IPAC2016 - Classification: 07 Accelerator Technology / T06 Room Temperature RF

Paper	Title	Page
MOOCA01	R&D of a Super-compact SLED System at SLAC	39
	J.W. Wang, G.B. Bowden, S. Condamoor, Y. Ding, V.A. Dolgashev, J.P. Eichner, M.A. Franzi, A.A. Haase, P. Krejcik, J.R. Lewandowski, S.G. Tantawi, L. Xiao, C. Xu SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE-AC03-76SF00515. We have successfully designed, fabricated, installed and tested a super-compact X-Band SLED system at SLAC. It is composed of an elegant mode converter/polarizer and a single sphere energy store cavity with high Q of 94000 and diameter less than 12 cm. The available RF peak power of 50 MW can be compressed to peak average power of more than 200 MW in order to double the kick for the electron bunches in a RF transverse deflector system and greatly improve the measurement resolution for both the electron bunch and the x-ray FEL pulse. High power operation has demonstrated the excellent performance of this RF compression system without any problems in RF breakdown, pulse heating and radiation. The design physics and fabrication as well as the measurement results will be presented in detail.
	Slides MOOCA01 [20.278 MB]
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MOOCA02	RFQ Developments at CEA-IRFU	42
	O. Piquet CEA/DSM/IRFU, France
	Vane RFQs are particularly well suited to high intensity proton acceleration, since they offer minimal RF power losses and best accelerating field accuracy. Cea-Irfu is involved in several developments of 4 vane RFQs namely IPHI, Spiral2, Linac4 and ESS. This paper gives an overview of the design flow and tools developed at Irfu in order to design, tune, condition and commission RFQs. SPIRAL2 RFQ will be mainly used to illustrate this design flow. This CW RFQ requires 180 kW to achieve the nominal accelerating voltage. It can accelerate a 5 mA proton or deuteron beam (A/Q=1 and 2) or a 1 mA ion beam with up to A/Q=3 at 0.75 MeV/A. Conditioning and commissioning of this RFQ are actually in progress.
	Slides MOOCA02 [3.712 MB]
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MOPMR023	Surface Characterization and Field Emission Measurements of Copper Samples inside a Scanning Electron Microscope	283
	J. Ögren, V.G. Ziemann Uppsala University, Uppsala, Sweden S.H.M. Jafri, K. Leifer Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
	Vacuum breakdown in normal-conducting accelerating structures is a limiting factor for high gradient acceleration. Many aspects of the physics governing the breakdown process and its onset are yet to be fully understood. At Uppsala University we address these questions with an in-situ experimental setup mounted in an environmental scanning electron microscope. It consists of a piezo motor driven tungsten needle and a sample surface mounted on a piezo stage, allowing for nano-meter 3D-position control. One of the piezo motors controls the needle-sample gap while the two other scan across the surface. A DC-voltage up to 1 kV is applied across the gap and field emission currents from a copper surface are measured with an electrometer. Here we present the setup and some initial results.
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MOPMR059	Development of S-band High Power Load	383
	X.C. Meng, H.B. Chen, C. Cheng, Y.-C. Du, Q. Gao, J. Shi, P. Wang, Z.F. Xiong TUB, Beijing, People's Republic of China
	Several types of S-band high power loads have been designed, manufactured and tested successfully in Tsinghua University. The high power loads, which work at 2856 MHz for 10 MW~100 MW range, are made of all stainless steel. In this paper, we will present the design, fabrication and the high power test results.
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MOPMW001	A New Buncher for the ESRF Linac Injector	389
	A.S. Setty, A.S. Chauchat, D. Jousse Thales Communications & Security (TCS), Gennevilliers Cedex, France H. Delamare, J. Jacob, B. Ogier, T.P. Perron, E. Rabeuf, C. Richard, V. Serrière, R. Versteegen ESRF, Grenoble, France
	The electron linac was designed to be able to deliver more than 2.5 A in less than 2 ns at 200 MeV within an energy spread of 1% for positrons production at ESRF . The 200 MeV electron linac was commissioned in 1991. A new gun, a cleaner, a pre-buncher cavity and 4 shielded lenses were tested and installed on the injector in 2008 . Then, a new Buncher for the ESRF electron linac injector was manufactured and commissioned in 2015. Meanwhile, some new settings were performed to reduce the energy spread for both cases: the long pulse mode and the short pulse mode. The simulations and measurements will be presented. D. Tronc et Al. "Electron injector for light source", Proc. EPAC88, Italy, Rome, June 1988. ** T. Perron et Al. "New preinjector for the ESRF booster", Proc. EPAC08, Italy, Genoa, June 2008.
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MOPMW002	Modeling and Simulation of Broadband RF Cavities in PSpice	392
	J. Harzheim, D. Domont-Yankulova, H. Klingbeil, R. Königstein TEMF, TU Darmstadt, Darmstadt, Germany M. Frey, H. Klingbeil GSI, Darmstadt, Germany
	Barrier bucket systems are planned for the SIS100 Synchrotron (part of the future accelerator facility FAIR) and the ESR storage ring to facilitate several longitudinal beam manipulations [9] [15]. In order to achieve a single-sine gap signal of the desired amplitude and quality, effects in the linear and nonlinear region of the RF systems have to be investigated and included in the design of the overall system. Therefore, the cavities and the amplifier stages are to be modeled in PSpice. In this contribution, a cavity model will be presented. In a first step, a model for the magnetic alloy (MA) ring cores, which highly account for the properties of the cavity, has been found based on measurement data. In a second step, the future setup of the cavity is systematically created using the MA ring core models. The model of the cavity allows simulations in frequency domain as well as time domain. The results show good agreement with former measurements.
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MOPMW003	Thermal Simulation of an Energy Feedback Normal Conducting RF Cavity	396
	M. Fakhari, K. Flöttmann, S. Pfeiffer, H. Schlarb DESY, Hamburg, Germany J. Roßbach University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany A. Yahaghi CFEL, Hamburg, Germany
	Thermal simulation has been performed for an energy feedback normal conducting RF cavity. The cavity is going to be used as a fast actuator to regulate the arrival time of the electron bunches in fs level in FLASH. By measuring the arrival time jitter of one bunch in a bunch train, the designed cavity apply a correcting accelerating or decelerating voltage to the next bunches. The input power of the cavity is provided by a solid state amplifier and will be coupled to the cavity via a loop on the body. To achieve the fs level precision of the arrival time, the cavity should be able to provide accurate accelerating voltage with a precision of 300 eV. We performed thermal simulation to find out the temperature distribution of the cavity and make sure that heating will not affect its voltage precision. The simulation results show that by using two input loops the coupling constant will vary from 4.11 to 4.13 during the operation of the cavity which effect on the bunchs' arrival time would be less than 0.25 fs. While using just one input loop can lead to an error of about 1 fs.
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MOPMW004	Realization and High Power Tests of Damped C-Band Accelerating Structures for the ELI-NP Linac	399
	D. Alesini, M. Bellaveglia, S. Bini, R. Boni, P. Chimenti, F. Cioeta, R.D. Di Raddo, A. Falone, A. Gallo, V.L. Lollo, L. Palumbo, S. Pioli, A. Variola INFN/LNF, Frascati (Roma), Italy F. Cardelli, M. Magi, A. Mostacci, L. Palumbo, L. Piersanti University of Rome La Sapienza, Rome, Italy F. Cardelli, L. Piersanti INFN-Roma1, Rome, Italy P. Favaron, F. Poletto INFN/LNL, Legnaro (PD), Italy L. Ficcadenti, F. Pellegrino, V. Pettinacci INFN-Roma, Roma, Italy
	The ELI-NP C-Band structures are 1.8 m long travelling wave accelerating structures, quasi-constant gradient, with a field phase advance per cell of 2pi/3. They operate at a repetition rate of 100 Hz and, because of the multi-bunch operation, they have been designed with a dipole HOM damping system to avoid beam break-up (BBU). The structures have symmetric input and output couplers and integrate, in each cell, a waveguide HOM damping systems with silicon carbide RF absorbers. An optimization of the electromagnetic and mechanical design has been done to simplify the fabrication and to reduce their cost. After the first full scale prototype successfully tested at the nominal gradient of 33 MV/m, the production of the twelve structures started. In the paper we illustrate the main design criteria, the realization process and the high power test results.
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MOPMW005	Design of Linac with the New Gaskets Clamping Fabrication Technique	403
SUPSS086	use link to see paper's listing under its alternate paper code
	F. Cardelli INFN-Roma1, Rome, Italy D. Alesini INFN/LNF, Frascati (Roma), Italy M. Magi, L. Palumbo University of Rome La Sapienza, Rome, Italy F. Pellegrino, V. Pettinacci INFN-Roma, Roma, Italy
	Recently, a new technique for the realization of high gradient accelerating structures based on the use of gaskets without brazing processes, has been successfully tested at high power on a 1.6 cells RF gun (D. Alesini, et al, PRST 18, 02001, 2015). The new technique developed at the Laboratories of Frascati of the INFN (Italy) in the framework of the SPARC_LAB project has been also adopted for the ELI-NP RF gun. The use of the special gaskets that simultaneously guarantee the vacuum seal and a perfect RF contact allow to avoid the brazing process, strongly reducing the cost, the realization time and the risk of failure. Moreover, without copper annealing due to the brazing process, it is possible, in principle, to decrease the breakdown rate increasing, at the same time, the maximum achievable gradient. The extension of this new fabrication process to complex LINAC structures is the next step on the application of this new technique on particle accelerator. In the paper, we discuss how to extend this process to S-band and C-band Travelling Wave accelerating structures illustrating their electromagnetic design and their mechanical realization.
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MOPMW006	The RF System of the ELI-NP Gamma Beam Source	407
	L. Piersanti, F. Cardelli, L. Palumbo INFN-Roma1, Rome, Italy D. Alesini, M. Bellaveglia, R. Boni, A. Gallo, A. Variola INFN/LNF, Frascati (Roma), Italy F. Cardelli, L. Palumbo, L. Piersanti University of Rome La Sapienza, Rome, Italy G. D'Auria Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	ELI-NP is a linac based gamma-source under construction in Magurele (RO) by the European consortium EuroGammaS led by INFN. Photons with tunable energy (from 0.2 to 19.5 MeV) and with unprecedented intensity and brilliance will be produced by Compton back-scattering between a high quality electron beam (up to 740 MeV), and a 515 nm intense laser pulse. In order to increase the gamma photon flux, the accelerator will operate in multi-bunch at 100 Hz repetition rate, with 32 bunches separated by 16 ns. Three S-band (2856 MHz) RF power plants will feed two room temperature Travelling Wave (TW) structures, a 1.6 cell Standing Wave (SW) S-band gun (which has been manufactured by means of a new technique based on clamped gaskets without brazing) and two SW RF deflectors for longitudinal beam diagnostics. Ten C-band (5712 MHz) RF power plants will feed 12 TW high-order-modes (HOM) damped structures. In this paper, we review the whole ELI-NP RF architecture including the Low Level RF (LLRF) system.
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MOPMW009	RF System of the SPring-8 Upgrade Project	414
	H. Ego, T. Fujita, N. Hosoda, K. Kobayashi, T. Masuda, S. Matsubara, T. Sugimoto JASRI/SPring-8, Hyogo-ken, Japan T. Asaka, T. Fukui, T. Inagaki, C. Kondo, H. Maesaka, T. Ohshima, T. Sakurai RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	The RF system of the SPring-8 storage ring has stably generated an accelerating voltage of 16 MV at a frequency of 508.58 MHz since 1997. In the upgrade of the SPring-8, a beam energy is lowered from 8 to 6 GeV and a needed voltage is 7 MV. The upgrade employs multi-bending optics, and shortens the straight sections available for RF accelerating cavities by 30%. On account of the space, the RF system is to be so rearranged that the number of cavities can be reduced to half. The analog low-level RF (LLRF) system in use controls the voltage with sufficiently small deviations of less than 0.1 % in amplitude and less than 0.1 degree in phase, but becomes out-of-dates and hard to be maintained. We plan to replace them with a compact digital LLRF system in the MTCA.4 standard and based on under-sampling scheme. The SACLA linac is used for injecting a low-emittance beam to the ring. Because we have to balance the FEL operation and the beam injection on demand, pulse-by-pulse control of beam parameters is going to be implemented to the SACLA LLRF modules. Furthermore, we build a timing system for injection to a target bucket-position in the ring within a time deviation of 3 ps.
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MOPMW010	Property Test of the Q-Factor for High Purity Copper at the Temperature of 20K	417
	A. Iino Sokendai, Ibaraki, Japan K. Endo TOYAMA Co., Ltd., Zama-shi, Kanagawa, Japan S. Yamaguchi KEK, Ibaraki, Japan
	A coherent parametric x-ray radiation (PXR) source based on a cryogenic electron linac has been developed by Toyama Co., Ltd, KEK and Nihon University. This accelerator is a C-band normal-conducting compact linac that requires a high Q factor in the accelerating and de-celerating structures. To obtain a high Q factor, the ac-celerating and decelerating structures are operated around 20 K, and are joined by diffusion bonding and are constructed with high-purity 6N8 copper which has very low resistivity in extremely low temperatures. In this study, we report the measurements and calculation of the residual resistance ratio (RRR) for 6N8 copper and oxy-gen-free copper (Class 1) as well as the Q factor for a pillbox cavity made of 6N8 copper and Class 1. The results of a low-power test of this accelerating structure at low temperature are reported. The Q factor for a 6N8 copper pillbox cavity is not much higher than that of a Class 1 pillbox cavity at low temperatures Moreover, the Q factor is saturated when RRR is greater than 500.
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MOPMW011	The Second Harmonic RF System for J-PARC MR Upgrade	420
	C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii KEK, Tokai, Ibaraki, Japan M. Nomura, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	Power upgrade scenario of J-PARC Main Ring includes replacement of RF cavities with higher field gradient using magnetic alloy cores, FT3L than the present ones. It also need to install the second harmonic RF cavity in the other section where dedicated water system for RF cavities is not available. Installation scenario of the second harmonic RF will be presented.
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MOPMW012	Study for a 162.5 MHz Window-Type RFQ	423
	Q. Fu, P.P. Gan, S.L. Gao, F.J. Jia, H.P. Li, J. Liu, Y.R. Lu, Z. Wang, K. Zhu PKU, Beijing, People's Republic of China
	A window type of four vane radio-frequency quadrupole accelerator has been designed to accelerate 50 mA deuteron beam from 50 keV to 1 MeV. It will operate at 162.5 MHz in CW mode. Compared to the traditional four-vane RFQ, the window-type RFQ is more compact and has higher mode separation without π-mode stabilizing loops or dipole rods. A detailed full 3D model including vane modulation was developed. For the purpose of high shunt impedance, high quality factor and low power dissipation, the RF structure design was optimized by using electromagnetic simulations. Following the EM design optimization, an aluminium model of the window-type RFQ was fabricated and tested.
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MOPMW015	Wakefields Studies of High Gradient X-band Accelerating Structure at SINAP	429
SUPSS087	use link to see paper's listing under its alternate paper code
	X.X. Huang, W. Fang, Q. Gu, M. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	Shanghai compact hard x-ray free electron laser (CHXFEL)* is now proposed accompanied with a high-gradient accelerating structure, which is the trend of large scale and compact facility. This structure operated at X-band (11424 MHz) holds the promise to achieve high gradient up to 80 MV/m. However, due to its particular property, a more serious wakefields** will be generated, leading to worse beam instability effects. In this paper, the computation of this case will be carried out with simulation. Moreover, analysis and optimization will be adopted to suppress beam instability. * C. Feng, Z. T. Zhao, Chinese Sci Bull, 2010, 55, 221-227. ** K. Bane, SLAC, NLC-Note 9, Feb. 1995.
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MOPMW019	Resonant Frequency Control with RCCS for the KOMAC Proton Linac	435
	D.H. Seo, Y.-S. Cho, H.S. Kim, H.-J. Kwon, K.T. Seol, Y.G. Song Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea
	Funding: This work is supported by the Ministry of Science, ICT & Future Planning of the Korean Government. The Resonance control cooling systems (RCCS) of 100 MeV proton linac at the Korea multi-purpose accelerator complex (KOMAC) have been operated for cooling the drift tubes (DT) and controlling the resonant frequency of the drift tube linac (DTL). The RCCS can maintain the cooling water temperature within ±0.1 °C by controlling 3-way valve opening. The RCCS has two types of control mode, the constant cooling water temperature control mode and the resonant frequency control mode. In the case of the resonant frequency control, the error frequency is measured in the low-level RF (LLRF) control system and the RCCS compensates the error frequency by controlling the cooling water temperature of DT with PID algorithm. In this paper, the operation results of the resonant frequency control with the RCCS as well as some modification of the LLRF system are presented.
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MOPMW023	Optimization of the RF Cavity of a Low-energy Storage Ring for Thomson Scattering X-Ray Source	438
SUPSS090	use link to see paper's listing under its alternate paper code
	L. Ovchinnikova, V.I. Shvedunov SINP MSU, Moscow, Russia A. Ryabov IHEP, Moscow Region, Russia V.I. Shvedunov LEA MSU, Moscow, Russia
	Results of optimization of the RF cavity of a low-energy storage ring for Thomson scattering X-ray source are presented. The geometry of 714 MHz RF cavity was optimized to provide maximum shunt impedance taking into account position of higher order modes (HOMs). The number and position of cooling channels were adjusted to minimize frequency shift due to cavity thermal deformations. The waveguide coupler and frequency tuner were calculated. Special attention was paid to detailed calculations of the HOMs parameter and to study of methods to minimize their influence on the storage ring beam dynamics.
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MOPMW024	Design of the New Wideband RF System for the CERN PS Booster	441
	M.M. Paoluzzi, S.C.P. Albright, M.E. Angoletta, L. Arnaudon, S. Energico, A. Findlay, M. Haase, M. Jaussi, A.J. Jones, D. Landré, J.C. Molendijk, D. Quartullo, E.N. Shaposhnikova CERN, Geneva, Switzerland
	For the renovation and upgrade of the CERN PS Booster (PSB) RF systems a development project was launched in 2012. The design, based on a new approach, aimed at replacing the existing tuned, narrowband RF systems with wideband, modular, solid-state driven units. A wide range of issues had to be addressed spanning from RF power production, radiation hardness of solid-state devices, active cancellation of beam-induced voltages, dedicated low-level electronics allowing multi-harmonic operation and beam stability. Following a three-year prototyping and testing campaign and two international reviews, the project endorsement came at the end of year 2015. It foresees the complete removal of present h1, h2 and h10 systems and the deployment of a new one covering all the frequency ranges from 1 MHz to 18 MHz. The four PSB rings will be equipped with 144 identical acceleration cells providing 24 kV total RF voltage per ring. This paper describes the design concepts, the retained solutions, the expected performances and includes the procurement and implementation strategies. This activity is part of the LHC Injectors Upgrade project (LIU).
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MOPMW025	Vacuum RF Breakdown of Accelerating Cavities in Multi-Tesla Magnetic Fields	444
	D.L. Bowring, A. Moretti, M.A. Palmer, D.W. Peterson, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA P.G. Lane, Y. Torun Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359. Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures within multi-Tesla magnetic fields. The application of strong magnetic fields has been shown to lead to an increase in vacuum RF breakdown. This phenomenon imposes operational (i.e. gradient) limitations on cavities in ionization cooling channels, and has a bearing on the design and operation of other RF structures as well, such as photocathodes and klystrons. We present recent results from Fermilab's MuCool Test Area (MTA), in which 201 and 805 MHz cavities were operated at high power both with and without the presence of multi-Tesla magnetic fields. We present an analysis of damage due to breakdown in these cavities, as well as measurements related to dark current and their relation to a conceptual model describing breakdown phenomena.
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MOPMW026	Resonant Control for Fermilab's PXIE RFQ	447
	D.L. Bowring, B.E. Chase, J. Czajkowski, J.P. Edelen, D.J. Nicklaus, J. Steimel, T.J. Zuchnik Fermilab, Batavia, Illinois, USA S. Biedron, A.L. Edelen, S.V. Milton CSU, Fort Collins, Colorado, USA
	Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359. The RFQ for Fermilab's PXIE test program is designed to accelerate a < 10 mA H⁻ CW beam to 2.1 MeV. The RFQ has a four-vane design, with four modules brazed together for a total of 4.45 m in length. The RF power required is < 130 kW at 162.5 MHz. A 3 kHz limit on the maximum allowable frequency error is imposed by the RF amplifiers. This frequency constraint must be managed entirely through differential cooling of the RFQ's vanes and outer body and associated material expansion. Simulations indicate that the body and vane coolant temperature should be controlled to within 0.1 degrees C. We present the design of the cooling network and the resonant control algorithm for this structure, as well as results from initial operation.
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MOPMW027	Design of a Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster	451
	C.-Y. Tan, J.E. Dey, K.L. Duel, R.L. Madrak, W. Pellico, E. Prebys, J. Reid, 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 and built for the Fermilab Booster. The purpose is to flatten the bucket at injection and thus change the longitudinal beam distribution to decrease space charge effects. It can also help with transition crossing. A model cavity has been built to verify various CST Microwave studio and COMSOL results and a test stand has been built to ensure that the Y567 tube is able to operate at twice the Booster fundamental frequencies. Also discussed are the RF windows which are critical to the design.
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MOPMW028	Progress on the MICE RF Module at LBNL	454
	T.H. Luo, A.J. DeMello, A.R. Lambert, D. Li, T.J. Loew, S. Prestemon, S.P. Virostek, J.G. Wallig LBNL, Berkeley, California, USA T.G. Anderson, A.D. Bross, M.A. Palmer Fermilab, Batavia, Illinois, USA Y. Torun IIT, Chicago, Illinois, USA
	The international Muon Ionization Cooling Experiment aims to demonstrate the transverse cooling of a muon 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 assembly of MICE RF Module is being carried out at LBL. In this paper we will report the recent progress on the assembly work.
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MOPMW029	Analysis of Transverse Field Induced by Curved Beryllium Window in Muon Ionization Cooling Cavity	457
	T.H. Luo, D. Li LBNL, Berkeley, California, USA
	The beryllium windows are used in muon ionization cooling cavity to increase the cavity shunt impedance. The windows are curved for predictable thermal deformation. This curvature also introduces transverse field, which will affect the transverse beam emittance. In this paper, we will analyze this transverse field and evaluate its effect on the emittance cooling.
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MOPMW030	High Powered Tests of Dielectric Loaded High Pressure RF Cavities for Use in Muon Cooling Channels	460
	B.T. Freemire IIT, Chicago, Illinois, USA D.L. Bowring, A. Moretti, D.W. Peterson, A.V. Tollestrup, Y. Torun, K. Yonehara Fermilab, Batavia, Illinois, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA
	Funding: This work is supported by the Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359. Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. Alumina of purities ranging from 96 to 99.8% was tested in a high pressure RF test cell at the MuCool Test Area at Fermilab. The results of breakdown studies with pure nitrogen gas, and oxygen-doped nitrogen gas indicate the peak surface electric field on the alumina ranges between 10 and 15 MV/m. How these results affect the design of a prototype cooling channel cavity will be discussed.
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MOPMW031	Beam Test of a Dielectric Loaded High Pressure RF Cavity for Use in Muon Cooling Channels	463
	B.T. Freemire IIT, Chicago, Illinois, USA D.L. Bowring, A. Moretti, D.W. Peterson, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, Illinois, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA
	Funding: This work is supported by the Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359. Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. A 99.5% alumina ring was inserted in a high pressure RF test cell and subjected to an intense proton beam at the MuCool Test Area at Fermilab. The results of the performance of this dielectric loaded high pressure RF cavity will be presented.
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MOPMW032	Study of RF Breakdown in 805MHz Pillbox Modular Cavity in Strong Magnetic Field	466
	A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA D.L. Bowring, A. Moretti, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA
	RF breakdown has a negative impact on a cavity's performance, especially with the presence of strong magnetic fields. This issue can arise in designs of muon ionization cooling channel, RF guns, klystrons and in many other applications. The MuCool Test Area at Fermilab is the facility that allows us to study the effects of static magnetic field on RF cavity operation. As a part of this research program, we have tested an 805MHz pillbox "modular" cavity in strong external magnetic fields. The design of the cavity allowed for a better control over sources of systematic error. "Modular" structure of the cavity enables easy dismounting of the endplates to perform inspection of inner surfaces after each run as well as swapping endplates to study the effects of various materials on breakdown phenomenon. Coupler design ensures maximum electric field enhancement on cavity axis, thus reducing breakdown probability in the coupler region. The results and analysis from high-power runs with zero and non-zero external magnetic fields will be presented.
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MOPMW033	Acoustic Localization of RF Cavity Breakdown: Status and Progress	470
	P.G. Lane, P. Snopok, Y. Torun Illinois Institute of Technology, Chicago, Illinois, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA
	Current designs for muon accelerators require high-gradient RF cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. It has been found that placing normal conducting RF cavities in strong magnetic fields 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 localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to a small region of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Presented here are the algorithms for and results from localizing simulated and experimental acoustic data from the Modular Cavity at the MuCool Test Area at Fermilab.
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MOPMW034	Final Commissioning of the MICE RF Module Prototype with Production Couplers	474
	Y. Torun, P.G. Lane Illinois Institute of Technology, Chicago, Illlinois, USA T.G. Anderson, M. Backfish, D.L. Bowring, A. Moretti, D.V. Neuffer, D.W. Peterson, M. Popovic, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA T.L. Hart UMiss, University, Mississippi, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA T.H. Luo LBNL, Berkeley, California, USA
	Funding: Supported by the US Department of Energy Office of Science through the Muon Accelerator Program. We report operational experience from the prototype RF module for the Muon Ionization Cooling Experiment (MICE) with final production couplers at Fermilab's MuCool Test Area. This is the last step in fully qualifying the RF modules for operation in the experiment at RAL.
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MOPMW035	Wakefield Excitation in Power Extraction Cavity (PEC) of Co-linear X-band Energy Booster (CXEB) in Time Domain (T3P) with ACE3P	477
	T. Sipahi, S. Biedron, S.V. Milton CSU, Fort Collins, Colorado, USA
	In our previous papers we provided the general concept and the design details of our proposed Co-linear X-band Energy Booster (CXEB) as well as more advanced 3D simulations of our system using the frequency domain solvers OMEGA3P and S3P of the ACE3P Suite. Here, using the time domain solver T3P of ACE3P, we provide the single bunch and multiple bunch wakefield excitations resulting from a Gaussian bunch. The related power extraction mechanism for our traveling wave (TW) X-band power extraction cavity (PEC) are also discussed further.
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MOPMW036	Frequency Domain Simulations of Co-linear X-band Energy Booster (CXEB) RF Cavity Structures and Passive RF Components with ACE3P	480
	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, and this can lead to more compact light sources. At the Colorado State University Accelerator Laboratory (CSUAL) [1] we would like to adapt this technology to our 1.3-GHz, L-band accelerator system using a passively driven 11.7 GHz traveling wave X-band configuration that capitalizes on the high shunt impedances achievable in X-band accelerating structures 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 comparisons of the important parameters achieved using SUPERFISH and OMEGA3P for our Co-linear X-band Energy Booster (XCEB) system that will allow us to achieve our goal of reaching the maximum practical net potential across the X-band accelerating structures while driven solely by the beam from the L-band system.
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MOPMW038	Measurements of Copper RF Surface Resistance at Cryogenic Temperatures for Applications to X-Band and S-Band Accelerators	487
	A.D. Cahill, A. Fukasawa, J.B. Rosenzweig UCLA, Los Angeles, California, USA G.B. Bowden, V.A. Dolgashev, M.A. Franzi, S.G. Tantawi, P.B. Welander, C. Yoneda SLAC, Menlo Park, California, USA J. Guo JLab, Newport News, Virginia, USA Y. Higashi OIST, Onna-son, Okinawa, Japan
	Funding: Funding from DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515 Recent SLAC experiments with cryogenically cooled X-Band standing wave copper accelerating cavities have shown that these structures can operate with accelerating gradients of ~250 MV/m and low breakdown rates. These results prompted us to perform systematic studies of copper rf properties at cryogenic temperatures and low rf power. We placed copper cavities into a cryostat cooled by a pulse tube cryocooler, so cavities could be cooled to 4K. We used different shapes of cavities for the X-Band and S-Band measurements. Properties of the cavities were measured using a network analyzer. We calculated rf surface resistance from measured Q0 and Q external of the cavity at temperatures from 4 K to room temperature. The results were then compared to the theory proposed by Reuter and Sondheimer. These measurements are a part of studies with the goal of reaching very high operational accelerating gradients in normal conducting rf structures.
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MOPMW039	TM01 Mode Launcher for Use in High Brightness Photoguns	491
	A.D. Cahill UCLA, Los Angeles, California, USA M. Dal Forno, V.A. Dolgashev SLAC, Menlo Park, California, USA
	Funding: DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515 Photo rf guns are a source of electron beams for X-ray FELs such as LCLS and European XFEL. In existing photoguns power is coupled into the cavity by waveguides through the cell walls, like LCLS, or through coaxial coupling, at the European XFEL. We are considering feeding a gun using a circular waveguide with the TM01 mode. To do that we need a mode launcher, a matched device that couples the rectangular TE01 mode waveguide to a TM01 mode in a circular waveguide. Use of the mode launcher reduces complexity of the gun cavity and increases flexibility of positioning the input waveguide relative to the gun body. Mode launchers have been successfully used at SLAC and elsewhere for X-band high gradient tests. Because the existing mode launchers were not built for high brightness guns, they have a significant quadrupole field component. High brightness rf guns have tight requirements on output beam properties, and this quadrupole component adversely affects the beam. We have designed a mode launcher free of this disadvantage. We present design considerations, methodology, and an example S-band mode launcher.
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MOPMW040	Electron Beam Excitation of a Surface Wave in mm-Wave Open Accelerating Structures	494
	M. Dal Forno, G.B. Bowden, C.I. Clarke, V.A. Dolgashev, M.J. Hogan, D.J. McCormick, A. Novokhatski, B.D. O'Shea, S.G. Tantawi, S.P. Weathersby SLAC, Menlo Park, California, USA B. Spataro INFN/LNF, Frascati (Roma), Italy
	Funding: Work supported by the US DOE under contract DE-AC02-76SF00515. As part of research on the physics of rf breakdowns we performed experiments with high gradient traveling-wave mm-wave accelerating structures. The accelerating structures are open, composed of two identical halves separated by an adjustable gap. The electromagnetic fields are excited by an ultra-relativistic electron beam. We observed that a confined travelling-wave mode exists in half of the accelerating structure. The experiments were conducted at FACET facility at SLAC National Accelerator Laboratory. Depending on the gap width, the accelerating structure had beam-synchronous frequencies that vary from 90 to 140 GHz. When we opened the gap by more than half wavelength the synchronous wave remains trapped. Its behavior is consistent with the so called "surface wave". We characterized this beam-wave interaction by several methods: measurement of the radiated rf energy with the pyro-detector, measurement of the spectrum with an interferometer, measurement of the beam deflection by using the beam position monitors and profile monitor.
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MOPMW041	Measurements of RF Breakdowns in Beam Driven mm-Wave Accelerating Structures	497
	M. Dal Forno, G.B. Bowden, C.I. Clarke, V.A. Dolgashev, M.J. Hogan, D.J. McCormick, A. Novokhatski, S.G. Tantawi, S.P. Weathersby SLAC, Menlo Park, California, USA B. Spataro INFN/LNF, Frascati (Roma), Italy
	Funding: Work supported by the US DOE under contract DE-AC02-76SF00515 We studied the physics and properties of rf breakdowns in high gradient traveling-wave accelerating structures at 100 GHz. The structures are open, made of two halves with a gap in between. The rf fields were excited in the structure by an ultra-relativistic electron beam generated by the FACET facility at the SLAC National Accelerator Laboratory. We observed rf breakdowns generated in the presence of GV/m scale electric fields. We varied the rf fields excited by the FACET bunch by moving structure relative to the beam and by changing the gap between structure halves. Reliable breakdowns detectors allowed us to measure the rf breakdown rate at these different rf parameters. We measured radiated rf energy with a pyro-detector. When the beam was off-axis, we observed beam deflection in the beam position monitors and on the screen of a magnetic spectrometer. The measurements of the deflection allowed us to verify our calculation of the accelerating gradient.
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MOPMW043	Overview of High Power Vacuum Dry RF Load Designs	504
	A.K. Krasnykh, A. Brachmann, F.-J. Decker, T.J. Maxwell, J. Sheppard SLAC, Menlo Park, California, USA
	Funding: Work supported by US Department of Energy under contract DE-AC02-76SF00515 A specific feature of RF linacs based on the pulsed traveling wave (TW) mode of operation is that only a portion of the RF energy is used for the beam acceleration. The residual RF energy has to be terminated into an RF load. Higher accelerating gradients require higher RF sources and RF loads, which can stably terminate the residual RF power. This overview will outline vacuumed RF loads only. A common method to terminate multi-MW RF power is to use circulated water (or other liquid) as an absorbing medium. A solid dielectric interface (a high quality ceramic) is required to separate vacuum and liquid RF absorber mediums. Using such RF load approaches in TW linacs is troubling because there is a fragile ceramic window barrier and a failure could become catastrophic for linac vacuum and RF systems. Traditional loads comprising of a ceramic disk have limited peak and average power handling capability and are therefore not suitable for high gradient TW linacs. This overview will focus on 'vacuum dry' or 'all-metal' loads that do not employ any dielectric interface between vacuum and absorber. The first prototype is an original design of RF loads for the Stanford Two-Mile Accelerator.
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MOPMW044	Design of an RF Device to Study the Multipactor Phenomenon	507
SUPSS115	use link to see paper's listing under its alternate paper code
	D. Amorim Grenoble-INP Phelma, Grenoble, France J.-M. De Conto, Y. Gómez Martínez LPSC, Grenoble Cedex, France
	Multipacting is a parasitic electron avalanche process that may occur in RF devices such as cavities or couplers. As it can be detrimental to the operation of these devices, the accelerator group at LPSC is currently designing a coaxial resonant cavity in order to study this phenomenon. In order to determine the measurable parameters on the cavity, calculations were performed and validated with numerical simulations. In a second time multipacting simulations were conducted to determine if the experiment will allow to observe multipacting.
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MOPMY001	Beam Dynamics Analysis for the Ultra-fast Kicker in Circular Cooler Ring of JLEIC	510
	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. An ultra-fast kicker system consist of four quarter wavelength resonator based deflecting cavities was developed that simultaneously resonates at 10 subharmonic modes of the 476.3MHz bunch repetition frequency, thus every 10th bunch in the bunch train will experience a transverse kick while all the other bunches are undisturbed. This fast kicker is developed for the Energy Recovery Linac (ERL) based electron Circular Cooler Ring (CCR) in the proposed Jefferson Lab Electron Ion Collider (JLEIC, previously MEIC). The electron bunches can be reused 10-30 turns thus the beam current in the ERL can be reduced to 1/10 - 1/30 (150mA - 50mA) of the cooling bunch current (1.5A). In this paper, several methods to synthesis such a kicker waveform will be discussed with the comparison of beam dynamics tracking in Elegant.
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MOPMY005	Study of Pretuning and High Power Test of DTL Iris Waveguide Couplers Using a Single Cell Cavity	522
	S.W. Lee, M.S. Champion, Y.W. Kang ORNL, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S.DOE. Six drift tube linac (DTL) cavities have been operating successfully at the Spallation Neutron Source (SNS). Each cavity is fed by a tapered ridge waveguide iris input coupler and a waveguide ceramic disk window. The original couplers and cavities have been in service for more than a decade. Design optimization and tuning of the couplers were initially performed prior to installation and commissioning of the cavities. Since each DTL cavity is unique, expensive, and fully utilized for neutron production, none of the cavity structure is available as a test cavity or a spare. Maintaining spares for operations and for future system upgrade, test setup of the iris couplers for precision tuning is needed. Ideally a smaller cavity structure may be used for pretuning and RF conditioning of the iris couplers as a test cavity or a bridge waveguide. In this paper, study of using a single cell cavity for the iris tuning and conditioning is presented along with the 3D simulation results.
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MOPMY007	Mechanical Design and 3-D Coupled RF, Thermal-Structural Analysis of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac	525
	J.C. Brutus, S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, A.V. Fedotov, M.C. Grau, C. Pai, L. Snydstrup, J.E. Tuozzolo, B. P. Xiao, T. Xin, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, 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. Two normal conducting cavities operating at 704 MHz and 2.1 GHz will be used for the Low Energy RHIC electron Cooling (LEReC) under development at BNL to improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon. The single cell 704 MHz cavity and the 3-cell 2.1 GHz third harmonic cavity will be used in LEReC to correct the energy spread introduced in the SRF cavity. The successful operation of normal RF cavities has to satisfy both RF and mechanical requirements. 3-D coupled RF-thermal-structural analysis has been performed on the cavities to confirm the structural stability and to minimize the frequency shift resulting from thermal and structural expansion. In this paper, we will present an overview of the mechanical design, results from the RF-thermal-mechanical analysis, progress on the fabrication and schedule for the normal conducting RF cavities for LEReC.
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MOPMY009	HOM Consideration of 704 MHz and 2.1 GHz Cavities for LEReC Linac	528
	B. P. Xiao, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, J.C. Brutus, A.V. Fedotov, H. Hahn, G.T. McIntyre, C. Pai, K.S. Smith, J.E. Tuozzolo, Q. Wu, T. Xin, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh Fermilab, Batavia, Illinois, 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 supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE. To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under development at BNL. The Linac of LEReC is designed to deliver 2 MV to 5 MV electron beam, with rms dp/p less than 5·10^-4. The HOM in this Linac is carefully studied to ensure this specification.
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MOPMY010	RF Design of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac	532
	B. P. Xiao, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, J.C. Brutus, A.V. Fedotov, H. Hahn, G.T. McIntyre, C. Pai, K.S. Smith, J.E. Tuozzolo, Q. Wu, T. Xin, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh Fermilab, Batavia, Illinois, USA S.A. Belomestnykh, I. Ben-Zvi, T. Xin 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 supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE. To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy 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 energy spread correction. Currently these two cavities are under fabrication. In this paper we report the RF design of these two cavities.
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MOPMY033	Effect of Bandwidth of Low Level Radio Frequency System on the Instability of an Electron Beam	570
	Z.K. Liu, L.-H. Chang, M.H. Chang, L.J. Chen, PY. Chen, F.-T. Chung, M.-C. Lin, C.H. Lo, C.L. Tsai, M.H. Tsai, Ch. Wang, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	The analog Low Level Radio Frequency (LLRF) system is used at Taiwan Photon Source (TPS) RF system. It is composed of three feedback loops to control the amplitude and phase of accelerating field and the frequency of RF cavity. Instability of electron beam and accelerating field due to the bandwidth of LLRF system were observed during the TPS commissioning. This effect was studied and the results will be presented in this paper.
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MOPOR013	The PS 10 MHz High Level RF System Upgrade	622
	G. Favia, H. Damerau, V.D. Desquiens, S. Energico, M. Morvillo, D. Perrelet, C. Rossi CERN, Geneva, Switzerland
	In view of the upgrade of the injectors for the High Luminosity LHC, significantly higher bunch intensity is required for LHC-type beams. In this context an upgrade of the main accelerating RF system of the Proton Synchrotron (PS) is necessary, aiming at reducing the cavity impedance which is the source of longitudinal coupled-bunch oscillations. These instabilities pose as a major limitation for the increase of the beam intensity as planned after LS2. The 10 MHz RF system consists in 11 ferrite loaded cavities, driven by tube-based power amplifiers for reasons of radiation hardness. The cavity-amplifier system is equipped with a wide-band feedback that reduces the beam induced voltage. A further reduction of the beam loading is foreseen by upgrading the feedback system, which can be reasonably achieved by increasing the loop gain of the existing amplification chain. This paper describes the progress of the design of the upgraded feedback system and shows the results of the tests on the new amplifier prototype, installed in the PS during the 2015-16 technical stop. It also reports the first results of its performance with beam, observed in the beginning of the 2016 run.
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MOPOY054	Status of the ESS RFQ	974
	D. Chirpaz-Cerbat, A. Albéri, A.C. Chauveau, M. Lacroix, N. Misiara, G. Perreu, O. Piquet, H. Przybilski, N. Sellami CEA/IRFU, Gif-sur-Yvette, France N. Berton, G. Bourdelle, M. Desmons, A.C. France, V.M. Hennion, P.-A. Leroy, B. Pottin CEA/DSM/IRFU, France
	The ESS Radio-Frequency Quadrupole (RFQ) is a 4-vanes resonant cavity designed at the frequency of 352.21 MHz. It must accelerate and bunch a 70mA proton beams from 75keV to 3.62MeV with a 4% duty cycle. The RFQ design has already been done, and documented in other papers. This one will present the global status of the RFQ, with technical solutions cho-sen for the main components (for fabrication and op-eration) and the present status of the RFQ fabrication.
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WEPMB008	ESS DTL Mechanical Design and Prototyping.	2131
	P. Mereu, M. Mezzano INFN-Torino, Torino, Italy D. Castronovo, R. Visintini Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy F. Grespan, A. Pisent, M. Poggi, C. R. Roncolato INFN/LNL, Legnaro (PD), Italy
	The Drift Tube Linac (DTL) of the European Spallation Source (ESS) is designed to operate at 352.2 MHz with a duty cycle of 4% (3 ms pulse length, 14 Hz repetition period) and will accelerate a proton beam of 62.5 mA pulse peak current from 3.62 to 90 MeV. In this paper the DTL mechanical design and simulations are presented, together with the results obtained from the prototypes of three drift tubes, equipped respectively with Permanent Magnet Quadrupole, Steerer and Beam Position Monitor.
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Paper

Title

Page

R&D of a Super-compact SLED System at SLAC

39

J.W. Wang, G.B. Bowden, S. Condamoor, Y. Ding, V.A. Dolgashev, J.P. Eichner, M.A. Franzi, A.A. Haase, P. Krejcik, J.R. Lewandowski, S.G. Tantawi, L. Xiao, C. Xu
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE-AC03-76SF00515.
We have successfully designed, fabricated, installed and tested a super-compact X-Band SLED system at SLAC. It is composed of an elegant mode converter/polarizer and a single sphere energy store cavity with high Q of 94000 and diameter less than 12 cm. The available RF peak power of 50 MW can be compressed to peak average power of more than 200 MW in order to double the kick for the electron bunches in a RF transverse deflector system and greatly improve the measurement resolution for both the electron bunch and the x-ray FEL pulse. High power operation has demonstrated the excellent performance of this RF compression system without any problems in RF breakdown, pulse heating and radiation. The design physics and fabrication as well as the measurement results will be presented in detail.

Slides MOOCA01 [20.278 MB]

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MOOCA02

RFQ Developments at CEA-IRFU

42

O. Piquet
CEA/DSM/IRFU, France

Vane RFQs are particularly well suited to high intensity proton acceleration, since they offer minimal RF power losses and best accelerating field accuracy. Cea-Irfu is involved in several developments of 4 vane RFQs namely IPHI, Spiral2, Linac4 and ESS. This paper gives an overview of the design flow and tools developed at Irfu in order to design, tune, condition and commission RFQs. SPIRAL2 RFQ will be mainly used to illustrate this design flow. This CW RFQ requires 180 kW to achieve the nominal accelerating voltage. It can accelerate a 5 mA proton or deuteron beam (A/Q=1 and 2) or a 1 mA ion beam with up to A/Q=3 at 0.75 MeV/A. Conditioning and commissioning of this RFQ are actually in progress.

Slides MOOCA02 [3.712 MB]

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MOPMR023

Surface Characterization and Field Emission Measurements of Copper Samples inside a Scanning Electron Microscope

283

J. Ögren, V.G. Ziemann
Uppsala University, Uppsala, Sweden
S.H.M. Jafri, K. Leifer
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden

Vacuum breakdown in normal-conducting accelerating structures is a limiting factor for high gradient acceleration. Many aspects of the physics governing the breakdown process and its onset are yet to be fully understood. At Uppsala University we address these questions with an in-situ experimental setup mounted in an environmental scanning electron microscope. It consists of a piezo motor driven tungsten needle and a sample surface mounted on a piezo stage, allowing for nano-meter 3D-position control. One of the piezo motors controls the needle-sample gap while the two other scan across the surface. A DC-voltage up to 1 kV is applied across the gap and field emission currents from a copper surface are measured with an electrometer. Here we present the setup and some initial results.

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MOPMR059

Development of S-band High Power Load

383

X.C. Meng, H.B. Chen, C. Cheng, Y.-C. Du, Q. Gao, J. Shi, P. Wang, Z.F. Xiong
TUB, Beijing, People's Republic of China

Several types of S-band high power loads have been designed, manufactured and tested successfully in Tsinghua University. The high power loads, which work at 2856 MHz for 10 MW~100 MW range, are made of all stainless steel. In this paper, we will present the design, fabrication and the high power test results.

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MOPMW001

A New Buncher for the ESRF Linac Injector

389

A.S. Setty, A.S. Chauchat, D. Jousse
Thales Communications & Security (TCS), Gennevilliers Cedex, France
H. Delamare, J. Jacob, B. Ogier, T.P. Perron, E. Rabeuf, C. Richard, V. Serrière, R. Versteegen
ESRF, Grenoble, France

The electron linac was designed to be able to deliver more than 2.5 A in less than 2 ns at 200 MeV within an energy spread of 1% for positrons production at ESRF *. The 200 MeV electron linac was commissioned in 1991. A new gun, a cleaner, a pre-buncher cavity and 4 shielded lenses were tested and installed on the injector in 2008 **. Then, a new Buncher for the ESRF electron linac injector was manufactured and commissioned in 2015. Meanwhile, some new settings were performed to reduce the energy spread for both cases: the long pulse mode and the short pulse mode. The simulations and measurements will be presented.
* D. Tronc et Al. "Electron injector for light source", Proc. EPAC88, Italy, Rome, June 1988.
** T. Perron et Al. "New preinjector for the ESRF booster", Proc. EPAC08, Italy, Genoa, June 2008.

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MOPMW002

Modeling and Simulation of Broadband RF Cavities in PSpice

392

J. Harzheim, D. Domont-Yankulova, H. Klingbeil, R. Königstein
TEMF, TU Darmstadt, Darmstadt, Germany
M. Frey, H. Klingbeil
GSI, Darmstadt, Germany

Barrier bucket systems are planned for the SIS100 Synchrotron (part of the future accelerator facility FAIR) and the ESR storage ring to facilitate several longitudinal beam manipulations [9] [15]. In order to achieve a single-sine gap signal of the desired amplitude and quality, effects in the linear and nonlinear region of the RF systems have to be investigated and included in the design of the overall system. Therefore, the cavities and the amplifier stages are to be modeled in PSpice. In this contribution, a cavity model will be presented. In a first step, a model for the magnetic alloy (MA) ring cores, which highly account for the properties of the cavity, has been found based on measurement data. In a second step, the future setup of the cavity is systematically created using the MA ring core models. The model of the cavity allows simulations in frequency domain as well as time domain. The results show good agreement with former measurements.

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MOPMW003

Thermal Simulation of an Energy Feedback Normal Conducting RF Cavity

396

M. Fakhari, K. Flöttmann, S. Pfeiffer, H. Schlarb
DESY, Hamburg, Germany
J. Roßbach
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
A. Yahaghi
CFEL, Hamburg, Germany

Thermal simulation has been performed for an energy feedback normal conducting RF cavity. The cavity is going to be used as a fast actuator to regulate the arrival time of the electron bunches in fs level in FLASH. By measuring the arrival time jitter of one bunch in a bunch train, the designed cavity apply a correcting accelerating or decelerating voltage to the next bunches. The input power of the cavity is provided by a solid state amplifier and will be coupled to the cavity via a loop on the body. To achieve the fs level precision of the arrival time, the cavity should be able to provide accurate accelerating voltage with a precision of 300 eV. We performed thermal simulation to find out the temperature distribution of the cavity and make sure that heating will not affect its voltage precision. The simulation results show that by using two input loops the coupling constant will vary from 4.11 to 4.13 during the operation of the cavity which effect on the bunchs' arrival time would be less than 0.25 fs. While using just one input loop can lead to an error of about 1 fs.

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MOPMW004

Realization and High Power Tests of Damped C-Band Accelerating Structures for the ELI-NP Linac

399

D. Alesini, M. Bellaveglia, S. Bini, R. Boni, P. Chimenti, F. Cioeta, R.D. Di Raddo, A. Falone, A. Gallo, V.L. Lollo, L. Palumbo, S. Pioli, A. Variola
INFN/LNF, Frascati (Roma), Italy
F. Cardelli, M. Magi, A. Mostacci, L. Palumbo, L. Piersanti
University of Rome La Sapienza, Rome, Italy
F. Cardelli, L. Piersanti
INFN-Roma1, Rome, Italy
P. Favaron, F. Poletto
INFN/LNL, Legnaro (PD), Italy
L. Ficcadenti, F. Pellegrino, V. Pettinacci
INFN-Roma, Roma, Italy

The ELI-NP C-Band structures are 1.8 m long travelling wave accelerating structures, quasi-constant gradient, with a field phase advance per cell of 2pi/3. They operate at a repetition rate of 100 Hz and, because of the multi-bunch operation, they have been designed with a dipole HOM damping system to avoid beam break-up (BBU). The structures have symmetric input and output couplers and integrate, in each cell, a waveguide HOM damping systems with silicon carbide RF absorbers. An optimization of the electromagnetic and mechanical design has been done to simplify the fabrication and to reduce their cost. After the first full scale prototype successfully tested at the nominal gradient of 33 MV/m, the production of the twelve structures started. In the paper we illustrate the main design criteria, the realization process and the high power test results.

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MOPMW005

Design of Linac with the New Gaskets Clamping Fabrication Technique

403

SUPSS086

use link to see paper's listing under its alternate paper code

F. Cardelli
INFN-Roma1, Rome, Italy
D. Alesini
INFN/LNF, Frascati (Roma), Italy
M. Magi, L. Palumbo
University of Rome La Sapienza, Rome, Italy
F. Pellegrino, V. Pettinacci
INFN-Roma, Roma, Italy

Recently, a new technique for the realization of high gradient accelerating structures based on the use of gaskets without brazing processes, has been successfully tested at high power on a 1.6 cells RF gun (D. Alesini, et al, PRST 18, 02001, 2015). The new technique developed at the Laboratories of Frascati of the INFN (Italy) in the framework of the SPARC_LAB project has been also adopted for the ELI-NP RF gun. The use of the special gaskets that simultaneously guarantee the vacuum seal and a perfect RF contact allow to avoid the brazing process, strongly reducing the cost, the realization time and the risk of failure. Moreover, without copper annealing due to the brazing process, it is possible, in principle, to decrease the breakdown rate increasing, at the same time, the maximum achievable gradient. The extension of this new fabrication process to complex LINAC structures is the next step on the application of this new technique on particle accelerator. In the paper, we discuss how to extend this process to S-band and C-band Travelling Wave accelerating structures illustrating their electromagnetic design and their mechanical realization.

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MOPMW006

The RF System of the ELI-NP Gamma Beam Source

407

L. Piersanti, F. Cardelli, L. Palumbo
INFN-Roma1, Rome, Italy
D. Alesini, M. Bellaveglia, R. Boni, A. Gallo, A. Variola
INFN/LNF, Frascati (Roma), Italy
F. Cardelli, L. Palumbo, L. Piersanti
University of Rome La Sapienza, Rome, Italy
G. D'Auria
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

ELI-NP is a linac based gamma-source under construction in Magurele (RO) by the European consortium EuroGammaS led by INFN. Photons with tunable energy (from 0.2 to 19.5 MeV) and with unprecedented intensity and brilliance will be produced by Compton back-scattering between a high quality electron beam (up to 740 MeV), and a 515 nm intense laser pulse. In order to increase the gamma photon flux, the accelerator will operate in multi-bunch at 100 Hz repetition rate, with 32 bunches separated by 16 ns. Three S-band (2856 MHz) RF power plants will feed two room temperature Travelling Wave (TW) structures, a 1.6 cell Standing Wave (SW) S-band gun (which has been manufactured by means of a new technique based on clamped gaskets without brazing) and two SW RF deflectors for longitudinal beam diagnostics. Ten C-band (5712 MHz) RF power plants will feed 12 TW high-order-modes (HOM) damped structures. In this paper, we review the whole ELI-NP RF architecture including the Low Level RF (LLRF) system.

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MOPMW009

RF System of the SPring-8 Upgrade Project

414

H. Ego, T. Fujita, N. Hosoda, K. Kobayashi, T. Masuda, S. Matsubara, T. Sugimoto
JASRI/SPring-8, Hyogo-ken, Japan
T. Asaka, T. Fukui, T. Inagaki, C. Kondo, H. Maesaka, T. Ohshima, T. Sakurai
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

The RF system of the SPring-8 storage ring has stably generated an accelerating voltage of 16 MV at a frequency of 508.58 MHz since 1997. In the upgrade of the SPring-8, a beam energy is lowered from 8 to 6 GeV and a needed voltage is 7 MV. The upgrade employs multi-bending optics, and shortens the straight sections available for RF accelerating cavities by 30%. On account of the space, the RF system is to be so rearranged that the number of cavities can be reduced to half. The analog low-level RF (LLRF) system in use controls the voltage with sufficiently small deviations of less than 0.1 % in amplitude and less than 0.1 degree in phase, but becomes out-of-dates and hard to be maintained. We plan to replace them with a compact digital LLRF system in the MTCA.4 standard and based on under-sampling scheme. The SACLA linac is used for injecting a low-emittance beam to the ring. Because we have to balance the FEL operation and the beam injection on demand, pulse-by-pulse control of beam parameters is going to be implemented to the SACLA LLRF modules. Furthermore, we build a timing system for injection to a target bucket-position in the ring within a time deviation of 3 ps.

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MOPMW010

Property Test of the Q-Factor for High Purity Copper at the Temperature of 20K

417

A. Iino
Sokendai, Ibaraki, Japan
K. Endo
TOYAMA Co., Ltd., Zama-shi, Kanagawa, Japan
S. Yamaguchi
KEK, Ibaraki, Japan

A coherent parametric x-ray radiation (PXR) source based on a cryogenic electron linac has been developed by Toyama Co., Ltd, KEK and Nihon University. This accelerator is a C-band normal-conducting compact linac that requires a high Q factor in the accelerating and de-celerating structures. To obtain a high Q factor, the ac-celerating and decelerating structures are operated around 20 K, and are joined by diffusion bonding and are constructed with high-purity 6N8 copper which has very low resistivity in extremely low temperatures. In this study, we report the measurements and calculation of the residual resistance ratio (RRR) for 6N8 copper and oxy-gen-free copper (Class 1) as well as the Q factor for a pillbox cavity made of 6N8 copper and Class 1. The results of a low-power test of this accelerating structure at low temperature are reported. The Q factor for a 6N8 copper pillbox cavity is not much higher than that of a Class 1 pillbox cavity at low temperatures Moreover, the Q factor is saturated when RRR is greater than 500.

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MOPMW011

The Second Harmonic RF System for J-PARC MR Upgrade

420

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

Power upgrade scenario of J-PARC Main Ring includes replacement of RF cavities with higher field gradient using magnetic alloy cores, FT3L than the present ones. It also need to install the second harmonic RF cavity in the other section where dedicated water system for RF cavities is not available. Installation scenario of the second harmonic RF will be presented.

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MOPMW012

Study for a 162.5 MHz Window-Type RFQ

423

Q. Fu, P.P. Gan, S.L. Gao, F.J. Jia, H.P. Li, J. Liu, Y.R. Lu, Z. Wang, K. Zhu
PKU, Beijing, People's Republic of China

A window type of four vane radio-frequency quadrupole accelerator has been designed to accelerate 50 mA deuteron beam from 50 keV to 1 MeV. It will operate at 162.5 MHz in CW mode. Compared to the traditional four-vane RFQ, the window-type RFQ is more compact and has higher mode separation without π-mode stabilizing loops or dipole rods. A detailed full 3D model including vane modulation was developed. For the purpose of high shunt impedance, high quality factor and low power dissipation, the RF structure design was optimized by using electromagnetic simulations. Following the EM design optimization, an aluminium model of the window-type RFQ was fabricated and tested.

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MOPMW015

Wakefields Studies of High Gradient X-band Accelerating Structure at SINAP

429

SUPSS087

use link to see paper's listing under its alternate paper code

X.X. Huang, W. Fang, Q. Gu, M. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

Shanghai compact hard x-ray free electron laser (CHXFEL)* is now proposed accompanied with a high-gradient accelerating structure, which is the trend of large scale and compact facility. This structure operated at X-band (11424 MHz) holds the promise to achieve high gradient up to 80 MV/m. However, due to its particular property, a more serious wakefields** will be generated, leading to worse beam instability effects. In this paper, the computation of this case will be carried out with simulation. Moreover, analysis and optimization will be adopted to suppress beam instability.
* C. Feng, Z. T. Zhao, Chinese Sci Bull, 2010, 55, 221-227.
** K. Bane, SLAC, NLC-Note 9, Feb. 1995.

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MOPMW019

Resonant Frequency Control with RCCS for the KOMAC Proton Linac

435

D.H. Seo, Y.-S. Cho, H.S. Kim, H.-J. Kwon, K.T. Seol, Y.G. Song
Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea

Funding: This work is supported by the Ministry of Science, ICT & Future Planning of the Korean Government.
The Resonance control cooling systems (RCCS) of 100 MeV proton linac at the Korea multi-purpose accelerator complex (KOMAC) have been operated for cooling the drift tubes (DT) and controlling the resonant frequency of the drift tube linac (DTL). The RCCS can maintain the cooling water temperature within ±0.1 °C by controlling 3-way valve opening. The RCCS has two types of control mode, the constant cooling water temperature control mode and the resonant frequency control mode. In the case of the resonant frequency control, the error frequency is measured in the low-level RF (LLRF) control system and the RCCS compensates the error frequency by controlling the cooling water temperature of DT with PID algorithm. In this paper, the operation results of the resonant frequency control with the RCCS as well as some modification of the LLRF system are presented.

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MOPMW023

Optimization of the RF Cavity of a Low-energy Storage Ring for Thomson Scattering X-Ray Source

438

SUPSS090

use link to see paper's listing under its alternate paper code

L. Ovchinnikova, V.I. Shvedunov
SINP MSU, Moscow, Russia
A. Ryabov
IHEP, Moscow Region, Russia
V.I. Shvedunov
LEA MSU, Moscow, Russia

Results of optimization of the RF cavity of a low-energy storage ring for Thomson scattering X-ray source are presented. The geometry of 714 MHz RF cavity was optimized to provide maximum shunt impedance taking into account position of higher order modes (HOMs). The number and position of cooling channels were adjusted to minimize frequency shift due to cavity thermal deformations. The waveguide coupler and frequency tuner were calculated. Special attention was paid to detailed calculations of the HOMs parameter and to study of methods to minimize their influence on the storage ring beam dynamics.

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MOPMW024

Design of the New Wideband RF System for the CERN PS Booster

441

M.M. Paoluzzi, S.C.P. Albright, M.E. Angoletta, L. Arnaudon, S. Energico, A. Findlay, M. Haase, M. Jaussi, A.J. Jones, D. Landré, J.C. Molendijk, D. Quartullo, E.N. Shaposhnikova
CERN, Geneva, Switzerland

For the renovation and upgrade of the CERN PS Booster (PSB) RF systems a development project was launched in 2012. The design, based on a new approach, aimed at replacing the existing tuned, narrowband RF systems with wideband, modular, solid-state driven units. A wide range of issues had to be addressed spanning from RF power production, radiation hardness of solid-state devices, active cancellation of beam-induced voltages, dedicated low-level electronics allowing multi-harmonic operation and beam stability. Following a three-year prototyping and testing campaign and two international reviews, the project endorsement came at the end of year 2015. It foresees the complete removal of present h1, h2 and h10 systems and the deployment of a new one covering all the frequency ranges from 1 MHz to 18 MHz. The four PSB rings will be equipped with 144 identical acceleration cells providing 24 kV total RF voltage per ring. This paper describes the design concepts, the retained solutions, the expected performances and includes the procurement and implementation strategies. This activity is part of the LHC Injectors Upgrade project (LIU).

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MOPMW025

Vacuum RF Breakdown of Accelerating Cavities in Multi-Tesla Magnetic Fields

444

D.L. Bowring, A. Moretti, M.A. Palmer, D.W. Peterson, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
P.G. Lane, Y. Torun
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359.
Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures within multi-Tesla magnetic fields. The application of strong magnetic fields has been shown to lead to an increase in vacuum RF breakdown. This phenomenon imposes operational (i.e. gradient) limitations on cavities in ionization cooling channels, and has a bearing on the design and operation of other RF structures as well, such as photocathodes and klystrons. We present recent results from Fermilab's MuCool Test Area (MTA), in which 201 and 805 MHz cavities were operated at high power both with and without the presence of multi-Tesla magnetic fields. We present an analysis of damage due to breakdown in these cavities, as well as measurements related to dark current and their relation to a conceptual model describing breakdown phenomena.

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MOPMW026

Resonant Control for Fermilab's PXIE RFQ

447

D.L. Bowring, B.E. Chase, J. Czajkowski, J.P. Edelen, D.J. Nicklaus, J. Steimel, T.J. Zuchnik
Fermilab, Batavia, Illinois, USA
S. Biedron, A.L. Edelen, S.V. Milton
CSU, Fort Collins, Colorado, USA

Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359.
The RFQ for Fermilab's PXIE test program is designed to accelerate a < 10 mA H⁻ CW beam to 2.1 MeV. The RFQ has a four-vane design, with four modules brazed together for a total of 4.45 m in length. The RF power required is < 130 kW at 162.5 MHz. A 3 kHz limit on the maximum allowable frequency error is imposed by the RF amplifiers. This frequency constraint must be managed entirely through differential cooling of the RFQ's vanes and outer body and associated material expansion. Simulations indicate that the body and vane coolant temperature should be controlled to within 0.1 degrees C. We present the design of the cooling network and the resonant control algorithm for this structure, as well as results from initial operation.

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MOPMW027

Design of a Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster

451

C.-Y. Tan, J.E. Dey, K.L. Duel, R.L. Madrak, W. Pellico, E. Prebys, J. Reid, 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 and built for the Fermilab Booster. The purpose is to flatten the bucket at injection and thus change the longitudinal beam distribution to decrease space charge effects. It can also help with transition crossing. A model cavity has been built to verify various CST Microwave studio and COMSOL results and a test stand has been built to ensure that the Y567 tube is able to operate at twice the Booster fundamental frequencies. Also discussed are the RF windows which are critical to the design.

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MOPMW028

Progress on the MICE RF Module at LBNL

454

T.H. Luo, A.J. DeMello, A.R. Lambert, D. Li, T.J. Loew, S. Prestemon, S.P. Virostek, J.G. Wallig
LBNL, Berkeley, California, USA
T.G. Anderson, A.D. Bross, M.A. Palmer
Fermilab, Batavia, Illinois, USA
Y. Torun
IIT, Chicago, Illinois, USA

The international Muon Ionization Cooling Experiment aims to demonstrate the transverse cooling of a muon 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 assembly of MICE RF Module is being carried out at LBL. In this paper we will report the recent progress on the assembly work.

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MOPMW029

Analysis of Transverse Field Induced by Curved Beryllium Window in Muon Ionization Cooling Cavity

457

T.H. Luo, D. Li
LBNL, Berkeley, California, USA

The beryllium windows are used in muon ionization cooling cavity to increase the cavity shunt impedance. The windows are curved for predictable thermal deformation. This curvature also introduces transverse field, which will affect the transverse beam emittance. In this paper, we will analyze this transverse field and evaluate its effect on the emittance cooling.

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MOPMW030

High Powered Tests of Dielectric Loaded High Pressure RF Cavities for Use in Muon Cooling Channels

460

B.T. Freemire
IIT, Chicago, Illinois, USA
D.L. Bowring, A. Moretti, D.W. Peterson, A.V. Tollestrup, Y. Torun, K. Yonehara
Fermilab, Batavia, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: This work is supported by the Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359.
Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. Alumina of purities ranging from 96 to 99.8% was tested in a high pressure RF test cell at the MuCool Test Area at Fermilab. The results of breakdown studies with pure nitrogen gas, and oxygen-doped nitrogen gas indicate the peak surface electric field on the alumina ranges between 10 and 15 MV/m. How these results affect the design of a prototype cooling channel cavity will be discussed.

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MOPMW031

Beam Test of a Dielectric Loaded High Pressure RF Cavity for Use in Muon Cooling Channels

463

B.T. Freemire
IIT, Chicago, Illinois, USA
D.L. Bowring, A. Moretti, D.W. Peterson, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: This work is supported by the Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359.
Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. A 99.5% alumina ring was inserted in a high pressure RF test cell and subjected to an intense proton beam at the MuCool Test Area at Fermilab. The results of the performance of this dielectric loaded high pressure RF cavity will be presented.

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MOPMW032

Study of RF Breakdown in 805MHz Pillbox Modular Cavity in Strong Magnetic Field

466

A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
D.L. Bowring, A. Moretti, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

RF breakdown has a negative impact on a cavity's performance, especially with the presence of strong magnetic fields. This issue can arise in designs of muon ionization cooling channel, RF guns, klystrons and in many other applications. The MuCool Test Area at Fermilab is the facility that allows us to study the effects of static magnetic field on RF cavity operation. As a part of this research program, we have tested an 805MHz pillbox "modular" cavity in strong external magnetic fields. The design of the cavity allowed for a better control over sources of systematic error. "Modular" structure of the cavity enables easy dismounting of the endplates to perform inspection of inner surfaces after each run as well as swapping endplates to study the effects of various materials on breakdown phenomenon. Coupler design ensures maximum electric field enhancement on cavity axis, thus reducing breakdown probability in the coupler region. The results and analysis from high-power runs with zero and non-zero external magnetic fields will be presented.

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MOPMW033

Acoustic Localization of RF Cavity Breakdown: Status and Progress

470

P.G. Lane, P. Snopok, Y. Torun
Illinois Institute of Technology, Chicago, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA

Current designs for muon accelerators require high-gradient RF cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. It has been found that placing normal conducting RF cavities in strong magnetic fields 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 localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to a small region of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Presented here are the algorithms for and results from localizing simulated and experimental acoustic data from the Modular Cavity at the MuCool Test Area at Fermilab.

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MOPMW034

Final Commissioning of the MICE RF Module Prototype with Production Couplers

474

Y. Torun, P.G. Lane
Illinois Institute of Technology, Chicago, Illlinois, USA
T.G. Anderson, M. Backfish, D.L. Bowring, A. Moretti, D.V. Neuffer, D.W. Peterson, M. Popovic, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
T.L. Hart
UMiss, University, Mississippi, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
T.H. Luo
LBNL, Berkeley, California, USA

Funding: Supported by the US Department of Energy Office of Science through the Muon Accelerator Program.
We report operational experience from the prototype RF module for the Muon Ionization Cooling Experiment (MICE) with final production couplers at Fermilab's MuCool Test Area. This is the last step in fully qualifying the RF modules for operation in the experiment at RAL.

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MOPMW035

Wakefield Excitation in Power Extraction Cavity (PEC) of Co-linear X-band Energy Booster (CXEB) in Time Domain (T3P) with ACE3P

477

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

In our previous papers we provided the general concept and the design details of our proposed Co-linear X-band Energy Booster (CXEB) as well as more advanced 3D simulations of our system using the frequency domain solvers OMEGA3P and S3P of the ACE3P Suite. Here, using the time domain solver T3P of ACE3P, we provide the single bunch and multiple bunch wakefield excitations resulting from a Gaussian bunch. The related power extraction mechanism for our traveling wave (TW) X-band power extraction cavity (PEC) are also discussed further.

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MOPMW036

Frequency Domain Simulations of Co-linear X-band Energy Booster (CXEB) RF Cavity Structures and Passive RF Components with ACE3P

480

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, and this can lead to more compact light sources. At the Colorado State University Accelerator Laboratory (CSUAL) [1] we would like to adapt this technology to our 1.3-GHz, L-band accelerator system using a passively driven 11.7 GHz traveling wave X-band configuration that capitalizes on the high shunt impedances achievable in X-band accelerating structures 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 comparisons of the important parameters achieved using SUPERFISH and OMEGA3P for our Co-linear X-band Energy Booster (XCEB) system that will allow us to achieve our goal of reaching the maximum practical net potential across the X-band accelerating structures while driven solely by the beam from the L-band system.

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MOPMW038

Measurements of Copper RF Surface Resistance at Cryogenic Temperatures for Applications to X-Band and S-Band Accelerators

487

A.D. Cahill, A. Fukasawa, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
G.B. Bowden, V.A. Dolgashev, M.A. Franzi, S.G. Tantawi, P.B. Welander, C. Yoneda
SLAC, Menlo Park, California, USA
J. Guo
JLab, Newport News, Virginia, USA
Y. Higashi
OIST, Onna-son, Okinawa, Japan

Funding: Funding from DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515
Recent SLAC experiments with cryogenically cooled X-Band standing wave copper accelerating cavities have shown that these structures can operate with accelerating gradients of ~250 MV/m and low breakdown rates. These results prompted us to perform systematic studies of copper rf properties at cryogenic temperatures and low rf power. We placed copper cavities into a cryostat cooled by a pulse tube cryocooler, so cavities could be cooled to 4K. We used different shapes of cavities for the X-Band and S-Band measurements. Properties of the cavities were measured using a network analyzer. We calculated rf surface resistance from measured Q0 and Q external of the cavity at temperatures from 4 K to room temperature. The results were then compared to the theory proposed by Reuter and Sondheimer. These measurements are a part of studies with the goal of reaching very high operational accelerating gradients in normal conducting rf structures.

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MOPMW039

TM01 Mode Launcher for Use in High Brightness Photoguns

491

A.D. Cahill
UCLA, Los Angeles, California, USA
M. Dal Forno, V.A. Dolgashev
SLAC, Menlo Park, California, USA

Funding: DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515
Photo rf guns are a source of electron beams for X-ray FELs such as LCLS and European XFEL. In existing photoguns power is coupled into the cavity by waveguides through the cell walls, like LCLS, or through coaxial coupling, at the European XFEL. We are considering feeding a gun using a circular waveguide with the TM01 mode. To do that we need a mode launcher, a matched device that couples the rectangular TE01 mode waveguide to a TM01 mode in a circular waveguide. Use of the mode launcher reduces complexity of the gun cavity and increases flexibility of positioning the input waveguide relative to the gun body. Mode launchers have been successfully used at SLAC and elsewhere for X-band high gradient tests. Because the existing mode launchers were not built for high brightness guns, they have a significant quadrupole field component. High brightness rf guns have tight requirements on output beam properties, and this quadrupole component adversely affects the beam. We have designed a mode launcher free of this disadvantage. We present design considerations, methodology, and an example S-band mode launcher.

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MOPMW040

Electron Beam Excitation of a Surface Wave in mm-Wave Open Accelerating Structures

494

M. Dal Forno, G.B. Bowden, C.I. Clarke, V.A. Dolgashev, M.J. Hogan, D.J. McCormick, A. Novokhatski, B.D. O'Shea, S.G. Tantawi, S.P. Weathersby
SLAC, Menlo Park, California, USA
B. Spataro
INFN/LNF, Frascati (Roma), Italy

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
As part of research on the physics of rf breakdowns we performed experiments with high gradient traveling-wave mm-wave accelerating structures. The accelerating structures are open, composed of two identical halves separated by an adjustable gap. The electromagnetic fields are excited by an ultra-relativistic electron beam. We observed that a confined travelling-wave mode exists in half of the accelerating structure. The experiments were conducted at FACET facility at SLAC National Accelerator Laboratory. Depending on the gap width, the accelerating structure had beam-synchronous frequencies that vary from 90 to 140 GHz. When we opened the gap by more than half wavelength the synchronous wave remains trapped. Its behavior is consistent with the so called "surface wave". We characterized this beam-wave interaction by several methods: measurement of the radiated rf energy with the pyro-detector, measurement of the spectrum with an interferometer, measurement of the beam deflection by using the beam position monitors and profile monitor.

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MOPMW041

Measurements of RF Breakdowns in Beam Driven mm-Wave Accelerating Structures

497

M. Dal Forno, G.B. Bowden, C.I. Clarke, V.A. Dolgashev, M.J. Hogan, D.J. McCormick, A. Novokhatski, S.G. Tantawi, S.P. Weathersby
SLAC, Menlo Park, California, USA
B. Spataro
INFN/LNF, Frascati (Roma), Italy

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515
We studied the physics and properties of rf breakdowns in high gradient traveling-wave accelerating structures at 100 GHz. The structures are open, made of two halves with a gap in between. The rf fields were excited in the structure by an ultra-relativistic electron beam generated by the FACET facility at the SLAC National Accelerator Laboratory. We observed rf breakdowns generated in the presence of GV/m scale electric fields. We varied the rf fields excited by the FACET bunch by moving structure relative to the beam and by changing the gap between structure halves. Reliable breakdowns detectors allowed us to measure the rf breakdown rate at these different rf parameters. We measured radiated rf energy with a pyro-detector. When the beam was off-axis, we observed beam deflection in the beam position monitors and on the screen of a magnetic spectrometer. The measurements of the deflection allowed us to verify our calculation of the accelerating gradient.

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MOPMW043

Overview of High Power Vacuum Dry RF Load Designs

504

A.K. Krasnykh, A. Brachmann, F.-J. Decker, T.J. Maxwell, J. Sheppard
SLAC, Menlo Park, California, USA

Funding: Work supported by US Department of Energy under contract DE-AC02-76SF00515
A specific feature of RF linacs based on the pulsed traveling wave (TW) mode of operation is that only a portion of the RF energy is used for the beam acceleration. The residual RF energy has to be terminated into an RF load. Higher accelerating gradients require higher RF sources and RF loads, which can stably terminate the residual RF power. This overview will outline vacuumed RF loads only. A common method to terminate multi-MW RF power is to use circulated water (or other liquid) as an absorbing medium. A solid dielectric interface (a high quality ceramic) is required to separate vacuum and liquid RF absorber mediums. Using such RF load approaches in TW linacs is troubling because there is a fragile ceramic window barrier and a failure could become catastrophic for linac vacuum and RF systems. Traditional loads comprising of a ceramic disk have limited peak and average power handling capability and are therefore not suitable for high gradient TW linacs. This overview will focus on 'vacuum dry' or 'all-metal' loads that do not employ any dielectric interface between vacuum and absorber. The first prototype is an original design of RF loads for the Stanford Two-Mile Accelerator.

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MOPMW044

Design of an RF Device to Study the Multipactor Phenomenon

507

SUPSS115

use link to see paper's listing under its alternate paper code

D. Amorim
Grenoble-INP Phelma, Grenoble, France
J.-M. De Conto, Y. Gómez Martínez
LPSC, Grenoble Cedex, France

Multipacting is a parasitic electron avalanche process that may occur in RF devices such as cavities or couplers. As it can be detrimental to the operation of these devices, the accelerator group at LPSC is currently designing a coaxial resonant cavity in order to study this phenomenon. In order to determine the measurable parameters on the cavity, calculations were performed and validated with numerical simulations. In a second time multipacting simulations were conducted to determine if the experiment will allow to observe multipacting.

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MOPMY001

Beam Dynamics Analysis for the Ultra-fast Kicker in Circular Cooler Ring of JLEIC

510

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.
An ultra-fast kicker system consist of four quarter wavelength resonator based deflecting cavities was developed that simultaneously resonates at 10 subharmonic modes of the 476.3MHz bunch repetition frequency, thus every 10th bunch in the bunch train will experience a transverse kick while all the other bunches are undisturbed. This fast kicker is developed for the Energy Recovery Linac (ERL) based electron Circular Cooler Ring (CCR) in the proposed Jefferson Lab Electron Ion Collider (JLEIC, previously MEIC). The electron bunches can be reused 10-30 turns thus the beam current in the ERL can be reduced to 1/10 - 1/30 (150mA - 50mA) of the cooling bunch current (1.5A). In this paper, several methods to synthesis such a kicker waveform will be discussed with the comparison of beam dynamics tracking in Elegant.

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MOPMY005

Study of Pretuning and High Power Test of DTL Iris Waveguide Couplers Using a Single Cell Cavity

522

S.W. Lee, M.S. Champion, Y.W. Kang
ORNL, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S.DOE.
Six drift tube linac (DTL) cavities have been operating successfully at the Spallation Neutron Source (SNS). Each cavity is fed by a tapered ridge waveguide iris input coupler and a waveguide ceramic disk window. The original couplers and cavities have been in service for more than a decade. Design optimization and tuning of the couplers were initially performed prior to installation and commissioning of the cavities. Since each DTL cavity is unique, expensive, and fully utilized for neutron production, none of the cavity structure is available as a test cavity or a spare. Maintaining spares for operations and for future system upgrade, test setup of the iris couplers for precision tuning is needed. Ideally a smaller cavity structure may be used for pretuning and RF conditioning of the iris couplers as a test cavity or a bridge waveguide. In this paper, study of using a single cell cavity for the iris tuning and conditioning is presented along with the 3D simulation results.

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MOPMY007

Mechanical Design and 3-D Coupled RF, Thermal-Structural Analysis of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac

525

J.C. Brutus, S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, A.V. Fedotov, M.C. Grau, C. Pai, L. Snydstrup, J.E. Tuozzolo, B. P. Xiao, T. Xin, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, 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.
Two normal conducting cavities operating at 704 MHz and 2.1 GHz will be used for the Low Energy RHIC electron Cooling (LEReC) under development at BNL to improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon. The single cell 704 MHz cavity and the 3-cell 2.1 GHz third harmonic cavity will be used in LEReC to correct the energy spread introduced in the SRF cavity. The successful operation of normal RF cavities has to satisfy both RF and mechanical requirements. 3-D coupled RF-thermal-structural analysis has been performed on the cavities to confirm the structural stability and to minimize the frequency shift resulting from thermal and structural expansion. In this paper, we will present an overview of the mechanical design, results from the RF-thermal-mechanical analysis, progress on the fabrication and schedule for the normal conducting RF cavities for LEReC.

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MOPMY009

HOM Consideration of 704 MHz and 2.1 GHz Cavities for LEReC Linac

528

B. P. Xiao, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, J.C. Brutus, A.V. Fedotov, H. Hahn, G.T. McIntyre, C. Pai, K.S. Smith, J.E. Tuozzolo, Q. Wu, T. Xin, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh
Fermilab, Batavia, Illinois, 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 supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under development at BNL. The Linac of LEReC is designed to deliver 2 MV to 5 MV electron beam, with rms dp/p less than 5·10^-4. The HOM in this Linac is carefully studied to ensure this specification.

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MOPMY010

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

532

B. P. Xiao, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, J.C. Brutus, A.V. Fedotov, H. Hahn, G.T. McIntyre, C. Pai, K.S. Smith, J.E. Tuozzolo, Q. Wu, T. Xin, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh
Fermilab, Batavia, Illinois, USA
S.A. Belomestnykh, I. Ben-Zvi, T. Xin
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 supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy 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 energy spread correction. Currently these two cavities are under fabrication. In this paper we report the RF design of these two cavities.

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MOPMY033

Effect of Bandwidth of Low Level Radio Frequency System on the Instability of an Electron Beam

570

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

The analog Low Level Radio Frequency (LLRF) system is used at Taiwan Photon Source (TPS) RF system. It is composed of three feedback loops to control the amplitude and phase of accelerating field and the frequency of RF cavity. Instability of electron beam and accelerating field due to the bandwidth of LLRF system were observed during the TPS commissioning. This effect was studied and the results will be presented in this paper.

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MOPOR013

The PS 10 MHz High Level RF System Upgrade

622

G. Favia, H. Damerau, V.D. Desquiens, S. Energico, M. Morvillo, D. Perrelet, C. Rossi
CERN, Geneva, Switzerland

In view of the upgrade of the injectors for the High Luminosity LHC, significantly higher bunch intensity is required for LHC-type beams. In this context an upgrade of the main accelerating RF system of the Proton Synchrotron (PS) is necessary, aiming at reducing the cavity impedance which is the source of longitudinal coupled-bunch oscillations. These instabilities pose as a major limitation for the increase of the beam intensity as planned after LS2. The 10 MHz RF system consists in 11 ferrite loaded cavities, driven by tube-based power amplifiers for reasons of radiation hardness. The cavity-amplifier system is equipped with a wide-band feedback that reduces the beam induced voltage. A further reduction of the beam loading is foreseen by upgrading the feedback system, which can be reasonably achieved by increasing the loop gain of the existing amplification chain. This paper describes the progress of the design of the upgraded feedback system and shows the results of the tests on the new amplifier prototype, installed in the PS during the 2015-16 technical stop. It also reports the first results of its performance with beam, observed in the beginning of the 2016 run.

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MOPOY054

Status of the ESS RFQ

974

D. Chirpaz-Cerbat, A. Albéri, A.C. Chauveau, M. Lacroix, N. Misiara, G. Perreu, O. Piquet, H. Przybilski, N. Sellami
CEA/IRFU, Gif-sur-Yvette, France
N. Berton, G. Bourdelle, M. Desmons, A.C. France, V.M. Hennion, P.-A. Leroy, B. Pottin
CEA/DSM/IRFU, France

The ESS Radio-Frequency Quadrupole (RFQ) is a 4-vanes resonant cavity designed at the frequency of 352.21 MHz. It must accelerate and bunch a 70mA proton beams from 75keV to 3.62MeV with a 4% duty cycle. The RFQ design has already been done, and documented in other papers. This one will present the global status of the RFQ, with technical solutions cho-sen for the main components (for fabrication and op-eration) and the present status of the RFQ fabrication.

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WEPMB008

ESS DTL Mechanical Design and Prototyping.

2131

P. Mereu, M. Mezzano
INFN-Torino, Torino, Italy
D. Castronovo, R. Visintini
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
F. Grespan, A. Pisent, M. Poggi, C. R. Roncolato
INFN/LNL, Legnaro (PD), Italy

The Drift Tube Linac (DTL) of the European Spallation Source (ESS) is designed to operate at 352.2 MHz with a duty cycle of 4% (3 ms pulse length, 14 Hz repetition period) and will accelerate a proton beam of 62.5 mA pulse peak current from 3.62 to 90 MeV. In this paper the DTL mechanical design and simulations are presented, together with the results obtained from the prototypes of three drift tubes, equipped respectively with Permanent Magnet Quadrupole, Steerer and Beam Position Monitor.

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