IHEP Beijing, Beijing
BEPCII is major upgrades of BEPC (Beijing Electron-Positron Collider). It is a double ring e±e collider as well as a synchrotron radiation (SR) source with its outer ring, or SR ring. As a collider, BEPCII operates in the beam energy region of 1-2.1 GeV with design luminosity of 1*1033cm-2s-1 at 1.89 GeV. As a light source, the SR ring operates at 2.5 GeV and 250 mA. Construction of the project started in the beginning of 2004. Installation of the storage ring components completed in October 2007. The BESIII detector was moved to the Interaction Region (IR) on May 6, 2008. In accordance to the progress of construction, the beam commissioning of BEPCII is carried out in 3 phases: Phase 1, with conventional magnets instead of the superconducting insertion magnets (SIM’s)n in the IR; Phase 2, with SIM’s in the IR; Phase 3, joint commissioning with the detector. The maximum luminosity reached to 2.3*1032cm-2s-1. This paper summarizes progress of the construction and commissioning in 3 phases, while focusing on the third phase.
* On behalf of the BEPCII Team
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) is a third-generation storage-ring-based x-ray source that has been operating for more than 11 years and is enjoying a long period of stable, reliable operation. While APS is presently providing state-of-the-art performance to its large user community, we must clearly plan for improvements and upgrades to stay at the forefront scientifically. Significant improvements should be possible through upgrades of beamline optics, detectors, and end-station equipment, along with local, evolutionary changes to the storage ring itself. However, major accelerator upgrades are also being investigated. One very promising option that has been the subject of considerable research is the use of an energy recovery linac. In this option, APS would transition from a source based on a stored electron beam to one based on a continuously generated high-brightness electron beam from a linac. Such a source promises dramatically improved brightness and transverse coherence compared to third-generation storage rings, as well as distinctly different temporal properties.
NSCL, East Lansing, Michigan
The 2007 Long Range Plan for Nuclear Science had as one of its highest recommendations the “construction of a Facility for Rare Isotope Beams (FRIB) a world-leading facility for the study of nuclear structure, reactions, and astrophysics. Experiments with the new isotopes produced at FRIB will lead to a comprehensive description of nuclei, elucidate the origin of the elements in the cosmos, provide an understanding of matter in the crust of neutron stars, and establish the scientific foundation for innovative applications of nuclear science to society.” A heavy-ion driver linac will be used to provide stable beams of >200 MeV/u at beam powers up to 400 kW that will be used to produce rare isotopes. Experiments can be done with rare isotope beams at velocities similar to the driver linac beam, at near zero velocities after stopping in a gas cell, or at intermediate (0.3 to 10 MeV/u) velocities through reacceleration. An overview of the design proposed for implementation on the campus of Michigan State University leveraging the existing infrastructure will be presented.
BNL, Upton, Long Island, New York
CERN, Geneva
Lancaster University, Lancaster
KEK, Ibaraki
SLAC, Menlo Park, California
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
LBNL, Berkeley, California
Fermilab, Batavia
Funding: This work was partially performed under the auspices of the US DOE and the European Community-Research Infrastructure, FP6 programme (CARE, contract number RII3-CT-2003-506395)}
The LHC crab cavity program is advancing rapidly towards a first prototype which is anticipated to be tested during the early stages of the LHC phase I upgrade and commissioning. Some aspects related to crab optics, collimation, aperture constraints, impedances, noise effects, beam transparency and machine protection critical for a safe and robust operation of LHC beams with crab cavities are addressed here.
JAEA/ERL, Ibaraki
Energy Recovery Linacs (ERL) have been successfully operated in three high-power FEL facilities, Jefferson Laboratory (JLAB) IR FEL Upgrade, Japan Atomic Energy Agency (JAEA) FEL and Budker Institute of Nuclear Physics (BINP) THz FEL. The ERLs are now considered a promising candidate for uses as high-power FELs, synchrotron radiation sources, electron cooling devices, electron-ion colliders and Compton X/gamma-ray sources. All these applications are based on the excellent feature of the ERL that is simultaneous attainment of multiple beam parameters: small emittance, short bunch duration and high-average current. In order to overcome technological challenges and realize the above future ERL applications, several R&D efforts have been launched in the world. In this paper, we overview the current status of these R&D programs and envision the future of ERLs.
BINP SB RAS, Novosibirsk
The first stage of Novosibirsk high power free electron laser (FEL) is in operation since 2003. Now the FEL provides average power up to 500 W in the wavelength range 120 - 240 micron. One orbit for 11-MeV energy with terahertz FEL lies in vertical plane. Other four orbits lie in the horizontal plane. The beam is directed to these orbits by switching on of two round magnets. In this case electrons pass four times through accelerating RF cavities, obtaining 40-MeV energy. Then, (at fourth orbit) the beam is used in FEL, and then is decelerated four times. At the second orbit (20 MeV) we have bypass with third FEL. When magnets of bypass are switched on, the beam passes through this FEL. The length of bypass is chosen to provide the delay, which necessary to have deceleration instead of acceleration at the third passage through accelerating cavities. Now two of four horizontal orbits are assembled and commissioned. The electron beam was accelerated twice and then decelerated down to low injection energy. Project average current 9 mA was achieved. First multi-orbit ERL operation was demonstrated successfully.
CIAE, Beijing
CYCIAE-100 is a 100 MeV, 200 muA H- cyclotron being constructed at CIAE. The tolerance of the magnetic field is as tight as 1.2 Gauss for isochronous field and 2 Gauss for first harmonics. Due to the absence of coil adjusting in this machine, a measure that helps to achieve a more compact structure (435 ton for the main magnet), the imperfection hence becomes a much more critical factor in our consideration. The effects by the various kinds of imperfection are investigated numerically and the imperfection fields are predicted for beam dynamics simulation, serving as a basic guidance in the magnet construction for CYCIAE-100. Some of the important results will be reported in this paper, including
- the deformation of the main magnet by the gravity itself, 480 ton EM force and 120 ton vacuum pressure,
- segregation, inclusion and contraction cavity induced by the casting procedure,
- fabrication and assembling tolerance, and
- thermal deformation.
CIAE, Beijing
TUB, Beijing
To limit the cost for the main magnet of a compact cyclotron CYCIAE-100, the cast steel is used for the top/bottom yoke and return yoke. The imperfection may not be ignored and the harmonic coils on the return yokes will make the fields reaching the requirements easier during the shimming. The centering coils will not only compensate the 1st harmonic fields at the center region, which is usually remain big, but also correct the off-center injection of the beam. The thermal deformation and the vacuum pressure may change the fields distribution during the machine operation and therefore It is necessary to use trim coils to adjust the fields. We arrange the trim coils inside the two opposite valleys of the main magnet. The second harmonics from the trim coils are not big eough to affect the beam dynamics significantly from the beam dynamics study. In this paper, the effects of correction coils of three types are presented. The detail configuration of the correction coils is introduced in the paper as well. One concern is the potential interference of some water cooled coils could have with vacuum. Some experience for the coils inside the high vacuum tank is tested and the results are given.
Fermilab, Batavia
Funding: Department of Energy, U.S.A.
A novel prototype of SCRF cavity tuner is being designed and tested at Fermilab. This is a superconducting C-type iron dominated magnet having a 10 mm gap, axial symmetry, and a 1 Tesla field. Inside the gap is mounted a superconducting coil capable of moving ± 1 mm and producing a longitudinal force up to ± 1.5 kN. The static force applied to the RF cavity flanges provides a long- term cavity geometry tuning to a nominal frequency. The same coil powered by a fast AC current pulse delivers mechanical perturbation for fast cavity tuning. This fast mechanical perturbation could be used to compensate a dynamic RF cavity detuning caused by cavity Lorentz forces and microphonics. A special configuration of magnet system was designed and tested.
Fermilab, Batavia
Muons, Inc, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-07ER84825 and by FRA under DOE Contract DE-AC02-07CH11359
The helical cooling channel is proposed to make a quick muon beam phase space cooling in a short channel length. The challenging part of the helical cooling channel magnet design is how to integrate the RF cavity into the compact helical cooling magnet. This report shows the possibility of the integration of the system.
LBNL, Berkeley, California
Fermilab, Batavia
BNL, Upton, Long Island, New York
Funding: This work was supported in part by the Director, Office of Science, High Energy Physics, U.S. Department of Energy under contract No. DE-AC02-05CH11231
Pushing accelerator magnets beyond 10 T holds a promise of future upgrades to machines like the Large Hadron Collider (LHC) at CERN. Nb3Sn conductor is at the present time the only practical superconductor capable of generating fields beyond 10 T. In support of the LHC Phase-II upgrade, the US LHC Accelerator Research Program (LARP) is developing a large bore (120mm) IR quadrupole (HQ) capable of reaching 15 T at its conductor peak field. The 1 m long two-layer coil, based on the design of the LARP TQ quadrupole series that achieved 230 T/m in a 90 mm bore, will demonstrate additional features such as alignment and accelerator field quality while exploring the magnet performance limits in terms of gradient, forces and stresses. In this paper we summarize the design and report on the magnet construction progress.
LBNL, Berkeley, California
ICST, Harbin
UMiss, University, Mississippi
Funding: This work is supported by funds under the “985-2” plan of HIT. This work is also supported by the Office of Science, US-DOE under DOE contract DE-AC02-05CH11231 and by NSF through NSF-MRI-0722656.
The superconducting coupling solenoid for MuCOOL and MICE will have an inside radius of 750 mm, and a coil length of 285 mm. The MuCOOL coupling coil is identical to the MICE coupling coils. The MICE coupling magnet will have a self inductance of 592 H. When operated at it maximum design current of 210 A (the highest momentum operation of MICE), the magnet stored energy will be about 13 MJ. These magnets will be kept cold using a pair of pulse tube cryocoolers that deliver 1.5 W at 4.2 K and 55 W at 60 K. This report describes the progress on the MuCOOL and MICE coupling magnet design and engineering. The progress on the construction of the first coupling coil will also be presented.
ESRF, Grenoble
This paper outlines the present status and configuration of the ESRF vacuum system and its performance over the last years. A short overview of the installed vacuum devices is given as well as an outlook of future developments towards the planned ESRF upgrade. The storage ring down times caused by vacuum accidents have been dramatically improved due to a systematical survey using advanced vacuum diagnostic tools. Their use and drawbacks will also be discussed in this paper.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An energy recovery linac (ERL) is a potential candidate for an Advanced Photon Source (APS) upgrade at Argonne National Laboratory. A high-DC-voltage photocathode-gun-based electron injector* was previously investigated to meet the ultra-low emittance requirement. Recently the modeling was extended to include a merger using the fully three-dimensional tracking simulation code IMPACT-T. A multiobjective numerical optimization was performed with the goal of delivering a 10-MeV, 19-pC bunch with a normalized transverse emittance less than 0.1 μm at the entrance of the linac. In this paper we show the optimum performance obtained.
*Y.-E. Sun et al., ”Optimization of a DC Injector for an Energy Recovery Linac Upgrade to the Advanced Photon Source”, Proc. of LINAC 2008, TUP100, to be published on http://www.jacow.org.
ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
The concept of an ultra-low transverse emittance injector operating in CW mode for an XFELO* was discussed at LINAC-08**. Here we will report the design optimization of the injector, which includes a 100 MHz RF-gun with thermionic cathode, an energy filter to produce short bunches (~0.5 nsec), a velocity bunching section, higher harmonic cavities to minimize longitudinal emittance, two bunch compressors and accelerating sections operating at 400 MHz and 1300 MHz to obtain 540 MeV electrons. The proposed design is capable of producing 40 pC bunches with 0.5 psec rms time width and 0.7 MeV rms energy spread. Most significantly, the transverse rms emittance is kept below 0.11 π μm. The longitudinal emittance and bunch time width can be substantially reduced for low-charge bunches of several pC.
*K.-J. Kim, Y. Shvyd’ko, and S. Reiche, Phys. Rev. Lett., 100 244802 (2008).
**P.N. Ostroumov, K.-J. Kim, Ph. Piot, Proceedings of the Linac-2008.
ANL, Argonne
Funding: This work was supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Low-frequency normal-conducting photoinjectors have the potential to generate CW beam due to low frequency and relatively low field. They can provide a much higher accelerating field at the cathode than envisioned DC injectors but without the complexity involved in superconducting rf injectors. Low frequency allows a relatively long bunch near the cathode to reduce space-charge effects, which is detrimental for generating demandingly high-brightness beams. However, low frequency means higher bunch charge for a given average current, counteracting the potential benefits of low-frequency rf injectors. Furthermore, significant bunch length reduction in the injectors is often needed, which may degrade transverse brightness. To explore the potential of a normal-conducting injector for the envisioned ERL upgrade of the Advanced Photon Source, we made a preliminary design and searched for a suitable solution using genetic optimization. Simulation results are presented.
DULY Research Inc., Rancho Palos Verdes, California
A Gallium Arsenide (GaAs) photocathode RF electron gun is useful if high polarization (>85%) and low emittance are required as, for example, in the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility. DULY Research is developing a normal-conducting, L-band photoelectron gun in an ultra high vacuum accelerating structure called the Plane-Wave-Transformer (PWT) integrated with an activated, strained-lattice GaAs photocathode, as a continuous wave polarized electron source. We compare two designs (1-cell and ½ cell) of an L-Band PWT photoelectron gun in this paper. This RF gun will simplify the CEBAF photoinjector design by replacing the direct current (DC) gun, buncher cavities and the capture section. The new compact design provides a stiffer beam that is less subject to space charge blowup. In addition, a higher field gradient at the photocathode would mitigate electron and ion backbombardment problems. Cooling for a CW PWT gun is challenging but manageable.
DESY, Hamburg
JLAB, Newport News, Virginia
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
In this contribution, we report progress on the development of a hybrid lead/niobium superconducting RF (SRF) photoinjector. The goal of this effort is to build a Nb injector with the superconducting cathode made of lead, which demonstrated in the past superior quantum efficiency (QE) compared to Nb Three prototype hybrid devices, consisting of an all-niobium cavity with an arc-deposited spot of lead in the cathode region, have been constructed and tested. We present the cold test results of these cavities with and without lead.
Diamond, Oxfordshire
For the successful operation of an X-ray free electron laser the injector must be robust and able to provide a high quality beam. In this paper we present the design of a normal conducting L-band photoinjector which is based on the successful DESY/PITZ gun, but with improved cavity geometry. The result of beam dynamics simulations predicts that a beam with a normalized transverse emittance of less than 0.7 mm mrad at 1 nC can be produced. With an expected repetition rate of at least 1 kHz this gun meets the requirements of the first stage injector for the UK's New Light Source project.
Diamond, Oxfordshire
To precisely control the electron beam parameters from a photocathode RF gun, the RF field distribution during real RF operation must be known. During RF operation, the RF field induces local RF heating on the cavity surface. This non-uniform temperature distribution may deform the cavity and affect the output beam parameters. Here, we model a copper RF gun cavity and calculate the temperature distribution and the stress over the cavity surface. Then, the beam parameter change caused by the cavity deformation is simulated.
KEK, Ibaraki
JAEA/ERL, Ibaraki
The compact ERL, cERL, is a project to test an energy recovery linac (ERL) with 60 MeV and 100 mA electron beam to generate synchrotron radiation with smaller emittance and shorter pulse length. The design work of the cERL injector has been carried out using a space charge simulation code. The injector consists of 500 kV photo cathode DC gun, two solenoid magnets, buncher cavity, three super conducting RF cavities and merger section to return pass. It generates an electron beam with -77 pC bunch charge and 1.3 GHz repetition rate. Our target value of emittance is less than 1 mm mrad with the bunch length of 1 mm at the exit of the injector. The parameter optimization of the injector using the multi objected method has been carried out to obtain the minimum emittance. The simulation results will be presented in detail.
LBNL, Berkeley, California
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
A high-brightness high-repetition rate photo-injector based on a normal conducting 187 MHz RF cavity design capable of CW operation is under construction at the Lawrence Berkeley National Laboratory. A cathode field of ~20 MV/m accelerates electron bunches to 750 keV with peak current, energy spread and transverse emittance suitable for FEL and ERL applications. A vacuum load-lock mechanism is included and a 10 picoTorr range vacuum capability allows most types of photocathodes to operate at a MHz repetition rate with present laser technology. The status of the project is presented.
PKU/IHIP, Beijing
High quality electron beam with low transverse emittance in 3.5‐cell DC‐SC photo‐injector is crucial significance for PKU‐ERL‐FEL facility. In this paper, we analyse the emittance evolution in the 3.5‐cell DC‐SC photo‐injector by simply model with consideration of DC acceleration, RF acceleration and space charge effect. The results are compared with Astra simulation. The matching condition of DC‐gun and Superconducting cavity, which is critical for the final emittance at the exit of the injector, is also presented.
Pulsar Physics, Eindhoven
TUE, Eindhoven
Delft University of Technology, Opto-electronic Section, Delft
Three different S-band rf-photoguns have been constructed by Eindhoven University of Technology in the Netherlands: A 1.5-cell, a 100 Hz 1.6-cell, and a 2.6-cell. They share a design concept that differs from the ‘standard’ BNL-gun in many aspects: Individual cells are clamped and not brazed saving valuable manufacturing time and allowing damaged parts to be replaced individually. The inner geometry employs axial incoupling, inspired by DESY, to eliminate any non-cylindrically symmetric modes. Elliptical irises, identical to a 2.6-cell design of Strathclyde University, reduce the maximum field on the irises and thereby reduce electrical breakdown problems. The manufacturing process uses single-point diamond turning based on a micrometer-precise design. The overall precision is such that the clamped cavities are spot-on resonance and have near-perfect field balance without the need for any post-production tuning. Operational performance of the three Dutch rf-photoguns will be presented.
BINP SB RAS, Novosibirsk
The projected electron RF gun of Novosibirsk Microtron-Recuperator injector employs an industrial thermionic cathode grid assembly with 0.08 mm gap that usually used in metal-ceramic RF tubes. Three-dimensional (3D)computer simulations have been performed that use the mesh refinement capability of the both Microwave Studio and 2D SAM codes to examine the full region of the real cathode grid assembly in static fields in order to illustrate the beam quality that can result from such a gridded structure. These simulations have been found to reproduce the beam current behaviors versus of applied potentials that are observed experimentally. Based on it ASTRA RF beam simulations also predict a complicated time-dependent response to the waveform applied to the grid during the current turn-on, calculation of the dissipated power by electrons at the grid, and particle tracking downstream of the grid into RF gun cavity and farther on. These simulations may be representative in other sources, such as some L-band RF injectors for industrial applications.
TRIUMF, Vancouver
DAE/VECC, Calcutta
TRIUMF (Canada) and VECC (India) are planning to each build a 1.3GHz 50MeV/500kW superconducting electron linac as a driver for producing radioactive ion beams through photo-fission. The two institutes have launched a collaboration with the initial goal to design, build and test a 5-10MeV superconducting injector cryomodule capable of accelerating up to 10mA. A testing area is being set-up at TRIUMF to house the electron gun, rf buncher, injector cryomodule, diagnostic station and beam-dump for beam studies. The project will test all critical elements of the final linac; beam halo generation, HOM excitation, LLRF and rf beam loading and cavity and cryomodule design/performance. The scope and status of the project will be described.
TUB, Beijing
BNL, Upton, Long Island, New York
Funding: Supported by National Natural Science Foundation of China (No.10735050, No.10875070) and National Basic Research Program of China (973 Program)(No.2007CB815102)
Time-resolved MeV ultra-fast electron diffraction (UED) is a promising tool for studying of structural dynamics on the fundamental temporal and spatial scales of atomic motion. To reach the desired temporal and spatial resolutions, precise control and measurement of ultra-short, low emittance electron pulses are required. A MeV UED system based on an S-band photocathode RF gun is built and optimized at Tsinghua University. We present the experiment results here.
UCLA, Los Angeles, California
Funding: Office of Naval Research (US) Grant No. N000140711174
Longitudinal beam dynamics of the photoinjector "blowout" regime are investigated. A two beamlet macroparticle approach is first used to investigate the effects of S-Band RF photogun fields on a picosecond time scale. The beams' longitudinal phase spaces (LPS) are measured via an X-band RF deflecting cavity and dipole spectrometer. Lastly, the LPS of a single subpicosecond beam is investigated as a function of initial charge density at the cathode and compared to simulation.
RISE, Tokyo
KEK, Ibaraki
ISIR, Osaka
AIST, Tsukuba, Ibaraki
At Waseda University, we have been developing a high quality electron source based on photo-cathode rf-gun and its application experiments. To produce a high current electron beam, we installed a Cs-Te cathode which has higher quantum efficiency and improved the structure of the rf cavity. By adopting a Cs-Te cathode, it is expected that the production of the higher charged single bunch electron beam with a low emittance can be achieved. Moreover, the generation of high quality multi-bunch electron beam is also expected to be possible due to the high quantum efficiency of Cs-Te. For understanding of a Cs-Te cathode and higher quantum efficiency operation, we have performed the fundamental studies by single bunch beam. On the other hand, we have also developed a multi-pulse UV laser for generating the multi-bunch electron beam. Our laser system is composed by all-solid-state Nd:YLF for the stable operation, and the specification of this laser is expected to generate a 100bunch/train with the bunch charge of 800pC/bunch. In this conference, the experimental results of Cs-Te and new laser system and the recent progress of multi-bunch electron beam generation will be reported.
Xavier University of Louisiana, New Orleans, Louisiana
UW-Madison/SRC, Madison, Wisconsin
For many years it has been speculated that uniformly filled ellipsoidal electron bunches, with their linear fields, would be ideal to produce high charge density with low emittance beams. This may be particularly advantageous with bunch compression schemes required for operation of an FEL. The “blow-out” mode is a method of producing the desired electron bunch distribution: an initial charge pancake is produced at the cathode and allowed to expand to an ellipsoidal shape under the influence of its own space charge. In earlier studies a constant, DC electric field has been assumed in the production of ellipsoidal bunch distributions using “blow-out” mode. In this paper we look at the effects of a time varying, non-constant electric field on the development of the electron bunches as they are emitted from the photocathode and travel through an accelerating RF cavity. We present the effects of frequency in the cavity, field strength of the cavity,, as well as the phase of the electron bunch. These three variables change the spatial curvature and the temporal slope of the electric field as observed by the electron bunch. This results in changes in bunch development and formation.
LBNL, Berkeley, California
Funding: This work was supported by the Office of Science, U. S. Department of Energy, under Contract No. DE-AC02-05CH11231.
There is considerable interest in the use of muon beams to create either an intense source of decay neutrinos aimed at a detector located 3000-7500 km away (a Neutrino Factory), or a Muon Collider that produces high-luminosity collisions at the energy frontier. R&D aimed at producing these facilities has been under way for more than 10 years. This paper will review experimental results from MuCool, MERIT, and MICE and indicate the extent to which they will provide proof-of-principle demonstrations of the key technologies required for a Neutrino Factory or Muon Collider. Progress in constructing components for the MICE experiment will be described.
BNL, Upton, Long Island, New York
In the past few years, there have been a number of advances in the design and supporting R&D for a machine to cool, accelerate and collide TeV muon beams. This talk will review progress and discuss how such a machine might evolve from programs to build high intensity proton sources and neutrino factories.
BNL, Upton, Long Island, New York
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Funding: Work Supported by the United States Department of Energy, Contract No. DE-AC02-98CH10886.
The International Design Study for the Neutrino Factory (IDS-NF) aims to produce a design report for a neutrino factory. One component of that design is a linear non-scaling fixed-field alternating gradient accelerator (FFAG) that will accelerate to the final energy of 25~GeV. An FFAG is used to reduce the machine cost by maximizing the number of passes made through the RF cavities. We present some design options for this FFAG, individually optimized for cost. We study the addition of nonlinear magnets to the lattice to improve the performance of the lattice and consider the negative effects of doing so.
Fermilab, Batavia
Muons, Inc, Batavia
We have developed a new method for capture, bunching and phase-energy rotation of secondary beams from a proton source, using high-frequency rf systems. The method is the baseline for muon capture in the International scoping study for a neutrino factory. In this method, a proton bunch on a target creates secondaries that drift into a capture transport channel. A sequence of rf cavities forms the resulting muon beams into strings of bunches of differing energies, aligns the bunches to (nearly) equal central energies, and initiates ionization cooling. For the International Design Study the method must be optimized for performance and cost, and variations will be explored. In this paper we present results of optimization and variation studies toward obtaining the maximum number of muons for a neutrino factory, as well as for a future muon collider.
CEA, Gif-sur-Yvette
With the aim of producing an intense flux of 14 MeV neutrons, the International Fusion Materials Irradiation Facility (IFMIF) relies on two high power CW accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV to a common lithium target. The Engineering Validation and Engineering Design Activities (EVEDA) phase of IFMIF, which has been launched in the middle of 2007, has two major objectives: to produce the detailed design of the entire IFMIF facility and to build and test the key systems, in particular the prototype of a high-intensity CW deuteron accelerator (125 mA @ 9 MeV). The design of the IFMIF accelerator, as well as the design of the prototype to be installed in Rokkasho (Japan) are presented.
IPN, Orsay
INFN/LASA, Segrate (MI)
SCK-CEN, Mol
CEA, Gif-sur-Yvette
IAP, Frankfurt am Main
An Accelerator Driven System (ADS) for transmutation of nuclear waste typically requires a 600 MeV - 1 GeV accelerator delivering a proton flux of a few mA for demonstrators, and a few tens of mA for large industrial systems. Such a machine belongs to the category of the high-power proton accelerators, with an additional requirement for exceptional "reliability": because of the induced thermal stress to the subcritical core, the number of unwanted "beam-trips" should not exceed a few per year, a specification that is far above usual performance. This paper describes the reference solution adopted for such a machine, based on a so-called "fault-tolerant" linear superconducting accelerator, and presents the status of the associated R&D. This work is performed within the 6th Framework Program EC project "EUROTRANS".
CLASSE, Ithaca, New York
Cornell University, Ithaca, New York
JLAB, Newport News, Virginia
Cornell University has built a high average current electron injector for use with an Energy Recovery Linac. The injector is capable of up to 100 mA average current at 5 MeV (33 mA at 15 MeV) and is expected to produce the ultra low emittances needed for an ERL. This talk will give an overview of the initial performance of this injector and summarize a spectrum of beam physics experiments undertaken to demonstrate low emittance, high average current operation.
Cornell University, Ithaca, New York
CLASSE, Ithaca, New York
Funding: This work is supported by the National Science Foundation.
Cornell University has developed and fabricated a SRF injector cryomodule for the acceleration of the high current (100 mA) beam in the Cornell ERL injector prototype. The injector cryomodule is based on superconducting rf technology with five 2-cell rf cavities operated in cw mode. To support the acceleration of a low energy, ultra low emittance, high current beam, the beam tubes on one side of the cavities have been enlarged to propagate Higher-Order-Mode power from the cavities to broadband rf absorbers located at 80 K between the cavities. The axial symmetry of these absorbers, together with two symmetrically placed input couplers per cavity, avoids transverse on-axis fields, which would cause emittance growth. Each cavity is surrounded by a LHe vessel and equipped with a frequency tuner including fast piezo-driven fine tuners for fast frequency control. The cryomodule provides the support and precise alignment for the cavity string, the 80 K cooling of the ferrite loads, and the 2 K LHe cryogenic system for the high cw heat load of the cavities. In this paper results of the commissioning phase of this injector cryomodule will be reported.
ANL, Argonne
Several high power proton and ion linac projects based on superconducting accelerating technology are currently under study and drive an important worldwide R&D effort on superconducting cavities, especially for low and medium energy linacs. Multi-cell elliptical cavities, single or multi-spoke cavities, half-wave and quarter-wave superconducting cavities have been developed at many laboratories and institutions and continue to extend the state-of-the-art for this class of cavities. This talk reviews recent developments and results for SC cavity performance along with a brief overview of associated components such as mechanical slow tuning systems, fast tuners and rf power couplers.
JLAB, Newport News, Virginia
A major portion of the ILC R&D effort is focused on increasing the sustainable gradients in the baseline TESLA-shape SC cavities. This is a world-wide effort with major contributions from DESY (in parallel with their XFEL program), JLAB, FNAL and KEK. During the past year, the work in the US and Japan has ramped up considerably, and PAC09 is an opportune time to review the contributions from the groups in these regions, as well as at DESY.
KEK, Ibaraki
A 6-m cryomodule, which includes four Tesla-like 9-cell cavities, was assembled and installed in the STF tunnel in April, 2008. After cooldown of the cryomodule, high power tests of four cavities had been carried out at 2 K from September to December, 2008. A cavity package consists of a 9-cell niobium cavity with two HOM couplers, an input coupler with a cold and a warm rf window, and a frequency tuning system with a mechancal and a piezo tuner. The performance as a total sc cavity system was checked in the cryomodule test with high rf power. One of the cavities was achieved a stable pulsed operation at 32 MV/m higher than the specific operating gradient (31.5 MV/m) in ILC. The maximum accelerating gradients (Eacc,max) obtained in the vertical cw tests was maintained or slightly improved in the cryomodule tests with a pulsed operation of 1.5 msec and 5 Hz. Compensation of Lorentz force detuning at 31 MV/m was successfully demonstrated by using piezo tuner and pre-detuning.
Fermilab, Batavia
Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Ionization cooling is essential for realization of Muon Collider, muons beam based neutrino factories and other experiments involving muons. The simplest structure - absorber(s) immersed in alternating solenoidal magnetic field - provides only transverse cooling since the longitudinal motion in the most suitable momentum range (2-300MeV/c) is naturally antidamped. To overcome this difficulty it is proposed to periodically tilt solenoids so that a rotating transverse magnetic field was created. By choosing the phase advance per period above a multiple of 2pi it is possible to ensure that muons with higher momentum make a longer path in the absorber (whether distributed or localized) thus providing longitudinal damping. Basic theory of such channel and results of tracking simulations are presented.
SLAC, Menlo Park, California
Funding: Work supported by US DOE contract DE-AC02-76SF00515.
Single-pass free electron lasers require high peak currents from ultra-short electron bunches to reach saturation and an accurate measurement of bunch length and longitudinal bunch profile is necessary to control the bunch compression process from low to high beam energy. The various state-of-the-art diagnostics methods from ps to fs time scales using coherent radiation detection and RF deflection techniques are presented.
SLAC, Menlo Park, California
ANL, Argonne
Funding: Work supported by U.S. Department of Energy under Contract Nos. DE-AC02-06CH11357 and DE-AC02-76SF00515.
We present the performance of the cavity beam position monitor (BPM) system for the LCLS undulator. The construction and installation phase of 34 BPMs for the undulator and 2 for the transport line have been completed. The X-band cavity BPM employs a TM010 monopole reference cavity and a TM110 dipole cavity designed to operate at a center frequency of 11.384 GHz. The signal processing electronics features a low-noise single-stage three-channel heterodyne receiver that has selectable gain and a phase locking local oscillator. The approximately 40 MHz IF is digitized by a 120M sample/second four-channel 16-bit digitizer. System requirements include sub-micron position resolution for a single-bunch beam charge of 200 pC. We discuss the system specifications and commissioning results.
SLAC, Menlo Park, California
SAIC, Billerica, Massachusetts
Funding: Work supported by Department of Energy contract DE-AC02-76SF00515
SLAC is developing a 10 MW, 5 Hz, 1.6 ms, L-band (1.3 GHz) Sheet-Beam Klystron as a less expensive and more compact alternative to the ILC baseline Multiple-Beam Klystron. The Klystron is intended as a plug-compatible device of the same beam current and operating voltage as existing Multiple-Beam Klystrons. At this time, a beam tester has been constructed and currently is in test. The beam tester includes an intercepting cup for making beam quality measurements of the 130 A, 40-to-1 aspect ratio beam. Measurements will be made of the electrostatic beam and of the beam after transporting through a drift tube and magnetic focusing system. General theory of operation, design trade-offs, and manufacturing considerations of both the beam tester and klystron will be discussed.
Beam-Wave Research, Inc., Union City
SAIC, McLean
NRL, Washington, DC
STAAR/AWR Corporation, Mequon
Funding: Research funded by the Office of Naval Research and Naval Research Laboratory.
The accelerator community is making the transition to IOT technology for a number of high-power UHF and L-band applications as a result their inherent benefits. Scientists, funded by the Office of Naval Research and Naval Research Laboratory, are investigating the physics of the beam-wave interaction of the IOT. The time-domain electrostatic PIC code MICHELLE, in conjunction with the Analyst® suite of electromagnetic codes, were used to model the cathode-grid-anode structure that comprise the input cavity. Our investigation has led to the discovery of a delay mechanism responsible for intra-bunch charge formation, as evidenced by IOT X-ray generation with energies significantly higher than the cathode accelerating potential, increasing with RF output power. Time-domain PIC results of this effect will be shown. We will also present simulation results of the large-signal beam wave interaction in the output cavity using the code TESLA. Examples of single beam and multiple-beam IOTs will also be shown.
KEK, Ibaraki
KEK/JAEA, Ibaraki-Ken
J-PARC is a unique accelerator, because magnetic alloy (MA) loaded cavities are employed for the first time in the rf systems of high intensity proton synchrotrons. High field gradients of more than 20 kV/m are achieved covering the frequency range from 0.9 MHz to 3.4 MHz. The peak voltage of 45 kV per cavity is obtained by driving with two 600 kW tetrodes in push-pull. The first high intensity beam acceleration was successfully initiated at J-PARC RCS. Although RCS beam commissioning started with 10 rf systems, instead of 11 as designed, RCS succeeded in the acceleration of an intense proton beam, which is equivalent to 300 kW when operated at 25 Hz. The longitudinal painting based on the simulation with superimposed second harmonics and with phase and momentum manipulations was the key of success. In December 2008, the J-PARC MR beam is scheduled for its first acceleration up to 30 GeV, and the Material and Life Science facilities start the user operations. During the development stage of the MA cavities, some serious problems such as electrical breakdown on core surfaces occurred. The problems were solved in a short term, and all rf systems were completed on schedule.
Fermilab, Batavia
Rutgers University, The State University of New Jersey, Piscataway, New Jersey
Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The promise of next-generation light sources depends on the availability of ultra-low emittance electron sources. One method of producing low transverse emittance beams is to generate a low longitudinal emittance beam and exchange it with a large transverse emittance. Experiments are underway at Fermilab's A0 Photoinjector and ANL's Argonne Wakefield Accelerator using the exchange scheme of Kim and Sessler. Experiments as the A0 photoinjector exchange a large longitudinal emittance with a small trasverse emittance. AWA expects to exchange a large transvserse emittance with a small logitudinal emittance. In this paper we discuss recent results at A0 and AWA and future plans for these experiments.
IHEP Beijing, Beijing
KEK, Ibaraki
TIPC, BeiJing
Funding: Supported by National Natural Science Foundation of China (10525525)
1.3 GHz single cell large grain (LG) cavities have been studied in our research programs on the superconducting cavity for the International Linear Collider (ILC) in the last three years and five LG cavities were fabricated at IHEP and KEK. Three cavities were dealt with by surface treatments based on electro polishing (EP) and the maximum gradient of 47.90 MV/m was achieved. The other two cavities were treated based on chemical polishing (CP) and both reached the accelerating gradients higher than 35 MV/m with the maximum gradient of 40.27 MV/m. In this paper, the performance comparison of the large grain cavities will be presented and discussed.
TRIUMF, Vancouver
PAVAC, Richmond, B.C.
The ISAC-II heavy ion linear accelerator has been in operation at TRIUMF since 2006. The high beta section of the accelerator, consisting of twenty cavities with optimum beta=0.11, is currently under production and is scheduled for completion in 2009. The cavities are superconducting bulk Niobium two-gap quarter-wave resonators with a frequency of 141 MHz, providing, as a design goal, a voltage gain of Veff=1.08 MV at 7 W power dissipation. Production of the cavities is with a Canadian company, PAVAC Industries of Richmond, B.C. after two prototype cavities were developed, produced and successfully tested. Cavity production details and test results will be presented and discussed.
ANL, Argonne
IIT, Chicago, Illinois
Tech-X, Boulder, Colorado
Funding: DOE. OHEP
We are modeling breakdown arcs in rf structures with Particle in Cell, (OOPIC Pro and VORPAL), Molecular Dynamics (HyDyn, LAMMPS), and an integrated radiation-magnetohyrodynamic package (HEIGHTS) to evaluate the basic parameters and mechanisms of rf discharges. We are evaluating the size, density, species temperature, radiation levels and other properties, to determine how the breakdown trigger works, what the growth times of the discharge are, effects of strong magnetic fields and what happens to both the arc and cavity energy. The goal is to have a complete picture of the plasma and its interaction with the wall. While we expect that these calculations will help guide further experimental studies, we have recently benchmarked model predictions against available experimental data on rise times of x ray pulses, and found a reasonable agreement.
ANL, Argonne
CEA, Gif-sur-Yvette
JLAB, Newport News, Virginia
Fermilab, Batavia
NHMFL, Tallahassee, Florida
IIT, Chicago, Illinois
Funding: DOE/OHEP
We have begun using Atomic Layer Deposition (ALD) to synthesize a variety of surface coatings on coupons and cavities as part of an effort to produce rf structures with significantly better performance and yield than those obtained from bulk niobium, The ALD process offers the possibility of conformally coating complex cavity shapes with precise layered structures with tightly constrained morphology and chemical properties. Our program looks both at the metallurgy and superconducting properties of these coatings, and also their performance in working structures. Initial results include: 1) evidence from point contact tunneling showing magnetic oxides can be a significant limitation to high gradient operation, 2) experimental results showing the production sharp niobium/oxide interfaces from a high temperature bake of ALD coated Al2O3 on niobium surfaces, 3) results from ALD coated structures.
BNL, Upton, Long Island, New York
Funding: This work supported by the U.S. Department of Energy, contract no. DE-AC02-98CH10886.
Beam cooling for a future neutrino factory or muon collider requires high gradient rf cavities in the presence of strong magnetic fields. Experimental measurements suggested that the maximum accelerating gradient drops as the axial magnetic field increases. Little is known about the explicit dependence of the gradient on the strength of the magnetic field. The experimental observation of dark currents arising from local regions with enhanced surface field intensities under external magnetic fields however, suggests a new possible mechanism of breakdown based on electron field emission. A model of magnetic field breakdown is proposed. We illustrate that the field emitted electrons are focused by the external fields into small spots on the other side of the cavity and estimate the energy density they deliver to the wall. We show that this energy increases with the magnetic field, and this may lead to melting of the cavity surface. The influence of local fields at the emitter side is discussed and the extent to which space-charge affects this process is investigated. Results of our model are compared with recent experimental data from the 201 MHz and 805 MHz cavities.
IHEP Beijing, Beijing
In the conventional 324 MHz DTL designed for China Spallation Neutron Source (CSNS) accelerating H- ion from 3MeV to 132MeV, there are 7 tanks and currently the R&D of tank-1 is under proceeding, which has 29 cells and 29 quadrupoles. In design, the Tank-1 has a tilt field distributed partially in order to obtain most effective energy gain and low Kilpatric parameter. In order to decrease the difficulty of tuning the partial tilt field distribution, a new analysis named transfer matrix method is introduced. Verifying of the calculation and simulation of the transfer matrix has been finished with MDTFISH code, picking parameters from CSNS and SNS. Checking the method on the model tank in CSNS will be operated.
Cockcroft Institute, Lancaster University, Lancaster
SLAC, Menlo Park, California
UMAN, Manchester
Funding: The work is supported by STFC
A crab cavity is required in the CLIC to allow effective head-on collision of bunches at the IP. A high operating frequency (X-band) for the crab cavity is preferred as the deflection voltage required and the RF phase tolerance are inversely proportional to the operating frequency. However, the strong inter-bunch wakefields deteriorate the quality of the colliding bunches. The short bunch spacing of the CLIC scheme and the crab cavity's high sensitivity to dipole kicks demands very high damping of the inter-bunch wakes. A crab cavity requires special attention to the damper design as its wakefield spectrum is entirely different from that of an accelerating cavity. In addition to the higher-order modes, the orthogonally polarised dipole mode (same order mode) and the fundamental monopole mode (lower order mode) also need to be damped, however their resonant frequencies make damping these modes complicated. The same order mode suppression requires the use of an azimuthally asymmetric damper. This paper investigates the nature of the wakefields in the CLIC crab cavity and the possibility of using choke-mode damping and various types of waveguide damping to suppress them effectively.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
The Dampy cavity, operating at 500 MHz and up to 160 kW, normal conducting HOM damped, will be used in the ALBA storage ring. The pre-series has shown two problems. First, the HOM damping is very efficient but for one mode. The longitudinal impedance of the E011 mode was found to be around 11 kΩ, slightly above ALBA stability threshold. Second, overheating close to the dampers flanges induces a vacuum leak after several thermal cyclings. The maximum achieved operational dissipated power is 40 kW, if power is further increased a leak opens at one of the dampers flanges. In order to alleviate this latter drawback, two modifications have been implemented in two different cavities. The pre-series has been provided with short-circuits bridging waveguide ridges and cavity body. These are supposed to decrease the current in the area of the flanges. The first production cavity features a reduced thermal impedance between the water cooling channels and the area of overheating by replacing stainless steel by copper in the critical area. Both these cavities are currently under test and this paper will show the results.
Euclid TechLabs, LLC, Solon, Ohio
KEK, Ibaraki
Ceramics Ltd., St. Petersburg
Fermilab, Batavia
Funding: This work was supported by the US Department of Energy
Euclid TechLabs LLC is developing BST based ferroelectric elements designed to be used as the basis for new advanced accelerator components operating in the 1.3 GHz frequency range and intended for Project X and ILC applications. These new ferroelectric elements are designed for the fast active tuner for SC cavities that can operate in air at low biasing DC fields in the range of 15 kV/cm. The BST(M) material (BST ferroelectric with Mg-based additives) allows fast switching and tuning in vacuum and in air both; switching time of material samples < 10 ns has been demonstrated. The overall goal of the program was to design an L-band externally-controlled fast ferroelectric tuner for controlling the coupling of superconducting RF cavities for the future linear colliders. The tuner prototype has been built; a time response of <30 ns, or 1 deg. in 0.5 ns has been reached. . The following problems are addressed: (i) lowering the losses in the ferroelectric material; (ii) improving the technique of the ferroelectric element metallization and brazing; and (iii) improvement breakdown threshold at high voltage bias.
CERN, Geneva
aurorasat, Paterna
DCOM-iTEAM-UPV, Valencia
WBFB, Berlin
Universidad Politecnica de Madrid, ETSI Aeronauticos, Madrid
UAM, Madrid
UVEG, Burjasot (Valencia)
ESA-ESTEC, Noordwijk
CSIC, Madrid
Multipactor phenomena which are closely linked to the SEY (secondary electron yield) can be mitigated by many different methods including groves in the metal surface as well as using electric or magnetic bias fields. However frequently the application of global magnetic or electric bias field is not practicable considering the weight and power limitations on-board satellites. Additionally, surface grooves may degrade the RF performance. Here we present a novel technique which is based on a magnetostatic field pattern on the metallic surface with fast spatial modulation in the order of 30 micron. This field pattern is produced by proper magnetization of an underlying ferromagnetic layer such as nickel. Simulations and preliminary experimental results will be shown and a number of applications, both for particle accelerators and satellite microwave payloads are discussed.
CERN, Geneva
The understanding of electrical breakdowns has a critical role in the design of the RF accelerating cavities for the CLIC linear collider. In this context a new statistical model of the conditioning process and breakdown rate evolution is presented for a DC spark system with tip-plane electrode geometry charged from a capacitance. The approach requires a small amount of assumptions, but can still make several interesting predictions. Electrode gap distance dependence on the saturated breakdown field and spitfest (grouped breakdowns) are among the phenomena that could be explained from this simple model.
CERN, Geneva
Electrical breakdown in the accelerating cavities set a potential limit to the performance of the CLIC linear collider. Vacuum degradation and beam instability are possible outcomes from a breakdown if too much gas is released from the cavity surface. Quantitative data of gas release are provided for copper electrodes (milled Cu-OFE, as-received and heat-treated), and molybdenum electrodes. These data are produced from a controlled DC spark environment with capacitance charged anode at fixed energy.
Far-Tech, Inc., San Diego, California
We describe a novel acceleration structure for acceleration of electron and ion beams where the cell-to-cell coupling is provided by slot resonances in the wall of adjacent accelerator cells. As with the side-coupled linac, the concept allows for the operation of a standing-wave structure in a phase and amplitude stabilized pi/2 mode. We explore the applications of such a structure to electron and ion accelerators.
Far-Tech, Inc., San Diego, California
The fixed-field alternate gradient (FFAG) synchrotron offers an attractive solution for systems that require rapid acceleration over a wide range of energies. The ability to rapidly tune the frequency of the accelerating cavity in the “non-scaling” variety of an FFAG synchrotron represents a fundamental barrier to their implementation in a wide variety of applications for proton, ion and muon acceleration. Initial results of the rapidly tunable cavity design for specific application to proton and light ion medical FFAG accelerators are presented.
Fermilab, Batavia
Muons, Inc, Batavia
Funding: Supported in part by FRA DOE contract number DE-AC02-07CH11359
RF cavities below 800 MHz are large, so alternative cavities at low frequencies are needed. Novel dielectric loaded RF cavities will allow smaller diameter cavities to be designed; changing the frequency of a cavity design would be as simple as changing the dielectric cylinder insert material or inner radius of the dielectric in the cavity. This paper discusses RF cavities loaded with dielectric material that could be used in various ways for muon facilities. The examples given are for 400 and 800 MHz cavities. Our initial motivation was to use dielectric to reduce the radial size of gas-filled cavities in helical cooling channels, but dielectric-loading has potential use in vacuum cavities for suppression of dark current emission. We also studied cavities that can be used for the phase rotation channel in the front end of a muon collider or neutrino factory.
Muons, Inc, Batavia
Fermilab, Batavia
Funding: Supported by STTR Grant DE-FG02-07ER86320 and FRA DOE contract number DE-AC02-07CH11359
Originally conceived as a solution for FFAG applications, a new compact RF cavity design that tunes rapidly over various frequency ranges can be used to upgrade existing machines. The design being developed uses orthogonally biased garnet cores for fast frequency tuning and liquid dielectric to adjust the frequency range and to control the core temperature. We describe measurements of candidate ferrite and dielectric materials. The first use of the new cavity concept will be for improvements to the 8 GeV Fermilab Booster synchrotron.
Fermilab, Batavia
Muons, Inc, Batavia
Voss Scientific, Albuquerque, New Mexico
Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86350 and and FRA DOE contract number DE-AC02-07CH11359
RF cavities pressurized with hydrogen gas may provide effective muon beam ionization cooling needed for muon colliders. Recent 805 MHz test cell studies reported below include the first use of SF6 dopant to reduce the effects of the electrons that will be produced by the ionization cooling process in hydrogen or helium. Measurements of maximum gradient in the Paschen region are compared to a simulation model for a 0.01% SF6 doping of hydrogen. The observed good agreement of the model with the measurements is a prerequisite to the investigation of other dopants.
Fermilab, Batavia
Muons, Inc, Batavia
CERN, Geneva
Funding: supported in part by USDOE STTR Grant DE-FG02-08ER86350
The great advantage of the helical ionization cooling channel (HCC) is its compact structure that enables the fast cooling of muon beam 6-dimensional phase space. This compact aspect requires a high average RF gradient, with few places that do not have cavities. Also, the muon beam is diffuse and requires an RF system with large transverse and longitudinal acceptance. A traveling wave system can address these requirements. First, the number of RF power coupling ports can be significantly reduced compared with our previous pillbox concept. Secondly, by adding a nose on the cell iris, the presence of thin metal foils traversed by the muons can possibly be avoided. We show simulations of the cooling performance of a traveling wave RF system in a HCC, including cavity geometries with inter-cell RF power couplers needed for power propagation.
FZJ, Jülich
CERN, Geneva
The COoler SYnchrotron COSY at the Forschungszentrum Jülich is operating now since 1992. Up to 5*1010 protons can be delivered over a momentum range of 600 MeV/c to 3.6 GeV/c. The prototype of the HESR barrier bucket cavity was installed into COSY and many measurements have been performed. Especially the co-operation of barrier bucket with stochastic cooling has been studied. During the measurements the internal WASA Pellet target was available which is similar to the PANDA target at the HESR. A 1.2m long cryo-tank has been designed and installed to measure the sensitivities of new pickup structures for the HESR stochastic cooling system. Tank design and structures arrangement correspond to the projected HESR stochastic cooling layout. The recent results will be presented.
GSI, Darmstadt
To feed the production targets of FAIR with very short bunches (pulse durations of not more than 50 ns are envisaged) demanding rf-systems for bunch compression are required in SIS18 and SIS100. But also the opposite process, namely debunching, is required in the collector ring CR. Bunch compression as well as debunching will be done by fast bunch rotation. Due to space restrictions both rf-systems must be able to generate a very high field gradient of 50 kV/m at very low frequencies. Such high field gradients can be realised only using magnetic alloy (MA) cavities, since their saturation field strength is about ten times higher compared to NiZn-ferrites. For SIS18 a MA bunch compressor unit, which generates the required 50 kV/m at 800- and 1200 kHz, has already been realized as a forerunner for the required FAIR-systems.
GSI, Darmstadt
The 'Facility of Antiproton and Ion Research' (FAIR) project will be realized at the 'GSI Helmholtzzentrum für Schwerionenforschung GmbH' (Darmstadt, Germany) in the scope of a large international collaboration. One of the FAIR storage rings is the collector ring (CR) whose main purpose is to allow a fast cooling of secondary beams (rare isotopes and antiprotons). The RF system of the collector ring has to allow pulsed operation (40kV, duty cycle 5e-4) as well as continuous operation (2kV) in the frequency range of 1.2 to 1.4MHz. The detailed conceptual design of this RF system is introduced here. It will be based (similar to the existing RF system 'SIS18 bunch compressor' which will also be presented at PAC09) on two inductively loaded quarter wavelength coaxial resonators operating on a common ceramic gap. The resonator will be loaded with twelve ring cores (rout=313mm, rin=145mm, h=25mm) of a cobalt based amorphous magnetic alloy (VitroVac6030F); it will be cooled by forced air. The cavity will be driven by a push-pull amplifier operated in class A consisting of two tetrodes (TH555A) that will be coupled inductively to the cavity.
KEK, Ibaraki
CEA, Gif-sur-Yvette
LPSC, Grenoble
This paper presents the RF systems of RACCAM FFAG for medical applications. Design of the RF system was updated to fit short and curved straight section of the spiral FFAG in view of preserving the compactness of the spiral lattice.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
GUAS, Kanagawa
J-PARC RCS accelerates a high intensity beam using 11 sets of Magnetic Alloy loaded cavities. It supplies the proton beam to the MLF (Material Life Science Facility) for the neutron and muon experiments. For very high resolution muon experiments, a short proton beam bunch of few ten ns is necessary. To reduce the bunch width to several ten ns, a bunch rotation scheme before extraction will be useful. For the bunch width of few ten ns, a much higher RF voltage is also required. Based on a new magnetic alloy core technology, a design of a new RF cavity to increase the maximum RF voltage by a factor of two will be described in this paper.
KEK, Ibaraki
High-gradient RF breakdown studies have been in progress at Nextef (New X-band Test Facility at KEK) since 2006. To study the characteristics of different materials on high-field RF breakdown, we have performed high-gradient experiments by using narrow waveguides that has a field of around 140 MV/m at 50 MW power. Breakdown rates of stainless-steel and copper cases were measured and the results are described in this paper.
HUST, Wuhan
Funding: Nation Nature Science Foundation of China,10435030
At Huazhong University of Science and Technology (HUST), the design study of a 10 MeV compact cyclotron CYCHU-10 for the application of Positron Emission Tomography (PET) has been developed since 2007. This paper describes the recent status of RF cavities including numerical calculation results of basic parameters, the capacitive trimmer to overcome frequency shift when in operation and the construction and cold test of the 1:1 scale prototype. The inductive coupling loop design and matching simulation with the RF power generator are also presented
HUST, Wuhan
Funding: Work supported by National Nature Science Foundation of China, 10435030
In order to reduce the cost of the signal generator comprising a high performance direct digital synthesizer (DDS), the method of picking up a desired aliased signal of DDS output is adopted in the study. The chip AD9850 is used to synthesize RF signal in the system, and the amplitude modulation of the system is achieved by altering the external connection resistance of the chip. The output frequency is tunable from 99.5 to 101MHz. The principle and the test results of the signal synthesizer will be presented. The amplifier based on tetrode technology can deliver the 10kW RF power in a continuous wave (CW) mode of operation. The driver amplifier consists of two solid-state modules, and it can provide the tetrode with up to 300W input power. The tetrode operates in the grounded cathode configuration. The conceptual design of the final stage amplifier will also be demonstrated in this paper.
IIT, Chicago, Illinois
Fermilab, Batavia
LBNL, Berkeley, California
ANL, Argonne
Funding: The United States Department of Energy
The accelerating gradient in a RF cavity is limited by many factors such as the surface material properties, RF frequency, the external magnetic field and the gas pressure inside the cavity. In the MuCool Program, RF cavities are studied with the aim of understanding these basic mechanisms and improving their maximum stable accelerating gradient. These cavities are being developed for muon ionization cooling channel for a Neutrino Factory or Muon Collider. We report studies using the 805 MHz and 201 MHz RF cavities in the MuCool Test Area (MTA) at Fermilab. New results include data from buttons of different materials mounted in the 805 MHz cavity, study of the accelerating gradient in the 201 MHz cavity and X-ray background radiation from the cavities due to Bremsstrahlung. The 201 MHz cavity has been shown to be stable at 19 MV/m at zero magnetic field, well in excess of its 16 MV/m design gradient. We will also discuss results from the 201 MHz cavity study in magnetic field and introduce the test of E × B effects with the 805 MHz box cavity.
BNL, Upton, Long Island, New York
This paper will present the preliminary results of the testing of the 703 MHz SRF cryomodule designed for use in the ampere class ERL under construction at Brookhaven National Laboratory. The preliminary VTA cavity testing, carried out at Jefferson Laboratory, demonstrated cavity performance of 20 MV/m with a Qo of 1x1010, results we expect to reproduce in the horizontal configuration. This test of the entire string assembly will allow us to evaluate all of the additional cryomodule components not previously tested in the VTA and will prepare us for our next milestone test which will be delivery of electrons from our injector through the cryomodule to the beam dump. This will also be the first demonstration of an accelerating cavity designed for use in an ampere class ERL, a key development which holds great promise for future machines.
Fermilab, Batavia
CERN, Geneva
BNL, Upton, Long Island, New York
Funding: This work has been partially performed under the auspices of the US department of energy
The complex LHC crab cavity design and the beam-line configuration pose very tight constraints for the cryostat design. An initial assessment of the LHC main RF cryostat points to a new design both from the RF and engineering point of view. The cavity and tunnel constraints are discussed in detail and an intial cryostat design along with the cryogenic circuit is presented.
BNL, Upton, Long Island, New York
Omega-P, Inc., New Haven, Connecticut
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A novel tuner has been developed by the Omega-P company to achieve fast control of the accelerator RF cavity frequency. The tuner is based on the ferroelectric property which has a variable dielectric constant as function of applied voltage. Tests using a Brookhaven National Laboratory (BNL) 1.3 GHz RF cavity have been carried out for a proof-of-principle experiment of the ferroelectric tuner. Two different methods were used to determine the frequency change achieved with the ferroelectric tuner. The first method is based on a S11 measurement at the tuner port to find the reactive impedance change when the voltage is applied. The reactive impedance change then is used to estimate the cavity frequency shift. The second method is a direct S21 measurement of the frequency shift in the cavity with the tuner connected. The estimated frequency change from the reactive impedance measurement due to 5 kV is in the range between 3.2 kHz and 14 kHz, while 9 kHz is the result from the direct measurement. The two methods are in reasonable agreement. The detail description of the experiment and the analysis will be discussed in the paper.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A 56 MHz Superconducting RF cavity is developed for the luminosity enhancement of the Relativistic Heavy Ion Collider (RHIC). The 56 MHz SRF cavity enables to adiabatically rebucket the beam from the 28 MHz accelerating cavities, which with shorter bunch lengths will enhance the luminosity significantly. The 56 MHz SRF cavity fundamental mode must be damped during injection and acceleration by a fundamental mode damper (FD), which is physically withdrawn at store for operation. The cavity frequency changes from the withdrawing motion but is kept below the beam frequency at store by a judicious axial placement of the FD. Physics studies by numerical simulations, tests of the FD in the prototype cavity, and the challenging engineering issues are here addressed. In addition, higher-order mode (HOM) dampers are necessary for the stable operation of the 56 MHz SRF cavity. The HOM’s are identified and the external Q factors are obtained from tests of the prototype cavity and are compared to simulations with the CST MWS program. The HOM damper blocks the fundamental mode by a 5 element high pass filter. The HOM stability criteria of the cavity are satisfied with four HOM dampers.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A beam excited 56 MHz RF Niobium Quarter Wave Resonator has been proposed to enhance RHIC beam luminosity and bunching. As multipacting is expected, an extensive study was carried out with the Multipac 2.1 code, looking for a way to suppress it. Multipacting bands were found. Discharge occurred at cavity’s top corner above beam gap and on outer conductor up to more than half its length, moving towards the end of the cavity. We find single-point multipacting, with emission from the outer conductor, as well as two-point multipacting involving both inner and outer conductor. We found a geometric approach to suppressing multipacting. The most promising method was ripples in outer conductor. Ripples’ depth, width and gap were optimized. In shallow depth of 1 cm, electrons multiply, drift further, however they are stopped by 2 cm ripples. Width of 1 and 3 cm didn’t work as in 1 cm electrons emerge out of it, whereas, in 3 cm, they resonate and trap inside. A 2 cm wide was found good. Likewise, 2 cm gap was valuable. Finally, we find that ripples of 2 cm deep, 2 cm wide spaced by 2 cm completely suppressed multipacting, and were adopted for fabrication.
IHEP Beijing, Beijing
TIPC, BeiJing
Funding: NSFC 10525525
With the aim to develop 1.3 GHz superconducting radio-frequency (SCRF） technology in the frame of ILC collaboration, IHEP has started a program to build a SCRF Accelerating Unit. This unit contains a 9-cell 1.3 GHz superconducting cavity, a short cryomodule, a high power input coupler, a tuner, a low level RF system and a high power RF source, etc. This program also includes the SCRF laboratory upgrade, which will permit the unit to be built and tested at IHEP. We will use this unit as a horizontal test stand for many 9-cell cavities and other components (e.g. input couplers, tuners), as in Europe and North America. In this paper, we report the recent R&D status and the future plan of this program.
Cockcroft Institute, Lancaster University, Lancaster
BNL, Upton, Long Island, New York
JLAB, Newport News, Virginia
Lancaster University, Lancaster
In 2017 the LHC is envisioned to increase is luminosity via an upgrade. This upgrade is likely to require a large crossing angle hence a crab cavity is required to align the bunches prior to collision. There are two possible schemes for crab cavity implementation, global and local. In a global crab cavity the crab cavity is far from the IP and the bunch rotates back and forward as it traverses around the accelerator in a closed orbit. For this scheme a two cell elliptical squashed cavity at 800 MHz is preferred. To avoid any potential beam instabilities all the modes of the cavities must be damped strongly, however crab cavities have lower order and same order modes in addition to the usual higher order modes and hence a novel damping scheme must be used to provide sufficient damping of these modes. In the local scheme two crab cavities are placed at each side of the IP two start and stop rotation of the bunches. This would require crab cavities much smaller transversely than in the global scheme but the frequency cannot be increased any higher due to the long bunch length of the LHC beam. This will require a novel compact crab cavity design.
CEA, Gif-sur-Yvette
GANIL, Caen
LPSC, Grenoble
The Spiral2 project at Ganil aims at producing exotic ion beams for Nuclear Physics. The accelerator of the primary beam is a superconducting LINAC designed to provide 5mA deuteron beams at 40MeV. It will also allow accelerating stable ions of different Q/A values ranging from protons to Q/A=1/6 heavy ions. The accelerator should be commissioned by the end of 2011, first beam in 2012; the first tests aiming to produce exotic beams are planned one year later. The superconducting LINAC consists of 12 low beta (0.07) quarter wave (88MHz) superconducting (SC) cavities and 24 beta (0,14) SC cavities integrated in their cryomodule. The status of the low beta cryomodules, supplied by the CEA Saclay Irfu institute, is reported in this paper. The RF full power tests were performed at the end of 2008 on the qualifying cryomodule, and the tests of the first series cavity in vertical cryostat were performed during spring 2009.
CLASSE, Ithaca, New York
Funding: Work supported by NSF Grant PHY 0131508
This paper reports results of cold measurements characterizing the electro-mechanical properties of the Cornell ERL injector cryomodule, which houses five superconducting niobium elliptical 2-cell cavities developed for a high-current (100 mA) low-emittance electron beam. Each cavity is equipped with a blade tuner. The Cornell ERL blade tuner is a modified version of the INFN-Milano design, and incorporates 4 piezoelectric actuators and accelerometers enabling concurrent slow/fast cw RF frequency control and mechanical vibration measurements. Cavity microphonics and fast tuner electro-mechanical transfer functions for all of the cavities have been measured and show the feasibility of stable feedback control at microphonic noise frequencies below ~100 Hz.
CLASSE, Ithaca, New York
Funding: Work supported by NSF Grant PHY 0131508
The RF power required to phase-stabilize the Cornell University ERL main linac cavities is expected to be driven by microphonic-noise. To reduce the required RF power we are exploring the possibility of active compensation of cavity microphonic noise with the cavities in the Cornell ERL injector cryomodule. The Cornell ERL injector cryomodule houses five elliptical 2-cell SRF cavities developed for the acceleration of a high current (100mA) ultra-low emittance beam and is currently undergoing extensive testing and commissioning. Each of the five cavities is equipped with a blade tuner; each blade tuner integrates 4 piezoelectric actuators and vibration sensors for the active compensation of cavity detuning. This paper presents first results of active frequency-stabilization experiments performed with the Cornell ERL injector cryomodule cavities and their integral blade/piezoelectric fast tuners.
CLASSE, Ithaca, New York
Funding: Work Supported by the NSF and DOE
Superconducting RF cavity quench detection is presently a cumbersome procedure requiring two or more expensive cold tests. One cold test identifies the cell-pair involved via quench field measurements in several 1.3 GHz TM010 pass-band modes. A second test follows with numerous fixed thermometers attached to the culprit cell-pair to identify the particular cell. A third measurement with many localized thermometers is necessary to zoom in on the quench spot. We report here on a far more efficient alternative method which utilizes a few (e.g. 8) oscillating superleak transducers (OST) to detect the He-II second sound wave driven by the defect induced quench. Results characterizing defect location with He-II second sound wave OST detection, powering multiple modes of the 1.3GHz TM010 passband to locate multiple defects, and corroborating measurements with carbon thermometers will be presented.
CLASSE, Ithaca, New York
Fermilab, Batavia
Funding: Work Supported by the U.S. Department of Energy
To build the ~14,000 cavities required for the ILC each of the three world regions must have a sizable industrial base of qualified companies to draw cavities from. One of these companies, Niowave Inc., recently manufactured six 1.3 GHz single-cell cavities for qualification purposes. All six cavities achieved gradients above 25 MV/m before they were limited by the available RF power (Q-slope) or quenched. This paper will report the results of cold tests for all six cavities and on the causes of quench determined by 2nd sound detection and optical inspection.
CLASSE, Ithaca, New York
Funding: Work Supported by the U.S. Department of Energy
Cornell University’s superconducting niobium nine-elliptical-cell cavity testing and repair program is one contributor to the collaborative effort on critical SRF R&D for the ILC. The Cornell University program benefits from several unique features which provide for the rapid testing and, if necessary, repair of ILC nine-cell cavities: a continuous vertical electropolish procedure, superfluid helium second sound defect location, and tumble polishing. First, we report on the cavity 2K RF performance and the effect of micro-EP preceding the cavity test. Single-cell results at KEK have shown that micro-EP as a final surface treatment reduces the spread in gradients, but micro-EP has not yet been tried with multi-cell cavities. Secondly, we report on the highly efficient method of detecting defects using a few He-II second sound wave detectors and powering several modes of the 1.3GHz TM010 passband.
CLASSE, Ithaca, New York
Funding: Work Supported by the NSF and the DOE
An innovative reentrant cavity design instigated the initial, highly successful, superconducting niobium reentrant-single-cell cavity tests at Cornell and KEK. Prompted by the success of the single cell program a joint effort of Cornell University and Advanced Energy Systems (AES) fabricated two multiple-cell reentrant cavities: a three-cell and a nine-cell cavity. This paper reports the development status of these two cavities. First, the results of cold tests, superfluid helium defect location and repair work on the reentrant nine-cell cavity will be presented. Second, the results of cold tests, including defect location and repair efforts of the reentrant three-cell cavity will be presented.
Cornell University, Ithaca, New York
Funding: This work is supported by the National Science Foundation.
Cornell University is developing an Energy-Recovery-Linac driven x-ray light source. One of the major components of this accelerator will be its 5 GeV superconducting main linac. The design of the superconducting RF cavities in this main linac has been optimized primarily for two objectives: (1) low RF losses from the accelerating mode to minimize refrigeration cost and (2) strong Higher-Order-Mode damping to preserve low emittance and prevent beam break-up at high beam current (100 mA). In this paper we study the robustness of this optimized cavity design with respect to small cell shape fluctuations from fabrication errors.
CLASSE, Ithaca, New York
Funding: National Science Foundation
Diagnosing field-limiting behavior in multi-cell superconducting cavities can be difficult due to the lack of direct local measurements of cavity surface properties. The results of multiple vertical tests on several 5-cell vertically electropolished 1.3GHz superconducting cavities with measurements of cavity surface properties are presented. A combination of oscillating superleak transducer and resistive thermometry data for various accelerating passband modes are used to infer the field-limiting mechanism for several cells of each multi-cell cavity.
CLASSE, Ithaca, New York
Funding: DOE
The first phase of the Cornell Energy Recovery Linac was the high current, low emittance injector. At present the injector is under commissioning. The next phase calls for the development of multicell cavity for the main linac. The cavities need to have low RF losses to minimize refrigeration and strong HOM damping to preserve low emittance and prevent beam break-up at high current (100 mA). Here we present the RF design of the cavity meeting these requirements.
CLASSE, Ithaca, New York
The superheating magnetic field of a superconducting niobium 1.3 GHz reentrant cavity was measured at several points in the temperature range from (1.7 to 4.4) K. This experimental data is used to discriminate between two competing theoretical s for the temperature dependent behavior of the RF superheating field. Measurements were made with <250 us high power pulses (HPP, ~1MW) to avoid defect initiated thermal breakdown from contaminating the data. Our test incorporated oscillating superleak transducers to determine the cavity quench locations and characterize changes and the migrations of the quench locations during processing. This information provides insight into the factors which limit the ultimate achievable RF surface magnetic field.
DESY, Hamburg
JLAB, Newport News, Virginia
A coaxial coupling device located in the beam pipe of the TESLA type superconducting cavities provides for better propagation of Higher Order Modes (HOMs) and their strong damping in appropriate HOM couplers. Additionally, it also provides efficient coupling for fundamental mode RF power into the superconducting cavity. The whole coupling device can be designed as a detachable system. If appropriately dimensioned, the magnetic field can be minimized to a negligible level at the flange position. This scheme, presented previously*, provides for several advantages: strong HOM damping, flangeable solution, exchangeability of the HOM damping device on a cavity, less complexity of the superconducting cavity, possible cost advantages. This contribution will describe the results of the first cryogenic test.
*J. Sekutowicz et al., Proceedings LINAC08, Victoria, Canada, 2008.
DESY, Hamburg
ACCEL, Bergisch Gladbach
W.C. Heraeus GmbH, Materials Technology Dept., Hanau
A test program of 1.3 GHz TESLA shape 9-cell large grain (LG) resonators for the European XFEL project was started at DESY. The main aim is to find out whether or not the choice of LG material could be an option for the fabrication of approx. 800 XFEL resonators. Several aspects are under investigation and will be compared with the conventional polycrystalline material option. One of the aspects is the material issue: could the required amount of LG niobium be produced at industry in a cost effective and reliable manner? The second issue is the fabrication of cavities: could the series production of resonators be done on the level of required accuracy and costs? The third one is the performance issue: what is the appropriate treatment for reproducibly achieving the specified XFEL accelerating gradients? Development of the LG disc production was done within the framework of the R&D program of DESY and W. C. HERAEUS. Eleven resonators are produced at the company ACCEL. Up to now three resonators are RF-tested vertically. The He-vessel was welded onto one of the resonators which passed the horizontal RF-test. The data and perspectives of the LG cavity application are discussed.
DESY, Hamburg
JLAB, Newport News, Virginia
Technological aspects of seamless tube fabrication and multi-cell cavity production by hydroforming will be discussed. Problems related to the fabrication of seamless cavities from bulk niobium are mainly solved. Several two cell- and three cell- niobium cavities have been produced by hydroforming at DESY. A 9-cell cavity of the TESLA shape has been completed from three sub-sections at company ZANON. The cavity was treated by electropolishing (EP) and successfully RF-tested. Two 3-cell units equipped with niobium beam pipes are being RF-tested after BCP surface treatment. The temperature mapping method with Jlab’s two-cell thermometry system is applied for performance analysis. It is of particular interest to compare the seamless cavity quench locations to those from standard cavities. The cryogenic test results and the T-mapping findings will be discussed. Of special interest is the combination of the seamless technique with NbCu cladding, i.e. the fabrication of cavity from bimetallic clad NbCu tube by hydroforming. Fabrication of single-cell and multi-cell NbCu clad cavities by hydroforming from bimetallic tubes is proven. Some test results will be presented.
Fermilab, Batavia
DESY, Hamburg
A series of four automatic tuning machines for 9-cell TESLA-type cavities are being developed and fabricated through a collaboration between DESY, FNAL and KEK. These machines are intended to support high-throughput cavity fabrication for construction of large SRF-based accelerator projects. Two of these machines will be delivered to cavity vendors for the tuning of XFEL cavities. The control system for these machines must support a high level of automation adequate for industrial use by non-expert operators. This paper describes the control system hardware and software designs, and shows preliminary results obtained with a tuning machine prototype.
Fermilab, Batavia
Combined temperature mapping and optical inspection of SRF cavities has revealed defects near the edge of the heat affected zone (HAZ) of numerous welds. We have re-created similar defects on welded coupons that were electropolished in the lab and characterized by a variety of tools. Several features that may have bearing on the origin of these defects are discussed, such as their location relative to grain boundaries, the strain state of the niobium prior to welding and etching, the electropolishing parameters, and so forth. Since coupons are useful for distribution to academic researchers, we also describe other detailed characterizations.
Fermilab, Batavia
Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-07CH11359.
Fermilab is in a collaboration with DESY to provide a cryomodule containing 4-3.9 GHz superconducting RF cavities to be placed in TTF/FLASH. The purpose of this 'Third Harmonic' module is to linearize the nonlinear beam energy-time profile produced by the 1.3 GHz accelerating gradient. The completed module has now been shipped to DESY and is awaiting cold, powered testing and installation into FLASH later this year. We report on experience with fabricating, testing, assembling, and shipping the module and its components with a focus on cavity test results.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy.
Recently developed, the Superconducting Radio Frequency (SRF) Accelerator Test Facilities at Fermilab supports the International Linear Collider (ILC), High Intensity Neutrino Source (HINS), a new high intensity injector (Project X) and other future machines. These facilities; Meson Detector Building and New Muon Lab (NML) have very different foundations, structures, relative elevations with respect to grade level and surrounding soil composition. Also, there are differences in the operating equipment and their proximity to the primary machine. All the future machines have stringent operational stability requirements. The present study examines both near-field and ambient vibration in order to develop an understanding of the potential contribution of near-field sources (e.g. compressors, ultra-high and standard vacuum equipment, klystrons, modulators, utility fans and pumps) and distant noise sources to the overall system displacements. Facility vibration measurement results and methods of possible isolation from noise sources are presented and discussed.
Fermilab, Batavia
Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359
The Fermilab High Intensity Neutrino Source (HINS) Linac R&D program is building a 60 MeV superconducting H- linac. The Linac incorporates SC solenoids, high power RF vector modulators and SC spoke-type accelerating cavities starting at 10 MeV. This will be the first application and demonstration of any of these technologies in a low-energy, high-intensity proton/H- linac. The HINS effort is relevant to a high intensity, SC H- linac that might serve the next generation of neutrino physics and muon storage ring/collider experiments. Three types of superconducting resonators are used in the linac front end. Single Spoke Resonators typs-1 (SSR1) at Beta=0.2, Single Spoke Resonators type-2 (SSR2) at Beta=0.4 and Triple Spoke Resonators (TSR) at Beta=0.6. In this paper we describe the Buffer Chemical Polishing (BCP) performed on SSR1-#2 and the results of the cold tests for this bare cavity. We also describe the inelastic tune performed on cavity SSR1-#1, during this operation we measured also the spring constant and the frequency sensitivity of the end walls. We have also completed the design for the helium vessel that will be used to jacket SSR1 resonators and we present its design here.
Fermilab, Batavia
Different couplers are described that allow the reduction of both transverse wake potential and RF kick in the SC acceleration structure of ILC. A simple rotation of the couplers reducing the RF kick and transverse wake kick is discussed for both the main linac and bunch compressors, along with possible limitations of this method. Designs of a coupler unit are presented which preserve axial symmetry of the structure, and provide reduced both the RF kick and transverse wake field.
Fermilab, Batavia
Euclid TechLabs, LLC, Solon, Ohio
KEK, Ibaraki
The accelerating gradient required for the ILC project exceeds 30 MeV/m. With current technology the maximum acceleration gradient in SC structures is determined mainly by the value of the surface RF magnetic field. In order to increase the gradient, the RF magnetic field is distributed homogeneously over the cavity surface (low-loss structure), and coupling to the beam is improved by introducing aperture "noses" (re-entrant structure). These features allow gradients in excess of 50 MeV/m to be obtained for a singe-cell cavity. Further improvement of the coupling to the beam may be achieved by using a TW SC structure with small phase advance per cell. We have demonstrated that an additional gradient increase by up to 46% may be possible if a pi/2 TW SC structure is employed. However, a TW SC structure requires a SC feedback waveguide to return the few GW of circulating RF power from the structure output back to the structure input. Advantages and limitations of different techniques of exciting the traveling wave in this structure are considered, including an analysis of mechanical tolerances. We also report on investigations of transient processes in the SC TW structure.
Fermilab, Batavia
MIPT, Dolgoprudniy, Moscow Region
Long 11-cell, beta=0.81 L-band structure is considered as an initial stage of the high-energy part of the Project-X in order to accommodate to a standard CM4 cryomodule. The cavity shape is optimized for maximal energy gain providing the same time field flatness along the structure not worse than for ILC beta=1 cavity, and the same ratio of surface magnetic field to electric field. The results of spectrum analysis for monopole and dipole HOMs is presented as well as the HOM damper design.
Fermilab, Batavia
In the paper the Crab Cavity is described for local Crab schemes for LHC that demand reduced transverse cavity dimensions small enough to fit limited space necessary for the beams separation. The results of the configuration cavity optimization are presented that include (a) the surface field minimization; (b) parasitic monopole and dipole spectrum optimization and dumping, (c) the input and the parasitic mode damping couplers design. The results of multipacting simulations, which were performed in order to understand the possible gradient limitations, are discussed also.
FZJ, Jülich
Forschungszentrum Jülich GmbH, Institut fur Nuklearchemie (INC), Jülich
The paper describes the design, fabrication and first test results of the triple-spoke cavity (resonant frequency 352 MHz, beta=0.48) developed at Forschungszentrum Jülich in the frame of High Intensity Pulsed Proton Injector project. The cavity has 5 cm diameter beam aperture, a transverse radius of 21.7 cm and the whole length of 78 cm. An initial wall thickness of niobium sheets used for cavity fabrication was around 4 mm. The RF cavity design has been adapted to two main goals - the simplest technology of cavity manufacture and for the prime goal of the project to achieve the best possible structural parameters (Lorenz force frequency shift and a resonant frequency pressure dependence). Intense cavity structural analyses have been conducted and the further prospectives on cavity developments are also presented. Construction of the niobium cavity prototype has been completed, the cavity has been chemically processed. Results of initial cold test are discussed.
FZJ, Jülich
CEA, Gif-sur-Yvette
The driver of the International Fusion Material Irradiation Facility (IFMIF) consists of two 125 mA, 40 MeV cw deutron accelerators. A superconducting option for the 5 to 40 MeV linac is based on Half-Wave Resonators (HWR) has been choosen. The first cryomudule should contain 8 HWR's with resonant frequency of 175 MHz and beta=v/c=0.094. The paper describes RF design of half-wave length resonator. The requirents on high power coupler define its installation in the cavity central region. Few options of cavity tune were investigated, the capacitive tuner installed opposite to the coupler port have been accepted. The cavity structural analyses have been conducted and cavity stiffening has been worked out.
KEK, Ibaraki
KAKEN Inc., Mito
Sokendai, Ibaraki
In order to achieve higher and more stable performance of super conducting radio-frequency (SRF) cavities, extensive effort in development and application has been done for surface treatment and conditioning methods. Those methods have been evaluated with vertical tests showing lots of remarkable results in cavity performance. However it cannot be well understood yet how surface treatment or conditioning contributed to the results and which step of process in the treatment or conditioning affected the results. In this article, we describe our try to understand those questions focusing on the surface analyses with scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) for electro-polishing (EP) processed niobium sample coupons.
KEK, Ibaraki
A cryomodule including three 2-cell sc cavities was designed for the ERL injector Linac, which is operated at the beam energy of 10 MeV and the beam current of 100 mA. A prototype 2-cell cavity with two input coupler ports and four HOM couplers was fabricated. The double input couplers is to reduce the power per coupler and to keep a symmetric filed configuration around the coupler port. Required rf power in the input couplers is about 200 kW in the cw operation. First vertical test of the 2-cell cavity will be carried out in March.
KEK, Ibaraki
JLAB, Newport News, Virginia
The Electro-polishing process is the best candidate of final surface treatment for the production of ILC cavities. Nevertheless, the broad distribution of the gradient caused by field emitters in cavities is sitll a serious problem for the EP process. Ethanole- and degreaser-rinse processes after the EP process were found to be effective to decrease the field emmitter in recent studies, however, these are not perfect yet. We tried to test the sponge cleaning as the post EP process to remove the field emitter inside the cavcity. This article describe the results of series tests with a proto-type sponge-cleaning tool for single-cell cavity at KEK.
KEK, Ibaraki
Kyoto ICR, Uji, Kyoto
The inspections of the superconducting RF cavities seem essential in achieving high accelerating gradient. The Kyoto camera system is a good tool to survey a defect location and to be analysis a defect shape in the inner surface of the superconducting rf cavities. The cavity inspections of the AES, ACCEL, ZANON and STF Baseline cavities were inspected to study relations between a defect shape and a heating gradient of the superconducting rf cavities. The STF Baseline #5 and #6 cavities with each surface treatment (as received, after Pre-EP, after EP-1, and after vertical test with EP-2) were inspected to trace a changing spots shape. The full inspection of the EBW seam, the HAZ (heat affected zone) and hot spots region were carried out before EP-2 process and a vertical test then the shape analysis of a discovered spots was done. The vertical tests of these cavities with T-map of fixed 9-cell type were measured at STF from September 2008. The inspection and shape analysis of these cavities were made after vertical tests for based on T-map data. The result of vertical tests and changing a shape of a discovered spots with EP-2 process will be presented.
KEK, Ibaraki
ISSP/SRL, Chiba
TIPC, BeiJing
A new vertical test facility for L-band multi-cell cavities has been completed in support of development efforts of ILC (International Linear Collider) and ERL (Energy Recovery Linac) projects at STF (Superconducting rf Test Facility) of KEK. The facility possesses a clean booth for pre-tuning the cavities, four cavity stands to prepare the cavities prior to vertical testing, a half-underground pit which accommodates up to two vertical cryostats which can be pumped and operated separately under a movable iron shield. Vertical testing of the cavities, with a 400 W high-power amplifier and with a temperature-mapping (T-mapping) and additional monitoring systems, is supervised from a control room which overlooks the entire facility. This paper describes the specific details of the facility and results from its initial pilot operation that was conducted in Summer-Fall of 2008.
KEK, Ibaraki
TIPC, BeiJing
A pulsed RF operation of four units of 9-cell L-band (1.3 GHz) cavities in a horizontal cryostat (cryo-module) was conducted in 2008 as part of R&D efforts at STF at KEK for ILC. A series of compensation experiments were conducted for Lorentz-detuning effects, which are critically important for pulsed RF operation of high-gradient linacs based on superconducting cavity technologies. The experiments were done at a repetition rate of 5 Hz with RF pulses of a width of 1.5 msec, and the typical accelerating gradient within the cavities was 20 32 MV/m. Two types of compensation techniques have been tested. In a “feed-forward” method, piezo actuators on individual cavity tuners are activated to mechanically control the tuning of the cavity in synchronization with the RF pulses. In a “feed-back” method, the low-level RF system is driven so as to maintain the average of “I” and “Q” components of the cavities as constant. This paper reports the experimental results using the various parameters of the piezo control to compensate the effect of Lorentz-detuning. These results are consistent with the numerical calculation postulating that two mechanical modes mainly contribute to the effect.
KEK, Ibaraki
ISSP/SRL, Chiba
TIPC, BeiJing
A new cavity diagnostic system has been introduced for vertical testing of nine-cell L-band superconducting cavities at KEK-STF. The present system is based on approximately 300 carbon resistors for temperature-mapping (T-mapping), and approximately 40 PIN photo diodes for detecting emission of X-rays. The system can accommodate up to total 600 sensors in needed in the future. While most of the sensors are attached to the cavity exterior in a pre-determined regular pattern, some sensors can be strategically placed at non-regular positions so as to watch the areas which are considered “suspicious” as per the surface inspection done prior to vertical testing. Data from the sensors can be collected every 100 msec. The data can be graphically displayed online and are stored for offline analysis. This paper describes the details of this system, together with results from its initial pilot operation which was done with a nine-cell cavity on loan from FNAL (AES#001). Effectiveness of the combined use of T-mapping and PIN photo diodes in operation of the pi-mode and other pass-band modes in conjunction with surface inspection is discussed.
ANL, Argonne
Funding: U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Work is underway to improve the reilability and power handling capability of input couplers used in the Advanced Photon Source single-cell and five-cell cavities. Coupler performance during conditioning in a test cavity suggests that ceramic material defects and field enhancement caused by a mechanical gap in the coupler design may be responsible for past coupler failures at high power. Simulation results and high-power test data will be discussed.
ANL, Argonne
Funding: U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An investigation into development of a 200-kW CW solid state rf power system design to replace the existing klystron-based 352-MHz rf systems at the Advanced Photon Source has been started. The baseline 352-MHz solid state system design will consist of multiple 1-kW CW modules combined to produce a total output capability of 200-kW CW, sufficient to drive one single-cell storage ring cavity. A description of the 1-kW CW module building block of the solid state power sistem will be presented, along with results from hardware evaluation tests at the 1-kW CW level.
BNL, Upton, Long Island, New York
Continental Electronics Corp., Dallas, Texas
CPI, Palo Alto, California
Funding: DoE Contract No. DE-AC02-98CH10886
Brookhaven’s ERL (Energy Recovery LINAC) requires a 1 MW CW RF system for the superconducting electron gun cavity. The system consists primarily of klystron tube, transmitter, and High-Voltage Power Supply (HVPS). The 703.75 MHz klystron made by CPI, Inc. provides RF power of 1 MW CW with efficiency of 65%. It has a single output window, diode-type electron gun, and collector capable of dissipating the entire beam power. It was fully factory tested including 24-hour heat run at 1.1 MW CW. The solid state HVPS designed by Continental Electronics provides up to 100 kV at low ripple and 2.1 MW CW with over 95% efficiency. With minimal stored energy and a fast shut down mode no crowbar circuit is needed. Continental’s transmitter includes PLC based user interface and monitoring, RF pre-amplifier, magnet and Vac-Ion pump supplies, cooling water instrumentation, and integral safety interlock system. BNL installed the klystron, HVPS, and transmitter along with other items, such as circulator, water load, and waveguide components. The collaboration of BNL, CPI, and Continental in the design, installation, and testing was essential to the successful operation of the 1 MW system.
DESY Zeuthen, Zeuthen
DESY, Hamburg
The European XFEL, an X-ray free electron laser, is planned as an European project with a strong connection to the DESY research center in Hamburg. The LINAC of the XFEL incorporates 27 RF stations, which supply the RF power required by the superconducting cavities. In order to generate the RF power (1.3 GHz, 10MW pulses) HV pulse modulators are required. Each modulator has to supply 12kV pulses at 1.6kA for 1.5ms pulse duration and at 10Hz nominal repetition rate. The repetition rate can be increased to 30Hz at shorter pulse duration. Although extensive experience exists from the test facilities FLASH and PITZ (DESY Hamburg and Zeuthen sites) a dedicated modulator test stand has been setup to test and investigate additional new modulator prototypes developed by different companies. The results of these tests and the experience gained with the RF-stations at PITZ and FLASH will be an important criterium for the decision on the final layout and choice of vendor. An overview of the Modulator Test Facility at DESY will be presented. The first of two prototypes was delivered in July 2008 and started its operation in October. First test results of this prototype will be presented.
Diversified Technologies, Inc., Bedford, Massachusetts
Funding: U.S. Department of Energy SBIR Program
Constructing and supporting a wide range of RF amplifiers for research accelerators at is costly at present. This is because amplifiers to date have been designed for a single application, and have little commonality in their design and control interfaces. Diversified Technologies, Inc. (DTI) is developing a modular RF amplifier design for a wide range of amplifier requirements. Amplifiers built on this model have common design, controls, and spares, independent of frequency or power. The amplifier design combines a solid-state RF driver, power conditioning, and controls with a high-power vacuum electronic device, giving high performance at a low cost. In this paper, DTI will describe results of the first implementation of the amplifier, which delivers 20 kW CW at 704 MHz.
Fermilab, Batavia
Omega-P, Inc., New Haven, Connecticut
Yale University, Physics Department, New Haven, CT
Funding: Sponsored in part by US Department of Energy, Office of High Energy Physics.
A preliminary design is presented for a two-cavity 7th harmonic multiplier, intended as a high-power RF source for use in experiments aimed at developing high-gradient structures for a future collider. The harmonic multiplier is to produce power in K-band using as an RF driver an XK-5 S-band klystron (2.856 GHz). The device is to be built with a TE111 rotating mode input cavity and interchangeable output cavities, a principal example of which is a TE711 mode cavity running at 19.992 GHz. Design of the harmonic multiplier is described that uses a 250 kV, 20 A injected laminar electron beam. With 10 MW of S-band drive power, 4.7 MW of 20-GHz output power is predicted. Details are described of the gun beam optics, beam dynamics in the RF system, and of the magnetic circuit. The theory of an azimuthally distributed coupler for the output cavity is presented, as well as the conceptual design of the entire RF circuit.
KEK, Ibaraki
The super-conducting RF test facility (STF) at KEK has been functional since 2005, and the STF phase-I, which involves the testing of a cryomodule with four superconducting cavities, was performed at the end of 2008. In this test, intense study of the power distribution system for the possible linear collider scheme was performed. Linear power distribution and tree-like distribution were compared and also the effects of eliminating circulator are studied. Current status of RF source of KEK STF are reported.
Nano, Moscow
RAS/INR, Moscow
Solid State High Power RF System is proposed for XFEL and ILC. It includes individual RF power supply for each SC cavity and common control system. Each RF power supply includes Solid State Generator, circulator and Q-tuner. Triggering, synchronization, output power and phase of each Solid State Generator are controlled from the common control system through fiber-optic lines. Main parameters of Solid State Generator are: frequency 1.3 GHz, peak power 128 kW, pulse length 1.4 msec, repetition rate 10 Hz, average power 1.8 kW, CW power 2.5 kW. Advantages of Solid State High Power RF System are: simple triggering, synchronization, output power and phase adjustment for all cavities separately, operation both in pulse and in CW modes, unlimited lifetime, no high voltage, no oil-tank, compactness.
ORNL, Oak Ridge, Tennessee
ORNL RAD, Oak Ridge, Tennessee
Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
The SNS has been operational and delivering beam to the target for 3 years. Over this time period we have increased the beam power delivered to the target to 700 kW, 50% of the design goal. The RF Group has acquired a fair amount of experience in the operation and maintenance of our RF systems during the power ramp up process. This paper reviews the design and layout of the various SNS RF systems, documents the present state and performance of the systems and covers, in a broad sense, issues raised during operation and improvements we have undertaken as well as future RF system requirements.
PAL, Pohang, Kyungbuk
Funding: Supported by the Korea Ministry of Science and Technology mhchun@postech.ac.kr
The RF system for the Pohang Light Source (PLS) storage ring is operating at total maximum RF power of 300kW with four 75kW klystron amplifiers and four PF-type normal conductivity(NC) RF cavities for 190mA at 2.5GeV. The PLS will be upgraded from 2.5GeV/200mA to 3.0GeV/400mA in the near future. Therefore the RF system should be greatly upgraded to supply total 627kW beam power. We are investigated the some upgrade ways with adding NC cavities or new super conductivity(SC) RF cavities. According to the cavity type, the high power RF system will be adjusted the total RF power, and source type and quantity such as klystron or IOT. This paper describes the present operation status and several optional ways of high power RF system for the upgrade project of PLS storage ring
BINP SB RAS, Novosibirsk
Yale University, Physics Department, New Haven, CT
KEK, Ibaraki
Fermilab, Batavia
Funding: Sponsored in part by US Department of Energy, Office of High Energy Physics.
Conceptual design of a multi-beam klystron (MBK) for ILC and Project X application is presented. The chief distinction between the MBK design and existing 10-MW MBK’s is the low operating voltage of 60 kV. There are at least four compelling reasons that justify development of a low-voltage MBK, namely (i) no pulse transformer would be required; (ii) no oil tank would be required for the tube socket; (iii) modulator would be a compact 60-kV IGBT switching circuit. The proposed klystron consists of four clusters that contain six beams each. The tube has common input and output cavities for all 24 beams, and individual gain cavities for each cluster. A closely related optional configuration for a 10 MW tube would involve a design having four totally independent cavity clusters and four 2.5 MW output ports, all within a common magnetic circuit. This option has appeal because the output waveguides would not require a controlled atmosphere and because it would be easier to achieve phase and amplitude stability as required in individual SC cavities.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
EMMA is a prototype non-scaling FFAG that requires a demanding RF system. Production for the final RF system is due for completion in Spring 09 and testing of the combined hardware has taken place. This paper describes the high power verification tests of the IOT transmitter, waveguide distribution, RF cavity and LLRF control system.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The Muon Ionisation Cooling Experiment (MICE) at the Rutherford Appleton Laboratory uses normal conducting copper cavities to re-accelerate a muon beam after it has been retarded by liquid hydrogen absorbers. Each cavity operates at 200MHz and requires 1MW of RF power in a 1ms pulse at a repetition rate of 1Hz. In order to provide this power, a Thales TH116 triode, driven by a Burle 4616 tetrode is used, with each amplifier chain providing ~2.5MW. This power is then split between 2 cavities. The complete MICE RF system is described, including details of the low level RF, the power amplifiers and the coaxial power distribution system. Testing of the amplifier chain, power supplies and low level RF is described.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
ALICE (Accelerators and Lasers in Combined Experiments) incorporates two super-conducting radio frequency (SCRF) cryomodules each with two identical 9-cell cavities that are powered by 5 inductive output tubes (IOTs) from 3 different commercial suppliers. During the commissioning of the ALICE rf system numerous problems were encountered with the operation of the high voltage power supply and the auxiliary power supplies, which had to be resolved before the beam commissioning of the accelerator could commence. The issues encountered and measures taken to improve the operation of the rf system are described within this paper.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
EMMA (Electron Model for Many Applications) is a non-scaling Fixed Field Accelerating Gradient (NS-FFAG) accelerator presently in the process of being built at Daresbury Laboratory as a proof of principle demonstrator for proton/carbon therapy application. Its aim is to take an injected beam from ALICE (Accelerators and Lasers in Combined Experiments) at 10MeV and accelerate it to 20MeV, so that the characteristics of NS-FFAGs can be studied. The beam is to be accelerated by 19 identical 1.3GHz RF cavities, which each need to provide the same accelerating voltage to the beam. The initial design stage of the RF system design has been completed, utilising three commercial suppliers of the major RF sub-system components.
ELETTRA, Basovizza
The full energy injection is now the standard procedure for the Elettra synchrotron radiation light source. The four RF storage ring plants have been benefited by this procedure in terms of reliability and stability of operation. The injector booster RF plant is running well. A new High Order Mode (HOM) diagnostic board has been implemented using the radiofrequency (RF) cavity’s signal to improve the HOM’s detection. The analysis and the performances of the new Inductive Output Tube (IOT)based RF power transmitter are presented.
ELETTRA, Basovizza
Funding: The work was supported in part by the Italian Ministry of University and Research under grant FIRB-RBAP045JF2
The former linac sections used in the injector system of the Elettra Laboratory storage ring will be upgraded for use on the FERMI@elettra project, a free-electron laser user facility operating down to 3 nm. These seven accelerating sections are 3π/4 mode backward-travelling wave (BTW) constant-impedance structures, powered by 45 MW TH2132A klystrons couple to what was called a PEN – power enhancement network, or more commonly referred to as a SLED system. Due to breakdown problems inside the sections, that was the result of high peak fields generated during conventional SLED operation, the sections experienced difficulties in reaching the design gradients. To lower the peak field and make the compressed pulse “flatter”, phase-modulation of the SLED drive power option is investigated. This paper presents the results of this investigations and includes a detailed mathematically analysis.
SESAME, Amman
Funding: SESAME (Synchrotron light-source for Experimental Science and Applications in the Middle-East) Allan, Jordan
The SESAME (Synchrotron light source for Experimental Science and Applications in the Middle-East) accelerator consists of a 22MeV Microtron, an 800MeV booster synchrotron and a 2.5GeV storage ring. Each accelerator has its own RF system. The Microtron RF frequency is 3GHz generated by a 2MW pulsed Magnetron while the booster and storage ring have a common 500MHz CW RF source. The Booster RF system consists of a DORIS cavity fed by a 2kW CW solid-state RF amplifier but the storage ring (SR) RF system has been designed based on four 500 MHz plants, each comprising a normal conducting (NC) single-cell cavity , powered with 140 kW (CW) by two combined 80kW IOTs to have maximum possible RF power in the cavity via a WR1800 waveguide line. In the initial phase, it has been decided to start with two ELETTRA type cavities and in final phase, four cavities will be accommodated in one straight section in the storage ring to have nominal energy and current in the machine. This paper presents status of installed Microtron RF system and modified booster RF system from BESSY I, as well as designed SESAME storage ring high power RF system and low level electronics.
ANL, Argonne
JLAB, Newport News, Virginia
Funding: * Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A superconducting multi-cell cavity for the production of short x-ray pulses at the Advanced Photon Source (APS) has been explored as an alternative to a single-cell cavity design in order to improve the packing factor and potentially reduce the number of high-power RF systems and low-level RF controls required. The cavity will operate at 2815 MHz in the APS storage ring and will require heavy damping of parasitic modes to maintain stable beam operation. Novel on-cell dampers, attached directly to the cavity body, have been utilized by taking advantage of the magnetic field null on the equatorial plane in order to enhance damping. Design issues and simulation results will be discussed.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
ALBA is the first 3rd generation synchrotron light source to be build in Spain. The project is in the process of installation, with the LINAC already commissioned, and the Booster and Storage Ring in the installation phase, and the building already completed. The Booster synchrotron is expected to be finish and commission by the end of summer 2009, and the storage ring commissioning should take place in spring 2010. Most of the major components are already delivered and tested in-house, among those the vacuum system, the magnets, the RF cavities, etc. In this paper, the status of the project and of the most relevant components is reviewed.
ANL, Argonne
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An x-ray radiation source based on a free-electron laser (FEL) oscillator was recently proposed as a complementary facility to those based on self-amplified spontaneous emission*. Such a source uses narrow-bandwidth Bragg mirrors and a low-emittance, high-brightness electron beam to produce coherent, intense pulses of hard x-ray radiation. We present a study of the FEL oscillator performance and radiation characteristics at several potential wavelengths using a variety of electron beam and undulator parameters. Our simulations include realistic complex mirror reflectivities calculated from dynamical diffraction theory, and highlight additional constraints imposed by a four-mirror cavity that can provide tunable FEL radiation. We comment on how this concept may be extended to soft x-rays using dielectric multilayer mirrors.
*K.-J. Kim, Y. Shvyd'ko, S. Reiche, Phys. Rev. Lett. 100, 244802 (2008)
DESY, Hamburg
The European XFEL contains hundreds of sources of the coupled impedances. To have an overview of them an impedance budget database is developed. It contains wake functions of the point charge (Green functions) and allows to calculate the wake potentials for arbitrary bunch shapes.
Diamond, Oxfordshire
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Several new light source projects aim at the production of X-ray photons with high repetition rate (1kHz or above). We present here the results of the start-to-end simulations of a 2.2 GeV superconducting LINAC based on L-band SC Tesla-type RF cavities and the corresponding optimisation of the FEL dynamics at 1 keV photon energy.
ENEA C.R. Frascati, Frascati (Roma)
We explore the possibility of using free-electron laser (FEL) triggered cathodes to produce high quality e-beams. We propose a scheme which foresees cathodes operating either as thermionic and photo-cathodes, which can be exploited in devices using the same e-beam to drive the laser and the cathode. We discuss different modes of operation, in particular we consider oscillator FELs, in which the light from higher order harmonics, generated in the oscillator cavity, is used to light the cathode. The dynamics of the system is explored along with the technical solutions, necessary for the stability of the system. The Master Oscillator Power Amplifier FEL scheme is explored too. The use of the same e-beam, driving the photocathode and the FEL, makes the system naturally free of any synchronization problem, arising when an external laser is used. The device is a kind of regenerative amplifier in which the growth of the optical power can be controlled by using a proper detuning or misalignment of the optical cavity. Specific examples are reported. The use of this technique for an ab-initio control the Coherent Radiation Synchrotron instability is finally discussed too.
FEL/Duke University, Durham, North Carolina
PKU/IHIP, Beijing
Funding: Work supported by US Air Force Office of Scientific Research medical FEL grant FA9550-04-01-0086.
The storage ring based free electron laser (FEL) oscillator serves as a photon driver for the High Intensity Gamma-Ray Source (HIGS) at Duke University. The FEL cavity consists of two concave mirrors with a large radius of curvature of more than 27 m. Both cavity mirrors see very high intensity intracavity FEL power; the downstream mirror also receives higher harmonic spontaneous UV-VUV radiation of wigglers. The large heat load by various types of radiation can deform the mirror surface, causing FEL mode distortion. The FEL mirror can also be damaged by intense UV-VUV wiggler harmonic radiation. To mitigate these problems, a pair of water-cooled, in-vacuum apertures have been installed inside the FEL cavity. These apertures are ideal for manipulating the FEL transverse profile. This paper reports our study on the FEL transverse mode shaping using these apertures, including the characterization of the transverse mode structure of the FEL beam under a variety of operation conditions. These studies allow us to minimize the diffraction loss of the fundamental mode of the FEL while effectively reducing the impact of off-axis UV-VUV wiggler radiation on the FEL mirrors.
ANL, Argonne
Funding: This work was supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The envisioned next-generation ERL-based x-ray light sources demand costly CW superconducting linacs and high-brightness high-current photoinjectors that are beyond the state of the art. To overcome the fiscal challenge of a multi-GeV CW superconducting ERL and the physical challenge of high-brightness high-current CW photoinjectors, we explore a new scheme using multi-beam injection into a quasi-CW ERL. Multi-beam injection lowers the burden on individual rf injectors at subharmonics of the linac frequency. Lower injector frequency allows higher bunch charge, which permits lower duty factor of the linac with significant reduction in construction and operation costs. Preliminary studies foresee many benefits and no obvious physical showstoppers, despite potential technical challenges. Here we provide a simulation study of a preliminary design.
KEK, Ibaraki
JAEA/ERL, Ibaraki
JASRI/SPring-8, Hyogo-ken
ISSP/SRL, Chiba
UVSOR, Okazaki
HU/AdSM, Higashi-Hiroshima
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
AIST, Tsukuba
Future synchrotron light source project using an energy recovery linac (ERL) is under proposal at the High Energy Accelerator Research Organization (KEK) in collaboration with several Japanese institutes such as the JAEA and the ISSP. We are on the way to develop such key technologies as the super-brilliant DC photo-injector and superconducting cavities that are suitable for both CW and high-current operations. We are also promoting the construction of the Compact ERL for demonstrating such key technologies. We report the latest status of our project, including update results from our photo-injector and from both superconducting cavities for the injector and the main linac, as well as the progress in the design and preparations for constructing the Compact ERL.
ISSP/SRL, Chiba
JAEA/ERL, Ibaraki
KEK, Ibaraki
A compact ERL (energy recovery linac) is planned in Japan in order to demonstrate excellent ERL performances and to test key components such as low-emittance photocathode gun and superconducting RF cavity. We studied and optimized the compact ERL optics (except the injector part) to generate a subpico-second bunch in bunch compression mode and to preserve the beam emittance in normal and low-emittance mode. As a result, we could obtain a very short bunch of about 50 fs with a charge of 77 pC in bunch compression mode and almost keep the normalized emittance of 0.1 mm mrad with a charge of 7.7 pC in low-emittance mode. We also designed it to achieve efficient energy recovery at the superconducting RF cavities and to transport the beam to the dump section without serious loss. The design study of the compact ERL optics was carried out with the simulation code Elegant, including CSR(coherent synchrotron radiation) effects. In this paper, we will present the results of the beam optics study for the compact ERL.
Plansee Metall GmbH, Reutte
W.C. Heraeus GmbH, Materials Technology Dept., Hanau
Sheet material made of high-purity Niobium (Nb-RRR) is the key component for future linear accelerators based on the superconducting radio-frequency technology. To be prepared for large production scale quantities, which are demanded for the upcoming projects like XFEL and ILC respectively, W.C. Heraeus (D) and Plansee SE (A) joined there competencies in the field of Nb-RRR. In 2007 the qualification procedure as material supplier for the XFEL project could be successfully finished and a complete product and technology package for products made of Nb-RRR was established. Based on the combination of the high expertise and long-term experience in electron beam melting of different Nb-RRR qualities; the knowledge and availability of various processing technologies for manufacturing of semi-finished and ready to assemble components; and the unique analytical capabilities for advanced quality control along the process chain customized product solutions can be realized for the accelerator industry. Beside a general overview about the production capabilities a strategy for installation of a Quality-Assurance-Management system for large production scale quantities are presented.
UTNL, Ibaraki
The University of Tokyo, Nuclear Professional School, Ibaraki-ken
A, Kawasaki, Kanagawa
AET Japan, Inc., Kawasaki-City
We are developing X-ray nondestructive testing (NDT) system using with portable X-band linac. This system uses 9.4 GHz X-band linac and 250 kW magnetron. Our system energy is 950 keV for Japanese regulation. Therefore we can use it on-site using local radiation protection. We measured electron beam and X-ray. We have started X-ray imaging test. We will use this system for condition based maintenance of pump-impeller at nuclear plants. The linac based X-ray source can generate pulsed X-ray. Therefore we can get still images without stopping rotation when x-ray repetition rate synchronizes impeller's rotaion rate. We are successfull in proof of principle using a simple fan and a synchronized circuit. We prepare real-time imaging for conventional pump. In this paper, we will explain the detail of this system and expermental results.
Hitachi, Ltd., Energy and Environmental Systems laboratory, Hitachi-shi, Ibaraki-ken
Hitachi Ltd., Power & Industrial Systems, 1-1, Saiwai-cho, 3-chome
Hitachi, Ltd., Energy and Environmental System Laboratory, Hitachi-shi
Slow cycle synchrotron system for cancer therapy is presented to realize the pencil beam scanning with carbon and proton. The designed synchrotron’s circumference is 60m and the maximum beam energies are 480MeV/u for carbon and 250MeV for proton. These energies correspond to the beam range of 35cm in water. In the treatment system with the present synchrotron, the discrete spot scanning scheme for lateral irradiation is employed using fast beam ON/OFF that is characteristic of the RF driven slow beam extraction from the synchrotron. Distal dose distribution is controlled with energy stacking technique, which is superimposing various bragg peaks which are controlled with the energy of the beam accelerated by the synchrotron. Furthermore, respiratory-gated operation with high throughput will be realized by the variable flat top length and timing for the beam extraction.
INFN/LNS, Catania
The study of the Superconducting Cyclotron named SCENT300 [1] was carried out by the accelerator R&D team of LNS-INFN of Catania in collaboration with the University of Catania and supported by IBA (Belgium). The new design features concerning the magnetic properties of the machine and the last results about the beam dynamic are presented.
TRIUMF, Vancouver
The medical isotope Molybdenum-99 is presently used for 80-85% of all nuclear medicine procedures and is produced by irradiating highly enriched uranium U-235 targets in nuclear reactors. It has been proposed* that an electron linac be used for the production of 99Mo via photo-fission of a natural uranium target. The nominal linac parameters are 50 MeV electron energy, 100 mA beam current and 100% duty factor. This paper describes two possible superconducting RF accelerator design concepts based on the frequencies of 704 MHz and 1.3 GHz. We present design parameters, efficiency and reliability estimates, and comparisons between the two options. Finally, we describe how the proposed e-linac project at TRIUMF can be used for proof-of-principle demonstration and critical validation tests of the accelerator-based production of 99Mo.
*Making Medical Isotopes: Report of the Task Force on Alternatives for
Medical-Isotope Production (2008)
LAL, Orsay
CNAO Foundation, Milan
SOLEIL, Gif-sur-Yvette
NSC/KIPT, Kharkov
The goal of X-ray sources based on Compton back scattering processes is to develop a compact device, which could produce an intense flux of monochromatic X-rays. Compton back-scattering resuls from collisions between laser pulses and relativistic electron bunches. Due to the relative low value of the Compton cross section, a high charge electron beam, a low emittance and a high focusing at the interaction point are required for the electron beam. In addition, the X-ray flux is related to the characteristics of the electron beam, which are themselves dynamically affected by the Compton interaction. One possible configuration is to inject frequently into a storage ring with a low emittance linear accelerator without waiting for the synchrotron equilibrium. As a consequence, the optics should be designed taking into account the characteristics of the electron beam from the linear accelerator. The accelerator ring design for a 50 MeV electron beam, aiming at producing a flux higher than 1013 ph/s, will be presented.
NCC, Korea, Kyonggi
SNU, Seoul
An accelerator mass spectrometer (AMS) based on a compact cyclotron has been studied for biomedical uses. The system will have the mass resolving power of over 4000 to analyze a few different kinds of isotopes for tracing or chronometric dating. High transmission efficiency is a major design goal to compete with a Tandem AMS. A compact magnet with high stability, a saw tooth harmonic buncher, and flat-topping rf system are the components needed to achieve the goal. The results of design study for the AMS cyclotron and its injection line will be presented as well as the results of model tests for the cavity and the buncher.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
The J-PARC 3-GeV rapid cycling synchrotron (RCS) has been beam commissioned since October 2007 and it has been able to provide downstream facilities, the 50-GeV synchrotron (MR) and the Materials and Life Science Facility (MLF) with stable beam required from them. After beam deliver operation to the MR and MLF, while the priority ha s been given to their beam tuning, the RCS also continues further beam studies toward higher beam intensity. On September 18th, 2008, the RCS achieved the beam power of 210kW to beam dump with 25Hz. This presentation will concentrate itself on the outcome of the J-PARC RCS commissioning program, including the discussion on the issues of the high-power operation.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK/JAEA, Ibaraki-Ken
In the J-PARC RCS, we employ the longitudinal painting methods, the momentum offset injection method and applying the second harmonic RF voltages, to increase the bunching factor so that the space-charge tune shift is reduced. By the dual-harmonic operation with wide-band MA loaded cavities, in which each single cavity is driven by a superposition of the fundamental and the second harmonic RF signals, we can generate a large amplitude second harmonic RF voltage without extra cavities for the second harmonic RF. We present the results of the beam tests for the longitudinal painting in the J-PARC RCS. Also, we present the beam behavior at very high beam power.
KEK, Ibaraki
JAEA/LINAC, Ibaraki-ken
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
The output energy of J-PARC linac is planned to be upgraded from 190 MeV to 400 MeV by adding an ACS (Annular Coupled Structure linac) section. The ACS is a variety of coupled-cavity structure linac newly devised for former JHP (Japan Hadron Project), and its original beam dynamics design for J-PARC was presented in LINAC02 [M. Ikegami et. al., in Procs. of LINAC02, p. 629]. Extensive R&D studies have been conducted since then to establish the feasibility of ACS, where four ACS modules have been fabricated and successfully high-power tested. In parallel, the beam dynamics design of the ACS has been further optimized to reflect the experience obtained in the R&D studies and reduce the cost for mass production. In this paper, the revised beam dynamics design of the J-PARC ACS is presented with some simulation results with a particle simulation code.
NSCL, East Lansing, Michigan
An 8 GeV proton linac is being considered for the Fermilab accelerator complex. A design calls for five superconducting cavity types: three types of half-wave and two types of multi-cell elliptical structures. The elliptical cavity types have a frequency of 1.3 GHz with a beta = 0.81 and a beta = 1 and provide acceleration from 420 MeV to 8 GeV. An alternative concept would be to use an additional 1.3 GHz elliptical cavity type starting at 150 MeV. The alternative design may reduce project cost and risk. It would increase the technology overlap between Project X and the International Linear Collider. Preliminary simulations show the alternative linac layout has adequate longitudinal acceptance. This paper will discuss the beam dynamics studies for the alternative linac layout in comparison with the baseline layout.
ORNL, Oak Ridge, Tennessee
Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
The Spallation Neutron Source (SNS) is a second generation pulsed-neutron source and designed to provide a 1-GeV, 1.44-MW proton beam to a mercury target for neutron production. Since the initial commissioning of accelerator complex in 2006, the SNS has begun neutron production operation and beam power ramp-up has been in progress toward the design goal. Since the design beam power is almost an order of magnitude higher compared to existing neutron facilities, all subsystems of the SNS were designed and developed for substantial improvements compared to existing accelerators and some subsystems are first of a kind. Many performance and reliability aspects were unknown and unpredictable, for which it takes time to understand the systems as a whole and/or needs additional performance improvements. A power ramp-up plan has been revised based on the operation experiences and understandings of limits and limiting conditions through extensive studies with an emphasis on machine availability. In this paper the operational experiences of SNS Superconducting Linac (SCL), the power ramp-up status and plans will be presented including related subsystem issues.
Bilbao, Faculty of Science and Technology, Bilbao
ESS Bilbao, Bilbao
Elytt Energy, Madrid
Funding: ESS-Bilbao Consortium
A baseline design for the proton linear accelerator as proposed by the European Spallation Source-Bilbao bid to host the installation (ESS-B) is here described. The new machine concept incorporates advances which have been registered within high power accelerators during the last decade. The design of such a new accelerator layout heavily relies upon low-beta superconducting spoke resonators which are already under development.
BNL, Upton, Long Island, New York
CEA, Gif-sur-Yvette
ESS-S, Lund
Fermilab, Batavia
CERN, Geneva
Funding: ESS-S Scandinavia Consortium
The conceptual design of the European Spallation Source-Scandinavia (ESS-S) is presented. The accelerator system baseline draws heavily on state-of-the-art mature technologies that are being employed in the CERN Linac4 and SPL projects, although advances with spoke resonator and sputtered superconducting cavities are also being evaluated for reliable performance. Irradiation damage due to proton beam losses is a key issue for linac and target components. Their optimized design is performed from an engineering perspective, using the last updated versions of mechanical design codes which were already qualified for irradiated components. Finally, future upgrades of power and intensity of the proton linac are considered, including the design optimization of the Target Station (proton/neutron convertor), with the possibility of increasing the average pulsed power deposition up to 7.5 MW. All possible upgrades will be taken into account for the final design review, in the frame of the costs and constraints given with the site decision.
ORNL, Oak Ridge, Tennessee
Muons, Inc, Batavia
JLAB, Newport News, Virginia
Funding: Supported in part by USDOE Contract No. DE-AC05-84-ER-40150. Supported in part by USDOE Contract DE-AC05-00OR22725
The ORNL spallation neutron source (SNS) user facility requires a reliable, intense beams of protons. The technique of H- charge exchange injection into a storage ring or synchrotron has the potential to provide the needed beam currents, but it will be limited by intrinsic limitations of carbon and diamond stripping foils. A laser in combination with magnetic stripping has been used to demonstrate a new technique for high intensity proton injection, but several problems need to be solved before a practical system can be realized. Technology developed for use in Free Electron Lasers is being used to address the remaining challenges to practical implementation of laser controlled H- charge exchange injection for the SNS. These technical challenges include (1) operation in vacuum, (2) the control of the UV laser beam to synchronize with the H- beam and to shape the proton beam, (3) the control and stabilization of the Fabry-Perot resonator, and (4) protection of the mirrors from radiation.
JLAB, Newport News, Virginia
ODU, Norfolk, Virginia
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The CEBAF accelerator at Jefferson Lab has had, since first demonstration in 1996, the ability to deliver a 5-pass electron beam to experimental halls (A, B, and C) simultaneously. This capability was provided by a set of three, room temperature 499 MHz rf separators in the 5th pass beamline. The separator was two-rod, TEM mode type resonator, which has a high shunt impedance. The maximum rf power to deflect the 6 GeV beams was about 3.4kW. The 12 GeV baseline design does not preserve the capability of separating the 5th pass, 11 GeV beam for the 3 existing halls. Several options for restoring this capability, including extension of the present room temperature system or a new superconducting design in combination with magnetic systems, are under investigation and are presented.
Fermilab, Batavia
DESY, Hamburg
INFN/LASA, Segrate (MI)
CEA, Gif-sur-Yvette
Albert Einstein, Leibniz Universität, Hannover
With a view to the series production of one hundred, 12 m long XFEL 1.3 GHz cryomodules and their transportation from the assembly site at CEA Saclay (F) to the installation site at DESY Hamburg (D) a test transportation of a FLASH cryomodule has been performed, in the condition foreseen for the mass transportation. The present study examines the stresses induced on the module and verify the damping capabilities of the transport frame in order to minimize risk of damage to the most critical components. During the transportation, acceleration and vibration have been monitored as well as coupler antenna contacts and vacuum performances. This paper describes the analysis performed and compares those results to the data of a similar transportation study at Fermilab for the CM1 cryomodule.
Fermilab, Batavia
INFN/LASA, Segrate (MI)
Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy.
In an exchange of technology agreement, Deutsches Elektron-Synchrotron (DESY) Laboratory in Hamburg Germany has provided a 1.3 GHz cryomodule “kit” to Fermilab. The cryomodule components (qualified dressed cavities, cold mass parts, vacuum vessel, etc.) sent from Germany in pieces were assembled at Fermilab’s Cryomodule Assembly Facility (CAF). The cavity string was assembled at CAF-MP9 Class 10 cleanroom and then transported to CAF-ICB cold mass assembly area via a flatbed air ride truck. Finite Element Analysis (FEA) studies were implemented to define location of instrumentation for initial coldmass transport, providing modal frequencies and shapes. Subsequently, the fully assembled cryomodule CM1 was transported to the SRF Accelerator Test Facility at New Muon Lab (NML). Internal geophones (velocity sensors) were attached during the coldmass assembly for transport (warm) and operational (cold) measurements. A description of the isolation system that maintained alignment during transport and protected fragile components is provided. Shock and vibration measurement results of each transport and modal analysis are discussed.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy.
In an exchange of technology agreement, Fermilab has built and delivered a 3.9 GHz (3rd harmonic) cryomodule to Deutsches Elektron-Synchrotron (DESY) Laboratory to be installed in the TTF/FLASH beamline. Transport to Hamburg, Germany was completed via a combination of flatbed air ride truck and commercial aircraft, while minimizing transition or handling points. Initially, destructive testing of fragile components, transport and corresponding alignment stability studies were performed in order to assess the risk associated with transatlantic travel of a fully assembled cryomodule. Data logged tri-axial acceleration results of the transport with a comparison to the transport study predicted values are presented.
INFN-Napoli, Napoli
UCR, Riverside, California
Funding: World Wide Collaboration of a large fraction of the international agencies.
Muon ionization cooling provides the only practical solution to prepare high brilliance beams necessary for a neutrino factory or muon colliders. The muon ionization cooling experiment (MICE) is under development at the Rutherford Appleton Laboratory (UK). It comprises a dedicated beam line to generate a range of input emittance and momentum, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. A first measurement of emittance is performed in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in liquid hydrogen and RF acceleration. A second spectrometer identical to the first one and a particle identification system provide a measurement of the outgoing emittance. By April 2009 it is expected that the beam and first set of detectors will have been commissioned, and a first measurement of input beam emittance may be reported. Along with the plan of measurements of emittance and cooling that will follow in the second half of 2009 and in 2010.
INFN/LNF, Frascati (Roma)
STAAR/AWR Corporation, Mequon
SLAC, Menlo Park, California
CERN, Geneva
To suppress the vertical beam instability in the CTF3 Combiner Ring caused by vertical trapped modes in the rf deflectors, two new devices have been constructed. In the new structures special antennas absorb the power released by the beam to the modes. They have been realized in aluminium to reduce the costs and delivery time and have been successfully installed in the ring. In the paper we illustrate the electromagnetic design, the realization procedures, the rf measurement and high power test results.
ORNL, Oak Ridge, Tennessee
University of Tennessee, Knoxville, Tennessee
MIT Lincoln Laboratory, Boston MA
Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
Investigations of the rf properties of certain twisted waveguide structures show that they support favorable accelerating fields. This makes them potential candidates for accelerating cavities. Using the particle tracking code, ORBIT, We examine the beam - rf interaction in the twisted cavity structures to understand their beam transport and acceleration properties. The results will show the distinctive properties of these new structures for particle transport and acceleration, which have not been previously analyzed.
TEMF, TU Darmstadt, Darmstadt
DESY, Hamburg
The rf and wakefield transverse kicks resulting from the asymmetry of input and HOM couplers in the third harmonic module for the XFEL are investigated. The fundamental mode is computed using eigenvalue analysis. The short range wakefields in a string of cavities are simulated with the PBCI code. Using the simulation data, the transverse kick factors associated with the presence of cavity couplers are evaluated.
* P. Pierini, "Third Harmonic Superconducting Cavity Prototypes for the XFEL", LINAC08.
** T. Khabiboulline, "New HOM Coupler Design For 3.9 Ghz Superconducting Cavities At FNAL", PAC07.
CPI, Palo Alto, California
Funding: The authors would like to thank DESY for their support. In addition, we appreciate SLAC helping us out with test equipment.
CPI has designed and is currently in the process of building a prototype of a horizontally oriented multiple beam klystron (MBK) required to provide at least 10 MW peak rf output and 65% efficiency at 1300 MHz and 1.5% rf duty. The klystron was ordered by DESY for the European XFEL. In our design six off-axis electron beams go through seven ring resonators operating in the fundamental-mode. This ensures sufficient beam separation for longer cathode life while keeping the overall diameter of the device small. The MBK was designed using sate-of-the-art multi-dimensional design codes which showed that it was exceeding all performance requirements. First rf hot test data at reduced duty produced 11.2 MW peak saturated rf output and 74% efficiency, which was however accompanied by high beam interception. Initial optimization of the electromagnet resulted in a 70% reduction of the rf body current, but at the expense of rf output power, efficiency (down to 67%) and gain. The magnetic field balance has to be further optimized for low body current and high efficiency at all required operating conditions. Complete test data after optimization and tuning will be presented at the conference.
LBNL, Berkeley, California
Traditional rf processing systems have involved heterodyned rf processing based on mixing a Local Oscillator to up and down convert rf signals through a baseband I/Q or Mag/Phase processing channel. These systems were traditionally custom engineered for each accelerator application. Recent technical developments in rf processing and the development of sufficiently fast reprogrammable digital processing functions lead to development of general-purpose rf processing functions which can incorporate a mix of heterodyned and direct digital down/up-converted processing ("software radio"). This general-purpose approach allows one design of hardware to be applicable to many rf processing tasks, where the firmware and software in the programmable functions define the application. An example design, with applications to linac LLRF control loops and electro-optic timing reference stabilization is presented.
Fermilab, Batavia
Funding: FRA
Fermilab’s High Intensity Neutrino Source (HINS), the 325 MHz low energy section of Project X consists of an RFQ, 18 copper cavities and a section of superconducting spoke resonator cavities, all driven by a single 2.5 MW klystron. Each cavity has a high power ferrite vector modulator which provides individual RF power control. This paper proposes a scheme that optimizes RF drive and vector modulator control. The different gradients, acceleration phase angles, unloaded Q’s and beam loading are taken into account to optimize the cavities detuning angles, forward power, and loaded Q’s. This scheme makes an efficient use of the klystron’s high bandwidth ability to modulate the forward power, hence minimizing the burden on the high power vector modulator during the RF pulse. The proposed method is explained in details, a parameter sensitivity analysis is performed and the impact on the total power consumption for the RF station is calculated.
BARC, Trombay, Mumbai
Indian Institute of Technology Bombay, Mumbai
TIFR, Mumbai
As a first step towards development in digital domain, a computer model of a self excited loop (SEL) has been created using MATLAB/SIMULINK. The behaviour of a resonator and a power amplifier combination has been approximated using two first-order differential equations. The square of the amplitude of the RF field in the resonator acts as a driving force for the motion of mechanical modes of the resonator, which are individually represented as second order systems. A key element is the limiter, which has been modelled as a feedback loop, to achieve constant output amplitude. The model has been created in the I-Q domain for computational efficiency and close correspondence with actual implementation. To study the field stabilisation, proportional amplitude and phase feedback loops have been appended to the model of the SEL. In this paper we discuss the details of the model and results from simulation. Initial experimental results are also presented.
BNL, Upton, Long Island, New York
After the success of longitudinal stochastic cooling of bunched heavy ion beam in RHIC, transverse stochastic cooling was installed and commissioned with proton beam. The talk presents the status of this effort and gives an estimate, based on simulation, of the RHIC luminosity with stochastic cooling in all planes.
KEK, Ibaraki
Future accelerators require a high resolution beam profile monitor that measures the beam non-destructively and works at high beam intensity. Laser based beam monitors can be the solution. It uses a focused laser beam to scan the electron beam while detecting the Compton scattered photon. Accelerator Test Facility at KEK has been developing various types of Laser Wire monitors. CW laser wire with build-up optical cavity has been used to measure the small emittance beam at the damping ring. Pulsed laser wire has been developed to measure a small focused beam at the extraction line. Performance of these systems will be presented.
RISE, Tokyo
KEK, Ibaraki
Kyoto University, Kyoto
Funding: Work supported by a Grant-In-Aid for Creative Scientific Research of JSPS (KAKENHI 17GS0210) and a Grant-In-Aid for JSPS Fellows (19-5789)
We have been developing a pulsed-laser storage technique in a super-cavity for compact X-ray sources. The pulsed-laser super-cavity enables to make high peak power and small waist laser at the collision point with the electron beam. Recently, using 357 MHz mode-locked Nd:VAN laser pulses which stacked in a super-cavity scattered off a multi-bunch electron beam, we obtained multi-pulse X-rays through laser-Compton scattering. Detecting an X-ray pulse-by-pulse using a high-speed detector makes it possible to measure the 3-dimensional beam size with bunch-by-bunch scanning the laserwire target position and pulse timing. This technique provides not only the non-destructive beam profile monitoring but also the measuring of bunch length and/or bunch spacing shifting. In our multi-bunch electron linac, the bunch spacing narrowing due to the electron velocity difference in the train at the output of rf-gun cavity was observed. The principle of the 3-dimensional laserwire monitor and the experimental results of multi-bunch electron beam measurements will be presented at the conference.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
EMMA, the Electron Model with Many Applications, was originally conceived as a model of a GeV-scale muon accelerator. The non-scaling (NS) properties of resonance crossing, small apertures, parabolic ToF and serpentine acceleration are novel, unproven accelerator physics and require "proof of principle". EMMA has metamorphosed from a simple "demonstration" objective to a sophisticated instrument for accelerator physics investigation with operational demands far in excess of the muon application that lead to technological challenges in magnet design, rf optimisation, injection and extraction, and beam diagnostics. Machine components procured in 2008 will be installed February-May 2009 leading to full system tests June-August and commissioning with electrons beginning September 2009.
TRIUMF, Vancouver
DAE/VECC, Calcutta
A 0.5 megawatt electron linear accelerator is being designed at TRIUMF in support of its expanding rare isotope program, which targets nuclear structure and astrophysics studies as well as material science. The first stage of the project, a 25 MeV, 5 mA, cw linac matching the isotope production target power-handling capability in the next five-year plan, is planned to be completed in 2013. The injector cryomodule development, which is being fast tracked, is the subject of a scientific collaboration between TRIUMF and the VECC laboratory in Kolkata, India. The paper gives an overview of the accelerator design progress.
Imperial College of Science and Technology, London
Imperial College of Science and Technology, Department of Physics, London
Cockcroft Institute, Lancaster University, Lancaster
The proposed Muon Cooling System for the Neutrino Factory operates with high accelerating gradient in the presence of magnetic field. This can significantly increase the risk of RF breakdown. Field Emission is the most frequently encountered RF breakdown that occurs at sites with local electromagnetic field enhancement. Surface defects can be considered as possible emission sites. Upon Impact, generally the majority of electron’s energy is converted into stress and heat. In return, the damage inflicted can create additional emission sites. This paper presents the work under way, which aims to model certain physical phenomena during both emission and impact of electrons. The three-dimensional field profile of an 805 MHz pill-box cavity is modelled by Comsol Multuphysics. A tracking code written in-house is employed to track particles, providing sufficient data such as energy and speed at small time steps. This would allow the study of local heat transfer, applied surface stresses and secondary electron yield upon impact with the RF surface. In addition, the effects of externally applied magnetic field on electron’s behaviour are to be investigated.
JAEA/J-PARC, Tokai-mura
KEK, Ibaraki
KEK/JAEA, Ibaraki-Ken
J-PARC consists of a 181 MeV linac, a 3GeV Rapid Cycling Synchrotron (RCS) and a 50 GeV Synchrotron (MR). The RCS is designed to accelerate a high intensity proton beam. One of the key issues of the RCS RF system is how to achieve the very high accelerating field gradient of more than 20kV/m. This is impossible with conventional ferrite-loaded cavities. We reach this goal by the development of Magnetic Alloy (MA) core loaded RF cavities. We installed 10 RF cavities in the RCS tunnel on May 2007. The RCS beam commissioning was started on September 2007 and we successfully accelerated a proton beam up to 3GeV on October 2007. We also employed MA cores for MR RF cavities and use a cut core configuration to adjust the Q-value. The MR beam commissioning was started on May 2008. We didn't have any trouble caused by the MA cores during operation. We measured the impedance of the RF cavities several times at the shutdown periods. We show the results of impedance measurements. From these results, we can make an assumption about the core condition.
JAEA/J-PARC, Tokai-mura
KEK, Ibaraki
KEK/JAEA, Ibaraki-Ken
The J-PARC Rapid Cycling Synchrotron (RCS) uses broadband magnetic alloy loaded cavities to create the acceleration voltages needed for rapid cycling at 25 Hz rate. Besides the desired second harmonic of the acceleration frequency, which is employed in the painting process of RCS injection, also unwanted harmonics can be found at the acceleration gaps of the cavities. Here, the effect of the vector sums of undesired harmonics during the acceleration process is estimated.
LBNL, Berkeley, California
JLAB, Newport News, Virginia
UMiss, University, Mississippi
The international muon ionization cooling experiment (MICE) requires low frequency and normal conducting RF cavities to compensate for muon beams’ longitudinal energy lost in the MICE cooling channel. Eight 201-MHz normal conducting RF cavities with conventional beam irises terminate by large and thin beryllium windows are needed. The cavity design is based on a successful prototype cavity for the US MUCOOL program. The MICE RF cavity will be operated at 8-MV/m in a few Tesla magnetic fields with 1-ms pulse length and 1-Hz repetition rate. The cavity design, fabrication, post process plans and as well as integration to the MICE cooling channel will be discussed and presented in details.
University of Tennessee, Knoxville, Tennessee
ORNL RAD, Oak Ridge, Tennessee
ORNL, Oak Ridge, Tennessee
RF properties of twisted waveguide structures were investigated to show that slow-wave accelerating fields can be excited and used for acceleration of particle at various velocities lately. To build a practical accelerating cavity structure using the twisted waveguide, more development work was needed: cavity structure tuning, end wall effect of the structures, incorporating beam pipes and input power coupler, and HOM damping, etc. In this paper, the practical aspects of the designs to make more complete accelerating structures are discussed with the results of computer simulations.
Old Dominion University, Norfolk, Virginia
Muons, Inc, Batavia
Fermilab, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86350 Supported in part by USDOE STTR Grant DE-FG02-08ER86352 and in part by FRA DOE contract number DE-AC02-07CH11359
In earlier reports, microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments were used to investigate the mechanism of RF breakdown of tungsten, molybdenum, and beryllium electrode surfaces. Plots of remnants were consistent with the breakdown events being due to field emission, due to the quantum mechanical tunnelling of electrons through a barrier as described by Fowler and Nordheim. In the work described here, these studies have been extended to include tin, aluminium, and copper. Contamination of the surfaces, discovered after the experiments concluded, have cast some doubt on the proper qualities to assign to the metallic surfaces. However, two significant results are noted. First, the maximum stable RF gradient of contaminated copper electrodes is higher than for a clean surface. Second, the addition of as little as 0.01% of SF6 to the hydrogen gas increased the maximum stable gradient, which implies that models of RF breakdown in hydrogen gas will be important to the study of metallic breakdown
Old Dominion University, Norfolk, Virginia
LBNL, Berkeley, California
ANL, Argonne
Muons, Inc, Batavia
Fermilab, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86352 and FRA DOE contract number DE-AC02-07CH11359
Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual vacuum and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) and pressure barrier capable of operating both at high pressure and in vacuum been designed and built, and preliminary testing has been completed. A series of detailed experiments is planned at the Argonne Wakefield Accelerator.
Omega-P, Inc., New Haven, Connecticut
KEK, Ibaraki
Fermilab, Batavia
Measurements are reported for a one-third version of a L-band high-power ferroelectric phase shifter. The device is designed to allow fast adjustments of cavity coupling in an accelerator where microphonics, RF source fluctuations, or another uncontrolled fluctuations could cause undesired emittance growth. Experimental measurements of switching speed, phase shift and insertion loss vs. externally-applied voltage are presented. An average switching rate of 0.5 ns or better for each degree of RF phase has been observed.
OXFORDphysics, Oxford, Oxon
Imperial College of Science and Technology, Department of Physics, London
UMAN, Manchester
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Brunel University, Middlesex
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
JAI, Oxford
Cockcroft Institute, Lancaster University, Lancaster
Manchester University, Manchester
Gray Cancer Institute, Northwood, Middlesex
Funding: EP/E032869/1
AMELA (Particle Accelerator for MEdicaL Applications) is a newly developed fixed field accelerator, which has capability for rapid beam acceleration, which is interesting for practical applications such as charged particle therapy. PAMELA aims to design a particle therapy facility using Non-Scaling FFAG technology, with a target beam repetition rate of 1kHz, which is far beyond that of conventional synchrotron. To realize the repetition rate, the key component is rf acceleration system. The combination of a high field gradient and a high duty factor is a significant challenge. In this paper, options for the system and the status of their development are presented.
PSI, Villigen
INFN/LNF, Frascati (Roma)
RF deflectors are crucial diagnostic tools for bunch length and slice emittance measurements with sub-picosecond resolution. Their use is essential in commissioning and operation of VUV and X-ray FELs. The 250MeV FEL injector, under construction at PSI, will use two of them. The first one will be installed after the gun at low energy (~7MeV), the second one at the end of the Linac at high energy (250MeV). The first RF deflector consists of a single cell standing wave cavity working on the TM110 deflecting mode, and tuned at 2997.912 MHz (frequency of the linac structures). In this note we report the motivation of this measurement, beam dynamics and beam diagnostics considerations and the RF design and simulations of this cavity.
BINP SB RAS, Novosibirsk
RRC, Moscow
The project of upgraded RF System of Siberia-2 Electron Storage Ring / SR Source, Moscow, Russia, is presented. The upgraded RF system will allow to increase the total accelerating voltage up to 1.8MV and ensure operation of the storage ring with new superconducting wiggler at beam currents up to 0.3A. RF system operates at 181MHz. It consists of 3 single bi-metal cavities, 2 power amplifiers based on GU-101A tetrodes with output power of 200kW, power transmission lines and control system. Parameters of the upgraded RF system are given, the design of its main elements is shown.
SAMEER, Mumbai
Shunt impedance of an accelerating structure is an important parameter. It gives an idea of the power coupled to the beam. A 6 MeV to 15 MeV ‘S’ band standing wave side coupled linac structure is developed in SAMEER*. The measurement of the shunt impedance of the cavity is done using bead pull method. The shunt impedance is calculated after plotting the electric field profile. The calculation is done using a C code which first calculates the area of the plot and then uses appropriate variables to give the final value of the shunt impedance. The automation of the bead pull setup is planned and then the integration of calculation and automated setup. This paper describes the method used in the code and outlines the results of the measurement.
*R.Krishnan et.al. submitted in this conference.
SLAC, Menlo Park, California
Funding: Work supported by the DOE under contract DE-AC02-76SF00515
An L-band (1.3 GHz), normal-conducting, five-cell, standing-wave cavity that was built as a prototype capture accelerator for the ILC is being high-power processed at SLAC. The goal is to demonstrate stable operation at 15 MV/m with 1 msec, 5 Hz pulses and the cavity immersed in a 0.5 T solenoidal magnetic field. This paper summarizes the performance that was ultimately achieved and describes a novel analysis of the modal content of the stored energy in the cavity after a breakdown to determine on which iris it occurred.
SLAC, Menlo Park, California
Funding: Work supported by the DOE under contract DE-AC02-76SF00515
A new facility to clean, assemble, bake and rf process TTF3-style power couplers has been completed and is in operation at SLAC. This facility includes a class-10 cleanroom, bake station and an L-band source capable of producing up to 4 MW pulses. This paper describes the facility, test results from processing pairs of couplers that will be used in cryomodules at FNAL, and efforts to simplify the design and manufacturing of the couplers for large scale use at ILC. Also, tests of the couplers to explore their power limits for use in an FNAL superconducting proton linac are presented.
SLAC, Menlo Park, California
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
Funding: This work was supported by DOE contract No. DE-AC02-76SF00515 NERSC
The muon cooling cavity for Muon Collider works under strong external magnetic fields. It has been observed that this external magnetic field can enhance the multipacting activities and dark current heating. As part of a broad effort to optimize external magnetic field map and cavity shape for minimal dark current and multipacting, we use SLAC’s 3D parallel code Track3P to analyze the multipacting and dark current issues of the design. Track3P has been successfully used to predict multipacting phenomena in cavity and coupler designs. It provides unprecedented capabilities for simulating large-scale accelerator structure systems, including realistic 3D details and low turn-around times. In this paper, we present the comprehensive multipacting and dark current simulations for Muon Collider cavities.
SLAC, Menlo Park, California
Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515.
We present a concept for powering the main linacs of the International Linear Collider (ILC) by delivering high power RF from the surface via overmoded, low-loss waveguides at widely spaced intervals. The baseline design employs a two-tunnel layout, with klystrons and modulators evenly distributed along a service tunnel running parallel to the accelerator tunnel. This new idea eliminates the need for the service tunnel. It also brings most of the warm heat load to the surface, dramatically reducing the tunnel water cooling and HVAC requirements. In the envisioned configuration, groups of 70 klystrons and modulators are clustered in surface buildings every 2.4 km. Their outputs are combined into two half-meter diameter circular TE01 mode evacuated waveguides. These are directed via special bends through a deep shaft and along the tunnel, one upstream and one downstream. Each feeds approximately 1.2 km of linac with power tapped off in 10 MW portions at 38 m intervals. The power is extracted through a novel coaxial tapoff (CATO), after which the local distribution is as it would be from a klystron. This tapoff design is also employed in reverse for the initial combining.
ELETTRA, Basovizza
Funding: The work was supported in part by the Italian Ministry of University and Research under grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3
FERMI@Elettra is a seeded FEL user facility under construction at Sincrotrone Trieste, Italy. The linac is based on S-band normal conducting technology. It will use the accelerating sections of the original Elettra linac injector, seven sections received from CERN after LIL decommissioning and two additional sections to be constructed for a total number of 18 S-band accelerating structures. Installation of the machine is presently being carried on. This paper will provide a summary of the requirements of the different parts of the S-band RF system and of the options for a possible upgrade path both in energy and reliability. The ongoing activities on the main subassemblies, in particular regarding the tests and the installation work, are also presented.
ELETTRA, Basovizza
Funding: The work was supported in part by the Italian Ministry of University and Research under grant FIRB-RBAP045JF2 or grant FIRB-RBAP06AWK3 or grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3
The FERMI@ELETTRA project will use the existing ELETTRA linac. The linac includes seven accelerating sections, each section is a backward traveling (BTW) structure comprised of 162 nose re-entrant cavities coupled magnetically. Furthermore, there are specialized input and output cavities specifically designed to match the structure to the RF source and load. These BTW accelerating structures work on the 3pi/4 mode which was chosen to optimize the structure efficiency and to achieve a simple RF tuning setup. These accelerating sections are powered by a TH2132A 45 MW klystron providing a 4.5 microsecond rf pulse and are coupled to a Thomson CIDR. In this paper the 3pi/4 backward BTW structures are investigated and the results of the electromagnetic simulations are presented.
TRIUMF, Vancouver
In the TRIUMF cyclotron when a spark occurs it is necessary to shut off the RF drive and to initiate a RF restart procedure. It is also desirable to restore the full operational dee voltage as soon as possible in order to prevent thermal detuning of the resonant cavity. However, when the RF drive is shut off, the disappearance of Lorentz force on the resonator hot-arms causes the hot-arms to vibrate at their mechanical resonant frequency. When the RF field is being restored, the electromagnetic resonance is coupled to the mechanical resonance through the Lorentz force, and the amplitudes of both the mechanical vibration and the RF field depend on the timing when RF drive is re-applied. Computer simulations and experimental results will be presented to demonstrate that an optimum exists as to when to initiate the RF restart. With this optimal timing, the Lorentz force is used to damp the mechanical vibrations of the hot-arms. The reduction in hot-arm vibrations increases the probability of successful restarts as well as reduces the stress on the RF components.
USTC/PMPI, Hefei, Anhui
USTC/NSRL, Hefei, Anhui
Funding: "Collinear Load for Accelerators and R&D on High Power Microwave Absorbed Material" No.10775128 From National Natural Science Foundation of China
Thermal deformation caused by Non-uniform temperature distribution in disk-loaded waveguide will affect the resonant frequency of LINAC deeply. Formerly, researchers evaluated it by experiments or experience and gave their conclusion roughly and linearly. A new approach of integration of multi-disciplinary is adopted to study the relationship more accurately. After loading the loss RF power on the accelerator tube wall, the thermal deformation is calculated in software I-DEAS, and a deformed finite element model is obtained. Then nodes on inner surfaces of the cavities were extracted and sort by a customized program. According to these nodes, a new solid model is reconstructed with a self developed 3D reconstruction technology in ANSYS. B-Spline interpolation technique is used to fit a group of curves first, and then to reconstruct NURBS surfaces. The final reconstructed deformed solid model, obtained by closing the surfaces, can be exported in IGES format which is used to recalculate the resonant frequency in Microwave Studio again. The error of the reconstruction can be controlled within 3 micrometers. The resonant frequency change of every cavity can be accurately calculated.
Parietti L, etc., Thermal structural analysis and frequency shift **
Zhou, Zu-Sheng,etc. Thermal structural analysis and test **
IIT, Chicago, Illinois
Superconducting RF cavities are made of a thin metal shell (typically Niobium) with liquid Helium around it housed within another metal vessel. This geometry is effectively a Cerenkov radiator between two mirrors. Electrons stripped from the inner surface due to field emission can get accelerated by the electric field inside the cavity, punch through the cavity wall and still have enough energy to be faster than light in He. Detection of Cerenkov light generated by the electrons through an optical port integrated into the vessel can serve as a very sensitive diagnostic for field emission in cavity R&D and production as well as in operating superconducting linear accelerators. We report on simulation results for calculating the effective light yield in such a system to establish the feasibility of the technique.
IPN, Orsay
Funding: EURISOL Project
The development of RF power couplers for superconducting low-beta SPOKE cavities, performed at Nuclear Physics Institute in Orsay in the framework of the EURISOL Design Study, has led to the design of a 20 kW RF power coaxial coupler showing very good RF performances and the implementation of a test stand to condition two of these couplers at 20 kW CW power in the traveling wave mode at 352,2 MHz by using a half-wave resonant cavity. Composed by a ceramic disk, the coaxial power coupler developed shows on one hand a very good 50 ohms matching on a large bandwidth like 760 MHz, after an electromagnetic optimisation of the window area, and on the other hand a simplified design with regard to the classic coaxial couplers. Characteristics of the power coupler and the test stand will be described, and the low RF power test of the coaxial window and the conditioning at high RF power of two couplers will be presented.
INFN/LASA, Segrate (MI)
DESY, Hamburg
Cavity tuners are needed to precisely tune the resonant frequency of TESLA SC cavities for European XFEL linac. Although several units of the currently used device, originally designed at Saclay for TTF and then developed at DESY, have been manufactured and tested so far, a permanent installation like the XFEL poses higher requirements in terms of reliability and reproducibility. XFEL indeed requires about {10}00 tuners to be produced in a relatively short time and then to simultaneously work in cryogenic environment, each of them being equipped with a stepper motor driving unit and two piezoelectric actuators. In this frame, an acceptance test procedure, here presented, has been studied, its main goal being the cross-check of issues affecting reliability: installation, mechanical coupling of active elements to cavity, motor and fast actuators functionality. An electronic equipment has been developed for driving signals, sensors and data management, specifically aiming toward an automatic and user-friendly routine in view of a large scale application. The procedure has been then applied for calibration purposes of a sample cavity assembly, the experimental results are also presented.
INFN/LASA, Segrate (MI)
BESSY GmbH, Berlin
An extensive validation activity has been conducted since year 2007 for the coaxial Blade Tuner for TESLA SC cavities. During this activity, performances and limits of prototype models have been deeply investigated through detailed test sessions inside CHECHIA (DESY) and HoBiCaT (BESSY) horizontal cryostats as well as F.E. modeling and analyses. The result is an improved design for the Blade Tuner, specifically meant to satisfy the incoming ILC-level performance requirements, fulfill pressure vessels regulations and keep Ti / S.S. material compatibility. Recent Blade Tuner activities and results will be presented in this paper in view of the installation of 8 units in the second cryomodule of ILCTA facility at Fermilab, and also of our contribution to both incoming S1-Global (KEK) and ILC-HiGrade projects. The manufacturing process of the first set of 8 tuners, from production to room temperature validation for the whole series, will be also reviewed. Then results will be shown from the cold tests recently performed, where special effort has been made in evaluating the accuracy and repeatability of fast and slow tuning action at few Hz range.
INFN/LASA, Segrate (MI)
DESY, Hamburg
Three superconducting 3.9 GHz cavity prototypes have been fabricated for the XFEL linac injector, with minor modifications to the rf structures built by FNAL for the FLASH linac. This paper describes the production and preparation experience, the initial measurements, the plans for the XFEL series production and the cryogenic test infrastructure under preparation at INFN Milano.
INFN/LASA, Segrate (MI)
Funding: Work partially supported by the FP6 EU programs EUROTRANS (Contract FI6KW-CT-2004-516520) and CARE/HIPPI (Contract RII3-CT-2003-506395).
The two TRASCO elliptical superconducting cavities for low energy (100-200 MeV) protons have been completed with equipping them with cold tuner and a magnetic shield internal to the helium tank. One of the two structures is now available for significative tests of Lorentz Force Detuning control of these low beta structures under pulsed conditions for future high intensity linac programs, as SPL or the ESS. The second structure will be integrated in a single cavity cryomodule under fabrication for the prototypical activities of the EUROTRANS program for nuclear waste trasmutation in accelerator driven systems.
KAERI, Daejon
Funding: This work is supported by the Ministry of Education, Science and Technology of Korea.
A superconducting radio frequency (SRF) cavity with a geometrical beta of 0.42 has been designed to accelerate a proton beam after 100 MeV at 700 MHz for an extended project of Proton Engineering Frontier Project (PEFP). In order to confirm the RF and mechanical properties of the cavity, and to produce documentation for a procurement and quality control for an industrial manufacture of the cavities, two prototype copper cavities have been produced, tuned and tested. In this paper, the copper cavity’s production, tuning and testing are introduced. The testing results show that the low-beta cavity and its tuning system can work as we design.
LANL, Los Alamos, New Mexico
Funding: DTRA
A temperature mapping system with 4608 100-ohm Allen-Bradley resistors has been built and tested at LANL. With this temperature mapping system we were able to locate lossy regions in the 1.3 GHz 9-cell SRF cavity due to field emission and direct heating. The results of the temperature mapping have been correlated with the inside surface inspection of the cavity and will be shown together with Q-E curves. A brief description of the mapping system and improvements that have been made in the recent months will also be mentioned in the paper.
LANL, Los Alamos, New Mexico
JLAB, Newport News, Virginia
Funding: DTRA
805 MHz elliptical SRF cavities have been used for SNS as the first application for protons. At LANL, an R&D started to explore a capability of getting high-gradient cavities (40-50 MV/m) at this frequency for the future applications such as proton and muon based interrogation testing facility added to the LANSCE accelerator and a power upgrade of the LANSCE accelerator for the fission and fusion material test station. Optimized cell designs for “standard”, “low-loss” and “re-entrant” shapes, cavity test results for “standard” single-cell cavities with temperature mapping as well as surface inspection results will be presented.
LANL, Los Alamos, New Mexico
ORNL, Oak Ridge, Tennessee
SLAC, Menlo Park, California
Penn State University, University Park, Pennsylvania
Funding: DTRA
We are currently testing the effect of coating Nb with a thin layer of another superconductor such as NbN and MgB2. Gurevich’s theory of multi-layered coating predicts an enhancement of the critical magnetic field, giving us hope to increase the achievable accelerating gradient to above 50 MV/m in elliptical cavities. CW test results of 3 GHz Nb single-cell cavities coated with ~100 nm NbN at LANL and 11.4 GHz <1 μs high-power pulsed test results of 2” Nb disk samples coated with ~100 nm MgB2 will be presented.
NSCL, East Lansing, Michigan
A medium-velocity half wave resonator has been designed and prototyped at the National Superconducting Cyclotron Laboratory for use in a heavy ion linac. The cavity is designed to provide 3.7 MV of accelerating voltage at an optimum beta = v/c = 0.53, with peak surface electric and magnetic fields of 32.5 MV/m and 79 mT, respectively. The resonant frequency is 322 MHz. The cavity was designed to reduce sensitivity to bath pressure fluctuations while maintaining a structure that can be easily fabricated, cleaned, and tuned. Deep draw forming dies and a copper cavity prototype were fabricated to confirm tolerances and formability. A prototype tuner was built; the helium vessel and power coupler have been designed. Measurements were performed to confirm finite element predictions for the mechanical modes, bath pressure sensitivity, tuner stiffness, and tuning range.
MHI, Kobe
We report on the activities and achievements at MHI about cavity fabrication for ILC. Some new procedures of cavity fabrication for industrialization are reported.
BNL, Upton, Long Island, New York
Niowave, Inc., Lansing, Michigan
MHI, Kobe
NSLS-II is a new ultra-bright 3GeV 3rd generation synchrotron radiation light source. The performance goals require operation with a beam current of 500mA and a bunch current of at least 0.5mA. Ion clearing gaps are required to suppress ion effects on the beam. The natural bunch length of 3mm is planned to be lengthened by means of a third harmonic cavity in order increase the Touschek limited lifetime. After an extensive investigation of different cavity geometries a passive, superconducting 2-cell cavity has been selected for prototyping. The cavity is HOM damped with ferrite absorbers on the beam-pipes. The 2-cell cavity simplifies the tuner design as compared to two independent cells. Tradeoffs between the damping of the higher order modes, thermal isolation associated with the large beam tubes and overall cavity length are described. A copper prototype has been constructed and measurements of fundamental and higher order modes will be compared to calculated values.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
Funding: Supported in part by USDOE SBIR Grant DE-FG02-08ER85171
High-current RF cavities that are needed for many accelerator applications are often limited by the power transmission capability of the pressure barriers (windows) that separate the cavity from the power source. Most efforts to improve RF window design have focused on alumina ceramic, the most popular historical choice, and have not taken advantage of new materials. Alternative window materials have been investigated using a novel Merit Factor comparison and likely candidates have been tested for the material properties which will enable construction in the self-matched window configuration. Window assemblies have also been modeled and fabricated using compressed window techniques which have proven to increase the power handling capability of waveguide windows. Candidate materials have been chosen to be used in fabricating a window for high power testing at Thomas Jefferson National Accelerator Facility.
Muons, Inc, Batavia
CLASSE, Ithaca, New York
Cornell University, Ithaca, New York
Funding: Supported in part by USDOE Contract. DE-AC05-84-ER-40150
Superconducting HOM-damped (higher-order-mode-damped) RF systems are needed for present and future storage ring and linac applications. Superconducting RF (SRF) systems typically contain unwanted frequencies or higher order modes (HOM) that must be absorbed by ferrite and other lossy ceramic-like materials that are brazed to substrates mechanically attached to the drift tubes adjacent to the SRF cavity. These HOM loads must be thermally and mechanically robust and must have the required broadband microwave loss characteristics, but the ferrites and their attachments are weak under tensile stresses and thermal stresses and tend to crack. A HOM absorber with improved materials and design will be developed for high-gradient 750 MHz superconducting cavity systems. RF system designs will be numerically modeled to determine the optimum ferrite load required to meet the broadband loss specifications. Several techniques for attaching ferrites to the metal substrates will be studied, including full compression rings and nearly-stress-free ferrite assemblies. Prototype structures will be fabricated and tested for mechanical strength.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
Funding: Supported in part by DOE SBIR grant DE-FG02-08ER85171 Supported in part by USDOE Contract DE-AC05-84-ER-40150
There are over 35 coupler designs for SRF cavities ranging in frequency from 325 to 1500 MHz. Two-thirds of these designs are coaxial couplers using disk or cylindrical ceramics in various combinations and configurations. While it is well known that dielectric losses go down by several orders of magnitude at cryogenic temperatures, it not well known that the thermal conductivity also goes down, and it is the ratio of thermal conductivity to loss tangent (SRF ceramic Quality Factor) and ceramic volume which will determine the heat load of any given design. We describe a novel robust co-axial SRF coupler design which uses compressed window technology. This technology will allow the use of highly thermally conductive materials for cryogenic windows. The mechanical designs will fit into standard-sized ConFlat® flanges for ease of assembly. Two windows will be used in a coaxial line. The distance between the windows is adjusted to cancel their reflections so that the same window can be used in many different applications at various frequencies.
PKU/IHIP, Beijing
Funding: Supported by National Basic Research Program(No. 2002CB713600) and NSFC(No. 10775010).
The 3.5-cell cavity for the PKU DCSC photoinjector requires the main coupler and the pickup be on the same side of the cavity, which will cause crosstalk between them. At room temperature, serious distortion of the RF response is caused. This paper applies a clear understanding of the RF signal; numerical and experimental study shows that the crosstalk will be negligible in superconducting (SC) status. Furthermore, a method to calculater resonant frequency and loaded quality factor from the crosstalk signal is provided
SLAC, Menlo Park, California
CERN, Geneva
KEK, Ibaraki
Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and used resources of NERSC supported by DOE Contract No. DE-AC02-05CH11231, and of NCCS supported by DOE Contract No. DE-AC05-00OR22725.
Normal conducting accelerator structures such as the X-Band NLC structures and the CLIC structures have been found to suffer damage due to RF breakdown and/or dark current when processed to high gradients. Improved understanding of these issues is desirable for the development of structure designs and processing techniques that improve the structure high gradient performance. While vigorous experimental efforts have been put forward to explore the gradient parameter space via high power testing, comprehensive numerical multipacting and dark current simulations would complement measurements by providing an effective probe for observing interior quantities. In this paper, we present studies of multipacting, dark current, and the associated surface heating in high gradient accelerator structures using the parallel finite element simulation code Track3P. Comparisons with the high power test of the CLIC accelerator structures will be presented.
SLAC, Menlo Park, California
Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and used resources of NERSC supported by DOE Contract No. DE-AC02-05CH11231, and of NCCS supported by DOE Contract No. DE-AC05-00OR22725.
Crab cavities are proposed for the LHC upgrade to improve the luminosity. In the local crabbing scheme, the crab cavities are located close to the interaction region and the transverse separation between the two beam lines at the crab cavity location can only accommodate an 800-MHz cavity of the conventional elliptical shape. Thus the baseline crab cavity design for the LHC upgrade is focused on the 800-MHz elliptical cavity shape although a lower frequency cavity is preferable due to the long bunch length. In this paper, we present a compact 400-MHz design as an alternative to the 800-MHz baseline design. The compact design is of a half-wave resonator (HWR) shape that has a small transverse dimension and can fit into the available space in the local crabbing scheme. The optimization of the HWR cavity shape and the couplers for the HOM, LOM, and SOM damping will be presented.
SLAC, Menlo Park, California
Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and used resources of NERSC supported by DOE Contract No. DE-AC02-05CH11231, and of NCCS supported by DOE Contract No. DE-AC05-00OR22725.
In this paper, we present a 800MHz crab cavity conceptual design for LHC upgrade, including the cell shape optimization, and LOM, SOM, HOM and input coupler design. The compact coax-to-coax coupler scheme is proposed to couple to the LOM and SOM modes which can provide strong coupling to the LOM and SOM modes. HOM coupler design uses a two-stub antenna with a notch filter to couple to the HOM modes in the horizontal plane and reject the operating mode at 800MHz. All the damping results for the LOM/SOM/HOM modes satisfy their damping requirements. The multipacting in cell and couplers is simulated as well. And the issue of the cross-coupling between the input coupler and LOM/SOM couplers due to cavity asymmetry is addressed. The power coming out of the LOM/SOM/HOM couplers are estimated. All the simulations are carried out using SLAC developed parallel EM simulation codes Omega3P, S3P and Track3P.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Cockcroft Institute, Lancaster University, Lancaster
The ILC crab cavities require very tight phase control in order to operate within the ILC parameters. In order to verify that the phase control system met the design tolerances, two single-cell niobium 3.9GHz superconducting dipole-mode cavities were tested in a liquid helium cryostat. The preparation of the cavities, design of the testing apparatus and performance of the phase control system are described in this paper.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
CLASSE, Ithaca, New York
FZD, Dresden
STFC/DL, Daresbury, Warrington, Cheshire
LBNL, Berkeley, California
Stanford University, Stanford, California
DESY, Hamburg
STFC/DL/SRD, Daresbury, Warrington, Cheshire
The collaborative development of an optimised cavity/cryomodule solution for application on ERL facilities, has now progressed to final assembly and testing of the cavity string components and their subsequent cryomodule integration. This paper outlines the verification of the various cryomodule sub-components and details the processes utilised for final cavity string integration. The paper also describes the modifications needed to facilitate this new cryomodule installation and ultimate operation on the ALICE facility at Daresbury Laboratory.
SINAP, Shanghai
SSRF, Shanghai
RF system for SSRF (Shanghai Synchrotron Radiation Facility) Storage Ring consists of three RF stations, each of which has a klystron, one superconducting RF module and its low level RF feedback control. A 300kW klystron will feed the RF power to the superconducting cavity via a circulator and waveguides. Three CESR type 499.654MHz superconducting modules with tuning range ±150kHz are now in operation. A digitalized I/Q technology based on FPGA is adopted in its low level control. The commissioning and the performance of whole RF system will be described in details in this paper.
TRIUMF, Vancouver
An energy upgrade in the Radioactive Ion Beam (RIB) facility at ISAC-II will see the installation of 20MV of superconducting heavy ion linac. The addition includes twenty beta=11% bulk niobium quarter wave cavities housed in three cryomodules with six cavities in the first two and eight cavities in the last. Each cavity is specified to add 1MV in accelerating potential corresponding to peak surface fields of ~30MV/m. Transverse focusing is achieved with a 9T superconducting solenoid inside each cryomodule. The first module in the expansion has now been assembled and tested. Developments include a new ball screw tuner, locally produced cavities, modified coupler design and LN2 cryogenic circuits. The new developments are described and the results of the first cold tests are presented.
JLAB, Newport News, Virginia
ODU, Norfolk, Virginia
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
A new concept for a deflecting and crabbing rf structure based on half-wave resonant lines was introduced recently*. It offers significant advantages to existing designs and, because of it compactness, allows low frequency operation. This concept has been further refined and optimized for superconducting implementation. Results of this optimization and application to a 400 MHz crabbing cavity and a 499 MHz deflecting cavity are presented.
*A New TEM-Type Deflecting and Crabbing RF Structure, J. R. Delayen and H. Wang, Proc. LINAC08
JLAB, Newport News, Virginia
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
For the planned CEBAF upgrade ten new cryomodules are required to increase the beam energy to the envisaged 12 GeV. Extensive cavity and cryomodule R&D has been done previously, including the installation of a new cryomodule dubbed “Renascence” in CEBAFs north linac in 2007. It houses both seven-cell low loss and high gradient type of cavities thereby serving as a testbed to address and cope with crucial technological challenges. Based on this experience a final iteration on the upgrade cavity has been performed to improve various aspects of HOM-damping and thermal stability. Two such cavities have been produced and qualified. A thorough cavity HOM-survey has been performed to verify the integrity of the cavities and to guarantee the impedance requirements of each crucial HOM. This paper details the results of HOM-surveys performed for the first two upgrade style low loss cavities tested both individually in a vertical Dewar and horizontally in a dedicated cavity pair cryomodule. The safety margin to the worst beam break-up scenario at 12 GeV has been concluded.
JLAB, Newport News, Virginia
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The great majority of experience in niobium SRF cavity processing at Jefferson Lab is with BCP etching. This has been used on CEBAF cavities and others totaling over 500 in number. With improved process quality control, field emission is now largely controlled and other factors limit performance. All of the prototype cavities developed for the 12 GeV upgrade, although meeting minimum requirements, have demonstrated a Q-drop in the 17 23 MV/m range that is not remedied by 120 C bake. Most of these cavities received >250 micron removal by BCP etch. Three of these cavities are being electropolished using the protocol under development within ILC R&D activities. The first such cavity was transformed from Q = 3 ·1010 at 17 MV/m to quench from 1010 at 35 MV/m. The details of this and two subsequent electropolished JLab 7-cell cavities will be reported.
JLAB, Newport News, Virginia
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Recent global interest in high duty factor or CW superconducting linacs with high average beam power highlights the need for robust and reliable SRF structures capable of delivering high average RF power to the beam with moderate HOM damping, low interception of halo and good efficiency. Potential applications include proton or H- drivers for spallation neutron sources, neutrino physics, waste transmutation, subcritical reactors, and high-intensity high-energy physics experiments. We describe a family of SRF cavities with a range of Betas capable of transporting beam currents in excess of 10 mA CW with large irises for minimal interception of halo and HOM and power couplers capable of supporting high average power operation. Goals include an efficient cell shape, high packing factor for efficient real-estate gradient and strong HOM damping to ensure stable beam operation. Designs are being developed for low-frequency (e.g. 650-975 MHz), but can easily be scaled to high-frequency (e.g. 1.3-1.5 GHz), depending on the application. We present the results of conceptual design studies, simulations and prototype measurements.
JLAB, Newport News, Virginia
The College of William and Mary, Williamsburg
North Carolina State University, Raleigh, North Carolina
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
As SRF cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on performance limitations. Micro-and nano-roughness are implicated in direct geometrical field enhancements and complications of the composition of the 50 nm surface layer in which the super-currents flow. Interior surface etching (BCP/EP) to remove mechanical damage leaves surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely-used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is being used to distinguish the scale-dependent smoothing effects. The topographical evolution of the varied starting state Nb surface (CBP/ EBW) as a function of applied etching, polishing steps and conditions is reported, resulting in a novel qualitative and quantitative description of Nb surface topography.
JLAB, Newport News, Virginia
The College of William and Mary, Williamsburg
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Future accelerators require unprecedented cavity performance, which is strongly influenced by interior surface nanosmoothness. Electropolishing is the technique of choice to be developed for high-field superconducting radiofrequency cavities. Electrochemical impedance spectroscopy (EIS) and related techniques point to the electropolishing mechanism of Nb in a sulfuric and hydrofluoric acid electrolyte of controlled by a compact surface salt film under F- diffusion-limited mass transport control. These and other findings are currently guiding a systematic characterization to form the basis for cavity process optimization, such as flowrate, electrolyte composition and temperature. This integrated analysis is expected to provide optimum EP parameter sets for a controlled, reproducible and uniform surface leveling for Nb SRF cavities.
JLAB, Newport News, Virginia
ANL, Argonne
Funding: This manuscript has been authored by Jefferson Science Associates, LLC and by UChicago Argonne, LLC under U.S. DOE Contract numbers DE-AC05-06OR23177 and DE-AC02-06CH11357.
After design optimization of a squashed elliptical single-cell crab cavity at 2.8 GHz, a copper prototype has been bench measured in order to determine its rf properties and the effectiveness of waveguide damping of parasitic modes, especially the low-order mode (LOM)*. We also present detailed results of the RF cold test at 2K on niobium single-cell and two-cell prototype cavities operating either in the zero or pi mode. Further progress will be discussed on the design of high-order mode (HOM) waveguide damping, the analysis of the Lorenz force detuning simulations by ANSYS, and the prototype of on-cell damping in which a waveguide port is attached directly on the cavity’s long equator. Details of LOM/HOM impedance calculations and experimental bench measurements will be reported and compared to strict requirements for satisfying the APS impedance budget.
*J. Shi et. al., “Superconducting RF Deflecting Cavity Design and Prototype for Short X-ray Pulse Generation”, EPAC 2008, paper MOPP155.
JLAB, Newport News, Virginia
CEA, Gif-sur-Yvette
PKU/IHIP, Beijing
ORNL, Oak Ridge, Tennessee
Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A new surface treatment technique for niobium (Nb) Superconducting Radio Frequency (SRF) cavities called Buffered Electropolishing (BEP) has been developed at JLab. It was found that BEP could produce the smoothest surface finish on Nb samples ever reported in the literature. Experimental results revealed that the Nb removal rate of BEP could reach as high as 4.67 μm/min. This is significantly faster* than that of the conventional electropolishing technique employing an acid mixture of HF and H2SO4. An investigation is underway to determine the optimum values for all relevant BEP parameters so that the high quality of surface finish achieved on samples can be realized within the geometry of an elliptical RF cavity. Toward this end, single cell Nb cavities are being electropolished by BEP at both CEA-Saclay and JLAB. These cavities will be RF tested and the results will be reported through this presentation.
*Xiangyang Lu et al, to be published.
JLAB, Newport News, Virginia
The College of William and Mary, Williamsburg
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Much remains to be learned regarding the details of SRF performance effects with material variation, including niobium treated in different ways, and different bulk/thin film materials that are fabricated under different conditions. A facility that can measure small samples’ RF properties in a range of 0~180mT magnetic field and 2~20k temperature is necessary in order to answer this question. The Jefferson Lab surface impedance characterization (SIC) system has been designed to attempt to meet this requirement. The SIC system uses a sapphire-loaded cylindrical Nb cavity at 7.5GHz with 50mm diameter flat sample placed on a non-contacting end plate and a calorimetric technique to directly measure the rf dissipation in the sample in response to known rf fields over ~1 cm2. We report on the commissioning of this system and its first uses for characterizing materials. Preliminary tests with Nb thin film sample sputtered on Cu substrate, and bulk Nb sample have been done at low field. The presently available hardware is expected to enable tests up to 20 mT peak magnetic field on the sample CW. Paths to higher field tests have been identified.
JLAB, Newport News, Virginia
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
SRF cavities are observed to be limited by non-linear localized effects. The variation of local material parameters between "hot" and "cold" spots is thus of intense interest. Such locations were identified in a BCP etched large-grain single-cell cavity and removed for examination by high resolution electron microscopy (SEM), electron-back scattering diffraction microscopy (EBSD), and scanning Auger electron spectroscopy (SAM). Pits with clear crystal facets were observed on both "Hotspot" and "Coldspot" specimens. The pits were found in-grain and on "Y"-shaped junction of three crystals. They are interpreted as etch pits induced by surface crystal defects (e.g., dislocations). All "Coldspots" examined had obvious low density of etching pits or very shallow tri-crystal boundary junction. EBSD revealed crystal structure surrounding the pits via crystal phase orientation mapping. This study suggests a mechanism by which BCP etching creates pits on large-grain Nb cavity surfaces and sharp-edged topography in fine-grain Nb. Field enhancements at very deep, sharp and densely populated etching pits may then cause distributed hotspots and limit cavity performance.
University of Pennsylvania, Philadelphia, Pennsylvania
TRIUMF, Vancouver
The quality factor of superconducting radio-frequency cavities typically degrades with increasing field at moderate gradients before the on-set of field emission. The origin of the so called medium field Q-slope is not fully described and understanding it would be important in order to develop a cavity design or treatment which minimizes this effect, allowing us to produce cavities with reduced cryogenic losses. This paper will present an analysis of the medium field Q-slope data measured on cavities at different frequencies treated with buffered chemical polishing (BCP) at TRIUMF. The data is compared with existing models and agreements-discrepancies will be highlighted.
ASCo, Clayton, Victoria
RF cavities are routinely detuned slightly from resonance to maintain Robinson stability of the beam as beam loading increases. Detuning the cavities results in a reduction of the overall energy efficiency of the RF and can waste many MW hours of energy per year. It is therefore desirable to only detune as much as required by the beam loading to maintain stability. A new system for monitoring the load impedance of the Storage Ring RF cavities has been developed at the Australian Synchrotron. The system utilises the Analogue devices AD8302 chip to monitor the load impedance of the Cavities and allow for more efficient detuning of the system. An overview and commissioning results of this system will be presented.
BARC, Trombay, Mumbai
Indian Institute of Technology Bombay, Mumbai
CERN, Geneva
An RF system model has been created for the CERN Linac2 Tanks. RF systems in this linac have both single and double feed architectures. The main elements of these systems are: RF power amplifier, main resonator, feed-line and the amplitude and phase feedback loops. The model of the composite system is derived by suitably concatenating the models of these individual sub-systems. For computational efficiency the modeling has been carried out in the base band. The signals are expressed in in-phase - quadrature domain, where the response of the resonator is expressed using two linear differential equations, making it valid for large signal conditions. MATLAB/SIMULINK has been used for creating the model. The model has been found useful in predicting the system behaviour, especially during the transients. In the paper we present the details of the model, highlighting the methodology, which could be easily extended to multiple feed RF systems.
BNL, Upton, Long Island, New York
Funding: US DOE
The National Synchrotron Light Source-II (NSLS-II) is a new ultra-bright 3GeV 3rd generation synchrotron radiation light source. The performance goals require operation with a beam current of 500mA and a bunch current of at least 0.5mA. The position and timing specifications of the ultra-bright photon beam imposes a set of stringent requirements on the radio Frequency (RF) control, among which, for example, is the 0.14 degree phase stability, and the flexibility of handling varying beam conditions. To meet these requirements, a digital implementation of the LLRF is chosen in order to be able to take the advantage of the power of precision signal processing and control that only DSP technology can provide. The initial design of NSLS II LLRF control solution is comprised of a FPGA-based basic field controller, a dual ASIC DSP co-processor directly coupled to the FPGA controller, as well as a local CPU which monitors the operation, stores the data, and facilitates the tests and development. The prototype of the basic FPGA field controller hardware has been designed. The first sample has been fabricated, and is currently being tested.
BNL, Upton, Long Island, New York
Funding: Work performed under contract number 126615 for Brookhaven Science Associates, LLC.
NSLS-II is a new ultra-bright 3GeV 3rd generation synchrotron radiation light source. The performance goals require operation with a beam current of 500mA and a bunch current of at least 0.5mA. The position and timing specifications of the photon beam place tolerances on the phase stability of the RF cavity fields of less than 0.15 degrees jitter. This study develops computational methods for the construction of LQG controllers for discrete-time models of single-cavity rf systems coupled to rigid-bunch beams able to meet this tolerance. It uses Matlab’s control-systems toolbox and Simulink to synthesize the LQG controller; establish resolutions of state variables, ADCs, DACs, and matrix coefficients that, in a fixed-point controller provide essentially undiminished performance; simulate closed-loop performance; and assess sensitivity to variations of the model. This machinery is applied to NSLS-II-, CLS-, and NSLS VUV-ring models showing exceptional noise suppression and bandwidth. Thoughts are given on the validation and tuning of the rf model by machine measurements, DSP implementations, and future work.
CIAE, Beijing
In the commissioning phase of CRM cyclotron, the RF cavity resonance frequency changes rapidly due to cavity thermal instability and electronics interference inside tuning loop. To solve the later issue, a set of cavity tuning control electronics has been re-designed, fabricated and tested in 2008. The new tuning control electronics and related experimental results will be described in this paper. A wide dynamic range phase detector with double balanced mixer were selected to detect the cavity detuning angle by comparing the phase difference between the cavity pickup signal and cavity driven signal. One analogue P.I. controller was utilized for loop regulation, taking advantage of shorter developing time. A current amplifier is also included to magnify the driven ability of the P.I. regulator for cavity fine tuning motors. A careful layout has been performed to avoid interference between RF part, DC small signal part and the current amplifier part. The desk experiment yields good phase detection sensitivity and acceptable stability after the mixer reaches natural thermal balance.
CEA, Gif-sur-Yvette
The acceleration of non relativistic particles, with a velocity lower than light velocity, in an RF cavity is more complex than for relativistic particles. Non-linear behaviours appear on the accelerator voltage because of the phase slippage inside the cavity. Moreover, a superconducting RF cavity is sensitive to various perturbations like mechanical vibrations (microphonics) and Lorentz force detuning. These perturbations produce a significant detuning of the cavity, leading a strong instability for the amplitude and phase of the field because of the narrow bandwidth of the accelerating mode. We will present a simulation approach of the cavity and its LLRF system control in order to ensure proper cavity operation under perturbations in the framework of the SPIRAL2 project.
UPC, Barcelona
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
The conventional electrical model analogy of a RF cavity is a shunt RLC circuit supplied by two current sources representing the RF amplifier and the beam. In the literature, the impedance of the cavity is often calculated in the Fourier domain. This type of cavity modelling has two drawbacks: First, it assumes a perfect matching between the cavity and the amplifier therefore it neglects the reflected voltage. And, second, it does not provide any information about the cavity transient response, for example at startup or upon beam arrival, while this information can be very important for the design of the regulation loops. In this work we will remove these drawbacks by calculating the cavity impedance in Laplace domain taking the reflected voltage into account. We will then modify our model so that it also includes the influence of the beam on the cavity. For transient RF simulations, though, a typical problem is the long simulation time due to the relatively slow transient response compared to the RF period. To overcome this problem, finally, we will use a mathematical method to map the cavity frequency response from RF to baseband to reduce the simulation time significantly.
CRE, Wuppertal
DESY, Hamburg
For future applications in Light Sources and Large Scale Linear Accelerators we have developed a fully digital LLRF system which overcomes the intrinsic problems of analogue and semi digital LLRF systems by realizing all functions in the high speed cores of FPGAs. Due to its modular design using either the ATCA or the VME form factor the LLRF system can be configured conveniently according to the specific requirements of the accelerator to control the rf field in individual resonators or in a combination of cavities. The LLRF input stage can be custom designed for rf frequencies of up to 3.9 GHz. The hardware and software architectures of the Cryoelectra digital LLRF control system are presented.
DESY, Hamburg
Warsaw University of Technology, Institute of Electronic Systems, Warsaw
TUL-DMCS, Łódź
Future RF Control systems will require simultaneuous data acquisition of up to 100 fast ADC channels at sampling rates of around 100 MHz and real time signal processing within a few hundred nanoseconds. At the same time the standardization of low-level systems are common objectives for all laboratories for cost reduction, performance optimization and machine reliability. Also desirable are modularity and scalability of the design as well as compatibility with accelerator instrumentation needs including the control system. All these requirements can be fulfilled with the new telecommunication standard ATCA when adopted to the domain of instrumentation. We describe the architecture and design of an ATCA based LLRF system for the European XFEL. Initial results of the demonstration of such a system at the FLASH user facility will be presented.
CERN, Geneva
JINR, Dubna, Moscow Region
Hardware commissioning of the LHC RF system was successfully completed in time for first beams in LHC in September 2008. All cavities ware conditioned to nominal field, power systems tested and all Low level synchronization systems, cavity controllers and beam control electronics were tested and calibrated. Beam was successfully captured in ring 2, cavities phased, and a number of initial measurements made. These results are presented and tests and preparation for colliding beams in 2009 are outlined.
CERN, Geneva
In the framework of the LHC project the concept has been developed of a global digital signal processing unit (DSPU) that implements in numerical form the architecture of low-level RF systems [1]. The approach, using an FPGA as core for the low-level system, is very flexible and allows the upgrade of the signal processing by modification of the original firmware [2]. The achieved performances of the LHC 1-Turn delay Feedback are compared with project requirements. The PS Transverse Damper DSPU, with automatic loop delay compensation adapting to the beam’s time of flight and Hilbert Filter for single pick-up betatron phase adjustment, is presented. A modified DSPU with digital inputs for the LHC Transverse Damper is also presented.
[1] V. Rossi, CERN SL-2002-047-HRF, CERN, Geneva, July 2002.
[2] V. Rossi, CERN BE-2009-009, CERN, Geneva, January 2009.
Fermilab, Batavia
DESY, Hamburg
ANL, Argonne
KEK, Ibaraki
Funding: *Work supported by Fermi Research Alliance, LLC. under ContractNo. DE-AC02-07CH11359 with the United States Department of Energy.
In September 2008 the DESY-FLASH accelerator was run with up to 550, 3 nano-coulomb bunches at 5 Hz repetition rate. This test is part of a longer term study aimed at validating ILC parameters by operation as close as possible to ILC beam currents and RF gradients. The present paper reports on the analysis that has been done in order to understand the RF control system performance during this test. Actual klystron power requirements and beam stability are evaluated with heavy beam loading conditions. Results include suggested improvements for upcoming tests in 2009
Fermilab, Batavia
Funding: Work supported by U.S. Department of Energy under contract DE-AC02-76CH03000
Progress has been made at Fermilab on the development of feed-forward and feed-back algorithms used to compensate SCRF cavity detuning, which is caused by Lorentz Forces and microphonics. Algorithms that have been developed and tested for the 1.3GHz (ILC-style) SCRF cavities (Capture Cavity II) will be reported.
GSI, Darmstadt
Funding: Project funded by the European Community under the FP6 "Structuring the European Research Area" program (SIS1002, contract number 515873)
SIS100 is a synchrotron that will be built in the scope of the FAIR (Facility for Antiproton and Ion Research) project. High intensity ion beams are required, making it necessary to damp longitudinal coupled and uncoupled bunch oscillations. For this purpose, a closed-loop control system was designed. Its processing part is based on digital signal processors (DSP) and field programmable gate arrays (FPGA) whose advantage is their adaptability to different problems by software changes. Experiments with a prototype were performed at the existing synchrotron SIS12/18 at GSI concentrating on the damping of longitudinal coupled bunch quadrupole oscillations of the lowest order. The configuration of the electronic system is described and results of the machine development experiments are reported. Finally, an outlook to the application in SIS100 is given.
KEK, Ibaraki
NETS, Fuchu-shi
Digital low-level rf (LLRF) control system has been installed in many linear accelerators to stabilize the accelerating field. In the digital LLRF system, the rf signal is down-converted into intermediate frequency for sampling at analog-to-digital converter (ADC) and the number of ADC required for vector sum feedback operation is equal to the number of cavity. In order to decrease the number of the ADCs required, a digital LLRF control system using different four intermediate frequencies has been developed at STF (Superconducting RF Test Facility) in KEK. This digital LLRF control system was operated with four superconducting cavities and the rf field stability under feedback operation was estimated. The result of the performance will be reported.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
NETS, Fuchu-shi
Upgrade of J-PARC linac has been planed using 972 MHz rf system. The rf field regulation is required to be less than ±1% in amplitude and ±1deg. in phase. The basic digital llrf concept is same as the present 324 MHz llrf system using a compact PCI crate. The main alterations are rf and clock generator (RF&CLK), mixer and IQ modulator (IQ&Mixer) and digital llrf algorithm. Since the typical decay time is faster (due to higher operational frequency than present 324 MHz cavity), chopped beam compensation is one of the main concerns. Performance of the digital feedback system using a cavity simulator is summarized.
KEK, Ibaraki
NETS, Fuchu-shi
Vector-sum control of 4 superconducting cavities is examined at STF in KEK. The digital llrf control is carried out and the stabilities of rf fields are obtained. Various studies such as feedback margin necessary for enough field regulation, effects of perturbations of cavity detuning or klystron HV and so on. Performance degradation by elimination of circulators is also studied from the viewpoint of llrf system.
KEK, Ibaraki
NETS, Fuchu-shi
In STF phass-1, four-cavities are operated with vector-sum feedback (FB) control. The FB control instabilities arising from passband of TM010 mode other than π mode with FB loop-delays were measured. Further, a feedforward (FF) table was used in combination with FB control, which improved the flatness of the flat-top region. A method for reduction of overshoot in FB + FF operation is also proposed. By electrically developing a quasi-beam, the response for quasi-beam injection was also measured, and the correction on beam-loading was performed.
I-Tech, Solkan
In a feedback system the disturbances added in the receiver section are one of the major contributors to the amplitude and phase fluctuations of the fields in the RF cavities that are being controlled. It is therefore crucial to thoroughly evaluate the receiver section of the control system. Measurement results of parameters like amplitude noise, phase noise, coupling between RF channels, linearity and temperature dependent drifts of the receiver are presented. We also discuss what the influences of some of the measured parameters on phase and amplitude stability of the RF fields are. Finally, we summarize the results of the measurements and their impact on the future development of the Libera LLRF system.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
JAEA, Ibaraki-ken
In the J-PARC Linac LLRF, for the cavity warming-up, the cavity resonance is automatically tuned to be the accelerating frequency (324MHz and 972MHz) with a mechanical tuner installed on the cavity. Now we are planning to introduce a new method of the cavity-input frequency matching into the digital LLRF control system instead of the cavity resonance tuning for the cavity worming-up. For the frequency matching with the detuned cavity, the RF frequency is modulated by way of phase rotation with the I/Q modulator, while the source oscillator frequency is still fixed. The phase rotation is automatically controlled by the FPGA. The detuned frequency of the cavity is obtained from phase gradient of the cavity field decay at the RF-pulse end. No hardware modification is necessary for this frequency modulation method. The cost reduction or the high durability for the mechanical tuner is expected in the future. The results of the frequency modulation test will be reported in this presentation.
NETS, Fuchu-shi
KEK, Ibaraki
Intermediate-frequency conversion technique has been widely used for rf signal detection. However, this technique has disadvantages such as temperature dependence higher order modes of downconverters. One of our recent attractive developments is the high-speed data acquisition system that combines commercial FPGA board ML555 and fast ADC (ADS5474 14bit, maximum 400MS/s and bandwidth of 1.4 GHz). Direct measurements of 1.3 GHz rf signals are carried out with 270 MHz sampling. The direct sampling method can eliminate a down-converter and avoid calibration of non-linearity of the down-converter. These results are analyzed and compared with conventional measurement system.
NSRRC, Hsinchu
The direct RF feedback has been adopted in storage ring to reduce the beam loading effect for maximizing the stored beam current. Its performance in reducing beam loading is determined by the operational parameters, including the feedback gain, RF phase shift and the loop delay time. This paper presents a mathematical method, based on the Pedersen model, to study the effects of the direct RF feedback on beam loading. Through an example, the influences of different operational parameters on the performance of the direct RF feedback is analyzed by examining the characteristic equation of the feedback loop. The Nyquist criterion is applied for the determination of system stability.
NSRRC, Hsinchu
The quasi-constant current operation is achieved in the NSRRC by periodically injecting electrons from the booster to the storage ring. It means the booster RF system keeps running during operation period, even the injection period occupies only a small portion of the total operation time. To benefit both the energy saving and klystron life, an energy saving controller has been developed and integrated into the TLS booster RF system. The cathode current of the klystron is decreased during the top-injection period. The energy consumption is thus dramatically reduced. A continuous record since the beginning of 2009 shows this controller can save about 78 percent of energy consumption of the booster RF system during normal operation. An overview of the control architecture and its functionality is presented herein.
ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source (SNS) has recently installed a prototype low level radio frequency (LLRF) control system for initial testing. This system is designed to replace the original fixed frequency, two harmonic Accumulator Ring LLRF system used to maintain a gap in the proton beam for extraction to the target. This prototype system is based on the hardware for the Linac LLRF system that has been modified to operate at the low frequencies required for the ring. The goal of the final system is to leverage the mature hardware and software of the Linac systems with the added flexibility needed to support the heavy beam loading requirements of the Accumulator Ring.
ORNL, Oak Ridge, Tennessee
Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
Four ferrite loaded resonant radio frequency (RF) cavity structures and one resistive wall current monitor (WCM) located in the South leg of the Spallation Neutron Source (SNS) accumulator ring provide a 250 ns beam extraction gap. Three ring RF cavities operate at the fundamental accumulator ring revolution frequency (~ 1.05 MHz) to bunch the beam while the fourth cavity operates at the second harmonic (~ 2.10 MHz) to suppress the peak beam current. The SNS ring low-level RF (LLRF) control system utilizes dynamic cavity tuning and proportional, integral, and derivative (PID) feedback control to regulate the amplitude and phase of the fields in the ring RF cavities. In April 2009 the SNS accelerator delivered 835 kW of beam power (928 MeV, 60 Hz, 15 uC/pulse) to the target during a neutron production run. This paper discusses operation and performance of the SNS ring LLRF system with high intensity beam loading.
SLAC, Menlo Park, California
ANL, Argonne
DESY, Hamburg
Funding: *Work supported by the DOE under contract DE-AC02-76SF00515
The FLASH L-Band superconducting (SC) accelerator facility at DESY has a LLRF system that is similar to that envisioned for ILC. This system has extensive monitoring capability and was used to gather performance data relevant to ILC. In particular, waveform data were recorded with beam off for three, 8-cavity cryomodules to evaluate the input rf stability, perturbations to the SC cavity frequencies and the rf overhead required to achieve constant gradient during the 800 μs pulses. In this paper, we discuss the measurements made in September 2008 and the data analysis procedures, and present key findings on the pulse-to-pulse input rf and cavity field stability.
SLAC, Menlo Park, California
CERN, Geneva
Funding: Work supported through SLAC/DOE Contract DE-AC02-76-SF00515 and US LARP CERN collaboration.
The LHC Low Level RF System (LLRF) is a complex multi-VME crate system which is used to regulate the superconductive cavity gap voltage as well as to lower the impedance as seen by the beam through low latency feedback. This system contains multiple loops with several parameters which must be set before the loops can be closed. In this paper, we present a suite of matlab based tools developed to perform the preliminary alignment of the RF stations and the beginnings of the closed loop model based alignment routines. We briefly introduce the RF system and in particular the base band (time domain noised based) network analyzer system built into the LHC LLRF. The main focus of this paper is the methodology of the algorithms used in the routines within the context of the overall system. Measured results are presented which validate the technique. Because the RF systems are located underground in a location which is relatively un-accessible even without beam and completely un-accessible when beam is present, these tools will allow CERN LLRF experts to maintain and tune their LLRF systems from a remote location similar to what was done very successfully in PEP-II at SLAC.
TRIUMF, Vancouver
The rf control system for the 1.3 GHz TRIUMF e-linac elliptical superconducting cavities is a hybrid analogue/digital design. It is based in part on an earlier design developed for the 1/4 wave superconducting cavities of the ISACII linac. This design has undergone several iterations in the course of its development. In the current design, down-conversion to an intermediate frequency of 138MHz is employed. The cavity operates in a self-excited feedback loop, while phase locked loops are used to achieve frequency and phase stability. Digital signal processors are used to provide amplitude and phase regulation, as well as mechanical cavity tuning control. This version also allows for the rapid implementation of operating firmware and software changes, which can be done remotely, if the need arises. This paper describes the RF control system and the experience gained in operating this system with a single-cavity test facility.
TU Darmstadt, RTR, Darmstadt
GSI, Darmstadt
Funding: This work was partly supported by Deutsche Telekom Stiftung.
The effects of heavy beam loading on the RF control loops of a double-harmonic cavity system are examined. This cavity system that will be realized at the GSI Helmholtzzentrum für Schwerionenforschung in the scope of the SIS18 upgrade program consists of a main broadband cavity and a second harmonic narrowband cavity. The cavities comprise both an amplitude and a phase feedback loop. In addition, the narrowband cavity includes a feedback loop which controls its resonance frequency to follow the main RF frequency. After modelling the cavity system and the feedback loops, an analytic controller design is presented. In addition, longitudinal beam dynamics are added to the cavity model to allow a detailed simulation of the cavity-beam interaction. Realistic simulation results are given for an acceleration cycle of heavy-ions to demonstrate the performance of the RF control loops.
JLAB, Newport News, Virginia
Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The RF system model based on MATLB has been developed for analyzing the basic characteristics of the LLRF control system being designed for the 12 GeV Energy Upgrade of the CEBAF accelerator. In our model, a typically complex cavity representation is simplified to in-phase and quadrature (I&Q) components. Lorentz Force and microphonic detuning is incorporated as a new quadrature carrier frequency (frequency modulation). Beam is also represented as in-phase and quadrature components and superpositioned with the cavity field vector. Afterward signals pass through two low pass filters, where the cutoff frequency is equal to half of the cavity bandwidth then they are demodulated using the same detuning frequency. Because only baseband I&Q signals are calculated, the simulation process is very fast when compared to other controller-cavity models. During the design process we successfully analyzed gain requirements vs. field stability for different superconducting cavity microphonic backgrounds and Lorentz Force coefficients. Moreover, we were able to evaluate different types of a LLRF structures:GDR* and SEL** as well as klystron power requirements for different cavities and beam loads.
*Generator Driven Resonator
**Self Excited Loop
Warsaw University of Technology, Institute of Electronic Systems, Warsaw
DESY, Hamburg
One of the most important requirements for the XFEL RF system is to assure a very precise RF field stability within the accelerating cavities. The required amplitude and phase stability equals respectively dA/A <3·10-5, dphi<0.01 deg @ 1.3GHz in the injector and dA/A<10-3, dphi <0.1 deg @1.3GHz in the main linac section of the XFEL facility. Fulfilling such requirements is a very challenging task for the 1.5 km long main linac system and about 3.4 km length of the entire facility. Thousands of electronic and RF devices must be precisely phase synchronized for effective controlling of the RF field parameters. We describe the the proposed architecture of the RF Master Oscillator and the Phase Reference Distribution System for the XFEL. Design choices were based on the experience gained during the commissioning of the FLASH phase reference distribution system and on many laboratory experiments with distribution system components. Proposed system parameter analysis shows that the given requirements for the distributed signal phase stability can be fulfilled easily for the main linac section. Fulfilling the injector requirements may require using optical distribution techniques.
NSRRC, Hsinchu
Quadruple Bend Achromat (QBA) low emittance lattice of 3GeV Taiwan Photon Source (TPS) allows us to consider three configurations for location of a pair of superconducting transverse RF deflecting cavities for generation ultra short X-ray pulses. The available arrangements for location of cavities in a super-period of TPS are investigated. We find that use of such deflecting cavities in the middle of two QBA lattices in a super-period of TPS provides better conditions for emittance of electron beam.
NSRRC, Hsinchu
Deflecting cavity generates a correlation between longitudinal position and vertical momentum of electrons in the synchrotron light sources for production short X-ray pulses. Use of such structures leads to growth in vertical amplitude and slope of stored electrons. Since errors are characteristic of real machine, any errors associated with the photon compression system must be considered and the tolerance of them must be evaluated. In this paper we present simulation of main errors due to deflecting structures, QBA lattice and injection system and find tolerances of them.
NSRRC, Hsinchu
A superconducting accelerating RF cavity is going to be installed in 3GeV Taiwan Photon Source (TPS). It causes a reduction in bunch length in contrast with operation of normal type of RF cavity. A higher harmonic RF cavity is usually considered as an important tool to control the bunch length in the storage rings. The harmonic cavity in lengthening mode can also be helpful for improving the lifetime which is usually dominated in the storage rings by large angle intrabeam scattering (Touschek). In this paper we study the effects of third active harmonic cavity on bunch length of the TPS ring. We present the procedure, the simulation and the formulae to analyze the effects of third harmonic cavity on the rms bunch length while the main superconducting RF system is operated in 3MV. It is shown that the longitudinal rms electron bunches will lengthen up to 7.9 times for the optimum operation of the harmonic system.
SLAC, Menlo Park, California
Stanford University, Stanford, California
UCLA, Los Angeles, California
Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
SSRL and SLAC groups are developing a long-range plan to transfer its evolving scientific programs from the SPEAR3 light source to a much higher performing photon source that would be housed in the 2.2-km PEP-II tunnel. While various concepts for the PEP-X light source are under consideration, including ultimate storage ring and ERL configurations, the present baseline design is a very low-emittance storage ring. A hybrid lattice has DBA or QBA cells in two of the six arcs that provide a total ~30 straight sections for ID beam lines extending into two new experimental halls. The remaining arcs contain TME cells. Using ~100 m of damping wigglers the horizontal emittance at 4.5 GeV would be ~0.1 nm-rad with >1 A stored beam. PEP-X will produce photon beams having brightnesses near 1022 at 10 keV. Studies indicate that a ~100-m undulator could have FEL gain and brightness enhancement at soft x-ray wavelengths with the stored beam. Crab cavities or other beam manipulation systems could be used to reduce bunch length or otherwise enhance photon emission properties. The present status of the PEP-X lattice and beam line designs are presented and other implementation options are discussed.
PKU/IHIP, Beijing
The PKU Terahertz facility (PTF) is planned as a compact, high power Terahertz user facility based on the coherent undulator radiation concept and the superconducting radiofrequency technology for the linear accelerator. By utilizing a 3.5-cell DC-SC (DC-Superconducting) photoinjector, the PTF will provide high average power, coherent terahertz radiation with quasi-monochromaticity and wavelength tunable between 400um ~ 1200um, serving as a powerful tool for frontier researches and practical applications in the THz realm. Key components of the 3.5-cell DC-SC photoinjector have been prepared and the beamline is under construction. In this paper, the technical layout of the injector and the conceptual design of the PTF will be presented.
UW-Madison/SRC, Madison, Wisconsin
SLAC, Menlo Park, California
The microbunching gain of the driver for the Wisconsin FEL (WiFEL) is reduced by more than an order of magnitude by using a single-stage bunch compressor rather than a two-stage design. This allows compression of a bunch with lower energy spread for improved FEL performance.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Recently, an upgrade of RHIC storage RF system with a superconducting 56 MHz cavity was proposed. This upgrade will provide significant increase in the acceptance of storage RF bucket. Presently, the short bunch length for collisions is obtained via RF gymnastics with bunch rotation (called “re-bucketing”), because the length of 197MHz bucket of 5 nsec is too short to accommodate long bunches otherwise. However, some increase in the longitudinal emittance occurs during re-bucketing. The 56MHz cavity will produce sufficiently short bunches which would allow one to operate without re-bucketing procedure. This paper summarizes simulation of beam evolution due to Intra-beam scattering (IBS) for beam parameters expected with the 56 MHz SRF cavity upgrade. Expected luminosity improvement is shown both for Au ions at 100 GeV/nucleon and for protons at 250 GeV.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
There is a strong interest in low-energy RHIC collisions in the energy range below present RHIC transition energy. These collisions will help to answer one of the key questions in the field of QCD about the existence and location of a critical point on the QCD phase diagram. For low-energy RHIC operation, particle losses from the RF bucket are of particular concern since the longitudinal beam size is comparable to the existing RF bucket at low energies. However, operation below transition energy allows us to exploit an Intra-beam Scattering (IBS) feature that drives the transverse and longitudinal beam temperatures towards equilibrium by minimizing the longitudinal diffusion rate using a high RF voltage. Simulation studies were performed with the goal to understand whether one can use this feature of IBS to improve luminosity of RHIC collider at low-energies. This paper presents results of simulations which show that additional luminosity improvement for low-energy RHIC project may be possible with high RF voltage from a 56 MHz superconducting RF cavity that is presently under development for RHIC.
CERN, Geneva
BNL, Upton, Long Island, New York
KEK, Ibaraki
Funding: This work was supported by the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395).
Modern colliders bring into collision a large number of bunches per pulse or per turn to achieve a high luminosity. The long-range beam-beam effects arising from parasitic encounters at such colliders are mitigated by introducing a crossing angle. Under these conditions, crab cavities (CC) can be used to restore effective head-on collisions and thereby to increase the geometric luminosity. In this paper, we discuss the beam dynamics issues of a single global crab cavity (GCC) for both nominal LHC optics and one upgrade LHC optics.
LBNL, Berkeley, California
Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Crab cavity is proposed to compensate the geometric luminosity loss of crossing angle collision at LHC upgrade. In this paper, we report on strong-strong beam-beam simulation of crab cavity compensation at LHC using the BeamBeam3D code. Simulation results showed that using a pair of local compensation for each beam could significantly improve the beam luminosity at collision. However, this improvement could be lost with random offset errors from the RF deflection cavities.
KEK, Ibaraki
Crab cavities were installed at KEKB at the beginning of 2007. The beam operation with the crab cavities is in progress. In this paper, machine performance with crab crossing is described focusing on a specific luminosity and a beam lifetime issue related to the dynamic beam-beam effects.
KEK, Ibaraki
Lattice design for SuperKEKB is based on the present KEKB lattice. The unit-cell structure of KEKB has a wide range of flexibility, therefore main beam-optical parameters can be adjusted without changing the arcs. The interaction region (IR) and the other straight sections are changed to squeeze the vertical beta function to 3 mm at IP, keeping sufficient dynamic apertures. Recent progress such as a new design of IR with superconducting quadrupole magnets at 1.9 K, traveling focus scheme by using crab cavities, local chromaticity correction for the high energy ring, is presented.
KEK, Ibaraki
Beam-beam tune shift parameter characterizes the strength of the nonlinear interaction due to the beam-beam collision. The tune shift has been measured in many e+e- colliders and has been an indicator for the collider performance. The record for the tune shift is known as 0.07-0.1 depending on the parameter of the collider, especially the radiation damping rate. We discuss the fundamental limit of the tune shift can be very high (>0.2) depending on the choice of collider parameter, which concerns operating point near the half integer tune, head-on collision and travel focus.
KEK, Ibaraki
KEKB is a multi-bunch, high-current electron-positron collider. Newly installed crab cavities realized an effective head-on collision, while maintaining finite-angle crossing orbits. Bunches form a single train followed by a beam abort gap. We observed a beam phase advancing along a train due to transient beam loading. Since there is a difference in the beam phase between the two beams, a longitudinal displacement of the collision vertex is expected under the crabbing collision. Estimated variations agree with those detected by the Belle*. A displacement in the horizontal beam position was observed in correspondence with the variations in the beam phase. We found that the horizontal displacement was caused by a transverse kick of the crab cavities to phase-shifted bunches. Moreover, a rapid phase advancing was observed at the leading part in a train in the LER. We suspect that some longitudinal wakes with low Q values in accelerator components might contribute to the rapid change in the beam phase.
*H. Kichimi et al., to be published.
SLAC, Menlo Park, California
INFN/LNF, Frascati (Roma)
Funding: Work supported by the U.S. Department of Energy under contract number DE-AC03-76SF00515.
The use of normal conducting cavities and an ion-clearing gap will cause a significant RF accelerating voltage gap transient and longitudinal phase shift of the individual bunches along the bunch train in both rings of the SuperB accelerator. Small relative centroid position shifts between bunches of the colliding beams will have a large adverse impact on the luminosity due to the small beta y* at the interaction point (IP). We investigate the possibility of minimizing the relative longitudinal position shift between bunches by reducing the gap transient in each ring and matching the longitudinal bunch positions of the two rings at the IP using feedback/feedforward techniques in the LLRF. The analysis is conducted assuming maximum use of the klystron power installed in the system.
SLAC, Menlo Park, California
Funding: Work supported by the DOE under contract DE-AC02-76SF00515.
Optimization of Interaction Region parameters of a TeV energy scale linear collider has to take into account constraints defined by phenomena such as beam-beam focusing forces, beamstrahlung radiation, and hour-glass effect. With those constraints, achieving a desired luminosity of about 2·1034 would require use of e+e- beams with about 10 MW average power. It is shown in this paper that application of the ‘‘travelling focus'' regime [V.Balakin, 1991] may allow reduction of required beam power by at least a factor of two, helping cost reduction of the collider, while keeping the beamstrahlung energy loss reasonably low. The technique is illustrated in application to 500 GeV CM parameters of the International Linear Collider. Application of this technique may also in principle allow recycling the e+e- beams and/or recuperation of their energy.
LLNL, Livermore, California
SLAC, Menlo Park, California
A high energy photon-photon collider can be created by the combination of electron linear accelerators with terawatt peak power lasers to create high energy photon beams through Commpton backscattering. The realization of this option requires of order 10kW of average laser power if each laser pulse is used once and discarded. Proposals for recirculating cavities to allow the laser light to be reused open the potential for laser systems with much lower required average power. We review the current status of laser technology and it's ability to realize a photon collider system.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
CERN, Geneva
In Muon Ionisation Cooling, closely packed high-field RF cavities are interspersed with energy-absorbing material in order to reduce particle beam emittance. Transverse focussing of the muon beams is achieved by superconducting magnets. This results in the RF cavities sitting in intense magnetic fields. Recent studies have shown that this may limit the peak gradient that can be achieved in the RF cavities. In this paper, we study the effect that a reduced RF gradient may have on the cooling performance of the Neutrino Factory lattice and examine methods to mitigate the effect.
Muons, Inc, Batavia
Fermilab, Batavia
Funding: Supported in part by DOE STTR grant DE-FG02-05ER86252
Earlier studies on the front end of a neutrino factory or muon collider have relied on a single simulation tool, ICOOL. We present here a cross-check against another simulation tool, G4beamline. We also perform a study in economizing the number of RF cavity frequencies and gradients. We conclude with a discussion of future studies.
Fermilab, Batavia
Muons, Inc, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-05ER86252 and FRA DOE contract number DE-AC02-07CH11359
Gas-filled RF cavities can provide high-gradient accelerating fields for muons, and can be used for simultaneous acceleration and cooling of muons. In this paper we explore using these cavities in the front-end of the capture and cooling systems for neutrino factories and muon colliders. We consider using gas-filled RF cavities for the initial front end cooling systems. We also consider using them for simultaneous phase-energy rotation and cooling in a front-end system. We also consider using lower-density RF cavities, where the gas density is primarily for RF breakdown suppression, with less cooling effect. Pressurized RF cavities enable higher gradient rf within magnetic fields than is possible with evacuated cavities, enabling more options in the front-end. The status of designs of the capture, phase rotation, and precooling systems of muon beams in pressurized cavities is described.
Muons, Inc, Batavia
Fermilab, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86282
The MANX experiment is to demonstrate the reduction of 6D muon phase space emittance using a continuous liquid absorber to provide ionization cooling in a helical solenoid magnetic channel. The experiment involves the construction of a short two-period long helical cooling channel (HCC) to reduce the muon invariant emittance by a factor of two. The HCC would replace the current cooling section of the MICE experiment now being setup at the Rutherford Appleton Laboratory. The MANX experiment would use the existing MICE spectrometers and muon beam line. This paper shall consider the various approaches to integrate MANX into the RAL hall using the MICE spectrometers. This study shall discuss the matching schemes used to minimize losses and prevent emittance growth between the MICE spectrometers and the MANX HCC. Also the placement of additional detection planes in the matching region and the HCC to improve the resolution will be examined.
JLAB, Newport News, Virginia
Muons, Inc, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86351
Neutrino Factories and Muon Colliders require rapid acceleration of short-lived muons to multi-GeV and TeV energies. A Recirculating Linear Accelerator (RLA) that uses International Linear Collider (ILC) RF structures can provide exceptionally fast and economical acceleration to the extent that the focusing range of the RLA quadrupoles allows each muon to pass several times through each high-gradient cavity. A new concept of rapidly changing the strength of the RLA focusing quadrupoles as the muons gain energy is being developed to increase the number of passes that each muon will make in the RF cavities, leading to greater cost effectiveness. We discus the optics and technical requirements for RLA designs, using RF cavities capable of simultaneous acceleration of both μ+ and μ- species, with pulsed Linac quadrupoles to allow the maximum number of passes.
DESY, Hamburg
ANL, Argonne
Fermilab, Batavia
KEK, Ibaraki
Funding: Work at Argonne supported by U.S. Department of Energy, Office of Science, office of Basic Energy, Sciences, under Contract No. DE-AC02-06CH11357
XFEL and ILC both intend to accelerate long beam pulses of a few thousand bunches and high average current. It is expected that the superconducting accelerating cavities will eventually be operated close to their respective gradient limits as they are pushed to higher energies. In addition, a relative energy stability of <10-4 must be maintained across all bunches. These parameters will ultimately push the limits of several sub systems including the low-level rf control, which must properly compensate for the heavy beam loading while avoiding problems from running the cavities close to their quench limits. An international collaboration led by DESY has begun a program of study to demonstrate such ILC-like conditions at FLASH, which serves as a prototype for both XFEL and ILC. The objective is to achieve reliable operation with pulses of 2400 3-nC bunches spaced by 330 ns (a current of 9 mA) while meeting the required energy stability and while operating accelerating cavities close to their quench limits. Other goals include measurement of cryoload from HOM heating and evaluation of rf power overhead for the ILC. The paper will describe the program and report recent results.
AES, Medford, NY
Funding: Work supported by The Department of Energy under SBIR Contract DE-FG02-08ER85054
From past work we found that within the cost of the String Assembly that dominates the overall cost of the cryomodules for ILC, the greatest cost elements are the helium vessel with the 2 phase pipe assembly, the niobium material, and the SRF cavity fabrication*. The cost of niobium is dependant upon market supply and demand and is essentially out of our control. We have carried out an aggressive study to reduce the cost of cavity fabrication in a high production environment**, which leaves the helium vessel for further investigation. It is recognized that significant cost savings may be realized if the helium vessel could be constructed of stainless steel instead of titanium material as is currently planned. To facilitate this change (AES) has designed a niobium to stainless steel transition assembly that will interface the helium vessel to the SRF Cavity at each end. Details of the design and analysis of the low cost helium vessel assembly are discussed along with potential cost reductions for the ILC high production run.
*E. Bonnema, J. Sredniawski,"ILC RF Unit Industrial Cost Study Methodology & Results"
**A. Favale, J. Sredniawski, M. Calderaro, E. Peterson,"ILC Cavity Fabrication Optimization for High Production"
CLASSE, Ithaca, New York
Funding: Work supported by NSF, New York State, and Cornell University
A cryomodule design for the Cornell Energy Recovery Linac (ERL) will be based on TTF technology, but must have several unique features dictated by the ERL beam parameters. The main deviations from TTF are that the HOM loads must be on the beamline for sufficient damping, that the average power through the RF couplers is low, and that cw beam operation introduces higher heat loads. Several of these challenges were addressed for the Cornell ERL Injector, from which fabrication and operational insight was gained. A baseline design for the Cornell ERL Linac cryomodule will be presented that includes fabrication and operational considerations along with thermal and mechanical analyses.
KEK, Ibaraki
Fermilab, Batavia
INFN/LASA, Segrate (MI)
DESY, Hamburg
In an attempt at demonstrating an average field gradient of 31.5 MV/m as per the design accelerating gradient for ILC, a program called S1-Global is in progress as an international research collaboration among KEK, INFN, FNAL, DESY and SLAC. The S1-Global cryomodule will contain eight superconducting cavities from FNAL, DESY and KEK. The cryomodule will be constructed by joining two half-size cryomodules, each 6 m in length. The module containing four cavities from FNAL and DESY will be constructed by INFN. The design of this module is based on an improved 3rd generation TTF design. KEK will modify the 6-meter STF cryomodule to contain four KEK cavities. The designs of the cryomodules are ongoing between these laboratories, and the operation of the system is scheduled at the KEK-STF from June 2010. In this paper, the S1-Global cryomodule plan and the module design will be presented. ‘S1-Global collaboration’ as a co-author.
NSRRC, Hsinchu
The feasibility of SRF operation at 2K using the remaining refrigeration capacity of an operating 4.5K cryogenic plant at NSRRC is examined. A refrigeration configuration with warm compression is proposed under an assumption that a reasonable amount of cryogenic heat load is required at 2K. The expectation of the efficacy of the cold and warm heat exchangers (HEX) is evaluated in terms of the corresponding equivalent cryogenic heat load on the 4.5K cold box. A factor approximately 9.5 or 6.0 is required to convert the cryogenic loss, 12 W at 2K, into our 4.5K cold box operated in a refrigeration mode without or with the cold heat exchanger (efficiency 85 %), respectively. An additional benefit is that the required volumetric pumping speed of the warm compressor can be greatly decreased. Moreover, a considerable cold capacity from the sub-atmospheric cold return helium gas can be ultimately converted by combining the cold HEX working together with a highly effective warm HEX, to a conversion factor 3.8 with an efficiency 95 %. Special attention must be devoted to minimize the risk of contamination or impurity for a turbine refrigerator.
TIPC, BeiJing
IHEP Beijing, Beijing
IHEP Beiing, Beijing
Technical Institute of Physics and Chemistry, Beijing
Graduate School of the Chinese Academy of Sciences, Beijing
Funding: Work supported by NSFC 10525525
In order to obtain the design, manufacture and operational experiences on the SRF cryomodule toward ILC, a test cryomodule for 1.3GHz single 9-cell SC cavity was designed by IHEP (Institute of High Energy Physics) and TIPC (Technical Institute of Physics and Chemistry) jointly. This cryomodule will be used as a 1.3GHz 9 cell SC cavity horizontal test facility. The cryogenic system for the cryomodule is designed and will be operated at 2.0K, with the saturated superfluid helium. The major requirements, design, simulation results of the cryomodule are reported in the paper. This key component of a superconducting accelerator test unit will be built in the near future at IHEP.
JLAB, Newport News, Virginia
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In the framework of the ongoing CEBAF 12 GeV upgrade program improvements are being made to refurbish cryomodules housing JLab’s original 5-cell cavities. Recently we have started to look into a possible simplification of the HOM-absorber design combined with the need to find alternative material candidates. The absorbers are implemented in two HOM-waveguides immersed in the helium bath and need to operate at 2K. We therefore have built a cryogenic setup to perform measurements on sample load materials to investigate their lossy characteristics and variations from room temperature down to 2K. Initial results are presented in this paper.
DESY, Hamburg
The DESY Engineering Data Management System, DESY EDMS, is a fully Web-based central information management platform at the European XFEL and the Global Design Effort for the International Linear Collider (ILC GDE). It provides functionality for managing documents and 3D CAD data and for performing configuration and change management. It can control complex information structures and keep track of their dependencies and history, i.e. their evolution over time. Due to its powerful capabilities for automating workflows and controlling information access, the DESY EDMS can coordinate processes and manage authorizations and responsibilities in large and complex organizations, which may include several institutes and industrial partners. Applications of the DESY EDMS range from small-scale document management for work groups, up to managing the complexity of world-wide collaborations during design and construction activities. The poster describes the architecture of the DESY EDMS, introduces some of its use cases and reports lessons learned in developing and operating the system.
PAL, Pohang, Kyungbuk
KAERI, Daejon
Funding: Work supported by PEFP and MEST in Korea
The objectives of the cooling system of Proton Engineering Frontier Project (PEFP) Drift Tube Linac (DTL) operated in combination with the low-level RF system (LLRF) are to regulate the resonant frequency of the drift tube cavities of 350 MHz. To provide an effective means of bringing the PEFP DTL up for a resonance condition within ±5 kHz, the prototype of the cooling system has been designed and fabricated to investigate the performance features for the servo stabilization of the cavity resonant frequency. As a result, it is estimated that the resonant frequency could be regulated less than ±1 kHz with this proposed feedback temperature controlled cooling system although introducing a little nonlinear features as the reference operating temperature changes. This report describes the design and performance test results of a cooling system, including the size of water pumping skid components and the temperature control scheme.
CIPS, Boulder, Colorado
Funding: This work is supported by the U.S. Department of Energy grant DE-FG02-04ER41317.
The RF properties of photonic crystals (PhCs) can be exploited to avoid the parasitic higher order modes (HOMs) that degrade beam quality in accelerator cavities and reduce efficiency and power in RF generators. Computer simulations show that long-range wake fields are significantly reduced in accelerator structures based on dielectric PhC cavities, which can be designed to trap only those modes within a narrow frequency range. A 2D PhC structure can be used to create a 3D accelerator cavity by using metal end-plates to confine the fields in the third dimension; however, even when the 2D photonic structure allows only a single mode, the 3D structure may trap HOMs, such as guided modes in the dielectric rods, that increase wake fields. For a 3D cavity based on a triangular lattice of dielectric rods, the rod positions can be optimized (breaking the lattice symmetry) to reduce radiation leakage using a fixed number of rods; moreover, the optimized structure has reduced wake fields. Using computer simulation, wake fields in pillbox, PhC, and optimized photonic cavities are calculated; a design for a klystron using the optimized photonic cavity structure is presented.
Euclid TechLabs, LLC, Solon, Ohio
Coating Technology Solution, Inc., Somerville
ANL, Argonne
Funding: This work is supported by the US Department of Energy
There has been considerable progress in using microfabrication techniques to produce experimental rf sources. These devices have for the most part been based on micromachined copper surfaces or silicon wafers. We are developing THz diamond wakefield structures produced using Chemical Vapor Deposition (CVD) technology. The electrical and mechanical properties of diamond make it an ideal candidate material for use in dielectric rf structures: high breakdown voltage (~600 MV/m), extremely low dielectric losses and the highest thermoconductive coefficient available for removing waste heat from the device. These structures are based on cylindrical diamond dielectric tubes that are manufactured via a relatively simple and inexpensive chemical vapor deposition (CVD) process, plasma assisted CVD. Use of the CVD process is a much simpler method to achieve high quality rf microcavities compared to other microfabrication techniques. We are designing a number of diamond rf structures with fundamental TM01 frequencies in the 0.1-1 THz range. Numerical simulations of planned experiments with these structures will be reported.
Imperial College of Science and Technology, Department of Physics, London
Fermilab, Batavia
The International Design Study for the Neutrino Factory (IDS-NF), which is being carried out by personnel from the Americas, Asia, and Europe, has been established by the Neutrino Factory community to deliver a Reference Design Report for the facility by 2012*. The baseline design, developed from that defined in the ISS**, will provide 1021 muon decays per year from 25GeV stored muon beams. The facility will serve two neutrino detectors; one situated at source-detector distance of between 3000-5000km, the second at 7000-8000km. Muon storage rings have also been proposed as the basis of a multi-TeV lepton-antilepton Muon Collider. The R&D required to deliver the Neutrino Factory and that required to realise the Muon Collider have many synergies including: the pion-production target; ionisation cooling; rapid acceleration of large emittance beams; and the provision of high-gradient accelerating cavities that operate in high magnetic fields. The conceptual design of the accelerator facility for the Neutrino Factory and the relation of the IDS-NF to the EUROnu Design Study will be described***.
*The decision point identified by the Strategy Group of the CERN Council.
**The International Scoping Study for a future Neutrino Factory and super-beam facility.
***Submitted on behalf of the IDS-NF.
IAP/RAS, Nizhny Novgorod
A new two-beam accelerating structure based on periodic chain of rectangular shape multi-mode cavities was suggested recently*. The structure is aimed to increase threshold breakdown surface field and thus to provide a high gradient. This threshold increase is to be brought about by designing cavities of the structure to operate simultaneously in several harmonically-related TMn,n,0 modes, thereby reducing the effective exposure time of the cavity surface to the peak fields. The more number of the operating modes is the more reduction of the exposure time. Unfortunately, a big amount of modes leads to limitation for cavity length and practical limitation of filling factor. In order to avoid this, it is suggested to operate with several TMn,n,l modes with non-zero longitudinal indices. These modes are able to provide the long interaction of a moving bunch with RF fields along the cavity. Such regime requires for the longitudinal index l to be strictly proportional the mode frequency. A cylindrical shape cavity design is also considered.
*S.V. Kuzikov, S.Yu. Kazakov, M.E. Plotkin, J.L. Hirshfield, High-Gradient Multi-Mode Two-Beam Accelerating Structure, Proc. of EPAC’08 Conf., Genoa, June 23-27, 2008, WEPP133.
IAP/RAS, Nizhny Novgorod
Yale University, Physics Department, New Haven, CT
Omega-P, Inc., New Haven, Connecticut
Funding: Sponsored in part by US Department of Energy, Office of High Energy Physics.
A multi-mode cavity design for a two-beam accelerator aimed to achieve an accelerating gradient exceeding 150 MeV/m is reported. The cavity has a square cross section which allows excitation in several equidistantly-spaced eigen modes by a bunched drive beam in such a way that the RF fields reach peak values only during time intervals that can be much shorter than for excitation of a single mode, thus exposing the cavity surfaces to strong fields for shorter times. This feature is expected to raise the breakdown and pulse heating thresholds. In order to measure an increase in breakdown threshold surface electric field due to this reduction of exposure time during each RF period, a high-power experiment is planned. Preliminary calculations show that such a study in which comparison of breakdown threshold would be made of a conventional single-mode cavity with a multi-mode cavity can in principle be carried out using the drive beam of the CTF-3 test stand at CERN.
MIT/PSFC, Cambridge, Massachusetts
Funding: This work was supported by the Department of Energy, Grant No. DE-FG02-95ER40919 and the Air Force Office of Scientific Research, Grant No. FA9550-06-1-0269.
Relativistic elliptic electron beams have applications in the research and development of a new class of elliptic- or sheet-beam klystrons which have the potential to outperform conventional klystrons in terms of power, efficiency, and operating voltage. This paper reports on results of a small-signal analysis of space-charge waves on a relativistic elliptic electron beam in a perfectly-conducting beam tunnel. A dispersion relation is derived. A computer code is developed and used in studies of the dispersion characteristics of various relativistic elliptic electron beams.
USTC/NSRL, Hefei, Anhui
Funding: the National Nature Science Foundation of China, Grant No. 10375060, 10375061 and 10675116
One of the major concerns in the development of hybrid dielectric-iris-loaded structure is the performance of the used dielectric. The previous dielectric is machinable but the loss tangent is slightly high. So we adopt the new dielectric (Mg-Ca-Ti-O) with loss tangent of about 2·10-4. Because of its high hardness and brittleness, the machining technology and methods are attempted. In this paper, we present a new design of the structure. The model cavities and the coupler for this structure with the new dielectric are investigated experimentally. The experiment results are accorded with the simulated results. In the end, the amplitude and phase shift of the electric field and R/Q of this structure at the operation frequency are even got by a bead-pull experiment.
USTC, Hefei, Anhui
USTC/NSRL, Hefei, Anhui
Funding: National Nature Science Foundation of China, Grant No. 10675116 and 10375060
We present the new experimental results for an X-band (11.42GHz) metallic PBG accelerating cavity. A coupler of a single cavity was fabricated and cold tested. An X-band traveling-wave PBG accelerator was designed based on CST MWS transient analysis. The X-band PBG accelerator is now under construction, future work will focus on the structure to be cold tested and tuned.
Yale University, Beam Physics Laboratory, New Haven, Connecticut
Yale University, Physics Department, New Haven, CT
Omega-P, Inc., New Haven, Connecticut
Fermilab, Batavia
Funding: Supported by US Department of Energy, Office of High Energy Physics
A detailed analysis is presented of a new concept for a high current, high gradient proton beam accelerator in a normal conducting (i.e. room temperature) structure. The structure consists of a cascade of RF cavities in a nearly uniform magnetic axial field. The proton energy gain mechanism relies upon cyclotron resonance acceleration in each cavity. In order to check the concept and determine its limits, an engineering design is presented of a four cavity electron counterpart test accelerator under construction that will mimic parameters of the multi-cavity proton accelerator.
RRCAT, Indore (M.P.)
Particle accelerator programs being pursued by the Indian labs cover a broad range, encompassing accelerators for nuclear physics research (NPR) (in the low and intermediate energy range), construction of synchrotron radiation sources (SRS) as well as participation in international accelerator projects, especially those related to high energy physics. Machines for NPR include 14MV Pelletrons, augmented by home built superconducting linac boosters to enhance the energy & mass range of the ion beams, and a superconducting cyclotron which is currently undergoing commissioning at Kolkata. Two SRS, namely, a 450 MeV ring Indus-1 and 2.5 GeV booster cum light source, Indus-2, have been indigenously constructed and set up at Indore. A program is also on to develop a high current proton accelerator that will eventually be used for R&D linked to ADS. Regarding our international collaborations, Indian labs have contributed to setting up of LHC at CERN, are associated with the CLIC Test Facility 3 & Linac-4 and the FAIR project at Hamburg besides working with Fermilab on ILC/Project-X R&D. The talk will give an overview of some of the recent developments related to these activities.
JLAB, Newport News, Virginia
Funding: Work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, and by the DOE Contract DEAC05-84ER40150.
As the only currently operating free electron laser (FEL) based on a CW superconducting energy recovering linac (ERL), the Jefferson Laboratory FEL Upgrade remains unique as an FEL driver. The present system represents the culmination of years of effort in the areas of SRF technology, ERL operation, lattice design, high power optics and DC photocathode gun technology. In 2001 the FEL Demo generated 2.1 kW of laser power. Following extensive upgrades, in 2006 the FEL Upgrade generated 14.3 kW of laser power breaking the previous world record. The FEL Upgrade remains a valuable testbed for studying a variety of collective effects, such as the beam breakup instability, longitudinal space charge and coherent synchrotron radiation. Additionally, there has been exploration of operation with lower injection energy and higher bunch charge. Recent progress and achievements in these areas will be presented, and two recent milestones installation of a UV FEL and establishment of a DC gun test stand will be discussed. Additionally, a review of the longitudinal matching scheme and the use of incomplete energy and its implications will be presented.
JAI, Oxford
Imperial College of Science and Technology, Department of Physics, London
UMAN, Manchester
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
STFC/RAL, Chilton, Didcot, Oxon
Brunel University, Middlesex
GIROB, Oxford
Fermilab, Batavia
Gray Institute for Radiation Oncology and Biology, Oxford
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Cockcroft Institute, Lancaster University, Lancaster
Funding: EPSRC EP/E032869/1
The PAMELA (Particle Accelerator for MEdicaL Applications) project is to design an accelerator for proton and light ion therapy using non-scaling Fixed Field Alternating Gradient (FFAG) accelerators, as part of the CONFORM project, which is also constructing the EMMA electron model of a non-scaling FFAG at Daresbury. This paper presents an overview of the PAMELA design, and a discussion of the design goals and the principles used to arrive at a preliminary specification of the accelerator.
NSRRC, Hsinchu
Since use of such deflecting structures leads to growth in vertical amplitude and slope of electrons, non-zero momentum compaction factor, nonlinearities and coupling of the elements between the deflectors affect the tilted electrons even in perfect machine and change their amplitude and slope at second deflecting cavity. It causes the second deflector cannot cancel the first kick perfectly and leads to increase of transverse emittance. We have studied simulation and detail analyses of effects of non-zero momentum compaction factor and sextupoles between the deflecting structures, as sources of emittance degradation in TPS and evaluate how much emittance growths due to the effects. We also contrast the statuses of interior sextupoles and elucidate them.
CERN, Geneva
Funding: This work was supported by the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395).
The use of crab cavities in the LHC may not only raise the luminosity, but it could also complicate the beam dynamics, e.g. crab cavities might not only cancel synchro-betatron resonances excited by the crossing angle but they could also excite new ones. In this paper, we use weak-strong beam-beam model to study the incoherent linear tune shift of the weak beam, for the crossing collision case and crab collision case with a finite crossing angle. The tune shift is also compared among the head-on collision, crossing collision and crab collision cases, both analytically and numerically.
IAP, Frankfurt am Main
Funding: * Work supported by BMBF contr. No. 06F134I & EU contr. No. EFDA/99-507ERB5005CT990061
The International Fusion Materials Irradiation Facility (IFMIF) is looking for an efficient drift-tube linac (DTL) which can accelerate a 125mA, CW deuteron beam from 5MeV to 40MeV with a high beam quality and nearly no beam loss. Taking advantages of the KONUS dynamics concept and the H-type structure, a compact DTL design has been realized by IAP, Frankfurt University, with satisfying performances. Including simulated errors, the feasibility of the IAP scheme has been carefully checked as well.
ANL, Argonne
We developed a moving window algorithm for the SEDG time-domain code, NekCEM, for wake field calculations. NekCEM is a highly efficient and spectrally accurate electromagnetic solver using the spectral element discontinuous Galerkin (SEDG) method based on body-fitted spectral element hexahedral meshes. When the domain of interest is around a moving bunch within a certain distance, one does not need to carry out full domain simulations. Moving window approach has been a natural consideration in such circumstance to have significant reduction in computational cost for the conventional low-order methods such as FDTD method. However, there have not been studies on the high-order methods, especially the SEDG method, based on the moving window approach. We implemented 3D moving window option for wake field calculations on various conducting cavities including the 9-cell TESLA cavity. We will demonstrate the performance of the SEDG simulations on moving window meshes.
UMAN, Manchester
It is necessity to be able to accurately predict the performance of the any proposed baseline accelerator design in which the effects of couplers, trapped modes, Wakefields, realistic machining and alignment errors as well as numerous other important effects have been taken into consideration. Traditionally used numerical schemes (such as Finite element and Finite difference) require vast resources and time, not only that but the inclusion of realistic defects and misalignments into the baseline configuration will prove time consuming as it will potentially require remeshing of the problem. Here we present a mode matching scheme which utilises a globalised scattering matrix approach that allows large scale electromagnetic field calculations to be obtained rapidly and efficiently. The scalar product of all the S matrices used within this paper has been determined analytically and is calculated only once per transition, adding to the efficiency of the calculation. The influence of cell misalignments and cavity perturbations on the main accelerating linacs of XFEL and CLIC are exhibited. The wake-fields in super-structures and segments of entire modules are also presented
UMAN, Manchester
The main linacs of the ILC consist of nine-cell cavities based on the TESLA design. In order to facilitate reaching higher gradients we have re-designed the cavity shape. This leads to a reduction, comparable to several current designs, in both the ratio of the surface electric field to the accelerating field (Es/Ea) and the magnetic field to the accelerating field (Bs/Ea). The bandwidth of the accelerating mode is also optimized. This new shape, which we refer to as the New Low Surface Field (NLSF) design, bears comparison with the Ichiro, Re-entrant and LSF designs.
Rome University La Sapienza, Roma
INFN/LNF, Frascati (Roma)
We discuss the use of non resonant bead pull technique for measuring fields in standing wave accelerating structures. From the Steele perturbation theory, one can derive the relation between the magnitude and phase of the field in the cavity and the complex reflection coefficient. The effect of the bead size, the calibration of the bead and the comparison with the more common resonant techniques are addressed. As an example, we discuss the measurement on a X-band bi-periodic cavity proposed for linearizing emittance at the Frascati photo-injector SPARC.
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
Funding: Institute for Nuclear Studies, Swierk, Poland
The five parameter method of tuning of biperiodic π/2 linear accelerating structure is presented. The method consists in analytical calculation of the five parameters determining the dispersion relation of such structure: two eigen frequencies fa and fc of accelerating and coupling cavities, the first coupling coefficient kac and two second coupling coefficients kaa and kcc, using five measured dispersion frequencies. Usually the process of tuning is based on sets of 3 cavities however, to include directly also the second coupling coeffients kaa and kcc, one should consider sets composed of five cells. For each such set, using the dispersion relation, a set of five equations for five unknowns is solved by successive elimination of unknowns by expressing them in terms of Fa = fa/f π/2. For Fa one obtains biquadratic equation. Coefficients of this equation are expressed as functions of measured quantities: dispersion phases and frequencies. Knowing Fa all other parameters are easily calculated and the Stop Band SB = fa fc . In this way, on each step of building up the structure one can control precision of measurements and the Stop Band.
JLAB, Newport News, Virginia
Tech-X, Boulder, Colorado
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In this paper, we present benchmarking results for high-class 3D electromagnetic (EM) codes in designing RF cavities today. These codes include Omega3P [1], VORPAL [2], CST Microwave Studio [3], Ansoft HFSS [4], and ANSYS [5]. Two spherical cavities are selected as the benchmark models. We have compared not only the accuracy of resonant frequencies, but also that of surface EM fields, which are critical for superconducting RF cavities. By removing degenerated modes, we calculate all the resonant modes up to 10 GHz with similar mesh densities, so that the geometry approximation and field interpolation error related to the wavelength can be observed.
TUB, Beijing
LBNL, Berkeley, California
Funding: Supported by National Natural Science Foundation of China (No.10775080)
An S-band RF deflecting cavity has been developed and applied for measuring the bunch length at Tsinghua Thomson-Scattering X-ray Source (TTX). This paper briefly introduces the 3-cell pi-mode standing-wave deflecting cavity and reports the recent experiments of the beam diagnostics for the photo-cathode RF gun, which produces electron bunches with RMS length around 1-ps. It is also observed that the bunches are lengthened while the total charge increases, showing the strong space charge effect at a low beam energy.
ANL, Argonne
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) injector consists of a linac, a particle accumulator ring (PAR), and a booster synchrotron (booster). The PAR accumulates multiple linac bunches and compresses them into a single bunch for booster injection. Beam energy in the PAR is 325 MeV. Due to its low energy and relatively strong beam-loading effect, beam charge and phase (or timing ) monitoring is critical to the stable operations of rf control loops. We implemented a monitor system with an FPGA processor, which provides both current monitor and stripline fast waveforms. The system provides a bunch charge reading with a data rate of up to 1 MHz and a beam phase resolution of 200 ps, which are sufficient for the rf phase control loops. The system is currently used for beam tuning and diagnostics during normal operation. We are planning to build an upgraded version with fast data output and included it in the new rf control loops. We present a description of the system and the measurement results.
CIAE, Beijing
The beam phase monitor was designed to address phase slide issue, which can lead to significant beam loss inside 100MeV cyclotron. The measured phase information can be used to direct cyclotron magnetic field fine tuning. The system describes in this paper consists of the following part: 10 sets of beam phase pickup, a phase detector, a set of RF multiplexer and a phase shifter to compensate different phase offset generated by cables, connectors etc. The last one is a computer interface consisting of two 16 bits AD converters, one ARM 7 processor was included in this module to support RS232 connection and perform necessary signal process. All parts except the probe were located in one 3U VME standard crate, 8 slots were occupied and one user defined backplane was developed to carry necessary power supply lines and inter-connections. Preliminary tests for the electronic system has been performed, and a good result was obtained in the procedure. Yet the leakage from RF cavity in the 100MeV cyclotron is still an undermined limitation for this application.
CEA, Gif-sur-Yvette
The probe beam linac of the CTF3 test facility, named CALIFES, is developed by the CEA Saclay, the LAL Orsay and CERN to deliver short bunches (0.75 ps) with a charge of 0.6 nC to the CLIC 12 GHz accelerating structures. To setup the machine and obtain a precise beam handling, six high resolution beam position monitors (BPMs), based on a radiofrequency reentrant cavity with an aperture of 18 mm, are installed along the linac. The associated electronics is composed of an analog signal processing electronics with a multiplexing to control the six monitors. Due to mechanical tolerances, dipole mode frequencies are different for each BPMs, 100 MHz IF frequency is, therefore, used so that monitors operate in single and multi-bunches. Digitalised signals from acquisition boards are made available to the operation crew thanks to the OASIS interfaces. In this paper, the BPMs acquisition and the signal post processing, to extract the beam position, will be discussed and first beam tests will be presented.
Far-Tech, Inc., San Diego, California
The emittance exchange experiment planned at the Argonne Wakefiel Accelerator facility will rely on a set of cavity-based beam diagnostics in order to map the transport matrix through the beamline. These will include cavity BPM and time-of-flight diagnostics, as well as quadrupole cavity x-y coupling diagnostics. The measurement system will be designed to fit within compact space requirements, while also maintaining a sufficient clear aperture and sensitivity. The RF design of the system, as well as RF cold-test data for the BPM cavities, is presented.
FSU Jena, Jena
HIT, Heidelberg
GSI, Darmstadt
Funding: This work was supported in part by the Gesellschaft für Schwerionenforschung Darmstadt, Germany.
We describe an LTS SQUID-based high precision measurement tool for nuclear physics. This device makes use of the Cryogenic Current Comparator (CCC) principle and is able to measure e.g. the absolute intensity of a high energy ion beam extracted from a particle accelerator or the so-called dark current, generated by superconductive RF accelerator cavities at high voltage gradients. The CCC mainly consists of a high performance LTS-DC SQUID system, a special toroidal pick-up coil, and a meander-shaped superconductive magnetic ring structure. The design of the CCC requires a thorough knowledge of several noise contributions to achieve a high current resolution. As the SQUID and the pick-up coil are extremely sensitive to external magnetic fields it is necessary to shield both sufficiently against any disturbing field sources. Theoretical investigations showed that with strong attenuation of external noise sources an improvement of the sensor performance is dependent on the ferromagnetic core material imbedded in the pick-up coil. Several materials were investigated and the temperature- and the frequency dependence measured. The current results will be presented and discussed.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
JAEA/LINAC, Ibaraki-ken
In the J-PARC LINAC, BPMs with 4 strip lines (up, down, right, left) have been used to monitor the beam position by taking log ratio of signals on the opposite (facing) sides of stirp lines. We are studying possibility to monitor beam phase by measuring phase of summed signal of all four stlip lines. In this paper, status of the study is presented.
Kyungpook National University, Daegu
Royal Holloway, University of London, Surrey
KEK, Ibaraki
PAL, Pohang, Kyungbuk
UCL, London
SLAC, Menlo Park, California
Fermilab, Batavia
CHEP, Daegu
University of Cambridge, Cambridge
The ATF2 international collaboration is intending to demonstrate nanometer beam sizes required for the future Linear Colliders. The position of the electron beam focused down at the end of the ATF2 extraction line to a size as small as 35 nm has to be measured with nanometer resolution. For that purpose a special Interaction Point(IP) beam position monitor (BPM) was designed. In this paper we report on the features of the BPM and electronics design providing the required resolution. We also consider the results obtained with BPM triplet which was installed in the ATF beamline and the first data from ATF2 commissioning runs.
Ankara University, Faculty of Engineering, Tandogan, Ankara
FZD, Dresden
SDU, Isparta
Funding: State Planning Organization of Turkey
Turkish Accelerator Center (TAC) Infrared (IR) Free Electron Laser facility (FEL) supported by State Planning Organization (SPO) of Turkey will be based on 15-40 MeV energy range electron linac and two different undulators with 2.5 cm and 9 cm period lengths in order to obtain FEL in 2-250 micron wavelength range. The electron linac will consist of two superconducting ELBE modules which houses two 9-cell TESLA cavity in one module and can operate in cw mode. The electron bunches in cw mode which are compatible with the main linac will be provided by a thermionic gun and an injector system which is totally based on normal conducting technology. In this study the injector design for TAC IR FEL is represented and beam dynamics issues were discussed for suitable injection to first accelerating module.
ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
The corrective steering algorithm in TRACK has been recently updated to be more realistic. A simplified formalism will be presented along with the method of implementation. As an important application, the algorithm was used to determine the number of correctors and monitors required for the front-end of the HINS project at Fermilab. The algorithm allowed us also to find the optimum locations for the correctors and monitors as well as the required corrector field strength and the required monitor precision for an effective correction. This correction procedure could be easily implemented in an accelerator control-room for real-time machine operations.
UMAN, Manchester
CERN, Geneva
The upgrade of the normal conducting REX-ISOLDE heavy ion accelerator at CERN, under the HIE-ISOLDE framework, proposes the use of superconducting (SC) quarter-wave resonators (QWRs) to increase the energy capability of the facility from 3 MeV/u to beyond 10 MeV/u. A beam dynamics study of a lattice design comprising SC QWRs and SC solenoids has confirmed the design's ability to accelerate ions, with a mass-to-charge ratio in the range 2.5 < A/q < 4.5, to the target energy with a minimal emittance increase. We report on the development of this study to include the implementation of realistic fields within the QWRs and solenoids. A preliminary error study is presented in order to constrain tolerances on the manufacturing and alignment of the linac.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
MHI, Kobe
The output energy of J-PARC linac is planned to be upgraded from 181 MeV to 400 MeV by adding an ACS (Annular Coupled Structure linac) section. The debuncher system for J-PARC linac is also replaced in this energy upgrade. The new debuncher system will consist of two 972-MHz debuncher cavities with the separate-function configuration. In this configuration, the momentum jitter is corrected with the first debuncher, whereas the momentum spread is controlled with the second debuncher. This configuration is advantageous in simplifying the tuning procedure, and it is also beneficial in reducing the nonlinear effects of the debuncher cavities. In this paper, the beam dynamics design of the debuncher system is presented with some simulation results.
TU Darmstadt, Darmstadt
Funding: Supported by DFG via SFB 634
Operational Experience at the Darmstadt superconducting linac (S-DALINAC) showed unexpected effects on beam dynamics and beam quality. So operators could observe transverse beam deflections by changing phases of the SRF-Cavities. Furthermore there has been occurred a growth of normalized tranverse emittance by a factor of 2. The beam current in the S-DALINAC does not exceed 60 μA so space-charge effects could be eliminated to be the reason for the observations. In this work the effect of misalignment of the SRF-Cavities in the linac has been examined using beam-dynamic simulations with the tracking code GPT and measurements on the electron beam of the S-DALINAC. By measuring the transverse deflection of the beam by changes of the phases of the SRF-Cavities and comparing results with GPT-simulations a misalignment of the 5-cell capture cavity and first 20-cell cavity of several mm in both transverse directions could be found. This misalignment can explain transverse deflections as well as emittance growth. A correction of misalignment has been carried out using the described results. First measurements showed no more emittance growth and less beam-deflections by SRF-Cavities.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
Wire Scanner Monitors (WSMs) and Bunch Shape Monitors (BSMs) are going to be installed in the entrance part of ACS (Annular Coupled Structure) section at the energy upgraded J-PARC linac. WSMs are used to measure transverse beam profiles, and BSMs are used to measure longitudinal beam profiles. Both are used to match beams from upstream SDTL (Separated-type Drift Tube Linac) accelerator cavities to ACS. Only a BSM will be installed in the beggining and the best location for the BSM has been chosen through studies of the tuning schemes.
IHEP Beijing, Beijing
SINAP, Shanghai
RF deflectors can be used for bunch length measurement with high resolution. This paper describes the completed S-band travelling wave RF deflector and the bunch length measurement of the electron beam produced by the photocathode RF gun of Shanghai DUV-FEL facility. The deflector’s VSWR is 1.06, the whole attenuation 0.5dB, and the bandwidth 4.77MHz for VSWR less than 1.1. With laser pulse width of 8.5ps, beam energy of 4.2 MeV, bunch charge of 0.64 nC, the bunch lengths for different RF input power into the deflector were measured, and the averaged rms bunch length of 5.25 ps was obtained. A YAG crystal is used as a screen downstream of the deflector, with the calibrated value of 1pix =136um.
NSCL, East Lansing, Michigan
LBNL, Berkeley, California
Funding: U.S. Department of Energy
A driver linac has been designed for the proposed Facility for Rare Isotope Beam (FRIB) at Michigan State University. FRIB is a lower cost and reduced scope alternative to the Rare Isotope Accelerator (RIA) project. The superconducting driver linac will accelerate stable isotope beams to energies ≥200 MeV/u with a beam power up to 400 kW for the production of rare isotope beams. The driver linac consists of a front-end and two segments of superconducting linac connected by a charge stripping station. End-to-end beam simulation studies with high statistics have been performed using the RIAPMTQ and IMPACT codes on high performance parallel computers. These studies include misalignment of beam elements, rf amplitude and phase errors for cavities, and thickness variation of the stripping foil. Three-dimensional fields of the superconducting solenoids and cavities were used in the lattice evaluation. The simulation results demonstrate good driver linac performance. No uncontrolled beam losses were observed even for the challenging case of multiple charge state uranium beam acceleration. The beam dynamics issues will be discussed and the detail beam simulation results presented.
Northern Illinois University, DeKalb, Illinois
ANL, Argonne
Funding: M.R. and P.P. was supported by the US DOE under Contracts No. DE-FG02-08ER41532 with NIU. W.G. and J.P are supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 with ANL.
Transverse to longitudinal phase space manipulation hold great promises, e.g., as a potential technique for repartitioning the emittances of a beam. A proof-of-principle experiment to demonstrate the exchange of a low longitudinal emittance with a larger transverse emittance is in preparation at the Argonne Wakefield Accelerator using a 15 MeV electron beam. In this paper we explore the limiting effects of this phase space manipulation method associated to high order optics and collective effects. A realistic start-to-end simulation of the planned proof-of-principle experiment including jitter studies is also presented.
TRIUMF, Vancouver
DAE/VECC, Calcutta
TRIUMF proposes a 1/2 MW electron linac (e-linac) for radioactive ion beam production via photofission. The e-linac is to operate CW using 1.3 GHz superconducting (SC) technology. The accelerator layout consists of a 100 keV thermionic gun, a normal conducting buncher, an injector module, and main linac modules accelerating to a final energy of 50 MeV. The design beam current is 10 mA. The beam dynamics of the injector, where electrons make the transition to the fully relativistic state, has been identified as the most critical part of the design and is the subject of simulations (starting at the gun cathode) using realistic EM fields in PARMELA and TRACK. CW operation demands the novel choice of adopting an SC capture section. A preliminary design of the injector foresees a capture section composed either of two independent or two coupled single-cell cavities, beta <1, that increase the energy to about 500 keV, followed by one nine-cell cavity that boosts the energy up to 10 MeV. The design parameters are subjected to a global optimization program. In this paper we present results from the beam dynamics study as well as details and final outcome of the optimization process.
Northern Illinois University, DeKalb, Illinois
Fermilab, Batavia
Funding: Supported by U.S. Department of Energy, under Contract DE-FG02-06ER41435 with Northern Illinois University and by the Fermi Research Alliance, LLC under Contract DE-AC02-07CH11359 with the U.S. D.O.E.
Designs for developing TeV-range electron-positron linear colliders include a non-zero crossing angle colliding scheme at the interaction point to mitigate instabilities and possible background. Maximizing the luminosity when operating with non-zero crossing angles requires the use of "crab" cavities to impart a well-defined spatio-temporal correlation. In this paper we propose a novel non-interceptive diagnostic capable of measuring and monitoring the spatio-temporal correlation, i.e. the transverse position of sub-picosecond time slices, within bunch. An analysis of the proposed scheme, its spatio-temporal resolution and its limitations are quantified. Finally, the design of a proof-of-principle experiment in preparation for the Fermilab's A0 photoinjector is presented.
RCNS, Sendai
KEK, Ibaraki
Tohoku University, School of Scinece, Sendai
We have designed a beam orbit tilt monitor for stabilizing a beam orbit in ATF2. Once we can measure a beam orbit tilt angle with high precision at one point, we can relate this data with the beam position profile at the focal point. This monitor is composed of a single rectangular cavity and waveguides to extract the signal. This monitor can measure the beam orbit tilt with a single cavity. We extract the signal of one basic resonance mode from the cavity. This electric field mode is perpendicular to the nominal beam axis, and is excited by beam tilt. The magnitude of extracted signal gives us the beam tilt data. According to our simulation, the expected sensitivity is about 30 nrad.
UCL, London
Royal Holloway, University of London, Surrey
Cavity beam position monitors (CBPM) made a significant progress in the last 10 years with an entire nano-beamline relying on them being currently commissioned at ATF2 (KEK). The major improvement was the introduction of the mode selective coupling allowing for efficient rejection of unwanted monopole modes. We propose another step towards creating a simple and cost effective CBPM - a cavity using just one coupler (instead of 2 or even 4) to couple out both polarisations of the dipole mode. The x and y signals are then split in the mixing stage of the electronics, so that only one expensive high-frequency electronics front-end is used for both x and y. A very good separation of the x and y signals can be achieved with a reasonable performance mixer assembly. In this paper we present the concept and provide some simulation results proving this processing scheme.
UCL, London
Royal Holloway, University of London, Surrey
Kyungpook National University, Daegu
KEK, Ibaraki
SLAC, Menlo Park, California
Fermilab, Batavia
University of Cambridge, Cambridge
The ATF2 international collaboration is intending to demonstrate nanometre beam sizes required for the future Linear Colliders. An essential part of the beam diagnostics needed to achieve this goal is the high resolution cavity beam position monitors (BPMs). In this paper we report on the S-band system installed in the final focus region of the new ATF2 extraction beamline. It only includes 4 BPMs, but they are mounted on the most critical final focus magnets squeezing the beam down to 35 nm. We discuss both the design and the first operational experience with the system.
Royal Holloway, University of London, Surrey
Kyungpook National University, Daegu
KEK, Ibaraki
UCL, London
SLAC, Menlo Park, California
Fermilab, Batavia
University of Cambridge, Cambridge
The ATF2 international collaboration is intending to demonstrate nanometre beam sizes required for the future Linear Colliders. An essential part of the beam diagnostics needed to achieve that goal is the high resolution cavity beam position monitors (BPMs). In this paper we report on the C-band system consisting of 32 BPMs spread over the whole length of the new ATF2 extraction beamline. We discuss the design of the BPMs and electronics, main features of the DAQ system, and the first operational experience with these BPMs.
BINP SB RAS, Novosibirsk
The VEPP-4M electron-positron collider is now operating with the KEDR detector for high-energy physics experiments in the 1.5−2.0 GeV beam energy range. Parallel with these experiments, the VEPP-4M scientific team carries out a number of accelerator physics investigations. A new registration system for the Touschek polarimeter has been put into operation. A new NMR-based system for suppression of the guide field ripples has been developed. The counting rate of the Touschek particles has been measured as a function of the beam energy in the range from 1.85 to 4 GeV. The measurement results can be claimed at the future super B and C-Tau factories. For simultaneous measurement of the transverse beam position and inclination angle an X-ray multi-pinhole camera has been designed, manufactured and installed at the VEPP-4M. To suppress the longitudinal instability caused by high-order modes of the RF cavities, a feedback system has been developed.
SLAC, Menlo Park, California
Funding: Operated by Stanford University for the U. S. Department of Energy under Contract DE-AC02-76-SF00515 and Office of Basic Energy Sciences.
The Bergoz Instrumentation New Parametric Current Transformer (NPCT) has been evaluated at the SPEAR3 synchrotron light source. The device was tested for vacuum performance and residual gas and was found suitable for installation in the storage ring. The NPCT was installed during August 2008 and has measured beam currents to 500 mA. Performance is compared to the earlier PCT design. The NPCT Sensor Head has been instrumented with thermal sensors for characterization of the internal operating temperature.
RIKEN Spring-8 Harima, Hyogo
JASRI/SPring-8, Hyogo-ken
RIKEN/SPring-8, Hyogo
In XFEL/SPring-8, it is very important to generate an electron beam, having a low slice emittance of 0.7 pimm-mrad, a pulse width of 30 fs, and a peak current of 3 kA at an X ray lasing part. For tuning such beam to guarantee stable X ray laser generation, beam and laser monitors to diagnose the temporal structure of them are an indispensable function. The monitors, such as a beam position monitor (BPM), a TM11-mode rf beam deflector and a screen monitor (SCM), have been developed to satisfy the function. The BPM has a position resolution of less than 1 um. The SCM to observe the beam deflecting image has a position resolution of 2.5 um. The design of a longitudinal beam diagnosis system using the monitors showed that it can measure a temporal structure with a resolution of 0.5 fs along the beam pulse. The experiment to check feasibility of the BPM showed that it can work as a beam arrival timing monitor with a temporal resolution of 46 fs. A monitor system using an in-vacuum photo diode was also developed to measure the laser arrival timing, and showed ability to resolve a 2 ps time jitter. These temporal resolutions allow us fine beam tuning required for the XFEL.
UCR, Riverside, California
The Muon Ionization Cooling Experiment (MICE) is being built at the Rutherford Appleton Laboratory (RAL) to test ionization cooling of a muon beam. Successful demonstration of cooling is a necessary step along the path toward creating future high intensity muon beams in either a neutrino factory or muon collider. MICE will reduce the transverse emittance of the beam by 10%, and spectrometers using particle physics techniques will measure the emittance reduction with an absolute precision of 0.1%. This measurement will be done with scintillating fiber tracking detectors nested inside solenoid magnets on either side of the cooling channel. Each fiber tracker contains five stations with 3 layers of fibers rotated 120 degrees with respect to each other, thereby allowing reconstruction of hit points along the path of the muons. Light is carried from the active fiber volume by clear waveguide fibers where it is detected using VLPCs (Visible Light Photon Counters). The details of the tracker commissioning using cosmic rays will be discussed in addition to the status and performance of the readout electronics*.
*Submitted on behalf of the MICE collaboration.
USTC/NSRL, Hefei, Anhui
Funding: National “985 Project” （173123200402002); National Natural Science Foundation(10875117)
A new high brightness injector is planned to be installed at HLS, NSRL. It is based on a new photocathode RF electron gun. To steer the beam along the optimal trajectory, higher precision controlling of beam position is required. The positional resolution of the BPM system designed for the new RF gun should be higher than 10 μm. A new cavity BPM design is then given instead of old stripline one because of its higher positional resolution. In a normal symmetrical pill-box BPM design, machining tolerance will result in x-y coupling, which will cause cross-talk problem. A novel design is then presented here. To solve the problem before, a position cavity which has a racetrack cross section is used instead of a pill-box one. The ideal resolution of this design could be less than 3 nm.
USTC/NSRL, Hefei, Anhui
A high brightness injector has been developing in HLS (Hefei Light Source), and the design of beam parameter measurement system is presented in this paper. The whole system will measure beam position, beam current, emittance of beam, bunch length, beam energy and energy spread. For the beam position, we have designed three types of BPMs: stripline BPM, with the resolution of 20 μm; cavity BPM, with the resolution of 10 μm, and resonant stripline BPM*. The beam position processor Libera will be used. The beam current will measured using the ICT and FCT. When going out of the gun, the energy of the beam is about 4MeV 5MeV, and the emittance of the beam is charge-dominated, so we use a set of slits with the width of 90 μm to split the beam to beamlets. The bunch length is measured using OTR and streak camera. Before entering the bending magnet, the beam will go pass a very narrow slit, with the width of 90 μm, and the resolution of energy spread will be improved.
*M.Dehler, “Resonant Strip line BPM for Ultra Low Current Measurements”, Proceedings of DIPAC 2005, Lyon, France, p.286-288
ELETTRA, Basovizza
DEEI, Trieste
Funding: The work was supported in part by the Italian Ministry of University and Research under grant FIRB-RBAP045JF2.
Travelling wave and standing wave deflectors are well known RF devices that nowadays are used in particle accelerators as a beam diagnostic tool. They will also be implemented in FERMI@Elettra project, a soft X-ray fourth-generation light source under development at the ELETTRA laboratory, and used to completely characterize the beam phase space by means of measurements of bunch length and transverse slices emittance. In particular, one deflector will be placed at low energy (250MeV) and another at high energy (1.2GeV), just before the FEL process starts. In this note we collect our experience and simulation on this last device, making a comparison between the most relevant options we have considered to satisfy our RF and space constraints. Basic cell design is discussed for both the travelling and standing wave choice. In particular, two different modes, the 2/3π and the 5/6π, are analyzed for the travelling wave option while an 11 cells design in π mode is presented for the standing wave case. For both cases sensitivity analysis and other relevant RF parameters are given.
FEL/Duke University, Durham, North Carolina
PAL, Pohang, Kyungbuk
Dimtel, San Jose
Funding: work supported by US Air Force Office of Scientific Research medical FEL grant FA9550-04-01-0086
The coupled bunch mode instabilities (CBMIs) caused by vacuum chamber impedance limit and degrade the performance of the storage ring based light sources. A bunch-by-bunch longitudinal feedback (LFB) system has been developed to stabilize beams for the operation of a storage ring based Free Electron Laser (FEL) and the High Intensity Gamma-ray Source (HIGS) at the Duke storage ring. Employing a Giga-sample FPGA based processor (iGP), the LFB is capable of damping out the dipole mode oscillation for all 64 bunches. As a critical subsystem of the LFB system, kicker cavity is developed with a center frequency of 938 MHz, a wide bandwidth (> 90 MHz), and a high shunt impedance (> {10}00 Ω). First commissioned in summer 2008, the LFB has been operated to stabilize high current multi-bunch operation. More recently, the LFB system is demonstrated as a critical instrument to ensure stable operation of the HIGS with a high intensity gamma beam above 20 MeV with a frequent top-off injection to compensate for the substantial and continuous electron beam loss in the Compton scattering process. In the future, we will perform detailed studies of the impedance effects using the LFB system.
ANL, Argonne
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
The Argonne Advanced Photon Source is in the process of developing a short-pulse x-ray (SPX) beamline capable of producing picosecond-scale x-ray pulses for use in time-resolved studies. To accomplish this, transverse deflecting cavities (crab cavities) operating at eight times the storage ring rf will be installed to enable production of short x-ray pulses at a selected beamline. Analysis reveals demanding phase and amplitude stability requirements for the cavity fields. The common-mode cavity field phase error relative to bunch arrival time is ± 10 degrees at the 2815-MHz cavity frequency while the cavity-to-cavity phase difference must be held to ± 0.07 degrees. The phase differential between the cavity phase and beamline timing must be held to ± 1 picosecond. A phase stabilized link* is being developed to transport a phase stable 351.9-MHz reference to the LLRF located at the beamline end. The delivered phase-stable reference will be used to develop rf references for the cavity LLRF, beamline laser, and streak camera. This paper will discuss the details of the design and report measured performance of the prototype.
* J. Frisch, D. Bernstein, D. Brown, E. Cisnerso, “A High Stability, Low Noise RF Distribution System,“ Proceedings of PAC2001, pp 816-818.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Excellent phase stability of the drive laser is a critical performance specification of photoinjectors such as Fermilab’s A0 photoinjector (A0PI). Previous efforts based on the measurement of the power spectrum of the signal of a fast photodiode illuminated by the mode locked infra-red laser pulse component indicated a phase jitter of less than 1.4 ps (technique limited). A recently procured dual-sweep plugin unit and existing Hamamatsu C5680 streak camera were used to study the phase stability of the UV laser pulse component. Initial measurements with the synchroscan vertical sweep unit locked to 81.25 MHz showed that the phase slew through the micropulse train and the phase jitter micropulse to micropulse were two key aspects that could be evaluated. The phase slew was much less than 100 fs per micropulse, and the total phase jitter (camera, trigger, and laser) was approximately 300 fs RMS for measurements of 20-micropulse trains. Data on the macropulse phase stability were also obtained. A possible upgrade to achieve better phase stability will be also discussed.
NSRRC, Hsinchu
The 266 nm UV drive laser for the NSRRC 2998 MHz photo-injector system is generated from a nonlinear optical crystal that is driven by a 798 nm, 3.5 mJ Ti:Sapphire laser amplifier system. Synchronization of the seed laser pulses with the master oscillator of the photo-injector high power microwave system is done by locking the laser to the rf clock signal with time jitter of less than a picosecond. A detector circuit is being built to measure this jitter at sub-picosecond time resolution. Preliminary results of this jitter measurement electronics that have been tested with artificial signals are presented.
SLAC, Menlo Park, California
Funding: Work supported by U.S. Department of Energy under Contract Nos. DE-AC02-06CH11357 and DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) project at SLAC uses a dense 15 GeV electron beam passing through a 131m undulator to generate extremely bright xrays. The project requires electron bunches with a bunch charge of 20pC to 1nC and bunch lengths of 0.020mm (70fs).To measure the beam resolution to 1 micron (rms) for bunch charge > 20 pC in the undulator, a cavity BPM system was chosen. This system can measure the beam position to within a micron. The LCLS Cavity BPM local oscillator subsystem consists of a second order phase-locked loop (PLL) to synchronize with LCLS timing system and injector system. The output of the PLL is distributed to 36 Cavity BPM receivers and 36 high speed digitizers while maintaining good phase noise and low jitter. This paper describes the design of the PLL and how it met the design specifications of 0.1 degree of phase noise at 119MHz and 1 ns of rms jitter.
JLAB, Newport News, Virginia
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Jefferson Lab’s CEBAF accelerator operation requires various frequency signals to be distributed along the site. Three signals: 10 MHz, 70 MHz and 499 MHz are synthesized in the Machine Control Center (MCC) while 1427 MHz and 429 MHz are derived from 499 MHz and 70 MHz signals in four separate locations. We are replacing our obsolete 10 MHz, 70 MHz and 499 MHz sources with new sources that will incorporate a GPS receiver to discipline a 10 MHz reference. In addition the MO (Master Oscillator) system will be redundant (duplicate MO) and a third signal source will be used as a system diagnostic. Moreover the 12 GeV Energy Upgrade for CEBAF accelerator will be adding 80 new RF systems. To support them the distribution of 1427 MHz and 70 MHz signals has to be extended and be able to deliver enough LO (Local Oscillator) and IF (Intermediate Frequency) power to 320 old and 80 new 80 RF systems. This paper discusses the new MO and the drive line extension.
SLAC, Menlo Park, California
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
JAI, Oxford
KEK, Ibaraki
IHEP Beijing, Beijing
LAL, Orsay
Royal Holloway, University of London, Surrey
IN2P3-LAPP, Annecy-le-Vieux
OXFORDphysics, Oxford, Oxon
ATOMKI, Debrecen
CERN, Geneva
DESY, Hamburg
Fermilab, Batavia
Kyungpook National University, Daegu
PAL, Pohang, Kyungbuk
Kyoto ICR, Uji, Kyoto
ICEPP, Tokyo
University of Tokyo, Tokyo
UCL, London
BNL, Upton, Long Island, New York
Tohoku University, Graduate School of Science, Sendai
UMAN, Manchester
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
Cockcroft Institute, Warrington, Cheshire
ATF2 is a final-focus test beam line that attempts to focus the low-emittance beam from the ATF damping ring to a beam size of about 37 nm, and at the same time to demonstrate nm beam stability, using numerous advanced beam diagnostics and feedback tools. The construction is well advanced and beam commissioning of ATF2 has started in the second half of 2008. ATF2 is constructed and commissioned by ATF international collaborations with strong US, Asian and European participation.
CAEP/IFP, Mainyang, Sichuan
TUB, Beijing
CAEP/IAE, Mianyang, Sichuan
It has been three decades since the research and development of key technologies and components started at the Institute of Fluid Physics, CAEP, for the linear induction accelerator (LIA). The first LIA was built in 1989 with beam parameters of 1.5 MeV, 3 kA and pulse width of 90 ns. Later the SG-I LIA (3.3 MeV, 2 kA, 90 ns) was developed for FEL in 1991. The first Linear Induction Accelerator X-Ray Facility (LIAXF, 10 MeV, 2 kA, 90 ns, spot size about 6 mm in diameter) was built in 1993 and upgraded to 12 MeV with higher performance (LIAXFU, 12 MeV, 2.5 kA, 90 ns, spot size about 4 mm in diameter) in 1995. The Dragon-I LIA with the best quality (20 MeV, 2.5 kA, 80 ns, spot size about 1 mm in diameter) in the world was finished in 2003. The smallest LIA with double pulses separated by 300 ns (MiniLIA, 200 keV, 1 A, 80 ns) was developed in 2007 for beam physics studies.
GANIL, Caen
The SPIRAL 2 superconducting linac is currently under construction. This talk describes the collaboration effort with industrial partners to fabricate the two cryomodule families: the low beta Cryomodule A, and the high beta Cryomodule B. The low beta family is composed of 12 single cavity cryomodules. The high energy section is composed of 7 cryomodules hosting 2 cavities each. The design goal for the accelerating field Eacc of the SPIRAL 2 QWRs is 6.5 MV/m.
Fermilab, Batavia
Funding: This work was supported by the Fermi National Accelerator Laboratory, which is operated by Universities Research Association, under contract No.DE-AC02-76CH03000 with the U.S. Department of Energy
This talk will present arguments that the Neutrino Factory - an extremely intense source of flavor-tagged neutrinos from muon decays in a storage ring - gives the best physics reach for CP violation, as well as virtually all parameters in the neutrino oscillation parameter space. It will describe the physics capabilities of a baseline Neutrino Factory as compared to other possible future facilities (beta-beam and super-beam facilities), give an overview of the accelerator complex, describe the current international R&D program and present a potential time line for the design and construction of the facility. Although the baseline study focuses on a facility with muon energy of 25 GeV, a concept for a Low-Energy (~ 4 GeV) Neutrino Factory has also been developed and its physics reach will also be discussed. Finally, it will be shown that a facility of this type is unique in that it can present a physics program that can be staged, addressing exciting new physics at each step. Eventually it can lead to an energy-frontier muon collider. A muon accelerator facility is a natural extension that can exploit the high intensity potential at FNAL starting with Project X.
DESY, Hamburg
Fermilab, Batavia
KEK, Ibaraki
With a now extended plan to 2012, the ILC Global Design Effort Technical Design Phase focuses on key R&D to verify performance goals and to reduce both technical risk and cost. This talk will review the progress during the last two years, and plans for the future.
KEK, Ibaraki
KURRI, Osaka
Harmonic number jump (HNJ) acceleration in scaling FFAG accelerator, especially for muon acceleration in neutrino factory, has been studied. Criterions for HNJ acceleration were clarified and beam tracking simulations have been carried out.
CLASSE, Ithaca, New York
Commissioning of a new high brightness electron source for the Energy Recovery Linac at Cornell University is currently underway. Despite the fact that the beam dynamics in this portion of the accelerator is space-charge dominated, a fundamental understanding of the machine linear optics is crucial in that it determines the effectiveness of space-charge emittance compensation methods, as well as provides the means to achieving various beam parameters such as beam length and energy spread. Here we introduce a new numerical tool being used in the commissioning of the injector that provides linear optics matrix calculation using field maps for various optical elements.
Rutgers University, The State University of New Jersey, Piscataway, New Jersey
Fermilab, Batavia
BNL, Upton, Long Island, New York
A transverse to longitudinal emittance exchange experiment is installed at the Fermilab A0 Photoinjector. We report on the completed measurement of emittance exchange transport matrix as well as the ongoing program to directly measure the emittance exchange. Both the transverse and longitudinal input beam parameters are being explored in order to achieve direct emittance exchange with minimal dilution effects
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Using an FFAG for rapid-cycling proton acceleration has the advantage that the acceleration cycle is no longer subject to constraints from the main magnet power supply used in an RCS. The RF can be used to its maximum potential to increase the energy range in a short 50Hz cycle as proposed for multi-MW proton driver projects. The challenge becomes an optical one of maintaining a stable lattice across a wide range of beam momenta without magnet sizes or the ring circumference making the machine prohibitively expensive for its purpose. Investigations of stable energy ranges for proton FFAG lattices in the few GeV regime (relativistic but not ultra-relativistic) are presented here.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Results of designing of the extended ALICE injector with the aim to include a special dedicated diagnostic line are presented. The purpose of the diagnostic line is to characterise the low energy beam, before it enters the booster, as much as possible. A key component of the ALICE is the high brightness injector. The ALICE injector consists of a DC photocathode gun generating ~ 80 pC electron bunches at 350 keV. These bunches are then matched into a booster cavity which accelerates them to an energy of 8.35 MeV. In order to do this, three solenoids and a single-cell buncher cavity are used, together with the off-crest of the first booster cavity where the beam is still far from being relativistic. The performance of the injector has been studied using the particle tracking code ASTRA.
UCR, Riverside, California
Funding: Work supported by the United States Department of Energy under Grant No. DE-FG02-07ER41487.
The RFOFO ring is considered to be one of the most promising six-dimensional cooling channels proposed for the future Muon Collider. It has a number of advantages over other cooling channels, but also certain drawbacks. The injection and extraction, the absorber overheating, and the bunch train length are among the main issues. A number of simulations of a possible solution to these problems, the RFOFO helix, commonly referred to as the Guggenheim channel, were carried out and their results are summarized. The issue of the RF breakdown in the magnetic field is addressed, and the preliminary results of the simulation of the lattice with magnetic coils in the irises of the RF cavities are presented.
ELETTRA, Basovizza
Funding: "The work was supported in part by the Italian Ministry of University and Research under grant FIRB-RBAP045JF2 or grant FIRB-RBAP06AWK3 or grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3"
FERMI@Elettra is a FEL user facility under construction at Sincrotrone Trieste, Italy. It will use the existing normal conducting S-band Linac and seven accelerating sections received from CERN after the LIL decommissioning. Two additional new sections are also foreseen. The Linac repetition rate will be 10 Hz during the initial stage of operation, but it will be ramped up from 10 Hz to 50 Hz. Due to the higher RF power dissipation, the temperature distribution on the copper structure will reach higher values. RF heating will imply a thermal deformation of the accelerating cavities, both in the transversal and in the longitudinal direction. Since FERMI@Elettra has stringent requirements on phase stability, the length of the section must be kept as constant as possible. In this paper the thermo-mechanic behaviour of the accelerating sections is investigated and the results of the simulations are presented. Furthermore an algorithm has been developed to control the longitudinal deformation of the sections.
UCLA, Los Angeles, California
INFN/LNF, Frascati (Roma)
Rome University La Sapienza, Roma
A hybrid photoinjector, which we present here, consists of a 6-cell traveling wave structure with a standard 1.6-cell RF gun attached to the one end and a 3-m long linac following for further acceleration. With this structure, no reflection observed at the input port. This enables to build the accelerator without a circulator which limits the power and the frequency of RF. From the beam dynamics point of view, the beam is produced as the normal RF guns and gets short by velocity bunching in the traveling wave section right after the gun. The peak current can reach more than 1 kA, with about 2 mm.mrad of the emittance at 20 MeV. We discuss more details about the beam dynamics as well as the RF structure.
SLAC, Menlo Park, California
JLAB, Newport News, Virginia
Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and used resources of NERSC supported by DOE Contract No. DE-AC02-05CH11231, and of NCCS supported by DOE Contract No. DE-AC05-00OR22725.
SLAC has developed a multi-physics simulation code TEM3P for simulating integrated effects of electromagnetic, thermal and structural effects. TEM3P shares the same finite element infrastructure with EM finite elements codes developed at SLAC. This enables simulations within a single framework. Parallel implementation allows large scale computation, and high fidelity and high accuracy simulations can be performed in faster time. In this paper, TEM3P is used to analyze thermal loading in the coupler end-groups of the JLAB SCRF cavity. The results are benchmarked against measurements.
TRIUMF, Vancouver
DAE/VECC, Calcutta
SFU, Burnaby, BC
ANL, Argonne
The TRIUMF ARIEL Project plans to build a 50MeV electron linac at 10mA to produce radioactive ion beams through photofission. Beam dynamics studies of the accelerator are on-going. The TRACK code originally written to simulate proton and heavy ion linacs has been used in e-linac modeling studies. This paper will summarize the TRACK simulation studies and the simulation results will be compared with other codes like PARMELA and ASTRA.
MEPhI, Moscow
TRIUMF, Vancouver
The results of 3D multipacting simulation in coaxial superconducting quarter wave cavities of the linear accelerator of heavy ions ISAC-II are presented. The multipacting simulation was done using MultP-M code. Dangerous areas of structure and levels of an accelerating field are revealed. Examples of electrons resonant trajectories are presented. Simulation results are compared with experimental results obtained during several superconducting cavities processing.
Tech-X, Boulder, Colorado
Funding: Supported in part by the DOE Office of Science, Office of High-Energy Physics under grant No. DE-FG02-06ER84485.
We present realistic models, including fringes, for several standing-wave modes in rf cavities. These models include a simple accelerating mode and a TM-110 (crab) mode. They are useful for the accurate computation of transfer maps* as well as for constructing model fields that can be used for testing and comparing a variety of rf cavity codes.
*D.T. Abell, "Numerical computation of high-order transfer maps for rf cavities", Phys. Rev. ST Accel. Beams 9, 052001, (2006).
Tech-X, Boulder, Colorado
Fermilab, Batavia
CIPS, Boulder, Colorado
Funding: US DOE, COMPASS SciDAC-2, Grant Number DE-FC02-07ER41499
We have applied the Werner-Cary method* for extracting modes and mode frequencies from time-domain simulations of crab cavities, as are needed for the ILC and the beam delivery system of the LHC. This method for frequency extraction relies on a small number of simulations and post-processing using the SVD algorithm with Tikhonov regularization. The time domain simulations were carried out using the VORPAL computational framework, which is based on the eminently scalable finite-difference time-domain algorithm. A validation study was performed on an aluminum model of the 3.9 GHz RF separators built originally at Fermi National Accelerator Laboratory in the US. Comparisons with measurements of the A15 cavity show that this method can provide accuracy to within 0.01% of experimental results after accounting for manufacturing imperfections. To capture the near degeneracies two simulations requiring in total a few hours on 600 processors were employed. This method has applications across many areas including obtaining MHD spectra from time-domain simulations.
*J. Comp. Phys. 227, 5200-5214 (2008)
Tech-X, Boulder, Colorado
Funding: DoD FA9451-07-C-0025
This work introduces a conformal finite difference time domain (CFDTD) method as implemented in VORPAL to accurately and efficiently study RF cavities. For illustration, an A6 magnetron cavity has been employed and the corresponding dispersion relation has been carried out. The accuracy of the CFDTD method is measured by comparing with SUPERFISH calculations. To verify the accuracy of the CFDTD simulations, a geometric model has been constructed in VORPAL and simulated with different mesh numbers as 10,000, 40,000, 90,000, 160,000, and 250,000 for three DMFRAC values equal to 0.75, 0.5 and 0.25, respectively. The results show an accuracy of 99.4% can be achieved by using only 10,000 meshes with Dey-Mittra algorithm. By comparison, a mesh number of 360,000 need be used to preserve an accuracy of 99% in the conventional FDTD method. One should be careful using conventional FDTD to study systems with complicated geometry as the staircased meshes fail to conform the boundary correctly. The simulation time of studying the interaction of particles with fields inside cavities can be dramatically reduced by using CFDTD particle-in-cell simulation without losing accuracy.
* C. Nieter, J. R. Cary, J. Comput. Phys. 196, 448-473 (2004).
** S. Dey, R. Mittra, and S. Chebolu, Microwave and Opt. Technol. Lett. 14, 213-215 (1997).
Tech-X, Boulder, Colorado
Funding: This project was in part supported by DOE Office of Advanced Scientific Computing Research SBIR Phase II grant #DE-FG02-07ER84731, SciDAC Grant #DE-FC02-07ER41499, and Tech-X Corporation.
In order to meet the design and budget constraints of next generation particle accelerators, individual components have to be optimized using numerical simulations. Among the optimizations are the geometric shape of RF cavities and the placement of coupler and dampers, requiring large numbers of simulations. It is therefore desirable to accelerate individual cavity simulations. Finite-Difference Time-Domain (FDTD) is a widely used algorithm for modeling electromagnetic fields. While being a time-domain algorithm, it can also be used to determine cavity modes and their frequencies. Weak scaling of parallel FDTD yields good results due to the algorithm locality, but the maximum speedup is determined by the usually small problem size. Graphics Processing Units (GPUs) offer a huge amount of processing power and memory bandwidth, well suited for accelerating FDTD simulations. We therefore developed an FDTD solver on GPUs and incorporated it into the plasma simulation code VORPAL. We will present GPU accelerated VORPAL simulations, provide speedup figures and address the effect of running these simulations in single precision.
Tech-X, Boulder, Colorado
JLAB, Newport News, Virginia
Funding: Department of Energy SBIR grant DE-FG02-05ER84172
We will present the results of benchmarking simulations run to test the ability of VORPAL to model multipacting processes in Superconducting Radio Frequency structures. VORPAL is an electromagnetic (FDTD) particle-in-cell simulation code originally developed for applications in plasma and beam physics. The addition of conformal boundaries and algorithms for secondary electron emission allow VORPAL to be applied to multipacting processes. We start with simulations of multipacting between parallel plates where there are well understood theoretical predictions for the frequency bands where multipacting is expected to occur. We reproduce the predicted multipacting bands and demonstrate departures from the theoretical predictions when a more sophisticated model of secondary emission is used. Simulations of existing cavity structures developed at Jefferson National Laboratories will also be presented where we compare results from VORPAL to experimental data.
Tech-X, Boulder, Colorado
Funding: Supported in part by the DOE Office of Science, Office of High-Energy Physics under grant No. DE-FG02-06ER84485.
We present our recently developed capability for generating High-Order Mode (HOM) maps of rf cavity fields for use in particle tracking code-based simulations. We use VORPAL field data as a starting point, and follow the approach of* to produce the maps that are subsequently incorporated into the MaryLie/IMPACT and Synergia frameworks. We present and discuss the results of applying this new modeling tool to crab cavity simulations.
*D.T. Abell, "Numerical computation of high-order transfer maps for rf cavities", Phys. Rev. ST Accel. Beams 9, 052001, (2006).
TEMF, TU Darmstadt, Darmstadt
We report on a new numerical technique for the computation of geometrical wakes in three-dimensional LINAC structures. The method utilises an explicit Finite-Volume Time-Domain (FVTD) formulation. The numerical dispersion in all three axial directions is completely eliminated by choice of an appropriate staggering of the field components on the grid. Thus, contrary to most of the previously reported techniques no splitting of the time-evolution operator is necessary. This results in large savings in computational time as well as in an improved numerical accuracy. We have implemented this new technique in PBCI code and present some preliminary results.
JLAB, Newport News, Virginia
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
With the proposal of medium to high average current accelerator facilities the demand for cavities with extremely low HOM impedances is increasing. Modern numerical tools are still under development to more thoroughly predict impedances that need to take into account complex absorbing boundaries and lossy materials. With the usually large problem size it is preferable to utilize massive parallel computing when applicable and available. Apart from such computational issues, we have developed methods using available computer resources to enhance the information that can be extracted from a cavities’ wake potential computed in time domain. In particular this is helpful for a careful assessment of the extracted RF power and the mitigation of potential beam breakup or emittance diluting effects, a figure of merit for the cavity performance. The methods are described as well as examples of their implementation.
University of Delhi, Delhi
Fermilab, Batavia
It is well known that Insertion of a coupler into a RF cavity breaks the rotational symmetry of the cavity, resulting in an asymmetric field. This asymmetric field results in a transverse RF Kick*. This RF kick transversely offsets the bunch from the nominal axis & it depends on the longitudinal position of the particle in the bunch. Also, insertion of coupler generates short range transverse wake field** which is independent from the transverse offset of the particle. These effects cause emittance dilution and it is thus important to study their behavior & possible correction mechanisms. These coupler effects, i.e. coupler’s RF kick & coupler's wake field are implemented in a beam dynamics program, Lucretia. Calculations are done for Main Linac. For ILC like Lattices Results are compared with analytical results. and a good agreement has been found.
*N.Solyak et al, “RF Kick in the ILC Acceleration Structure. ” MOPP042.pdf (EPAC 08).
** N.Solyak et al, “Transverse Wake Field Simulation for the ILC Acceleration Structure”. MOPP043 pdf (EPAC 08).
ANL, Argonne
Euclid TechLabs, LLC, Solon, Ohio
Technion, Haifa
Funding: DOE
Particle Acceleration by Stimulated Emission of Radiation (PASER) is method of particle acceleration in which a beam gains energy from an active medium through stimulated emission. To obtain the required sitmulated emission for the PASER effect the particle beam intensity is modulated at the frequency corresponding to the energy difference between the levels in which population inversion is achieved in the active medium. We propose to use solid-state active medium based on the Zeeman effect (triplet systems) for the PASER. Modulation of the beam at the frequency of the transition to obtain stimulated emission can be produced by means of a deflecting cavity. A transverse "beamlet" pattern will be produced on the AWA photocathode gun by using a laser mask. The transverse beam distribution will be transformed into a longitudinal beam modulation as the beam passes through the deflecting cavity. In this paper we report on the development of active media and the first RF bench test.
CIPS, Boulder, Colorado
Funding: This work is supported by the U.S. Department of Energy grant DE-FG02-04ER41317.
Through computer simulation, a 2D photonic crystal (PhC) cavity formed from a truncated triangular lattice of dielectric rods is optimized to confine a single accelerating mode efficiently. Photonic crystals have the ability to reflect radiation within only certain frequency ranges, called bandgaps; the bandgaps are determined by the geometry and material of the PhC and so are tunable. For truncated PhCs, reflection is incomplete. Therefore, the confinement of bandgap frequencies to a cavity within a truncated PhC is weakened by the severity of the truncation. For a cavity made of 18 dielectric rods in a truncated triangular lattice arrangement, the desired accelerating cavity mode is weakly confined. Adjusting the positions and sizes of the dielectric rods away from the best lattice configuration within an optimization procedure gives unintuitive structures, ultimately increasing the confinement of the accelerating mode by a factor of 100. Confinement of higher-order modes is also dramatically reduced by the optimization. Similar increases in confinement of the fundamental accelerating mode are found for a 24-rod structure.
CERN, Geneva
MPI-P, München
Short high-energy proton bunches have been proposed as efficient drivers for future single-stage electron-beam plasma accelerators. We discuss if and how the desired proton bunches could be obtained in the CERN accelerator complex, considering various compression schemes, such as a fast non-adiabatic lattice change prior to extraction from a storage ring or the use of transversely deflecting cavities.
PBPL, Los Angeles
UCLA, Los Angeles, California
Manhattanville College, Purchase, NY
The millimeter-scaleμAccelerator Platform (MAP)–essentially a “particle accelerator on a chip”–will ultimately allow for revolutionary medical and industrial applications due to its manageable size and reproducibility. The MAP consists of an electron source and an all-dielectric, laser powered, particle accelerator. The dielectric structure has two slab-symmetric reflecting mirrors with a vacuum gap between them. A periodic coupling mechanism allows laser power to enter transversely through one mirror. This mechanism is analogous to the slots of an optical diffraction grating, with coupling period and vacuum gap equal to the wavelength of the laser (800nm in this study). Work to date has included designing, fabricating and testing a prototype relativistic structure using a patterned gold layer. To go further, we have studied the fabrication techniques and electromagnetic designs of an all-dielectric (non-metallic) structure. Fabrication of the final structure is modeled after Vertical-Cavity Surface-Emitting Lasers (VCSEL) and Distributed Bragg Reflector (DBR) techniques. Preliminary numerical studies of the sub-relativistic structure are also presented.
UTNL, Ibaraki
RLNR, Tokyo
The University of Tokyo, Nuclear Professional School, Ibaraki-ken
SUT, Noda-shi, Chiba
An all-optical inverse Compton gamma-ray source is enable us to make a tabletop monochromatic gamma-ray source that might be applied to measure an amount of nuclear material, etc. An intense laser pulse excites a very nonlinear plasma wave and accelerate electron bunch up to several-hundreds MeV within a length of a few millimeters. The key to success is stabilization of the laser-plasma accelerators. We are developing the artificial injection technique of initial electrons in to the plasma wave and guiding of the intense laser pulse by the preformed plasma channel.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
Couples bunch longitudinal instability in the presence of high frequency impedance is considered. A frequency domain technique is developed and compared with simulations. The frequency domain technique allows for absolute stability tests and is applied to the problem of longitudinal stability in RHIC with the proposed 56 MHz rf system.
BNL, Upton, Long Island, New York
Impedance of two vacuum chamber components, Bellows and BPM, is considered in some detail. In order to avoid generation of Higher-Order Modes (HOM’s) in the NSLS-II bellows, we designed a new low-impedance RF shielding consisting of 6 wide and 2 narrow metal plates without opening slots between them. The short-range wakepotential has been optimized taking into account vertical offset of RF fingers from their nominal position. The results were compared with data of bellows designed at other laboratories. Narrow-band impedance of the BPM Button has been studied. TE-modes in the BPM button were suppressed by a factor of 8 by modification of existing housings. Two new types of housings are shown. The total impedance of the NSLS-II storage ring is discussed in terms of the loss factor and the vertical kick factor for a 3mm-Gaussian bunch.
BNL, Upton, Long Island, New York
For the NSLS-II storage ring with damping wigglers but without a Landau cavity, the low-current bunch length is 4.5mm. We have studied bunch lengthening and estimated the microwave instability threshold using the multi-particle tracking code TRANFT. An estimate of the pseudo-Green’s function for a 0.5mm driving bunch was obtained for most components of the vacuum system by using the 3D code GdfidL. With our present computer resources, certain components were too large and had too complex geometry to allow the wake for such a short bunch to be computed using GdFidL. In these cases, the actual 3D geometry was approximated by a structure having circular cross-section, and the pseudo-Green’s function was computed using the 2D code ABCI. It was found that the dominant geometric wake is due to the tapers for the in-vacuum undulators. The resistive wall wake is also important. The effect of pseudo-Green’s functions corresponding to an even shorter driving bunch (0.05mm) was investigated using the program ECHO to compute the wake of tapers with circular cross-section. Our results suggest that the microwave threshold will occur at an average single-bunch current greater than 5mA.
CLASSE, Ithaca, New York
Wake fields arising from the discontinuities in the vacuum chamber produce energy spread. In an energy recovery linac (ERL), a spent beam is decelerated before it is dumped in order to use its energy for the acceleration of new beam. While the energy spread accumulated from wakes before deceleration does not increase during deceleration, it becomes more important relative to the beam's decreasing energy. Therefore, in an ERL, wakes can produce very significant energy spread in the beam as it is decelerated to the energy of the beam dump so that beam transport to the dump may become impractical. This effect can place a limit either on the maximum charge per bunch or on the wake field-budget for the ERL. As an example of these wake field effects, this paper discusses their impact for the present design of the Cornell ERL and estimates the effects for typical vacuum chamber components being considered.
EPFL, Lausanne
INFN/LNF, Frascati (Roma)
CERN, Geneva
BNL, Upton, Long Island, New York
UMAN, Manchester
A detailed knowledge of the beam coupling impedance of the CERN Super Proton Synchrotron (SPS) is required in order to operate this machine with a higher intensity for the foreseen Large Hadron Collider (LHC) luminosity upgrade. A large number of Beam Position Monitors (BPM) is currently installed in the SPS, and this is why their contribution to the SPS impedance has to be assessed. This paper focuses on electromagnetic simulations and bench measurements of the longitudinal and transverse impedance generated by the horizontal and vertical BPMs installed in the SPS machine.
Fermilab, Batavia
CERN, Geneva
Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy and CARE-HHH
Motivated by the discussions on scenarios for LHC upgrades, beam studies on the stability of flat bunches in a double-harmonic RF system have been conducted in the CERN Proton Synchrotron (PS). Injecting nearly nominal LHC beam intensity per cycle, 18 bunches are accelerated on harmonic h=21 to 26 GeV with the 10 MHz RF system. On the flat-top, all bunches are then transformed to flat bunches by adiabatically adding RF voltage at h=42 from a 20 MHz cavity in anti-phase to the h=21 system. The voltage ratio V(h42)/V(h21) of about 0.5 was set according to simulations. For the next 140 ms, longitudinal profiles show stable bunches in the double harmonic RF bucket until extraction. Without the second harmonic component, coupled-bunch oscillations are observed. The flatness of the bunches along the batch is analyzed as a measure of the relative phase error between the RF systems due to beam loading. Measurements of electron cloud effects induced by the beam are also discussed. The results of beam dynamics simulations and their comparison with the measured data are presented.
Fermilab, Batavia
In the paper the results are presented for calculation of the transverse wake and RF kick from the power and HOM couplers of the acceleration structure. The beam emittance dilution caused by the couplers is calculated for the main linac and bunch compressor of ILC. It is shown that for the bunch compressor this effect may constitute a problem, and modification of the coupler unit may be necessary in order to preserve the cavity axial symmetry.
LBNL, Berkeley, California
Funding: Supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Uneven beam fill patterns in storage rings, such as gaps in the fill patterns, leads to periodic, or transient loading of the modes of the RF cavities. We show that an analogous effect can occur in the loading of a dipole cavity mode when the beam passes off the electrical center of the cavity mode. Although this effect is small, it results in a variation of the transverse offset of the beam along the bunch train. For ultralow emittance beams, such as optimized third generation light sources and damping rings, this effect results in a larger projected emittance of the beam compared with the single bunch emittance. The effect is particularly strong for the case when a strong dipole mode has been purposely added to the ring, such as a deflecting, or ‘‘crab'' cavity. We derive an approximate analytic solution for the variation of the beam-induced deflecting voltage along the bunch train. We also show via a tracking simulation the combined effect of the periodic loading of the fundamental and dipole modes.
SLAC, Menlo Park, California
Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515.
An L-band (1.3 GHz) sheet beam klystron that will nominally produce 10 MW, 1.6 ms pulses is being developed at SLAC for the ILC program. In recent particle-in-cell transport simulations of the 115 kV DC beam through the klystron buncher section without rf drive, a hose-type instability has been observed that is the result of beam noise excitation of transverse modes trapped between the rf cells. In this paper we describe analytical calculations and numerical simulations that were done to study the nature of this instability and explore the required mode damping and changes in the beam focusing to suppress it.
SLAC, Menlo Park, California
Funding: work supported by the Department of Energy under contract number DE-AC03-76SF00515
We present the history and analysis of different wake field effects throughout the operational life of the PEP-II SLAC B-factory. Although the impedance of the high and low energy rings is small, the high current intense beams generated a lot of power. These wake field effects are: heating and damage of vacuum beam chamber elements like RF seals, vacuum valves , shielded bellows, BPM buttons and ceramic tiles; vacuum spikes, vacuum instabilities and high detector background; beam longitudinal and transverse instabilities. We also discuss the methods used to eliminate these effects. Results of this analysis and the PEP-II experience may be very useful in the design of new storage rings and light sources.
SLAC, Menlo Park, California
A proposed high-brightness synchrotron light source (PEP-X) is under design at SLAC. The 4.5-GeV PEP-X storage ring has four theoretical minimum emittance (TME) cells to achieve the very low emittance and two double-bend achromat (DBA) cells to provide spaces for IDs. Damping wigglers will be installed in zero-dispersion straights to reduce the emittance below 0.1 nm. Ion induced beam instability is one critical issue due to its ultra small emittance. Third harmonic cavity can be used to lengthen the bunch in order to improve the beam life time. Bunch-train filling pattern is proposed to mitigate both the fast ion instability and beam loading effect. This paper investigates the fast ion instability and beam loading for different beam filling patterns.
UCLA, Los Angeles, California
Rome University La Sapienza, Roma
We present the status of development of a 1.5+0.5 cell photoinjector run in the blowout regime. LANL Parmela simulation results indicate a near uniform beam of slice energy spread on the order of 500 eV when neglecting thermal effects. We examine the use of an extra half cell to control longitudinal beam growth and compare the system in development with previous 1.6 cell photoinjector designs.
SLAC, Menlo Park, California
IHEP Beijing, Beijing
Funding: Work supported in part by the DOE Contract DE-AC02-76SF00515. This work was performed in support of the LCLS project at SLAC.
XAL, a high-level application framework originally developed by Spallation Neutron Source (SNS), has been adapted by the Linac Coherent Light Source (LCLS) project. The work includes proper relational database schema modification to better suit XAL configuration data requirement, addition of new device types for LCLS online modeling purpose, longitudinal coordinate system change to better represent the LCLS electron beam rather than proton or ion beam in the original SNS XAL design, intensively benchmark with MAD and present SLC modeling system for the online model, and various new features to the XAL framework. Storing online model data in a relational database and providing universal access methods for other applications is also described here.
SLAC, Menlo Park, California
Funding: Work supported in part by Department of Energy contract DE-AC02-76SF00515.
An x-ray Free-Electron Laser (FEL) calls for a high brightness electron beam. Generically, such a beam needs to be accelerated to high energy on the GeV level and compressed down to tens of microns, if not a few microns. The very bright electron beam required for the FEL has to be stable and the high quality of the electron beam has to be preserved during the acceleration and bunch compression. With a newly developed model independent global optimizer*, here we report study for the control and error diagnostics of such a generic machine: magnetic elements, and RF cavities, and the electron beam parameters: the peak current, centroid energy, and trajectory. Collective effects, such as coherent synchrotron radiation, space charge, and various wakefields are incorporated in a parametric approach. Applicability and verification are detailed for the LINAC Coherent Light Source, an x-ray FEL project being commissioned at SLAC.
*M.J. Lee, SLAC Report in press (2009).
ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
An energy upgrade project of the ATLAS heavy ion linac at ANL includes a new cryomodule containing seven {10}9 MHz β=0.15 quarter-wave superconducting cavities to provide an additional 15 MV voltage to the existing linac. Several new features have been incorporated into both the cavity and cryomodule design. For example, the primary feature of the cryomodule is a separation of the cavity vacuum space from the insulating vacuum. The cavities are designed in order to cancel the beam steering effect due to the RF field. The cryomodule was designed and built as a prototype for the driver linac of the Facility for Rare Isotope Beams (FRIB). Similar design can be effectively used in the SC proton linac for the Project X at FNAL. Currently, we are working on cryomodule assembly and final preparation of cryogenics, RF, vacuum and other subsystems for off-line tests. The initial commissioning results will be reported.
CERN, Geneva
The PIMS will accelerate an H- beam from 100 MeV to 160 MeV, the output energy of Linac4. The cell length is constant within each of the 12 seven-cell cavities, but increases from cavity to cavity according to the increasing beam velocity. Its mechanical design is derived from the five-cell normal conducting LEP cavities, which were in operation at CERN for approximately 15 years. Even though the shunt impedance is around 10% lower than for a Side-Coupled Linac (SCL) operating at 704 MHz, the PIMS has the advantage of using the same RF frequency (352 MHz) as all the other accelerating structures in Linac4, thus simplifying and standardising the linac RF system. Furthermore, the simplified mechanical construction of the PIMS, which uses only 84 cells instead of over 400 for the SCL, also reduces construction costs and tuning effort. In this paper we present the electromagnetic design of the PIMS, including the arguments for the choice of a 5% cell-to-cell coupling factor, the shape of the coupling cells, the dimensioning of the wave-guide ports, and the expected field errors during operation.
CERN, Geneva
KIP, Heidelberg
In this paper is analysed the influence of Higher Order Modes (HOM) on the operation of the superconducting linac section of the SPL, the Superconducting Proton Linac being designed at CERN. For this purpose, the characteristics of the HOMs in the 2 different beta families (0.65, 0.92 both at 704 MHz) of the SPL are calculated to estimate their effect on the cryogenic system and on the beam stability. For both criteria the maximum external Q of the HOMs is defined.
CERN, Geneva
A one meter long hot prototype of the LINAC4 DTL, built in a collaboration with INFN Legnaro, was delivered to CERN in 2008. It was then copper plated at CERN is and is presently prepared for high-power testing at the CERN test stand in SM18. In this paper we present 2D/3D simulations and the first RF low-power measurements to verify the electromagnetic properties of the cavity and to tune it before the high-power RF tests. In particular, the influence of the post couplers was studied in order to guarantee stabilization of the accelerating field during operation. We present an equivalent circuit model of the DTL, together with a comparison of 3D simulations and measurement results for the hot model.
Fermilab, Batavia
NSCL, East Lansing, Michigan
ANL, Argonne
A superconducting cavity has been designed for acceleration of particles traveling at 81% the speed of light (beta = 0.81). The application of interest is an 8 GeV proton linac proposed for a Fermilab upgrade; at present, the cavity is to be used from 420 MeV to 1.3 GeV. The cavity is similar to the 805 MHz high-beta cavity developed for the SNS Linac, but the resonant frequency (1.3 GHz) and beam tube diameter (78 mm) are the same as for the beta = 1 cavities developed for the TESLA Test Facility. Four single-cell prototype cavities have been fabricated and tested. Two multi-cell prototypes have also been fabricated, but they have not yet been tested. The original concept was for an 8-cell cavity, but the final design and prototyping was done for 7 cells. An 11-cell cavity was proposed recently to allow the cryomodules for the beta = 0.81 cavity and downstream 9-cell beta = 1 cavities to be identical. The choice of number of cells per cavity affects the linac design in several ways. The impact of the number of cells in the 8 GeV linac design will be explored in this paper. Beam dynamics simulations from the ANL code TRACK will be presented.
Fermilab, Batavia
Funding: Work performed by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The High Intensity Neutrino Source (HINS) linac R&D program at Fermilab is constructing a first-of-a-kind superconducting H- linac. The machine will demonstrate acceleration of high intensity beam using superconducting spoke cavities, solenoidal focusing optics throughout for control of halo growth, and operation of many cavities from a single high power rf source for acceleration of non-relativistic particles. The ion source and RFQ are operational with beam and the 10 MeV room temperature cavity section is being assembled. Superconducting spoke cavity testing is proceeding. The overall status and outlook of the HINS program is presented.
IAP, Frankfurt am Main
GSI, Darmstadt
For the research program with cooled antiprotons at FAIR a dedicated 70MeV, 70mA proton injector is needed. The main acceleration of this room temperature injector will be provided by six coupled CH-cavities operated at 325MHz. Each cavity will be powered by a 3 MW klystron (6 in total). For the second acceleration unit from 11.7 to 24.3 MeV measurements on a 1:2 scaled model are performed. This tank is now ready for construction and will be used for RF power tests at GSI. The RF power test installations are underway. This paper presents the CH-DTL design and especially the status of the first power cavity.
IAP, Frankfurt am Main
The superconducting CH-cavity is the first multi-cell drift tube cavity for the low and medium energy range of proton and ion linacs. A 19 cell, beta=0.1 cavity has been developed and tested successfully with gradients of up to 7 MV/m. A piezo based fast tuner system has been developped. First horizontal tests of the cavity in a cryo-module with tuner are presented. Additionally, the construction of a new superconducting 325 MHz 7-gap CH-cavity has started. This cavity has an optimized geometry with respect to tuning possibilities, high power RF coupling and minimized end cell lengths. After low power tests it is planned to test this cavity with a 11.4 MeV/u beam delivered by the Unilac at GSI.
INFN- Sez. di Padova, Padova
INFN/LNL, Legnaro (PD)
Consorzio RFX, Associazione Euratom-ENEA sulla Fusione, Padova
The IFMIF-EVEDA RFQ is a 9.8 m long cavity, whose working frequency is equal to 175 MHz. In the base line design the accelerator tank is composed of 9 modules flanged together and a pattern of lateral CF100 flanges allows to host the dummy tuners and the couplers, and a pattern of CF 150 flanges the apertures for vacuum pumping manifolds as well. The construction procedure of each module foresees the horizontal brazing of four half module length electrodes and then the vertical brazing of two brazed assembly. The progresses in the design and engineering phase, as well the description of all the fabrication phases are reported.
LANL, Los Alamos, New Mexico
We are developing high-efficiency room-temperature RF accelerating structures based on inter-digital H-mode (IH) cavities and the transverse beam focusing with permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. Such IH-PMQ accelerating structures following a short RFQ can be used in the front end of ion linacs or in stand-alone applications such as a compact deuteron-beam accelerator up to the energy of several MeV. New results from our detailed electromagnetic 3-D modeling combined with beam dynamics simulations and thermal-stress analysis for a complete IH-PMQ accelerator tank, including the end-cell design, will be presented.
LANL, Los Alamos, New Mexico
Muon accelerators are proposed world wide for future neutrino factory, muon colliders and other applications. One of the problem on accelerating muons is their large emittance as well as huge energy spreads. We carried out some simulation works on large acceptance muon linear accelerator that operates at mixed buncher / acceleration mode. The designed linac has following features: iris structure of 12 cm diameter, inject ~100 MeV muon beam and accelerates to several 100 MeV, 700 MHz and 25 MV/m peak field. Further acceleration of the muon beam can be easily done by extending the muon linear accelerator. According to the simulation, our linac can accelerates DC muon beam of 20 - 100 MeV range with 20 % phase acceptance.
LANL, Los Alamos, New Mexico
Funding: This work is supported by the U. S. Department of Energy, Contract DE-AC52-06NA25396.
The Los Alamos Neutron Science Center simultaneously provides both H- and H+ beams to several user facilities. Opposite polarity beams are usually accelerated in the linac during the same macropulse when beam-loading limitations are not exceeded. Presently, the Weapons Neutron Research (WNR) H- and Isotope Production Facility (IPF) H+ beams are accelerated simultaneously during the same macropulse. The amplitude of the cavity field in the last 201-MHz buncher, located in the common transport just upstream of the DTL, is a compromise between the optimal values for each beam. Recent beam dynamics studies have shown that implementing a debuncher cavity in the H- low-energy beam transport would allow for more optimal operation of both beams. For this application where space is limited, a compact 201-MHz quarter-wave cavity will be used. This paper will report on the beam dynamics simulations performed and the quarter-wave cavity design being developed to address this issue.
Naples University Federico II and INFN, Napoli
Istituto Nazionale di Fisica Nucleare, Milano
Naples University Federico II, Napoli
The use of BBAC (Back-to-Back Accelerating Cavity) tiles in proton Side Coupled Linacs can be extended down to energies of the order of 20 MeV, keeping more than suitable shunt impedances and energy gradients. However, the considerable energy absorption from the cavity noses may induce a remarkable increase in their temperature. This may cause both a strong duty-cycle-dependent detuning of the modules, and dangerous thermo-mechanical stress due to the non-uniform temperature distribution. An innovative shape of the BBAC tile is proposed, which allows to limit the temperature rise within a safe range, without introducing detrimental effects neither on the shunt impedance nor on the working frequency. A protocol for the design of such a cavity will be presented.
PKU/IHIP, Beijing
Funding: supported by NSFC (19775009)
A trapezoidal IH-RFQ (T-IH-RFQ) is being built to accelerate 14C^+ from 40 keV to 500 keV, motivated by RFQ based 14C AMS application at Peking University. The last design of beam dynamics and the optimized results of RF structure will be presented in this paper. The length of the cavity is about 1.1m operating at {10}4MHz, with a designed transmission efficiency of more than 97%. A special feature is that the RFQ output beam energy spread is as low as 0.6% approached by the method of internal discrete bunching. On the other hand, the new RF cavity structure T-IH-RFQ was proposed for the beam dynamics design, which has higher resonant frequency than traditional four rods RFQ and IH-RFQ at the same transverse dimension. Microwave Studio (MWS) simulations have been performed to study the field distribution and power consumption characteristic of this T-IH-RFQ. The specific shunt impedance and the quality factor have been optimized. Those details will be given.
RLNR, Tokyo
An Interdigital-H (IH) linac has been used for ion acceleration in low beta range. It can realize a resonant cavity of a convenient size at low frequencies and higher shunt impedance at low energy range. These characteristics are advantageous especially for heavy ion acceleration. Since the shunt impedance of the IH linac reduces according to the increasing of beam energy, the linacs operated by the TM010 mode such as an Alvarez type and a coupling cavity type are adopted for medium and high energy range. However, we propose the new IH linac using the TE11n mode, the higher order mode IH (HOM-IH) linac. By using the higher order mode, the resonance frequency is higher than that of the IH linac. This property is suitable for middle and high beta linacs, and a proton linac as well. The design of the cavity structure and the possibility are presented.
SAMEER, Mumbai
The developmental work on linear electron accelerators in SAMEER, India is briefed in this paper. The technology to develop ‘S’ band compact side coupled standing wave electron linear accelerator is very well established at SAMEER, Mumbai center. 6 MV to 15 MV linacs are developed with the desired specifications. Indigenous 6 MV linac machines for radiotherapy applications have been developed successfully and these machines are in use at premier cancer hospitals in the country. SAMEER is presently working on the development of the dual mode-electron and photon and dual photon energy linear accelerator for radiotherapy application. The 6 MeV linac tube development and its test results are discussed.
USP/LAL, Sao Paulo
Funding: FAPESP, CNPq
The Instituto de Física da Universidade de São Paulo (IFUSP) is building a two-stage 38 MeV continuous wave racetrack microtron. This accelerator consists of a linac injector that delivers a 1.7 MeV beam to a microtron (booster) with 5 MeV exit energy. A transport line guides the beam to the main microtron to be accelerated to energies up to 38 MeV in steps of 0.9 MeV. This work describes the commissioning of the linac injector that comprises the first two accelerating structures of the IFUSP Microtron. A provisional beam line was built at the end of the linac to provide energy and current measurements. We also present results concerning RF power, RF phase, and temperature control of the accelerating structures. The first results of the chopper and buncher systems are also presented.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Features of a linac and ring for potential ISIS upgrades are outlined. Maximum parameters are 0.8 GeV, 0.5 MW for the H(-)linac and 3.2 GeV, 2 MW for the ring, both at 30 or 50 Hz. The linac is based on a 324 MHz frequency at low energies, having an ion source, LEBT, 3 MeV RFQ and MEBT, with A 74.8 MeV drift tube linac (DTL) and intermediate energy beam transport (IEBT). The MEBT chopper stage uses solenoid and triplet focusing, and both MEBT and IEBT have long sections for beam collimation. There are three options for the higher energies, a 648 MHz superconducting linac(ScL1, ScL2 and ScL3), a 648 MHz (CCL, ScL2 and ScL3), and a 324 MHz (ScLa) with a two-stage 972 MHz (ScLb and ScLc). The ScL1, CCL and ScLa are designed to accelerate the H(-) beam from 74.8 to ~200 MeV. The proton synchrotron design is based on a five superperiod lattice of doublet and triplet cells, and has a circumference of ~ 370 m.
Soreq NRC, Yavne
ACCEL, Bergisch Gladbach
The Soreq Applied Research Accelerator Facility, SARAF, is currently under construction at Soreq NRC. SARAF is based on a continuous wave (CW), proton/deuteron RF superconducting linear accelerator with variable energy (540 MeV) and current (0.04-2 mA). SARAF is designed to enable hands-on maintenance, which implies beam loss below 10-5 for the entire accelerator. Phase I of SARAF consists of a 20 keV/u ECR ion source, a low energy beam transport section, a 4-rod RFQ, a medium energy (1.5 MeV/u) transport section, a superconducting module housing 6 half-wave resonators and 3 superconducting solenoids, a diagnostic plate and a beam dump. Phase II will include 5 additional superconducting modules. The ECR source is in routine operation since 2006, the RFQ is in routine operation with protons since 2008 and has been further operated with molecular hydrogen and deuterons. The superconducting module is being operated and characterized with protons. Phase I commissioning results, their comparison to beam dynamics simulations and Phase II plans will be presented.
THALES, Colombes
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
EuroMev, Buc
A turn key 100 MeV linac was provided by THALES Communications in order to inject electrons into the booster synchrotron of ALBA*. The linac was commissioned in October 2008. This paper will remind the main features of the linac** and will give results obtained during the commissioning tests. The energy and emittance measurements have been done on the transfer line concieved and realized by CELLS. Specified and measured beam parameters will be compared to show the performance of the entire system.
* D. Einfeld "Progress of ALBA", EPAC08, Genoa, Italy, June 2008.
** A. Falone et Alt, "Status of the 100 MeV preinjector for the ALBA synchrotron", EPAC08, Genoa, Italy, June 2008.
TUB, Beijing
Funding: Work supported by National Science Foundation of China (No. 10775079)
On the basis of an X-band 2MeV on-axis standing wave electron linear accelerator, a compact 4MeV/2.5MeV X-band accelerator is being developed at Tsinghua University for non-destructive testing. The single tube can deliver two kinds of x-rays, with dose rate of >100cGy/min@m at 4MeV or >50cGy/min@m at 2.5MeV. To suppress the nearby modes, the coupler is set in the middle of the long coupled cavity chain. The coupled circuit model is applied to analyze the RF characteristic and the dynamic is investigated by CAV code. The prototype has being machined and tuned at our laboratory.
jfhua@mail.tsinghua.edu.cn
TUB, Beijing
The Multipactor Electron Gun (MEG) can produce high current self-bunching electron beams. In this paper, the primary experimental results of an S-band MEG based accelerator are presented. The accelerator was modified from a 6MeV standing wave accelerator to integrate the MEG, which has an adjusting structure to control both the cathode-grid distance and frequency tuner. The designed output energy is 5MeV and average current is 100mA. The experiment included low power microwave parameter measurement and high power beam test. In the microwave parameter measurement, the relationship between tuner position and E-field distribution was investigated. Platinum was used as the secondary electron emitters of the MEG. The multipacting process was observed and an average current of 40mA was collected by an aluminum target.
ENEA C.R. Frascati, Frascati (Roma)
SPARKLE S.r.l., Casarano (Lecce)
SPARKLE company is setting up in the south of Italy (Casarano) a new cyclotron facility based on a 18 MeV, 150 uA IBA Cyclone 18/9. The aim is to create a multidisciplinary research site for the medical applications of accelerators. The main activity will be the production of standard and new radionuclides, by internal targets and one external beam line. Another opposite beam line has been reserved for low current proton irradiations for radiotherapy studies, and a linac booster between 18 and 24 MeV was designed and built to this end. The beam line, which focuses and matches the beam to the linac, includes a chopping system to synchronize the beam to the pulsed linac and to collect 99% of the beam not synchronous to the linac. The linac uses a 3 GHz SCDTL structure powered by a magnetron modulator system. In the paper we report an overview of the beam line, component design, and tests.
DAE/VECC, Calcutta
UGC DAE CSR, Kolkata
An ISOL post-accelerator type of Rare Ion Beam (RIB) facility is being developed at our centre. The facility will use light ion beams from the K=130 cyclotron for producing RIBs using suitable thick targets. Also, development of an electron LINAC has been initiated with an eye to produce RIBs using the photo-fission route. The RIBs will be ionized, mass separated and the RIB of interest will be accelerated using a four rod Radio Frequency Quadrupole from 1.7 to 98 keV/u. The posts, vanes and base plate of the RFQ have been machined from OFC copper and the cavity is made from steel with its inner surface plated with copper. Oxygen beam of charge state 5+ has already been accelerated with an efficiency of around 90% through the RFQ. The first IH LINAC will accelerate RIBs up to about 186 keV/u. The octagonal shape LINAC cavity is made from explosively bonded copper cladded steel. Low power tests of the LINAC is encouraging - the beam test is scheduled for January 2009 and the results of which will be reported. The R&D efforts in various areas of this project will be discussed in this paper. Special emphasis will be given to the development of the RFQ and LINAC.
PKU/IHIP, Beijing
Funding: work supported by NSFC(10805003,10855001)
The beam commissioning of Separated Function RFQ (SFRFQ) accelerator, which can gain high accelerating efficiency and enough focusing strength for low energy high current beam, is presented. In order to demonstrate the feasibilities of this novel accelerator, a prototype cavity was designed and constructed. The O+ beam was accelerated from 1MeV to 1.6MeV by SFRFQ cavity. A triplet was constructed for the transverse beam matching between the 1MeV ISR-RFQ 1000 and SFRFQ. A capacitance frequency tuning system and RF phase shifter were used to keep SFRFQ cavity working at the same frequency of ISR RFQ at the right phase. The whole RFQ accelerator system and the preliminary beam test results are presented in this paper.