phase and power. Most efficient and less expensive in capital and maintenance costs the high-power transmitters based on magnetrons, injection-locked by phase-modulated signals, controlled in wide-band are proposed as the RF sources. The magnetron RF sources utilizing 2-cascade magnetrons allowing a wide-band phase and power control by the injection-locking phase-modulated signals were experimentally modelled by 2.45 GHz, CW, 1 kW magnetrons. Results of the modelling and adequacy of the transmitters for the SRF cavities are discussed in the presented article.

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WEPWI045

Status of Superconducting Traveling Wave Cavity for High Gradient Linac

accelerating-gradient, vacuum, cryogenics, feedback

3591

R.A. Kostin, P.V. Avrakhov, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
T.N. Khabiboulline, Y.M. Pischalnikov, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

The use of a travelling wave (TW) accelerating structure with a small phase advance per cell instead of standing wave may provide a significant increase of accelerating gradient in a superconducting linear accelerator. The TW section achieves an accelerating gradient 1.2-1.4 times larger than TESLA-shaped standing wave cavities for the same surface electric and magnetic fields. The final stage of a 3-cell superconducting travelling wave cavity development is presented. This cavity will be tested in travelling wave regime at cryogenic temperature.

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WEPWI046

Demonstration of Coaxial Coupling Scheme at 26 MV/m for 1.3 GHz TESLA-type SRF Cavities

coupling, niobium, SRF, acceleration

3594

Y. Xie, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
T.N. Khabiboulline, A. Lunin, V. Poloubotko, A.M. Rowe, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
J. Rathke
AES, Medford, New York, USA

Funding: Work sponsored by DOE SBIR Grant DE-SC0002479.
We will report the first successful rf test of a detachable coaxial coupler by Euclid Techlabs and Fermilab SRF development department. The coaxial coupling method has vast advantages compared with ordinary welded-on couplers. It totally eliminates coupler kicks and it is detachable and easy to clean. We reached 26 MV/m (no hard quench limit) with a quarter-wave detachable coaxial coupler. This is also a demonstration of the highest field gradient ever reached with a superconducting joint.

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WEPWI050

SRF and RF Systems for LEReC Linac

SRF, gun, electron, booster

3600

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, A.V. Fedotov, G.T. McIntyre, S. Polizzo, K.S. Smith, R. Than, J.E. Tuozzolo, Q. Wu, B. P. Xiao, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosity at low energies. It will consist of a short electron linac and two cooling sections, one for blue and one for yellow beams. For the first stage of the project, LEReC-1, we will to install a 704 MHz superconducting RF cavity and two normal conducting cavities operating at 704 MHz and 2.1 GHz. The SRF cavity will boost the electron beam energy up to 2 MeV. The warm cavities will be used to correct the energy spread introduced in the SRF cavity. The paper describes layouts of the SRF and RF systems, their parameters and status.

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WEPWI051

Update on the CeC POP 704 MHz 5-Cell Cavity Cryomodule Design and Fabrication

SRF, cryomodule, electron, linac

3603

J.C. Brutus, S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, I. Pinayev, J. Skaritka, L. Snydstrup, R. Than, J.E. Tuozzolo, W. Xu
BNL, Upton, Long Island, New York, USA
S.M. Gerbick, M.P. Kelly, T. Reid
ANL, Argonne, USA
T.L. Grimm, R. Jecks, J.A. Yancey
Niowave, Inc., Lansing, Michigan, USA
Y. Huang
Fermilab, Batavia, Illinois, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
A 5-cell SRF cavity operating at 704 MHz will be used for the Coherent Electron Cooling Proof of Principle (CeC PoP) system currently under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The CeC PoP experiment will demonstrate the ability of relativistic electrons to cool a single bunch of heavy ions in RHIC. The cavity will accelerate 2 MeV electrons from a 112 MHz SRF gun up to 22 MeV. Novel mechanical designs, including the helium vessel, vacuum vessel, tuner mechanism, and FPC are presented. This paper provides an overview of the design, the project status and schedule of the 704 MHz 5-cell SRF for the CeC PoP experiment.
.

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WEPWI052

Commissioning and Early Operation Experience of the NSLS-II Storage Ring RF System

operation, synchrotron, storage-ring, klystron

3606

F. Gao, J. Cupolo, P. Davila, T. Dilgen, W.K. Gash, B. Holub, J.G. Kulpin, J. Papu, G. Ramirez, V. Ravindranath, B. Rose, J. Rose, R. Sikora, J. Tagger, M. Yeddulla
BNL, Upton, Long Island, New York, USA

The National Synchrotron Light Source II (NSLS-II) is a 3 GeV X-ray user facility commissioned in 2014. The storage ring RF system, essential for replenishing energy loss per turn of the electrons, consists of digital low level RF controllers, 310 kW CW klystron transmitters, CESR-B type superconducting cavities, as well as a supporting cryogenic system. Here we will report on RF commissioning and early operation experience of the system for beam current up to 200 mA.

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WEPWI055

Commissioning and Early Operation for the NSLS-II Booster RF System

booster, extraction, synchrotron, operation

3615

C. Marques, J. Cupolo, P. Davila, F. Gao, A. Goel, B. Holub, J.G. Kulpin, K. McDonald, J. Oliva, J. Papu, G. Ramirez, J. Rose, R. Sikora, C. Sorrentino, N.A. Towne
BNL, Upton, Long Island, New York, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-SC0012704.
The National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory (BNL) is a third generation 3GeV, 500mA synchrotron light source. We discuss the booster synchrotron RF system responsible for providing power to accelerate an electron beam from 200MeV to 3GeV. The RF system design and construction are complete and is currently in the operational phase of the NSLS-II project. Preliminary operational data is also discussed.

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WEPWI058

The NSLS-II RF Cryogenic System

controls, cryogenics, PLC, operation

3624

J. Rose, T. Dilgen, W.K. Gash, J. Gosman, J. Papu, R. Sikora
BNL, Upton, Long Island, New York, USA
Y. Jia
Linde BOC Process Plants LLC, Tulsa, Oklahoma, USA
C.M. Monroe
Monroe Brothers Ltd., Moreton-in-Marsh, United Kingdom
V. Ravindranath
SLAC, Menlo Park, California, USA
H. Wilhelm
Linde Kryotechnik AG, Pfungen, Switzerland

Funding: Work supported by DOE contract DE-SC0012704
The National Synchrotron Light Source II is a 3 GeV X-ray user facility commissioned in 2014. A new helium refrigerator system has been installed and commissioned to support the superconducting RF cavities in the storage ring. Special care was taken to provide very stable helium and LN2 pressures and flow rates to minimize microphonics and thermal effects at the cavities. Details of the system design along with commissioning and early operations data will be presented.

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WEPWI059

Higher Order Mode Filter Design for Double Quarter Wave Crab Cavity for the LHC High Luminosity Upgrade

HOM, impedance, luminosity, coupling

3627

B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, S. Verdú-Andrés, Q. Wu
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
G. Burt, B.D.S. Hall
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
G. Burt
Lancaster University, Lancaster, United Kingdom
R. Calaga, O. Capatina
CERN, Geneva, Switzerland
T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Work partly supported by US LARP, by US DOE under contract No. DE-AC02-05CH11231 and through BSA under contract No. DE-AC02-98CH10886. Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404.
A double quarter wave crab cavity (DQWCC) was designed for the Large Hadron Collider (LHC) luminosity upgrade. A compact Higher Order Mode (HOM) filter with wide stop band at the deflecting mode is developed for this cavity. Multi-physics finite element simulation results are presented. The integration of this design to the cavity cryomodule is described.

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WEPWI060

Cryogenic Test of Double Quarter Wave Crab Cavity for the LHC High Luminosity Upgrade

cryogenics, luminosity, radiation, higher-order-mode

3630

B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, C. Cullen, L.R. Hammons, C. Marques, J. Skaritka, S. Verdú-Andrés, Q. Wu
BNL, Upton, Long Island, New York, USA
L. Alberty, R. Calaga, O. Capatina
CERN, Geneva, Switzerland
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
Z. Li
SLAC, Menlo Park, California, USA

Funding: Work partly supported by US LARP, by US DOE under contract No. DE-AC02-05CH11231 and through BSA under contract No. DE-AC02-98CH10886. Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404.
A Proof-of-Principle (PoP) Double Quarter Wave Crab Cavity (DQWCC) was designed and fabricated for the Large Hadron Collider (LHC) luminosity upgrade. A vertical cryogenic test has been done at Brookhaven National Lab (BNL). The cavity achieved 4.5 MV deflecting voltage with a quality factor above 3×10⁹. We report the test results of this design.

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WEPWI061

Design of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac

impedance, resonance, electron, simulation

3634

B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, A.V. Fedotov, G.T. McIntyre, K.S. Smith, J.E. Tuozzolo, Q. Wu, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energey RHIC electron Cooler (LEReC) is currently under development at BNL. Two normal conducting cavities, a single cell 704 MHz cavity and a 3 cell 2.1 GHz third harmonic cavity, will be used in LEReC for bunch stretching and energy spread correction. In this paper we report the design of these two cavities.

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THXB1

CEBAF SRF Performance during Initial 12 GeV Commissioning

cryomodule, controls, klystron, operation

3638

R. Bachimanchi, T.L. Allison, E. Daly, M.A. Drury, C. Hovater, G.E. Lahti, C.I. Mounts, R.M. Nelson, T. E. Plawski
JLab, Newport News, Virginia, USA

The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of eleven new 100 MV cryomodules (88 cavities). The superconducting RF cavities are designed to operate CW at an accelerating gradient of 19.3 MV/m with a QL of 3×107. Not all the cavities were operated at the minimum gradient of 19.3 MV/m with the beam. Though the initial 12 GeV milestones were achieved during the initial commissioning of CEBAF, there are still some issues to be addressed for long term reliable operation of these modules. This paper reports the operational experiences during the initial commissioning and the path forward to improve the performance of C100 (100 MV) modules.

Slides THXB1 [5.595 MB]

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THXB2

Crab Cavities: Past, Present, and Future of a Challenging Device

luminosity, collider, HOM, operation

3643

Q. Wu
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with LARP and the U.S. Department of Energy and EU FP7 HiLumi LHC - Grant Agreement 284404
In two-ring facilities operating with a crossing angle collision scheme, the luminosity can be limited due to incomplete overlap of the colliding bunches. Crab cavities are introduced to restore head-on collisions by providing destined opposite deflection to the head and tail of the bunch. Luminosity increase has been demonstrated at KEKB with global crab crossing, and the Large Hardron Collider (LHC) at CERN is currently designing local crab crossing for the Hi-Lumi upgrade. Future colliders may investigate both approaches. This paper reviews the challenges in the technology and implementation of crab cavities, discusses experience in past colliders, ongoing R&D and proposed implementations for future facilities such as HL-LHC, CLIC, ILC, and eRHIC/MEIC.

Slides THXB2 [4.307 MB]

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THPF006

Design and Manufacturing Status of the IFMIF-LIPAC SRF LINAC

cryomodule, vacuum, linac, solenoid

3686

H. Dzitko
CEA, Pontfaverger-Moronvilliers, France
N. Bazin, A. Bruniquel, P. Charon, P. Gastinel, P. Hardy, H. Jenhani, J. Neyret, O. Piquet, J. Relland, N. Sellami
CEA/IRFU, Gif-sur-Yvette, France
S. Chel, G. Devanz, G. Disset, V.M. Hennion, B. Renard
CEA/DSM/IRFU, France
D. Gex, G. Phillips
F4E, Germany
D. Regidor, F. Toral
CIEMAT, Madrid, Spain

The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy neutron flux for testing of candidate materials for use in fusion energy reactors. The first phase of the project, called EVEDA (Engineering Validation and Engineering Design Activities) aims at validating the technical options by constructing an accelerator prototype, called LIPAc (Linear IFMIF Prototype Accelerator) whose construction has begun. It is a full scale of one of the IFMIF accelerator from the injector to the first cryomodule. The cryomodule contains all the necessary equipment to transport and accelerate a 125 mA deuteron beam from an input energy of 5 MeV up to output energy of 9 MeV. It consists of a horizontal vacuum tank approximately 6 m long, 3 m high and 2.0 m wide, and includes 8 superconducting HWRs working at 175 MHz and at 4.45 K for beam acceleration. 8 Power Couplers provide RF power to the cavities up to 70 kW CW in the LIPAc case and 200 kW CW in the IFMIF case, with 8 Solenoid Packages acting as focusing elements. This paper gives an overview of the progress, achievements and status of the IFMIF SRF LINAC.

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THPF011

Status of the FAIR Proton Linac

linac, rfq, proton, diagnostics

3702

R. M. Brodhage, M. Kaiser, W. Vinzenz, M. Vossberg
GSI, Darmstadt, Germany
U. Ratzinger
IAP, Frankfurt am Main, Germany

For the research program with cooled antiprotons at FAIR a dedicated 70 MeV, 70 mA proton injector is required. The main acceleration of this room temperature linac will be provided by six CH cavities operated at 325 MHz. Within the last years, the assembly and tuning of the first power prototype was finished. The cavity was tested with a preliminary aluminum drift tube structure, which was used for precise frequency and field tuning. Afterwards, the final drift tube structure has been welded inside the main tanks and the galvanic copper plating has taken place at GSI workshops. This paper will report on the recent advances with the prototype as well as on the current status of the overall p-Linac project.

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THPF013

UNILAC Proton Injector Operation for FAIR

proton, ion, linac, operation

3709

M. Heilmann, A. Adonin, S. Appel, W.A. Barth, P. Gerhard, F. Heymach, R. Hollinger, W. Vinzenz, H. Vormann, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth
HIM, Mainz, Germany

The pbar physics program at the Facility for Antiproton and Ion Research (FAIR) requires a high number of cooled pbars per hour. The FAIR proton injector with coupled CH-cavities will provide for a high intensity (35 mA) pulsed 70 MeV proton beam at a repetition rate of 4 Hz. The recent heavy ion UNIversal Linear Accelerator (UNILAC) at GSI is able to deliver proton as well as heavy ion beams for injection into the FAIR-synchrotrons. Recently GSI UNILAC could provide for a two orders of magnitude higher proton beam current in routine operation. A hydrocarbon beam (CH3) from the MUCIS ion source was accelerated inside High Current Injector and cracked in a supersonic nitrogen gas jet into stripped protons and carbon ions. A new proton beam intensities record (3 mA) could be achieved during machine experiments in October 2014. Potentially up to 25% of the FAIR proton beam performance is achievable at a maximum UNILAC beam energy of 20 MeV and a repetition rate of 4 Hz. The UNILAC can be used as a high performance proton injector for initial FAIR-commissioning and as a redundant option for the first FAIR-experiments.

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THPF014

325 MHz High Power RF Coupler for the CH-Cavities of the FAIR p-LINAC

coupling, linac, proton, simulation

3712

F. Maimone, R. M. Brodhage, M. Kaiser, W. Vinzenz, M. Vossberg
GSI, Darmstadt, Germany

In order to supply the input RF power to the Cross-bar H-mode (CH) cavities of the p-LINAC for FAIR an inductive RF coupler has been studied. The designed RF coupler, and its water cooled inductive loop, has to withstand up to a 3 MW pulsed power (at 325 MHz). At GSI a prototype has been manufactured and tests were performed. The prototype of the designed high power RF coupler is presented together with the results of the coupling measurements at the CH-prototype cavity.

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THPF019

Status and First Measurement Results for a High Gradient CH-Cavity

linac, ion, resonance, operation

3724

A. Almomani, U. Ratzinger
IAP, Frankfurt am Main, Germany

Funding: BMBF, contract no. 05P12RFRB9
This pulsed linac activity aims on compact designs and on a considerable increase of the voltage gain per meter. A high gradient CH-cavity operated at 325 MHz was developed at IAP-Frankfurt. The mean effective accelerating field for this cavity is expected well above 10 MV/m at β = 0.164. This cavity is developed within a funded project. The results might influence the rebuilt of the UNILAC-Alvarez section, aiming to achieve the beam intensities specified for the GSI - FAIR project (15 mA U²⁸⁺). Another motivation is the development of an efficient pulsed ion accelerator for significantly higher energies like 60 AMeV. The new GSI 3 MW Thales klystron test stand will be used for the cavity RF power tests. Detailed studies on two different types of copper plating will be performed with this cavity.

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THPF021

Structural, Mechanical and RF Measurements on the Superconducting 217 MHz CH Cavity for the CW Demonstrator at GSI

simulation, resonance, niobium, operation

3730

F.D. Dziuba, M. Amberg, M. Basten, M. Busch, H. Podlech
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher, W.A. Barth, S. Mickat
HIM, Mainz, Germany
K. Aulenbacher
IKP, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

Funding: Work supported by HIM, GSI, BMBF Contr. No. 05P12RFRBL
Together with the new horizontal cryomodule and two superconducting (sc) 9.5 T solenoids the sc 217 MHz Crossbar-H-mode (CH) cavity represents the continuous wave (cw) demonstrator and brings sc rf technology to GSI. A reliable operability of the sc CH cavity is one major goal of the demonstrator project. Furthermore, the successful beam operation of the demonstrator will be a milestone on the way to a new sc cw linac at GSI for a competitive production of Super Heavy Elements (SHE) in the future. The production of the cryomodule and the solenoids is almost finished while the cavity has been completed except for the helium vessel. In this paper structural mechanical as well as related rf measurements on the sc 217 MHz CH cavity are presented.

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THPF025

Beam Dynamics for the SC CW Heavy Ion LINAC at GSI

linac, ion, heavy-ion, emittance

3742

M. Schwarz, M. Amberg, M. Basten, F.D. Dziuba, H. Podlech, U. Ratzinger, R. Tiede
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, V. Gettmann, M. Heilmann, S. Mickat, A. Orzhekhovskaya, S. Yaramyshev
GSI, Darmstadt, Germany

Funding: Work supported by BMBF contr. No. 05P12RFRBL
For future experiments with heavy ions near the coulomb barrier within the SHE (super-heavy elements) research project a multi-stage R&D program of GSI, HIM and IAP is currently in progress*. It aims at developing a superconducting (sc) continuous wave (cw) LINAC with multiple CH cavities as key components downstream the High Charge Injector (HLI) at GSI. The beam dynamics concept is based on EQUUS (equidistant multigap structure) constant-beta cavities. Advantages of its periodicity are a high simulation accuracy, easy manufacturing and tuning with minimized costs as well as a straightforward energy variation. The next milestone will be a full performance beam test of the first LINAC section, comprising two solenoids and a 15-gap CH cavity inside a cryostat (Demonstrator).
*W. Barth et al., ‘‘Further R&D for a new Superconducting cw Heavy Ion LINAC@GSI'', THPME004, IPAC'14, Dresden, Germany (2014)

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THPF026

Development of a 325 MHz Ladder-RFQ of the 4-Rod Type

rfq, simulation, proton, linac

3745

M. Schütt, U. Ratzinger
IAP, Frankfurt am Main, Germany
R. M. Brodhage
GSI, Darmstadt, Germany

For the research program with cooled antiprotons at FAIR a dedicated 70 MeV, 70 mA proton injector is required. In the low energy section, between the Ion Source and the main linac an RFQ will be used. The 325 MHz RFQ will accelerate protons from 95 keV to 3.0 MeV. This particular high frequency for an RFQ creates difficulties, which are challenging in developing this cavity. In order to define a satisfactory geometrical configuration for this resonator, both from the RF and the mechanical point of view, different designs have been examined and compared. Very promising results have been reached with a ladder type RFQ, which has been investigated since 2013. We present recent 3D simulations of the general layout and of a complete cavity demonstrating the power of a ladder type RFQ as well as measurements of a 0,8 m prototype RFQ, which was manufactured in late 2014 and designed for RF power and vacuum tests. We will outline a possible RF layout for the RFQ within the new FAIR proton injector and highlight the mechanical advantages.

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THPF027

Ten Gap Model of a New Alvarez DTL Cavity at GSI

simulation, ion, DTL, impedance

3748

A. Seibel, O.K. Kester
IAP, Frankfurt am Main, Germany
X. Du, L. Groening, S. Mickat
GSI, Darmstadt, Germany

In order to meet the challenges of the FAIR project at GSI requiring highest beam intensities an upgrade of the existing Universal Linear Accelerator (UNILAC) is planned. The 10⁸ MHz cavities will be replaced by new rf-structures of the same frequency. Simulations are done to improve the rf-properties. The geometry of the drift tubes is to be changed to a smoother curvature to reach a homogeneous surface field distribution and higher shunt impedances. To check the necessity of cooling channels, simulations on the temperature distribution at the drift tubes and stems are conducted. A test bench for low power rf-measurements with a 10 gap aluminum model (scale 1:3) is under construction. The modular mechanical design of the model will allow probing experimentally a wide range of drift tube and stem geometries. With the bead pull method the electrical field distribution will be measured as well as the field stability with respect to parasitic modes. Additionally, appropriate locations along the cavity to place fixed and dynamic rf-frequency tuners will be determined.

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THPF033

The First Operation of 56 MHz SRF Cavity in RHIC

HOM, operation, SRF, cryomodule

3767

Q. Wu, S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, L. DeSanto, D. Goldberg, M. Harvey, T. Hayes, G.T. McIntyre, K. Mernick, P. Orfin, S.K. Seberg, F. Severino, K.S. Smith, R. Than, A. Zaltsman
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A 56 MHz superconducting RF cavity has been designed, fabricated and installed in the Relativistic Heavy Ion Collider (RHIC). The cavity operated at 4.4 K with a “quiet helium source” to isolate the cavity from environmental acoustic noise. The cavity is a beam driven quarter wave resonator. It is detuned and damped during injection and acceleration cycles and is brought to operation only at store energy. For a first test operation, the cavity voltage was stabilized at 300 kV with full beam current. Within both Au + Au and asymmetrical Au + He3 collisions, luminosity improvement was detected from direct measurement, and the hourglass effect was reduced. One higher order mode (HOM) coupler was installed on the cavity. We report in this paper on our measurement of a broadband HOM spectrum excited by the Au beam.

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THPF042

Rectlinear Cooling Scheme for Bright Muon Sources

emittance, simulation, space-charge, lattice

3792

D. Stratakis
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Contract No, DE-AC02-07CH11359 with the US Department of Energy.
A fast cooling technique is described that simultaneously reduces all six phase-space dimensions of a charged particle beam. In this process, cooling is accomplished by reducing the beam momentum through ionization energy loss in absorbers and replenishing the momentum loss only in the longitudinal direction rf cavities. In this work we describe its main features and describe the main results.

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THPF049

The Simulation and Manufacture of the Room Temperature Cross-bar H Type Drift Tube Linac

impedance, DTL, proton, rfq

3811

J.H. Li
China Institute of Atomic Energy, Beijing, People's Republic of China
Z. Li
SCU, Chengdu, People's Republic of China

Funding: This work is supported by the National Natural Science Foundation of China (NSFC).
The room temperature Cross-bar H Type Drift Tube Linac (CH-DTL) is one of the candidate acceleration structures working in CW mode. In order to optimize the parameters, the 3 dimensional electromagnetic field of the CH-DTL cavity is simulated. The method of parameter sweeping with constraint variable is better than the method of parameter sweeping with only one variable during the optimization. In order to simplify the manufacture, the drift tube surface can be designed as spherical shape. The effective shunt impedance of the CH-DTL cavity with cylinder end cup is better than that with cone cup.

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THPF055

Status of the Superconducting Cavity Development at IHEP for the CADS Linac

linac, SRF, operation, proton

3824

F.S. He, J.P. Dai, J. Dai, X. Huang, L.H. Li, Z.Q. Li, Q. Ma, Z.H. Mi, B. Ni, W.M. Pan, X.H. Peng, T. Qi, P. Sha, G.W. Wang, Q.Y. Wang, Z. Xue, X.Y. Zhang, G.Y. Zhao
IHEP, Beijing, People's Republic of China
H. Huang, H.Y. Lin
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

IHEP (Institute of High Energy Physics) is developing a CW 10MeV proton injector and part of the 25MeV main linac for the CADS project. 14 SRF (superconducting radio frequency) spoke-012 cavities for the injector, as well as 6 SRF spoke-021 cavities for the main linac are to be beam commissioned before middle of 2016; meanwhile, VT (vertical test) of two more types of prototype cavities are to be finished with 2015, for the future phases of the project. In this paper, the VT statistics of 10 spoke012 cavities, 4 spoke021 cavities, and a 5-cell β0.82 elliptical cavity are reported; the cavity performance during beam commissioning of the TCM (test cryomodule) is reported as well.

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THPF062

CADS 650 MHz β=0.63 Elliptical Cavity Study

HOM, linac, proton, resonance

3836

L.J. Wen, Y. He, Y.M. Li, S.H. Zhang
IMP/CAS, Lanzhou, People's Republic of China

The China Accelerator Driven Sub-critical System (CADS) is a high intensity proton facility to dispose of nuclear waste and generate electric power. CADS is based on 1.5 GeV, 10mA CW superconducting (SC) linac as a driver. The high-energy section of the linac is composed of two families of SC elliptical cavities which are designed for the geometrical beta 0.63 and 0.82. In this paper, the 650 MHz β=0.63 SC elliptical cavity was studied, including cavity optimization, multipacting, high order modes (HOM) and generator RF power calculation.

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THPF069

The Early Results of the Vertical Test for β=0.12 HWR at RISP

coupling, vacuum, cryogenics, niobium

3839

G.-T. Park, H.J. Cha, H.C. Jung, H. Kim, W.K. Kim, Y.J.K. Kim
IBS, Daejeon, Republic of Korea

At RISP, we are planning to perform the vertical test of the β=0.12 half wave resonator. We report our progress on the preparation of the test including the cryogenic system, the RF system, the control and data acquisition system, and the radiation shields. We had the first few occaaisions of the cool down and various measurements at a low gradient. Out preliminary result on the Q₀-E_acc excitation curve will be given.

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THPF070

Prototyping Progress of SSR1 Single Spoke Resonator for RAON

target, simulation, vacuum, ion

3842

H.J. Cha, H. Kim, H.J. Kim, W.K. Kim, G.-T. Park
IBS, Daejeon, Republic of Korea

The fabrication of prototypes for four different types of superconducting cavities (QWR, HWR, SSR1, and SSR2) for the Korean heavy ion accelerator, “RAON” is in progress. In this presentation, we report the current status of the SSR1 cavity (β=0.3 and f=325 MHz) prototype fabrication based on the technical designs. The simulation results on the target frequency determination for the clamp-up test of the prototype are also given.

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THPF072

Beam Optics of RISP Linac using Dynac Code

linac, simulation, rfq, target

3845

J.-H. Jang, I.S. Hong, H. Jang, D. Jeon, H. Jin, H.J. Kim
IBS, Daejeon, Republic of Korea

Funding: This work was supported by the Rare Isotope Science Project of Institute for Basic Science funded by Ministry of Science, ICT and Future Planning.
The RISP (Rare Isotope Science Project) is developing a superconducting linac which accelerates uranium beams up to 200MeV/u with the beam power of 400kW. The linac consists of an injector which includes an ECR ion source and an RFQ, and superconducting cavities which include QWR (Quarter Wave Resonator), HWR (Half Wave Resonator), and SSR (Single Spoke Resonator). Up to HWR, two charge state beams will be accelerated to achieve the required beam current and then five charge state beams will be used to obtain the higher acceleration efficiency. In this work, we performed the beam optics calculation by using a beam dynamics code DYNAC in order to study a possibility of the code as an online model. We compared the results with the calculation in the baseline design by TRACK code.

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THPF074

Progress on Superconducting Linac for the RAON Heavy Ion Accelerator

linac, cryomodule, ion, electron

3851

H.J. Kim, H.C. Jung, W.K. Kim
IBS, Daejeon, Republic of Korea

The RISP (Rare Isotope Science Project) has been proposed as a multi-purpose accelerator facility for providing beams of exotic rare isotopes of various energies. It can deliver ions from proton to Uranium. Proton and Uranium beams are accelerated upto 600 MeV and 200 MeV/u respectively. The facility consists of three superconducting linacs of which superconducting cavities are independently phased. Requirement of the linac design is especially high for acceleration of multiple charge beams. In this paper, we present the RISP linac design, the prototyping of superconducting cavity and cryomodule.

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THPF076

Thermal and Structural Analysis of the 72.75 MHz LINCE RFQ

rfq, simulation, software, controls

3857

A.K. Orduz, A. Berjillos, C. Bonțoiu, J.A. Dueñas, I. Martel
University of Huelva, Huelva, Spain
A. Garbayo
AVS, Elgoibar, Spain

Funding: Work partially supported by the Spanish Government (MINECO-CDTI) under program FEDER INTERCONNECTA.
The 72.75 MHz LINCE RFQ is designed to function at room temperature. Effective operation of the RFQ cavity requires efficient water cooling in order to dissipate significant resistive power non-uniformly distributed on the copper walls and vanes. This amounts to about 10 kWfor one 0.5m long RFQ section. Cylindrical cooling channels have been designed and optimized by varying their diameter and position in order to minimize the frequency shift generated by thermal displacements. The article reports results of power loss simulations coupled with electromagnetic modelling studies and their consequences on the RFQ performance in terms of resonant frequency and thermal deformations.

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THPF077

Proposal for a 72.75 MHz RFQ for the LINCE Accelerator Complex

rfq, simulation, pick-up, Windows

3861

A.K. Orduz, A. Berjillos, C. Bonțoiu, J.A. Dueñas, I. Martel
University of Huelva, Huelva, Spain
A. Garbayo
AVS, Elgoibar, Spain

Funding: Work partially supported by the Spanish Government (MINECO-CDTI) under program FEDER INTERCONNECTA
The low-energy part of the LINCE facility can be based on a 72.75MHz normal-conducting RFQ designed to give a 450 keV/u boost for A/Q=7 ions in about 5m length. The vanes have been electromagnetically designed to accommodate dedicated RF windows producing effective separation of the RFQ modes in an octagonal-shaped resonance chamber. This article outlines the optimization of the quality factor of the cavity by using numerical methods for electromagnetic calculations. Experimental results of RF test carried out on a prototype are also discussed.

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THPF084

ProTec - A Normal-conducting Cyclinac for Proton Therapy Research and Radioisotope Production

cyclotron, proton, linac, accelerating-gradient

3883

R. Apsimon, G. Burt, S. Pitman
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
A. Degiovanni
CERN, Geneva, Switzerland
J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
H.L. Owen
UMAN, Manchester, United Kingdom

The ProTec cyclinac proposes the use of a 24 MeV high-current cyclotron to inject protons into a normal-conducting linac pulsed at up to 1 kHz to give energies up to 150 MeV. As well as being able to produce radioisotopes such as 99mTc, the cyclinac can also provide protons at higher energy with beam properties relevant for proton therapy research. In this paper we present a comparison of linac designs in which S-band structures are used at lower energies, prior to injection into a high-gradient X-band structure; issues such as beam capture and transmission are evaluated.

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THPF090

Status and Plans for the Upgrade of the CERN PS Booster

injection, proton, booster, hardware

3905

K. Hanke, D. Aguglia, M.E. Angoletta, W. Bartmann, C. Bedel, E. Benedetto, S. Bertolasi, C. Bertone, J. Betz, T.W. Birtwistle, A. Blas, J. Borburgh, C. Bracco, A.C. Butterworth, E. Carlier, S. Chemli, P. Dahlen, A. Dallocchio, G.P. Di Giovanni, T. Dobers, A. Findlay, R. Froeschl, A. Funken, S. Gabourin, J.L. Grenard, D. Grenier, J. Hansen, D. Hay, J.-M. Lacroix, P. Le Roux, L.A. Lopez Hernandez, C. Martin, A. Masi, B. Mikulec, Y. Muttoni, A. Newborough, D. Nisbet, M.R. Obrecht, M.M. Paoluzzi, S. Pittet, B. Puccio, J. Tan, J. Vollaire, W.J.M. Weterings
CERN, Geneva, Switzerland

CERN’s Proton Synchrotron Booster (PSB) is undergoing a major upgrade program in the frame of the LHC Injectors Upgrade (LIU) project. During the first long LHC shutdown (LS1) some parts of the upgrade have already been implemented, and the machine has been successfully re-commissioned. More work is planned for the upcoming end-of-year technical stops, notably in 2016/17, while most of the upgrade is planned to take place during the second long LHC shutdown (LS2). We report on the upgrade items already completed and commissioned, the first Run 2 beam performance and give a status of the ongoing design and integration work.

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THPF103

Current Status of the SANAEM RFQ Accelerator Beamline

rfq, plasma, proton, simulation

3952

G. Turemen, B. Yasatekin
Ankara University, Faculty of Sciences, Ankara, Turkey
Y. Akgun, A.S. Bolukdemir
TAEK, Ankara, Turkey
A. Alacakir
SNRTC, Ankara, Turkey
A. Bozbey, A. Sahin
TOBB ETU, Ankara, Turkey
S. Erhan
UCLA, Los Angeles, California, USA
Ö. Mete
UMAN, Manchester, United Kingdom
S. Ogur, V. Yildiz
Bogazici University, Bebek / Istanbul, Turkey
S. Oz, A. Ozbey, H. Yildiz
Istanbul University, Istanbul, Turkey
G. Unel
UCI, Irvine, California, USA
F. Yaman
IZTECH, Izmir, Turkey

The design and production of the proton beamline of SPP, which aims to educate accelerator physicists and serve as particle accelerator technologies test bench, continues at TAEK-SANAEM as a multi-phase project. For the first phase, the 20 keV protons will be accelerated to 1.3 MeV by a single piece RFQ. Currently, the beam current and stability tests are ongoing for the Inductively Coupled Plasma ion source and the measured magnetic field maps of the Low Energy Beam Transport solenoids are being matched to the RFQ acceptance with various beam configurations of the ion source by using computer simulations. The production of the RFQ cavity was started by using high grade aluminum material which will be subsequently coated by Copper to reduce the RF losses. The installation of the low energy diagnostics box was also completed. On the RF side, the development of the hybrid power supply based on solid state and tetrode amplifiers continues. All RF transmission components are already produced with the exception of the circulator and the power coupling antenna which are in the manufacture and design phases, respectively. The acceptance tests of the produced RF components are ongoing. This work summarizes the design, production and test phases of the above mentioned SPP proton beamline components.

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THPF106

Review of Linac Upgrade Options for the ISIS Spallation Neutron Source

linac, DTL, neutron, proton

3962

D.C. Plostinar, C.R. Prior, G.H. Rees
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

The ISIS Spallation Neutron Source at Rutherford Appleton Laboratory has recently celebrated 30 years of neutron production. However, with increasing demand for improved reliability and higher beam power it has become clear that a machine upgrade is necessary in the medium to long term. One of the upgrade options is to replace the existing 70 MeV H⁻ injector. In this paper we review the ongoing upgrade programme and highlight three linac upgrade scenarios now under study. The first option is to keep the existing infrastructure and replace the current linac with a higher frequency, more efficient machine. This would allow energies in excess of 100 MeV to be achieved in the same tunnel length. A second option is to replace the current linac with a new 180 MeV linac, requiring a new tunnel. A third option is part of a larger upgrade scenario and involves the construction of an 800 MeV superconducting linac.

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THPF113

Energy Spread of the Proton Beam in the Fermilab Booster at Its Injection Energy

booster, injection, proton, simulation

3979

C.M. Bhat, B.E. Chase, S. Chaurize, F.G. Garcia, W. Pellico, K. Seiya, T. Sullivan, A.K. Triplett
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
We have measured the total energy spread (99% energy spread) of the Booster beam at its injection energy of 400 MeV by three different methods - 1) creating a notch of about 40 nsec wide in the beam immediately after multiple turn injection and measuring the slippage time required for high and low momentum particles for a grazing touch in line-charge distribution, 2) injecting partial turn beam and letting it to debunch, and 3) comparing the beam profile monitor data with predictions from MAD simulations for the 400 MeV injection beam line. The measurements are repeated under varieties of conditions of RF systems in the ring and in the beam transfer line.

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THPF129

The MICE Demonstration of Lonization Cooling

lattice, emittance, acceleration, radiation

4023

J. Pasternak, C. Hunt, J.-B. Lagrange, K.R. Long
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
V. Blackmore
Imperial College of Science and Technology, London, United Kingdom
N.A. Collomb
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
V.C. Palladino
INFN-Napoli, Napoli, Italy
R. Preece, J.S. Tarrant
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
C.T. Rogers
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
P. Snopok
Fermilab, Batavia, Illinois, USA

Funding: SFTC, DOE, NSF, INFN, CHIPP and more
Muon beams of low emittance provide the basis for the intense, well-characterised neutrino beams necessary to elucidate the physics of flavour at the Neutrino Factory and to provide lepton-antilepton collisions at energies of up to several TeV at the Muon Collider. The International Muon Ionization Cooling Experiment (MICE) will demonstrate ionization cooling, the technique by which it is proposed to reduce the phase-space volume occupied by the muon beam at such facilities. In an ionization-cooling channel, the muon beam passes through a material (the absorber) in which it loses energy. The energy lost is then replaced using RF cavities. The combined effect of energy loss and re-acceleration is to reduce the transverse emittance of the beam (transverse cooling). A major revision of the scope of the project was carried out over the summer of 2014. The revised project plan, which has received the formal endorsement of the international MICE Project Board and the international MICE Funding Agency Committee, will deliver a demonstration of ionization cooling by September 2017. In the revised configuration a central lithium-hydride absorber provides the cooling effect. The magnetic lattice is provided by the two superconducting focus coils and acceleration is provided by two 201 MHz single-cavity modules. The phase space of the muons entering and leaving the cooling cell will be measured by two solenoidal spectrometers. All the superconducting magnets for the ionization cooling demonstration are available at the Rutherford Appleton Laboratory and the first single-cavity prototype is under test in the MuCool Test Area at Fermilab. The design of the cooling demonstration experiment will be described together with a summary of the performance of each of its components. The cooling performance of the revised configuration will also be presented.

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THPF135

Optimization of Orbits, SRF Acceleration, and Focusing Lattice for a Strong-Focusing Cyclotron

cyclotron, dipole, SRF, focusing

4038

K.E. Melconian, S. Assadi, J. Gerity, J.N. Kellams, P.M. McIntyre, A. Sattarov
Texas A&M University, College Station, Texas, USA
N. Pogue
PSI, Villigen, Villigen, Switzerland

The strong-focusing cyclotron is a high-current proton/ion accelerator in which superconducting rf cavities are used to provide enough energy gain per turn to fully separate orbits, and arc-shaped beam transport channels are located in the sector dipole aperture to provide strong focusing of all orbits. An optimization method has been devised by which the orbit separations can be adjusted to provide sufficient separation while maintaining isochronicity on all orbits. The transport optics of the FD lattice is also optimized to provide stable transport and to lock the betatron tunes to a favorable value over the full range of acceleration.

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THPF136

Beam Dynamics Optimization of FRIB Folding Segment 1 with Single-type Re-buncher Cryomodule

lattice, cryomodule, emittance, quadrupole

4042

Z.Q. He, M. Ikegami, F. Marti, T. Xu, Y. Zhang, Q. Zhao
FRIB, East Lansing, Michigan, USA

Funding: The work is supported by the U.S. National Science Foundation under Grant No. PHY-11-02511, and the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
FRIB is using a charge stripper in folding segment 1 to increase the number of charge states of particles to enhance the acceleration efficiency. To control possible emittance growth after the charge stripper, the 3-dimensional on-stripper beam size should be as small as possible. The original 2-cavity-HWR (HWR stands for half wave resonator) rebuncher cryomodule is responsible for the longitudinal focusing before stripper. In order to accept and transport the beam downstream to linac segment 2, another kind of 3-cavity-QWR (QWR stands for quarter wave resonator) rebuncher cryomodule is baselined after the stripper. However, two kinds of cryomodules would increase the cost in design, therefore would be quite inefficient. In this paper, the FRIB lattice with only single-type 4-cavity-QWR rebuncher cryomodule in folding segment 1 is discussed. Positions of lattice elements are adjusted to accommodate the new type of cryomodule. Beam dynamics is optimized to meet the on-stripper beam requirement. The lattice is then adjusted and rematches.

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FRXB3

Advances in CW Ion Linacs

linac, rfq, cryomodule, ion

4085

P.N. Ostroumov
ANL, Argonne, Illinois, USA

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics and Nuclear Physics, under Contracts DE-AC02-76CH03000 and DE-AC02-06CH11357.
Substantial research and development related to CW proton and ion accelerators are being performed at ANL. A normal conducting CW RFQ and a 4K cryomodule with seven quarter-wave resonators (QWR) and SC solenoids have been developed, built, commissioned and operated as an upgrade of the CW ion linac, ATLAS, to achieve higher efficiency and beam intensities. The new CW RFQ and cryomodule were fully integrated into ATLAS and have been in routine operation for more than a year. Currently we are engaged in development of the first cryomodule for a CW H linac being built at FNAL. This work is well aligned with the development of a 1 GeV 25 MW linac as the driver of a sub-critical assembly for near-term spent nuclear fuel disposal. A 2K cryomodule with eight 162.5-MHz SC half wave resonators (HWR) and eight SC solenoids is being developed for FNAL and scheduled for commissioning in 2017. The testing of the first 2 HWRs demonstrated remarkable performance. Experience with the development and reliable operation of new copper and superconducting accelerating structures is an essential precursor for advanced, reliable future large scale high power CW accelerators.

Slides FRXB3 [4.963 MB]

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