IPAC2012 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOYBP01	State-of-the-Art and Future Prospects in RF Superconductivity	SRF, niobium, electron, storage-ring	11
	K. Saito KEK, Ibaraki, Japan
	This presentation should recount the remarkable progress in improving the performance of superconducting cavities over the past 50 years and explore future directions, including advances in materials other than Nb, such as MgB2 and novel multi-layer superconductor-insulator systems. This talk should provide an overview of international activities.
	Slides MOYBP01 [10.097 MB]

MOOBB01	Transverse-to-longitudinal Emittance-exchange with an Energy Chirped Beam	emittance, electron, simulation, radiation	49
	J.C.T. Thangaraj, H.T. Edwards, A.S. Johnson, A.H. Lumpkin, T.J. Maxwell, J. Ruan, J.K. Santucci, Y.-E. Sun, R.M. Thurman-Keup Fermilab, Batavia, USA
	Emittance exchange has been proposed to increase the performance of free electron lasers by tailoring the phase space of an electron beam. The principle of emittance exchange - where the transverse phase space of the electron beam is exchanged with the longitudinal phase space - has been demonstrated recently at the A0 photoinjector. The experiment used a low charge bunch (250 pC) with no energy chirp. Theory predicts an improvement in the emittance exchange scheme when the incoming beam has an energy chirp imparted on it. The energy chirp helps to overcome the thick lens effect of the deflecting mode cavity and other second order effects that might lead to an incomplete emittance exchange at higher charges. In this work, we report experimental and simulation results from operating the emittance exchange beam line using an energy chirped beam with higher charge (500 pC) at different RF-chirp settings.
	Slides MOOBB01 [2.338 MB]

MOOAC01	The European XFEL LLRF System	LLRF, cryomodule, klystron, laser	55
	J. Branlard, G. Ayvazyan, V. Ayvazyan, M.K. Grecki, M. Hoffmann, T. Jeżyński, I.M. Kudla, T. Lamb, F. Ludwig, U. Mavrič, S. Pfeiffer, H. Schlarb, Ch. Schmidt, H.C. Weddig, B.Y. Yang DESY, Hamburg, Germany P. Barmuta, S. Bou Habib, L. Butkowski, K. Czuba, M. Grzegrzółka, E. Janas, J. Piekarski, I. Rutkowski, D. Sikora, L. Zembala, M. Żukociński Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland W. Cichalewski, K. Gnidzińska, W. Jałmużna, D.R. Makowski, A. Mielczarek, A. Napieralski, P. Perek, A. Piotrowski, T. Pożniak, K.P. Przygoda TUL-DMCS, Łódź, Poland S. Korolczuk, J. Szewiński The Andrzej Soltan Institute for Nuclear Studies, Centre Świerk, Świerk/Otwock, Poland K. Oliwa, W. Wierba IFJ-PAN, Kraków, Poland
	The European X-ray free electron laser accelerator consists of 800 superconducting cavities grouped in 25 RF stations. The challenges associated with the size and complexity of this accelerator required a high-precision, modular and scalable low level RF (LLRF) system. TheμTCA technology (uTCA) was chosen to support this system and adapted for RF standards. State-of-the-art hardware development in close collaboration with the industry allowed for the system continuity and maintainability. The complete LLRF system design is now in its final phase and the designed hardware was installed and commissioned at FLASH. The uTCA hardware system, measurement results and system performance validation will be shown. Operational strategy and plans for future automation algorithms for performance optimization will also be presented in this paper.
	Slides MOOAC01 [12.188 MB]

MOOAC03	Superconducting Resonators Development for the FRIB and ReA Linacs at MSU: Recent Achievements and Future Goals	linac, cryomodule, SRF, ion	61
	A. Facco INFN/LNL, Legnaro (PD), Italy E.C. Bernard, J. Binkowski, C. Compton, J.L. Crisp, L.J. Dubbs, K. Elliott, A. Facco, L.L. Harle, M. Hodek, M.J. Johnson, D. Leitner, M. Leitner, I.M. Malloch, S.J. Miller, R. Oweiss, J. Popielarski, L. Popielarski, K. Saito, J. Wei, J. Wlodarczak, Y. Xu, Y. Zhang, Z. Zheng FRIB, East Lansing, Michigan, USA A. Burrill, G.K. Davis, K. Macha, A.V. Reilly JLAB, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 The superconducting driver and post-accelerator linacs of the FRIB project, the large scale radioactive beam facility under construction at MSU, require the construction of about 400 low-beta Quarter-wave (QWR) and Half-wave resonators (HWR) with four different optimum velocities. 1st and 2nd generation prototypes of β=0.041 and 0.085 QWRs and β=0.53 HWRs have been built and tested, and have more than fulfilled the FRIB and ReA design goals. The present cavity surface preparation at MSU allowed production of low-beta cavities nearly free from field emission. The first two cryostats of β=0.041 QWRs are now in operation in the ReA3 linac. A 3rd generation design of the FRIB resonators allowed to further improve the cavity parameters, reducing the peak magnetic field in operation and increasing the possible operation gradient , with consequent reduction of the number of required resonators. The construction of the cavities for FRIB, which includes three phases for each cavity type (development, pre-production and production runs) has started. Cavity design, construction, treatment and performance will be described and discussed. Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics.
	Slides MOOAC03 [4.009 MB]

MOOBC01	Electron Linac Photo-fission Driver for the Rare Isotope Program at TRIUMF	cryomodule, gun, TRIUMF, linac	64
	S.R. Koscielniak, F. Ames, R.A. Baartman, I.V. Bylinskii, Y.-C. Chao, D. Dale, R.J. Dawson, A. Koveshnikov, A. Laxdal, R.E. Laxdal, F. Mammarella, L. Merminga, A.K. Mitra, Y.-N. Rao, V.A. Verzilov, D. Yosifov, V. Zvyagintsev TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada D. Karlen Victoria University, Victoria, B.C., Canada
	The TRIUMF Advanced Rare Isotope Laboratory (ARIEL) is funded since 2010 June by federal and BC Provincial governments. In collaboration with the University of Victoria, TRIUMF is proceeding with construction of a new target building, connecting tunnel, rehabilitation of an existing vault to contain the electron linear accelerator, and a cryogenic compressor building. TRIUMF starts construction of a 300 keV thermionic gun, and 10 MeV Injector cryomodule (EINJ) in 2012; the designs being complete. The 25 MeV Accelerator Cryomodule will follow in 2013. TRIUMF is embarking on major equipment purchases and has signed contracts for 4K cryogenic plant and a 290kW CW klystron, and four 1.3 GHz Nb 9-cell cavities from a local Canadian supplier. Moreover, the low energy beam transport is under construction; and detailing of two intra-cryomodule beam transports has just begun. Procurements are anticipated in mid 2012 for (i) the entire facility quadrupole magnets, and (ii) the klystron's 600kW HV power supply.
	Slides MOOBC01 [4.852 MB]

MOOBC02	Status of Main Linac Cryomodule Development for Compact ERL Project	linac, HOM, cryomodule, damping	67
	K. Umemori, K. Enami, T. Furuya, H. Sakai, M. Satoh, K. Shinoe KEK, Ibaraki, Japan E. Cenni Sokendai, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	The Compact ERL, which is a test facility of ERL, is under construction at KEK, in Japan. For the main linac, one cryomodule, containing two 9-cell superconducting cavities, is under development. The cryomodule has been designed under High Pressure Gas Safety Code in Japan. Thermal design and cavity alignment have been also carefully considered. Two 9-cell cavities were already fabricated and their performances were confirmed by vertical tests. They satisfied ERL main linac specifications. Their accelerating field reached to 25 MV/m, without field limits. Two input couplers, three HOM absorbers and two Slide-Jack tuners are also under fabrication for the cryomodule. High power processing will be applied for input couplers, at a test stand using a 300 kW klystron. Cooling tolerance and HOM damping abilities were tested for HOM absorbers. Some performance studies were also applied for the tuner at room temperature condition. Cryomodule assembly is planned on this summer. After cooling tests and high power tests will be carried out, ERL beam operation will be started.
	Slides MOOBC02 [3.849 MB]

MOPPC003	Very Fast LHC Crab Cavity Failures and their Mitigation	luminosity, simulation, betatron, optics	121
	T. Baer, R. Calaga, R. De Maria, S.D. Fartoukh, E. Jensen, R. Tomás, J. Tückmantel, J. Wenninger, B. Yee-Rendon, F. Zimmermann CERN, Geneva, Switzerland T. Baer University of Hamburg, Hamburg, Germany
	For the high-luminosity LHC upgrade program (HL-LHC), the installation of crab cavities (CCs) is needed to compensate the geometric luminosity loss due to the crossing angle and for luminosity leveling []. The baseline is a local scheme with CCs around the ATLAS and CMS experiments. In a failure case (e.g. a control failure or arcing in the coupler), the voltage and/or phase of a CC can change significantly with a very fast time constant of the order of 1 to 10 LHC turns. This can lead to large, global betatron oscillations of the beam. The impact of CC failures on the beam dynamics is discussed and the results from dedicated simulations are presented. Mitigation strategies to limit the impact of CC failures to an acceptable level are proposed. F. Zimmermann and O. Brüning, “Parameter Space for the LHC High-Luminosity Upgrade”, IPAC'12, MOPPC005, May 2012.

MOPPC015	Proposal for an RF Roadmap Towards Ultimate Intensity in the LHC	klystron, feedback, injection, beam-loading	154
	P. Baudrenghien, T. Mastoridis CERN, Geneva, Switzerland
	The LHC is currently operated with 1380 bunches at 50 ns spacing and 1.4 E11 p per bunch (0.35A DC). In this paper the RF operation with ultimate bunch intensity (1.7 E11 p per bunch) and 25 ns spacing (2808 bunches per beam) summing up to 0.86A DC is presented. With the higher beam current, the demanded klystron power will be increased and the longitudinal stability margin reduced. In addition one must consider the impact of a klystron trip (voltage and power transients in the three turns latency before the beam is actually dumped). In this work a scheme is proposed that can deal with ultimate bunch intensity, without modification to the RF power system. Only a minor upgrade of the LLRF will be necessary: the field set point will be modulated according to the phase shift produced by the transient beam loading, thus minimizing the requested RF power while keeping the strong feedback for stability and reduction of RF noise.

MOPPC036	Influence of Intense Beam in High Pressure Hydrogen Gas Filled RF Cavities	electron, plasma, proton, pick-up	208
	K. Yonehara, M.R. Jana, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup Fermilab, Batavia, USA M. Chung Handong Global University, Pohang, Republic of Korea M.G. Collura Politecnico di Torino, Torino, Italy G. Flanagan, R.P. Johnson, M. Notani Muons, Inc, Batavia, USA B.T. Freemire, Y. Torun IIT, Chicago, Illinois, USA
	Funding: This work is supported by US DOE under contract DE-AC02-07CH11359. Breakdown plasma in a high-pressure hydrogen gas filled RF cavity has been studied from a time domain spectroscopic light analysis. The observed breakdown plasma temperature and density reached 21,000 K and 10²⁰ cm^-3, respectively. The electron recombination rate has been evaluated from the decay of plasma density in various gas pressures. The recombination mechanism in dense plasma will be discussed. Finally, the similarity and difference of the breakdown processes between the high-pressure hydrogen gas filled RF cavity and a vacuum RF one will be discussed.

MOPPC039	Electron Recombination in a Dense Hydrogen Plasma	electron, collider, plasma, ion	217
	B.T. Freemire, P.M. Hanlet IIT, Chicago, Illinois, USA M. Chung Handong Global University, Pohang, Republic of Korea M.G. Collura Politecnico di Torino, Torino, Italy M.R. Jana, C. Johnstone, T. Kobilarcik, G.M. Koizumi, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup, Y. Torun, K. Yonehara Fermilab, Batavia, USA R.P. Johnson Muons, Inc, Batavia, USA
	Funding: US DOE under contract DE-AC02-07CH11359. A high pressure hydrogen gas filled RF cavity was subjected to an intense proton beam to study the evolution of the beam induced plasma inside the cavity. The electron recombination rate with the dense ionized hydrogen plasma has been measured under varying conditions. Recombination rates as high as 10^-7 cm³/s have been recorded. This technique shows promise in the R&D program for a muon accelerator. The use of hydrogen, both as a way to prevent breakdown in an RF cavity and as a mechanism for cooling a beam of muons, will be discussed.

MOPPC040	Study of Electronegative Gas Effect in Beam-Induced Plasma	plasma, electron, proton, ion	220
	M.A. Leonova, M.R. Jana, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, USA M. Chung Handong Global University, Pohang, Republic of Korea M.G. Collura Politecnico di Torino, Torino, Italy B.T. Freemire, P.M. Hanlet, Y. Torun IIT, Chicago, Illinois, USA R.P. Johnson Muons, Inc, Batavia, USA
	Funding: This research was supported by US DOE under contract DE-AC02-07CH11359. Muon Colliders and Neutrino Factories call for R&D for a high-gradient RF system capable of operating in a high magnetic field. Adding a high pressure gas inside an RF cavity (HPRF) prevents cavity breakdown, allowing higher gradients in a magnetic field. A high-energy beam passing through an HPRF cavity ionizes the gas, producing plasma. Plasma electrons absorb cavity’s energy, reducing the energy available for beam acceleration. Doping cavity gas with electronegative gas (gas that tends to attract and bond electrons) reduces the number of plasma electrons. The experiments were carried out at the MuCool Test Area (MTA) facility at Fermilab. Different concentrations of an electronegative gas SF6 were added to hydrogen gas. The results of room-temperature tests showing a great reduction in power drop in the cavity will be presented. However, a realistic cavity would operate at liquid nitrogen temperature, where SF6 freezes. Thus, a search for a better electronegative gas candidate is underway; we plan to test oxygen-doping next.

MOPPC058	Eigenmode Computation for Ferrite-loaded Cavity Resonators	resonance, heavy-ion, acceleration, ion	265
	K. Klopfer, W. Ackermann, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	The GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt is operating the heavy-ion synchrotron SIS18 for fundamental research. Within the ring two ferrite-loaded cavity resonators are installed. During the acceleration phase their resonance frequency has to be adjusted to the revolution frequency of the heavy-ions to reflect their increasing velocity. Within the resonator structures dedicated biased ferrite rings are installed. In the whole setup a properly chosen bias current is used to modify the differential permeability of the ferrite material which consequently enables to adjust the eigenfrequency of the resonator system. The goal of the current study is to numerically determine the lowest eigensolutions of accelerating ferrite-loaded cavities based on the Finite Integration Technique. Since the underlying eigenmodes depend on the differential permeability, the static magnetic field generated by the bias current has to be computed in a first step. The eigenmodes can then be determined with the help of a dedicated Jacobi-Davidson eigensolver. Particular emphasis is put on the implementation to enable high performance computations based on distributed memory machines.

MOPPC059	Various Approaches to Electromagnetic Field Simulations for RF Cavities	simulation, impedance, electromagnetic-fields, HOM	268
	C. Liu, W. Ackermann, W.F.O. Müller, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by BMBF under contract 05H09RD5. The Superconducting Proton Linac (SPL) cavity is mainly designed and conducted by CERN. It is a part of the planned injector upgrade of the Large Hadron Collider (LHC). The SPL cavity is used to accelerate the ion beam from 160 MeV to 5GeV and served as a driver for neutrino facilities and radioactive beam facilities. In the Superconducting Proton Linac (SPL) cavity, it is very important to calculate the eigenmodes precisely, because many higher-order modes (HOMs) can lead to particle beam instabilities. We used and compared three different ways to calculate the eigenmodes in the SPL cavity: field simulation with hexahedron mesh in frequency domain, field simulation with hexahedron mesh in time domain, and field simulation with tetrahedral mesh and higher order curvilinear elements. In this paper the principles of the three numerical methods will be introduced and compared. Finally the calculated results will be presented.

MOPPC062	Eigenmode Computation for Cavities with Perturbed Geometry Based on a Series Expansion of Unperturbed Eigenmodes	HOM, factory, wakefield, higher-order-mode	277
	K. Brackebusch, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
	Funding: Work supported by Federal Ministry for Research and Education BMBF under contracts 05H09HR5 and 05K10HRC. The geometry of an accelerator cavity determines its eigenmodes and thereby its performance characteristics. Therefore, accelerating performance and wakefield characteristics may be improved by an intentional modification of the geometry. However, undesired geometry perturbations due to manufacturing tolerances and operational demands can likewise impair it. To analyze the effects of geometry variations on the eigenmodes, parameter studies are to be undertaken. Using common eigenmode solvers it usually is necessary to perform a full eigenmode computation for each variation step, even if the geometry is only slightly altered. Parameter studies for cavity perturbations thus tend to be computationally extensive and inefficient. In this paper, we present the fundamentals of an efficient eigenmode computation method for varying cavity geometries. Knowing a set of initial eigenmodes of an unperturbed geometry, the method allows expanding the eigenmodes of any geometry that is part of the unperturbed one as a series of the initial eigenmodes. Thereby the computation effort may be significantly reduced. The method is demonstrated by means of analytically evaluable cavity geometries.

MOPPC070	Field Emission Simulation for KEK-ERL 9-Cell Superconducting Cavity	electron, simulation, linac, coupling	295
	E. Cenni Sokendai, Ibaraki, Japan T. Furuya, H. Sakai, M. Satoh, K. Shinoe, K. Umemori KEK, Ibaraki, Japan M. Sawamura JAEA/ERL, Ibaraki, Japan
	In order to develop the Energy Recovery Linac at KEK, we are studying the performance of L-band superconducting cavities by means of vertical tests. One of the limiting factor for the cavities performance is power losses due to field emitted electrons. With regard to this phenomena, a particle tracking code is used to study electron trajectories and deposited energy on the inner surface of the cavity. Different emitters location were tested within a range of accelerating field and phases in order to reproduce different scenario. The final goal of this study is to locate the sources of the electrons inside the cavity through a deeper understanding of the phenomena. To validate the results from the simulation the outcome data are compared with other particle tracking codes.

MOPPC081	Simulation of RF Cavity Dark Current in Presence of Helical Magnetic Field	electron, simulation, dipole, site	325
	G.V. Romanov, V.S. Kashikhin Fermilab, Batavia, USA
	In order to produce muon beam of high enough quality to be used for a Muon Collider, its large phase space must be cooled several orders of magnitude. This task can be accomplished by ionization cooling. Ionization cooling consists of passing a high-emittance muon beam alternately through regions of low-Z material, such as liquid hydrogen, and very high accelerating RF cavities within a multi-Tesla solenoidal focusing channel. But first high power tests of an RF cavity with beryllium windows in a solenoidal magnetic field showed a dramatic drop in accelerating gradient due to RF breakdowns. It has been concluded that external magnetic fields parallel to the RF electric field significantly modifies the performance of RF cavities. However, the magnetic field in a Helical Cooling Channel has a strong dipole component in addition to a solenoidal one. The dipole component essentially changes electron motion in a cavity compared to a pure solenoidal case, making dark current less focused at field emission sites. The simulation of a dark current dynamic in HCC performed with CST Studio Suite is presented in this paper.

MOPPC095	XAL's Online Model at ReA3 to Understand Beam Performance	linac, simulation, cryomodule, lattice	358
	C. Benatti NSCL, East Lansing, Michigan, USA P. Chu, M.J. Syphers, X. Wu FRIB, East Lansing, Michigan, USA
	Funding: This material is based on work supported by the National Science Foundation under Grant No. PHY-1102511 and by Michigan State University. The ReA3 facility at the NSCL at MSU has been designed to reaccelerate rare isotope beams to 3MeV/u. ReA3 consists of a charge to mass selection section, a normal conducting RFQ, a superconducting linac, and transport beam lines that deliver the beam to the experiments. The beam optics designs were developed using COSY and IMPACT. A code with an online model capable of interacting with the control system, such as XAL, developed at SNS, would be ideal for studying this system. New elements have been added to XAL’s already extensive list of supported devices in order to model elements unique to the NSCL. The benchmarking process has been completed for establishing the use of XAL’s Online Model at the NSCL, and preliminary results from its use at the ReA3 control room have been obtained. The development of applications to fit the needs of the program is ongoing. A summary of the benchmarking process is presented including both transverse and longitudinal studies. J. Galambos et al., Proc. PAC 2005, p. 79, (2005); doi: 10.1109/PAC.2005.1590365.

MOPPC096	Multiphysics Applications of ACE3P	simulation, HOM, vacuum, SRF	361
	K.H. Lee, C. Ko, Z. Li, C.-K. Ng, L. Xiao SLAC, Menlo Park, California, USA G. Cheng, H. Wang JLAB, Newport News, Virginia, USA
	Funding: Work supported by US DOE Offices of HEP, ASCR and BES under contract AC02-76SF00515. The TEM3P module of ACE3P, a parallel finite-element electromagnetic code suite from SLAC, focuses on the multiphysics simulation capabilities, including thermal and mechanical analysis for accelerator applications. In this pa- per, thermal analysis of coupler feedthroughs to supercon- ducting rf (SRF) cavities will be presented. For the realistic simulation, internal boundary condition is implemented to capture RF heating effects on the surface shared by a di- electric and a conductor. The multiphysics simulation with TEM3P matched the measurement within 0.4%.

MOPPD033	Strong-focusing Cyclotron - High-current Applications	cyclotron, dipole, proton, focusing	436
	P.M. McIntyre, S. Assadi, K.E. Badgley, C. Collins, J. Comeaux, R. Garrison, J.N. Kellams, T.L. Mann, A.D. McInturff, N. Pogue, A. Sattarov Texas A&M University, College Station, Texas, USA
	Funding: This work is supported by grants from the State of Texas (ASE) and from the Mitchell Family Foundation. Quadrupole focusing channels are integrated into the pole faces of a superconducting sector cyclotron, to enable control of the betatron tunes for all orbits. This provision makes it possible to lock the tunes to desired values for all orbits, thereby eliminating resonance crossing and facilitating local orbit bumps for injection and extraction. Optical control is of particular importance for applications where higher beam current is desired, for ADS fission drivers, for spallation neutron sources, and for medical isotope production.

MOPPD034	Flux-coupled Stacking of Cyclotrons for a High-power ADS Fission Driver	cyclotron, injection, focusing, target	439
	A. Sattarov, S. Assadi, K.E. Badgley, J.N. Kellams, T.L. Mann, A.D. McInturff, P.M. McIntyre, N. Pogue Texas A&M University, College Station, Texas, USA
	Funding: This work is funded by grants from the State of Texas (ASE) and the Mitchell Family Foundation. The sector magnets for an isochronous cyclotron are configured as a flux-coupled stack of apertures, each forming an independent cyclotron, separated sufficiently to accommodate independent superconducting rf cavities. The stack strategy makes it possible to deliver any amount of proton beam power consistent with the limitations of each individual cyclotron, and to deliver the aggregate power to a number of spallation targets as dictated by optimum coupling for accelerator-driven subcritical (ADS) fission and by limitations in target transfer.

MOPPP015	Status of the BERLinPro Energy Recovery Linac Project	linac, SRF, booster, quadrupole	601
	J. Knobloch, M. Abo-Bakr, W. Anders, R. Barday, K.B. Bürkmann-Gehrlein, V. Dürr, S.C. Heßler, A. Jankowiak, T. Kamps, O. Kugeler, B.C. Kuske, P. Kuske, A.N. Matveenko, G. Meyer, R. Müller, A. Neumann, K. Ott, Y. Petenev, D. Pflückhahn, T. Quast, J. Rahn, S.G. Schubert HZB, Berlin, Germany
	Funding: Funding provided by the BMBF and the State of Berlin In October 2010 Helmholtz Zentrum Berlin received funding to design and build the Berlin Energy Recovery Linac Project BERLinPro. The goal of this compact ERL is to develop the accelerator physics and technology required to generate and accelerate a 100-mA, 1 mm·mrad emittance beam. Given the flexibility of ERLs, other operation modes such as short-bunch operation will also be investigated. The BERLinPro technology and know-how can then be transferred to a variety of ERL-based applications. Presently, BERLinPro is in the design phase and the optics has been settled. Furthermore, first beam has been achieved with a superconducting RF photoinjector, which represents an important step towards realizing a CW injector for BERLinPro. An overview of the present status and the conceptual design report is presented.

MOPPP023	Effect of DC Photoinjector Gun Voltage on Beam Dynamics in ALICE ERL	gun, electron, booster, linac	616
	Y.M. Saveliev, F. Jackson, J.K. Jones, J.W. McKenzie STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The ALICE ERL employs a DC HV photoelectron gun as an electron source. As with other machines in this class, the electron beam is not always of perfect quality. This is aggravated by that the ALICE gun has been operated so far at lower 230kV voltage compared to the design value of 350kV due to hardware limitations. The “two beams” structure was observed and experimentally investigated and found to be the result of complex processes during initial stages of beam acceleration. The experimental observations and data will be compared with those obtained at a nominal 350kV gun voltage. An investigation of the effect of the DC photogun voltage on longitudinal and transverse beam dynamics will be presented and discussed.

MOPPP026	Cryogenic Distribution System for the Proposed Cornell ERL Main Linac	cryomodule, linac, HOM, vacuum	619
	E.N. Smith Cornell University, Ithaca, New York, USA Y. He, G.H. Hoffstaetter, M. Liepe, M. Tigner CLASSE, Ithaca, New York, USA
	Funding: This material is based upon work supported by the National Science Foundation under Grant No. DMR-0807731. The proposed Cornell ERL main linac requires a total cooling power of nearly 8kW at 1.8K, 5kW at 5K and over 100kW at 80K. This is distributed over approximately 65 cryomodules, each containing 6 rf cavities and associated input couplers and higher order mode absorbers. situated in two underground tunnels. While the total heat load is comparable to that for each of the 8 individual LHC cryoplants, the very high ratio of dynamic heat load to static heat load, combined with the high power density at various sites produces interesting challenges for the cryogenic distribution system. A schematic view of the design choices selected, some of which are different from existing large cryogenic systems, and the basis for these decisions, is presented in this paper.

MOPPP034	Simulation of the Longitudinal Phase Space Measurement with Transverse Deflecting Structure at PITZ	electron, dipole, emittance, simulation	637
	D. Malyutin, M. Krasilnikov, M. Otevřel, F. Stephan DESY Zeuthen, Zeuthen, Germany
	The main goal of the Photo Injector Test facility at DESY, Zeuthen site, (PITZ) is the development, optimization and detailed characterization of electron sources for the short wavelength Free Electron Lasers (FELs) like FLASH and the European XFEL. For successful operation of such type of FELs the injector must provide high quality electron bunches, enough short in duration with high charge and small transverse and longitudinal emittance values. Installation of the Transverse Deflecting Structure (TDS) at PITZ will provide the possibility for detailed characterization of bunch temporal profile, bunch transverse slice emittance and longitudinal phase space. The TDS cavity is currently installed at the PITZ beamline, and commissioning of the whole TDS system is expected in the spring 2012. In the first part of the paper the basic principles of the TDS deflector are described. In the next section, simulation of measurements by TDS cavity applied to the PITZ beam parameters is presented. The temporal resolution for different types of measurements is discussed. Systematic limitations are estimated.

MOPPP035	Initial Emittance and Temporal Response Measurement for GaAs Based Photocathodes	electron, cathode, emittance, laser	640
	S. Matsuba Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan Y. Honda, T. Miyajima, T. Uchiyama, M. Yamamoto KEK, Ibaraki, Japan X.G. Jin Institute for Advanced Research, Nagoya, Japan Y. Takeda Nagoya University, Nagoya, Japan
	For future light source based on Energy Recovery Linac (ERL) is planned in KEK. For the ERL, an ultra low emittance and fast temporal response and high current electron source is needed. To achieve these requirements, a high voltage DC gun with a Negative Electron Affinity photo-cathode is under development. In this development, it is important to investigate the performance of photo-cathodes. We have constructed an ERL gun test stand to measure emittance and temporal profile. We use a solenoid scan technique for emittance measurements and a deflecting cavity technique for temporal profile measurements. In this presentation, we introduce KEK ERL gun test stand and beam test results.

MOPPP045	Status of the Wisconsin SRF Gun	cathode, gun, laser, solenoid	661
	R.A. Legg, J. Bisognano, M.J. Bissen, R.A. Bosch, D. Eisert, M.V. Fisher, M.A. Green, K. Jacobs, R.G. Keil, K.J. Kleman, J.G. Kulpin, G.C. Rogers, M.C. Severson UW-Madison/SRC, Madison, Wisconsin, USA D. Yavuz UW-Madison/PD, Madison, Wisconsin, USA
	Funding: The University of Wisconsin SRF electron gun program is supported by DOE Award DE-SC0005264. SRF electron guns hold out the promise of very bright beams for use in electron injectors, particularly for light source applications such as Free Electron Lasers. The University of Wisconsin is midway in a multi-year program to demonstrate a low frequency electron gun based on a quarter wave resonator cavity. The design includes active tuning and a high temperature superconducting solenoid for emittance compensation. We will report on the status of the 4 MeV SRF electron gun, including the cryomodule, the RF power coupler, the main RF power amplifier/low level RF control system, the photocathode laser system, and the diagnostic beamline. Installation is moving forward in a recently renovated experimental vault adjacent to the existing Aladdin synchrotron. First electron beam is expected in the summer 2012.

MOPPP047	Characterization of the First SRF Electron Beam Source at the Naval Postgraduate School	cathode, electron, SRF, coupling	667
	A.D. Holmes, A.B. Baxter, C.W. Bennett, J.R. Harris, J.W. Lewellen, R. Swent NPS, Monterey, California, USA J.M. Didoszak, J.M. Utschig ONR, Arlington, Virginia, USA
	In June 2011, the Naval Postgraduate school (NPS) received the 500 MHz Mark I quarter-wave superconducting RF (SRF) electron beam source and, among other firsts, completed the first cool down and characterization of an SRF beam source at a US Naval facility. The Mark I has a photocathode with adjustable position and uses a unique cascaded RF coupler design. As part of an on-going advanced electron source development project, the NPS Beam Physics Laboratory (BPL) team continues characterization of the Mark I cavity at various cathode stalk, coupler, and probe positions. Methods and experimentation used to measure the cavity Q and β, as well as characteristic results, with respect to coupler, cathode stalk, and probe positions are presented.

MOPPP076	Design Considerations for a Hybrid Undulator Applied in a Terahertz FEL Oscillator	undulator, FEL, electron, radiation	738
	B. Qin, M. Fan, Y.Q. Xiong Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China Y.J. Pei USTC/NSRL, Hefei, Anhui, People's Republic of China P. Tan HUST, Wuhan, People's Republic of China
	A planer undulator using hybrid permanent magnet scheme was designed for a FEL based 1THz~3THz radiation source. The influence of the undulator magnetic field errors, including peak field shift and field integrals errors, on the coherent radiation performance such as the gain per pass is investigated. And finally specifications of the undulator are determined.

MOPPR035	Study of the Signal Processing System for a Cavity Beam Position MonitorS	FEL, electron, factory, simulation	855
	B.P. Wang, Y.B. Leng, L.Y. Yu, W.M. Zhou SINAP, Shanghai, People's Republic of China Z.C. Chen, R.X. Yuan, N. Zhang SSRF, Shanghai, People's Republic of China
	A cavity beam position monitor (CBPM), which can realize nanometer-level resolution as reported, is important and indispensable for a free electron laser (FEL) facility. A prototype of CBPM, with resonant frequency of 5712 MHz, has been installed in the Shanghai deep ultraviolet free-electron laser source (SDUV-FEL) facility. A plug & play CBPM signal processor based on a broadband oscilloscope embedded IOC and FFT technology has been developed to do quick evaluation of prototype. According to the evaluation results, a series of simulation using Monte Carlo simulation method, has been carried as a guideline for the design of dedicated CBPM signal processing system. The development progress of signal processing system will be introduced as well.

MOPPR057	Development of a Cavity Beam Position Monitor for CLIC	dipole, linac, coupling, factory	915
	F.J. Cullinan, S.T. Boogert, N.Y. Joshi, A. Lyapin JAI, Egham, Surrey, United Kingdom E. Calvo, N. Chritin, F. Guillot-Vignot, T. Lefèvre, L. Søby CERN, Geneva, Switzerland A. Lunin, M. Wendt, V.P. Yakovlev Fermilab, Batavia, USA S.R. Smith SLAC, Menlo Park, California, USA
	The Compact Linear Collider (CLIC) project presents many challenges to its subsystems and the beam diagnostics in particular must perform beyond current limitations. The requirements for the CLIC main beam position monitors foresee a spacial resolution of 50 nm while delivering a 10 ns temporal resolution within the bunch train. We discuss the design of the microwave cavity pick-up and associated electronics, bench top tests with the first prototype cavity, as well as some of the machine-specific integration and operational issues.

MOPPR068	Design and Development of the Diagnostic System for 75 MeV Electron Drive Beam for the AWA Upgrade	diagnostics, controls, wakefield, emittance	942
	J.G. Power, S.P. Antipov, M.E. Conde, W. Gai, C.-J. Jing, W. Liu, E.E. Wisniewski, Z.M. Yusof ANL, Argonne, USA
	Funding: Work supported by High Energy Physics, Office of Science, US DOE We report on the development of the diagnostic system for the ongoing upgrade to the Argonne Wakefield Accelerator (AWA) facility where the electron drive beam energy will be increased from 15 to 75 MeV. The facility will produce a wide dynamic range of drive bunch train formats ranging from a single microbunch of 100 pC to bunch trains of up to 32 bunches spaced by 769 ps with up to 100 nC per bunch. In addition to standard diagnostics, this drive bunch train format poses two challenges for the diagnostic system: (i) the close spacing of the drive bunches, 769 ps, makes resolving the individual pulses difficult and (ii) the dynamic range of the bunch charge varies by x1000. A critical parameter of the drive bunch train for the wakefield accelerator is the charge along the train. To measure this, we are planning to use a 15 GHz digital oscilloscope to read either a BPM or Bergoz FCT. To handle the large dynamic range of charge, the imaging system will make use of GigE Vision cameras and a distributed system of motorized lenses, with remote control of focus, zoom, and aperture, which are operated through terminal servers and RS232 controllers.

MOPPR069	Use of Waveguide and Beam Pipe Probes as Beam Position and Tilt Monitoring Diagnostics with Superconducting Deflecting Cavities	dipole, HOM, monitoring, simulation	945
	X. Sun, T.G. Berenc, G. Decker, G.J. Waldschmidt, G. Wu ANL, Argonne, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357. Waveguide and beam pipe field probes associated with a superconducting deflecting cavity are explored as beam position and tilt monitoring diagnostics. The superconducting deflecting cavity will be used for the Short-pulse X-rays (SPX) in the Advanced Photon Source (APS) upgrade project. Microwave Studio will be used to simulate the techniques of detecting the fields excited by the beam passing through the cavity and determining how close the beam is on electrical center.

MOPPR070	Beam Profile Measurement in MTA Beam Line for High Pressure RF Cavity Beam Test	proton, diagnostics, linac, electron	948
	M.R. Jana, A.D. Bross, S. Geer, C. Johnstone, T. Kobilarcik, G.M. Koizumi, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, USA M. Chung Handong Global University, Pohang, Republic of Korea M.G. Collura Politecnico di Torino, Torino, Italy B.T. Freemire, P.M. Hanlet, Y. Torun IIT, Chicago, Illinois, USA
	Funding: This work is supported by the United States Department of Energy under contract DE-AC02-07CH11359. The recent High Pressure RF (HPRF) cavity experiment at the MuCool Test Area (MTA) used a 400 MeV Linac proton beam to study the beam loading effect. When the energetic proton beam passes through the cavity, it ionizes the inside gas and produces electrons. These electrons consume RF power inside the cavity. The number of electrons produced per cm inside the cavity (at 950 psi Hydrogen gas) per incident proton is 1200. The measurement of beam position and profile are necessary. The MTA is a flammable gas (Hydrogen) hazard zone, so we have developed a passive beam diagnostic instrument using a Chromox-6 scintillation screen and CCD camera. This paper presents quantitative information about beam position and beam profile. A neutral density filter was used to avoid saturation of the CCD camera. Image data is filtered and fitted with a Gaussian function to compute the beam size. The beam profile obtained from the scintillation screen will be compared with a multi-wire beam profile.

MOPPR073	Analysis of Resonant TE Wave Modulation Signals for Electron Cloud Measurements	electron, resonance, coupling, factory	957
	S. De Santis LBNL, Berkeley, California, USA D. Alesini INFN/LNF, Frascati (Roma), Italy J.P. Sikora CLASSE, Ithaca, New York, USA
	Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the US Department of Energy under Contracts DE-FC02-08ER41538, DE-AC02-05CH11231. Recent TE wave measurements of the electron cloud density in the beampipe at CesrTA and DAΦNE have shown that, especially near cutoff, the microwave excitation takes place by coupling to a standing wave, rather than to a propagating TE mode. With the beampipe acting as a resonant cavity, the effect of the periodic electron cloud density is a modulation of the cavity's resonant frequency. As a result, the measured sidebands are a combination of amplitude, phase, and frequency modulation, as the periodic cloud density modulates this resonant frequency. The quality factor Q of the resonance will determine its response to transients in the electron cloud density, and the resulting effect on modulation sidebands. In order to estimate the peak electron cloud density and its spacial distribution, knowledge of the Q and the standing wave pattern need to be determined, either by experimental measurements or simulation codes. In this paper we analyze the dependence of the modulation sidebands on the electron cloud density in two different regimes, when the cloud rise/decay time is much longer, or much shorter than the filling time of the resonance.

MOPPR074	Using TE Wave Resonances for the Measurement of Electron Cloud Density	resonance, electron, simulation, vacuum	960
	J.P. Sikora, M.G. Billing, D. L. Rubin, R.M. Schwartz CLASSE, Ithaca, New York, USA D. Alesini INFN/LNF, Frascati (Roma), Italy B.T. Carlson CMU, Pittsburgh, Pennsylvania, USA S. De Santis LBNL, Berkeley, California, USA K.C. Hammond Harvard University, Cambridge, Massachusetts, USA
	Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the US Department of Energy under Contracts DE-FC02-08ER41538, DE-AC02-05CH11231. In the past few years, electron cloud density has been measured by means of its effect on TE waves propagated through the accelerator vacuum chamber. This technique has been the object of careful studies and has been used in several laboratories around the world (CERN, SLAC, FNAL, Cornell, INFN-LNF). Recent measurements at CesrTA and DAΦNE show that in a majority of practical cases, the theoretical model that relates the cloud density to the phase shift induced on a TE wave propagating in beam pipe may not be the correct one. Instead, the measurement results have to be analyzed considering the effect of the electron cloud on a standing wave excited between the input and output couplers - typically Beam Position Monitors (BPMs). This standing wave pattern is not confined to the portion of beampipe between the BPMs and must be understood in order to correctly interpret the measurement. In this paper we present evidence that the transmission function near cutoff between two BPMs is the result of coupling to standing waves trapped in the vacuum chamber. This evidence includes measurements at DAΦNE, Cesr-TA, a test waveguide, computer EM simulations, and analytical calculations.

MOPPR088	Cavity BPM for 1300 MHz Cryomodules	coupling, dipole, wakefield, cryomodule	993
	N. Barov, D.J. Newsham, D. Wu Far-Tech, Inc., San Diego, California, USA
	Funding: Work supported by DOE grant DE-SC00004498 A cavity BPM for 1300 MHz cryomodules is under development by FAR-TECH, Inc. The BPM is capacitively loaded to fit in a small area, and uses a novel coupling scheme which further cuts down space requirements. We discuss status of the fabrication, and eventual plan to test the diagnostic at the ANL Wakefield Accelerator facility.

TUYA01	Research and Development of Future Muon Collider	collider, plasma, proton, emittance	1020
	K. Yonehara Fermilab, Batavia, USA
	A muon collider would provide a unique facility for future elementary-particle physics research, and present unique challenges for accelerator physics and technology. An R&D effort is underway to address major challenges in the design of a future muon collider. This talk should provide an opportunity to discuss the muon collider's challenges, present recent R&D results, and describe future prospects.

TUOAB01	Timing and Synchronization for the APS Short Pulse X-ray Project	laser, feedback, LLRF, storage-ring	1077
	F. Lenkszus, N.D. Arnold, T.G. Berenc, G. Decker, E.M. Dufresne, R.I. Farnsworth, Y.L. Li, R.M. Lill, H. Ma ANL, Argonne, USA J.M. Byrd, L.R. Doolittle, G. Huang, R.B. Wilcox LBNL, Berkeley, California, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Short-Pulse X-ray (SPX) project, which is part of the APS upgrade, will provide intense, tunable, high-repetition-rate picosecond x-ray pulses through the use of deflecting cavities operating at the 8th harmonic of the storage-ring rf. Achieving this picosecond capability while minimizing the impact to other beamlines outside the SPX zone imposes demanding timing and synchronization requirements. For example, the mismatch between the upstream and downstream deflecting cavities' rf field phase is specified to be less than 0.077 degrees root mean squared (rms) at 2815 MHz (~77 femtoseconds). Another stringent requirement is to synchronize beamline pump-probe lasers to the SPX x-ray pulse to 400 femtoseconds rms. To achieve these requirements we have entered into a collaboration with the Beam Technology group at LBNL. They have developed and demonstrated a system for distributing stable rf signals over optical fiber capable of achieving less than 20 femtoseconds rms drift and jitter over 2.2 km over 60 hours. This paper defines the overall timing/synchronization requirements for the SPX and describes the plan to achieve them. R. Wilcox et al. Opt. Let. 34(20), Oct 15, 2009
	Slides TUOAB01 [2.515 MB]

TUEPPB004	A Longitudinal Beam Dynamics Code for Proton Synchrotron	simulation, space-charge, synchrotron, bunching	1119
	Y.S. Yuan, N. Wang, S. Wang, S.Y. Xu IHEP, Beijing, People's Republic of China
	The accelerator of China Spallation Neutron Source (CSNS) consists of an 80 MeV linac and a 1.6 GeV Rapid Cycling Synchrotron (RCS). Longitudinal beam dynamics study is one of the most important issues for RCS beam dynamics design. However, the existing codes cannot meet the requirement of longitudinal beam dynamics for CSNS/RCS. A new code has been developed for longitudinal beam dynamics design and simulation. The code can perform the voltage and phase curves design for non-sinusoidal magnetic field of dipole in an RCS cycle, with the fundamental RF mode and dual harmonic mode. The code can also be used for the beam simulation with longitudinal space charge effect, including the effects of higher order mode of RF cavities. By using the code, the longitudinal beam dynamics of CSNS/RCS was designed and optimized, and the simulation study with dual harmonics higher order modes of RF cavity was done, and the simulation results are presented.

TUEPPB008	Status Report on the Iranian Light Source Facility Project	storage-ring, booster, synchrotron, dipole	1131
	J. Rahighi, H. Ajam, R. Aslani, S. Fatehi, H. Ghasem, M.R. Khabazi, R. Safian, E. Salimi, A. Shahveh IPM, Tehran, Iran E. Ahmadi, M. Jafarzadeh, H.B. Jalali, M. Moradi, S. Pirani, M. Rahimi, A. Sadeghipanah, F. Saeidi, Kh.S. Sarhadi, A. Shahverdi ILSF, Tehran, Iran D. Einfeld CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
	The Iranian Light Source Facility Project (ILSF) is a 3rd generation light source with an energy of 3 GeV,a full energy injector and a 100 MeV linac as preinjector. For storage ring, booster synchrotron and linac including the transfer lines, a draft design has been completed and will be presented. The storage ring has an emittance of 3.3 nm-rad, a circumference of 297.6 meters with an overall of 32 straight sections of different lengths. The booster synchrotron has a circumference of 197 meters and emittance of 35nm-rad. For the booster synchrotron a new lattice is proposed. The linac is a conventional 150 MeV accelerator. The different accelerator components, magnets, girders, power supplies, vacuum systems etc. are in the design phase. State of the art design for different components is employed through international collaboration.

TUPPC010	Study of Effects of Failure of Beamline Elements and its Compensation in CW Superconducting Linac	linac, beam-losses, emittance, focusing	1173
	A. Saini, K. Ranjan University of Delhi, Delhi, India C.S. Mishra, J.-F. Ostiguy, N. Solyak, V.P. Yakovlev Fermilab, Batavia, USA
	Project-X is the proposed high intensity proton facility to be built at Fermilab in United States. First stage of the Project-X consists of H^- superconducting linac (SC) which will be operated in continuous wave (CW) mode to accelerate the beam from kinetic energy of 2.1 MeV to 3 GeV. The operation in CW mode puts stringent tolerances on the beam line components, particularly at low energy section. The failure of beam line elements result in mismatch of the beam with the following sections due to different beam parameters than designed parameters. It makes the beam unstable which causes emittance dilution, and ultimately results in beam losses. In worst case, it can affect the reliability of the machine and may lead to the shutdown of the linac to replace the failed elements. Thus, it is important to study impacts of these effects and their compensation to restore linac performance to avoid beam interruption. This paper presents the studies performed for the failure of accelerating cavity and focusing magnets at the critical locations in the Project-X CW superconducting linac

TUPPC011	Beam Steering Correction in FRIB Quarter-wave Resonators	linac, simulation, cryomodule, solenoid	1176
	A. Facco INFN/LNL, Legnaro (PD), Italy A. Facco, Y. Xu, Y. Zhang, Q. Zhao, Z. Zheng FRIB, East Lansing, Michigan, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 The Quarter-Wave Resonators (QWR) section of the FRIB superconducting driver linac is required to accelerate Uranium beam up to 16 MeV/u in two different charge states simultaneously. This puts severe requirements on resonators alignment and field quality, in order to avoid beam losses and emittance growth. In particular, QWR beam steering can cause transverse oscillations of the beam centroid which reduce the linac acceptance and induces emittance growth. We have studied, with an analytical model and with 3D beam dynamics simulations, correction methods for the FRIB QWRs steering. We found that cavity shifting can provide effective steering cancellation in FRIB QWRs without need of cavity shape modifications, and allows to eliminate transverse beam oscillations and to improve beam quality. Calculation and simulation methods and results will be presented and discussed. Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics.

TUPPC026	Design of Compact C-Band Standing-Wave Accelerating Structure Enhancing RF Phase Focusing	coupling, bunching, focusing, simulation	1221
	H.R. Yang, M.-H. Cho, J. Jang, S.H. Kim, W. Namkung, S.J. Park POSTECH, Pohang, Kyungbuk, Republic of Korea J.-S. Oh NFRI, Daejon, Republic of Korea
	Funding: Work supported by POSTECH Physics BK21 Program. We design a C-band standing-wave accelerating structure for an X-ray source of the imaging and medical applications. It is capable of producing 6-MeV, 100-mA pulsed electron beams which is focused by less than 1.5 mm without external magnets. As an RF source, we use peak 1.5-MW magnetron with duty factor of 0.08%. The accelerating structure is a bi-periodic and on-axis-coupled structure with a built-in bunching section, which consists 3 bunching cells, 13 normal cells and a coupler cell. It operated with π/2-mode standing-waves. The bunching section is designed to enhance the RF phase focusing in order to achieve 1.2-mm beam spot size. Each cavity is designed with the MWS code to maximize the effective shunt impedance within 3.5% inter-cell coupling. In this paper, we present design details of RF cavities and the beam dynamics simulation by the PARMELA code.

TUPPC045	Modeling Investigation on a Deflecting-Accelerating Composite RF-cavity System for Phase Space Beam Control	coupling, simulation, klystron, electron	1266
	Y.-M. Shin, M.D. Church, P. Piot Fermilab, Batavia, USA
	Phase space manipulations between the longitudinal and transverse degree of freedoms hold great promise toward the precise control of electron beams. Such transverse-to-longitudinal phase space exchange have been shown to be capable of exchanging the transverse and horizontal emittance or controlling the charge distribution of an electron bunch, for beam-driven advanced accelerator methods. The main limitation impinging on the performance of this exchange mechanism stems from the external coupling nature of a realistic deflecting cavity, compared to a thin-lens model. As an extended idea from , this paper presents the design of a composite 3.9-GHz RF-system consisting of a deflecting- and accelerating-mode cavities. The system design analysis is discussed with particle-in-cell (PIC) simulations of the device performance. A. Zholents, PAC'11.

TUPPC053	Longitudinal Tuning of the SNS Superconducting Linac	linac, optics, acceleration, controls	1290
	T.V. Gorlov ORNL, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy. The SNS superconducting linac delivers proton beam with about 1 GeV of energy driven by self-consistent RF cavities. Here, we present an experience of the longitudinal tune-up of the SNS superconducting linac where a new application for quick RF phase setup and cavity fault adaptation was created. The routine of superconducting linac tune-up, longitudinal beam manipulation, and radio frequency cavity phase scaling for beam state recovery is presented. The application has direct value for beam optics study and will serve as the basis for longitudinal beam-size manipulation for a laser stripping project.

TUPPC054	Beam Acceleration by a Multicell RF Cavity Structure Proposed for Improved Yield in Hydroforming	electron, acceleration, quadrupole, focusing	1293
	J.A. Holmes, Y.W. Kang ORNL, Oak Ridge, Tennessee, USA A.E. Fathy, K.R. Shin University of Tennessee, Knoxville, Tennessee, USA
	Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. We study the accelerating properties of a new multicell cavity structure with irises forming a rectangular aperture between the cavity cells. We are interested in this structure because, from a mechanical point of view, the rectangular iris may make possible a much improved structure quality using a hydroforming manufacturing process. RF analysis shows that the rectangular iris shape provides asymmetric transverse focusing per half RF period. If the horizontal and vertical rectangular irises are interleaved, the net transverse focusing can be increased. The present studies of the acceleration and transport properties of these cavities are conducted by tracking particles through time-dependent 3D cavity fields from CST MWS using the ORBIT Code.

TUPPD003	Optimisation of Cooling Lattice Based on Bucked Coils for the Neutrino Factory	lattice, factory, emittance, simulation	1407
	A. Alekou, J. Pasternak Imperial College of Science and Technology, Department of Physics, London, United Kingdom
	The ionisation cooling technique will be used at the Neutrino Factory to reduce the transverse phase space of the muon beam. For efficient cooling, high average RF gradient and strong focusing are required to be applied in the cooling channel. However, high magnetic field at the position of the RF cavities induces electric field breakdown and therefore, a novel configuration, the Bucked Coils lattice, has been proposed to mitigate this problem. The Bucked Coils lattice has significantly lower magnetic field in the RF cavities by using coils of different radius and opposite polarity. This paper presents the optimisation of this lattice, its cooling performance, together with the preliminary conceptual engineering design.

TUPPD006	IDR Neutrino Factory Front End and Variations	proton, target, factory, solenoid	1416
	D.V. Neuffer Fermilab, Batavia, USA A. Alekou Imperial College of Science and Technology, Department of Physics, London, United Kingdom C.T. Rogers STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom P. Snopok IIT, Chicago, Illinois, USA C. Y. Yoshikawa Muons, Inc, Batavia, USA
	The (International Design Report) IDR neutrino factory scenario for capture, bunching, phase-energy rotation and initial cooling of muons produced from a proton source target is presented. It requires a drift section from the target, a bunching section and a phase-energy rotation section leading into the cooling channel. The rf frequency changes along the bunching and rotation transport in order to form the muons into a train of equal-energy bunches suitable for cooling and acceleration. This design is being explored within the IDR cost model. Important concerns are rf limitations and beam losses. Recent experiments on rf gradient limits suggest preferred configurations for the rf within the magnetic fields, and these considerations are incorporated into the front end design.

TUPPD010	Helical Muon Beam Cooling Channel Engineering Design	solenoid, simulation, beam-cooling, collider	1425
	G. Flanagan, R.P. Johnson, G.M. Kazakevich, F. Marhauser, M.L. Neubauer Muons, Inc, Batavia, USA V.S. Kashikhin, M.L. Lopes, G.V. Romanov, M.A. Tartaglia, K. Yonehara, M. Yu, A.V. Zlobin Fermilab, Batavia, USA
	Funding: Supported in part by DOE STTR Grant DE-SC0006266 The Helical Cooling Channel (HCC), a novel technique for six-dimensional (6D) ionization cooling of muon beams, has shown considerable promise based on analytic and simulation studies. However, the implementation of this revolutionary method of muon cooling requires new techniques for the integration of hydrogen-pressurized, high-power RF cavities into the low-temperature superconducting magnets of the HCC. We present the progress toward a conceptual design for the integration of 805 MHz RF cavities into a 10 T Nb3Sn based HCC test section. We include discussions on the pressure and thermal barriers needed within the cryostat to maintain operation of the magnet at 4.2 K while operating the RF and energy absorber at a higher temperature. Additionally, we include progress on the Nb3Sn helical solenoid design

TUPPD014	To the Ionization Cooling in a RF Cavity with Absorber	scattering, focusing, radiation, emittance	1437
	A.A. Mikhailichenko CLASSE, Ithaca, New York, USA
	We are considering a RF cavity with Beryllium disk installed in the middle of the cavity as a ionization cooling element for the muon beam. Specially arranged shape of disk together with nonzero dispersion allows 6D cooling of muon beam. Technical aspects of this system and conceptual design are discussed in this paper also. This type of cooler demonstrates advantages if compared with the RF cavity filled with pressurized gas or with the helical cooler.

TUPPD017	Electromagnetic Design of RF Cavities for Accelerating Low-Energy Muons	linac, vacuum, resonance, solenoid	1446
	S.S. Kurennoy LANL, Los Alamos, New Mexico, USA
	A high-gradient linear accelerator for accelerating low-energy muons and pions in a strong solenoidal magnetic field has been proposed for homeland defense and industrial applications.* The acceleration starts immediately after collection of pions from a target in a solenoidal magnetic field and brings decay muons, which initially have kinetic energies mostly around 15-20 MeV, to 200 MeV over a distance of ~10 m. At this energy, both ionization cooling and further, more conventional acceleration of the muon beam become feasible. A normal-conducting linac with external-solenoid focusing can provide the required large beam acceptances. The linac consists of independently fed zero-mode (TM010) RF cavities with wide beam apertures closed by thin conducting edge-cooled windows. Electromagnetic design of the cavity, including its RF coupler, tuning and vacuum elements, and field probes, has been developed with the CST MicroWave Studio, and will be presented. * S.S. Kurennoy, A.J. Jason, H. Miyadera, “Large-Acceptance Linac for Accelerating Low-Energy Muons.” Proceed. IPAC10, p. 3518.

TUPPD019	New Injector for the EMMA ns-FFAG Ring	booster, gun, linac, emittance	1449
	B.D. Muratori STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	EMMA is the world’s first non-scaling FFAG which has recently demonstrated acceleration in the serpentine channel. At present, the electron beam is injected into EMMA from the ALICE accelerator. However, funding will be re-directed to an Electron Beam Test Facility (EBTF) in the near future, therefore, in order to continue the broad portfolio of planned experiments required to characterize non-scaling FFAGs, it essential to consider an alternative injection scheme. In this paper, we propose re-utilizing a thermionic gun and a 12 MeV linac from the SRS (Synchrotron Radiation Source) at Daresbury Laboratory. The paper looks at how the required EMMA beam properties can be matched with this new set-up and the advantages and disadvantages involved.

TUPPD034	Multi-bunch Beam Generation by Photo-cathode RF Gun for KEK-STF	laser, gun, cathode, electron	1479
	M. Kuriki, S. Hosoda, H. Iijima HU/AdSM, Higashi-Hiroshima, Japan A. Ayaka Sokendai, Ibaraki, Japan H. Hayano, J. Urakawa, K. Watanabe KEK, Ibaraki, Japan G. Isoyama, R. Kato, K. Kawase ISIR, Osaka, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan K. Sakaue RISE, Tokyo, Japan
	Funding: MEXT, Quantum beam project. KEK-STF is doing R&D of Super-Conducting (SC) accelerator technology for ILC (International Linear Collider), based on 1.3 GHz RF system. For STF and ILC, the pulse length is 1ms and the repetition is 5Hz. We developed a L-band Normal-Conducting RF gun designed by DESY to provide electron beam over such long pulse duration. For NC Photo-cathode RF gun, such high duty and long pulse operation is a challenging task, because the detuning by the heat load of cavity dissipation power is significant. The RF gun provides the electron pulse train to SC accelerator modules which will be operated at 31.5 MV/m gradient. Precise RF control is essential for SC accelerator because the beam loading and input RF power should be well ballanced for a stable operation. The beam test to demonstrate the stable opeation is very important for SC accelerator R&D. The system is also used to demonstrate high-flux quasi-monochromatic X-ray generation by inverse Compton scattering at KEK-STF. The experiment is carried out from April 2012 to November 2012 at KEK-STF. We report the latest status of the multi-bunch generation by the RF gun.

TUPPD051	Operational Experience with the Nb/Pb SRF Photoelectron Gun	emittance, cathode, solenoid, laser	1518
	T. Kamps, W. Anders, R. Barday, A. Jankowiak, J. Knobloch, O. Kugeler, A.N. Matveenko, A. Neumann, T. Quast, J. Rudolph, S.G. Schubert, J. Völker HZB, Berlin, Germany P. Kneisel JLAB, Newport News, Virginia, USA R. Nietubyć The Andrzej Soltan Institute for Nuclear Studies, Centre Świerk, Świerk/Otwock, Poland J.K. Sekutowicz DESY, Hamburg, Germany J. Smedley BNL, Upton, Long Island, New York, USA J. Teichert HZDR, Dresden, Germany V. Volkov BINP SB RAS, Novosibirsk, Russia I. Will MBI, Berlin, Germany
	SRF photoelectron guns offer the promise of high brightness, high average current beam production for the next generation of accelerator driven light sources such as free electron lasers, THz radiation sources or energy-recovery linac driven synchrotron radiation sources. In a first step a fully superconducting RF (SRF) photoelectron gun is under development by a collaboration between HZB, DESY, JLAB, BNL and NCBJ. The aim of the experiment is to understand and improve the performance of a Nb SRF gun cavity coated with a small metallic Pb cathode film on the cavity backplane. This paper describes the highlights from the commissioning and beam parameter measurements. The main focus is on lessons learned from operation of the SRF gun.

TUPPD056	Development of a Photo-injector Laser System for KEK ERL Test Accelerator	laser, cathode, controls, alignment	1530
	Y. Honda KEK, Ibaraki, Japan
	As a test accelerator for future light source, Compact Energy Recovery Linac has been constructed in KEK. For its photo-injector, we have been developing a laser system. It requires high repetition rate and high average power at a visible wavelength. Development of an high power fiber amplifier and high efficiency wavelength conversion system utilizing an optical cavity will be reported.

TUPPD058	Development of an RF Electron Gun for Ultra-Short Bunch Generation	gun, electron, cathode, simulation	1536
	Y. Koshiba, T. Aoki, K. Sakaue, M. Washio RISE, Tokyo, Japan T. Takatomi, J. Urakawa KEK, Ibaraki, Japan
	At Waseda University, various researches are done using a photocathode rf electron gun with a 1.6 cell cavity. Now we are developing a new rf cavity specialized for producing an ultra-short electron bunch, with the collaboration of High Energy Accelerator Research Organization (KEK). We have used SUPERFISH for designing the new rf cavity and PARMELA for beam tracking. The new rf cavity has an extra cell following the 1.6 cell. The extra cell can chirp the energy of electron bunch so we call it ECC (Energy Chirping Cell). ECC chirp the energy because we shortened the length of iris just before the ECC and also the length of ECC itself. Moreover, electric field in ECC is made to be stronger than others. We have confirmed on PARMELA that ECC rf gun can generate an 100pC electron bunch less than 200fsec with the energy of 4.5MeV at about 2.5m away from the cathode. Such an ultra-short electron bunch enables us to generate a coherent terahertz light using ultra-short electron bunch by synchrotron radiation or transition radiation. In this conference, we would like to introduce the detail of the design of this new ECC rf gun, the present progresses and future prospects.

TUPPD062	The Source of Emittance Dilution and photoemission tunneling effect in Photocathode RF Guns	cathode, emittance, laser, simulation	1542
	V. Volkov BINP SB RAS, Novosibirsk, Russia R. Barday, T. Kamps, J. Knobloch, A.N. Matveenko, S.G. Schubert, J. Völker HZB, Berlin, Germany J.K. Sekutowicz DESY, Hamburg, Germany
	Funding: Work supported by Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association VH-NG-636 and HRJRG-214. Experimental data on HoBiCaT SRF photoinjector give an emittance which is much larger than the predicted thermal emittance. Modeling of photocathode RF gun beams with the different imperfections of experimental setup (alignment errors, inhomogeneity of quantum efficiency and laser power distributions on the cathode) is given. The main reason for the beam emittance dilution is photocathode field imperfections induced by field emitters that change the local electric field. Some field models of such photocathodes are tested in the simulations. The dependence of photocathode beam currents on the surface electric field was measured with the HoBiCaT SRF Photoinjector. The dependence can be explained by the tunneling effect described by Fowler-Nordheim like equation and is difficult to explain by usually applying Schottky effect.

TUPPD063	Interpretation of Dark Current Experimental Results in HZB SC RF Gun	simulation, accelerating-gradient, gun, HOM	1545
	V. Volkov BINP SB RAS, Novosibirsk, Russia R. Barday, T. Kamps, J. Knobloch, A.N. Matveenko, A. Neumann HZB, Berlin, Germany
	Funding: Work supported by Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association VH-NG-636 and HRJRG-214. The experimental dark current measurement results are obtained on HZB SC RF gun. The field emitters are considered to be random defects on the back wall of the cavity. Conducting wires with 1 micron length, blobs of 200 micron diameter and ”tip on tip” combination of them are taken as dark current emitters in the cavity. RF fields were calculated with CLANS program. The dynamic simulation of dark currents from these emitters fit experimental data. The emitter heating power by RF induced current is four orders of magnitude larger than by the field emitted dark current. The RF induced emitter temperature is proportional to ω1/2 which explains the accelerating gradient limit of a cavity like Kilpatrik law. The RF processing by high order modes seems to be promising.

TUPPD064	Cathode Insert Design for SC RF Guns	cathode, gun, multipactoring, HOM	1548
	V. Volkov BINP SB RAS, Novosibirsk, Russia R. Barday, T. Kamps, J. Knobloch, A.N. Matveenko HZB, Berlin, Germany
	Funding: Work supported by Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Assiciation VH-NG-636 and HRJRG-214. The cathode inserts in superconducting (SC) RF guns are normal conducting devices attached to a SC RF gun cavity. They enable the photocathode replacement and, at the same time, preserve high quality factor and high fields in the RF guns. However, the insert may also limit the gun performance because of multipacting etc. The experience gathered in early designs at Wuppertal [1], and, more recently at BNL [2] and HZDR [3] is taken into account. We consider the design structure of the cathode insert worked out by BINP for 1 cell prototype of SC HZDR RF gun [4]. The detailed electric, mechanic, and thermal calculations of the initial [4] and the upgraded design are presented in this paper. * A. Michalke et al., EPAC'92, p. 1014 (1992). A. Burrill et al., PAC07, p. 2544 (2007). * D. Janssen et al., NIM A507, 314 (2003). **** D. Janssen et al., NIM A445, 408 (2000).

TUPPD068	Design of the Production and Measurement of Ultra-Short Electron Bunches from an S-band RF Photoinjector	gun, dipole, electron, laser	1560
	J.W. McKenzie, D. Angal-Kalinin, J.K. Jones, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The Electron Beam Test Facility (EBTF) is planned for installation in late 2012 at Daresbury Laboratory. An S-band RF photoinjector provides ultrashort, low emittance electron bunches up to 6 MeV. A suite of diagnostics has been designed to fully characterise the bunches. A particular focus has been on producing and measuring bunch lengths less than 100 fs. This can be achieved with a multi-cell standing wave S-band transverse deflecting cavity. Operating such a cavity with low energy electrons provides certain challenges which are discussed in this paper with respect to beam dynamic simulations.

TUPPD077	SPEAR3 Booster RF System Upgrade: Performance Requirements and Evaluation of Resources	booster, klystron, injection, linac	1578
	S. Park, W.J. Corbett, R.O. Hettel, J.F. Schmerge, J.J. Sebek, J.W. Wang SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences. The SPEAR2 accelerator system originally had 3 RF stations (2 for storage ring, 1 Booster) operating at 358.5 MHz. SPEAR3 now operates at 476.3 MHz with PEP-II type RF system, while the Booster RF frequency remains unchanged. For top-off operation, the Booster injects single 3.0 GeV electron bunches into SPEAR3 at 10 Hz every 5 minutes to replenish lost charge. Due to the frequency mismatch between SPEAR3 and the Booster, only one SPEAR3 bucket can injected per shot limiting injection rate and overall system flexibility. The aging high-power RF subsystems of the Booster pose a reliability issue as well. In order to remove these constraints, studies are underway to replace the Booster RF system using the PEP-II type RF system as a baseline. The new Booster RF system will be tuned to 475.036 MHz, and phase-locked to the SPEAR3 RF system. The project calls for ramping the Booster cavity gap voltage to 0.80 MV at 10 Hz, each with a 40 ms acceleration interval. With very low beam loading and low average RF power, there are many subsystems that can be operationally simplified. In this paper we present the results of analysis leading to a new Booster RF system.

TUPPD078	A Novel Design of a High Brightness Superconducting RF Photoinjector Gun Cavity	gun, SRF, cathode, emittance	1581
	F. Marhauser, R. Rodriguez MuPlus, Inc., Newport News, USA Z. Li SLAC, Menlo Park, California, USA
	Funding: Work supported under U.S. DOE Grant Application Number 98802B12-I Next generation electron accelerators for research, medical, defense or industrial use are in need of electron sources operating at high repetition rates of 1 MHz and beyond, with normalized emittance of 1 mm-mrad or less and bunch charges as much as one nC or more. A conceptual layout of a novel superconducting RF photoinjector gun cavity (SRF gun) is proposed, which can provide unprecedented flexibility to vary beam pulse patterns in the MHz regime and beyond at average currents around 1 mA. It does not require an opening in the center of the back wall and avoids the complex cathode exchange system, but still allows an exchange or refurbishment of the cathode. The demountable back plate has the major benefit to clean the cavity cells independently from the back wall carrying a superconductive photocathode. This mitigates risks of cavity contamination and eases fabrication and chemical post-processing to achieve high accelerating fields, a key parameter to guarantee high brightness beams.

TUPPP003	Status and Very First Commissioning of the ASTRID2 Synchrotron Light Source	septum, vacuum, dipole, synchrotron	1605
	S.P. Møller, N. Hertel, J.S. Nielsen ISA, Aarhus, Denmark
	ASTRID2 is the new 10 nm UV and soft x-ray light source currently being built at Aarhus University, to replace the ageing source ASTRID. ASTRID2 is now in the end of its installation phase, with commissioning expected to take place during the spring. The status of the installation together with the first results of the commissioning will be presented.

TUPPP042	Passive Landau Cavity Effects in the NSLS-II Storage Ring	storage-ring, simulation, impedance, wakefield	1701
	G. Bassi, A. Blednykh, S. Krinsky BNL, Upton, Long Island, New York, USA
	Funding: Work supported by DOE contract No: DE-AC02-98CH10886. In new 3rd generation synchrotron light sources with small transverse emittance, higher harmonic cavities (Landau cavities) are installed for bunch lengthening to increase the Touschek lifetime, and to provide Landau damping for beam stability. In this contribution we study the effects of passive Landau cavities in the NSLS-II storage ring for arbitrary fill-patterns with the OASIS tracking code.

TUPPP043	Analysis of Coupled Bunch Instabilities in the NSLS-II Storage Ring with a 7-cell PETRA-III RF Structure	HOM, impedance, damping, simulation	1704
	G. Bassi, A. Blednykh, S. Krinsky, J. Rose BNL, Upton, New York, USA
	Funding: Work supported by DOE contract No: DE-AC02-98CH10886. A 7-cell PETRA-III cavity is considered to be installed for the commissioning Phase 1 in the NSLS-II storage ring at an average current of 25mA. In this contribution we study transverse and longitudinal coupled-bunch instabilities that may be driven by the higher order modes of the 7-cell PETRA-III cavity. The instability thresholds are calculated with the OASIS tracking code, with parameters of the bare lattice (no damping wigglers and Landau cavities). We study multibunch configurations with arbitrary fill-patterns and discuss the slow head-tail effect at positive chromaticity to increase the transverse instability thresholds.

TUPPP059	Effects of Metal Mirrors Reflectivity and Aberrations on THz FEL Radiation Performance	FEL, radiation, undulator, electron	1729
	P. Tan, T. Yu HUST, Wuhan, People's Republic of China M. Fan, Q. Fu, D. Li, B. Qin, Y.Q. Xiong, Y.B. Yibin Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China
	The primary design study of terahertz free-electron laser (FEL) is presented in this paper. The effects of optical cavity parameter, metal mirrors reflectivity and aberrations on the THz FEL radiation performance have been explored. The reflectivity characteristics of copper, silver and gold are tested in terahertz region. The effects of metal mirrors reflectivity and aberrations on the THz FEL radiation performance are studied by numerical simulation.

TUPPP068	Comparison of Compression Schemes for CLARA	emittance, FEL, linac, sextupole	1756
	P.H. Williams, J.W. McKenzie STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom J.K. Jones, P.H. Williams Cockcroft Institute, Warrington, Cheshire, United Kingdom
	CLARA (Compact Linear Advanced Research Accelerator) at Daresbury Laboratory is proposed to be the UK’s national FEL test facility. The accelerator will be a ~250 MeV electron linac capable of producing short, high brightness electron bunches. The machine comprises a 2.5 cell RF photocathode gun, one 2 m and three 5 m normal conducting S-band (2998MHz) accelerating structures and a variable magnetic compression chicane. CLARA will be used as a test bed for novel FEL configurations. We present a comparison of acceleration and compression schemes for the candidate machine layout.

TUPPR026	Conceptual Design of the CLIC Damping Ring RF System	damping, beam-loading, linac, coupling	1870
	A. Grudiev CERN, Geneva, Switzerland
	In order to achieve high luminosity in CLIC, ultra-low emittance bunches have to be generated in both electron and positron damping rings. To achieve this goal, big energy loss per turn in the wigglers has to be compensated by the RF system. This results in very strong beam loading transients affecting the longitudinal bunch position and bunch length. In this paper, conceptual design of the RF system for the CLIC damping ring is presented. Baseline and several alternatives are discussed and the corresponding requirements for the cavities and the RF power sources are presented in order to meet stringent tolerances on the bunch-to-bunch phase and bunch length variations.

TUPPR027	Study of Multipolar RF Kicks from the Main Deflecting Mode in Compact Crab Cavities for LHC	multipole, dipole, simulation, coupling	1873
	A. Grudiev, J. Barranco, R. Calaga, R. De Maria, M. Giovannozzi, R. Tomás CERN, Geneva, Switzerland
	A crab cavity system is under design in the frame work of the High Luminosity LHC project. Due to transverse space constraints on one hand and the RF frequency requirements on the other hand, the design of the crab cavities has to be compact. This results in the crab cavity shape being far from axially symmetric and, as a consequence, higher order multipolar components of the main deflecting mode are non-zero. In this paper, multipolar RF kicks from the main deflecting mode have been calculated in the compact crab cavities for LHC. They are compared to the multipolar error in magnetic elements of LHC. The influence of the RF kicks on the beam dynamics has been investigated and possible acceptable tolerances are presented.

TUPPR032	Beam Stability at CTF3	feedback, klystron, pick-up, linac	1888
	T. Persson, P.K. Skowroński CERN, Geneva, Switzerland
	The two beam acceleration tested in CTF3 imposes very tight tolerances on the drive beam stability. A description of the specialized monitoring tool developed to identify the drifts and jitter in the machine is presented. It compares all the relevant signals in an on-line manner for helping the operator to identify drifts or to log data for off-line analysis. The main sources for the drifts of the drive beam were identified and their causes are described. Feedbacks applied to the RF were implemented to reduce the effects. It works by changing the waveform for the pulse compression to compensate for the drifts.

TUPPR037	Simulations of Higher Order Modes in the ACC39 Module of FLASH	HOM, dipole, higher-order-mode, simulation	1900
	I.R.R. Shinton, R.M. Jones, P. Zhang UMAN, Manchester, United Kingdom Z. Li SLAC, Menlo Park, California, USA
	This study is primarily focused on the dipole component of the multiband expansion of the wakefield, with the emphasis being on the development of a HOM-based BPM system for ACC39 currently installed and in operation at FLASH and due to be installed at XFEL . Coupled inter-cavity modes are simulated together with a limited band of trapped modes. A suite of finite element computer codes (including HFSS and ACE3P) and globalised scattering matrix calculations (GSM) are used to investigate the modes in these cavities. In this way the nature of the multi-cavity nature of these modules is investigated with implications for a HOM-based BPM system and direct comparison to experimental results.

TUPPR045	Multi-cell VEP Results: High Voltage, High Q, and Localized Temperature Analysis	radiation, SRF, controls, monitoring	1918
	F. Furuta, B. Elmore Cornell University, Ithaca, New York, USA A.C. Crawford Fermilab, Batavia, USA G.M. Ge, G.H. Hoffstaetter, M. Liepe CLASSE, Ithaca, New York, USA
	We are developing Vertical Electro Polishing (VEP) system for niobium superconducting RF cavity at Cornell University. VEP has been successfully applied on different cell shapes (TESLA and Re-entrant), and single and multi-cell cavities. VEP achieved high gradient of 39MV/m with TESLA shape single cell and of 36MV/m with TESLA shape 9-cell, respectively. Preliminary results of R&D on VEPed cavities show removal dependence on cavity performance. Temperature oscillation asymmetry was also found during the VEP process. We will report these recent results and further R&D plan of Cornell VEP.

TUPPR049	An X-band Standing Wave Dielectric Loaded Accelerating Structure	multipactoring, coupling, simulation, resonance	1927
	C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow Euclid TechLabs, LLC, Solon, Ohio, USA S.H. Gold NRL, Washington, DC, USA S. Kazakov Fermilab, Batavia, USA R. Konecny ANL, Argonne, USA
	Funding: DOE SBIR Phase I grant #DE-SC0006303 An 11.4 GHz standing wave dielectric loaded accelerating structure was recently developed. We expect to achieve a 120 MV/m gradient powered by a 10 MW 200 ns rf pulse from the X-band Magnicon at the Naval Research Laboratory. The structure uses on-axis rf coupling, which helps to localize the maximum EM fields within the dielectric region. Bench testing shows excellent agreement with the simulation results. The high power rf test is scheduled for January 2012.

TUPPR050	Design and simulation of Prebuncher for S-band Traveling Linear Accelerator	coupling, simulation, electron, linac	1930
	S. Zarei, F. AbbasiDavani, S. Ahmadiannamini, F. Ghasemi sbu, Tehran, Iran H. Shaker IPM, Tehran, Iran
	An S-band Traveling wave linear accelerator with an RF input peak power level up to 2.5 MW, for accelerating 1 mA beam of electron up to 15 MeV, is under construction in Iran. This article presents design procedure of a prebuncher for this accelerator. One standing-cavity type prebuncher is required for bunching electron beam for this accelerator. The intended prebuncher is driven by a coaxial line at 2 kW and operated at the same frequency of the other parts of the accelerator. The magnetic coupling applied has been applied for power coupling to the prebuncher cavity. The optimum dimensions of the prebuncher were obtained by using 2D and 3D electromagnetic codes in the frequency domain. Prebuncher cavity consists of a copper body and coupling loop feed.

TUPPR051	Development of L-Band Positron Capture Accelerating Structure with Kanthal-coated Collinear Load for SuperKEKB	solenoid, damping, target, positron	1933
	F. Miyahara, Y. Arakida, T. Higo, N. Iida, K. Kakihara, T. Kamitani, S. Matsumoto KEK, Ibaraki, Japan L. Lilje DESY, Hamburg, Germany
	In order to achieve a luminosity of 8x10³⁵ cm^-2 s^-1, the SuperKEKB injector is required to provide both e⁺e⁻ beams higher in intensity by a factor 4-5 than those for KEKB, and with a low emittance of about 20 um. A damping ring is used to fulfill this low emittance requirement for e⁺, but the intensity increase is realized by a larger yield from the conversion target to the damping ring. To this end, the L-band capture system is adopted to increase the transverse and longitudinal acceptance. The capture section consists of a Tungsten conversion target with flux concentrator followed by two L-band 2.4m-long accelerating structures and continuing to the large aperture S-band 2m-long ones. The L-band frequency of 1.3 GHz, 5/11 times S-band one, was adopted to suppress the satellite bunches in the S-band system. This L-band system is surrounded by a solenoid magnet producing 4kG on axis. To compose compact magnet system, the output coupler of the L-band accelerating structure is replaced by the Kanthal coated collinear load section. In this paper, we will discuss the design of the accelerating structure and present the studies of Kanthal layer coated on copper.

TUPPR055	Upgrading the CEBAF Injector with a New Booster, Higher Voltage Gun, and Higher Final Energy	booster, gun, cryomodule, coupling	1945
	R. Kazimi, A. Freyberger, F.E. Hannon, A.S. Hofler, A. Hutton JLAB, Newport News, Virginia, USA
	Funding: Authored by JSA, LLC under U.S. DOE Contract DE-AC05- 06OR23177. The U.S. Govt. retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this for U.S. Govt. purposes. The CEBAF accelerator at Jefferson Lab will be upgraded from 6 GeV to 12 GeV in the next few years. To meet the requirement of the new machine and also to take the opportunity to improve the beam quality, the CEBAF injector will be upgraded with a higher voltage gun, a new booster, and a new accelerating RF module. The CEBAF injector creates and accelerates three beams at different currents simultaneously. The beams are interleaved, each at one third of RF frequency, traveling through the same beam line. The higher voltage gun will lower the space charge effects making it easier to operate at different current with the same setup. The new booster with optimized beam dynamics will complete the bunching process and provides initial acceleration matched to the new gun voltage. Using our latest SRF design, the new booster has significantly lower XY coupling effects that should improve our beam setup and operation for the highly sensitive parity experiments scheduled for the CEBAF’s future. Finally, the new accelerating RF module will roughly double the injector final energy to match the rest of the 12 GeV accelerator. In this paper we will provide more detail about this upgrade.

TUPPR076	The LHeC Project Development Beyond 2012	electron, linac, collider, dipole	1999
	F. Zimmermann, O.S. Brüning CERN, Geneva, Switzerland M. Klein The University of Liverpool, Liverpool, United Kingdom
	The LHeC study group is finalizing a Conceptual Design Report for publication early in 2012. This paper discusses the next steps required for developing a Technical Design Report and highlights the R&D developments, test facilities and implementation studies that need to be addressed over the coming years. Particular emphasize will be given to similarities with other ongoing accelerator and detector studies, and to a discussion of possible international collaboration efforts.

TUPPR084	HOM Damping and Multipacting Analysis of the Quarter-wave Crab Cavity	HOM, damping, simulation, electron	2020
	Q. Wu, S.A. Belomestnykh, I. Ben-Zvi BNL, Upton, Long Island, New York, USA R. Calaga CERN, Geneva, Switzerland
	The Quarter-Wave Crab Cavity design has been analyzed further to accommodate LHC requirements. The goal for the design is to provide strong deflecting voltage to the proton bunches at the IP, while keeping the effective length as short as possible. We will evaluate the Higher Order Mode damping with two magnetic coupling dampers of 90 degrees apart. In this paper, we also show possible multipacting locations which are simulated by 3D code.

WEYB03	High Average Power UV Free Electron Laser Experiments at JLAB	FEL, wiggler, linac, electron	2111
	D. Douglas, S.V. Benson, P. Evtushenko, J.G. Gubeli, C. Hernandez-Garcia, R.A. Legg, G. Neil, T. Powers, M.D. Shinn, C. Tennant, G.P. Williams JLAB, Newport News, Virginia, USA
	Funding: Authored by JSA LLC under US DOE Contract #DE-AC05-06OR23177. The U.S. Gov. retains non-exclusive, paid-up, irrevocable, world-wide license to publish/reproduce this manuscript for U.S. Gov. purposes. Having produced 14 kW of average power at ~2 microns, JLAB has shifted its focus to the ultraviolet portion of the spectrum. This presentation will describe the JLab UV Demo FEL, present specifics of its driver ERL, and discuss the latest experimental results from FEL experiments and machine operations.
	Slides WEYB03 [2.863 MB]

WEOBA03	Beam Tests of a High Pressure Gas-Filled Cavity for a Muon Collider	electron, ion, pick-up, collider	2131
	T.A. Schwarz, M.A. Leonova, A. Moretti, M. Popovic, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, USA M. Chung Handong Global University, Pohang, Republic of Korea B.T. Freemire, P.M. Hanlet, Y. Torun IIT, Chicago, Illinois, USA R.P. Johnson Muons, Inc, Batavia, USA
	Funding: US DOE under contract DE-AC02-07CH11359. One of the greatest challenges in constructing a Muon Collider is cooling the hot muons into a focused beam after their production. Because the beam must be cooled quickly before the muons decay, compact cooling designs require high gradient cavities inside strong magnetic fields. Unfortunately, due to focused field emission, an external magnetic field degrades the performance of the cavity below what is required for a muon collider. High-pressure gas inside the cavity has been proposed to both mitigate this effect, as well as serve as an absorber for transversely cooling the muon beam. A prototype of a high pressure gas-filled cavity is currently being studied at the Muon Test Area at Fermilab. The experimental setup as well as several measurements of the physics and performance of the apparatus while operating in a 400-MeV proton beam will be discussed.
	Slides WEOBA03 [6.912 MB]

WEOAB03	An Update on a Superconducting Photonic Band Gap Structure Resonator Experiment	SRF, HOM, wakefield, niobium	2140
	E.I. Simakov, W.B. Haynes, M.A. Madrid, F.P. Romero, T. Tajima, W.M. Tuzel LANL, Los Alamos, New Mexico, USA C.H. Boulware, T.L. Grimm Niowave, Inc., Lansing, Michigan, USA
	Funding: This work is supported by the U.S. Department of Energy (DOE) Office of Science Early Career Research Program. We present an update on the 2.1 GHz superconducting rf (SRF) photonic band gap (PBG) resonator experiment in Los Alamos. The SRF PBG cell was designed to operate at 2.1 GHz. PBG cells have great potential for outcoupling long-range wakefields in SRF accelerator structures without affecting the fundamental accelerating mode. Using PBG structures in superconducting particle accelerators will allow operation at higher frequencies and moving forward to significantly higher beam luminosities thus leading towards a completely new generation of colliders for high energy physics. However, the technology of fabrication of PBG accelerator cells from niobium has not been well developed to date. Here we report the results of our efforts to fabricate a 2.1 GHz PBG cell and to test it at high gradients in a liquid helium bath at the temperature of 2 Kelvin. The high gradient performance of the cell will be evaluated and the results will be compared to simulations with the CST Microwave Studio.
	Slides WEOAB03 [2.061 MB]

WEOBB02	Refraction Contrast Imaging via Laser-Compton X-Ray Using Optical Storage Cavity	laser, electron, photon, linac	2146
	K. Sakaue, T. Aoki, M. Washio RISE, Tokyo, Japan M.K. Fukuda, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	We have been developing a pulsed-laser storage technique in a super-cavity for a 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 a multi-pulse x-rays through the laser-Compton scattering. Then, we performed a X-ray imaging via laser-Compton X-ray. The images have edge enhancement by refraction contrast because the X-ray source spot size was small enough. This is one of the evidences that laser-Compton X-ray is high quality. Our laser-Compton experimental setup, the results of X-ray imaging and future prospective will be presented at the conference.
	Slides WEOBB02 [4.393 MB]

WEEPPB004	Status of the APEX Project at LBNL	gun, cathode, laser, electron	2173
	F. Sannibale, B.J. Bailey, K.M. Baptiste, J.M. Byrd, C.W. Cork, J.N. Corlett, S. De Santis, L.R. Doolittle, J.A. Doyle, P. Emma, J. Feng, D. Filippetto, G. Huang, H. Huang, T.D. Kramasz, S. Kwiatkowski, W.E. Norum, H.A. Padmore, C. F. Papadopoulos, G.C. Pappas, G.J. Portmann, J. Qiang, D.G. Quintas, J.W. Staples, T. Vecchione, M. Venturini, M. Vinco, W. Wan, R.P. Wells, M.S. Zolotorev, F.A. Zucca LBNL, Berkeley, California, USA M. J. Messerly, M.A. Prantil LLNL, Livermore, California, USA C.M. Pogue NPS, Monterey, California, USA
	Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231. The Advanced Photo-injector Experiment (APEX) at the Lawrence Berkeley National Laboratory is focused on the development of a high-brightness high-repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept gun, utilizing a normal conducting 186 MHz RF cavity operating in cw mode in conjunction with high quantum efficiency photocathodes capable of delivering the required repetition rates with available laser technology. The APEX activities are staged in 3 main phases. In Phases 0 and I, the gun will be tested at its nominal energy of 750 keV and several different photocathodes are tested at full repetition rate. In Phase II, a pulsed linac will be added for accelerating the beam at several tens of MeV to reduce space charge effects and measure the high-brightness performance of the gun when integrated in an injector scheme. At Phase II energies, the radiation shielding configuration of APEX limits the repetition rate to a maximum of several Hz. Phase 0 is under commissioning, Phase I under installation, and initial activities for Phase II are underway. This paper presents an update on the status of these activities.

WEEPPB008	HOM Coupler Optimisation for the Superconducting RF Cavities in ESS	HOM, neutron, target, damping	2182
	R. Ainsworth Royal Holloway, University of London, Surrey, United Kingdom R. Calaga CERN, Geneva, Switzerland S. Molloy ESS, Lund, Sweden
	The European Spallation Source (ESS) will be the world’s most powerful next generation neutron source. It consists of a linear accelerator, target, and instruments for neutron experiments. The linac is designed to accelerate protons to a final energy of 2.5 GeV , with an average design beam power of 5 MW, for collision with a target used to produce a high neutron flux. A section of the linac will contain Superconducting RF (SCRF) cavities designed to resonate at 704 MHz. Dangerous beam induced modes in these cavities may make the beam unstable and increase the cryogenic load and so couplers are usually installed to provide damping. Previous studies have shown potential designs are susceptible to multipacting, a resonant process which can absorb RF power and lead to heating effects. This paper will show how a coupler suffering from multipacting has been redesigned to limit this effect. Optimisation of the RF damping is also discussed.

WEEPPB010	RF Modeling Using Parallel Codes ACE3P for the 400-MHz Parallel-Bar/Ridged-Waveguide Compact Crab Cavity for the LHC HiLumi Upgrade	damping, HOM, impedance, dipole	2185
	Z. Li, L. Ge SLAC, Menlo Park, California, USA J.R. Delayen, S.D. Silva ODU, Norfolk, Virginia, USA
	Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515. Schemes utilizing crab cavities to achieve head-on beam-beam collisions were proposed for the LHC HiLumi upgrade. These crabbing schemes require that the crab cavities be compact in order to fit into the tight spacing available in the existing LHC beamlines at the location where the crab cavities will be installed. Under the support of US LARP program, Old Dominion University and SLAC have joint efforts to develop a 400-MHz compact superconducting crab cavity to meet the HiLumi upgrade requirements. In this paper, we will present the RF modeling and analysis of a parallel-bar/ridged-waveguide shaped 400-MHz compact cavity design that can be used for both the horizontal and vertical crabbing schemes. We will also present schemes for HOM damping and multipacting analysis for such a design.

WEEPPB015	Temperature Dependence of the Superheating Field: DC and RF Critical Fields	niobium, electron, superconductivity, SRF	2197
	N.R.A. Valles, M. Liepe CLASSE, Ithaca, New York, USA
	The superheating field is a metastable state at which the Meissner state persists at fields higher than would be predicted from steady-state energy considerations. Previous work demonstrated that a phenomenological approach based on the RF superheating field scaling near the critical temperature is also consistent with low temperature results. This work expands upon the RF results by measuring the DC superheating field, and comparing it to RF results and theoretical predictions.

WEPPC002	Impact of Trapped Flux and Thermal Gradients on the SRF Cavity Quality Factor	niobium, superconducting-cavity, SRF, controls	2203
	O. Kugeler, J. Knobloch, J.M. Vogt HZB, Berlin, Germany S. Aull CERN, Geneva, Switzerland
	The obtained Q0 value of a superconducting niobium cavity is known to depend on various factors like the RRR of the Niobium material, crystallinity, chemical treatment history, the high-pressure rinsing process, or effectiveness of the magnetic shielding. We have observed that spatial thermal gradients over the cavity length during cool-down appear to contribute to a degradation of Q0. Measurements were performed in the Horizontal Bi-Cavity Test Facility (HoBiCaT) at HZB on TESLA type cavities as well as on disc- and rod-shaped niobium samples equipped with thermal, electrical and magnetic diagnostics. Possible explanations for the effect are discussed.

WEPPC003	Component Qualification and Final Assembly of the S-DALINAC Injector Upgrade Module	linac, SRF, niobium, shielding	2206
	J. Conrad, R. Eichhorn, T. Kürzeder, A. Richter, S.T. Sievers TU Darmstadt, Darmstadt, Germany
	Funding: This work is supported by the DFG through SFB 634. The injector of the S-DALINAC delivers currently electron beams of up to 10 MeV with a current of up to 60 μA. With the new cryostat-module an increase of both parameters, energies ranging to 14 MeV and currents up to 150 μA, are expected. For acceleration, the module houses two 20 cell elliptical niobium cavities which are used at a frequency of 3 GHz in liquid helium at 2 K. The RF power is delivered to the cavities through the different temperature stages by a WR-284 transition line which is connected to the resonator by a new waveguide-to-coax power coupler (being one of the major changes compared to the design of the existing module). We review on the design of the module and present the results of the first cool-down. Also, a report on additional new design features, e.g. piezo actuators for tuning at 2 K, and the production of the cavities will be given.

WEPPC004	PLM-Based Quality Assurance in the Series Production of the Superconducting Cavities for the European XFEL	background	2209
	L. Hagge, J.A. Dammann, S. Eucker, J. Iversen, J. Kreutzkamp, W. Singer DESY, Hamburg, Germany
	This presentation describes the acceptance procedure in the series production of the superconducting cavities for the European XFEL. The cavities are produced by two manufacturers. To ensure they satisfy their performance requirements, the cavities have to pass more than 50 quality inspections, which are combined into four acceptance levels. Part of the inspections are done by the manufacturers, the remaining tests are conducted in a test facility at DESY. The inspections are recorded and processed based on DESY's Product Lifecycle Management (PLM) system, aka DESY EDMS. The DESY EDMS tracks all the individual cavities, keeps their entire production history, and associates all certificates and inspection results with the appropriate parts. The two manufacturers are integrated in the solution and can automatically and promptly upload inspections results to the DESY EDMS. The solution enables DESY to monitor the production progress and to ensure production quality.

WEPPC005	Parts Management during Fabrication at the European XFEL	controls, undulator, cryomodule, niobium	2212
	L. Hagge, J.A. Dammann, S. Eucker, A. Herz, J. Kreutzkamp, D. Käfer, D. Szepielak, N. Welle DESY, Hamburg, Germany
	This presentation describes policies and methods for parts management during fabrication at the European XFEL. The objective is to provide procedures for reliably gathering, recording, processing and archiving the complete mandatory fabrication information. The solution is a foundation for conducting Quality Assurance and Quality Control (QA/QC), as it ensures that acceptance tests are recorded, signed-off and followed-up in a reliable and orderly way. It achieves compliance with legal regulations in certain areas. One example is the pressurized equipment directive (PED), which for certain (parts of) equipment requires that the complete fabrication and usage history is tracked throughout the entire lifespan of the XFEL facility. In addition, the solution provides a basis for building the necessary documentation for later installation, operation and maintenance activities. The solution is established in the series production of several accelerator components. It uses DESY’s Engineering Data Management System as central collaboration and documentation platform.

WEPPC006	CW and LP Operation Test of XFEL-Like Cryomodule	HOM, cryomodule, cryogenics, feedback	2215
	J.K. Sekutowicz, V. Ayvazyan, M. Ebert, J. Eschke, A. Gössel, D. Kostin, I.M. Kudla, W. Merz, F. Mittag, R. Onken DESY, Hamburg, Germany W. Cichalewski, W. Jałmużna, K.P. Przygoda TUL-DMCS, Łódź, Poland K. Czuba, L. Zembala Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland J. Szewiński The Andrzej Soltan Institute for Nuclear Studies, Centre Świerk, Świerk/Otwock, Poland
	A continuous improvement in the performance of superconducting TESLA cavities will make possible, from the cryogenic point of view, operation of the XFEL linac in continuous wave (cw) mode at gradients up to 7.5 MV/m and in long pulse (lp) mode up to nominal gradient of 23.4 MV/m. Each of these new operation modes will offer an additional flexibility in time structure of the photon beam, and therefore will allow for more experiments and in some cases less demanding and less expensive equipment. In this contribution we discuss results of the first RF test of these new types of operation with a XFEL-like cryomodule.

WEPPC007	Image Processing for Characterization of Surfaces of Superconducting RF Cavities	superconductivity, LabView, linear-collider, collider	2218
	M. Wenskat, S. Aderhold, E. Elsen, S. Karstensen, F. Schlander, L. Steder DESY, Hamburg, Germany
	Funding: ILC HiGrade Optical inspection of finished Nb superconducting RF cavities has worldwide been established as an important tool for identification of field limiting surface features. Single defects in a single cell of a 9-cell cavity may severely constrain the maximum gradient while the micro-structure in the vicinity of a welding seam could affect the quench behavior. DESY has automated the imaging of critical cavity surface areas, in particular those of high magnetic field. With resolution of ~10 μm2 the information volume is large and the systematic examination becomes a necessity. The development of image processing algorithms has been started with two goals: automatic characterization of cavity surface properties and defect detection. The former results aid the quality assessment of cavities after manufacture; the latter serves to push the gradient performance. The status and prospects of the image processing for the European XFEL and ILC will be presented.

WEPPC008	FNAL Project X Conical Half-Wave Resonator Design	simulation, cryomodule, resonance, proton	2221
	E.N. Zaplatin FZJ, Jülich, Germany A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA
	Funding: This work is supported by the DOE SBIR Program, contract # DE-SC0006302. A high-intensity proton accelerator complex proposed at Fermi National Accelerator Laboratory (Project X) should provide beam for a variety of physics projects. The superconducting resonators of different types will be used as accelerating structures. Here we describe the design of conical Half-Wave Resonator that is considered as an option for a first accelerating cavity for β=v/c=0.11 with the resonance frequency 162.5 MHz. A careful study of the fields in the cavity has been carried out in order to optimize the electromagnetic parameters of the structure (peak fields, quality factor, dissipation power). An intensive investigations were provided of the liquid helium vessel design to minimize cavity frequency shifts from the external loads. Different tuning schemes have been studied to secure a frequency tuning range to cope with fabrication tolerances. The paper reports results of numerical simulations of the cavity shape optimization and structural analyses. The detailed developments of the structure using numerical coupled analyses allowed to minimize the level of expected microphonics in cavity.

WEPPC009	Status of the European XFEL 3.9 GHz system	status, linac, diagnostics, HOM	2224
	P. Pierini, A. Bosotti, P. Michelato, L. Monaco, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy E.R. Harms Fermilab, Batavia, USA C. Pagani UniversitÃ degli Studi di Milano & INFN, Segrate, Italy E. Vogel DESY, Hamburg, Germany
	The injector of the European XFEL will use a third harmonic RF system at 3.9 GHz to flatten the RF curvature after the first accelerating module before the first bunch compression stage. This paper presents qualification tests of the prototype cavities and the status of the activities for the realization of the third harmonic section of the European XFEL towards its commissioning due in 2014.

WEPPC011	Vertical Test Results for ERL 9-cell Cavities for Compact ERL Project	linac, cryomodule, radiation, HOM	2227
	K. Umemori, T. Furuya, H. Sakai, M. Satoh, K. Shinoe KEK, Ibaraki, Japan E. Cenni Sokendai, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	The Compact ERL project, which is a test facility of ERL, is ongoing in Japan. At the first step of this project, main linac cavities accelerate electron beams by 30 MV. Two 9-cell cavities were fabricated for main linac cryomodule, under High Pressure Gas Safety Code in Japan. A series of surface treatments, such as annealing, pre-tuning, electro-polishing (EP), degreasing, high pressure rinsing by ultra-pure water, cavity assembly and baking, were applied for the cavities. For the final EP, current density was selected to be relatively low. Vertical tests were performed for both cavities. Their field successfully reached to 25 MV/m, without any field limitation. The Q-values were more than 1x10¹⁰, even at 20 MV/m. Field emission on-sets were to be 14 and 22 MV/m, for each cavities. Both cavities satisfied requirements for ERL main linac cavity. Details of vertical tests, with X-ray and temperature mapping data, are shown, in this paper. These cavities will be mounted with titanium He jackets, assembled and installed into a cryomodule.

WEPPC012	High Power Tests of CW Input Couplers for cERL Injector Cryomodule	cryomodule, vacuum, linac, impedance	2230
	E. Kako, S. Noguchi, T. Shishido, K. Watanabe, Y. Yamamoto KEK, Ibaraki, Japan
	High power tests of a pair of the prototype input couplers were performed by using a newly developed 300 kW CW klystron. The input couplers were successfully processed up to 100 kW in a pulsed operation with a duty of 10% and 50 kW in a CW operation for 30 minutes. The conditioning was limited by excessive heating at bellows of an inner conductor at a coaxial line locating between a coaxial RF window and a doorknob-type transition. Improvement of a sufficient cooling at the inner conductor is necessary to achieve the required input RF power of 170 kW in a CW operation. Six input couplers to be installed in the injector cryomodule for the cERL project were completed, and they are under preparation for conditioning at a high power test stand.

WEPPC013	Progress of High Gradient Performance in STF 9-cell Cavities at KEK	accelerating-gradient, status, laser, HOM	2233
	Y. Yamamoto, H. Hayano, E. Kako, S. Noguchi, T. Shishido, K. Watanabe KEK, Ibaraki, Japan
	Vertical tests for ILC have been carried out since 2008 at KEK-STF. Measured cavities are from MHI#5 to MHI#22 (not yet for MHI#18-#22 at the end of November 2011), and MHI#12, #13 and #17 reached the ILC specification of 0.8x10¹⁰ at 35MV/m. The MHI cavity was added into the “qualified vendor” for the cavity yield. These three cavities (#12, #13 and #17) had no defect on every EBW seam of equator, iris and beampipe. On the other hand, the other cavities had a few or several defects on EBW seam. Especially, defect on the EBW seam of the equator is the worst case, and cavity performance is limited “certainly”. MHI#10, #15 and #16 cavities were limited by this kind of defect. As for iris region, MHI#14 had large defect at the iris between cell #8 and #9, and the performance was limited by the heavy field emission with “explosive event”. However, after the locally mechanical grind for this defect, the cavity performance was drastically improved with no field emission at 37MV/m. In this paper, the recent progress of the cavity performance at KEK-STF will be reported with the “detailed” defect analysis.

WEPPC014	Construction and Beam Operation of Capture Cryomodule for Quantum Beam Experiments at KEK-STF	cryomodule, controls, radiation, status	2236
	Y. Yamamoto KEK, Ibaraki, Japan
	Construction of capture cryomodule for Quantum Beam Project has started since September, and will be finished by the end of December in 2011 at KEK-STF. Two MHI cavities (MHI-12, -13), which reached ILC specification (0.8x10¹⁰ at 35MV/m) at the vertical test, were installed into a short cryomodule with improved input couplers. Slide-Jack tuner was attached at different position (center or end of helium jacket) for each cavity same as S1-Global. From January 2012, this cryomodule will be cooled down to 2K, and the high power test will be started including check of the cavity/coupler/tuner performance, LFD measurement, LFD compensation by Piezo, dynamic loss measurement and so on. From March, the beam operation with the beam current of 10mA and the maximum beam energy of 40MeV, will be started to generate x-rays by collision between electron beam and laser. At this stage, two cavities will be operated at the lower gradient of 15-20MV/m, and the stable operation is crucial. In this report, the test results of various performances at the Quantum Beam Project will be presented in detail.

WEPPC015	Construction of Injector Cryomodule for cERL at KEK	cryomodule, HOM, pick-up, linac	2239
	E. Kako, S. Noguchi, T. Shishido, K. Watanabe, Y. Yamamoto KEK, Ibaraki, Japan
	The cERL injector cryomodule includes three 2-cell cavities, and each cavity has 2 input couplers and 5 HOM couplers. Three 2-cell cavities for cERL has already completed. Vertical test of the three cavities has been going on. The first cavity have achieved Eacc of 30 MV/m. Vertical tests will be carried out twice in each cavity, till the end of December, 2011. Six cw input couplers for cERL has already completed. RF processing at the high-power test stand with a cw 300kW-klystron will be carried out in Jan.-Feb., 2012. After the cavities were covered with a He jacket, assembly of the cERL injector cryomodule will be carried out in March-April, 2012. The first cool-down of the cryomodule is scheduled in June 2012.

WEPPC018	Design of a Spoke Cavity for RIKEN RI-beam Factory	vacuum, ion, simulation, heavy-ion	2245
	L. Lu RIKEN, Saitama, Japan O. Kamigaito, N. Sakamoto, K. Suda, K. Yamada RIKEN Nishina Center, Wako, Japan
	Designs of a CW superconducting rebuncher tri-spoke cavity for uranium beams with β = 0.303 has been studied. The estimated peak voltage is rather high as 3 mega-voltages (MV). The resonator frequency was chose as 219MHz which is 12 times of the foundational frequency. The buncher would be settled in a location between two booster cyclotrons (RRC: K = 540MeV, fRC: K = 570 MeV). In this cavity design, a flat E field distribution on beam axis was designed based on the Microwave Studio (MWS) simulations. The cavity parameters, detail designs and some simulated results will be reported in this paper.

WEPPC021	Development of Superconducting Radio Frequency Cavities at SINAP	niobium, superconducting-cavity, electron, HOM	2248
	J.F. Liu, H.T. Hou, C.W. Lu, C. Luo, Z.Y. Ma, D.Q. Mao, J. Shi, Zh.G. Zhang, S.J. Zhao, X. Zheng SINAP, Shanghai, People's Republic of China Z.Q. Feng, Z. Li, J.F. Liu, Y.L. Wei, K. Xu, Y.B. Zhao Shanghai KEY Laboratory of Cryogenics & Superconducting RF Technology, Shanghai, People's Republic of China H. Yu Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
	This paper presents the development of superconducting radio frequency cavities at Shanghai Institute of Applied Physics (SINAP) mainly focused on the 500MHz band. Firstly, Two KEKB type 500MHz single cell niobium cavities have been fabricated and one of them has been vertical tested successfully in 2010. The highest accelerating gradient of the fabricated cavity higher than 10MV/m was obtained while the quality factor was better than 4·10⁸ at 4.2K. Secondly, a new type of 500MHz single cell cavity has been designed which adopts the fluted beam pipe for higher order modes propagation and a coaxial type high power input coupler. Thirdly, a 500MHz 5-cell superconducting cavity with large aperture, enlarged beam pipe for HOM propagation and high r/Q value has been optimized which can be a candidate cavity for high current FEL and ERL.

WEPPC022	Elliptical SRF Cavity Design for PEFP Extension	linac, SRF, coupling, proton	2251
	H.S. Kim, Y.-S. Cho, J.-H. Jang, H.-J. Kwon KAERI, Daejon, Republic of Korea
	Funding: * This work is supported by the Ministry of Education, Science and Technology of the Korean Government. To increase the beam energy up to 1 GeV by extending a PEFP 100-MeV proton linac, a study on the superconducting RF linac is underway. SRF technology is chosen due to its operational flexibility and lower beam loss, as well as its high accelerating performance and low operating cost. Preliminary study on the beam dynamics shows that two types of cavity with geometrical beta of 0.50 and 0.74 can cover the entire energy range from 100 MeV to 1 GeV. Assuming the achievable peak surface electric field to be 30 MV/m and 35 MV/m for medium and high beta cavity, respectively, we designed the six-cell elliptical cavities by optimizing the cavity parameters such as peak field ratio, inter-cell coupling and r/Q through the geometrical parameter sweep. The details of the SRF cavity design for PEFP extension will be presented.

WEPPC024	Preliminary Test of Superconducting RF Cavities for PLS-II	SRF, cryomodule, vacuum, cryogenics	2257
	Y.U. Sohn, M.-H. Chun, J.Y. Huang, Y.D. Joo, H.-S. Kang, H.-G. Kim, S.H. Nam, C.D. Park, H.J. Park, I.S. Park, I.H. Yu PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: This project is supported by the Korea Ministry of Science and Technology. The main part of the Installation for the PLS-II upgrade was finished in June and is on the way to user operation through elaborate commissioning. Up to now, the achievement is 150 mA beam current at 3 GeV with multi-bunch mode with 5 normal conducting cavities which served in the PLS before. After installation of 2 SRF cavities in the summer of 2012, the PLS-II will have 300 mA beam current with 20 IDs by 2 superconducting RF cavities until July, 2014. Finally, one more superconducting cavity will be added in August, 2014, and beam current will rise to 400 mA. The two SRF cavities are under test and conditioning. The two main subsystems, SRF cavities and ceramic windows were tested independently to confirm their performance. Each cavity recorded its accelerating voltage as 3.27 MV and 3.24 MV at 4.2K, respectively. Two RF windows also passed their specification, 300 kW CW traveling wave and 150 kW CW standing wave. The preliminary tests of SRF cryomodules are reported in the presentation.

WEPPC027	A Quarter Wave Design for Crab Crossing in the LHC	HOM, acceleration, high-voltage, higher-order-mode	2260
	R. Calaga CERN, Geneva, Switzerland S.A. Belomestnykh, I. Ben-Zvi, Q. Wu BNL, Upton, Long Island, New York, USA
	Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP). The aperture constraints of the LHC interaction region and the alternating crossing schemes at two collision points calls for a superconducting deflecting cavity with very compact dimensions at low frequencies for the purpose of crab crossing. A new concept of using a superconducting 1/4-wave design, ideally suited to address the LHC constraints at 400 MHz, is proposed. The optimized RF cavity design and associated advantages of using a 1/4 wave resonator are presented. Aspects related to higher order mode damping, multipacting and frequency tuning are also addressed.

WEPPC028	Slim Elliptical Cavity at 800 MHz for Local Crab Crossing	coupling, damping, impedance, HOM	2263
	L. Ficcadenti, J. Tückmantel CERN, Geneva, Switzerland
	A slim highly eccentric elliptical Crab cavity with vertical deflection at 800 MHz, compatible to beam line distances everywhere in the LHC ring, was designed. It is a good fall-back solution in case of problems with new compact 400 MHz designs. Simulated RF characteristics of the delfecting mode, HOM spectra and damping, tuning and multipacting effects are presented. First the most simple HOM coupling system was investigated. The rejection of the working mode was not sufficient and a notch filter was added. Results of both cases will be presented.

WEPPC029	Design and Development of an Octopus Thermometric System for the 704 MHz Single-cell SPL Cavity at CERN	LabView, SRF, factory, proton	2266
	K.C. Liao, L. Arnaudon, O. Brunner, E. Ciapala, D.C. Glenat, W. Weingarten CERN, Geneva, Switzerland
	The octopus thermometric system is designed for the 704 MHz superconducting proton linac (SPL) cavity to detect hot spots and X-rays caused by normal conducting defects and the impact of emission electrons. This system features an octopus body and tentacle structure for good contact with the cavity and easy assembly, a multiplexing circuit with integrated microprocessor for efficient readout and a high density temperature sensor arrangement in order to complete a high resolution temperature and X-ray map. The first prototype is being manufactured and investigations are undergoing for further development.
	Poster WEPPC029 [1.715 MB]

WEPPC030	Second Sound Measurement Using SMD Resistors to Simulate Quench Locations on the 704 MHz Single-cell Cavity at CERN	simulation, cryogenics, linac, quadrupole	2269
	K.C. Liao, O. Brunner, E. Ciapala, T. Junginger, W. Weingarten CERN, Geneva, Switzerland
	Oscillating superleak transducers (OSTs) containing a flexible porous membrane are widely used to detect the so-called second sound temperature wave when a quench event occurs in a superconducting RF cavity. In principle, from the measured speed of this wave and the travel time between the quench event and several OSTs, the location of the quench sites can be derived by triangulation. Second sound behavior has been simulated though different surface mount (SMD) resistors setups on a Superconducting Proton Linac (SPL) test cavity, to help understand the underlying physics and improve quench localisation. Experiments are described that have been conducted to search for explanation of heat transfer mechanism during cavity quench that causes contradictory triangulation results.
	Poster WEPPC030 [1.473 MB]

WEPPC031	Completed Assembly of the Daresbury International ERL Cryomodule and its Implementation on ALICE	cryomodule, HOM, cryogenics, controls	2272
	P.A. McIntosh, M.A. Cordwell, P.A. Corlett, P. Davies, E. Frangleton, P. Goudket, K.J. Middleman, S.M. Pattalwar, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S.A. Belomestnykh BNL, Upton, Long Island, New York, USA A. Büchner, F.G. Gabriel, P. Michel HZDR, Dresden, Germany J.N. Corlett, D. Li, S.M. Lidia LBNL, Berkeley, California, USA G.H. Hoffstaetter, M. Liepe, H. Padamsee, P. Quigley, J. Sears, V.D. Shemelin, V. Veshcherevich CLASSE, Ithaca, New York, USA T.J. Jones, J. Strachan STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom R.E. Laxdal TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada D. Proch, J.K. Sekutowicz DESY, Hamburg, Germany T.I. Smith Stanford University, Stanford, California, USA
	The completion of an optimised SRF cryomodule for application on ERL accelerators has now culminated with the successful assembly of an integrated cryomodule, following an intensive 5 years of development evolution. The cryomodule, which incorporates 2 x 7-cell 1.3 GHz accelerating structures, 3 separate layers of magnetic shielding, fully adjustable & high power input couplers and fast piezo tuners, has been installed on the ALICE ERL facility at Daresbury Laboratory. It is intended that this will permit operational optimisation for maximised efficiency demonstration, through increased Qext adjustment whilst retaining both effective energy recovery and IR-FEL lasing. The collaborative design processes employed in completing this new cryomodule development are explained, along with the assembly and implementation procedures used to facilitate its successful installation on the ALICE ERL facility.

WEPPC032	Analysis of the Four Rod Crab Cavity for HL-LHC	multipactoring, simulation, niobium, luminosity	2275
	B.D.S. Hall, P.K. Ambattu, G. Burt, D. Doherty, C. Lingwood Cockcroft Institute, Lancaster University, Lancaster, United Kingdom P. Goudket STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The Hi-Lumi Upgrade to the LHC will utilise crab cavities to increase the peak luminosity and provide luminosity levelling at the increased crossing angle. A transversely compact design is required to fit within the limited space between opposing beamlines. In this paper a four rod TEM deflecting cavity (4RCC) is shown to be suitable for LHC. The variation of the deflecting voltage with radial offset has been minimised by careful design and an aluminium prototype has been constructed and beadpull measurements are compared to simulations. Multipacting simulations have been performed on the cavity geometry and it is predicted that the growth rate is less than unity for a clean surface. Pressure variations in the LHe can result in deformation of the complex shape which will alter the resonant frequency. Mechanical simulations have also been performed to assess the sensitivity of the frequency to pressure. In order to reduce the impact of these cavities on the LHC beam low impedance is required for the HOMs as well as the fundamental monopole mode. The couplers for the 4RCC cavity have been optimised to provide effective damping of these modes while rejecting the operating mode.

WEPPC035	Design and Construction of a High-Power RF Coupler for PXIE	cryomodule, vacuum, linac, simulation	2284
	M.P. Kelly, Z.A. Conway, M. Kedzie, S.V. Kutsaev, P.N. Ostroumov ANL, Argonne, USA S. Nagaitsev Fermilab, Batavia, USA
	A power coupler has been designed and built at Argonne National Laboratory for use with the Project X Injector Experiment (PXIE) 162.5 MHz superconducting (SC) half-wave cavities. The 50 Ω coaxial capacitive coupler will be required to operate CW with up to 10 kW of forward power under any condition for the reflected power. A key feature is a moveable copper plated stainless steel bellows which will permit up to 3 cm of axial stroke and adjustment of Qext by roughly one order of magnitude in the range of 10^-5 to 10^-6. The mechanical and vacuum design will include two ceramic windows, one operating at room temperature and another at 70 Kelvin. The two window design allows the portion of the coupler assembled to the SC cavity in the clean room to be compact and readily cleanable. We present other design features including thermal intercepts to provide a large margin for RF heating and a mechanical guide assembly to operate cold and under vacuum with high reliability.

WEPPC036	Electromagnetic Design of 15 kW CW RF Input Coupler	simulation, cryomodule, linac, vacuum	2286
	S.V. Kutsaev, M.P. Kelly, P.N. Ostroumov ANL, Argonne, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. A new power coupler is under development at Argonne National Laboratory for a cw 40 MeV proton/deuteron linac for the SARAF project in Israel. This linac requires one 15 kW RF input power per superconducting cavity. Two different cavity options are still under consideration: 10⁹ MHz quarter-waves and 176 MHz half-waves. A coaxial capacitive input coupler has been designed and analyzed for these purposes. This paper presents the results of 3D electromagnetic simulations of this coupler together with the cavities mentioned above. An analysis of multipacting in the couplers is also presented.

WEPPC037	A Ring-shaped Center Conductor Geometry for a Half-wave Resonator	quadrupole, impedance, linac, ion	2289
	B. Mustapha, Z.A. Conway, P.N. Ostroumov ANL, Argonne, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract DE-AC02-06CH11357. Half-wave resonators (HWR) are used and being proposed for the acceleration of high-intensity proton and heavy-ion beams in the 0.1 < β < 0.5 velocity range. The highest performing half-wave resonator geometries use a center conductor with a race-track shaped cross section in the high-electric field region; a feature shared with spoke cavities which are also being proposed for the same velocity regime. We here propose a ring-shaped center conductor instead of the race-track shape. Preliminary studies show that the ring geometry has a similar peak surface electric field as the race-track one, but has several other advantages. In particular, the ring-shaped geometry has: a lower peak surface magnetic field, a much higher Shunt impedance for the same peak fields, and no quadrupole electric field asymmetry which has been observed in the race-track geometry. In a solenoid-based symmetric focusing, the quadrupole component may lead to unnecessary emittance growth which is not acceptable in high-intensity ion linacs. We will present a detailed comparison and a discussion of the two geometries.

WEPPC038	Status of the Short-Pulse X-ray Project at the Advanced Photon Source	LLRF, cryomodule, HOM, simulation	2292
	A. Nassiri, N.D. Arnold, T.G. Berenc, M. Borland, B. Brajuskovic, D.J. Bromberek, J. Carwardine, G. Decker, L. Emery, J.D. Fuerst, A.E. Grelick, D. Horan, J. Kaluzny, F. Lenkszus, R.M. Lill, J. Liu, H. Ma, V. Sajaev, T.L. Smith, B.K. Stillwell, G.J. Waldschmidt, G. Wu, B.X. Yang, Y. Yang, A. Zholents ANL, Argonne, USA J.M. Byrd, L.R. Doolittle, G. Huang LBNL, Berkeley, California, USA G. Cheng, G. Ciovati, P. Dhakal, G.V. Eremeev, J.J. Feingold, R.L. Geng, J. Henry, P. Kneisel, K. Macha, J.D. Mammosser, J. Matalevich, A.D. Palczewski, R.A. Rimmer, H. Wang, K.M. Wilson, M. Wiseman JLAB, Newport News, Virginia, USA Z. Li, L. Xiao SLAC, Menlo Park, California, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source Upgrade (APS-U) Project at Argonne will include generation of short-pulse x-rays based on Zholents’* deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. In collaboration with Jefferson Laboratory, we are prototyping and testing a number of single-cell deflecting cavities and associated auxiliary systems with promising initial results. In collaboration with Lawrence Berkeley National Laboratory, we are working to develop state-of-the-art timing, synchronization, and differential rf phase stability systems that are required for SPX. Collaboration with Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi-cavity geometries with lower- and higher-order modes waveguide dampers using ACE3P. This contribution provides the current R&D status of the SPX project. * A. Zholents et al., NIM A 425, 385 (1999).

WEPPC039	Development of a Half-Wave Resonator for Project X	linac, SRF, cryomodule, ion	2295
	P.N. Ostroumov, Z.A. Conway, R.L. Fischer, S.M. Gerbick, M. Kedzie, M.P. Kelly, B. Mustapha ANL, Argonne, USA I.V. Gonin, S. Nagaitsev Fermilab, Batavia, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics and Nuclear Physics, under Contract DE-AC02-76CH03000 and DE-AC02-06CH11357. We have developed an optimized electromagnetic and mechanical design of a 162.5 MHz half-wave resonator (HWR) suitable for acceleration of high-intensity proton or H-minus beams in the energy range from 2 MeV to 10 MeV. The cavity design is based on recent advances in SRF technology for TEM-class structures being developed at ANL. Highly optimized EM parameters were achieved by adjusting the shapes of both inner and outer conductors. This new design will be processed with a new HWR horizontal electropolishing system after all mechanical work on the cavity including the welding of the helium jacket is complete. The prototype HWR is being fabricated by domestic vendors under ANL’s supervision.

WEPPC040	Evaluation of VATSEAL Technology to Seal Waveguide Serving High-field Superconducting RF Cavities	vacuum, SRF, impedance, radio-frequency	2298
	B.K. Stillwell, J.D. Fuerst, J. Liu, G.J. Waldschmidt, G. Wu ANL, Argonne, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. A waveguide flange seal serving a high-field, superconducting, radio-frequency (SRF) cavity ideally possesses several characteristics. Seals must generally be ultrahigh-vacuum leak tight. Seals must also bridge the inner surfaces of connecting flanges for optimum transmission and minimal heating due to trapped modes. In addition, if seal contact areas are minimized, flange seals may serve as convenient thermal impedances. Finally, seals must be easily cleanable and not be prone to generate particulate matter during assembly and disassembly. A unique sealing technology known as VATSEAL may neatly address all of the above requirements. In this paper, we describe our evaluation of VATSEAL technology for use in SRF cavity assemblies.

WEPPC041	Tests of SRF Deflecting Cavities at 2K	SRF, vacuum, cryogenics, photon	2300
	J.D. Fuerst, D. Horan, J. Kaluzny, A. Nassiri, T.L. Smith, G. Wu ANL, Argonne, USA
	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) at Argonne National Laboratory (ANL) is developing 2.8-GHz deflecting-mode superconducting rf cavities in collaboration with Jefferson Lab as part of a major facility upgrade. On-site testing of these cavities requires a new cryostat capable of operation at 2.0 K or less. The APS has leveraged facilities and expertise within ANL’s Physics Division to upgrade an existing test stand for continuous operation at temperatures as low as 1.7 K. A new cryogenic feedbox was fabricated and mated to an existing liquid helium “bucket” dewar with 0.6-m inside diameter and 1-m working depth. The configuration allows continuous sub-λ operation using warm vacuum pumping and helium make-up from the Physics Division’s existing cryoplant at heat loads up to 50 W dynamic, plus 15 W measured static load at 2.0 K. A 2.8-GHz TWT-based rf station has been installed and commissioned, providing up to 275 W of rf power. We describe the cryogenic and rf performance of the system and provide examples of cavity test results.

WEPPC043	Transverse Kick Analysis of SSR1 Due to Possible Geometrical Variations in Fabrication	simulation, linac, alignment, solenoid	2306
	M.H. Awida, P. Berrutti, I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev Fermilab, Batavia, USA
	Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE Due to fabrication tolerance, it is expected that some geometrical variations could happen to the SSR1 cavities of Project X, like small shifts in the transverse direction of the beam pipe or the spoke. It is necessary to evaluate the resultant transverse kick due to these geometrical variations, in order to make sure that they are within the limits of the correctors in the solenoids. In this paper, we report the transverse kick values for various fabrications errors and the sensitivity of the beam to these errors.

WEPPC044	Multipole Effects Study for Project X Front End Cavities	multipole, quadrupole, linac, focusing	2309
	P. Berrutti, M.H. Awida, I.V. Gonin, J.-F. Ostiguy, N. Solyak, V.P. Yakovlev Fermilab, Batavia, USA
	Effects of RF field asymmetry along with multipoles have been studied in Project X front end cavities. One family of half wave resonators operating at 162.5 and two of spoke resonators operating at 325 MHz have been analysed. HWR and spoke resonators unlike elliptical cavities, do not have axial symmetry, hence a quadrupole perturbation to the beam is present. The purpose of this paper is to explain the approach and the calculation method used to understand and overcome the drawbacks due to the RF field asymmetry.

WEPPC045	Optimization of the Geometric Beta for the SSR2 Cavities of the Project X	linac, cryomodule, factory, proton	2312
	P. Berrutti, M.H. Awida, I.V. Gonin, N. Solyak, A. Vostrikov, V.P. Yakovlev Fermilab, Batavia, USA
	Project X based on the 3 GeV CW superconducting Linac and is currently in the R&D phase. The cw SC Linac starts from a low-energy SCRF section (2.1 - 165 MeV) containing three different types of resonators. HWR f=162.5 MHz (2.1 - 11 MeV) having β= 0.11, SSR1 f= 325 MHz (11 - 35 MeV) having β = 0.21. In this paper we present the analysis that lead to the final design of SSR2 f=325 MHz cavity (35 - 165 MeV). We present the results of optimization of the geometric beta and the comparison between single, double and triple spoke resonators used in Project X frontend.

WEPPC046	Overview of Project X Superconducting RF Cavities and Cryomodules	cryomodule, linac, SRF, focusing	2315
	T.N. Khabiboulline, M.S. Champion, C.M. Ginsburg, V.P. Yakovlev Fermilab, Batavia, USA
	The Project X Linac is based primarily on superconducting RF technology starting from a low beam energy of approximately 2.5 MeV up to the exit energy of 8 GeV. The Linac consists of 162.5 MHz half-wave cavities, 325 MHz single-spoke cavities, and two families of 650 MHz elliptical cavities - all operating in continuous-wave mode - up to a beam energy of 3 GeV. The beam is further accelerated up to 8 GeV in a pulsed mode ILC-like Linac utilizing 1.3 GHz cavities. In this paper we will give an overview of the design and status of the Project X superconducting RF cavities and cryomodules.

WEPPC047	Effects of the RF Field Asymmetry in SC Cavities of the Project X	linac, multipole, acceleration, focusing	2318
	I.V. Gonin, M.H. Awida, P. Berrutti, A. Saini, B.G. Shteynas, N. Solyak, V.P. Yakovlev Fermilab, Batavia, USA P.N. Ostroumov ANL, Argonne, USA
	The low-energy SCRF section of CW SC linac of Project X starts from Half Wave Resonators (HWR) having operating frequency f=162.5 MHz, optimal β= 0.11 and will accelerate the beam from 2 MeV up to 11 MeV. The preliminary analysis of beam dynamics shows that multipole effects caused by asymmetry of RF fields in HWR cavities aren’t negligible. In this paper we present the analysis of influence of multipole effects on beam dynamics and discuss the possible solutions how to compensate these effects.

WEPPC049	Individual RF Test Results of the Cavities Used in the First US-built ILC-type Cryomodule	cryomodule, SRF, radio-frequency, linear-collider	2321
	A. Hocker, A.C. Crawford, E.R. Harms, A. Lunin, D.A. Sergatskov, A.I. Sukhanov Fermilab, Batavia, USA G.V. Eremeev, R.L. Geng JLAB, Newport News, Virginia, USA J.P. Ozelis FRIB, East Lansing, USA
	Funding: Work supported in part by the U.S. Department of Energy under Contract No. DE-AC02-07CH11359. Eight 1.3-GHz, nine-cell SRF cavities have been installed in a cryomodule intended to demonstrate the ILC design goal of 31.5 MV/m. These cavities all underwent two types of individual RF testing: a low-power continuous-wave test of the “bare” cavity and a high-power pulsed test of the “dressed” cavity. Presented here is a discussion of the results from these tests and a comparison of their performance in the two configurations.

Paper

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Other Keywords

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MOYBP01

State-of-the-Art and Future Prospects in RF Superconductivity

SRF, niobium, electron, storage-ring

11

K. Saito
KEK, Ibaraki, Japan

This presentation should recount the remarkable progress in improving the performance of superconducting cavities over the past 50 years and explore future directions, including advances in materials other than Nb, such as MgB2 and novel multi-layer superconductor-insulator systems. This talk should provide an overview of international activities.

Slides MOYBP01 [10.097 MB]

MOOBB01

Transverse-to-longitudinal Emittance-exchange with an Energy Chirped Beam

emittance, electron, simulation, radiation

49

J.C.T. Thangaraj, H.T. Edwards, A.S. Johnson, A.H. Lumpkin, T.J. Maxwell, J. Ruan, J.K. Santucci, Y.-E. Sun, R.M. Thurman-Keup
Fermilab, Batavia, USA

Emittance exchange has been proposed to increase the performance of free electron lasers by tailoring the phase space of an electron beam. The principle of emittance exchange - where the transverse phase space of the electron beam is exchanged with the longitudinal phase space - has been demonstrated recently at the A0 photoinjector. The experiment used a low charge bunch (250 pC) with no energy chirp. Theory predicts an improvement in the emittance exchange scheme when the incoming beam has an energy chirp imparted on it. The energy chirp helps to overcome the thick lens effect of the deflecting mode cavity and other second order effects that might lead to an incomplete emittance exchange at higher charges. In this work, we report experimental and simulation results from operating the emittance exchange beam line using an energy chirped beam with higher charge (500 pC) at different RF-chirp settings.

Slides MOOBB01 [2.338 MB]

MOOAC01

The European XFEL LLRF System

LLRF, cryomodule, klystron, laser

55

J. Branlard, G. Ayvazyan, V. Ayvazyan, M.K. Grecki, M. Hoffmann, T. Jeżyński, I.M. Kudla, T. Lamb, F. Ludwig, U. Mavrič, S. Pfeiffer, H. Schlarb, Ch. Schmidt, H.C. Weddig, B.Y. Yang
DESY, Hamburg, Germany
P. Barmuta, S. Bou Habib, L. Butkowski, K. Czuba, M. Grzegrzółka, E. Janas, J. Piekarski, I. Rutkowski, D. Sikora, L. Zembala, M. Żukociński
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
W. Cichalewski, K. Gnidzińska, W. Jałmużna, D.R. Makowski, A. Mielczarek, A. Napieralski, P. Perek, A. Piotrowski, T. Pożniak, K.P. Przygoda
TUL-DMCS, Łódź, Poland
S. Korolczuk, J. Szewiński
The Andrzej Soltan Institute for Nuclear Studies, Centre Świerk, Świerk/Otwock, Poland
K. Oliwa, W. Wierba
IFJ-PAN, Kraków, Poland

The European X-ray free electron laser accelerator consists of 800 superconducting cavities grouped in 25 RF stations. The challenges associated with the size and complexity of this accelerator required a high-precision, modular and scalable low level RF (LLRF) system. TheμTCA technology (uTCA) was chosen to support this system and adapted for RF standards. State-of-the-art hardware development in close collaboration with the industry allowed for the system continuity and maintainability. The complete LLRF system design is now in its final phase and the designed hardware was installed and commissioned at FLASH. The uTCA hardware system, measurement results and system performance validation will be shown. Operational strategy and plans for future automation algorithms for performance optimization will also be presented in this paper.

Slides MOOAC01 [12.188 MB]

MOOAC03

Superconducting Resonators Development for the FRIB and ReA Linacs at MSU: Recent Achievements and Future Goals

linac, cryomodule, SRF, ion

61

A. Facco
INFN/LNL, Legnaro (PD), Italy
E.C. Bernard, J. Binkowski, C. Compton, J.L. Crisp, L.J. Dubbs, K. Elliott, A. Facco, L.L. Harle, M. Hodek, M.J. Johnson, D. Leitner, M. Leitner, I.M. Malloch, S.J. Miller, R. Oweiss, J. Popielarski, L. Popielarski, K. Saito, J. Wei, J. Wlodarczak, Y. Xu, Y. Zhang, Z. Zheng
FRIB, East Lansing, Michigan, USA
A. Burrill, G.K. Davis, K. Macha, A.V. Reilly
JLAB, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The superconducting driver and post-accelerator linacs of the FRIB project, the large scale radioactive beam facility under construction at MSU, require the construction of about 400 low-beta Quarter-wave (QWR) and Half-wave resonators (HWR) with four different optimum velocities. 1st and 2nd generation prototypes of β=0.041 and 0.085 QWRs and β=0.53 HWRs have been built and tested, and have more than fulfilled the FRIB and ReA design goals. The present cavity surface preparation at MSU allowed production of low-beta cavities nearly free from field emission. The first two cryostats of β=0.041 QWRs are now in operation in the ReA3 linac. A 3rd generation design of the FRIB resonators allowed to further improve the cavity parameters, reducing the peak magnetic field in operation and increasing the possible operation gradient , with consequent reduction of the number of required resonators. The construction of the cavities for FRIB, which includes three phases for each cavity type (development, pre-production and production runs) has started. Cavity design, construction, treatment and performance will be described and discussed.
Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics.

Slides MOOAC03 [4.009 MB]

MOOBC01

Electron Linac Photo-fission Driver for the Rare Isotope Program at TRIUMF

cryomodule, gun, TRIUMF, linac

64

S.R. Koscielniak, F. Ames, R.A. Baartman, I.V. Bylinskii, Y.-C. Chao, D. Dale, R.J. Dawson, A. Koveshnikov, A. Laxdal, R.E. Laxdal, F. Mammarella, L. Merminga, A.K. Mitra, Y.-N. Rao, V.A. Verzilov, D. Yosifov, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
D. Karlen
Victoria University, Victoria, B.C., Canada

The TRIUMF Advanced Rare Isotope Laboratory (ARIEL) is funded since 2010 June by federal and BC Provincial governments. In collaboration with the University of Victoria, TRIUMF is proceeding with construction of a new target building, connecting tunnel, rehabilitation of an existing vault to contain the electron linear accelerator, and a cryogenic compressor building. TRIUMF starts construction of a 300 keV thermionic gun, and 10 MeV Injector cryomodule (EINJ) in 2012; the designs being complete. The 25 MeV Accelerator Cryomodule will follow in 2013. TRIUMF is embarking on major equipment purchases and has signed contracts for 4K cryogenic plant and a 290kW CW klystron, and four 1.3 GHz Nb 9-cell cavities from a local Canadian supplier. Moreover, the low energy beam transport is under construction; and detailing of two intra-cryomodule beam transports has just begun. Procurements are anticipated in mid 2012 for (i) the entire facility quadrupole magnets, and (ii) the klystron's 600kW HV power supply.

Slides MOOBC01 [4.852 MB]

MOOBC02

Status of Main Linac Cryomodule Development for Compact ERL Project

linac, HOM, cryomodule, damping

67

K. Umemori, K. Enami, T. Furuya, H. Sakai, M. Satoh, K. Shinoe
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

The Compact ERL, which is a test facility of ERL, is under construction at KEK, in Japan. For the main linac, one cryomodule, containing two 9-cell superconducting cavities, is under development. The cryomodule has been designed under High Pressure Gas Safety Code in Japan. Thermal design and cavity alignment have been also carefully considered. Two 9-cell cavities were already fabricated and their performances were confirmed by vertical tests. They satisfied ERL main linac specifications. Their accelerating field reached to 25 MV/m, without field limits. Two input couplers, three HOM absorbers and two Slide-Jack tuners are also under fabrication for the cryomodule. High power processing will be applied for input couplers, at a test stand using a 300 kW klystron. Cooling tolerance and HOM damping abilities were tested for HOM absorbers. Some performance studies were also applied for the tuner at room temperature condition. Cryomodule assembly is planned on this summer. After cooling tests and high power tests will be carried out, ERL beam operation will be started.

Slides MOOBC02 [3.849 MB]

MOPPC003

Very Fast LHC Crab Cavity Failures and their Mitigation

luminosity, simulation, betatron, optics

121

T. Baer, R. Calaga, R. De Maria, S.D. Fartoukh, E. Jensen, R. Tomás, J. Tückmantel, J. Wenninger, B. Yee-Rendon, F. Zimmermann
CERN, Geneva, Switzerland
T. Baer
University of Hamburg, Hamburg, Germany

For the high-luminosity LHC upgrade program (HL-LHC), the installation of crab cavities (CCs) is needed to compensate the geometric luminosity loss due to the crossing angle and for luminosity leveling [*]. The baseline is a local scheme with CCs around the ATLAS and CMS experiments. In a failure case (e.g. a control failure or arcing in the coupler), the voltage and/or phase of a CC can change significantly with a very fast time constant of the order of 1 to 10 LHC turns. This can lead to large, global betatron oscillations of the beam. The impact of CC failures on the beam dynamics is discussed and the results from dedicated simulations are presented. Mitigation strategies to limit the impact of CC failures to an acceptable level are proposed.
* F. Zimmermann and O. Brüning, “Parameter Space for the LHC High-Luminosity Upgrade”, IPAC'12, MOPPC005, May 2012.

MOPPC015

Proposal for an RF Roadmap Towards Ultimate Intensity in the LHC

klystron, feedback, injection, beam-loading

154

P. Baudrenghien, T. Mastoridis
CERN, Geneva, Switzerland

The LHC is currently operated with 1380 bunches at 50 ns spacing and 1.4 E11 p per bunch (0.35A DC). In this paper the RF operation with ultimate bunch intensity (1.7 E11 p per bunch) and 25 ns spacing (2808 bunches per beam) summing up to 0.86A DC is presented. With the higher beam current, the demanded klystron power will be increased and the longitudinal stability margin reduced. In addition one must consider the impact of a klystron trip (voltage and power transients in the three turns latency before the beam is actually dumped). In this work a scheme is proposed that can deal with ultimate bunch intensity, without modification to the RF power system. Only a minor upgrade of the LLRF will be necessary: the field set point will be modulated according to the phase shift produced by the transient beam loading, thus minimizing the requested RF power while keeping the strong feedback for stability and reduction of RF noise.

MOPPC036

Influence of Intense Beam in High Pressure Hydrogen Gas Filled RF Cavities

electron, plasma, proton, pick-up

208

K. Yonehara, M.R. Jana, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup
Fermilab, Batavia, USA
M. Chung
Handong Global University, Pohang, Republic of Korea
M.G. Collura
Politecnico di Torino, Torino, Italy
G. Flanagan, R.P. Johnson, M. Notani
Muons, Inc, Batavia, USA
B.T. Freemire, Y. Torun
IIT, Chicago, Illinois, USA

Funding: This work is supported by US DOE under contract DE-AC02-07CH11359.
Breakdown plasma in a high-pressure hydrogen gas filled RF cavity has been studied from a time domain spectroscopic light analysis. The observed breakdown plasma temperature and density reached 21,000 K and 10²⁰ cm^-3, respectively. The electron recombination rate has been evaluated from the decay of plasma density in various gas pressures. The recombination mechanism in dense plasma will be discussed. Finally, the similarity and difference of the breakdown processes between the high-pressure hydrogen gas filled RF cavity and a vacuum RF one will be discussed.

MOPPC039

Electron Recombination in a Dense Hydrogen Plasma

electron, collider, plasma, ion

217

B.T. Freemire, P.M. Hanlet
IIT, Chicago, Illinois, USA
M. Chung
Handong Global University, Pohang, Republic of Korea
M.G. Collura
Politecnico di Torino, Torino, Italy
M.R. Jana, C. Johnstone, T. Kobilarcik, G.M. Koizumi, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup, Y. Torun, K. Yonehara
Fermilab, Batavia, USA
R.P. Johnson
Muons, Inc, Batavia, USA

Funding: US DOE under contract DE-AC02-07CH11359.
A high pressure hydrogen gas filled RF cavity was subjected to an intense proton beam to study the evolution of the beam induced plasma inside the cavity. The electron recombination rate with the dense ionized hydrogen plasma has been measured under varying conditions. Recombination rates as high as 10^-7 cm³/s have been recorded. This technique shows promise in the R&D program for a muon accelerator. The use of hydrogen, both as a way to prevent breakdown in an RF cavity and as a mechanism for cooling a beam of muons, will be discussed.

MOPPC040

Study of Electronegative Gas Effect in Beam-Induced Plasma

plasma, electron, proton, ion

220

M.A. Leonova, M.R. Jana, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, USA
M. Chung
Handong Global University, Pohang, Republic of Korea
M.G. Collura
Politecnico di Torino, Torino, Italy
B.T. Freemire, P.M. Hanlet, Y. Torun
IIT, Chicago, Illinois, USA
R.P. Johnson
Muons, Inc, Batavia, USA

Funding: This research was supported by US DOE under contract DE-AC02-07CH11359.
Muon Colliders and Neutrino Factories call for R&D for a high-gradient RF system capable of operating in a high magnetic field. Adding a high pressure gas inside an RF cavity (HPRF) prevents cavity breakdown, allowing higher gradients in a magnetic field. A high-energy beam passing through an HPRF cavity ionizes the gas, producing plasma. Plasma electrons absorb cavity’s energy, reducing the energy available for beam acceleration. Doping cavity gas with electronegative gas (gas that tends to attract and bond electrons) reduces the number of plasma electrons. The experiments were carried out at the MuCool Test Area (MTA) facility at Fermilab. Different concentrations of an electronegative gas SF6 were added to hydrogen gas. The results of room-temperature tests showing a great reduction in power drop in the cavity will be presented. However, a realistic cavity would operate at liquid nitrogen temperature, where SF6 freezes. Thus, a search for a better electronegative gas candidate is underway; we plan to test oxygen-doping next.

MOPPC058

Eigenmode Computation for Ferrite-loaded Cavity Resonators

resonance, heavy-ion, acceleration, ion

265

K. Klopfer, W. Ackermann, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

The GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt is operating the heavy-ion synchrotron SIS18 for fundamental research. Within the ring two ferrite-loaded cavity resonators are installed. During the acceleration phase their resonance frequency has to be adjusted to the revolution frequency of the heavy-ions to reflect their increasing velocity. Within the resonator structures dedicated biased ferrite rings are installed. In the whole setup a properly chosen bias current is used to modify the differential permeability of the ferrite material which consequently enables to adjust the eigenfrequency of the resonator system. The goal of the current study is to numerically determine the lowest eigensolutions of accelerating ferrite-loaded cavities based on the Finite Integration Technique. Since the underlying eigenmodes depend on the differential permeability, the static magnetic field generated by the bias current has to be computed in a first step. The eigenmodes can then be determined with the help of a dedicated Jacobi-Davidson eigensolver. Particular emphasis is put on the implementation to enable high performance computations based on distributed memory machines.

MOPPC059

Various Approaches to Electromagnetic Field Simulations for RF Cavities

simulation, impedance, electromagnetic-fields, HOM

268

C. Liu, W. Ackermann, W.F.O. Müller, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Work supported by BMBF under contract 05H09RD5.
The Superconducting Proton Linac (SPL) cavity is mainly designed and conducted by CERN. It is a part of the planned injector upgrade of the Large Hadron Collider (LHC). The SPL cavity is used to accelerate the ion beam from 160 MeV to 5GeV and served as a driver for neutrino facilities and radioactive beam facilities. In the Superconducting Proton Linac (SPL) cavity, it is very important to calculate the eigenmodes precisely, because many higher-order modes (HOMs) can lead to particle beam instabilities. We used and compared three different ways to calculate the eigenmodes in the SPL cavity: field simulation with hexahedron mesh in frequency domain, field simulation with hexahedron mesh in time domain, and field simulation with tetrahedral mesh and higher order curvilinear elements. In this paper the principles of the three numerical methods will be introduced and compared. Finally the calculated results will be presented.

MOPPC062

Eigenmode Computation for Cavities with Perturbed Geometry Based on a Series Expansion of Unperturbed Eigenmodes

HOM, factory, wakefield, higher-order-mode

277

K. Brackebusch, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany

Funding: Work supported by Federal Ministry for Research and Education BMBF under contracts 05H09HR5 and 05K10HRC.
The geometry of an accelerator cavity determines its eigenmodes and thereby its performance characteristics. Therefore, accelerating performance and wakefield characteristics may be improved by an intentional modification of the geometry. However, undesired geometry perturbations due to manufacturing tolerances and operational demands can likewise impair it. To analyze the effects of geometry variations on the eigenmodes, parameter studies are to be undertaken. Using common eigenmode solvers it usually is necessary to perform a full eigenmode computation for each variation step, even if the geometry is only slightly altered. Parameter studies for cavity perturbations thus tend to be computationally extensive and inefficient. In this paper, we present the fundamentals of an efficient eigenmode computation method for varying cavity geometries. Knowing a set of initial eigenmodes of an unperturbed geometry, the method allows expanding the eigenmodes of any geometry that is part of the unperturbed one as a series of the initial eigenmodes. Thereby the computation effort may be significantly reduced. The method is demonstrated by means of analytically evaluable cavity geometries.

MOPPC070

Field Emission Simulation for KEK-ERL 9-Cell Superconducting Cavity

electron, simulation, linac, coupling

295

E. Cenni
Sokendai, Ibaraki, Japan
T. Furuya, H. Sakai, M. Satoh, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
M. Sawamura
JAEA/ERL, Ibaraki, Japan

In order to develop the Energy Recovery Linac at KEK, we are studying the performance of L-band superconducting cavities by means of vertical tests. One of the limiting factor for the cavities performance is power losses due to field emitted electrons. With regard to this phenomena, a particle tracking code is used to study electron trajectories and deposited energy on the inner surface of the cavity. Different emitters location were tested within a range of accelerating field and phases in order to reproduce different scenario. The final goal of this study is to locate the sources of the electrons inside the cavity through a deeper understanding of the phenomena. To validate the results from the simulation the outcome data are compared with other particle tracking codes.

MOPPC081

Simulation of RF Cavity Dark Current in Presence of Helical Magnetic Field

electron, simulation, dipole, site

325

G.V. Romanov, V.S. Kashikhin
Fermilab, Batavia, USA

In order to produce muon beam of high enough quality to be used for a Muon Collider, its large phase space must be cooled several orders of magnitude. This task can be accomplished by ionization cooling. Ionization cooling consists of passing a high-emittance muon beam alternately through regions of low-Z material, such as liquid hydrogen, and very high accelerating RF cavities within a multi-Tesla solenoidal focusing channel. But first high power tests of an RF cavity with beryllium windows in a solenoidal magnetic field showed a dramatic drop in accelerating gradient due to RF breakdowns. It has been concluded that external magnetic fields parallel to the RF electric field significantly modifies the performance of RF cavities. However, the magnetic field in a Helical Cooling Channel has a strong dipole component in addition to a solenoidal one. The dipole component essentially changes electron motion in a cavity compared to a pure solenoidal case, making dark current less focused at field emission sites. The simulation of a dark current dynamic in HCC performed with CST Studio Suite is presented in this paper.

MOPPC095

XAL's Online Model at ReA3 to Understand Beam Performance

linac, simulation, cryomodule, lattice

358

C. Benatti
NSCL, East Lansing, Michigan, USA
P. Chu, M.J. Syphers, X. Wu
FRIB, East Lansing, Michigan, USA

Funding: This material is based on work supported by the National Science Foundation under Grant No. PHY-1102511 and by Michigan State University.
The ReA3 facility at the NSCL at MSU has been designed to reaccelerate rare isotope beams to 3MeV/u. ReA3 consists of a charge to mass selection section, a normal conducting RFQ, a superconducting linac, and transport beam lines that deliver the beam to the experiments. The beam optics designs were developed using COSY and IMPACT. A code with an online model capable of interacting with the control system, such as XAL, developed at SNS, would be ideal for studying this system*. New elements have been added to XAL’s already extensive list of supported devices in order to model elements unique to the NSCL. The benchmarking process has been completed for establishing the use of XAL’s Online Model at the NSCL, and preliminary results from its use at the ReA3 control room have been obtained. The development of applications to fit the needs of the program is ongoing. A summary of the benchmarking process is presented including both transverse and longitudinal studies.
* J. Galambos et al., Proc. PAC 2005, p. 79, (2005); doi: 10.1109/PAC.2005.1590365.

MOPPC096

Multiphysics Applications of ACE3P

simulation, HOM, vacuum, SRF

361

K.H. Lee, C. Ko, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA
G. Cheng, H. Wang
JLAB, Newport News, Virginia, USA

Funding: Work supported by US DOE Offices of HEP, ASCR and BES under contract AC02-76SF00515.
The TEM3P module of ACE3P, a parallel finite-element electromagnetic code suite from SLAC, focuses on the multiphysics simulation capabilities, including thermal and mechanical analysis for accelerator applications. In this pa- per, thermal analysis of coupler feedthroughs to supercon- ducting rf (SRF) cavities will be presented. For the realistic simulation, internal boundary condition is implemented to capture RF heating effects on the surface shared by a di- electric and a conductor. The multiphysics simulation with TEM3P matched the measurement within 0.4%.

MOPPD033

Strong-focusing Cyclotron - High-current Applications

cyclotron, dipole, proton, focusing

436

P.M. McIntyre, S. Assadi, K.E. Badgley, C. Collins, J. Comeaux, R. Garrison, J.N. Kellams, T.L. Mann, A.D. McInturff, N. Pogue, A. Sattarov
Texas A&M University, College Station, Texas, USA

Funding: This work is supported by grants from the State of Texas (ASE) and from the Mitchell Family Foundation.
Quadrupole focusing channels are integrated into the pole faces of a superconducting sector cyclotron, to enable control of the betatron tunes for all orbits. This provision makes it possible to lock the tunes to desired values for all orbits, thereby eliminating resonance crossing and facilitating local orbit bumps for injection and extraction. Optical control is of particular importance for applications where higher beam current is desired, for ADS fission drivers, for spallation neutron sources, and for medical isotope production.

MOPPD034

Flux-coupled Stacking of Cyclotrons for a High-power ADS Fission Driver

cyclotron, injection, focusing, target

439

A. Sattarov, S. Assadi, K.E. Badgley, J.N. Kellams, T.L. Mann, A.D. McInturff, P.M. McIntyre, N. Pogue
Texas A&M University, College Station, Texas, USA

Funding: This work is funded by grants from the State of Texas (ASE) and the Mitchell Family Foundation.
The sector magnets for an isochronous cyclotron are configured as a flux-coupled stack of apertures, each forming an independent cyclotron, separated sufficiently to accommodate independent superconducting rf cavities. The stack strategy makes it possible to deliver any amount of proton beam power consistent with the limitations of each individual cyclotron, and to deliver the aggregate power to a number of spallation targets as dictated by optimum coupling for accelerator-driven subcritical (ADS) fission and by limitations in target transfer.

MOPPP015

Status of the BERLinPro Energy Recovery Linac Project

linac, SRF, booster, quadrupole

601

J. Knobloch, M. Abo-Bakr, W. Anders, R. Barday, K.B. Bürkmann-Gehrlein, V. Dürr, S.C. Heßler, A. Jankowiak, T. Kamps, O. Kugeler, B.C. Kuske, P. Kuske, A.N. Matveenko, G. Meyer, R. Müller, A. Neumann, K. Ott, Y. Petenev, D. Pflückhahn, T. Quast, J. Rahn, S.G. Schubert
HZB, Berlin, Germany

Funding: Funding provided by the BMBF and the State of Berlin
In October 2010 Helmholtz Zentrum Berlin received funding to design and build the Berlin Energy Recovery Linac Project BERLinPro. The goal of this compact ERL is to develop the accelerator physics and technology required to generate and accelerate a 100-mA, 1 mm·mrad emittance beam. Given the flexibility of ERLs, other operation modes such as short-bunch operation will also be investigated. The BERLinPro technology and know-how can then be transferred to a variety of ERL-based applications. Presently, BERLinPro is in the design phase and the optics has been settled. Furthermore, first beam has been achieved with a superconducting RF photoinjector, which represents an important step towards realizing a CW injector for BERLinPro. An overview of the present status and the conceptual design report is presented.

MOPPP023

Effect of DC Photoinjector Gun Voltage on Beam Dynamics in ALICE ERL

gun, electron, booster, linac

616

Y.M. Saveliev, F. Jackson, J.K. Jones, J.W. McKenzie
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The ALICE ERL employs a DC HV photoelectron gun as an electron source. As with other machines in this class, the electron beam is not always of perfect quality. This is aggravated by that the ALICE gun has been operated so far at lower 230kV voltage compared to the design value of 350kV due to hardware limitations. The “two beams” structure was observed and experimentally investigated and found to be the result of complex processes during initial stages of beam acceleration. The experimental observations and data will be compared with those obtained at a nominal 350kV gun voltage. An investigation of the effect of the DC photogun voltage on longitudinal and transverse beam dynamics will be presented and discussed.

MOPPP026

Cryogenic Distribution System for the Proposed Cornell ERL Main Linac

cryomodule, linac, HOM, vacuum

619

E.N. Smith
Cornell University, Ithaca, New York, USA
Y. He, G.H. Hoffstaetter, M. Liepe, M. Tigner
CLASSE, Ithaca, New York, USA

Funding: This material is based upon work supported by the National Science Foundation under Grant No. DMR-0807731.
The proposed Cornell ERL main linac requires a total cooling power of nearly 8kW at 1.8K, 5kW at 5K and over 100kW at 80K. This is distributed over approximately 65 cryomodules, each containing 6 rf cavities and associated input couplers and higher order mode absorbers. situated in two underground tunnels. While the total heat load is comparable to that for each of the 8 individual LHC cryoplants, the very high ratio of dynamic heat load to static heat load, combined with the high power density at various sites produces interesting challenges for the cryogenic distribution system. A schematic view of the design choices selected, some of which are different from existing large cryogenic systems, and the basis for these decisions, is presented in this paper.

MOPPP034

Simulation of the Longitudinal Phase Space Measurement with Transverse Deflecting Structure at PITZ

electron, dipole, emittance, simulation

637

D. Malyutin, M. Krasilnikov, M. Otevřel, F. Stephan
DESY Zeuthen, Zeuthen, Germany

The main goal of the Photo Injector Test facility at DESY, Zeuthen site, (PITZ) is the development, optimization and detailed characterization of electron sources for the short wavelength Free Electron Lasers (FELs) like FLASH and the European XFEL. For successful operation of such type of FELs the injector must provide high quality electron bunches, enough short in duration with high charge and small transverse and longitudinal emittance values. Installation of the Transverse Deflecting Structure (TDS) at PITZ will provide the possibility for detailed characterization of bunch temporal profile, bunch transverse slice emittance and longitudinal phase space. The TDS cavity is currently installed at the PITZ beamline, and commissioning of the whole TDS system is expected in the spring 2012. In the first part of the paper the basic principles of the TDS deflector are described. In the next section, simulation of measurements by TDS cavity applied to the PITZ beam parameters is presented. The temporal resolution for different types of measurements is discussed. Systematic limitations are estimated.

MOPPP035

Initial Emittance and Temporal Response Measurement for GaAs Based Photocathodes

electron, cathode, emittance, laser

640

S. Matsuba
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
Y. Honda, T. Miyajima, T. Uchiyama, M. Yamamoto
KEK, Ibaraki, Japan
X.G. Jin
Institute for Advanced Research, Nagoya, Japan
Y. Takeda
Nagoya University, Nagoya, Japan

For future light source based on Energy Recovery Linac (ERL) is planned in KEK. For the ERL, an ultra low emittance and fast temporal response and high current electron source is needed. To achieve these requirements, a high voltage DC gun with a Negative Electron Affinity photo-cathode is under development. In this development, it is important to investigate the performance of photo-cathodes. We have constructed an ERL gun test stand to measure emittance and temporal profile. We use a solenoid scan technique for emittance measurements and a deflecting cavity technique for temporal profile measurements. In this presentation, we introduce KEK ERL gun test stand and beam test results.

MOPPP045

Status of the Wisconsin SRF Gun

cathode, gun, laser, solenoid

661

R.A. Legg, J. Bisognano, M.J. Bissen, R.A. Bosch, D. Eisert, M.V. Fisher, M.A. Green, K. Jacobs, R.G. Keil, K.J. Kleman, J.G. Kulpin, G.C. Rogers, M.C. Severson
UW-Madison/SRC, Madison, Wisconsin, USA
D. Yavuz
UW-Madison/PD, Madison, Wisconsin, USA

Funding: The University of Wisconsin SRF electron gun program is supported by DOE Award DE-SC0005264.
SRF electron guns hold out the promise of very bright beams for use in electron injectors, particularly for light source applications such as Free Electron Lasers. The University of Wisconsin is midway in a multi-year program to demonstrate a low frequency electron gun based on a quarter wave resonator cavity. The design includes active tuning and a high temperature superconducting solenoid for emittance compensation. We will report on the status of the 4 MeV SRF electron gun, including the cryomodule, the RF power coupler, the main RF power amplifier/low level RF control system, the photocathode laser system, and the diagnostic beamline. Installation is moving forward in a recently renovated experimental vault adjacent to the existing Aladdin synchrotron. First electron beam is expected in the summer 2012.

MOPPP047

Characterization of the First SRF Electron Beam Source at the Naval Postgraduate School

cathode, electron, SRF, coupling

667

A.D. Holmes, A.B. Baxter, C.W. Bennett, J.R. Harris, J.W. Lewellen, R. Swent
NPS, Monterey, California, USA
J.M. Didoszak, J.M. Utschig
ONR, Arlington, Virginia, USA

In June 2011, the Naval Postgraduate school (NPS) received the 500 MHz Mark I quarter-wave superconducting RF (SRF) electron beam source and, among other firsts, completed the first cool down and characterization of an SRF beam source at a US Naval facility. The Mark I has a photocathode with adjustable position and uses a unique cascaded RF coupler design. As part of an on-going advanced electron source development project, the NPS Beam Physics Laboratory (BPL) team continues characterization of the Mark I cavity at various cathode stalk, coupler, and probe positions. Methods and experimentation used to measure the cavity Q and β, as well as characteristic results, with respect to coupler, cathode stalk, and probe positions are presented.

MOPPP076

Design Considerations for a Hybrid Undulator Applied in a Terahertz FEL Oscillator

undulator, FEL, electron, radiation

738

B. Qin, M. Fan, Y.Q. Xiong
Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China
Y.J. Pei
USTC/NSRL, Hefei, Anhui, People's Republic of China
P. Tan
HUST, Wuhan, People's Republic of China

A planer undulator using hybrid permanent magnet scheme was designed for a FEL based 1THz~3THz radiation source. The influence of the undulator magnetic field errors, including peak field shift and field integrals errors, on the coherent radiation performance such as the gain per pass is investigated. And finally specifications of the undulator are determined.

MOPPR035

Study of the Signal Processing System for a Cavity Beam Position MonitorS

FEL, electron, factory, simulation

855

B.P. Wang, Y.B. Leng, L.Y. Yu, W.M. Zhou
SINAP, Shanghai, People's Republic of China
Z.C. Chen, R.X. Yuan, N. Zhang
SSRF, Shanghai, People's Republic of China

A cavity beam position monitor (CBPM), which can realize nanometer-level resolution as reported, is important and indispensable for a free electron laser (FEL) facility. A prototype of CBPM, with resonant frequency of 5712 MHz, has been installed in the Shanghai deep ultraviolet free-electron laser source (SDUV-FEL) facility. A plug & play CBPM signal processor based on a broadband oscilloscope embedded IOC and FFT technology has been developed to do quick evaluation of prototype. According to the evaluation results, a series of simulation using Monte Carlo simulation method, has been carried as a guideline for the design of dedicated CBPM signal processing system. The development progress of signal processing system will be introduced as well.

MOPPR057

Development of a Cavity Beam Position Monitor for CLIC

dipole, linac, coupling, factory

915

F.J. Cullinan, S.T. Boogert, N.Y. Joshi, A. Lyapin
JAI, Egham, Surrey, United Kingdom
E. Calvo, N. Chritin, F. Guillot-Vignot, T. Lefèvre, L. Søby
CERN, Geneva, Switzerland
A. Lunin, M. Wendt, V.P. Yakovlev
Fermilab, Batavia, USA
S.R. Smith
SLAC, Menlo Park, California, USA

The Compact Linear Collider (CLIC) project presents many challenges to its subsystems and the beam diagnostics in particular must perform beyond current limitations. The requirements for the CLIC main beam position monitors foresee a spacial resolution of 50 nm while delivering a 10 ns temporal resolution within the bunch train. We discuss the design of the microwave cavity pick-up and associated electronics, bench top tests with the first prototype cavity, as well as some of the machine-specific integration and operational issues.

MOPPR068

Design and Development of the Diagnostic System for 75 MeV Electron Drive Beam for the AWA Upgrade

diagnostics, controls, wakefield, emittance

942

J.G. Power, S.P. Antipov, M.E. Conde, W. Gai, C.-J. Jing, W. Liu, E.E. Wisniewski, Z.M. Yusof
ANL, Argonne, USA

Funding: Work supported by High Energy Physics, Office of Science, US DOE
We report on the development of the diagnostic system for the ongoing upgrade to the Argonne Wakefield Accelerator (AWA) facility where the electron drive beam energy will be increased from 15 to 75 MeV. The facility will produce a wide dynamic range of drive bunch train formats ranging from a single microbunch of 100 pC to bunch trains of up to 32 bunches spaced by 769 ps with up to 100 nC per bunch. In addition to standard diagnostics, this drive bunch train format poses two challenges for the diagnostic system: (i) the close spacing of the drive bunches, 769 ps, makes resolving the individual pulses difficult and (ii) the dynamic range of the bunch charge varies by x1000. A critical parameter of the drive bunch train for the wakefield accelerator is the charge along the train. To measure this, we are planning to use a 15 GHz digital oscilloscope to read either a BPM or Bergoz FCT. To handle the large dynamic range of charge, the imaging system will make use of GigE Vision cameras and a distributed system of motorized lenses, with remote control of focus, zoom, and aperture, which are operated through terminal servers and RS232 controllers.

MOPPR069

Use of Waveguide and Beam Pipe Probes as Beam Position and Tilt Monitoring Diagnostics with Superconducting Deflecting Cavities

dipole, HOM, monitoring, simulation

945

X. Sun, T.G. Berenc, G. Decker, G.J. Waldschmidt, G. Wu
ANL, Argonne, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357.
Waveguide and beam pipe field probes associated with a superconducting deflecting cavity are explored as beam position and tilt monitoring diagnostics. The superconducting deflecting cavity will be used for the Short-pulse X-rays (SPX) in the Advanced Photon Source (APS) upgrade project. Microwave Studio will be used to simulate the techniques of detecting the fields excited by the beam passing through the cavity and determining how close the beam is on electrical center.

MOPPR070

Beam Profile Measurement in MTA Beam Line for High Pressure RF Cavity Beam Test

proton, diagnostics, linac, electron

948

M.R. Jana, A.D. Bross, S. Geer, C. Johnstone, T. Kobilarcik, G.M. Koizumi, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, USA
M. Chung
Handong Global University, Pohang, Republic of Korea
M.G. Collura
Politecnico di Torino, Torino, Italy
B.T. Freemire, P.M. Hanlet, Y. Torun
IIT, Chicago, Illinois, USA

Funding: This work is supported by the United States Department of Energy under contract DE-AC02-07CH11359.
The recent High Pressure RF (HPRF) cavity experiment at the MuCool Test Area (MTA) used a 400 MeV Linac proton beam to study the beam loading effect. When the energetic proton beam passes through the cavity, it ionizes the inside gas and produces electrons. These electrons consume RF power inside the cavity. The number of electrons produced per cm inside the cavity (at 950 psi Hydrogen gas) per incident proton is 1200. The measurement of beam position and profile are necessary. The MTA is a flammable gas (Hydrogen) hazard zone, so we have developed a passive beam diagnostic instrument using a Chromox-6 scintillation screen and CCD camera. This paper presents quantitative information about beam position and beam profile. A neutral density filter was used to avoid saturation of the CCD camera. Image data is filtered and fitted with a Gaussian function to compute the beam size. The beam profile obtained from the scintillation screen will be compared with a multi-wire beam profile.

MOPPR073

Analysis of Resonant TE Wave Modulation Signals for Electron Cloud Measurements

electron, resonance, coupling, factory

957

S. De Santis
LBNL, Berkeley, California, USA
D. Alesini
INFN/LNF, Frascati (Roma), Italy
J.P. Sikora
CLASSE, Ithaca, New York, USA

Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the US Department of Energy under Contracts DE-FC02-08ER41538, DE-AC02-05CH11231.
Recent TE wave measurements of the electron cloud density in the beampipe at CesrTA and DAΦNE have shown that, especially near cutoff, the microwave excitation takes place by coupling to a standing wave, rather than to a propagating TE mode. With the beampipe acting as a resonant cavity, the effect of the periodic electron cloud density is a modulation of the cavity's resonant frequency. As a result, the measured sidebands are a combination of amplitude, phase, and frequency modulation, as the periodic cloud density modulates this resonant frequency. The quality factor Q of the resonance will determine its response to transients in the electron cloud density, and the resulting effect on modulation sidebands. In order to estimate the peak electron cloud density and its spacial distribution, knowledge of the Q and the standing wave pattern need to be determined, either by experimental measurements or simulation codes. In this paper we analyze the dependence of the modulation sidebands on the electron cloud density in two different regimes, when the cloud rise/decay time is much longer, or much shorter than the filling time of the resonance.

MOPPR074

Using TE Wave Resonances for the Measurement of Electron Cloud Density

resonance, electron, simulation, vacuum

960

J.P. Sikora, M.G. Billing, D. L. Rubin, R.M. Schwartz
CLASSE, Ithaca, New York, USA
D. Alesini
INFN/LNF, Frascati (Roma), Italy
B.T. Carlson
CMU, Pittsburgh, Pennsylvania, USA
S. De Santis
LBNL, Berkeley, California, USA
K.C. Hammond
Harvard University, Cambridge, Massachusetts, USA

Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the US Department of Energy under Contracts DE-FC02-08ER41538, DE-AC02-05CH11231.
In the past few years, electron cloud density has been measured by means of its effect on TE waves propagated through the accelerator vacuum chamber. This technique has been the object of careful studies and has been used in several laboratories around the world (CERN, SLAC, FNAL, Cornell, INFN-LNF). Recent measurements at CesrTA and DAΦNE show that in a majority of practical cases, the theoretical model that relates the cloud density to the phase shift induced on a TE wave propagating in beam pipe may not be the correct one. Instead, the measurement results have to be analyzed considering the effect of the electron cloud on a standing wave excited between the input and output couplers - typically Beam Position Monitors (BPMs). This standing wave pattern is not confined to the portion of beampipe between the BPMs and must be understood in order to correctly interpret the measurement. In this paper we present evidence that the transmission function near cutoff between two BPMs is the result of coupling to standing waves trapped in the vacuum chamber. This evidence includes measurements at DAΦNE, Cesr-TA, a test waveguide, computer EM simulations, and analytical calculations.

MOPPR088

Cavity BPM for 1300 MHz Cryomodules

coupling, dipole, wakefield, cryomodule

993

N. Barov, D.J. Newsham, D. Wu
Far-Tech, Inc., San Diego, California, USA

Funding: Work supported by DOE grant DE-SC00004498
A cavity BPM for 1300 MHz cryomodules is under development by FAR-TECH, Inc. The BPM is capacitively loaded to fit in a small area, and uses a novel coupling scheme which further cuts down space requirements. We discuss status of the fabrication, and eventual plan to test the diagnostic at the ANL Wakefield Accelerator facility.

TUYA01

Research and Development of Future Muon Collider

collider, plasma, proton, emittance

1020

K. Yonehara
Fermilab, Batavia, USA

A muon collider would provide a unique facility for future elementary-particle physics research, and present unique challenges for accelerator physics and technology. An R&D effort is underway to address major challenges in the design of a future muon collider. This talk should provide an opportunity to discuss the muon collider's challenges, present recent R&D results, and describe future prospects.

TUOAB01

Timing and Synchronization for the APS Short Pulse X-ray Project

laser, feedback, LLRF, storage-ring

1077

F. Lenkszus, N.D. Arnold, T.G. Berenc, G. Decker, E.M. Dufresne, R.I. Farnsworth, Y.L. Li, R.M. Lill, H. Ma
ANL, Argonne, USA
J.M. Byrd, L.R. Doolittle, G. Huang, R.B. Wilcox
LBNL, Berkeley, California, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Short-Pulse X-ray (SPX) project, which is part of the APS upgrade, will provide intense, tunable, high-repetition-rate picosecond x-ray pulses through the use of deflecting cavities operating at the 8th harmonic of the storage-ring rf. Achieving this picosecond capability while minimizing the impact to other beamlines outside the SPX zone imposes demanding timing and synchronization requirements. For example, the mismatch between the upstream and downstream deflecting cavities' rf field phase is specified to be less than 0.077 degrees root mean squared (rms) at 2815 MHz (~77 femtoseconds). Another stringent requirement is to synchronize beamline pump-probe lasers to the SPX x-ray pulse to 400 femtoseconds rms. To achieve these requirements we have entered into a collaboration with the Beam Technology group at LBNL. They have developed and demonstrated a system for distributing stable rf signals over optical fiber capable of achieving less than 20 femtoseconds rms drift and jitter over 2.2 km over 60 hours*. This paper defines the overall timing/synchronization requirements for the SPX and describes the plan to achieve them.
* R. Wilcox et al. Opt. Let. 34(20), Oct 15, 2009

Slides TUOAB01 [2.515 MB]

TUEPPB004

A Longitudinal Beam Dynamics Code for Proton Synchrotron

simulation, space-charge, synchrotron, bunching

1119

Y.S. Yuan, N. Wang, S. Wang, S.Y. Xu
IHEP, Beijing, People's Republic of China

The accelerator of China Spallation Neutron Source (CSNS) consists of an 80 MeV linac and a 1.6 GeV Rapid Cycling Synchrotron (RCS). Longitudinal beam dynamics study is one of the most important issues for RCS beam dynamics design. However, the existing codes cannot meet the requirement of longitudinal beam dynamics for CSNS/RCS. A new code has been developed for longitudinal beam dynamics design and simulation. The code can perform the voltage and phase curves design for non-sinusoidal magnetic field of dipole in an RCS cycle, with the fundamental RF mode and dual harmonic mode. The code can also be used for the beam simulation with longitudinal space charge effect, including the effects of higher order mode of RF cavities. By using the code, the longitudinal beam dynamics of CSNS/RCS was designed and optimized, and the simulation study with dual harmonics higher order modes of RF cavity was done, and the simulation results are presented.

TUEPPB008

Status Report on the Iranian Light Source Facility Project

storage-ring, booster, synchrotron, dipole

1131

J. Rahighi, H. Ajam, R. Aslani, S. Fatehi, H. Ghasem, M.R. Khabazi, R. Safian, E. Salimi, A. Shahveh
IPM, Tehran, Iran
E. Ahmadi, M. Jafarzadeh, H.B. Jalali, M. Moradi, S. Pirani, M. Rahimi, A. Sadeghipanah, F. Saeidi, Kh.S. Sarhadi, A. Shahverdi
ILSF, Tehran, Iran
D. Einfeld
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain

The Iranian Light Source Facility Project (ILSF) is a 3rd generation light source with an energy of 3 GeV,a full energy injector and a 100 MeV linac as preinjector. For storage ring, booster synchrotron and linac including the transfer lines, a draft design has been completed and will be presented. The storage ring has an emittance of 3.3 nm-rad, a circumference of 297.6 meters with an overall of 32 straight sections of different lengths. The booster synchrotron has a circumference of 197 meters and emittance of 35nm-rad. For the booster synchrotron a new lattice is proposed. The linac is a conventional 150 MeV accelerator. The different accelerator components, magnets, girders, power supplies, vacuum systems etc. are in the design phase. State of the art design for different components is employed through international collaboration.

TUPPC010

Study of Effects of Failure of Beamline Elements and its Compensation in CW Superconducting Linac

linac, beam-losses, emittance, focusing

1173

A. Saini, K. Ranjan
University of Delhi, Delhi, India
C.S. Mishra, J.-F. Ostiguy, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, USA

Project-X is the proposed high intensity proton facility to be built at Fermilab in United States. First stage of the Project-X consists of H^- superconducting linac (SC) which will be operated in continuous wave (CW) mode to accelerate the beam from kinetic energy of 2.1 MeV to 3 GeV. The operation in CW mode puts stringent tolerances on the beam line components, particularly at low energy section. The failure of beam line elements result in mismatch of the beam with the following sections due to different beam parameters than designed parameters. It makes the beam unstable which causes emittance dilution, and ultimately results in beam losses. In worst case, it can affect the reliability of the machine and may lead to the shutdown of the linac to replace the failed elements. Thus, it is important to study impacts of these effects and their compensation to restore linac performance to avoid beam interruption. This paper presents the studies performed for the failure of accelerating cavity and focusing magnets at the critical locations in the Project-X CW superconducting linac

TUPPC011

Beam Steering Correction in FRIB Quarter-wave Resonators

linac, simulation, cryomodule, solenoid

1176

A. Facco
INFN/LNL, Legnaro (PD), Italy
A. Facco, Y. Xu, Y. Zhang, Q. Zhao, Z. Zheng
FRIB, East Lansing, Michigan, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Quarter-Wave Resonators (QWR) section of the FRIB superconducting driver linac is required to accelerate Uranium beam up to 16 MeV/u in two different charge states simultaneously. This puts severe requirements on resonators alignment and field quality, in order to avoid beam losses and emittance growth. In particular, QWR beam steering can cause transverse oscillations of the beam centroid which reduce the linac acceptance and induces emittance growth. We have studied, with an analytical model and with 3D beam dynamics simulations, correction methods for the FRIB QWRs steering. We found that cavity shifting can provide effective steering cancellation in FRIB QWRs without need of cavity shape modifications, and allows to eliminate transverse beam oscillations and to improve beam quality. Calculation and simulation methods and results will be presented and discussed.
Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics.

TUPPC026

Design of Compact C-Band Standing-Wave Accelerating Structure Enhancing RF Phase Focusing

coupling, bunching, focusing, simulation

1221

H.R. Yang, M.-H. Cho, J. Jang, S.H. Kim, W. Namkung, S.J. Park
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.-S. Oh
NFRI, Daejon, Republic of Korea

Funding: Work supported by POSTECH Physics BK21 Program.
We design a C-band standing-wave accelerating structure for an X-ray source of the imaging and medical applications. It is capable of producing 6-MeV, 100-mA pulsed electron beams which is focused by less than 1.5 mm without external magnets. As an RF source, we use peak 1.5-MW magnetron with duty factor of 0.08%. The accelerating structure is a bi-periodic and on-axis-coupled structure with a built-in bunching section, which consists 3 bunching cells, 13 normal cells and a coupler cell. It operated with π/2-mode standing-waves. The bunching section is designed to enhance the RF phase focusing in order to achieve 1.2-mm beam spot size. Each cavity is designed with the MWS code to maximize the effective shunt impedance within 3.5% inter-cell coupling. In this paper, we present design details of RF cavities and the beam dynamics simulation by the PARMELA code.

TUPPC045

Modeling Investigation on a Deflecting-Accelerating Composite RF-cavity System for Phase Space Beam Control

coupling, simulation, klystron, electron

1266

Y.-M. Shin, M.D. Church, P. Piot
Fermilab, Batavia, USA

Phase space manipulations between the longitudinal and transverse degree of freedoms hold great promise toward the precise control of electron beams. Such transverse-to-longitudinal phase space exchange have been shown to be capable of exchanging the transverse and horizontal emittance or controlling the charge distribution of an electron bunch, for beam-driven advanced accelerator methods. The main limitation impinging on the performance of this exchange mechanism stems from the external coupling nature of a realistic deflecting cavity, compared to a thin-lens model. As an extended idea from *, this paper presents the design of a composite 3.9-GHz RF-system consisting of a deflecting- and accelerating-mode cavities. The system design analysis is discussed with particle-in-cell (PIC) simulations of the device performance.
* A. Zholents, PAC'11.

TUPPC053

Longitudinal Tuning of the SNS Superconducting Linac

linac, optics, acceleration, controls

1290

T.V. Gorlov
ORNL, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy.
The SNS superconducting linac delivers proton beam with about 1 GeV of energy driven by self-consistent RF cavities. Here, we present an experience of the longitudinal tune-up of the SNS superconducting linac where a new application for quick RF phase setup and cavity fault adaptation was created. The routine of superconducting linac tune-up, longitudinal beam manipulation, and radio frequency cavity phase scaling for beam state recovery is presented. The application has direct value for beam optics study and will serve as the basis for longitudinal beam-size manipulation for a laser stripping project.

TUPPC054

Beam Acceleration by a Multicell RF Cavity Structure Proposed for Improved Yield in Hydroforming

electron, acceleration, quadrupole, focusing

1293

J.A. Holmes, Y.W. Kang
ORNL, Oak Ridge, Tennessee, USA
A.E. Fathy, K.R. Shin
University of Tennessee, Knoxville, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
We study the accelerating properties of a new multicell cavity structure with irises forming a rectangular aperture between the cavity cells. We are interested in this structure because, from a mechanical point of view, the rectangular iris may make possible a much improved structure quality using a hydroforming manufacturing process. RF analysis shows that the rectangular iris shape provides asymmetric transverse focusing per half RF period. If the horizontal and vertical rectangular irises are interleaved, the net transverse focusing can be increased. The present studies of the acceleration and transport properties of these cavities are conducted by tracking particles through time-dependent 3D cavity fields from CST MWS using the ORBIT Code.

TUPPD003

Optimisation of Cooling Lattice Based on Bucked Coils for the Neutrino Factory

lattice, factory, emittance, simulation

1407

A. Alekou, J. Pasternak
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

The ionisation cooling technique will be used at the Neutrino Factory to reduce the transverse phase space of the muon beam. For efficient cooling, high average RF gradient and strong focusing are required to be applied in the cooling channel. However, high magnetic field at the position of the RF cavities induces electric field breakdown and therefore, a novel configuration, the Bucked Coils lattice, has been proposed to mitigate this problem. The Bucked Coils lattice has significantly lower magnetic field in the RF cavities by using coils of different radius and opposite polarity. This paper presents the optimisation of this lattice, its cooling performance, together with the preliminary conceptual engineering design.

TUPPD006

IDR Neutrino Factory Front End and Variations

proton, target, factory, solenoid

1416

D.V. Neuffer
Fermilab, Batavia, USA
A. Alekou
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
C.T. Rogers
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
P. Snopok
IIT, Chicago, Illinois, USA
C. Y. Yoshikawa
Muons, Inc, Batavia, USA

The (International Design Report) IDR neutrino factory scenario for capture, bunching, phase-energy rotation and initial cooling of muons produced from a proton source target is presented. It requires a drift section from the target, a bunching section and a phase-energy rotation section leading into the cooling channel. The rf frequency changes along the bunching and rotation transport in order to form the muons into a train of equal-energy bunches suitable for cooling and acceleration. This design is being explored within the IDR cost model. Important concerns are rf limitations and beam losses. Recent experiments on rf gradient limits suggest preferred configurations for the rf within the magnetic fields, and these considerations are incorporated into the front end design.

TUPPD010

Helical Muon Beam Cooling Channel Engineering Design

solenoid, simulation, beam-cooling, collider

1425

G. Flanagan, R.P. Johnson, G.M. Kazakevich, F. Marhauser, M.L. Neubauer
Muons, Inc, Batavia, USA
V.S. Kashikhin, M.L. Lopes, G.V. Romanov, M.A. Tartaglia, K. Yonehara, M. Yu, A.V. Zlobin
Fermilab, Batavia, USA

Funding: Supported in part by DOE STTR Grant DE-SC0006266
The Helical Cooling Channel (HCC), a novel technique for six-dimensional (6D) ionization cooling of muon beams, has shown considerable promise based on analytic and simulation studies. However, the implementation of this revolutionary method of muon cooling requires new techniques for the integration of hydrogen-pressurized, high-power RF cavities into the low-temperature superconducting magnets of the HCC. We present the progress toward a conceptual design for the integration of 805 MHz RF cavities into a 10 T Nb3Sn based HCC test section. We include discussions on the pressure and thermal barriers needed within the cryostat to maintain operation of the magnet at 4.2 K while operating the RF and energy absorber at a higher temperature. Additionally, we include progress on the Nb3Sn helical solenoid design

TUPPD014

To the Ionization Cooling in a RF Cavity with Absorber

scattering, focusing, radiation, emittance

1437

A.A. Mikhailichenko
CLASSE, Ithaca, New York, USA

We are considering a RF cavity with Beryllium disk installed in the middle of the cavity as a ionization cooling element for the muon beam. Specially arranged shape of disk together with nonzero dispersion allows 6D cooling of muon beam. Technical aspects of this system and conceptual design are discussed in this paper also. This type of cooler demonstrates advantages if compared with the RF cavity filled with pressurized gas or with the helical cooler.

TUPPD017

Electromagnetic Design of RF Cavities for Accelerating Low-Energy Muons

linac, vacuum, resonance, solenoid

1446

S.S. Kurennoy
LANL, Los Alamos, New Mexico, USA

A high-gradient linear accelerator for accelerating low-energy muons and pions in a strong solenoidal magnetic field has been proposed for homeland defense and industrial applications.* The acceleration starts immediately after collection of pions from a target in a solenoidal magnetic field and brings decay muons, which initially have kinetic energies mostly around 15-20 MeV, to 200 MeV over a distance of ~10 m. At this energy, both ionization cooling and further, more conventional acceleration of the muon beam become feasible. A normal-conducting linac with external-solenoid focusing can provide the required large beam acceptances. The linac consists of independently fed zero-mode (TM010) RF cavities with wide beam apertures closed by thin conducting edge-cooled windows. Electromagnetic design of the cavity, including its RF coupler, tuning and vacuum elements, and field probes, has been developed with the CST MicroWave Studio, and will be presented.
* S.S. Kurennoy, A.J. Jason, H. Miyadera, “Large-Acceptance Linac for Accelerating Low-Energy Muons.” Proceed. IPAC10, p. 3518.

TUPPD019

New Injector for the EMMA ns-FFAG Ring

booster, gun, linac, emittance

1449

B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

EMMA is the world’s first non-scaling FFAG which has recently demonstrated acceleration in the serpentine channel. At present, the electron beam is injected into EMMA from the ALICE accelerator. However, funding will be re-directed to an Electron Beam Test Facility (EBTF) in the near future, therefore, in order to continue the broad portfolio of planned experiments required to characterize non-scaling FFAGs, it essential to consider an alternative injection scheme. In this paper, we propose re-utilizing a thermionic gun and a 12 MeV linac from the SRS (Synchrotron Radiation Source) at Daresbury Laboratory. The paper looks at how the required EMMA beam properties can be matched with this new set-up and the advantages and disadvantages involved.

TUPPD034

Multi-bunch Beam Generation by Photo-cathode RF Gun for KEK-STF

laser, gun, cathode, electron

1479

M. Kuriki, S. Hosoda, H. Iijima
HU/AdSM, Higashi-Hiroshima, Japan
A. Ayaka
Sokendai, Ibaraki, Japan
H. Hayano, J. Urakawa, K. Watanabe
KEK, Ibaraki, Japan
G. Isoyama, R. Kato, K. Kawase
ISIR, Osaka, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
K. Sakaue
RISE, Tokyo, Japan

Funding: MEXT, Quantum beam project.
KEK-STF is doing R&D of Super-Conducting (SC) accelerator technology for ILC (International Linear Collider), based on 1.3 GHz RF system. For STF and ILC, the pulse length is 1ms and the repetition is 5Hz. We developed a L-band Normal-Conducting RF gun designed by DESY to provide electron beam over such long pulse duration. For NC Photo-cathode RF gun, such high duty and long pulse operation is a challenging task, because the detuning by the heat load of cavity dissipation power is significant. The RF gun provides the electron pulse train to SC accelerator modules which will be operated at 31.5 MV/m gradient. Precise RF control is essential for SC accelerator because the beam loading and input RF power should be well ballanced for a stable operation. The beam test to demonstrate the stable opeation is very important for SC accelerator R&D. The system is also used to demonstrate high-flux quasi-monochromatic X-ray generation by inverse Compton scattering at KEK-STF. The experiment is carried out from April 2012 to November 2012 at KEK-STF. We report the latest status of the multi-bunch generation by the RF gun.

TUPPD051

Operational Experience with the Nb/Pb SRF Photoelectron Gun

emittance, cathode, solenoid, laser

1518

T. Kamps, W. Anders, R. Barday, A. Jankowiak, J. Knobloch, O. Kugeler, A.N. Matveenko, A. Neumann, T. Quast, J. Rudolph, S.G. Schubert, J. Völker
HZB, Berlin, Germany
P. Kneisel
JLAB, Newport News, Virginia, USA
R. Nietubyć
The Andrzej Soltan Institute for Nuclear Studies, Centre Świerk, Świerk/Otwock, Poland
J.K. Sekutowicz
DESY, Hamburg, Germany
J. Smedley
BNL, Upton, Long Island, New York, USA
J. Teichert
HZDR, Dresden, Germany
V. Volkov
BINP SB RAS, Novosibirsk, Russia
I. Will
MBI, Berlin, Germany

SRF photoelectron guns offer the promise of high brightness, high average current beam production for the next generation of accelerator driven light sources such as free electron lasers, THz radiation sources or energy-recovery linac driven synchrotron radiation sources. In a first step a fully superconducting RF (SRF) photoelectron gun is under development by a collaboration between HZB, DESY, JLAB, BNL and NCBJ. The aim of the experiment is to understand and improve the performance of a Nb SRF gun cavity coated with a small metallic Pb cathode film on the cavity backplane. This paper describes the highlights from the commissioning and beam parameter measurements. The main focus is on lessons learned from operation of the SRF gun.

TUPPD056

Development of a Photo-injector Laser System for KEK ERL Test Accelerator

laser, cathode, controls, alignment

1530

Y. Honda
KEK, Ibaraki, Japan

As a test accelerator for future light source, Compact Energy Recovery Linac has been constructed in KEK. For its photo-injector, we have been developing a laser system. It requires high repetition rate and high average power at a visible wavelength. Development of an high power fiber amplifier and high efficiency wavelength conversion system utilizing an optical cavity will be reported.

TUPPD058

Development of an RF Electron Gun for Ultra-Short Bunch Generation

gun, electron, cathode, simulation

1536

Y. Koshiba, T. Aoki, K. Sakaue, M. Washio
RISE, Tokyo, Japan
T. Takatomi, J. Urakawa
KEK, Ibaraki, Japan

At Waseda University, various researches are done using a photocathode rf electron gun with a 1.6 cell cavity. Now we are developing a new rf cavity specialized for producing an ultra-short electron bunch, with the collaboration of High Energy Accelerator Research Organization (KEK). We have used SUPERFISH for designing the new rf cavity and PARMELA for beam tracking. The new rf cavity has an extra cell following the 1.6 cell. The extra cell can chirp the energy of electron bunch so we call it ECC (Energy Chirping Cell). ECC chirp the energy because we shortened the length of iris just before the ECC and also the length of ECC itself. Moreover, electric field in ECC is made to be stronger than others. We have confirmed on PARMELA that ECC rf gun can generate an 100pC electron bunch less than 200fsec with the energy of 4.5MeV at about 2.5m away from the cathode. Such an ultra-short electron bunch enables us to generate a coherent terahertz light using ultra-short electron bunch by synchrotron radiation or transition radiation. In this conference, we would like to introduce the detail of the design of this new ECC rf gun, the present progresses and future prospects.

TUPPD062

The Source of Emittance Dilution and photoemission tunneling effect in Photocathode RF Guns

cathode, emittance, laser, simulation

1542

V. Volkov
BINP SB RAS, Novosibirsk, Russia
R. Barday, T. Kamps, J. Knobloch, A.N. Matveenko, S.G. Schubert, J. Völker
HZB, Berlin, Germany
J.K. Sekutowicz
DESY, Hamburg, Germany

Funding: Work supported by Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association VH-NG-636 and HRJRG-214.
Experimental data on HoBiCaT SRF photoinjector give an emittance which is much larger than the predicted thermal emittance. Modeling of photocathode RF gun beams with the different imperfections of experimental setup (alignment errors, inhomogeneity of quantum efficiency and laser power distributions on the cathode) is given. The main reason for the beam emittance dilution is photocathode field imperfections induced by field emitters that change the local electric field. Some field models of such photocathodes are tested in the simulations. The dependence of photocathode beam currents on the surface electric field was measured with the HoBiCaT SRF Photoinjector. The dependence can be explained by the tunneling effect described by Fowler-Nordheim like equation and is difficult to explain by usually applying Schottky effect.

TUPPD063

Interpretation of Dark Current Experimental Results in HZB SC RF Gun

simulation, accelerating-gradient, gun, HOM

1545

V. Volkov
BINP SB RAS, Novosibirsk, Russia
R. Barday, T. Kamps, J. Knobloch, A.N. Matveenko, A. Neumann
HZB, Berlin, Germany

Funding: Work supported by Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association VH-NG-636 and HRJRG-214.
The experimental dark current measurement results are obtained on HZB SC RF gun. The field emitters are considered to be random defects on the back wall of the cavity. Conducting wires with 1 micron length, blobs of 200 micron diameter and ”tip on tip” combination of them are taken as dark current emitters in the cavity. RF fields were calculated with CLANS program. The dynamic simulation of dark currents from these emitters fit experimental data. The emitter heating power by RF induced current is four orders of magnitude larger than by the field emitted dark current. The RF induced emitter temperature is proportional to ω1/2 which explains the accelerating gradient limit of a cavity like Kilpatrik law. The RF processing by high order modes seems to be promising.

TUPPD064

Cathode Insert Design for SC RF Guns

cathode, gun, multipactoring, HOM

1548

V. Volkov
BINP SB RAS, Novosibirsk, Russia
R. Barday, T. Kamps, J. Knobloch, A.N. Matveenko
HZB, Berlin, Germany

Funding: Work supported by Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Assiciation VH-NG-636 and HRJRG-214.
The cathode inserts in superconducting (SC) RF guns are normal conducting devices attached to a SC RF gun cavity. They enable the photocathode replacement and, at the same time, preserve high quality factor and high fields in the RF guns. However, the insert may also limit the gun performance because of multipacting etc. The experience gathered in early designs at Wuppertal [1], and, more recently at BNL [2] and HZDR [3] is taken into account. We consider the design structure of the cathode insert worked out by BINP for 1 cell prototype of SC HZDR RF gun [4]. The detailed electric, mechanic, and thermal calculations of the initial [4] and the upgraded design are presented in this paper.
* A. Michalke et al., EPAC'92, p. 1014 (1992).
** A. Burrill et al., PAC07, p. 2544 (2007).
*** D. Janssen et al., NIM A507, 314 (2003).
**** D. Janssen et al., NIM A445, 408 (2000).

TUPPD068

Design of the Production and Measurement of Ultra-Short Electron Bunches from an S-band RF Photoinjector

gun, dipole, electron, laser

1560

J.W. McKenzie, D. Angal-Kalinin, J.K. Jones, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The Electron Beam Test Facility (EBTF) is planned for installation in late 2012 at Daresbury Laboratory. An S-band RF photoinjector provides ultrashort, low emittance electron bunches up to 6 MeV. A suite of diagnostics has been designed to fully characterise the bunches. A particular focus has been on producing and measuring bunch lengths less than 100 fs. This can be achieved with a multi-cell standing wave S-band transverse deflecting cavity. Operating such a cavity with low energy electrons provides certain challenges which are discussed in this paper with respect to beam dynamic simulations.

TUPPD077

SPEAR3 Booster RF System Upgrade: Performance Requirements and Evaluation of Resources

booster, klystron, injection, linac

1578

S. Park, W.J. Corbett, R.O. Hettel, J.F. Schmerge, J.J. Sebek, J.W. Wang
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.
The SPEAR2 accelerator system originally had 3 RF stations (2 for storage ring, 1 Booster) operating at 358.5 MHz. SPEAR3 now operates at 476.3 MHz with PEP-II type RF system, while the Booster RF frequency remains unchanged. For top-off operation, the Booster injects single 3.0 GeV electron bunches into SPEAR3 at 10 Hz every 5 minutes to replenish lost charge. Due to the frequency mismatch between SPEAR3 and the Booster, only one SPEAR3 bucket can injected per shot limiting injection rate and overall system flexibility. The aging high-power RF subsystems of the Booster pose a reliability issue as well. In order to remove these constraints, studies are underway to replace the Booster RF system using the PEP-II type RF system as a baseline. The new Booster RF system will be tuned to 475.036 MHz, and phase-locked to the SPEAR3 RF system. The project calls for ramping the Booster cavity gap voltage to 0.80 MV at 10 Hz, each with a 40 ms acceleration interval. With very low beam loading and low average RF power, there are many subsystems that can be operationally simplified. In this paper we present the results of analysis leading to a new Booster RF system.

TUPPD078

A Novel Design of a High Brightness Superconducting RF Photoinjector Gun Cavity

gun, SRF, cathode, emittance

1581

F. Marhauser, R. Rodriguez
MuPlus, Inc., Newport News, USA
Z. Li
SLAC, Menlo Park, California, USA

Funding: Work supported under U.S. DOE Grant Application Number 98802B12-I
Next generation electron accelerators for research, medical, defense or industrial use are in need of electron sources operating at high repetition rates of 1 MHz and beyond, with normalized emittance of 1 mm-mrad or less and bunch charges as much as one nC or more. A conceptual layout of a novel superconducting RF photoinjector gun cavity (SRF gun) is proposed, which can provide unprecedented flexibility to vary beam pulse patterns in the MHz regime and beyond at average currents around 1 mA. It does not require an opening in the center of the back wall and avoids the complex cathode exchange system, but still allows an exchange or refurbishment of the cathode. The demountable back plate has the major benefit to clean the cavity cells independently from the back wall carrying a superconductive photocathode. This mitigates risks of cavity contamination and eases fabrication and chemical post-processing to achieve high accelerating fields, a key parameter to guarantee high brightness beams.

TUPPP003

Status and Very First Commissioning of the ASTRID2 Synchrotron Light Source

septum, vacuum, dipole, synchrotron

1605

S.P. Møller, N. Hertel, J.S. Nielsen
ISA, Aarhus, Denmark

ASTRID2 is the new 10 nm UV and soft x-ray light source currently being built at Aarhus University, to replace the ageing source ASTRID. ASTRID2 is now in the end of its installation phase, with commissioning expected to take place during the spring. The status of the installation together with the first results of the commissioning will be presented.

TUPPP042

Passive Landau Cavity Effects in the NSLS-II Storage Ring

storage-ring, simulation, impedance, wakefield

1701

G. Bassi, A. Blednykh, S. Krinsky
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE contract No: DE-AC02-98CH10886.
In new 3rd generation synchrotron light sources with small transverse emittance, higher harmonic cavities (Landau cavities) are installed for bunch lengthening to increase the Touschek lifetime, and to provide Landau damping for beam stability. In this contribution we study the effects of passive Landau cavities in the NSLS-II storage ring for arbitrary fill-patterns with the OASIS tracking code.

TUPPP043

Analysis of Coupled Bunch Instabilities in the NSLS-II Storage Ring with a 7-cell PETRA-III RF Structure

HOM, impedance, damping, simulation

1704

G. Bassi, A. Blednykh, S. Krinsky, J. Rose
BNL, Upton, New York, USA

Funding: Work supported by DOE contract No: DE-AC02-98CH10886.
A 7-cell PETRA-III cavity is considered to be installed for the commissioning Phase 1 in the NSLS-II storage ring at an average current of 25mA. In this contribution we study transverse and longitudinal coupled-bunch instabilities that may be driven by the higher order modes of the 7-cell PETRA-III cavity. The instability thresholds are calculated with the OASIS tracking code, with parameters of the bare lattice (no damping wigglers and Landau cavities). We study multibunch configurations with arbitrary fill-patterns and discuss the slow head-tail effect at positive chromaticity to increase the transverse instability thresholds.

TUPPP059

Effects of Metal Mirrors Reflectivity and Aberrations on THz FEL Radiation Performance

FEL, radiation, undulator, electron

1729

P. Tan, T. Yu
HUST, Wuhan, People's Republic of China
M. Fan, Q. Fu, D. Li, B. Qin, Y.Q. Xiong, Y.B. Yibin
Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China

The primary design study of terahertz free-electron laser (FEL) is presented in this paper. The effects of optical cavity parameter, metal mirrors reflectivity and aberrations on the THz FEL radiation performance have been explored. The reflectivity characteristics of copper, silver and gold are tested in terahertz region. The effects of metal mirrors reflectivity and aberrations on the THz FEL radiation performance are studied by numerical simulation.

TUPPP068

Comparison of Compression Schemes for CLARA

emittance, FEL, linac, sextupole

1756

P.H. Williams, J.W. McKenzie
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.K. Jones, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom

CLARA (Compact Linear Advanced Research Accelerator) at Daresbury Laboratory is proposed to be the UK’s national FEL test facility. The accelerator will be a ~250 MeV electron linac capable of producing short, high brightness electron bunches. The machine comprises a 2.5 cell RF photocathode gun, one 2 m and three 5 m normal conducting S-band (2998MHz) accelerating structures and a variable magnetic compression chicane. CLARA will be used as a test bed for novel FEL configurations. We present a comparison of acceleration and compression schemes for the candidate machine layout.

TUPPR026

Conceptual Design of the CLIC Damping Ring RF System

damping, beam-loading, linac, coupling

1870

A. Grudiev
CERN, Geneva, Switzerland

In order to achieve high luminosity in CLIC, ultra-low emittance bunches have to be generated in both electron and positron damping rings. To achieve this goal, big energy loss per turn in the wigglers has to be compensated by the RF system. This results in very strong beam loading transients affecting the longitudinal bunch position and bunch length. In this paper, conceptual design of the RF system for the CLIC damping ring is presented. Baseline and several alternatives are discussed and the corresponding requirements for the cavities and the RF power sources are presented in order to meet stringent tolerances on the bunch-to-bunch phase and bunch length variations.

TUPPR027

Study of Multipolar RF Kicks from the Main Deflecting Mode in Compact Crab Cavities for LHC

multipole, dipole, simulation, coupling

1873

A. Grudiev, J. Barranco, R. Calaga, R. De Maria, M. Giovannozzi, R. Tomás
CERN, Geneva, Switzerland

A crab cavity system is under design in the frame work of the High Luminosity LHC project. Due to transverse space constraints on one hand and the RF frequency requirements on the other hand, the design of the crab cavities has to be compact. This results in the crab cavity shape being far from axially symmetric and, as a consequence, higher order multipolar components of the main deflecting mode are non-zero. In this paper, multipolar RF kicks from the main deflecting mode have been calculated in the compact crab cavities for LHC. They are compared to the multipolar error in magnetic elements of LHC. The influence of the RF kicks on the beam dynamics has been investigated and possible acceptable tolerances are presented.

TUPPR032

Beam Stability at CTF3

feedback, klystron, pick-up, linac

1888

T. Persson, P.K. Skowroński
CERN, Geneva, Switzerland

The two beam acceleration tested in CTF3 imposes very tight tolerances on the drive beam stability. A description of the specialized monitoring tool developed to identify the drifts and jitter in the machine is presented. It compares all the relevant signals in an on-line manner for helping the operator to identify drifts or to log data for off-line analysis. The main sources for the drifts of the drive beam were identified and their causes are described. Feedbacks applied to the RF were implemented to reduce the effects. It works by changing the waveform for the pulse compression to compensate for the drifts.

TUPPR037

Simulations of Higher Order Modes in the ACC39 Module of FLASH

HOM, dipole, higher-order-mode, simulation

1900

I.R.R. Shinton, R.M. Jones, P. Zhang
UMAN, Manchester, United Kingdom
Z. Li
SLAC, Menlo Park, California, USA

This study is primarily focused on the dipole component of the multiband expansion of the wakefield, with the emphasis being on the development of a HOM-based BPM system for ACC39 currently installed and in operation at FLASH and due to be installed at XFEL . Coupled inter-cavity modes are simulated together with a limited band of trapped modes. A suite of finite element computer codes (including HFSS and ACE3P) and globalised scattering matrix calculations (GSM) are used to investigate the modes in these cavities. In this way the nature of the multi-cavity nature of these modules is investigated with implications for a HOM-based BPM system and direct comparison to experimental results.

TUPPR045

Multi-cell VEP Results: High Voltage, High Q, and Localized Temperature Analysis

radiation, SRF, controls, monitoring

1918

F. Furuta, B. Elmore
Cornell University, Ithaca, New York, USA
A.C. Crawford
Fermilab, Batavia, USA
G.M. Ge, G.H. Hoffstaetter, M. Liepe
CLASSE, Ithaca, New York, USA

We are developing Vertical Electro Polishing (VEP) system for niobium superconducting RF cavity at Cornell University. VEP has been successfully applied on different cell shapes (TESLA and Re-entrant), and single and multi-cell cavities. VEP achieved high gradient of 39MV/m with TESLA shape single cell and of 36MV/m with TESLA shape 9-cell, respectively. Preliminary results of R&D on VEPed cavities show removal dependence on cavity performance. Temperature oscillation asymmetry was also found during the VEP process. We will report these recent results and further R&D plan of Cornell VEP.

TUPPR049

An X-band Standing Wave Dielectric Loaded Accelerating Structure

multipactoring, coupling, simulation, resonance

1927

C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow
Euclid TechLabs, LLC, Solon, Ohio, USA
S.H. Gold
NRL, Washington, DC, USA
S. Kazakov
Fermilab, Batavia, USA
R. Konecny
ANL, Argonne, USA

Funding: DOE SBIR Phase I grant #DE-SC0006303
An 11.4 GHz standing wave dielectric loaded accelerating structure was recently developed. We expect to achieve a 120 MV/m gradient powered by a 10 MW 200 ns rf pulse from the X-band Magnicon at the Naval Research Laboratory. The structure uses on-axis rf coupling, which helps to localize the maximum EM fields within the dielectric region. Bench testing shows excellent agreement with the simulation results. The high power rf test is scheduled for January 2012.

TUPPR050

Design and simulation of Prebuncher for S-band Traveling Linear Accelerator

coupling, simulation, electron, linac

1930

S. Zarei, F. AbbasiDavani, S. Ahmadiannamini, F. Ghasemi
sbu, Tehran, Iran
H. Shaker
IPM, Tehran, Iran

An S-band Traveling wave linear accelerator with an RF input peak power level up to 2.5 MW, for accelerating 1 mA beam of electron up to 15 MeV, is under construction in Iran. This article presents design procedure of a prebuncher for this accelerator. One standing-cavity type prebuncher is required for bunching electron beam for this accelerator. The intended prebuncher is driven by a coaxial line at 2 kW and operated at the same frequency of the other parts of the accelerator. The magnetic coupling applied has been applied for power coupling to the prebuncher cavity. The optimum dimensions of the prebuncher were obtained by using 2D and 3D electromagnetic codes in the frequency domain. Prebuncher cavity consists of a copper body and coupling loop feed.

TUPPR051

Development of L-Band Positron Capture Accelerating Structure with Kanthal-coated Collinear Load for SuperKEKB

solenoid, damping, target, positron

1933

F. Miyahara, Y. Arakida, T. Higo, N. Iida, K. Kakihara, T. Kamitani, S. Matsumoto
KEK, Ibaraki, Japan
L. Lilje
DESY, Hamburg, Germany

In order to achieve a luminosity of 8x10³⁵ cm^-2 s^-1, the SuperKEKB injector is required to provide both e⁺e⁻ beams higher in intensity by a factor 4-5 than those for KEKB, and with a low emittance of about 20 um. A damping ring is used to fulfill this low emittance requirement for e⁺, but the intensity increase is realized by a larger yield from the conversion target to the damping ring. To this end, the L-band capture system is adopted to increase the transverse and longitudinal acceptance. The capture section consists of a Tungsten conversion target with flux concentrator followed by two L-band 2.4m-long accelerating structures and continuing to the large aperture S-band 2m-long ones. The L-band frequency of 1.3 GHz, 5/11 times S-band one, was adopted to suppress the satellite bunches in the S-band system. This L-band system is surrounded by a solenoid magnet producing 4kG on axis. To compose compact magnet system, the output coupler of the L-band accelerating structure is replaced by the Kanthal coated collinear load section. In this paper, we will discuss the design of the accelerating structure and present the studies of Kanthal layer coated on copper.

TUPPR055

Upgrading the CEBAF Injector with a New Booster, Higher Voltage Gun, and Higher Final Energy

booster, gun, cryomodule, coupling

1945

R. Kazimi, A. Freyberger, F.E. Hannon, A.S. Hofler, A. Hutton
JLAB, Newport News, Virginia, USA

Funding: Authored by JSA, LLC under U.S. DOE Contract DE-AC05- 06OR23177. The U.S. Govt. retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this for U.S. Govt. purposes.
The CEBAF accelerator at Jefferson Lab will be upgraded from 6 GeV to 12 GeV in the next few years. To meet the requirement of the new machine and also to take the opportunity to improve the beam quality, the CEBAF injector will be upgraded with a higher voltage gun, a new booster, and a new accelerating RF module. The CEBAF injector creates and accelerates three beams at different currents simultaneously. The beams are interleaved, each at one third of RF frequency, traveling through the same beam line. The higher voltage gun will lower the space charge effects making it easier to operate at different current with the same setup. The new booster with optimized beam dynamics will complete the bunching process and provides initial acceleration matched to the new gun voltage. Using our latest SRF design, the new booster has significantly lower XY coupling effects that should improve our beam setup and operation for the highly sensitive parity experiments scheduled for the CEBAF’s future. Finally, the new accelerating RF module will roughly double the injector final energy to match the rest of the 12 GeV accelerator. In this paper we will provide more detail about this upgrade.

TUPPR076

The LHeC Project Development Beyond 2012

electron, linac, collider, dipole

1999

F. Zimmermann, O.S. Brüning
CERN, Geneva, Switzerland
M. Klein
The University of Liverpool, Liverpool, United Kingdom

The LHeC study group is finalizing a Conceptual Design Report for publication early in 2012. This paper discusses the next steps required for developing a Technical Design Report and highlights the R&D developments, test facilities and implementation studies that need to be addressed over the coming years. Particular emphasize will be given to similarities with other ongoing accelerator and detector studies, and to a discussion of possible international collaboration efforts.

TUPPR084

HOM Damping and Multipacting Analysis of the Quarter-wave Crab Cavity

HOM, damping, simulation, electron

2020

Q. Wu, S.A. Belomestnykh, I. Ben-Zvi
BNL, Upton, Long Island, New York, USA
R. Calaga
CERN, Geneva, Switzerland

The Quarter-Wave Crab Cavity design has been analyzed further to accommodate LHC requirements. The goal for the design is to provide strong deflecting voltage to the proton bunches at the IP, while keeping the effective length as short as possible. We will evaluate the Higher Order Mode damping with two magnetic coupling dampers of 90 degrees apart. In this paper, we also show possible multipacting locations which are simulated by 3D code.

WEYB03

High Average Power UV Free Electron Laser Experiments at JLAB

FEL, wiggler, linac, electron

2111

D. Douglas, S.V. Benson, P. Evtushenko, J.G. Gubeli, C. Hernandez-Garcia, R.A. Legg, G. Neil, T. Powers, M.D. Shinn, C. Tennant, G.P. Williams
JLAB, Newport News, Virginia, USA

Funding: Authored by JSA LLC under US DOE Contract #DE-AC05-06OR23177. The U.S. Gov. retains non-exclusive, paid-up, irrevocable, world-wide license to publish/reproduce this manuscript for U.S. Gov. purposes.
Having produced 14 kW of average power at ~2 microns, JLAB has shifted its focus to the ultraviolet portion of the spectrum. This presentation will describe the JLab UV Demo FEL, present specifics of its driver ERL, and discuss the latest experimental results from FEL experiments and machine operations.

Slides WEYB03 [2.863 MB]

WEOBA03

Beam Tests of a High Pressure Gas-Filled Cavity for a Muon Collider

electron, ion, pick-up, collider

2131

T.A. Schwarz, M.A. Leonova, A. Moretti, M. Popovic, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, USA
M. Chung
Handong Global University, Pohang, Republic of Korea
B.T. Freemire, P.M. Hanlet, Y. Torun
IIT, Chicago, Illinois, USA
R.P. Johnson
Muons, Inc, Batavia, USA

Funding: US DOE under contract DE-AC02-07CH11359.
One of the greatest challenges in constructing a Muon Collider is cooling the hot muons into a focused beam after their production. Because the beam must be cooled quickly before the muons decay, compact cooling designs require high gradient cavities inside strong magnetic fields. Unfortunately, due to focused field emission, an external magnetic field degrades the performance of the cavity below what is required for a muon collider. High-pressure gas inside the cavity has been proposed to both mitigate this effect, as well as serve as an absorber for transversely cooling the muon beam. A prototype of a high pressure gas-filled cavity is currently being studied at the Muon Test Area at Fermilab. The experimental setup as well as several measurements of the physics and performance of the apparatus while operating in a 400-MeV proton beam will be discussed.

Slides WEOBA03 [6.912 MB]

WEOAB03

An Update on a Superconducting Photonic Band Gap Structure Resonator Experiment

SRF, HOM, wakefield, niobium

2140

E.I. Simakov, W.B. Haynes, M.A. Madrid, F.P. Romero, T. Tajima, W.M. Tuzel
LANL, Los Alamos, New Mexico, USA
C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA

Funding: This work is supported by the U.S. Department of Energy (DOE) Office of Science Early Career Research Program.
We present an update on the 2.1 GHz superconducting rf (SRF) photonic band gap (PBG) resonator experiment in Los Alamos. The SRF PBG cell was designed to operate at 2.1 GHz. PBG cells have great potential for outcoupling long-range wakefields in SRF accelerator structures without affecting the fundamental accelerating mode. Using PBG structures in superconducting particle accelerators will allow operation at higher frequencies and moving forward to significantly higher beam luminosities thus leading towards a completely new generation of colliders for high energy physics. However, the technology of fabrication of PBG accelerator cells from niobium has not been well developed to date. Here we report the results of our efforts to fabricate a 2.1 GHz PBG cell and to test it at high gradients in a liquid helium bath at the temperature of 2 Kelvin. The high gradient performance of the cell will be evaluated and the results will be compared to simulations with the CST Microwave Studio.

Slides WEOAB03 [2.061 MB]

WEOBB02

Refraction Contrast Imaging via Laser-Compton X-Ray Using Optical Storage Cavity

laser, electron, photon, linac

2146

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

We have been developing a pulsed-laser storage technique in a super-cavity for a 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 a multi-pulse x-rays through the laser-Compton scattering. Then, we performed a X-ray imaging via laser-Compton X-ray. The images have edge enhancement by refraction contrast because the X-ray source spot size was small enough. This is one of the evidences that laser-Compton X-ray is high quality. Our laser-Compton experimental setup, the results of X-ray imaging and future prospective will be presented at the conference.

Slides WEOBB02 [4.393 MB]

WEEPPB004

Status of the APEX Project at LBNL

gun, cathode, laser, electron

2173

F. Sannibale, B.J. Bailey, K.M. Baptiste, J.M. Byrd, C.W. Cork, J.N. Corlett, S. De Santis, L.R. Doolittle, J.A. Doyle, P. Emma, J. Feng, D. Filippetto, G. Huang, H. Huang, T.D. Kramasz, S. Kwiatkowski, W.E. Norum, H.A. Padmore, C. F. Papadopoulos, G.C. Pappas, G.J. Portmann, J. Qiang, D.G. Quintas, J.W. Staples, T. Vecchione, M. Venturini, M. Vinco, W. Wan, R.P. Wells, M.S. Zolotorev, F.A. Zucca
LBNL, Berkeley, California, USA
M. J. Messerly, M.A. Prantil
LLNL, Livermore, California, USA
C.M. Pogue
NPS, Monterey, California, USA

Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
The Advanced Photo-injector Experiment (APEX) at the Lawrence Berkeley National Laboratory is focused on the development of a high-brightness high-repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept gun, utilizing a normal conducting 186 MHz RF cavity operating in cw mode in conjunction with high quantum efficiency photocathodes capable of delivering the required repetition rates with available laser technology. The APEX activities are staged in 3 main phases. In Phases 0 and I, the gun will be tested at its nominal energy of 750 keV and several different photocathodes are tested at full repetition rate. In Phase II, a pulsed linac will be added for accelerating the beam at several tens of MeV to reduce space charge effects and measure the high-brightness performance of the gun when integrated in an injector scheme. At Phase II energies, the radiation shielding configuration of APEX limits the repetition rate to a maximum of several Hz. Phase 0 is under commissioning, Phase I under installation, and initial activities for Phase II are underway. This paper presents an update on the status of these activities.

WEEPPB008

HOM Coupler Optimisation for the Superconducting RF Cavities in ESS

HOM, neutron, target, damping

2182

R. Ainsworth
Royal Holloway, University of London, Surrey, United Kingdom
R. Calaga
CERN, Geneva, Switzerland
S. Molloy
ESS, Lund, Sweden

The European Spallation Source (ESS) will be the world’s most powerful next generation neutron source. It consists of a linear accelerator, target, and instruments for neutron experiments. The linac is designed to accelerate protons to a final energy of 2.5 GeV , with an average design beam power of 5 MW, for collision with a target used to produce a high neutron flux. A section of the linac will contain Superconducting RF (SCRF) cavities designed to resonate at 704 MHz. Dangerous beam induced modes in these cavities may make the beam unstable and increase the cryogenic load and so couplers are usually installed to provide damping. Previous studies have shown potential designs are susceptible to multipacting, a resonant process which can absorb RF power and lead to heating effects. This paper will show how a coupler suffering from multipacting has been redesigned to limit this effect. Optimisation of the RF damping is also discussed.

WEEPPB010

RF Modeling Using Parallel Codes ACE3P for the 400-MHz Parallel-Bar/Ridged-Waveguide Compact Crab Cavity for the LHC HiLumi Upgrade

damping, HOM, impedance, dipole

2185

Z. Li, L. Ge
SLAC, Menlo Park, California, USA
J.R. Delayen, S.D. Silva
ODU, Norfolk, Virginia, USA

Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515.
Schemes utilizing crab cavities to achieve head-on beam-beam collisions were proposed for the LHC HiLumi upgrade. These crabbing schemes require that the crab cavities be compact in order to fit into the tight spacing available in the existing LHC beamlines at the location where the crab cavities will be installed. Under the support of US LARP program, Old Dominion University and SLAC have joint efforts to develop a 400-MHz compact superconducting crab cavity to meet the HiLumi upgrade requirements. In this paper, we will present the RF modeling and analysis of a parallel-bar/ridged-waveguide shaped 400-MHz compact cavity design that can be used for both the horizontal and vertical crabbing schemes. We will also present schemes for HOM damping and multipacting analysis for such a design.

WEEPPB015

Temperature Dependence of the Superheating Field: DC and RF Critical Fields

niobium, electron, superconductivity, SRF

2197

N.R.A. Valles, M. Liepe
CLASSE, Ithaca, New York, USA

The superheating field is a metastable state at which the Meissner state persists at fields higher than would be predicted from steady-state energy considerations. Previous work demonstrated that a phenomenological approach based on the RF superheating field scaling near the critical temperature is also consistent with low temperature results. This work expands upon the RF results by measuring the DC superheating field, and comparing it to RF results and theoretical predictions.

WEPPC002

Impact of Trapped Flux and Thermal Gradients on the SRF Cavity Quality Factor

niobium, superconducting-cavity, SRF, controls

2203

O. Kugeler, J. Knobloch, J.M. Vogt
HZB, Berlin, Germany
S. Aull
CERN, Geneva, Switzerland

The obtained Q0 value of a superconducting niobium cavity is known to depend on various factors like the RRR of the Niobium material, crystallinity, chemical treatment history, the high-pressure rinsing process, or effectiveness of the magnetic shielding. We have observed that spatial thermal gradients over the cavity length during cool-down appear to contribute to a degradation of Q0. Measurements were performed in the Horizontal Bi-Cavity Test Facility (HoBiCaT) at HZB on TESLA type cavities as well as on disc- and rod-shaped niobium samples equipped with thermal, electrical and magnetic diagnostics. Possible explanations for the effect are discussed.

WEPPC003

Component Qualification and Final Assembly of the S-DALINAC Injector Upgrade Module

linac, SRF, niobium, shielding

2206

J. Conrad, R. Eichhorn, T. Kürzeder, A. Richter, S.T. Sievers
TU Darmstadt, Darmstadt, Germany

Funding: This work is supported by the DFG through SFB 634.
The injector of the S-DALINAC delivers currently electron beams of up to 10 MeV with a current of up to 60 μA. With the new cryostat-module an increase of both parameters, energies ranging to 14 MeV and currents up to 150 μA, are expected. For acceleration, the module houses two 20 cell elliptical niobium cavities which are used at a frequency of 3 GHz in liquid helium at 2 K. The RF power is delivered to the cavities through the different temperature stages by a WR-284 transition line which is connected to the resonator by a new waveguide-to-coax power coupler (being one of the major changes compared to the design of the existing module). We review on the design of the module and present the results of the first cool-down. Also, a report on additional new design features, e.g. piezo actuators for tuning at 2 K, and the production of the cavities will be given.

WEPPC004

PLM-Based Quality Assurance in the Series Production of the Superconducting Cavities for the European XFEL

background

2209

L. Hagge, J.A. Dammann, S. Eucker, J. Iversen, J. Kreutzkamp, W. Singer
DESY, Hamburg, Germany

This presentation describes the acceptance procedure in the series production of the superconducting cavities for the European XFEL. The cavities are produced by two manufacturers. To ensure they satisfy their performance requirements, the cavities have to pass more than 50 quality inspections, which are combined into four acceptance levels. Part of the inspections are done by the manufacturers, the remaining tests are conducted in a test facility at DESY. The inspections are recorded and processed based on DESY's Product Lifecycle Management (PLM) system, aka DESY EDMS. The DESY EDMS tracks all the individual cavities, keeps their entire production history, and associates all certificates and inspection results with the appropriate parts. The two manufacturers are integrated in the solution and can automatically and promptly upload inspections results to the DESY EDMS. The solution enables DESY to monitor the production progress and to ensure production quality.

WEPPC005

Parts Management during Fabrication at the European XFEL

controls, undulator, cryomodule, niobium

2212

L. Hagge, J.A. Dammann, S. Eucker, A. Herz, J. Kreutzkamp, D. Käfer, D. Szepielak, N. Welle
DESY, Hamburg, Germany

This presentation describes policies and methods for parts management during fabrication at the European XFEL. The objective is to provide procedures for reliably gathering, recording, processing and archiving the complete mandatory fabrication information. The solution is a foundation for conducting Quality Assurance and Quality Control (QA/QC), as it ensures that acceptance tests are recorded, signed-off and followed-up in a reliable and orderly way. It achieves compliance with legal regulations in certain areas. One example is the pressurized equipment directive (PED), which for certain (parts of) equipment requires that the complete fabrication and usage history is tracked throughout the entire lifespan of the XFEL facility. In addition, the solution provides a basis for building the necessary documentation for later installation, operation and maintenance activities. The solution is established in the series production of several accelerator components. It uses DESY’s Engineering Data Management System as central collaboration and documentation platform.

WEPPC006

CW and LP Operation Test of XFEL-Like Cryomodule

HOM, cryomodule, cryogenics, feedback

2215

J.K. Sekutowicz, V. Ayvazyan, M. Ebert, J. Eschke, A. Gössel, D. Kostin, I.M. Kudla, W. Merz, F. Mittag, R. Onken
DESY, Hamburg, Germany
W. Cichalewski, W. Jałmużna, K.P. Przygoda
TUL-DMCS, Łódź, Poland
K. Czuba, L. Zembala
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
J. Szewiński
The Andrzej Soltan Institute for Nuclear Studies, Centre Świerk, Świerk/Otwock, Poland

A continuous improvement in the performance of superconducting TESLA cavities will make possible, from the cryogenic point of view, operation of the XFEL linac in continuous wave (cw) mode at gradients up to 7.5 MV/m and in long pulse (lp) mode up to nominal gradient of 23.4 MV/m. Each of these new operation modes will offer an additional flexibility in time structure of the photon beam, and therefore will allow for more experiments and in some cases less demanding and less expensive equipment. In this contribution we discuss results of the first RF test of these new types of operation with a XFEL-like cryomodule.

WEPPC007

Image Processing for Characterization of Surfaces of Superconducting RF Cavities

superconductivity, LabView, linear-collider, collider

2218

M. Wenskat, S. Aderhold, E. Elsen, S. Karstensen, F. Schlander, L. Steder
DESY, Hamburg, Germany

Funding: ILC HiGrade
Optical inspection of finished Nb superconducting RF cavities has worldwide been established as an important tool for identification of field limiting surface features. Single defects in a single cell of a 9-cell cavity may severely constrain the maximum gradient while the micro-structure in the vicinity of a welding seam could affect the quench behavior. DESY has automated the imaging of critical cavity surface areas, in particular those of high magnetic field. With resolution of ~10 μm2 the information volume is large and the systematic examination becomes a necessity. The development of image processing algorithms has been started with two goals: automatic characterization of cavity surface properties and defect detection. The former results aid the quality assessment of cavities after manufacture; the latter serves to push the gradient performance. The status and prospects of the image processing for the European XFEL and ILC will be presented.

WEPPC008

FNAL Project X Conical Half-Wave Resonator Design

simulation, cryomodule, resonance, proton

2221

E.N. Zaplatin
FZJ, Jülich, Germany
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: This work is supported by the DOE SBIR Program, contract # DE-SC0006302.
A high-intensity proton accelerator complex proposed at Fermi National Accelerator Laboratory (Project X) should provide beam for a variety of physics projects. The superconducting resonators of different types will be used as accelerating structures. Here we describe the design of conical Half-Wave Resonator that is considered as an option for a first accelerating cavity for β=v/c=0.11 with the resonance frequency 162.5 MHz. A careful study of the fields in the cavity has been carried out in order to optimize the electromagnetic parameters of the structure (peak fields, quality factor, dissipation power). An intensive investigations were provided of the liquid helium vessel design to minimize cavity frequency shifts from the external loads. Different tuning schemes have been studied to secure a frequency tuning range to cope with fabrication tolerances. The paper reports results of numerical simulations of the cavity shape optimization and structural analyses. The detailed developments of the structure using numerical coupled analyses allowed to minimize the level of expected microphonics in cavity.

WEPPC009

Status of the European XFEL 3.9 GHz system

status, linac, diagnostics, HOM

2224

P. Pierini, A. Bosotti, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
E.R. Harms
Fermilab, Batavia, USA
C. Pagani
UniversitÃ degli Studi di Milano & INFN, Segrate, Italy
E. Vogel
DESY, Hamburg, Germany

The injector of the European XFEL will use a third harmonic RF system at 3.9 GHz to flatten the RF curvature after the first accelerating module before the first bunch compression stage. This paper presents qualification tests of the prototype cavities and the status of the activities for the realization of the third harmonic section of the European XFEL towards its commissioning due in 2014.

WEPPC011

Vertical Test Results for ERL 9-cell Cavities for Compact ERL Project

linac, cryomodule, radiation, HOM

2227

K. Umemori, T. Furuya, H. Sakai, M. Satoh, K. Shinoe
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

The Compact ERL project, which is a test facility of ERL, is ongoing in Japan. At the first step of this project, main linac cavities accelerate electron beams by 30 MV. Two 9-cell cavities were fabricated for main linac cryomodule, under High Pressure Gas Safety Code in Japan. A series of surface treatments, such as annealing, pre-tuning, electro-polishing (EP), degreasing, high pressure rinsing by ultra-pure water, cavity assembly and baking, were applied for the cavities. For the final EP, current density was selected to be relatively low. Vertical tests were performed for both cavities. Their field successfully reached to 25 MV/m, without any field limitation. The Q-values were more than 1x10¹⁰, even at 20 MV/m. Field emission on-sets were to be 14 and 22 MV/m, for each cavities. Both cavities satisfied requirements for ERL main linac cavity. Details of vertical tests, with X-ray and temperature mapping data, are shown, in this paper. These cavities will be mounted with titanium He jackets, assembled and installed into a cryomodule.

WEPPC012

High Power Tests of CW Input Couplers for cERL Injector Cryomodule

cryomodule, vacuum, linac, impedance

2230

E. Kako, S. Noguchi, T. Shishido, K. Watanabe, Y. Yamamoto
KEK, Ibaraki, Japan

High power tests of a pair of the prototype input couplers were performed by using a newly developed 300 kW CW klystron. The input couplers were successfully processed up to 100 kW in a pulsed operation with a duty of 10% and 50 kW in a CW operation for 30 minutes. The conditioning was limited by excessive heating at bellows of an inner conductor at a coaxial line locating between a coaxial RF window and a doorknob-type transition. Improvement of a sufficient cooling at the inner conductor is necessary to achieve the required input RF power of 170 kW in a CW operation. Six input couplers to be installed in the injector cryomodule for the cERL project were completed, and they are under preparation for conditioning at a high power test stand.

WEPPC013

Progress of High Gradient Performance in STF 9-cell Cavities at KEK

accelerating-gradient, status, laser, HOM

2233

Y. Yamamoto, H. Hayano, E. Kako, S. Noguchi, T. Shishido, K. Watanabe
KEK, Ibaraki, Japan

Vertical tests for ILC have been carried out since 2008 at KEK-STF. Measured cavities are from MHI#5 to MHI#22 (not yet for MHI#18-#22 at the end of November 2011), and MHI#12, #13 and #17 reached the ILC specification of 0.8x10¹⁰ at 35MV/m. The MHI cavity was added into the “qualified vendor” for the cavity yield. These three cavities (#12, #13 and #17) had no defect on every EBW seam of equator, iris and beampipe. On the other hand, the other cavities had a few or several defects on EBW seam. Especially, defect on the EBW seam of the equator is the worst case, and cavity performance is limited “certainly”. MHI#10, #15 and #16 cavities were limited by this kind of defect. As for iris region, MHI#14 had large defect at the iris between cell #8 and #9, and the performance was limited by the heavy field emission with “explosive event”. However, after the locally mechanical grind for this defect, the cavity performance was drastically improved with no field emission at 37MV/m. In this paper, the recent progress of the cavity performance at KEK-STF will be reported with the “detailed” defect analysis.

WEPPC014

Construction and Beam Operation of Capture Cryomodule for Quantum Beam Experiments at KEK-STF

cryomodule, controls, radiation, status

2236

Y. Yamamoto
KEK, Ibaraki, Japan

Construction of capture cryomodule for Quantum Beam Project has started since September, and will be finished by the end of December in 2011 at KEK-STF. Two MHI cavities (MHI-12, -13), which reached ILC specification (0.8x10¹⁰ at 35MV/m) at the vertical test, were installed into a short cryomodule with improved input couplers. Slide-Jack tuner was attached at different position (center or end of helium jacket) for each cavity same as S1-Global. From January 2012, this cryomodule will be cooled down to 2K, and the high power test will be started including check of the cavity/coupler/tuner performance, LFD measurement, LFD compensation by Piezo, dynamic loss measurement and so on. From March, the beam operation with the beam current of 10mA and the maximum beam energy of 40MeV, will be started to generate x-rays by collision between electron beam and laser. At this stage, two cavities will be operated at the lower gradient of 15-20MV/m, and the stable operation is crucial. In this report, the test results of various performances at the Quantum Beam Project will be presented in detail.

WEPPC015

Construction of Injector Cryomodule for cERL at KEK

cryomodule, HOM, pick-up, linac

2239

E. Kako, S. Noguchi, T. Shishido, K. Watanabe, Y. Yamamoto
KEK, Ibaraki, Japan

The cERL injector cryomodule includes three 2-cell cavities, and each cavity has 2 input couplers and 5 HOM couplers. Three 2-cell cavities for cERL has already completed. Vertical test of the three cavities has been going on. The first cavity have achieved Eacc of 30 MV/m. Vertical tests will be carried out twice in each cavity, till the end of December, 2011. Six cw input couplers for cERL has already completed. RF processing at the high-power test stand with a cw 300kW-klystron will be carried out in Jan.-Feb., 2012. After the cavities were covered with a He jacket, assembly of the cERL injector cryomodule will be carried out in March-April, 2012. The first cool-down of the cryomodule is scheduled in June 2012.

WEPPC018

Design of a Spoke Cavity for RIKEN RI-beam Factory

vacuum, ion, simulation, heavy-ion

2245

L. Lu
RIKEN, Saitama, Japan
O. Kamigaito, N. Sakamoto, K. Suda, K. Yamada
RIKEN Nishina Center, Wako, Japan

Designs of a CW superconducting rebuncher tri-spoke cavity for uranium beams with β = 0.303 has been studied. The estimated peak voltage is rather high as 3 mega-voltages (MV). The resonator frequency was chose as 219MHz which is 12 times of the foundational frequency. The buncher would be settled in a location between two booster cyclotrons (RRC: K = 540MeV, fRC: K = 570 MeV). In this cavity design, a flat E field distribution on beam axis was designed based on the Microwave Studio (MWS) simulations. The cavity parameters, detail designs and some simulated results will be reported in this paper.

WEPPC021

Development of Superconducting Radio Frequency Cavities at SINAP

niobium, superconducting-cavity, electron, HOM

2248

J.F. Liu, H.T. Hou, C.W. Lu, C. Luo, Z.Y. Ma, D.Q. Mao, J. Shi, Zh.G. Zhang, S.J. Zhao, X. Zheng
SINAP, Shanghai, People's Republic of China
Z.Q. Feng, Z. Li, J.F. Liu, Y.L. Wei, K. Xu, Y.B. Zhao
Shanghai KEY Laboratory of Cryogenics & Superconducting RF Technology, Shanghai, People's Republic of China
H. Yu
Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China

This paper presents the development of superconducting radio frequency cavities at Shanghai Institute of Applied Physics (SINAP) mainly focused on the 500MHz band. Firstly, Two KEKB type 500MHz single cell niobium cavities have been fabricated and one of them has been vertical tested successfully in 2010. The highest accelerating gradient of the fabricated cavity higher than 10MV/m was obtained while the quality factor was better than 4·10⁸ at 4.2K. Secondly, a new type of 500MHz single cell cavity has been designed which adopts the fluted beam pipe for higher order modes propagation and a coaxial type high power input coupler. Thirdly, a 500MHz 5-cell superconducting cavity with large aperture, enlarged beam pipe for HOM propagation and high r/Q value has been optimized which can be a candidate cavity for high current FEL and ERL.

WEPPC022

Elliptical SRF Cavity Design for PEFP Extension

linac, SRF, coupling, proton

2251

H.S. Kim, Y.-S. Cho, J.-H. Jang, H.-J. Kwon
KAERI, Daejon, Republic of Korea

Funding: * This work is supported by the Ministry of Education, Science and Technology of the Korean Government.
To increase the beam energy up to 1 GeV by extending a PEFP 100-MeV proton linac, a study on the superconducting RF linac is underway. SRF technology is chosen due to its operational flexibility and lower beam loss, as well as its high accelerating performance and low operating cost. Preliminary study on the beam dynamics shows that two types of cavity with geometrical beta of 0.50 and 0.74 can cover the entire energy range from 100 MeV to 1 GeV. Assuming the achievable peak surface electric field to be 30 MV/m and 35 MV/m for medium and high beta cavity, respectively, we designed the six-cell elliptical cavities by optimizing the cavity parameters such as peak field ratio, inter-cell coupling and r/Q through the geometrical parameter sweep. The details of the SRF cavity design for PEFP extension will be presented.

WEPPC024

Preliminary Test of Superconducting RF Cavities for PLS-II

SRF, cryomodule, vacuum, cryogenics

2257

Y.U. Sohn, M.-H. Chun, J.Y. Huang, Y.D. Joo, H.-S. Kang, H.-G. Kim, S.H. Nam, C.D. Park, H.J. Park, I.S. Park, I.H. Yu
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This project is supported by the Korea Ministry of Science and Technology.
The main part of the Installation for the PLS-II upgrade was finished in June and is on the way to user operation through elaborate commissioning. Up to now, the achievement is 150 mA beam current at 3 GeV with multi-bunch mode with 5 normal conducting cavities which served in the PLS before. After installation of 2 SRF cavities in the summer of 2012, the PLS-II will have 300 mA beam current with 20 IDs by 2 superconducting RF cavities until July, 2014. Finally, one more superconducting cavity will be added in August, 2014, and beam current will rise to 400 mA. The two SRF cavities are under test and conditioning. The two main subsystems, SRF cavities and ceramic windows were tested independently to confirm their performance. Each cavity recorded its accelerating voltage as 3.27 MV and 3.24 MV at 4.2K, respectively. Two RF windows also passed their specification, 300 kW CW traveling wave and 150 kW CW standing wave. The preliminary tests of SRF cryomodules are reported in the presentation.

WEPPC027

A Quarter Wave Design for Crab Crossing in the LHC

HOM, acceleration, high-voltage, higher-order-mode

2260

R. Calaga
CERN, Geneva, Switzerland
S.A. Belomestnykh, I. Ben-Zvi, Q. Wu
BNL, Upton, Long Island, New York, USA

Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP).
The aperture constraints of the LHC interaction region and the alternating crossing schemes at two collision points calls for a superconducting deflecting cavity with very compact dimensions at low frequencies for the purpose of crab crossing. A new concept of using a superconducting 1/4-wave design, ideally suited to address the LHC constraints at 400 MHz, is proposed. The optimized RF cavity design and associated advantages of using a 1/4 wave resonator are presented. Aspects related to higher order mode damping, multipacting and frequency tuning are also addressed.

WEPPC028

Slim Elliptical Cavity at 800 MHz for Local Crab Crossing

coupling, damping, impedance, HOM

2263

L. Ficcadenti, J. Tückmantel
CERN, Geneva, Switzerland

A slim highly eccentric elliptical Crab cavity with vertical deflection at 800 MHz, compatible to beam line distances everywhere in the LHC ring, was designed. It is a good fall-back solution in case of problems with new compact 400 MHz designs. Simulated RF characteristics of the delfecting mode, HOM spectra and damping, tuning and multipacting effects are presented. First the most simple HOM coupling system was investigated. The rejection of the working mode was not sufficient and a notch filter was added. Results of both cases will be presented.

WEPPC029

Design and Development of an Octopus Thermometric System for the 704 MHz Single-cell SPL Cavity at CERN

LabView, SRF, factory, proton

2266

K.C. Liao, L. Arnaudon, O. Brunner, E. Ciapala, D.C. Glenat, W. Weingarten
CERN, Geneva, Switzerland

The octopus thermometric system is designed for the 704 MHz superconducting proton linac (SPL) cavity to detect hot spots and X-rays caused by normal conducting defects and the impact of emission electrons. This system features an octopus body and tentacle structure for good contact with the cavity and easy assembly, a multiplexing circuit with integrated microprocessor for efficient readout and a high density temperature sensor arrangement in order to complete a high resolution temperature and X-ray map. The first prototype is being manufactured and investigations are undergoing for further development.

Poster WEPPC029 [1.715 MB]

WEPPC030

Second Sound Measurement Using SMD Resistors to Simulate Quench Locations on the 704 MHz Single-cell Cavity at CERN

simulation, cryogenics, linac, quadrupole

2269

K.C. Liao, O. Brunner, E. Ciapala, T. Junginger, W. Weingarten
CERN, Geneva, Switzerland

Oscillating superleak transducers (OSTs) containing a flexible porous membrane are widely used to detect the so-called second sound temperature wave when a quench event occurs in a superconducting RF cavity. In principle, from the measured speed of this wave and the travel time between the quench event and several OSTs, the location of the quench sites can be derived by triangulation. Second sound behavior has been simulated though different surface mount (SMD) resistors setups on a Superconducting Proton Linac (SPL) test cavity, to help understand the underlying physics and improve quench localisation. Experiments are described that have been conducted to search for explanation of heat transfer mechanism during cavity quench that causes contradictory triangulation results.

Poster WEPPC030 [1.473 MB]

WEPPC031

Completed Assembly of the Daresbury International ERL Cryomodule and its Implementation on ALICE

cryomodule, HOM, cryogenics, controls

2272

P.A. McIntosh, M.A. Cordwell, P.A. Corlett, P. Davies, E. Frangleton, P. Goudket, K.J. Middleman, S.M. Pattalwar, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA
A. Büchner, F.G. Gabriel, P. Michel
HZDR, Dresden, Germany
J.N. Corlett, D. Li, S.M. Lidia
LBNL, Berkeley, California, USA
G.H. Hoffstaetter, M. Liepe, H. Padamsee, P. Quigley, J. Sears, V.D. Shemelin, V. Veshcherevich
CLASSE, Ithaca, New York, USA
T.J. Jones, J. Strachan
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
R.E. Laxdal
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
D. Proch, J.K. Sekutowicz
DESY, Hamburg, Germany
T.I. Smith
Stanford University, Stanford, California, USA

The completion of an optimised SRF cryomodule for application on ERL accelerators has now culminated with the successful assembly of an integrated cryomodule, following an intensive 5 years of development evolution. The cryomodule, which incorporates 2 x 7-cell 1.3 GHz accelerating structures, 3 separate layers of magnetic shielding, fully adjustable & high power input couplers and fast piezo tuners, has been installed on the ALICE ERL facility at Daresbury Laboratory. It is intended that this will permit operational optimisation for maximised efficiency demonstration, through increased Qext adjustment whilst retaining both effective energy recovery and IR-FEL lasing. The collaborative design processes employed in completing this new cryomodule development are explained, along with the assembly and implementation procedures used to facilitate its successful installation on the ALICE ERL facility.

WEPPC032

Analysis of the Four Rod Crab Cavity for HL-LHC

multipactoring, simulation, niobium, luminosity

2275

B.D.S. Hall, P.K. Ambattu, G. Burt, D. Doherty, C. Lingwood
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
P. Goudket
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The Hi-Lumi Upgrade to the LHC will utilise crab cavities to increase the peak luminosity and provide luminosity levelling at the increased crossing angle. A transversely compact design is required to fit within the limited space between opposing beamlines. In this paper a four rod TEM deflecting cavity (4RCC) is shown to be suitable for LHC. The variation of the deflecting voltage with radial offset has been minimised by careful design and an aluminium prototype has been constructed and beadpull measurements are compared to simulations. Multipacting simulations have been performed on the cavity geometry and it is predicted that the growth rate is less than unity for a clean surface. Pressure variations in the LHe can result in deformation of the complex shape which will alter the resonant frequency. Mechanical simulations have also been performed to assess the sensitivity of the frequency to pressure. In order to reduce the impact of these cavities on the LHC beam low impedance is required for the HOMs as well as the fundamental monopole mode. The couplers for the 4RCC cavity have been optimised to provide effective damping of these modes while rejecting the operating mode.

WEPPC035

Design and Construction of a High-Power RF Coupler for PXIE

cryomodule, vacuum, linac, simulation

2284

M.P. Kelly, Z.A. Conway, M. Kedzie, S.V. Kutsaev, P.N. Ostroumov
ANL, Argonne, USA
S. Nagaitsev
Fermilab, Batavia, USA

A power coupler has been designed and built at Argonne National Laboratory for use with the Project X Injector Experiment (PXIE) 162.5 MHz superconducting (SC) half-wave cavities. The 50 Ω coaxial capacitive coupler will be required to operate CW with up to 10 kW of forward power under any condition for the reflected power. A key feature is a moveable copper plated stainless steel bellows which will permit up to 3 cm of axial stroke and adjustment of Qext by roughly one order of magnitude in the range of 10^-5 to 10^-6. The mechanical and vacuum design will include two ceramic windows, one operating at room temperature and another at 70 Kelvin. The two window design allows the portion of the coupler assembled to the SC cavity in the clean room to be compact and readily cleanable. We present other design features including thermal intercepts to provide a large margin for RF heating and a mechanical guide assembly to operate cold and under vacuum with high reliability.

WEPPC036

Electromagnetic Design of 15 kW CW RF Input Coupler

simulation, cryomodule, linac, vacuum

2286

S.V. Kutsaev, M.P. Kelly, P.N. Ostroumov
ANL, Argonne, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
A new power coupler is under development at Argonne National Laboratory for a cw 40 MeV proton/deuteron linac for the SARAF project in Israel. This linac requires one 15 kW RF input power per superconducting cavity. Two different cavity options are still under consideration: 10⁹ MHz quarter-waves and 176 MHz half-waves. A coaxial capacitive input coupler has been designed and analyzed for these purposes. This paper presents the results of 3D electromagnetic simulations of this coupler together with the cavities mentioned above. An analysis of multipacting in the couplers is also presented.

WEPPC037

A Ring-shaped Center Conductor Geometry for a Half-wave Resonator

quadrupole, impedance, linac, ion

2289

B. Mustapha, Z.A. Conway, P.N. Ostroumov
ANL, Argonne, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract DE-AC02-06CH11357.
Half-wave resonators (HWR) are used and being proposed for the acceleration of high-intensity proton and heavy-ion beams in the 0.1 < β < 0.5 velocity range. The highest performing half-wave resonator geometries use a center conductor with a race-track shaped cross section in the high-electric field region; a feature shared with spoke cavities which are also being proposed for the same velocity regime. We here propose a ring-shaped center conductor instead of the race-track shape. Preliminary studies show that the ring geometry has a similar peak surface electric field as the race-track one, but has several other advantages. In particular, the ring-shaped geometry has: a lower peak surface magnetic field, a much higher Shunt impedance for the same peak fields, and no quadrupole electric field asymmetry which has been observed in the race-track geometry. In a solenoid-based symmetric focusing, the quadrupole component may lead to unnecessary emittance growth which is not acceptable in high-intensity ion linacs. We will present a detailed comparison and a discussion of the two geometries.

WEPPC038

Status of the Short-Pulse X-ray Project at the Advanced Photon Source

LLRF, cryomodule, HOM, simulation

2292

A. Nassiri, N.D. Arnold, T.G. Berenc, M. Borland, B. Brajuskovic, D.J. Bromberek, J. Carwardine, G. Decker, L. Emery, J.D. Fuerst, A.E. Grelick, D. Horan, J. Kaluzny, F. Lenkszus, R.M. Lill, J. Liu, H. Ma, V. Sajaev, T.L. Smith, B.K. Stillwell, G.J. Waldschmidt, G. Wu, B.X. Yang, Y. Yang, A. Zholents
ANL, Argonne, USA
J.M. Byrd, L.R. Doolittle, G. Huang
LBNL, Berkeley, California, USA
G. Cheng, G. Ciovati, P. Dhakal, G.V. Eremeev, J.J. Feingold, R.L. Geng, J. Henry, P. Kneisel, K. Macha, J.D. Mammosser, J. Matalevich, A.D. Palczewski, R.A. Rimmer, H. Wang, K.M. Wilson, M. Wiseman
JLAB, Newport News, Virginia, USA
Z. Li, L. Xiao
SLAC, Menlo Park, California, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source Upgrade (APS-U) Project at Argonne will include generation of short-pulse x-rays based on Zholents’* deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. In collaboration with Jefferson Laboratory, we are prototyping and testing a number of single-cell deflecting cavities and associated auxiliary systems with promising initial results. In collaboration with Lawrence Berkeley National Laboratory, we are working to develop state-of-the-art timing, synchronization, and differential rf phase stability systems that are required for SPX. Collaboration with Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi-cavity geometries with lower- and higher-order modes waveguide dampers using ACE3P. This contribution provides the current R&D status of the SPX project.
* A. Zholents et al., NIM A 425, 385 (1999).

WEPPC039

Development of a Half-Wave Resonator for Project X

linac, SRF, cryomodule, ion

2295

P.N. Ostroumov, Z.A. Conway, R.L. Fischer, S.M. Gerbick, M. Kedzie, M.P. Kelly, B. Mustapha
ANL, Argonne, USA
I.V. Gonin, S. Nagaitsev
Fermilab, Batavia, USA

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics and Nuclear Physics, under Contract DE-AC02-76CH03000 and DE-AC02-06CH11357.
We have developed an optimized electromagnetic and mechanical design of a 162.5 MHz half-wave resonator (HWR) suitable for acceleration of high-intensity proton or H-minus beams in the energy range from 2 MeV to 10 MeV. The cavity design is based on recent advances in SRF technology for TEM-class structures being developed at ANL. Highly optimized EM parameters were achieved by adjusting the shapes of both inner and outer conductors. This new design will be processed with a new HWR horizontal electropolishing system after all mechanical work on the cavity including the welding of the helium jacket is complete. The prototype HWR is being fabricated by domestic vendors under ANL’s supervision.

WEPPC040

Evaluation of VATSEAL Technology to Seal Waveguide Serving High-field Superconducting RF Cavities

vacuum, SRF, impedance, radio-frequency

2298

B.K. Stillwell, J.D. Fuerst, J. Liu, G.J. Waldschmidt, G. Wu
ANL, Argonne, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A waveguide flange seal serving a high-field, superconducting, radio-frequency (SRF) cavity ideally possesses several characteristics. Seals must generally be ultrahigh-vacuum leak tight. Seals must also bridge the inner surfaces of connecting flanges for optimum transmission and minimal heating due to trapped modes. In addition, if seal contact areas are minimized, flange seals may serve as convenient thermal impedances. Finally, seals must be easily cleanable and not be prone to generate particulate matter during assembly and disassembly. A unique sealing technology known as VATSEAL may neatly address all of the above requirements. In this paper, we describe our evaluation of VATSEAL technology for use in SRF cavity assemblies.

WEPPC041

Tests of SRF Deflecting Cavities at 2K

SRF, vacuum, cryogenics, photon

2300

J.D. Fuerst, D. Horan, J. Kaluzny, A. Nassiri, T.L. Smith, G. Wu
ANL, Argonne, USA

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) at Argonne National Laboratory (ANL) is developing 2.8-GHz deflecting-mode superconducting rf cavities in collaboration with Jefferson Lab as part of a major facility upgrade. On-site testing of these cavities requires a new cryostat capable of operation at 2.0 K or less. The APS has leveraged facilities and expertise within ANL’s Physics Division to upgrade an existing test stand for continuous operation at temperatures as low as 1.7 K. A new cryogenic feedbox was fabricated and mated to an existing liquid helium “bucket” dewar with 0.6-m inside diameter and 1-m working depth. The configuration allows continuous sub-λ operation using warm vacuum pumping and helium make-up from the Physics Division’s existing cryoplant at heat loads up to 50 W dynamic, plus 15 W measured static load at 2.0 K. A 2.8-GHz TWT-based rf station has been installed and commissioned, providing up to 275 W of rf power. We describe the cryogenic and rf performance of the system and provide examples of cavity test results.

WEPPC043

Transverse Kick Analysis of SSR1 Due to Possible Geometrical Variations in Fabrication

simulation, linac, alignment, solenoid

2306

M.H. Awida, P. Berrutti, I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
Due to fabrication tolerance, it is expected that some geometrical variations could happen to the SSR1 cavities of Project X, like small shifts in the transverse direction of the beam pipe or the spoke. It is necessary to evaluate the resultant transverse kick due to these geometrical variations, in order to make sure that they are within the limits of the correctors in the solenoids. In this paper, we report the transverse kick values for various fabrications errors and the sensitivity of the beam to these errors.

WEPPC044

Multipole Effects Study for Project X Front End Cavities

multipole, quadrupole, linac, focusing

2309

P. Berrutti, M.H. Awida, I.V. Gonin, J.-F. Ostiguy, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, USA

Effects of RF field asymmetry along with multipoles have been studied in Project X front end cavities. One family of half wave resonators operating at 162.5 and two of spoke resonators operating at 325 MHz have been analysed. HWR and spoke resonators unlike elliptical cavities, do not have axial symmetry, hence a quadrupole perturbation to the beam is present. The purpose of this paper is to explain the approach and the calculation method used to understand and overcome the drawbacks due to the RF field asymmetry.

WEPPC045

Optimization of the Geometric Beta for the SSR2 Cavities of the Project X

linac, cryomodule, factory, proton

2312

P. Berrutti, M.H. Awida, I.V. Gonin, N. Solyak, A. Vostrikov, V.P. Yakovlev
Fermilab, Batavia, USA

Project X based on the 3 GeV CW superconducting Linac and is currently in the R&D phase. The cw SC Linac starts from a low-energy SCRF section (2.1 - 165 MeV) containing three different types of resonators. HWR f=162.5 MHz (2.1 - 11 MeV) having β= 0.11, SSR1 f= 325 MHz (11 - 35 MeV) having β = 0.21. In this paper we present the analysis that lead to the final design of SSR2 f=325 MHz cavity (35 - 165 MeV). We present the results of optimization of the geometric beta and the comparison between single, double and triple spoke resonators used in Project X frontend.

WEPPC046

Overview of Project X Superconducting RF Cavities and Cryomodules

cryomodule, linac, SRF, focusing

2315

T.N. Khabiboulline, M.S. Champion, C.M. Ginsburg, V.P. Yakovlev
Fermilab, Batavia, USA

The Project X Linac is based primarily on superconducting RF technology starting from a low beam energy of approximately 2.5 MeV up to the exit energy of 8 GeV. The Linac consists of 162.5 MHz half-wave cavities, 325 MHz single-spoke cavities, and two families of 650 MHz elliptical cavities - all operating in continuous-wave mode - up to a beam energy of 3 GeV. The beam is further accelerated up to 8 GeV in a pulsed mode ILC-like Linac utilizing 1.3 GHz cavities. In this paper we will give an overview of the design and status of the Project X superconducting RF cavities and cryomodules.

WEPPC047

Effects of the RF Field Asymmetry in SC Cavities of the Project X

linac, multipole, acceleration, focusing

2318

I.V. Gonin, M.H. Awida, P. Berrutti, A. Saini, B.G. Shteynas, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, USA
P.N. Ostroumov
ANL, Argonne, USA

The low-energy SCRF section of CW SC linac of Project X starts from Half Wave Resonators (HWR) having operating frequency f=162.5 MHz, optimal β= 0.11 and will accelerate the beam from 2 MeV up to 11 MeV. The preliminary analysis of beam dynamics shows that multipole effects caused by asymmetry of RF fields in HWR cavities aren’t negligible. In this paper we present the analysis of influence of multipole effects on beam dynamics and discuss the possible solutions how to compensate these effects.

WEPPC049

Individual RF Test Results of the Cavities Used in the First US-built ILC-type Cryomodule

cryomodule, SRF, radio-frequency, linear-collider

2321

A. Hocker, A.C. Crawford, E.R. Harms, A. Lunin, D.A. Sergatskov, A.I. Sukhanov
Fermilab, Batavia, USA
G.V. Eremeev, R.L. Geng
JLAB, Newport News, Virginia, USA
J.P. Ozelis
FRIB, East Lansing, USA

Funding: Work supported in part by the U.S. Department of Energy under Contract No. DE-AC02-07CH11359.
Eight 1.3-GHz, nine-cell SRF cavities have been installed in a cryomodule intended to demonstrate the ILC design goal of 31.5 MV/m. These cavities all underwent two types of individual RF testing: a low-power continuous-wave test of the “bare” cavity and a high-power pulsed test of the “dressed” cavity. Presented here is a discussion of the results from these tests and a comparison of their performance in the two configurations.

WEPPC050

Main Couplers for Project X

vacuum, radiation, linac, cryomodule

2324

S. Kazakov, M.S. Champion, S. Cheban, T.N. Khabiboulline, M. Kramp, Y. Orlov, V. Poloubotko, O. Pronitchev, V.P. Yakovlev
Fermilab, Batavia, USA

Design of 325MHz and 650MHz multi-kilowatt CW main couplers for superconducting linac of Project X is described. Results of electrodynamics, thermal and mechanical simulations is presented.

WEPPC051

Multipactor Simulation in SC Elliptical Shape Cavities

simulation, electron, multipactoring, accelerating-gradient

2327

S. Kazakov, I.V. Gonin, V.P. Yakovlev
Fermilab, Batavia, USA

Typically multipactor exists near equator region in elliptical shape superconductive cavities. If the multipactor power zone dose not coincide with operating power, it is often the cavity has to pass through it before it reaches operating level of field. Results of multipactor simulations for several shapes of elliptical cavity are presented. New shape, which significantly suppresses multipactor, is found.

WEPPC052

High Gradient Tests of the Fermilab SSR1 Cavity

multipactoring, vacuum, SRF, linac

2330

T.N. Khabiboulline, C.M. Ginsburg, I.V. Gonin, R.L. Madrak, O.S. Melnychuk, J.P. Ozelis, Y.M. Pischalnikov, L. Ristori, A.M. Rowe, D.A. Sergatskov, A.I. Sukhanov, I. Terechkine, R.L. Wagner, R.C. Webber, V.P. Yakovlev
Fermilab, Batavia, USA

In Fermilab we are build and tested several superconducting Single Spoke Resonators (SSR1, β=0.22) which can be used for acceleration of low beta ions. Fist two cavities performed very well during cold test in Vertical Test Station at FNAL. One dressed cavity was also tested successfully in Horizontal Test Station. Currently we are building 8 cavity cryomodule for PIXIE project. Additional 10 cavities were manufactured in the industry and ongoing cold test results will be presented in this poster.

WEPPC053

SSR1 HOM Analysis and Measurements

HOM, dipole, quadrupole, higher-order-mode

2333

M.H. Awida, P. Berrutti, I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
Single spoke resonators (SSR1, β=0.22) are currently under development for Project X at Fermilab. In this paper, extensive Higher Order Mode (HOM) analysis carried out on SSR1 is reported including the simulated R/Q for monopoles, dipoles, and quadrupoles. HOM measurements carried out on several spoke cavities are also reported including the harmonic response and the bead pull measurements. Comparison between the measured R/Q values and the simulated ones are presented.

WEPPC056

Pressure Sensitivity Characterization of Superconducting Spoke Cavities

simulation, linac, resonance, electromagnetic-fields

2339

D. Passarelli, M.H. Awida, I.V. Gonin, L. Ristori, V.P. Yakovlev
Fermilab, Batavia, USA

The following proposal illustrates a method to characterize the pressure sensitivity behavior of superconducting spoke cavities. This methodology relies on evaluating the variation of resonant frequency of a cavity by observing only the displacements at designed regions of the cavity. The proposed method permits a reduced computational burden and a systematic approach to achieve a minimum value of pressure sensitivity in a complex system of dressed cavity. This method has been used to characterize the superconducting spoke cavities typs⁻¹ (SSR1), under development for Project X, and to design the helium containment vessel in such way to reduce the pressure sensitivity value to zero.

WEPPC057

Design of SSR1 Single Spoke Resonators for PXIE

SRF, niobium, cryomodule, coupling

2342

L. Ristori, M.H. Awida, I.V. Gonin, M. Merio, D. Passarelli, V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
The Project X Injector Experiment (PXIE) at Fermilab contains one cryomodule of Single Spoke Resonators operating at 325 MHz with a geometrical beta of 0.2. Two prototypes have been tested successfully at high gradients in the Fermilab Vertical Test Stand (VTS). We have welded a Stainless Steel helium vessel on the first prototype and tested it in the spoke-dedicated Test Cryostat. With excellent results in hand, an order for ten bare resonators was placed with US industry. A new design for the helium vessel was developed for these resonators with the main goal of reducing the sensitivity of the resonator to variations of the helium pressure to meet the requirements of PXIE. A new tuner was developed despite the good results of the first prototype. The new design was inevitable due to the different behavior of the resonator in the new helium vessel. Other aspects were improved such as the maintainability of the tuner motor and piezoelectric actuators allowing their replacement from access ports on the cryomodule's vacuum vessel.

WEPPC058

Development at ANL of a Copper-brazed Joint for the Coupling of the Niobium Cavity End Wall to the Stainless Steel Helium Vessel in the Fermilab SSR1 Resonator

niobium, vacuum, coupling, SRF

2345

L. Ristori
Fermilab, Batavia, USA
W.F. Toter
ANL, Argonne, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
In order to reduce the sensitivity of the Fermilab SSR1 resonator to helium pressure variations, it was concluded that the cavity and helium vessel end-walls needed to be structurally coupled by means of a transition ring. With the materials to be connected being Niobium and Stainless Steel, it was decided to utilize the same technology already developed for the cavity flanges which consists of a furnace-brazed joint utilizing oxygen-free electrolytic copper. Small-scale and full-scale annular samples have been constructed at Argonne National Laboratory and subject to tensile tests, thermal cycling and visual inspections to qualify the joint. The transition ring is electron-beam welded to the cavity and TIG welded to the helium vessel, the process is explained in detail.

WEPPC059

A Two-stage Injection-locked Magnetron for Accelerators with Superconducting Cavities

linac, injection, simulation, controls

2348

G.M. Kazakevich, G. Flanagan, R.P. Johnson, F. Marhauser, M.L. Neubauer
Muons, Inc, Batavia, USA
B. Chase, S. Nagaitsev, R.J. Pasquinelli, N. Solyak, V. Tupikov, D. Wolff, V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Supported in part by SBIR Grant 4743 11SC06261
A concept for a two-stage injection-locked CW magnetron intended to drive Superconducting Cavities (SC) for intensity-frontier accelerators has been proposed. The concept is based on a theoretical model that considers a magnetron as a forced oscillator; the model has been experimentally verified with a 2.5 MW pulsed magnetron. The two-stage CW magnetron can be used as a RF power source for Fermilab’s Project-X to feed separately each of the SC of the 8 GeV pulsed linac. For Project-X the 1.3 GHz two-stage magnetron with output power of 20-25 kW and expected output/input power ratio of about 35-40 dB would operate in a quasi-CW mode with a pulse duration ≤ 10 ms and repetition rate of 10 Hz. The magnetrons for both stages should be based on the commercial prototypes to decrease the cost of the system. An experimental model of the two-stage CW S-band magnetron with peak power of 1 kW, with pulse duration of 1-10 ms, has been developed and built for study. A description of the theoretical and experimental models, simulations, and experimental results are presented and discussed in this work.

WEPPC063

Superconducting RF Cavity for High-current Cyclotrons

cyclotron, focusing, extraction, injection

2354

N. Pogue, P.M. McIntyre, A. Sattarov
Texas A&M University, College Station, Texas, USA

Funding: This work is supported by grants from the State of Texas (ASE) and the Mitchell Family Foundation.
A novel superconducting cavity is presented for applications in cyclotrons. The cavity is in effect an extrusion of a 2-D double-quarter-wave structure, in which the ends of the extrusion are wrapped around and joined so that the cavity has no end perturbations. Power is applied to a linear array of input coupling loops, so that rf sheet current is launched in a laminar flow that matches the power coupled to the orbits of the cyclotron. Each loop is driven by an independent solid-state rf source. A strategy is presented for using to advantage the independent control of phase and amplitude to suppress transient phenomena. Longitudinal modes can be strongly suppressed. These provisions are of importance to suppress phenomena that can limit beam current.

WEPPC065

Cleanroom Techniques to Improve Surface Cleanliness and Repeatability for SRF Coldmass Production

SRF, vacuum, superconductivity, controls

2357

L. Popielarski, L.J. Dubbs, K. Elliott, I.M. Malloch, R. Oweiss, J. Popielarski
FRIB, East Lansing, Michigan, USA

Funding: Work supported by US DOE Cooperative Agreement DE-SC0000661 and Michigan State University.
The Facility for Rare Isotope Beams (FRIB) and ReA linear accelerator projects at Michigan State University (MSU) utilize Superconducting Radio-Frequency (SRF) cavities for their accelerating structures. The structures are cleaned and assembled in a cleanroom to reduce particle contamination. The project requires more than 350 SRF cavities. In preparation for production we want to maximize repeatable processes and reduce work time. The cleanroom assembly group at MSU investigates process techniques performed in the cleanroom. Various diagnostic tools; such as liquid particle counter, surface particle counter and airborne particle counter are used to quantify environments and optimize processes. We desire to define procedure specifications for cleaner processes and repeatability. We investigate effective part cleaning and storage, high pressure rinse and ultra pure water quality, and critical component rinsing. We study vacuum assembly, pump down and purge effects. The experiments are independent of cavity results with a focus to create cleanest surface and environment in the most effective manner. In this paper, we describe experiments, summarize the results and conclusions.

WEPPC066

Niobium Reaction Kinetics: An Investigation into the Reactions Between Buffered Chemical Polish and Niobium and the Impact on SRF Cavity Etching

niobium, SRF, superconducting-RF

2360

I.M. Malloch, L.J. Dubbs, K. Elliott, R. Oweiss, L. Popielarski
FRIB, East Lansing, Michigan, USA

Funding: Work supported by US DOE Cooperative Agreement DE-SC0000661 and Michigan State University.
In the SRF community, there is no definitive agreement on the precise reaction mechanism in the etching of niobium cavities by buffered chemical polish (BCP) mixtures. As a consequence, it is difficult to predict the heat produced during cavity etching. To gain a better understanding of the reaction kinetics of niobium and BCP, calorimetry experiments were performed to establish an experimental heat of reaction, and research was performed to determine a reasonable reaction scheme to allow for calculation of the theoretical heat of reaction. The results of the calorimetry experiments were in excellent agreement with one another and with the theoretical value. These results will allow for more accurate estimation of etch removal amounts on cavities without the need to perform time-intensive etch rate tests. Applying the experimental data to pre and post cavity etch ultrasonic thickness measurements has shown a significant improvement in the predictability of etch removal amounts in Facility for Rare Isotope Beams (FRIB) half-wave and quarter-wave resonators, and will allow for more reliable heat removal and prevention of Q-disease during other cavity etching procedures.

WEPPC067

Dewar Testing of Coaxial Resonators at MSU

linac, niobium, cryomodule, SRF

2363

J. Popielarski, E.C. Bernard, A. Facco, M. Hodek, F. Marti, D. Norton, G.J. Velianoff, J. Wlodarczak
FRIB, East Lansing, Michigan, USA
A. Burrill, G.K. Davis
JLAB, Newport News, Virginia, USA

Funding: Work supported by US DOE Cooperative Agreement DE-SC0000661 and Michigan State University
Michigan State University is currently testing prototype and production cavities for two accelerator projects. 80.5 MHz β=0.085 quarter wave resonators (QWR) are being produced as part of a cryomodule for ReA3. 322 MHz β=0.53 half wave resonators (HWR) are being prototyped for a driver linac for the Facility for Rare Isotope Beams. This paper will discuss test results and how different cavity preparations effect cavity performs. Also various diagnostics methods have been developed, such as second sound quench location determination, and temperature mapping to determine hot spots from defects and multipacting location.

WEPPC068

Multipacting Simulation and Analysis for the FRIB β = 0.085 Quarter Wave Resonators using Track3P

simulation, resonance, linac, niobium

2366

L. Ge, C. Ko, Z. Li
SLAC, Menlo Park, California, USA
J. Popielarski
FRIB, East Lansing, Michigan, USA

Funding: Work supported by DOE Office of Science under Cooperative Agreement DE- SC0000661, DOE Contract No. DE-AC02-76SF00515, and used resources of NERSC supported by DOE Contract No. DE-AC02- 05CH11231.
The drive linac for the Facility for Rare Isotope Beams (FRIB) utilizes several types of low beta superconducting resonators to accelerate the ion beams from 0.3 MeV per nucleon to 200 MeV per nucleon. Multipacting is an issue of concern for such superconducting resonators as they have unconventional shapes. We have used the parallel codes Tack3P and Omega3P, developed at SLAC under the support of the DOE SciDAC program, to analyze the multipacting barriers of such resonators. In this paper, we will present the simulation results for the β(v/c) = 0.085 Quarter Wave Resonator (QWR) for the FRIB project. Experimental data will also be presented to benchmark with the simulation results.

WEPPC069

Construction, Evaluation, and Application of a Temperature Map for Multi-cell SRF Cavities

SRF, controls, vacuum, superconductivity

2369

G.M. Ge, F. Furuta, D.L. Hartill, K.M.V. Ho, G.H. Hoffstaetter, E.N. Smith
CLASSE, Ithaca, New York, USA

Temperature mapping (T-mapping) system is able to locate hot-spot of SRF cavity, thus it is a very powerful tool for cavity’s Q-value research. Recently Cornell University is developing a T-mapping system for multi-cell SRF cavities. The system includes more than two thousands Allen-Bradley resistors. Electronic of the system uses multiplexing of sensors which is able to dramatically reduce wire numbers, and allow the whole system is feasible for multi-cell cavity application. A new cavity testing insert which is for T-mapping system has been constructed.

WEPPC070

Automated Cavity Test Suite for Cornell's ERL Program

controls, EPICS, radiation, linac

2372

D. Gonnella, M. Liepe, N.R.A. Valles
CLASSE, Ithaca, New York, USA

As of 2011, fabrication and testing of main linac 7-cell cavities has begun for Cornell's Energy Recovery Linac prototype project. To standardize the testing process, minimize errors and allow for quick and precise measurements of these cavities, a suite of MatLab programs has been written to automate cavity tests. The programs allow measuring the quality factor versus temperature, and quality factor vs. accelerating gradient, and allow extracting material properties such as RRR and residual resistance. They are compatible with EPICS input/output controllers or standalone computers. Finally, the program can measure continuous Q vs E curves from a single high field decay curve, and can perform temperature mapping and quench localization from oscillating superleak transducer data.

WEPPC071

Quench Studies of a Superconducting RF Cavity

superconducting-RF, superconductivity, resonance, superconducting-cavity

2375

D. Gonnella, M. Liepe, S. Posen
CLASSE, Ithaca, New York, USA

In tests of superconducting RF cavities, it is important to understand the cause of high field quenches. Quenches at high field above 25 MV/m are a limiting factor in the performance of high accelerating field cavities but their causes are currently not well understood. An ILC shaped single cell cavity with quench field near 40 MV/m was tested with temperature mapping to determine the cause of its hard quench. Prior to quench, heating on the order of 25 mK was concentrated in two hot spots. After a quench, these two hot spots remain and a new one appears with much higher heating (about 40 mK). The quench location was found by the temperature mapping system to be centered at the new hot spot, not at the two hot spot locations before that dominated quench. By studying the quench location and heating on the surface of the cavity, some hints were gained as to the cause of this quench.

WEPPC072

High Current Operation of the Cornell ERL Superconducting RF Injector Cryomodule

HOM, SRF, cryomodule, damping

2378

M. Liepe, G.H. Hoffstaetter, S. Posen, P. Quigley, V. Veshcherevich
CLASSE, Ithaca, New York, USA

Cornell University has developed a SCRF injector cryomodule for the acceleration of high current, low emittance beams in continuous wave operation. This cryomodule is based on superconducting RF technology, and is currently under extensive testing in the Cornell ERL injector prototype with CW beam currents exceeding 25 mA. Strong damping of Higher-Order-Modes in the cavities is essential for high beam current operation, and is achieved by beamline RF absorber located at cryogenic temperatures in the beam pipe sections between the cavities. This paper gives an overview of the experience gained during the high beam current operation of the cryomodule.

WEPPC073

Progress on Superconducting RF Work for the Cornell ERL

linac, SRF, cryomodule, HOM

2381

M. Liepe, F. Furuta, G.M. Ge, Y. He, G.H. Hoffstaetter, T.I. O'Connell, S. Posen, J. Sears, M. Tigner, N.R.A. Valles, V. Veshcherevich
CLASSE, Ithaca, New York, USA

Cornell University is developing the superconducting RF technology required for the construction of a 100 mA hard X-ray light source driven by an Energy-Recovery Linac. Prototypes of all beam line components of the 5 GeV cw SRF main linac cryomodule have been fabricated and tested in detail. This work includes an optimized 7-cell SRF cavity, a broadband HOM beamline absorber, a cold frequency tuner, and a 5 kW CW RF input coupler. A one-cavity test cryomodule has been assembled for a first full cryomodule test of the main linac cavity, and is currently under testing. In this paper we give an overview of these extensive R&D activities at Cornell.

WEPPC074

HOM Studies on the Cornell ERL Prototype Cavity in a Horizontal Test Cryomodule

HOM, higher-order-mode, linac, simulation

2384

N.R.A. Valles, M.G. Billing, G.H. Hoffstaetter, M. Liepe, C.E. Mayes
CLASSE, Ithaca, New York, USA

The main linac 7-cell cavity for Cornell's Energy Recovery Linac was optimized to maximize threshold current through the ERL. This was achieved by designing center and end cells that reduce the strength of dipole higher-order modes. A prototype cavity was fabricated based on the optimized RF design and found to meet fundamental mode specifications in a vertical test. The higher-order-mode spectrum was measured when the cavity was installed in a horizontal test cryomodule and is compared to 2D and 3D EM simulations.

WEPPC075

Testing of the Main-Linac Prototype Cavity in a Horizontal Test Cryomodule for the Cornell ERL

linac, cryomodule, cryogenics, HOM

2387

N.R.A. Valles, F. Furuta, G.M. Ge, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, S. Posen, P. Quigley, J. Sears, M. Tigner, V. Veshcherevich
CLASSE, Ithaca, New York, USA

Cornell has recently finished producing and testing the first prototype 7-cell main linac cavity for the Cornell Energy Recovery Linac (ERL). The cavity construction met all necessary fabrication constraints. After a bulk BCP, 650C outgassing, final BCP, and 120C bake the cavity was vertically tested. The cavity met quality factor and gradient specifications (2·10¹⁰ at 16.2 MV/m) in the vertical test. Progressing with the ERL linac development, the cavity was installed in a horizontal test cryomodule and the quality factor versus accelerating gradient was again measured. This baseline measurement is the first test in a sequence of tests of the main linac cavity in the test cryomodule. Subsequent tests will be with increased complexity of the beam line, e.g. with HOM beamline loads installed, to study potential sources of reducing the cavity’s quality factor.

WEPPC078

Recent Developments in the Cornell Nb3Sn Initiative

niobium, linac, SRF, accelerating-gradient

2390

S. Posen, G.H. Hoffstaetter, M. Liepe, Y. Xie
CLASSE, Ithaca, New York, USA

Superconducting accelerator cavities coated with Nb3Sn have already demonstrated significantly higher unloaded quality factors than standard niobium cavities at surface magnetic fields <30 mT. Theoretical predictions suggest that the maximum critical field of such cavities could be twice that of niobium cavities. Significant facilities have been developed at Cornell University to fabricate Nb3Sn using the vapor diffusion technique. In this paper, recent progress is presented from our Nb3Sn program. The first RF results from a test of a Nb3Sn sample in a TE pillbox sample cavity are presented as well as first images of the newly constructed apparatus for coating full 1.3 GHz single cell cavities.

WEPPC079

Residual Resistance Studies at Cornell

SRF, linac, simulation, accelerating-gradient

2393

S. Posen, D. Gonnella, G.H. Hoffstaetter, M. Liepe
CLASSE, Ithaca, New York, USA
J. Oh
Cornell University, Ithaca, New York, USA

The Cornell single-cell temperature mapping system has been adapted for use with ILC and Cornell ERL-shape superconducting accelerator cavities. The system was optimized for low-noise, high-precision measurements with the goal of measuring resistances as low as 1 nohms. Using this system, a T-map of an ILC single cell was obtained at accelerating fields below the onset of Q-slope and at temperatures at which BCS resistance is small, producing a measurement of the distribution of residual resistance over the surface of the cavity. Standard procedures were used in preparing the cavity to avoid Q-disease and trapped flux caused by cooling the cavity through its transition in the presence of magnetic fields. Studying the T-map gives clues to the source of residual resistance, so that steps can be taken to reduce it, thereby lowering losses and increasing Q0. The temperature map noise-reduction studies as well as the residual resistance results are presented in this paper.

WEPPC080

Minimizing Helium Pressure Sensitivity in Elliptical SRF Cavities

simulation, linac, factory, beam-loading

2396

S. Posen, M. Liepe
CLASSE, Ithaca, New York, USA

Superconducting cavities in CW operation with small beam loading can operate at high QL to significantly reduce power requirements. However, the resulting small bandwidth makes them vulnerable to microphonics from helium pressure fluctuations, which can detune the cavity and cause it to trip. In this paper, we present a mechanical optimization of elliptical cavities for minimization of df/dp, the sensitivity to helium pressure changes. Using the Cornell ERL main linac cavity as an example, an analytical model is developed to illustrate the factors that contribute to df/dp. Methods to reduce df/dp are presented. In addition, df/dp measurements made at the Cornell Horizontal Test Cryostat are presented and corrections to the model are made to account for the thickness of the welds in the helium vessel.

WEPPC081

Measurement of the Mechanical Properties of Superconducting Cavities During Operation

resonance, linac, feedback, simulation

2399

S. Posen, M. Liepe
CLASSE, Ithaca, New York, USA

The Horizontal Test Cryostat (HTC) contains the first prototype 7-cell 1.3 GHz superconducting cavity for the Cornell ERL main linac. In this paper, experimental measurements of the cavity's mechanical properties are presented. The mechanical resonances were studied using a Dynamic Signal Analyzer, which measured the transfer function from the fast piezo tuner to itself and the cavity frequency. The microphonics detuning of the cavity was measured, and found to satisfy the specification that the maximum detuning be below 20 Hz, even without feedback from the piezos. Correlations were studied between the microphonics detuning and the helium pressure, piezo sense signal, and the ground vibrations. The Lorentz force detuning (LFD) coefficient was also measured. The frequencies of the mechanical resonances were compared to simulation. In addition, the performance of the frequency tuners was evaluated. Both the mechanical tuner and the piezo were found to be highly linear with very little hysteresis even on small scales.

WEPPC082

First Results on Cornell TE-type Sample Host Cavities

niobium, coupling, vacuum, pick-up

2402

Y. Xie, M. Liepe
CLASSE, Ithaca, New York, USA

Funding: Work supported by NSF and Alfred P. Sloan Foundation.
In order to measure surface resistance of new materials other than niobium such as Nb3Sn and MgB2, two sample host niobium cavities operating at TE modes have been developed at Cornell University. The first one is a 6GHz pillbox TE011 cavity modified from an older vision enabling testing 2.75'' diameter flat sample plates. The second one is an optimized mushroom-shape niobium cavity operating at both 5GHz TE012 and 6GHz TE013 modes for 3.75'' diameter flat sample plates . First results from the commissioning of the two TE cavities will be reported.

WEPPC083

Tunable 28 MHz Superconducting Cavity for RHIC

niobium, superconducting-cavity, site, superconducting-RF

2405

C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA
S.A. Belomestnykh, I. Ben-Zvi
BNL, Upton, Long Island, New York, USA

Funding: This research has been supported by a Department of Energy Small Business Innovative Research Phase II grant through the Nuclear Physics program office, contract #DE-SC0001215.
Replacement of the normal conducting 28 MHz accelerating cavities in the RHIC ring with superconducting structures offers a number of advantages for the machine operation, including reduction of the number of cavities required and improved HOM performance. A prototype folded quarter wave structure is under construction at Niowave, Inc. to meet this need. This novel cavity geometry achieves the very low resonant frequency required with a relatively compact structure, and can provide the large tuning range required (~1% of the cavity frequency). Progress of the cavity fabrication will be presented along with room temperature RF measurements.

WEPPC084

Development of a Superconducting 500 MHz Multi-Spoke Cavity for Electron Linacs

cryomodule, electron, SRF, niobium

2408

D. Gorelov, C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA
S.U. De Silva, J.R. Delayen, C.S. Hopper, R.G. Olave
ODU, Norfolk, Virginia, USA

Funding: This work is supported by the US Department of Energy SBIR/STTR program through the Office of Nuclear Physics.
Multi-spoke cavities are well-known options for acceleration of heavy and light ions. A recently developed multi-spoke cavity for β=1 presents an attractive opportunity to use this cavity type for electron accelerators. One of the main attractive features of this cavity type is its compactness for relatively low frequency. A simplified design at 500 MHz allowed building of a multi-spoke cavity and cryomodule in a 2-year time frame with confidence and development of effective manufacturing techniques. It also constitutes an important step in proving the usefulness of this kind of cavity design for new applications in the electron machines. Niowave is now in a position to build on the success of this cavity to help advance the design of superconducting electron accelerators. Accelerating voltage of more then 4.3 MV in a single cavity at 4.5 K is expected with peak electric field of less then 21.7 MV/m, and peak magnetic field of less then 80 mT. The paper discusses the fabrication challenges of the complete cavity and the cryomodule, as well as room temperature and cryogenic test results.

WEPPC085

Engineering of a Superconducting 400 MHz Crabbing Cavity for the LHC HiLumi Upgrade

luminosity, niobium, collider, SRF

2411

D. Gorelov, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA
S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA

Funding: This work is supported by the US DOE-HEP SBIR/STTR program and the US DOE through the US LHC Accelerator Research Program (LARP).
The recently developed new simplified design for the 400 MHz LHC crabbing cavity presents attractive properties compared to conventional designs. The proposed approach can be equally compact in both transverse dimensions and allows horizontal as well as vertical deflection of the beam in the collider. The significant modification of the parallel-bar design with the bars merged to the side walls of the cavity gives improved properties, such as better mode separation and reduced surface fields*. A transverse deflecting voltage of 3 to 5 MV in a single cavity can be expected with the peak surface electric field lower then 50 MV/m and peak magnetic field below 100 mT. This paper presents engineering issues of the proof-of-concept crabbing cavity design and discusses the manufacturing techniques. The paper discusses present status of the project including fabrication of the niobium cavity, as well as room temperature and cryogenic testing.
* J.R. Delayen, S.U. De Silva, "Design of Superconducting Parallel-Bar Deflecting/Crabbing Cavities with Improved Properties," Proc. of 2011 PAC, New York, NY, USA, 2011, p. 10²¹.

WEPPC086

Higher Order Modes Damping Analysis for the SPX Deflecting Cavity Cyromodule

damping, HOM, dipole, impedance

2414

L. Xiao, Z. Li, C.-K. Ng
SLAC, Menlo Park, California, USA
A. Nassiri, G.J. Waldschmidt, G. Wu
ANL, Argonne, USA
R.A. Rimmer, H. Wang
JLAB, Newport News, Virginia, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A single-cell superconducting deflecting cavity operating at 2.812 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source upgrade. A cryomodule of 4 such cavities will be needed to produce the required 2-MV deflecting voltage. Each deflecting cavity is equipped with one fundamental power coupler (FPC), one lower order mode (LOM) coupler, and two higher order mode (HOM) couplers to achieve the stringent damping requirements for the unwanted modes. The damping of the HOM/LOM modes below the beampipe cutoff has been analyzed in the single cavity geometry and shown to meet the design requirements. The HOMs above beam pipe cutoff in the 4-cavity cyromodule, however, may result in cross coupling which may affect the HOM damping and potentially trapped modes between the cavities which could produce RF heating to the beamline bellows and even be detrimental to the beam. We have evaluated the HOM damping and trapped modes in the 4-cavity cryomodule using the parallel finite element EM code ACE3P developed at SLAC. We will present the results of the cryomodule analysis in this paper.

WEPPC087

Second Harmonic Cavity Design for Project-X Main Injector

simulation, dipole, HOM, impedance

2417

L. Xiao, C.-K. Ng
SLAC, Menlo Park, California, USA
J.E. Dey, I. Kourbanis
Fermilab, Batavia, USA

In order to accelerate the proposed beam intensity for Project-X, a new RF system for Main Injector (MI) will be required. A new 53 MHz first harmonic RF cavity that meets the MI requirements for Project-X has been designed. In order to reduce the peak longitudinal beam density a 10⁶ MHz second harmonic RF system is also needed. The first harmonic RF cavity design is a quarter wave coaxial resonator with a single accelerating gap and a perpendicular biased ferrite tuner. The second harmonic RF cavity baseline design is similar to the fundamental one and scaled down from it. RF simulations and shape optimizations on the second harmonic cavity are carried out to obtain the optimal performance which meets Project-X requirements. The results are discussed and presented in this paper.

WEPPC088

Standardization of CEBAF 12 GeV Upgrade Cavity Testing

HOM, radiation, survey, LabView

2420

T. Bass, G.K. Davis, C. Grenoble, M. Stirbet
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
CEBAF 12GeV upgrade project includes 80 new 7-cell cavities to form 10 cryomodules. Each cavity underwent RF qualification at 2 Kelvin using a high power accelerating gradient test and an HOM survey in JLab’s Vertical Testing Area (VTA) before cavity string assembly. In order to ensure consistently high quality data, updated cavity testing procedures and analysis were implemented and used by a group of 10 VTA operators. For high power tests, a cavity testing procedure was developed and used in conjunction with a LabVIEW program to collect the test data. Additionally while the cavity was at 2K, an HOM survey was performed using a network analyzer and a combination of Excel and Mathematica programs. Data analysis was standardized and an online logbook, Pansophy, was used for data storage and mining. The Pansophy system allowed test results to be easily summarized and searchable across all cavity tests. In this presentation, the CEBAF 12GeV upgrade cavity testing procedure, method for data analysis, and results reporting results will be discussed.

WEPPC089

SRF Cavity Performance Overview for the 12 GeV Upgrade

cryomodule, SRF, radiation, HOM

2423

A. Burrill, G.K. Davis, C.E. Reece, A.V. Reilly, M. Stirbet
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The CEBAF accelerator, a recirculating CW electron accelerator that is currently operating at Jefferson Laboratory, is in the process of having 10 new cryomodules installed to allow for the maximum beam energy to be increased from 6 GeV to 12 GeV. This upgrade required the fabrication, processing and RF qualification of 80, seven cell elliptical SRF cavities, a process that was completed in February 2012. The RF performance achieve in the vertical testing dewars has exceeded the design specification by ~25% and is a testament to the cavity design and processing cycle that has been implemented. This paper will provide a summary of the cavity RF performance in the vertical tests, as well as review the overall cavity processing cycle and duration for the project.

WEPPC091

A Path to Higher Q0 with Large Grain Niobium Cavities

SRF, niobium, accelerating-gradient, induction

2426

P. Dhakal, G. Ciovati, G.R. Myneni
JLAB, Newport News, Virginia, USA

The improvement of the quality factor Q0 of superconducting radio-frequency (SRF) cavities at medium accelerating gradients (~ 20 MV/m) is important in order to reduce the cryogenic losses in continuous wave accelerators for a variety of applications. In recent years, SRF cavities fabricated from ingot niobium have become a viable alternative to standard high-purity fine-grain Nb for the fabrication of high-performing SRF cavities with the possibility of significant cost reduction. Initial studies*,**, demonstrated the improvement of Q0 at medium field in cavities heat treated at 800-1000 °C without subsequent chemical etching. To further explore this treatment procedure, a new induction furnace with an all-niobium hot-zone was commissioned. A single-cell 1.5 GHz cavity fabricated from ingot material from CBMM, Brazil, with RRR~200, was heat treated with the new furnace in the temperature range 600-1400 °C for several hours. Residual resistance values below 5 nano Ω have been consistently achieved on this cavity as well as Q0 values above 4.5×1010 at 2 K and 100 mT peak surface magnetic field. Q0-values of the order of 1011 have been measured at 1.5 K.
* G. Ciovati, et al., Phys. Rev. ST Accel. Beams 13, 022002 (2010).
** G. Ciovati, et al., Proc. of the 15th Int. Conf. on RF Superconductivity, Chicago, July 25-29, 2011, paper TUPO051

WEPPC092

12 GeV Upgrade Project - Cryomodule Production

cryomodule, SRF, HOM, controls

2429

J. Hogan, A. Burrill, G.K. Davis, M.A. Drury, M. Wiseman
JLAB, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The Thomas Jefferson National Accelerator Facility (Jefferson Lab) is producing ten 100+MV SRF cryomodules (C100) as part of the CEBAF 12 GeV Upgrade Project. Once installed, these cryomodules will become part of an integrated accelerator system upgrade that will result in doubling the energy of the CEBAF machine from 6 to 12 GeV. This paper will present a complete overview of the C100 cryomodule production process. The C100 cryomodule was designed to have the major components procured from private industry and assembled together at Jefferson Lab. In addition to measuring the integrated component performance, the performance of the individual components is verified prior to being released for production and assembly into a cryomodule. Following a comprehensive cold acceptance test of all subsystems, the completed C100 cryomodules are installed and commissioned in the CEBAF machine in preparation of accelerator operations. This overview of the cryomodule production process will include all principal performance measurements, acceptance criterion and up to date status of current activities.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.

WEPPC093

Commissioning and Operation of the CEBAF 100 MeV Cryomodules

cryomodule, controls, klystron, LLRF

2432

C. Hovater, T.L. Allison, R. Bachimanchi, G.K. Davis, M.A. Drury, L. Harwood, J. Hogan, A.J. Kimber, G.E. Lahti, W. Merz, R.M. Nelson, T. E. Plawski, D.J. Seidman, M. Spata, M.J. Wilson
JLAB, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, under U.S. DOE Contract No. DE-AC05-06OR23177.
The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of ten new 100 MeV cryomodules and RF systems. The superconducting RF cavities are designed to be operated CW at a maximum accelerating gradient of 19.2 MV/m. To support the higher gradients and higher QL (~ 3x107), a new RF system has been developed and is being installed to power and control the cavities. The RF system employs digital control and 13 kW klystrons. Recently, two of these cryomodules and associated RF hardware and software have been installed and commissioned in the CEBAF accelerator. Electrons at currents up to 150 μA have been successfully accelerated and used for nuclear physics experiments. This paper reports on the commissioning and operation of the RF system and cryomodules.

WEPPC094

Optimizing Centrifugal Barrel Polishing for Mirror Finish SRFCavity and Rf Tests at Jefferson Lab

SRF, radio-frequency, controls, superconductivity

2435

A.D. Palczewski, R.L. Geng, H. Tian
JLAB, Newport News, Virginia, USA

Funding: This work is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We performed Centrifugal Barrel Polishing (CBP) on a 1.3GHz fine grain ILC SRF cavity following a modified version of the recipe* originally developed at Fermilab (FNAL)**. We were able to obtain a mirror like surface similar to that obtained at FNAL, while reducing the number of CBP steps. This paper will discuss the change in surface and subsequent cavity performance before CBP on a raw cavity and post CBP, after a 800C bake (no pre-bake chemistry) and minimal controlled electro-polishing (below 10 micron). In addition to Q vs. Eacc thermometry maps with preheating characteristics and optical inspection of the cavity before and after CBP will also be shown.
* A. D. Palczewski et al., Proc. of SRF2011, THPO071 (2011).
** C.A. Cooper et al., FERMILAB-PUB-11-032-TD, (May 31, 2011).

WEPPC095

Evaluation of Silicon Diodes as In-situ Cryogenic Field Emission Detectors for SRF Cavity Development

ion, radiation, SRF, cryogenics

2438

A.D. Palczewski, R.L. Geng
JLAB, Newport News, Virginia, USA

Funding: This work is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We performed in-situ cryogenic testing of five silicon diodes as possible candidates for field emission monitor of SRF cavities in vertical testing dewars and in cryo-modules. We evaluated diodes from 2 companies - from Hamamatsu corporation model S5821-02 (used at KEK)* and S1223-02; and from OSI Optoelectronics models OSD35-LR-A, XUV-50C, and FIL-UV20. The measurements were done by placing the diodes in superfluid liquid helium near a field emitting 9-cell cavity during its vertical test. For each diode, we will discuss their viability as a 2K cryogenic detector for FE mapping of SRF cavities and their directionality in such environments. We will also present calibration curves between the diodes and JLab’s standard radiation detector placed above the dewar top plate and within radiation shielding.
* H. Sakai et al., Proc of IPAC10, WEPEC028 p. 2950 (2010).

WEPPC096

Exploring the Effect of AL2O3 ALD Coating on a High Gradient ILC Single-Cell Cavity

niobium, SRF, electron, site

2441

G.V. Eremeev, A-M. Valente-Feliciano, A.T. Wu
JLAB, Newport News, Virginia, USA
D. Gu
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Encouraged by work at Argonne National Lab, we investigated atomic layer deposition technique for high gradient superconducting RF cavities at JLab with an ALD coating system of Old Dominion University located on the JLab site. The goal of this study was to look into the possibility of coating a dielectric layer on top of RF niobium surface at a lower temperature of 120 C as compared to ANL coatings at 200 C in order to preserve niobium pentooxide on niobium surface. The initial coatings showed complete, but non-uniform coatings of the surface with several areas exhibiting discoloration, which was probably due to the temperature variation during coatings. The initial coating showed a high RF losses, which were improved after discolored areas on the beam tubes were removed with HF rinse of the beam tubes only. The best result was 2·10⁹ low field Q0 and Eacc = 18 MV/m limited by available power.

WEPPC100

Design of Electron and Ion Crabbing Cavities for an Electron-Ion Collider

HOM, electron, ion, damping

2447

A. Castilla, J.R. Delayen, G.A. Krafft
ODU, Norfolk, Virginia, USA
A. Castilla
JLAB, Newport News, Virginia, USA

Beyond the 12 GeV upgrade at the Jefferson Lab a Medium Energy Electron-Ion Collider (MEIC) has been considered. In order to achieve the desired high luminosities at the Interaction Points (IP), the use of crabbing cavities is under study. In this work, we will present to-date designs of superconducting cavities, considered for crabbing both ion and electron bunches. A discussion of properties such as peak surface fields and higher-order mode separation will be presented.

WEPPC101

Characteristics and Fabrication of a 499 MHz Superconducting Deflecting Cavity for the Jefferson Lab 12 GeV Upgrade

vacuum, electron, target, niobium

2450

H. Park, S.U. De Silva
JLAB, Newport News, Virginia, USA
J.R. Delayen
ODU, Norfolk, Virginia, USA

A 499 MHz parallel bar superconducting deflecting cavity has been designed and optimized for a possible implementation at the Jefferson Lab 12 GeV upgrade. This paper will present the analysis of the mechanical characteristics of the cavity (pressure sensitivity and tunability) and will detail the fabrication process. The unique geometry of the cavity–which is currently being fabricated at Jefferson Lab–and its required mechanical strength present interesting manufacturing challenges.

WEPPC102

Design and Development of Superconducting Parallel-bar Deflecting/Crabbing Cavities

HOM, luminosity, pick-up, damping

2453

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
S.U. De Silva
JLAB, Newport News, Virginia, USA

The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties that is being considered for a number of applications. We present the designs of a 499 MHz deflecting cavity developed for the Jefferson Lab 12 GeV Upgrade and a 400 MHz crabbing cavity for the LHC High Luminosity Upgrade. Prototypes of these two cavities are now under development and fabrication.

WEPPC103

Development of Spoke Cavities for High-velocity Applications

electron, higher-order-mode, multipole, impedance

2456

C.S. Hopper, J.R. Delayen
ODU, Norfolk, Virginia, USA
R.G. Olave
Old Dominion University, Norfolk, Virginia, USA

In response to recent interest in alternatives to elliptical cavities for low-frequency, high-velocity applications we have initiated a program for the development of multi-spoke superconducting cavities. We have completed the electromagnetic design for two-spoke cavities operating at 352 and 325 MHz and a design velocity of β = 0.82 and β = 1. We present the results of the optimization, higher order mode (HOM) analysis, multipacting analysis, and an initial multipole expansion study of the fundamental accelerating mode.

WEPPC104

Tomography as a Diagnostic Tool for Plasma Etching of SRF Cavities

plasma, SRF, niobium, diagnostics

2459

M. Nikolić, A.L. Godunov, S. Popović, A. Samolov, L. Vušković
ODU, Norfolk, Virginia, USA
F. Čučkov
Old Dominion University, Norfolk, USA

Plasma based surface modification is a promising alternative for etching of superconductive radio frequency (SRF) cavities. A plasma processed SRF cavity presents a plasma reactor with limited or distorted symmetry. We are developing a tomographic reconstruction of local plasma parameters, as a diagnostic tool in the plasma etching setting of SRF cavities. The method is non-invasive and provides deep insight into the fundamental processes and phenomena during the plasma treatment of SRF cavities’ surfaces. Here we report on our progress in developing tomographic numerical method, based on 2D inverse Radon formula. We tested it on supersonic flowing microwave discharge maintained in the cylindrical quartz tube. Due to the model’s sensitivity to the noise signal in the experiment, an automated measurement system has been built with the aim to increase the overall precision of data acquisition as well as to stream line the measurement process.

WEPPC105

Study of Etching Rate Uniformity in SRF Cavities

plasma, electron, SRF, coupling

2462

J. Upadhyay, S. Popović, L. Vušković
ODU, Norfolk, Virginia, USA
H.L. Phillips, A-M. Valente-Feliciano
JLAB, Newport News, Virginia, USA

Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. The crucial aspect of the technology development is dependence of the etching rate and surface roughness on the frequency of the power supply, pressure, power level, driven electrode shape and chlorine concentration in gas mixture during plasma processing. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders are used as diagnostic ports for the measurement of the plasma parameters and as holders for the samples to be etched. The plasma properties are highly correlated with the shape of the driven electrode and the percentage of chlorine concentration in Argon/chlorine gas mixtures. The effect of the plasma parameters and chlorine gas concentration are investigated at RF (100 MHz) and microwave (2.45 GHz) frequencies.

WEPPC106

The First ASME Code Stamped Cryomodule at SNS

cryomodule, vacuum, linac, neutron

2465

M.P. Howell, D.R. Bruce, M.T. Crofford, D.L. Douglas, S.-H. Kim, S.E. Stewart, W.H. Strong
ORNL, Oak Ridge, Tennessee, USA
R. Afanador, B.S. Hannah, J. Saunders
ORNL RAD, Oak Ridge, Tennessee, USA
J.D. Mammosser
JLAB, Newport News, Virginia, USA

The first spare cryomodule for the Spallation Neutron Source (SNS) has been designed, fabricated, and tested by SNS personnel. The approach to design for this cryomodule was to hold critical design features identical to the original design such as bayonet positions, coupler positions, cold mass assembly, and overall footprint. However, this is the first SNS cryomodule that meets the pressure requirements put forth in the 10 CFR 851: Worker Safety and Health Program. The most significant difference is that Section VIII of the ASME Boiler and Pressure Vessel Code was applied to the vacuum vessel of this cryomodule. Applying the pressure code to the helium vessels within the cryomodule was considered. However, it was determined to be schedule prohibitive because it required a code case for materials that are not currently covered by the code. Good engineering practice was applied to the internal components to verify the quality and integrity of the entire cryomodule. The design of the cryomodule, fabrication effort, and cryogenic test results will be reported in this paper.

WEPPC107

RF Distribution System for High Power Test of the SNS Cryomodule

controls, cryomodule, EPICS, LLRF

2468

S.W. Lee, M. Broyles, M.T. Crofford, X. Geng, Y.W. Kang, S.-H. Kim, R.C. Peglow, C.L. Phibbs, W.H. Strong, A.V. Vassioutchenko
ORNL, Oak Ridge, Tennessee, USA

Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
A four-way waveguide RF power distribution system for testing the SNS multi-cavity cryomodule to investigate the collective behavior has been developed. A single klystron operating at 805MHz in 60Hz 8% duty cycle powers the 4-way waveguide splitter to deliver up to 600 kW to Individual cavities. Each cavity is fed through a waveguide vector modulator at each splitter output with magnitude and phase control. Waveguide vector modulator consists of two quadrature hybrids and two motorized waveguide phase shifters. The phase shifters and the assembled waveguide vector modulators were individually tested and characterized for low power and high pulsed RF power in the SNS RF test facility. Precise calibrations of magnitude and phase are done to generate the look up tables (LUTs) to provide operation references during the cryomodule test. An IQ demodulator board was developed and utilized to generate 2-port magnitude and phase LUTs. PLC units were developed for mechanical control of the phase shifters. Labview software was programmed for the measurements and the system operation. LUT based operation algorithm was implemented into EPICS control for the cryomodule test stand.

WEPPC108

Status of SRF Facilities at SNS

cryomodule, SRF, linac, controls

2471

J. Saunders, R. Afanador, T. Xu
ORNL RAD, Oak Ridge, Tennessee, USA
M.T. Crofford, M.P. Howell, S.-H. Kim, S.E. Stewart
ORNL, Oak Ridge, Tennessee, USA

SNS has recognized the need for developing in-house capability to ensure long term sustainability of the SCL. SNS has made substantial gains in the last 6 years in understanding SCL operation, including system and equipment limiting factors, and resolution of system and equipment issues. Significant effort and focus is required to assure ongoing success in the operation, maintenance, and improvement of the SCL and to address the requirements of the upgrade project for the Second Target Station. This interdependent effort includes implementation of demonstrated improvements, fabrication of spare cryomodules, cavity R&D to enhance machine performance, and related SRF facility developments. Cryomodule and vertical cavity testing facilities are being developed to demonstrate process capabilities and to further understand the collective limitations of installed cavities. The status and future plans for SRF facilities at SNS will be presented.

WEPPC109

Superconducting RF Systems for eRHIC

SRF, linac, electron, hadron

2474

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, H. Hahn, D. Kayran, G.J. Mahler, G.T. McIntyre, C. Pai, I. Pinayev, V. Ptitsyn, J. Skaritka, R. Than, J.E. Tuozzolo, Q. Wu, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, V. Litvinenko, T. Xin
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Future electron-hadron collider eRHIC will consist of a six-pass 30-GeV electron ERL and one of RHIC storage rings operating with energy up to 250 GeV. The collider design extensively utilizes superconducting RF (SRF) technology in both electron and hadron parts. This paper describes various SRF systems, their requirements and parameters.

WEPPC110

3D Simulations of Multipacting in the 56 MHz SRF Cavity

simulation, HOM, electron, higher-order-mode

2477

Q. Wu, S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA
L. Ge, C. Ko, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 56 MHz SRF Quarter-Wave Resonator (QWR) is designed for RHIC as a storage cavity to improve the collider performance. 2D multipacting simulation has been done for the cavity alone. Ripples were added to the outer body of the cavity for multipacting suppression based on the simulation findings. During operation, there will be four higher order mode (HOM) couplers and a fundamental power coupler (FPC) inserted through the end ports of the cavity and a fundamental mode damper (FD) inserted through a special port on the outer body. All of these components will be exposed to high RF fields. In this presentation we compare 2D and 3D codes simulation results for multipacting in the cavity. We also report 3D simulation results for multipacting simulation at the couplers.

WEPPC111

Multipacting Simulation ADN Test Results of BNL 704 MHz SRF Gun

cathode, gun, SRF, simulation

2480

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, C. Cullen, H. Hahn, X. Liang, G.T. McIntyre, D. Pate, S.P. Pontieri, C. Schultheiss, T. Seda, T.N. Tallerico, R. Than, R.J. Todd, S.J. Tuozzolo, A. Zaltsman
BNL, Upton, Long Island, New York, USA
J. Dai
SBU, Stony Brook, New York, USA
L.R. Hammons
Stony Brook University, Stony Brook, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The BNL 704 MHz SRF gun has a grooved choke joint to support the photo-cathode. Due to the distortion of grooves at the choke joint during the BCP for the choke joint, several multipacting barriers showed up when it was tested with Nb cathode stalk at JLab. We built a setup to use the spare large grain SRF cavity to test and condition the multipacting at BNL with various power sources. The test is carried out with three steps: cavity, cavity with Nb cathode stalk, and cavity with copper cathode stalk. This paper summarizes the results of multipacting simulation, and presents large grain cavity test setup and the test results.

WEPPC112

Development of a Fundamental Power Coupler for High-Current Superconducting RF Cavity

simulation, collider, linac, electron

2483

P. Jain
Stony Brook University, Stony Brook, USA
S.A. Belomestnykh, I. Ben-Zvi, W. Xu
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE and by the DOE grant DE-SC0002496 to Stony Brook University.
Brookhaven National Laboratory has undertaken a project to design a five-cell superconducting 703.75 MHz RF cavity for the Energy Recovery Linac (ERL) and the planned RHIC electron cooler. The earlier developed cavity, viz., the BNL1 is fed by a klystron using a co-axial Fundamental Power Coupler (FPC), which delivers 50 kW of cw RF power to the cavity. During the cavity operation, it has been observed that a 5 K cooling line intercept in the FPC introduces undesirable microphonics. A modification in the existing FPC has been planned to determine the feasibility of getting rid of the 5 K cooling line. The modified coupler will be incorporated in the newly designed, under construction BNL3 cavity. In order to accommodate this modification, peak microphonics of 12 Hz and 20 kW of cw RF power will be considered. This paper describes the design of the new FPC starting from the analysis of thermal profile along its length from first principles.

WEPPC113

Progress on the High-Current 704 MHz Superconducting RF Cavity at BNL

HOM, damping, higher-order-mode, impedance

2486

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn, P. Jain
BNL, Upton, Long Island, New York, USA
C.M. Astefanous, M.D. Cole, J.P. Deacutis, D. Holmes
AES, Medford, NY, USA

Funding: This work was supported by Sotny Brook under contract No. DE-SC0002496 and Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups for the copper prototype, and presents comparison of the experimental results with computer simulations. The progress with the niobium cavity fabrication will also be described.

WEPPC115

High Q0 in Superconducting Niobium Cavities: Progress at FNAL and Future Plans

niobium, SRF, factory, vacuum

2492

A. Grassellino, L.D. Cooley, C.M. Ginsburg, A. Romanenko, A.M. Rowe, V.P. Yakovlev
Fermilab, Batavia, USA

Consistent improvement in the quality factors of SRF cavities at medium surface fields of about 70 mT represents a direct cost savings factor for the proposed Project X CW linac and other SRF accelerator projects based on CW operation. Current state-of-the-art in SRF does not provide processing recipes to maximize the Q0 at those fields since a complete understanding of the mechanisms governing the quality factor at non-negligible surface fields is not yet developed. In this contribution we present results of the FNAL effort in both scientific understanding and practical improvements and discuss the directions we are pursuing for future research.

WEPPC116

Depth Distribution of Losses in Superconducting Niobium Cavities

niobium, SRF, positron, vacuum

2495

A. Romanenko, A. Grassellino, J.P. Ozelis
Fermilab, Batavia, USA
H. Padamsee
CLASSE, Ithaca, New York, USA

In order to optimize performances of superconducting niobium cavities it is crucial to understand the structure of near-surface few tens of nanometers of the material. In particular, superconducting properties of niobium, which depend on the presence of impurities and/or defects, may be non-uniform in the magnetic field penetration depth. A few cavity experiments based on oxypolishing* and anodizing**,*** provided some insight into the problem, but the definitive understanding is not developed yet. In this contribution we report on the "depth profiling" of the near-surface RF layer using an alternative technique based on the hydrofluoric acid (HF) rinsing. Tumbled, electropolished and buffered chemical polished cavities have been investigated and tentative nanostructural interpretation is discussed.
* P. Kneisel, Proc. of the 1999 SRF Workshop, Santa Fe, USA
** G. Eremeev and H. Padamsee, Physica C 441 No. 1-2 (2006) 62
*** G. Ciovati, P. Kneisel and A. Gurevich, PRSTAB 10 (2007) 062002

WEPPD002

The Purifier System for Helium Cryogenic Plant in NSRRC

cryogenics, controls, SRF, synchrotron

2498

H.C. Li, S.-H. Chang, C.M. Cheng, W.-S. Chiou, F. Z. Hsiao, T.F. Lin, C.P. Liu, H.H. Tsai
NSRRC, Hsinchu, Taiwan

A cryogenic adsorber is a purifier cooled with liquid nitrogen that is used to trap impurities from gaseous helium in the helium cryogenic system. The output purity can be decreased to less than 5 ppm and the dew point to -62 °C. The maximum rate of flow of each adsorber is 95 Nm3/h. We installed five cryogenic adsorbers in the cryogenic system and completed its testing in 2011; five additional cryogenic adsorbers will be installed in 2012. The configuration, installation, test results and operation of an cryogenic adsorber system are reported herein.
"cryogenic adsorber","purifier"

WEPPD005

SSR1 Cryomodule Design PXIE

cryomodule, vacuum, solenoid, cryogenics

2504

T.H. Nicol, S. Cheban, M. Chen, S. Kazakov, F. McConologue, Y. Orlov, D. Passarelli, V. Poloubotko, O. Pronitchev, L. Ristori, I. Terechkine
Fermilab, Batavia, USA

Funding: U.S. Department of Energy
Fermilab is planning to design and build a Project X Injector Experiment (PXIE), a cw linac, as a means of validating the Project X concept, reducing technical risks, and obtaining experience in the design and operation of a superconducting proton linac. The overall facility will include an ion source, low and medium-energy beam transport sections, a radio frequency quadrupole, and two cryomodules containing superconducting cavities. One will contain nine half-wave resonators operating at 162.5 MHz and six superconducting solenoids. The second will contain eight single spoke resonators (SSR1) operating at 325 MHz and four superconducting solenoids. This paper describes the design of the cryomodule being developed to house the 325 MHz single spoke resonators. Each of the main cryomodule systems will be described; cryogenic systems and instrumentation, cavity and solenoid positioning and alignment, conduction-cooled current leads, RF input couplers, magnetic shielding, cold-to-warm beam tube transitions, interfaces to interconnecting equipment and adjacent modules, as well as the overall assembly procedure.

WEPPD054

Development of Pulsed Laser Systems and Cathode-performance Studies for the S-DALINAC Polarized Injector

laser, cathode, electron, vacuum

2642

M. Espig, C. Eckardt, J. Enders, Y. Fritzsche, N. Kurichiyanil, J. Lindemann, M. Wagner
TU Darmstadt, Darmstadt, Germany

A source of polarized electrons has recently been implemented at the superconducting Darmstadt electron linear accelerator S-DALINAC. We give an overview of the recent performance of the system. Photo-emission from a superlattice-GaAs photo-cathode is obtained from using either a DC diode laser or a short-pulse Ti:Sapphire laser system. For a robust pulsed quasi-cw operation, it is investigated whether a VECSEL system (Vertical-Cavity Surface-Emitting Laser) can be realized with a wavelength of 780 nm and a repetition rate of 3 GHz with pulse widths of a few picoseconds only. To enhance the availability and performance of the polarized source with respect to quantum efficiency, a separate atomic-hydrogen cleaning system for the cathodes is planned which will allow cathode treatment to be tested and optimized. Supported by DFG within CRC/SFB 634 and by the state of Hesse in the LOEWE-Center HIC for FAIR.

WEPPD055

Gamma-rays Generation with 3D 4-mirror Cavity for ILC Polarized Positron Source

laser, photon, electron, scattering

2645

T. Akagi, S. Miyoshi
Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima, Japan
S. Araki, Y. Funahashi, Y. Honda, T. Okugi, T. Omori, H. Shimizu, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
H. Kataoka, T. Kon
Seikei University, Japan
M. Kuriki, T. Takahashi
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
K. Sakaue, M. Washio
RISE, Tokyo, Japan
R. Tanaka, H. Yoshitama
Hiroshima University, Higashi-Hiroshima, Japan

We are conducting gamma-rays generation experiment by the laser-Compton scattering using a Fabry-Perot cavity. We developed a 3D 4-mirror cavity, and it is installed at the KEK-ATF. By using a 3D 4-mirror cavity, small laser spot can be achieved with stable resonant condition. In addition, we aim 1900 times enhancement of input laser power by a 4-mirror cavity to increase the number of gamma-rays.

WEPPD056

Ytterbium Fiber Laser System of DAW RF Gun for SuperKEKB

laser, emittance, gun, luminosity

2648

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

For obtaining higher luminosity in the SuperKEKB, the photocathode DAW-type RF gun for high-current, low-emittance beams will be employed in the injector linac. The electron beams with a charge of 5 nC and a normalized emittance of 10 micrometer are expected generate in the photocathode RF gun by using the laser source with a center wavelength of 260 nm and a pulse width of 30 ps. Fiber laser especially Ytterbium(Yb) fiber have attracted attention as one of the promising practical alternatives to usual solid-state lasers, offering high energy-extraction efficiency, high repetition rate, high output power, low-cost and so on. Introducing the Ytterbium fiber laser system, we have developed a stable laser amplifier system, which could allow steady beam injection into the SuperKEKB rings. The laser system starts with a large mode-area Yb-doped fiber-based amplifier system, which consists of a passively mode-locked femtosecond Yb-fiber oscillator. To obtain the mJ-class pulse energy, a multi-pass solid-state amplifier is employed. Deep UV pulses for the photocathode are generated by using two frequency-doubling stages. High pulse energy and good stability would be expected.

WEPPD058

The Project-X 3 GeV Beam Distribution System

cryogenics, kaon, linac, ion

2651

D.E. Johnson, M.H. Awida, M.S. Champion, I.V. Gonin, A.L. Klebaner, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, USA

In the Project X facility, a 3 GeV H⁻ CW beam is delivered to three users simultaneously. This will be accomplished by selectively filling appropriate RF buckets at the front end of the linac and then utilizing a RF splitter to transversely separate bunches to three different target halls. A compact TE113 squashed-wall superconducting RF cavity has been proposed to produce the initial vertical deflection. The transport line optics, cavity design parameters, and cryogenic system requirements will be presented.

WEPPD063

Construction of Disk-loaded Buncher for S-Band Low Energy TW Electron Linear Accelerator

electron, linac, impedance, coupling

2666

F. Ghasemi, F. AbbasiDavani, S. Ahmadiannamini, M.Sh. Shafiee
sbu, Tehran, Iran
M.L. Lamehi Rashti, H. Shaker
IPM, Tehran, Iran

The project of design and construction of Traveling linear electron accelerator is being performed by the Institute for Research in Fundamental Sciences (IPM) and Shahid Beheshti University in Iran. By using the results of the calculations and by dynamic simulation of electron beam in the designed buncher, the dimensions of the designed sample have been obtained. This paper discuss construction of this buncher.

WEPPD068

High Power Collinear Load Coated with FeSiAl

simulation, linac, resonance, factory

2678

L.G. Shen, X.L. Fu, Y. Sun, F. Zhang
USTC/PMPI, Hefei, Anhui, People's Republic of China
Y.J. Pei
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: This work is supported by the NSFC (NO. 10775128 and NO.51075381)
Aimed at substituting output coupler to absorb remnant power of the LINAC, collinear load coated with high loss materials is expected to come reality. FeSiAl load is studied. The effect of the coating volume upon the cavity frequency and Q factor is analyzed and the dimension compensations of the cavities are suggested to tune the load cavities at 2856 MHz. Orthogonal Experimental Method is utilized to investigate the sensitivity of permittivity (both real part and imaginary part) and permeability (both real part and imaginary part) to cavity characteristics. Five cavities with different coating dimensions are manufactured and their operating frequencies and Q are measured. Compared with the simulations, they show that the Q factor, which is characterization of the actual attenuation of the FeSiAl, agrees very well with the theoretical value and Q factor of the resonant cavity is measured with the probe method. The relationship between Q factor and the length of the test probe is deduced and eventually the individual Q value of a load cavity is extracted. Simulation shows the FeSiAl load can support average power over 15 kW and the one-way attenuation is about 30 dB.

WEPPD072

Frequency Fine-tuning of a Spin-flip Cavity for Antihydrogen Atoms

resonance, antiproton, coupling, vacuum

2690

S. Federmann, F. Caspers, E. Mahner
CERN, Geneva, Switzerland
B. Juhasz, E. Widmann
SMI, Vienna, Austria

As part of the ASACUSA collaboration physics program a spin-flip cavity for measurements of the ground-state hyperfine transition frequency of anti-hydrogen atoms is needed. The purpose of the cavity is to excite anti-hydrogen atoms depending on their polarisation by a microwave field operating at 1.42 GHz. The delicacy of designing such a cavity lies in achieving and maintaining the required properties of this field over a large aperture of 10cm and for a long period of time (required amplitude stability is 1% within 12h). The present paper presents the frequency fine tuning techniques to obtain the desired centre frequency of 1.42 GHz with a Q value below 500 as well as the tuning circuit used for the frequency sweep over the desired bandwidth of 6 MHz.

WEPPD076

A Fast Kicker for a Staged Dielectric Two-beam Wakefield Accelerator

kicker, wakefield, FEL, klystron

2702

J.G. Power, M.E. Conde, W. Gai
ANL, Argonne, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: Work supported by DoE, Office of HEP.
An experimental program to demonstrate staging in a dielectric two-beam wakefield accelerator (dielectric TBA) is being planned at the Argonne Wakefield Accelerator (AWA) facility. We are planning an experiment that both fits in the AWA tunnel and mimics conditions similar to the recently presented conceptual design of a linear collider based on the dielectric TBA. This conceptual design is based on a new parameter space of the TBA scheme utilizing an ultra-short (~20ns) rf pulse in a dielectric TBA. The decelerating structures are driven by a series of drive microbunch trains that are 20 ns in duration and separated by 100 ns. This means that the fast kicker must have an extremely quick risetime as well as become stable within about 50 ns. In this paper, we consider designs for a fast kicker based on RF deflecting cavities and stripline kickers.

WEPPP011

Multi-Cavity Proton Cyclotron Accelerator: An Electron Counterpart

proton, electron, cyclotron, acceleration

2744

M.A. LaPointe, S.V. Shchelkunov
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield
Omega-P, Inc., New Haven, USA
V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Supported by the Department of Energy, Office of Nuclear Physics.
A multi-cavity multi-frequency proton cyclotron accelerator has been proposed. It would utilize cyclotron resonance in each of eight cavities of uniformly diminishing frequency in a uniform magnetic field to comprise a compact (25 m) 1 GeV proton accelerator, according to simulation results*. A four cavity electron counterpart is under construction to test the mechanism of the multi-cavity setup, including phase acceptance, energy gain, and growth of energy spread and emittance for parameters equivalent to the proton case. The four electron counterpart cavities are driven by kW-level phase coherent RF sources at 1.5, 1.8, 2.1 and 2.4 GHz. Each cavity operates in the rotating TE111 mode and includes two feeds in quadrature to drive the rotating mode and two RF pickoffs for diagnostics. The electron beam source is a low-current gun with a BaO cathode which operates at -1200V and <50 microamps. After traversing the cavities, the beam is collected on either a Faraday cup or is imaged with a phosphor screen. Details of the setup and initial results from experiments with the four cavity electron counterpart will be presented.
* M.A. LaPointe, V.P. Yakovlev, S.Yu. Kazakov, and J.L. Hirshfield, Proc. of PAC 2009, May 4-8,Vancouver, BC, Canada, pp.3045-3047 (2011).

WEPPP059

First Measurements with Multibunch Feedback Systems at the Fast Ramping Stretcher Ring ELSA

feedback, kicker, damping, electron

2840

M. Schedler, F. Frommberger, N. Heurich, W. Hillert, A. Roth, R. Zimmermann
ELSA, Bonn, Germany

Funding: Supported by German Research Foundation through SFB/TR 16.
At the Electron Stretcher Facility ELSA of Bonn University, an upgrade of the maximum stored beam current from 20 mA to 200 mA is planned. The storage ring operates applying a fast energy ramp of 4 GeV/s from 1.2 GeV to 3.5 GeV. The intended upgrade is mainly limited due to the excitation of multibunch instabilities. As a countermeasure, we succesfully commissioned state-of-the-art bunch by bunch feedback systems in the longitudinal and the two transverse dimensions. First results concerning the commissioning of the systems as well as the operation during the fast energy ramp will be presented. In particular, the performance while controlling the motion of every single bunch, especially in controlled bunch cleaning, will be discussed.

WEPPP073

Dynamic Feedback Model for High Repetition Rate Linac-driven FELs

linac, feedback, FEL, beam-loading

2879

J.M. Byrd, L.R. Doolittle, P. Emma, G. Huang, A. Ratti, C. Serrano
LBNL, Berkeley, California, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
One of the concepts for the next generation of linac-driven FELs is a cw superconducting linac driving an electron beam with MHz repetition rates. One of the challenges for next generation FELs is improve the shot-to-shot stability of the energy, charge, peak current, and timing jitter of the electron beam. The use of a cw RF system with MHz beam repetition rates presents an opportunity to use broadband feedback to stabilize the beam parameters. To understand the performance of such a feedback system, we are are developing a dynamic feedback model of the machine with a focus on the longitudinal beam properties. The model is being developed as an extension of the LITrack code and will include the dynamics of the beam-cavity interaction, RF feedback, beam-based feedback, and multibunch effects. In this paper, we will present the status of this model along with results.

WEPPP074

Study of a Wideband Feedback Kicker for the SPS

kicker, impedance, feedback, simulation

2882

S. De Santis, Z. Paret, A. Ratti
LBNL, Berkeley, California, USA
A. Gallo, F. Marcellini
INFN/LNF, Frascati (Roma), Italy

Funding: Work supported by the US Department of Energy under Contracts DE-AC02-05CH11231 and DE-AC02-76SF00515, and through the US LHC Accelerator Research Program (LARP).
The LHC luminosity upgrade currently being planned at CERN depends in large measure on a successful upgrade of its injectors chain. In particular the storing of higher currents in the SPS presents a significant challenge from the point of view of the beam stability. Electron cloud driven and transverse mode-coupled instabilities can disrupt the stored beam to the point of making injection in the LHC impossible. These types of instabilities are characterized by fast growth times and substantial spectral components at high frequency. Therefore a key aspect of any feedback system capable of effectively controlling the instability growth is the development of a suitable kicker with a high frequency response. In this paper we investigate the technologies available for such a kicker and identify a possible solution to be implemented on the SPS. By combining a lower frequency stripline kicker with a high frequency module, such as a damped cavity or a slotted waveguide, it would be possible to provide shunt impedances around 1000 Ω on a bandwidth from DC to 1 GHz. The basic parameters and limits of such a solution are discussed.

WEPPP077

Control of RF Transients in Cavities Induced by Pulsed High Current Beams

SRF, controls, feedback, linac

2891

F. Löhl, J. Dobbins, R.P.K. Kaplan, C.R. Strohman
CLASSE, Ithaca, New York, USA

Funding: Supported by NSF award DMR-0807731.
The Cornell ERL prototype injector is operated either in a cw or in a pulsed mode. In the latter case, the bunch trains, which have a duration of 100 ns to 10 microseconds and a beam current of up to 100 mA, generate transients in the RF cavity fields which severely distort the beam quality and cause beam loss. In this paper, we present a scheme we use to correct the fast transients based on an adaptive feed-forward method.

WEPPP093

Time and Phase Synchronisation at ESS

controls, LLRF, neutron, target

2927

A.J. Johansson
Lund University, Lund, Sweden
R. Zeng
ESS, Lund, Sweden

ESS is a next generation spallation source to be built in Lund, Sweden. It is a green field laboratory, and as such it has the opportunity to establish one central timing reference for all systems, from control systems through reference phases for the Linac RF generators to the scientific instruments at the detector. We will here present the proposed architecture for this timing and phase reference system.

WEPPR008

Simulation of Controlled Longitudinal Emittance Blow-up in J-PARC RCS

emittance, simulation, resonance, extraction

2952

M. Yamamoto, M. Nomura, A. Schnase, T. Shimada, F. Tamura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda, M. Yoshii
KEK, Ibaraki, Japan
T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

In the J-PARC RCS, a high intensity beam is prepared for the MR. The longitudinal beam emittance at the RCS extraction should be optimized to avoid beam loss during and after MR injection. In order to match the longitudinal emittance shape between the RCS and the MR, it is desirable to enlarge the longitudinal emittance during the RCS acceleration. We have performed the particle tracking simulation for the controlled longitudinal emittance blow up in the RCS.

WEPPR017

Wake Fields Effects for the eRHIC Project

wakefield, vacuum, electron, beam-transport

2976

A.V. Fedotov, S.A. Belomestnykh, D. Kayran, V. Litvinenko, V. Ptitsyn
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
An Energy Recovery Linac (ERL) with a high peak electron bunch current is proposed for the Electron-Ion collider (eRHIC) project at the Brookhaven National Laboratory. The present design is based on the multi-pass electron beam transport in existing tunnel of the Relativistic Heavy Ion Collider (RHIC). As a result of a high peak current and a very long beam transport, consideration of various collective beam dynamics effects becomes important. Here we summarize effects of the coherent synchrotron radiation, resistive wall, accelerating cavities and wall roughness on the resulting energy spread and energy loss for several scenarios of the eRHIC project, including results for different electron distributions. A possible correction scheme of accumulated correlated energy spread is also presented.

WEPPR029

Alternative Cavity for H E Part of the Project X linac

HOM, linac, cryomodule, emittance

2997

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

An alternative superconducting elliptical cavity is suggested for High Energy (HE) part of the Project X linac. The cavity is suitable to operate at CW regime with high beam current (10 mA), which is critical for Accelerator-Driven Subcritical (ADS) systems and for intense muon source for future Neutrino Factory or Muon Collider. We present the algorithm of the cavity shape optimization, comprehensive tolerances analysis and the solution for monopole High Order Modes (HOM) damping. Based on these results we estimated the probabilities of cryogenic losses per cryomodule and a growth of the beam longitudinal emittance due to the resonance excitation of monopole HOMs in the HE linac for Project X.

WEPPR034

Longitudinal Phase Space Measurement for the Advanced Superconducting Test Accelerator Photoinjector

emittance, diagnostics, simulation, collimation

3009

C.R. Prokop, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
M.D. Church, Y.-E. Sun
Fermilab, Batavia, USA

Funding: LANL LDRD program, project 20110067DR -U.S. DOE Contract No. DE-FG02-08ER41532 and DE-AC02-07CH11359.
The Advanced Superconducting Test Accelerator (ASTA) at Fermilab uses a high-brightness photoinjector capable of producing electron bunches with charges up to 3.2 nC, to be used in support of a variety of advanced accelerator R&D experiments. The photoinjector incorporates an extensive diagnostics suites including a single-shot longitudinal-phase-space diagnostics composed of a horizontally deflecting cavity followed by a vertical spectrometer. In this paper, we present the design, optimization, and performance analysis (including detrimental collective effects) of the longitudinal phase space diagnostics and especially compare two possible choices of deflecting cavity frequencies.

WEPPR037

First-Principle Approach for Optimization of Cavity Shape for High Gradient and Low Loss

superconductivity, wakefield, multipactoring, superconducting-cavity

3015

V.D. Shemelin, G.H. Hoffstaetter
CLASSE, Ithaca, New York, USA

Funding: Supported by NSF award DMR-0807731.
Minimization of surface fields for a given accelerating rate is the subject of cavity optimization because high electric and magnetic fields lead to field emission or thermal breakdown, respectively. The ratio between peak electric and magnetic fields is a function of geometry and the desired ratio depends on application. For each application the optimal geometry may be different. The elliptic shape of the cavity have been found evolutionarily: starting from a pill-box with beam-pipes having rounded corners. No attempts up to now are known for a search of non-elliptical optimal shapes. Here we describe the search for a cavity shape that has the lowest surface fields, not restricting to the conventional elliptical cavity shapes.

WEPPR060

Short range wakefields in MAX IV and FERMI Linac

wakefield, linac, electron, dipole

3063

O. Karlberg, F. Curbis, S. Thorin, S. Werin
MAX-lab, Lund, Sweden
P. Craievich, E. Ferrari, G. Penco
ELETTRA, Basovizza, Italy

Ultra-short electron pulses suffer from transverse wake fields resulting in a degradation of the beam quality. Since transverse emittance is a crucial parameter for possible FEL drivers, a careful characterization of wakefields is necessary in the design and commissioning phase of a high-brightness linear accelerator. In this paper we investigate the effect of short-range transverse wakefields in the MAXIV linac in various compression modes. Estimations of the wake potentials have been done with 3D modeling of the accelerating structures as well as with analytical models.

WEPPR062

The Mode Matching Method Applied to Beam Coupling Impedance Calculations of Finite Length Devices

impedance, coupling, simulation, resonance

3069

N. Biancacci, E. Métral, B. Salvant
CERN, Geneva, Switzerland
M. Migliorati, L. Palumbo
URLS, Rome, Italy
V.G. Vaccaro
Naples University Federico II and INFN, Napoli, Italy

The infinite length approximation is often used to simplify the calculation of the beam coupling impedance of accelerator elements. This is expected to be a reasonable assumption for devices whose length is greater than the transverse dimension but may be less accurate approximation for segmented devices. This contribution presents the study of the beam coupling impedance in the case of a finite length device: a cylindrical cavity loaded with a toroidal slab of material. In order to take into account the finite length we will decompose the field in the cavity and in the beam pipe into a set of orthonormal modes and apply the mode matching method to obtain the impedance. To validate our method, we will present comparisons between analytical formulas and 3D electromagnetic CST simulations as well as applications to the impedance of short beam pipe inserts, where the longitudinal and transverse dimensions are difficult to model in numerical simulations.

WEPPR067

Study of Fundamental Mode Multipolar Kicks in Double- and Single-feed Power Couplers for the CLIC Main Linac Accelerating Structure

linac, simulation, emittance, multipole

3081

A. Latina, A. Grudiev, D. Schulte
CERN, Geneva, Switzerland

Multipolar kicks from the fundamental mode have been calculated in the CLIC baseline accelerating structure with double–feed input and output power couplers. The influence of such multipolar kicks on the main linac beam dynamics has been investigated. Furthermore, an alternative design of the couplers with single-feed has been studied and compared with the double-feed. Such an alternative would significantly simplify the waveguide system of the main linac but potentially introduce an harmful dipolar kick from the fundamental mode. The geometry of the coupler has been optimized in order to minimize such a dipolar kick and keep it below threshold levels determined with beam dynamics simulations. Influence of the higher order multipoles has been investigated as well and acceptable levels have been determined.

WEPPR070

Beam Coupling Impedance Simulations of the LHC TCTP Collimators

impedance, simulation, coupling, vacuum

3090

H.A. Day, R.M. Jones
UMAN, Manchester, United Kingdom
F. Caspers, A. Dallocchio, L. Gentini, A. Grudiev, E. Métral, B. Salvant
CERN, Geneva, Switzerland

As part of an upgrade to the LHC collimation system, 8 TCTP and 1 TCSG collimators are proposed to replace existing collimators in the collimation system. In an effort to review all equipment placed in the accelerator complex for potential side effects due to collective effects and beam-equipment interactions, beam coupling impedance simulations are carried out in both the time-domain and frequency-domain of the full TCTP design. Particular attention is paid to trapped modes that may induce beam instabilities and beam-induced heating due to cavity modes of the device.

WEPPR081

The Collective Effects of the Short Pulsed X-Ray (SPX) System in the Advanced Photon Source Upgrade

impedance, simulation, emittance, collective-effects

3117

Y.-C. Chae, M. Borland
ANL, Argonne, USA

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 is a 7-GeV hard x-ray synchrotron light source. The APS Upgrade specifies a short-pulse x-ray (SPX) as well as additional beamlines delivering higher brightness and flux. In order to achieve this goal we plan to use S-band superconducting cavities. The performance of such a system based on the zero-current simulation is well established; here, we included the effect of wakefields generated by the SPX system. While the SPX system is off, we are interested in how much current we can store in the single bunch, because the SPX contributes a significant amount of broadband impedance to the ring. With the SPX system on, we are interested in how much vertical emittance will increase, which in turn will enlarge the x-ray pulse length. We report the results of both cases when the SPX system is installed in the ring for the APS Upgrade.

WEPPR083

New Sector 37 Chamber Design and Installation for High-Current Operation of the APS Storage Ring

impedance, vacuum, storage-ring, HOM

3123

Y.-C. Chae, R. Bechtold, W. Berg, L. Erwin, M. Givens, J.E. Hoyt, L.H. Morrison, K.M. Schroeder, R. Soliday, J.B. Stevens, G.J. Waldschmidt
ANL, Argonne, USA

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 is a 7-GeV hard x-ray synchrotron light source consisting of 40 sectors. Sector 37 accommodates four radio-frequency cavities followed by a short straight section, which is set aside for the future installation of a diagnostic device. The 60-cm-long section of spool pieces can be isolated by two gate valves and has an independent vacuum pump. The spool pieces are normally under high vacuum condition when the total current is below 100 mA. However, at the higher current required for the APS Upgrade, rf heating causes an unacceptable rise in temperature. We analyzed this situation by wakefield simulation, which led to a new chamber design. Proper fabrication and careful installation with twelve thermocouples ensured a temperature rise under 40-50 degrees Celsius at 100 mA. A brief thermal analysis shows that the present observed temperature rise in the new chamber is mainly due to the resistive wall.

WEPPR093

Impedance Budget for Crab Cavity in MEIC Electron Ring

impedance, electron, collider, ion

3153

S. Ahmed, G.A. Krafft, B.C. Yunn
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The Medium Energy Electron-Ion Collider (MEIC) at Jefferson Lab has been envisioned as a first stage high energy particle accelerator beyond the 12 GeV upgrade of CEBAF. The estimate of impedance budget is important from the view point of beam stability and matching with other accelerator components driving currents. The detailed study of impedance budget for electron ring has been performed by considering the current design parameters of the e-ring. A comprehensive picture of the calculations involved in this study has been illustrated in the paper.

WEPPR094

Large Volume Resonant Microwave Discharge for Plasma Cleaning of a CEBAF 5-Cell Srf Cavity

plasma, electron, coupling, SRF

3156

S. Ahmed, K. Macha, J.D. Mammosser
JLAB, Newport News, Virginia, USA
M. Nikolić, S. Popović, J. Upadhyay, L. Vušković
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S.
We report preliminary results on plasma generation in a 5-cell CEBAF SRF cavity for the application of cavity interior surface cleaning. CEBAF currently has ~300 of these five cell cavities installed in the JLab accelerator which are mostly limited by cavity surface contamination. The development of an in-situ cavity surface cleaning method utilizing a resonant microwave discharge could lead to significant performance improvement. This microwave discharge is currently being used for set of plasma cleaning procedures targeted to the removal of various organic, metal and metal oxide impurities. These contaminants are responsible for the increase of surface resistance and the reduction of RF performance in installed cavities. CEBAF five cell cavity volume is ~ 0.5 m2, which places the discharge in the category of large-volume plasmas. Our preliminary study includes microwave breakdown and optical spectroscopy, which was used to define the operating pressure range and the rate of removal of organic impurities.

WEPPR096

Recirculating Beam Breakup Study for the 12 GeV Upgrade at Jefferson Lab

HOM, cryomodule, linac, simulation

3162

I. Shin, S. Ahmed, R.M. Bodenstein, S.A. Bogacz, T. Satogata, M. Stirbet, H. Wang, Y. Wang, B.C. Yunn
JLAB, Newport News, Virginia, USA
I. Shin
University of Connecticut, Storrs, Connecticut, USA

Two new high gradient C100 cryostats with a total of 16 new cavities were installed at the end of the CEBAF south linac during the 2011 summer shutdown as part of the 12 GeV upgrade project at Jefferson Lab. We ran recirculating beam breakup (BBU) study in November 2011 to evaluate CEBAF low energy performance, measure transport optics, and evaluate BBU thresholds due to higher order modes (HOMs) in these cavities. This paper discusses the experiment setup, cavity measurements, machine setup, optics measurements, and lower bounds on existing CEBAF C100 BBU thresholds established by this experiment.

WEPPR100

Short-Range Wakefields of Slowly Tapered Structures

wakefield, focusing, factory, simulation

3174

B. Podobedov
BNL, Upton, Long Island, New York, USA

We present new analytical results for short-range geometric wakefields of slowly tapered accelerator structures in 2D geometry.

THEPPB008

Inverse Compton Scattering Experiment in a Bunch Train Regime Using Nonlinear Optical Cavity

laser, electron, photon, linac

3245

A.Y. Murokh, R.B. Agustsson, S. Boucher, P. Frigola, T. Hodgetts, A.G. Ovodenko, M. Ruelas, R. Tikhoplav
RadiaBeam, Santa Monica, USA
M. Babzien, M.G. Fedurin, T.V. Shaftan, V. Yakimenko
BNL, Upton, Long Island, New York, USA
I. Jovanovic
Penn State University, University Park, Pennsylvania, USA

Inverse Compton Scattering (ICS) is a promising approach towards achieving high intensity, directional beams of quasi-monochromatic gammas, which could offer unique capabilities in research, medical and security applications. Practicality implementation of ICS sources, however, depends on the ability to achieve high peak brightness (~0.1-1.0 ICS photons per interacting electron), while increasing electron-laser beam interaction rate to about 10,000 cps. We discuss the results of the initial experimental work at the Accelerator Test Facility (ATF) at BNL to demonstrate ICS interaction in a pulse-train regime, using a novel laser recirculation scheme termed Recirculation Injection by Nonlinear Gating (RING). Initial experimental results and outlook are presented.

THEPPB013

Progress in Modeling Arcs

plasma, electron, ion, simulation

3260

J. Norem, Z. Insepov
ANL, Argonne, USA
S. Mahalingam, S.A. Veitzer
Tech-X, Boulder, Colorado, USA
A. Moretti
Fermilab, Batavia, USA
I. Morozov, G.E. Norman
JIHT RAS, Moscow, Russia

Funding: DOE Office of High Energy Physics.
We are continuing to extend and simplify our understanding of vacuum arcs. We believe that all the breakdown phenomena we see (with and without B fields) can be explained by: 1) fracture due to electrostatic forces at surface crack junctions, 2) the development of a unipolar arc driven by the cavity electric field, and 3) cooling, and cracking of the surface after the event is finished. Recent progress includes the evaluation of non-Debye sheaths using Molecular Dynamics, studies of sheath driven instabilities, a model of degradation of gradient limits in strong B fields, analysis of the variety of arcs that can occur in cavities and their damage and further studies of breakdown triggers.

THEPPB014

LLRF Testing of Superconducting Cryomodules for the European XFEL

cryomodule, LLRF, controls, feedback

3263

J. Branlard, V. Ayvazyan, T. Jeżyński, H. Schlarb
DESY, Hamburg, Germany
W. Cichalewski, W. Jałmużna, A. Piotrowski
TUL-DMCS, Łódź, Poland

During the installation phase of the European XFEL (2014), an average of one superconducting cryomodule per week will be tested and validated before being installed into the XFEL tunnel. Extensive tests will be carried in order to assess the RF performance of each cryomodule. A series of low level RF (LLRF) tests are planned as part of this validation phase, and will assess the cryomodule effective operating gradient, tuning range, compensation of Lorentz force detuning and microphonic behavior. These tests will be carried at DESY, in the Cryomodule Test Bench (CMTB) during the early stage of cryomodule production, and later at the Accelerating Module Test Facility (AMTF). Due to the pace and quantity of the modules to be tested, these tests have to be fully automated. This contribution presents the LLRF tests for the XFEL cryomodule validation, the challenges associated with automation, along with the first experimental results obtained on pre-series cryomodules tested at CMTB.

THPPC001

Simulation and Design of a 70 MeV Cyclotron RF System

cyclotron, simulation, vacuum, resonance

3269

G. Gold, R.R. Johnson, B.F. Milton, V. Sabaiduc
BCSI, Vancouver, BC, Canada

The electromagnetic and mechanical design of the resonant cavity for a 70 MeV compact commercial cyclotron has been conducted by Best Cyclotron Systems Inc. Various resonator configurations have been studied for a radial, single-stem design and an optimal solution was selected with excellent electromagnetic properties and minimized construction and operational cost. Rapid model iterations during the design, using CST Microwave Studio and ANSYS, allowed for accurate tuning of geometry to precisely define the shape of the accelerating voltage profile, surface current distribution, and total power loss. The RF system of the BEST 70p cyclotron will operate at the fourth harmonic with two λ/2 separated resonant cavities shielded at the center allowing for beam modulation techniques to be applied through phase modulation of the accelerating voltage.

THPPC003

Development of a Broad-band Magnetic Alloy Cavity at GSI

impedance, coupling, storage-ring, ion

3275

T.S. Mohite, U. Ratzinger
IAP, Frankfurt am Main, Germany
R. Balß, P. Hülsmann
GSI, Darmstadt, Germany

FINEMET, a Magnetic Alloy material, is often used to build a broad-band cavity for an accelerator or a storage ring. A research on the broad-band FINEMET cavity is of prime importance not only for the present accelerator facility but also for the future storage rings and synchrotron in upcoming FAIR facility alongside the GSI, Darmstadt. In several measurements, high intensity rare-isotope beams, with lower life time, are demanded at injection energy in Experimental Storage Ring (ESR) at GSI. A longitudinal beam stacking of such beams by means of using a special barrier-bucket RF cavity is found appropriate to serve this purpose*. Additionally, this cavity is supposed to provide the compressed bunches at lower energies for HITRAP, an ion-trap facility for experiments with highly charged ions, in FAIR. Several measurements are being performed, along with the theoretical analysis, to achieve the designed parameters for the planned barrier-bucket cavity. 60 FINEMET ring cores have been tested to confirm their designed electrical properties. Some of these ring cores are then loaded, in steps, in a test cavity, which will further be used as the barrier-bucket cavity for the ESR.
* C. Dimopoulou et al., JACoW Proceedings of COOL 2007, Bad Kreuznach, Germany

THPPC005

Design of Magnetic Alloy Resonant System (MARS) Cavity for J-PARC MR

impedance, beam-loading, acceleration, status

3278

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

The Magnetic Alloy Resonant System (MARS) cavity is a new type of Magnetic Alloy (MA) cavity using an external energy storage system. It is proposed as a back-up system of the present J-PARC high-Q MA cavity using cut cores. MARS consists of un-cut core loaded wideband MA cavities combined with an energy storage system using high-impedance, FT3L, cut cores. The main cavities are water-cooled and already established at J-PARC RCS. The energy storage system will be relatively high-Q (>100) to be stable under heavy beam loading. It also has a higher impedance than the main cavity and is air-cooled. The design of this cavity system will be presented.

THPPC006

Status of the J-PARC Ring RF Systems

impedance, synchrotron, proton, beam-loading

3281

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

Due to the 11th march earthquakes, J-PARC was forced to stop operation. The restoration is following the schedule so that J-PARC is restarted in December. Before the earthquake, we had considerable success in the 400 kW equivalent proton beam in the RCS. Multi-harmonic RF feedforward was established, which contributes to the reduction of beam loss and stable acceleration in RCS. The MR synchrotron achieved stable 150 kW beam operation for the T2K experiment. This summer, we installed two new RF systems in MR. Eight RF systems in total allow a more stable beam acceleration and flexible bunch shape manipulation. Also, we prepare the RF feedforward to compensate beam loading in MR. To achieve a beam power in excess of 1 MW in MR, it is considered to double the MR repetition rate. We developed an annealing scheme for large magnetic alloy cores while inside a DC B-field that results in higher core impedance, and have succeeded in producing large FT3L cores in this summer. With such cores we can almost double the accelerating voltage without re-designing the existing RF sources. For the near future, we plan to replace the existing RF cavities with upgraded cavities using the FT3L cores.

THPPC007

Coupling Cavity Design of RF Input Coupler Tests for the IFMIF/EVEDA Prototype RFQ Linac

coupling, rfq, linac, beam-transport

3284

S. Maebara
JAEA, Ibaraki-ken, Japan
M. Ichikawa
Japan Atomic Energy Agency (JAEA), International Fusion Energy Research Center (IFERC), Rokkasho, Kamikita, Aomori, Japan

In the design of prototype RFQ linac for the IFMIF/EVEDA Project, a 175MHz RFQ, which has a longitudinal length of 9.78m, was proposed to accelerate deuteron beam up to 5MeV. The operation frequency of 175MHz was selected to accelerate a large current of 125mA in cw mode. The overall driving RF power of 1.28 MW by 8 RF input couplers has to be injected to the RFQ cavity. For the transmitted RF power tests of RF couplers, a coupling cavity to connect with two RF couplers is needed. For this purpose, two types of coupling cavities for the 175MHz have been designed. One is a capacitive coupling cavity with a co-axial waveguide and double loop coupling structures, and the other one is a ridge cavity type with a rectangular waveguide. In this article, these RF designs and engineering designs will be presented in detail.

THPPC008

Coupling Factor Evaluation of the RF Input Coupler for the IFMIF/EVEDA RFQ Linac

rfq, coupling, beam-loading, linac

3287

S. Maebara
JAEA, Ibaraki-ken, Japan
M. Ichikawa
Japan Atomic Energy Agency (JAEA), International Fusion Energy Research Center (IFERC), Rokkasho, Kamikita, Aomori, Japan
A. Palmieri
INFN/LNL, Legnaro (PD), Italy

In the design of prototype RFQ linac for the IFMIF/EVEDA Project, a 175 MHz RFQ, which has a longitudinal length of 9.78m, was proposed to accelerate deuteron beam up to 5MeV. The operation frequency of 175MHz was selected to accelerate a large current of 125mA in CW mode. The overall driving RF power of 1.28 MW by 8 RF input couplers has to be injected to the RFQ cavity. As a part of the validation of the coupler design, the beta factor (coupling coefficient) was measured on Aluminum RFQ at INFN Legnaro with on-purpose, real-scale dummy aluminum couplers for the installed depths of L=27, 40, 45, 48 and 73 mm. In this article, measurement and calculation results performed with the 3D code HFSS for coupling factor evaluation will be presented in details.

THPPC012

Impedance Computation of Main Components in CSNS/RCS

impedance, simulation, extraction, vacuum

3299

Y. Li, L. Huang, Z.P. Li, Y.D. Liu, N. Wang, S. Wang
IHEP, Beijing, People's Republic of China

The rapid cycling synchrotron (RCS) of the China spallation neutron source (CSNS) is a high intensity proton accelerator. The study on the coupling impedance in the ring plays an important role in the stability of the beam. The impedance of the main vacuum components in the RCS ring, such as RF cavities, bellows, ports of vacuum pumps, collimator etc, was calculated by using numerical methods. Meantime, RF shielding of bellows, collimators and ports of vacuum pumps are considered. The impact of the busbar configuration on RF cavities and beams was estimated by impedance calculation.

THPPC013

Progress on Coupled RFQ-SFRFQ Accelerator for Materials Irradiation Research

rfq, ion-source, ion, ECR

3302

Z. Wang, J.E. Chen, S.L. Gao, Z.Y. Guo, Y.R. Lu, S.X. Peng, W.L. Xia, X.Q. Yan, J. Zhao, K. Zhu
PKU/IHIP, Beijing, People's Republic of China

Funding: Project supported by the National Natural Science Foundation of China (Grant No.10905003) and China Postdoctoral Science Foundation.
There is always high interest to study material irradiation damage effects based on accelerators. The bombardment of solids with high energy particles causes some changes in many important engineering properties. By implanting helium ions, it may be possible to simulate the damage process occurs in vessels and unravel the complexμstructural andμchemical evolutions that are expected in advanced nuclear energy systems. A materials irradiation facility based on coupled RFQ-SFRFQ accelerator will be built in Peking University, attribute to the commissioning of prototype SFRFQ accelerator, we have coupled the SFRFQ electrodes and the traditional RFQ electrodes in one cavity to form a more compact accelerator which can provide helium beam with energy of 0.8MeV for materials irradiation research.

THPPC015

Design of a Four-vane 325 MHz RFQ Cold Model at Tsinghua University

rfq, dipole, resonance, simulation

3308

L. Du, J.C. Cai, X. Guan, Q.Z. Xing
TUB, Beijing, People's Republic of China

Funding: Work supported by National Natural Science Foundation of China (Project 11175096).
The design of a Radio Frequency Quadrupole (RFQ) accelerator cold model at Tsinghua University is presented in this paper. The 1-meter-long aluminium cold model is chosen to be the same as the low-energy part of the 3-meter-long RFQ for the Compact Pulsed Hadron Source (CPHS) project at Tsinghua University. This cold model will be used mainly for the RFQ field study and education. It will work at the RF frequency of 325 MHz. All the simulations are finished by the SUPERFISH and MAFIA codes.

THPPC020

Accurate Measurement of Ferrite Garnets to be used for Fast-tuned Ferrite Loaded Cavities in the Range of 20-40 MHz

impedance, resonance, vacuum, dipole

3317

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

For the implementation of ferrite-tuned cavities with perpendicular biased ferrites in the frequency range of 20 to 40 MHz, different types of ferrite garnets were evaluated in terms of their electromagnetic properties. We describe a precision measurement method applicable to small-sized ferrite samples of 1-square-inch surface and 2 mm thickness in the given frequency range. During measurement, these samples are exposed to varying magnetic bias fields of different orientations. Two different techniques for the determination of the real and the imaginary part of the permeability are required to achieve sufficiently accurate results. We present a detailed description of these methods as well as results obtained.

THPPC021

A Microwave Paraphoton and Axion Detection Experiment with 300 dB Electromagnetic Shielding at 3 GHz

photon, shielding, coupling, pick-up

3320

M. Betz, F. Caspers
CERN, Geneva, Switzerland

Funding: Work supported by the Wolfgang-Gentner-Programme of the Bundesministerium für Bildung und Forschung (BMBF).
For the microwave equivalent of "light shining through the wall" (LSW) experiments, a sensitive microwave detector and very high electromagnetic shielding is required. The screening attenuation between the axion-generating cavity and the nearby detection-cavity should be greater than 300 dB, in order to push beyond the presently existing exclusion limits. To achieve these goals in practice, a "box in a box" concept was utilized for shielding the detection-cavity, while a vector signal analyzer was used as a microwave receiver with a very narrow resolution bandwidth in the order of a few micro-Hz. This contribution will present the experimental layout and show the results to date.

THPPC023

RF Loads for Energy Recovery

synchrotron, vacuum, coupling, proton

3326

S. Federmann, M. Betz, F. Caspers
CERN, Geneva, Switzerland

Different conceptional designs for RF high power loads are presented. One concept implies the use of solid state rectifier modules for direct RF to DC conversion with efficiencies beyond 80%. In addition, robust metallic low-Q resonant structures, capable of operating at high temperatures (>150 ̊C) are discussed. Another design deals with a very high temperature (up to 800 ̊C) air cooled load using a ceramic foam block inside a metal enclosure. This porous ceramic block is the actual microwave absorber and is not brazed to the metallic enclosure.

THPPC024

Design, Construction and Power Conditioning of the First C-band Test Accelerating Structure for SwissFEL

klystron, linac, vacuum, impedance

3329

R. Zennaro, J. Alex, H. Blumer, M. Bopp, A. Citterio, T. Kleeb, L. Paly, J.-Y. Raguin
Paul Scherrer Institut, Villigen, Switzerland

The SwissFEL C-band linac will consist of 26 RF modules with a total acceleration voltage of 5.4 GV. Each module will be composed of a single 50 MW klystron and its solid-state modulator feeding a pulse compressor and four two-meter long accelerating structures. PSI has launched a vigorous R&D program of development of the accelerating structures including structure design, production and high-power RF tests. The baseline design is based on ultra-precise cup machining to avoid dimple tuning. The first test structure is a constant impedance structure composed of eleven double-rounded cups. We report here on the structure design, production, low-level RF measurements, high-power conditioning and breakdown analysis.

THPPC025

Improvements to ISIS RF Cavity Tuning

acceleration, controls, synchrotron, proton

3332

R.J. Mathieson, D. Bayley, N.E. Farthing, I.S.K. Gardner, A. Seville
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The ISIS facility at the Rutherford Appleton Laboratory in the UK routinely accelerates proton beam currents in excess of 230 uA to run two neutron spallation target stations. The accelerator consists of a 70 MeV H⁻ linac and an 800 MeV, 50 Hz, proton synchrotron. The synchrotron beam is accelerated using six fundamental (h=2), and four second harmonic (h=4) ferrite loaded RF cavities each having its own drive amplifier and bias system. Each RF cavity is driven as a high Q tuned RF circuit; the resonant frequency being controlled by biasing the ferrite using a current from the bias regulator system. The cavity is kept at the correct resonant frequency by an analogue feedback loop comparing the phase of the cavity voltage to the phase of the demand voltage at the amplifier, and a 50Hz digital correction function calculated from the estimated frequency response of the system. This paper describes work improving the performance of the tuning system by introducing better system identification of the tuning loop and a time varying transfer function.

THPPC026

A Transverse Deflecting Cavity for the Measurement of Short Low Energy Bunches at EBTF

coupling, electron, simulation, impedance

3335

G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
S.R. Buckley, P. Goudket, C. Hill, P.A. McIntosh, J.W. McKenzie, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The Electron Beam Test Facility (EBTF) at Daresbury Laboratory will deliver low energy (5/6 MeV) short bunches (~40 fs) to a number of industrial experimental stations and for scientific research. In order to measure the longitudinal profile of the bunch an S-band transverse deflecting cavity will be inserted into the beamline. A transverse kick of around 5 MV is required hence a 9 cell design has been chosen. The design of the transverse deflecting cavity has been influence by the competing demands of high RF efficiency and minimising the unwanted transverse kick at the entrance and exit of the cavity which cause the electrons to be displaced while traversing the cavity. This has led to a shortened end cell structure design to minimise the kick applied at the entrance and exit to the cavity. In order to minimise the impact of the input coupler a dummy waveguide has been placed on the opposing side of the cavity to minimise the monopole component of the RF fields in the coupling cell. The coupler is located at the central cell of the cavity to avoid exciting the nearby modes. Tracking of the beam is performed in GPT including space charge, due to the low energy of the electrons.

THPPC028

Kinetic Modeling of RF Breakdown in High-Pressure Gas-filled Cavities

simulation, plasma, electron, vacuum

3341

D. Rose, C.H. Thoma
Voss Scientific, Albuquerque, New Mexico, USA
J.M. Byrd, D. Li
LBNL, Berkeley, California, USA
R.P. Johnson, M.L. Neubauer, R. Sah
Muons, Inc, Batavia, USA
A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, USA

Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86352
Recent studies have shown that high gradients can be achieved quickly in high-pressure gas-filled cavities 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 radiofrequency and surface preparation. A series of experiments at 805 MHz using hydrogen fill pressures up to 0.01 g/cm³ of H2 have demonstrated high electric field gradients and scaling with the DC Paschen law limit, up to ~30 MV/m, depending on the choice of electrode material. For higher field stresses, the breakdown characteristics deviate from the Paschen law scaling. Fully-kinetic 0D collisional particle-in-cell (PIC) simulations give breakdown characteristics in H2 and H2/SF6 mixtures in good agreement with the 805 MHz experimental results below this field stress threshold. The impact of these results on gas-filled RF accelerating cavity design will be discussed.

THPPC029

High-power Waveguide Dampers for the Short-Pulse X-Ray Project at the Advanced Photon Source

HOM, damping, vacuum, cryomodule

3344

G.J. Waldschmidt, B. Brajuskovic, J. Liu, M.E. Middendorf, A. Nassiri, T.L. Smith, G. Wu
ANL, Argonne, USA
J. Henry, J.D. Mammosser, R.A. Rimmer, M. Wiseman
JLAB, Newport News, Virginia, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
High-power waveguide dampers have been designed and prototyped for the Short-Pulse X-ray (SPX) cavities at the Advanced Photon Source. The cavities will operate at 2.815 GHz and utilize the TM110 dipole mode. As a result, higher-order (HOM) and lower-order mode (LOM) in-vacuum dampers have been designed to satisfy the demanding broadband damping requirements in the APS storage ring. The SPX single-cell cavity consists of two WR284 waveguides for damping the HOMs and one WR284 waveguide for primarily damping the LOM where up to 2kW will be dissipated in the damping material. The damper designs and high-power experimental results will be discussed in this paper.

THPPC030

Multi-physics Analysis of the Fermilab Booster RF Cavity

booster, proton, injection, extraction

3347

M.H. Awida, M.S. Champion, T.N. Khabiboulline, V.A. Lebedev, J. Reid, V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
After about 40 years of operation the RF accelerating cavities in Fermilab Booster need an upgrade to improve their reliability and to increase the repetition rate in order to support a future experimental program. An increase in the repetition rate from 7 to 15 Hz entails increasing the power dissipation in the RF cavities, their ferrite loaded tuners, and HOM dampers. The increased duty factor requires careful modelling for the RF heating effects in the cavity. A multi-physic analysis investigating both the RF and thermal properties of Booster cavity under various operating conditions is presented in this paper.

THPPC031

Commissioning of a 1.3-GHz Deflecting Cavity for Phase-Space Exchange at the Argonne Wakefield Accelerator

wakefield, klystron, simulation, diagnostics

3350

P. Piot
Fermilab, Batavia, USA
M.E. Conde, W. Gai, C.-J. Jing, R. Konecny, W. Liu, J.G. Power, Z.M. Yusof
ANL, Argonne, USA
D. Mihalcea, M.M. Rihaoui
Northern Illinois University, DeKalb, Illinois, USA

Funding: Work supported by DOE awards FG-02-08ER41532 and DE-AC02-06CH11357.
A 1/2-1-1/2 cell normal-conducting 1.3-GHz deflecting cavity was recently installed at the Argonne Wakefield Accelerator. The cavity will soon be included in a transverse-to-longitudinal phase space exchanger that will eventually be used to shaped the current profile of AWA electron bunches in support of dielectric wakefield experimentS with enhanced transformer ratio. In this paper we report on the initial commissioning of the deflecting cavity including rf-conditioning and beam-based measurement of the deflecting strength.

THPPC032

Conditioning and Future Plans for a Multi-purpose 805 MHz Pillbox Cavity for Muon Acceleration

vacuum, acceleration, solenoid, linac

3353

G.M. Kazakevich, A. Dudas, G. Flanagan, R.P. Johnson, F. Marhauser, M.L. Neubauer, R. Sah
Muons, Inc, Batavia, USA
S.S. Kurennoy
LANL, Los Alamos, New Mexico, USA
A. Moretti, M. Popovic, G.V. Romanov, K. Yonehara
Fermilab, Batavia, USA
Y. Torun
IIT, Chicago, Illinois, USA

Funding: Supported in part by grant 4735 · 10 LANL and Dept. of Energy STTR grant DE-FG02-08ER86352.
An 805 MHz RF pillbox cavity has been designed and constructed to investigate potential muon beam acceleration and cooling techniques for a Muon Collider or Neutrino Factory. The cavity can operate in vacuum or under pressure to 100 atmospheres, at room temperature or in a liquid nitrogen bath at 77 K. The cavity has been designed for easy assembly and disassembly with bolted construction using aluminum seals. To perform vacuum and high pressure breakdown studies of materials and geometries most suitable for the collider or factory, the surfaces of the end walls of the cavity can be replaced with different materials such as copper, aluminum, beryllium, or molybdenum, and with different geometries such as shaped windows or grid structures. The cavity has been designed to fit inside the 5-Tesla solenoid in the MuCool Test Area at Fermilab. In this paper we present the vacuum conditioning results and discuss plans for testing in a 5-Tesla magnetic field. Additionally, we discuss the testing plan for beryllium (a material research has shown to be ideal for the collider or factory) end walls.

THPPC033

Progress on a Cavity with Beryllium Walls for Muon Ionization Cooling Channel R&D

coupling, electron, vacuum, simulation

3356

D.L. Bowring, A.J. DeMello, A.R. Lambert, D. Li, S.P. Virostek, M.S. Zisman
LBNL, Berkeley, California, USA
D.M. Kaplan
Illinois Institute of Technology, Chicago, Illinois, USA
R.B. Palmer
BNL, Upton, Long Island, New York, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The Muon Accelerator Program (MAP) collaboration is working to develop an ionization cooling channel for future muon colliders. The ionization cooling channel requires the operation of high-gradient, normal-conducting RF cavities in solenoidal magnetic fields up to 5 T. However, experiments conducted at Fermilab's MuCool Test Area (MTA) show that increasing the solenoidal field strength reduces the maximum achievable cavity gradient. This gradient limit is characterized by an RF breakdown process that has caused significant damage to copper cavity interiors. The damage is likely caused by field-emitted electrons, focused by the solenoidal magnetic field onto small areas of the inner cavity surface. Local heating may then induce material fatigue and surface damage. Fabricating a cavity with beryllium walls would mitigate this damage due to beryllium's low density, low thermal expansion, and high electrical and thermal conductivity. This poster addresses the design and fabrication of a pillbox RF cavity with beryllium walls, in order to evaluate the performance of high-gradient cavities in strong magnetic fields.

THPPC034

Design and Analysis of the PXIE CW Radio-frequency Quadrupole (RFQ)

rfq, controls, quadrupole, vacuum

3359

S.P. Virostek, M.D. Hoff, A.R. Lambert, D. Li, J.W. Staples
LBNL, Berkeley, California, USA
G.V. Romanov
Fermilab, Batavia, USA
C. Zhang
IAP, Frankfurt am Main, Germany

Funding: This work is supported by the Office of Science, United States Department of Energy under DOE contract DE-AC02-05CH11231.
The Project X Injector Experiment (PXIE) will be a prototype front end of the Project X accelerator proposed by Fermilab. PXIE will consist of an H⁻ ion source, a low-energy beam transport (LEBT), a radio-frequency quadrupole (RFQ) accelerator, a medium-energy beam transport (MEBT) and a section of superconducting cryomodules that will accelerate the beam from 30 keV to 30 MeV. LBNL has developed an RFQ design for PXIE with fabrication scheduled to begin before the end of CY 2012. The chosen baseline design is a four-vane, 4.4 m long CW RFQ with a resonant frequency at 162.5 MHz (2.4 wavelengths long). The RFQ will provide bunching and acceleration of a nominal 5 mA H⁻ beam to 2.1 MeV. The relatively low wall power density results in wall power losses that are less than 100 kW. The beam dynamics design has been optimized to allow for more than 99% beam capture with exceptionally low longitudinal emittance. The RFQ mechanical design and the results of RF and thermal analyses are presented here.

THPPC036

The Alpha Ferrite-loaded Coaxial Resonator Cavity

damping, resonance, storage-ring, radiation

3365

A.N. Pham, S.-Y. Lee, T.H. Luo
IUCEEM, Bloomington, Indiana, USA

Funding: Grant N00164-08-GM03 P00004 from the NSWC Crane Division, DOE Grant DE-FG02-92ER40747, and NSF Grant PHY-0852368 (IU: 48-432-31).
The Advanced Electron Photon Facility (ALPHA)*,** is a joint collaboration between the Indiana University Center for Exploration of Energy and Matter and the Crane Naval Surface Warfare Center. The ALPHA storage ring will serve as a debuncher in single pass mode of operation. With a set of two gradient damping wigglers, the storage ring can also accumulate to achieve high charge density beams. In this report, we present the design, fabrication, and testing of the 15 MHz ferrite-loaded quarter-wave rf coaxial resonator cavity that will be utilized in the ALPHA storage ring. Topics pertaining to beam lifetime, radiation damping, ferrite-loaded transmission lines, and key cavity parameters will be discussed.
* S.Y. Lee, P.E. Sokol, et al, "The ALPHA Project at IU CEEM," Proceedings of the IPAC2010.
** S.Y. Lee, et al, "A low energy electron storage ring with tunable compaction factor," RSI 78, 2007.

THPPC040

Improved RF Design for an 805 MHz Pillbox Cavity for the US MuCool Program

coupling, simulation, ion, multipactoring

3371

Z. Li, C. Adolphsen, L. Ge
SLAC, Menlo Park, California, USA
D.L. Bowring, D. Li
LBNL, Berkeley, California, USA

Funding: Work supported by US DOE under contract number DE-AC02-05CH11231, and DE-AC02-76SF00515.
Normal conducting RF cavities are required to operate at high gradient in the presence of strong magnetic field in muon ionization cooling channels for a Muon Collider. Experimental studies using an 805 MHz pillbox cavity at MTA of Fermilab has shown significant degradation in gradient performance and damage in the regions that are correlated with high RF fields in magnetic field up to 4 Tesla. These effects are believed to be related to the dark current and/or multipacting activities in the presence of external magnetic field. To improve the performance of the cavity, a new RF cavity with significantly lower surface field enhancement was designed, and will be built and tested in the near future. Numerical analyses of multipacting and dark current were performed using the 3D parallel code Track3P for both the original and new improved cavity profiles in order to gain more insight in understanding of the gradient issues under strong external magnetic field. In this paper, we will present the improved RF design and the dark current and multipacting analyses for the 805 MHz cavity.

THPPC041

704 MHz Fast High-power Ferroelectric Phase Shifter for Energy Recovery Linac Applications

coupling, controls, linac, pulsed-power

3374

S.V. Shchelkunov
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield
Omega-P, Inc., New Haven, USA
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
S. Kazakov, V.P. Yakovlev
Fermilab, Batavia, USA
A.B. Kozyrev
LETI, Saint-Petersburg, Russia
E. Nenasheva
Ceramics Ltd., St. Petersburg, Russia

Funding: Research supported by the U.S. Department of Energy, Office of High Energy Physics
Development, tests, and evaluation of a fast electrically-controlled 704 MHz tuner for Energy Recovery Linacs that employs an electrically -controlled ferroelectric component are presented. The tuner is a refinement of an already tested prototype described elsewhere. In the new concept, a collection of ferroelectric assemblies behave as cavities configured as transmission components within a coaxial waveguide. Each assembly is based on a ring-like ferroelectric ceramic with its height, inner and outer diameters, and the shape of edges adjusted to insure a clean operating mode, and relatively low field strength. Several assemblies serve to widen the passband and increase tunability. The tuner is to deliver fast (~100-200 ns) phase adjustment from 0-to-100 degrees when biased by voltages from 0-to-15kV; the design promises to handle 50 kW CW and 900 kW of pulsed power. A scaled version is also considered to operate at 1300 MHz while handling 500 kW of pulsed power. Our latest findings, related issues, and plans for experiments are discussed.

THPPC042

Modified Magnicon for High-Gradient Accelerator R&D

gun, electron, solenoid, cathode

3377

S.V. Shchelkunov, Y. Jiang, M.A. LaPointe
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield
Omega-P, Inc., New Haven, USA
V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Research supported by the U.S. Department of Energy, Office of High Energy Physics
A self-consistent design is described of a modified 34.3 GHz magnicon amplifier with a TE311-mode output cavity, to replace the existing magnicon at Yale Beam Physics Lab Test Facility whose output cavity operates in the TM310 mode. The main goal for the new design is to achieve robust reliable operation. This is expected since tube performance – according to simulations – is largely insensitive to the magnitude of external dc magnetic fields, including imperfections in magnetic field profile; small changes in gun voltage and current; changes in electron beam radial size; and even poorly matched external circuitry. The new tube, as with its predecessor, is a third harmonic amplifier, with drive and deflection gain cavities near 11.424 GHz and output cavity at 34.272 GHz. The design calculations predict stable output of power of 20-27 MW at a 10 Hz repetition rate in pulses up to 1.3 μs long, with a low probability of breakdown in the output cavity because of low electric fields (less than 650 kV/cm).

THPPC043

Cold Test of an L-band, 2-Cell PWT Photoelectron

gun, simulation, vacuum, electron

3380

Y. Luo, D. Yu
DULY Research Inc., Rancho Palos Verdes, California, USA
R. Andrews, T.N. Khabiboulline
Fermilab, Batavia, USA

Funding: DOE SBIR Grant No. DE-FG02-06ER84460
An L-band, 1+2/2-cell PWT gun with a coax coupler has been designed for high vacuum polarized electron source applications by DULY Research Inc. A cold test model was fabricated and is currently undergoing test at Fermilab, where the gun will eventually be hot tested. The aluminum cold test model includes an rf/ vacuum sieve, 2 disks, endplates, 6 supporting rods and a 6” CF flange, clamped together during testing. Fermilab made measurements for the cavity resonant frequency and axial field distribution using bead pull. To measure the resonant frequency of the cavity small diameter probes are placed through the vacuum sieve slot. A larger diameter probe can be used as an active tuner. This paper presents the results of the cold test and compares measurements with simulation results from 3D SLAC code Omega3p. The axial field distributions are in good agreement with each other. Frequency deviation is less than 0.5%, well within the experimental accuracy.

THPPC044

Development of the Dual Slot Resonance Linac

linac, coupling, resonance, impedance

3383

N. Barov, X. Chang, R.H. Miller, D.J. Newsham
Far-Tech, Inc., San Diego, California, USA

Funding: Work supported by DOE Grant DE-FG02-08ER85034
We report the status of the Dual Slot Resonance (DSR) linac under development by FAR-TECH. In this linac type, cell-to-cell coupling is provided by a pair of close-coupled resonant slots, resulting in very strong coupling vs. a typical side-coupled linac design, as well as a much more compact radial space requirement. We discuss the status of the structure fabrication, the RF distribution system, and installation and testing at the UCLA Pegasus facility.

THPPC045

Rapidly Tunable RF Cavity for Accelerators

acceleration, synchrotron, vacuum, simulation

3386

D.J. Newsham, N. Barov
Far-Tech, Inc., San Diego, California, USA

Funding: Work supported by the DOE-SBIR program, High Energy Physics Department.
The performance and range efficient use of rapidly cycling accelerators would be improved with the fast frequency tuning and associated variable phase change provided by a tunable rf cavity. The progress in developing a cavity that can be tuned by as much as 10 percent in frequency in less than 100 nanoseconds is presented.

THPPC046

Normal Conducting Radio Frequency x-band Deflecting Cavity Fabrication and Validation

alignment, electron, vacuum, linear-collider

3389

R.B. Agustsson, L. Faillace, A.Y. Murokh, S. Storms
RadiaBeam, Santa Monica, USA
D. Alesini
INFN/LNF, Frascati (Roma), Italy
V.A. Dolgashev
SLAC, Menlo Park, California, USA
J.B. Rosenzweig
UCLA, Los Angeles, California, USA
V. Yakimenko
BNL, Upton, Long Island, New York, USA

Funding: U.S. DOE SBIR grant DE-FG02-05ER84370
An X-band Traveling wave Deflector mode cavity (XTD) has been developed and fabricated at Radiabeam Technologies to perform longitudinal characterization of the sub-picosecond ultra-relativistic electron beams. The device is optimized for the 100 MeV electron beam parameters at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory, and is scalable to higher energies. An XTD is designed to operate at 11.424 GHz, and features short filling time, femtosecond resolution, and a small footprint. RF design, structure fabrication, cold testing results and commissioning plans are presented.

THPPC049

Progress on the MICE 201 MHz RF Cavity at LBNL

simulation, coupling, resonance, electron

3398

T.H. Luo, D.J. Summers
UMiss, University, Mississippi, USA
A.J. DeMello, D. Li, S.P. Virostek, M.S. Zisman
LBNL, Berkeley, California, USA

The international Muon Ionization Cooling Experiment (MICE) aims at demonstrating transverse cooling of muon beams by ionization. The ionization cooling channel of MICE requires eight 201-MHz normal conducting RF cavities to compensate for the longitudinal beam energy loss in the cooling channel. In this paper, we present recent progresses on MICE RF cavity at LBNL, which includes electro-polishing, intended to improve the cavity performance in the presence of strong external magnetic field; low power RF measurements on resonant frequency and Q value of each cavity with a pair of curved- beryllium windows to terminate the cavity irises. Multipacting simulations are conducted using SLAC’s ACE-3P code to study the effects in the cavity and coupler regions with the influence by external magnetic field.

THPPC053

First Experience at ELBE with the New 1.3 GHz CWRF Power System Equipped with 10 kW GHz Solid State Amplifiers (SSPA)

klystron, radiation, electron, linac

3407

H. Büttig, A. Arnold, A. Büchner, M. Justus, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig, G.S. Staats, J. Teichert
HZDR, Dresden, Germany

The superconducting CW- LINAC (1.3 GHz) of the radiation source ELBE is in permanent operation since May 2001/1/. During the winter shut-down 2011 - 1212 an upgrade program of ELBE was realized. One part of the program was to double the RF-power per cavity using two 10 kW Solid State Amplifiers in parallel per cavity. The poster gives an overview on the new RF-system and the experience gained within the first three months of operation.

THPPC056

Development of 12kW RF Power Supply for CYCHU-10 Cyclotron

power-supply, cyclotron, feedback, impedance

3416

D. Li, T. Hu, J. Huang, K.F. Liu, B. Qin, J. Yang, L. Yang
Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China

One 12kW RF power supply has been developed for CYCHU-10, which is a 10 MeV cyclotron developed in Huazhong University of Science and Technology (HUST). A high performance DDS chip AD9859 is used to synthesize RF signal in this power supply, which is easy to change the output frequency. The centre frequency is 101MHz, and the frequency bandwidth is more than 1MHz. The RF power supply could operate in fine searching mode, coarse searching mode, tracking mode, and so on. It could search the resonant frequency of cavity with the frequency control loop. The final stage amplifier using a triode 3CW20,000H7 operates in grounded grid configuration, which is stable and reliable. The performance test using a 50Ω resistor load has finished, and major results are shown in this paper.

THPPC057

S-band High Power RF System for 10 GeV PAL-XFEL

coupling, simulation, klystron, linac

3419

W.H. Hwang, J.Y. Huang, Y.D. Joo, H.-S. Kang, H.-G. Kim, S.H. Kim, H.-S. Lee, Y.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea

In PAL, We are constructing a 10GeV PxFEL project. The output power of the klystron is 80 MW at the pulse width of 4 ㎲ and the repetition rate of 120 Hz. In high power operation, it is important to decrease the rf electric field to protect rf break-down in high power rf components. To obtain the maximum beam, we must reduce the phase difference between waveguide branches including accelerating structure and minimize the environment influences. This paper describes the waveguide system and high power rf components for the PxFEL.

THPPC059

Design of SLED System with Dual Side-wall Coupling Irises and Biplanar Power Splitter for PAL XFEL

coupling, simulation, klystron, factory

3425

Y.D. Joo, I. Hwang, C. Kim, B.-J. Lee
PAL, Pohang, Kyungbuk, Republic of Korea

The SLED system of the PAL XFEL is required to be operated with the RF input power of 80 MW and the pulse width of 4 us. The high RF dose from the RF breakdown at the coupling holes and power splitter prohibits that the original design of the SLED serve this operation condition. To reduce the gradient at the cavity coupling structure, the concept of dual side-wall coupling irises is introduced. In addition, the 3dB splitter is modified with the concept of biplanar coupler structure.

THPPC062

CPI 100kW Klystrons Operation Experiences in NSRRC

klystron, factory, cathode, power-supply

3434

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

In 2004, NSRRC had decided to upgrade its traditional copper cavity in storage ring of Taiwan Light Source (TLS) to superconducting cavity for higher beam current, brighter X-ray and more insertion devices. To achieve this, the RF power source-the klystron had been upgraded by intensive cooperation with CPI (Communication & Power Industries) from 70 kW to 100 kW. The same 100 kW klystron would then be also adopted as the RF source in booster in TPS plan. There are total five 100kW CPI klystrons with Model number of VKB-7953B as the power amplifiers in RF facility of NSRRC. Four of the five klystrons have been tested in detail as basic characteristic understanding in custom test stand. Some encountered phenomenon in testing period would be discussed here. In conclusion, these klystrons from CPI is quite load VSWR sensitive while the performance has large difference between them.

THPPC063

Commission of RF Power Sources and its Auxiliary Components for TPS in NSRRC

klystron, feedback, controls, synchrotron

3437

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

Since 2010, before the starting the construction of TPS building in NSRRC, the intensive testing activities for RF facility has begun in RF lab. The RF facility includes 300kW transmitters, 350kW ferrite loads and 350kW circulators with the corresponding LLRF prototype system. Some unexpected situation happened, such as HV weak transformers and loosen greased ferrite tiles during the commission of the 300kW transmitter. Those situation are all encountered during long-term reliability test. For a high availability of beam light in TPS, the highly reliable sub-systems are the basic requirement and hence, long-term reliability is so essential during commission period. Then, the high power circulators for safe RF operation are also tested for various phases change at cavity port. The temperature compensation unit plays key role in proper operation of circulator. Some noticeable test procedure and results would also be introduced as the present RF system progress of TPS plan in NSRRC.

THPPC065

Phase and Frequency Locked Magnetron

shielding, controls, interaction-region, cathode

3440

M.L. Neubauer, A. Dudas, R. Sah
Muons, Inc, Batavia, USA
A. Moretti, M. Popovic
Fermilab, Batavia, USA

Funding: Supported in part by SBIR Grant 4724 · 09SC02766
Phase and Frequency locked magnetrons have many important uses from phased array ground penetrating radars to SRF sources. We report on the recent progress in making such a magnetron. The ferrite/garnet material has passed bakeout and outgassing tests with outgassing rates well below the requirements. The magnetic field requirements for adjusting the frequency by changing the microwave properties of the ferrite/garnet have been determined. The design of the anode structure with ferrites, magnetic shielding, and magnetic bias has been completed for a low power test. We report on the design status. Muons, Inc. has negotiated an contract with a manufacturing firm, L-3 Electron Devices California Tube Laboratory, Inc., to be the Manufacturing Partner for the commercialization of this technology and support these Phase II efforts.

THPPC066

Adjustable High Power Coax RF Coupler without Moving Parts

coupling, extraction, solenoid

3443

M.L. Neubauer, A. Dudas, R. Sah
Muons, Inc, Batavia, USA
A. Nassiri
ANL, Argonne, USA

A high power fundamental RF power coupler (FPC) with an adjustable in situ coupling factor would be highly desirable for a number of applications; for example, the 352 MHz light source at APS and Project X. A Phase I project has been completed with a prototype constructed and modeled. The prototype includes a coaxial TEE with two windows a quarter wavelength apart, and a ferrite tuner. Two materials were tested and their characteristics measured in terms of loss and magnetic field requirements to produce the desired change in coupling. A VSWR of better than 1.05:1 and a bandwidth of at least 8% at 1.15:1 was measured. The tradeoffs of a final design are proposed based upon these results.

THPPC069

Design, Test and Implementation of New 201.25 MHz Power Amplifier for the LANSCE Linac

cathode, DTL, electron, HOM

3446

J.T.M. Lyles, Z. Chen, J. Davis, A.C. Naranjo, D. Rees, G. M. Sandoval, Jr.
LANL, Los Alamos, New Mexico, USA
D. Baca, R.E. Bratton, R.D. Summers
Compa Industries, Inc., Los Alamos, New Mexico, USA
N.W. Brennan
Texas A&M University, College Station, Texas, USA

Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396
A new 201.25 MHz final power amplifier (FPA) has been designed, fabricated, and tested at Los Alamos Neutron Science Center (LANSCE). The prototype FPA has produced 3 MW peak and 250 kW of mean power with 15 dB of power gain and over 60% efficiency. It has been tested for several thousand hours with a load. A Thales TH628 Diacrode® electron tube is key to the performance of the new amplifier. It is configured with a full wavelength output circuit, having the lower main tuner situated ¾λ from the central electron beam region in the tube and the upper slave tuner ¼λ from the same point. The FPA is designed with input and output transmission line cavity circuits, grid decoupling circuits, an adjustable output coupler, DC blocking and RF bypassing capacitors, HOM suppressors, and a cooling system. A pair of production amplifiers are planned to be power-combined for up to 3.6 MW peak power at high duty factor. Three of these combined amplifiers will be installed in place of the original 1968-vintage amplifiers to return LANSCE operation to 12% beam duty factor with higher peak current than presently possible.

THPPC071

The Use of a Solid State Analog Television Transmitter as a Superconducting Electron Gun Power Amplifier

gun, electron, controls, LLRF

3452

J.G. Kulpin, K.J. Kleman
UW-Madison/SRC, Madison, Wisconsin, USA
R.A. Legg
JLAB, Newport News, Virginia, USA

Funding: The electron gun program is supported by DOE award DE-SC0005264, and the University of Wisconsin, Madison.
A solid state analog television transmitter designed for 200 MHz operation is being commissioned as a radio frequency power amplifier on the Wisconsin superconducting electron gun cavity. The amplifier consists of three separate radio frequency power combiner cabinets and one monitor and control cabinet. The transmitter employs rugged field effect transistors built into one kilowatt drawers that are individually hot swappable at maximum continuous power output. The total combined power of the transmitter system is 33 kW at 200 MHz, output through a standard coaxial transmission line. A low level radio frequency system is employed to digitally synthesize the 200 MHz signal and precisely control amplitude and phase.

THPPC075

Development of a Digital Low-level RF Control System for the p-Linac Test Stand at FAIR

controls, linac, low-level-rf, proton

3461

M. Konrad, U. Bonnes, C. Burandt, R. Eichhorn, J. Enders, P.N. Nonn, N. Pietralla
TU Darmstadt, Darmstadt, Germany

Funding: Work supported by DFG through CRC 634 and by the BMBF under 06 DA 9024 I
A test stand for a proton Linac is currently built at GSI in the context of the FAIR project. Its low-level RF control system will be based on a system that has been developed for the S-DALINAC at TU Darmstadt operating at 3 GHz. This system converts the RF signal coming from the cavity down to the base band using a hardware I/Q demodulator. The base-band signals are digitized by ADCs and fed into an FPGA. A custom CPU implemented in the FPGA executes the control algorithm. The resulting signals are I/Q modulated before they are sent back to the cavity. The RF module has to be adapted to the p-LINAC's operating frequency of 325 MHz. Moreover, the p-LINAC will run in pulsed operation whereas the S-DALINAC is operated in CW mode. Different quality factors of the cavities and the pulsed operation require a redesign of the control algorithm. We will report on the modifications necessary to adapt the S-DALINAC's control system to the p-LINAC test stand and on first results obtained from tests with a prototype.

THPPC076

Comparison of LLRF Control Approaches for High Intensity Hadron Synchrotrons: Design and Performance

controls, feedback, beam-loading, synchrotron

3464

K. Gross, J. Adamy
TU Darmstadt, RTR, Darmstadt, Germany

Funding: Federal Ministry of Education and Research
A usual and effective way to realize closed-loop controllers is to use cascaded SISO feedback and to rely on some kind of linear PID structure with parameters adjusted manually in simulations or experiments. Such a control may not reach optimal performance if the system is coupled or non-linear. Regarding intense beams, longitudinal beam loading can be compensated by detuning. But the coupling between phase and amplitude (or I and Q component) highly depends on the tuning, that is on the resonant frequency of the cavity. It is derived that cavity and beam dynamics thus show bi-linear nature, i.e. belong to a well investigated class of non-linear systems with appropriate control strategies available*. Different controller designs are compared in terms of performance but also design transparency, the need of previous knowledge like the expected magnitude of beam loading and adaptability to different conditions, e.g. during acceleration or if applied to the full range of ion species as at GSI. The performance evaluation is based on macro-particle tracking simulations. In particular avail and limits of an optimal (quadratic cost) MIMO controller for bi-linear systems are shown**.
* H.K. Khalil: Nonlinear Systems, 3rd Edition, Prentice-Hall, 2002
** Z. Aganović, Z. Gajić: Linear Optimal Control of Bilinear Systems, Springer-Verlag, 1995.

THPPC077

Resonance Control of Superconducting Cavities at Heavy Beam Loading Conditions

controls, beam-loading, resonance, LLRF

3467

M.K. Grecki, S. Pfeiffer
DESY, Hamburg, Germany

Funding: The research leading to these results has received funding from the European Commission under the EuCARD FP7 Research Infrastructures grant agreement no. 227579
The SC cavities operated at high Q level need to be precisely tuned to the RF frequency*. Well tuned cavities assure the good field stability and require minimum level of RF power to reach the operating gradient level. The TESLA cavities at FLASH are tuned with the help of slow (step motors) and fast (piezo) tuners driven by the control system**. The goal of this control system is to keep the detuning of the cavity as close to zero as possible in the presence of disturbing effects (Lorentz force detuning and microphonics). The detuning of the cavity can be determined using a few measurement methods. The most common is to measure detuning from the phase derivative at the end of the RF pulse. In order to calculate the detuning during the whole RF pulse the cavity equation must be solved taking into account all the driving forces (RF power delivered to the cavity and beam contribution). This in not the trivial task, particularly in the heavy beam conditions, since all signals must be precisely calibrated. This work presents the methods and algorithms to evaluate and control the detuning of the superconducting cavities in the heavy beam loading conditions adequate for ILC operation.
* Grecki M., Piezo operation experience at FLASH, LLRF-2011, DESY, 09.2011
** Grecki M. et al. Piezo Control for Lorentz Force Detuned SC Cavities of DESY FLASH, IPAC'10, Kyoto, Japan, pp.1452-1454

THPPC079

Prototype Performance of Digital LLRF Control System for SuperKEKB

controls, LLRF, pick-up, feedback

3470

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

For the SuperKEKB project, a new LLRF control system has been developed to realize high accuracy and flexibility. It is an FPGA-based digital RF feedback control system using 16-bit ADC's, which works on the μTCA platform. In this μTCA-module, the Linux-OS runs then it performs as the EPICS-IOC. This LLRF system is available to both of normal-conducting cavity and super-conducting cavity. A prototype of the LLRF control system for the SuperKEKB was produced. The feedback control stability, temperature characteristics and cavity-tuner control performance are evaluated. The evaluation results and future issue for the operation will be presented in this report. The amplitude and phase stability in the feedback control is 0.03% and 0.02 degrees, respectively. It is sufficiently stable for the SuperKEKB. However, the temperature dependency is not small for the required stability. Its countermeasures are under consideration.

THPPC080

The Development of LLRF System at PAL

LLRF, controls, simulation, radio-frequency

3473

K.-H. Park, H.S. Han, Y.-G. Jung, D.E. Kim, H.-G. Lee, H.S. Suh
PAL, Pohang, Kyungbuk, Republic of Korea
J.-S. Chai, H.W. Kim, Y.S. Lee
SKKU, Suwon, Republic of Korea
B.-K. Kang
POSTECH, Pohang, Kyungbuk, Republic of Korea

The Super Conducting Radio Frequency (SCRF) systems will be installed for PLS-II. The PAL has been carrying out the design of the low level radio frequency (LLRF) system for the SCRF control using the digital technologies. The requirements of the LLRF system are to maintain the field stability in a cavity within ±0.75% in amplitude and 0.35° in phase. The LLRF system includes the analog front-end, analog and digital board (ADC, DAC, DSP, FPGA, etc.), clock generation and distribution, and so on. The control algorithm will be implemented by the VHDL. The hardware design of the LLRF for PLS-II, simulation and test results were described in the paper.

THPPC082

Control Performance Improvement by Using Feedforward in LLRF

controls, klystron, feedback, LLRF

3476

R. Zeng, D.P. McGinnis, S. Molloy
ESS, Lund, Sweden
A.J. Johansson
Lund University, Lund, Sweden

The LLRF design is ongoing at ESS (European Spallation Source). One major task of LLRF is to overcome a variety of perturbations such as klystron droop and ripple, Lorentz detuning and beam loading. These perturbations can be well suppressed by classical PI (proportional-integral) controller in feedback loop, but at a cost of raising risk of instability and consuming power overhead for overshoot. Since ESS is a green project focusing on energy efficiency, we will hence investigate in this paper some feedforward and advanced adaptive algorithms to deal with these perturbations, so as to improve the control performance and reduce the power overhead.

THPPC083

Investigation of Feedback Control for Klystron Ripple

feedback, klystron, controls, cathode

3479

R. Zeng, D.P. McGinnis, S. Molloy
ESS, Lund, Sweden
A.J. Johansson
Lund University, Lund, Sweden

At ESS (European Spallation Source), there might be potentially serious droop and ripple because of long RF pulse more than 3 ms. It is important for us to know to what extent the droop and ripple affects the klystron output, and how much we can tolerate. The variations of the phase and amplitude of klystron output due to the change in klystron cathode voltage is investigated in this Paper. The mechanism and the effectiveness of the feedback control to suppress the variations are given. To understand the limitation of the feedback, both proportional controller and proportional-integral controller used in feedback loop are simulated and analyzed respectively for superconducting cavity and normal conducting cavity. The tolerances of the droop and ripple in cathode voltage under feedback control are shown according to the data and results obtained.

THPPC084

LHC One-turn Delay Feedback Commissioning

feedback, klystron, LLRF, beam-loading

3482

T. Mastoridis, P. Baudrenghien, J.C. Molendijk
CERN, Geneva, Switzerland

The 1-turn delay feedback is an FPGA based feedback system part of the LHC cavity controller, which produces gain only around the revolution frequency harmonics. As such, it helps reduce the transient beam loading and effective cavity impedance. Consequently, it increases the stability margin for Longitudinal Coupled Bunch Instabilities driven by the cavity impedance at the fundamental and allows reliable operation at higher beam currents. The 1-turn delay feedback was commissioned on all sixteen cavities in mid-October 2011 and was used in operation for the rest of the run. The commissioning procedure and algorithms for setting-up are presented. The resulting improvements in transient beam loading, beam stability, and required klystron power are analyzed. The commissioning of the 1-turn delay feedback reduced the cavity voltage phase modulation from approximately six degrees peak-to-peak to below one degree at 400 MHz.

THPPC088

LLRF Control Algorithm for APEX

controls, LLRF, laser, monitoring

3488

G. Huang, K.M. Baptiste, J.M. Byrd, L.R. Doolittle, F. Sannibale
LBNL, Berkeley, California, USA

Advanced photo-cathode experiment is an ongoing experiment of a high repetition rate low emittance VHF band gun experiment. A low level RF control and monitor subsystem is developed base on the 5 LLRF4 board. One of them is used for low level RF control and the other 4 are used as interlock and RF monitor at different point of the system. The laser is also controlled by the system to be synced to the RF system. This paper we summarize the control algorithm used in the system firmware.

THPPC089

LLRF Control for SPX @ APS Demonstration Experiment

LLRF, controls, low-level-rf, resonance

3491

G. Huang, J.M. Byrd, K. Campbell, L.R. Doolittle, J.B. Greer
LBNL, Berkeley, California, USA
N.D. Arnold, T.G. Berenc, F. Lenkszus, H. Ma
ANL, Argonne, USA

The SPX experiment at APS is part of the APS upgrade project, using two deflecting cavity to chirp the electron pulse and then generate short pulse x-ray. To minimize the influence to other users on the storage ring, the phase synchronization of the two deflecting cavity are required to be better then 77 femto-second. A LLRF4 board based system is designed to demonstrate the capability of meeting this requirement. This paper discuss the hardware and firmware design of the demo experiment including the cavity emulator, frequency reference generation and LLRF control algorithm.

THPPC090

Robust Control of a Two-Input Two-Output (TITO) Multistate Cavity RF System ith Mismatched Uncertainty

controls, feedback, simulation, LLRF

3494

S. Kwon, M.S. Prokop, A. Scheinker
LANL, Los Alamos, New Mexico, USA

A RF cavity is well modeled as a linear two input two output (TITO) system in the Inphase/Quadrature (IQ) coordinates and is both controllable and observable. Whether it is due to the beam loading or Lorentz force detuning of a superconducting cavity, a cavity frequency detuning can be modeled as a matched uncertainty. The cavity field of a TITO cavity system with a matched uncertainty is controlled by output feedback or state feedback, whose error bound is made arbitrary small. Because of the building cost of the RF system, the single RF source (single klystron)-multicavity structure is sometimes used. This structure is described as a two-input multiple-output (TIMO) system. The control problem is not a simple extension of the single TITO system. Though the controllability and observability are preserved, the matched uncertainty of the TITO cavity system caused by cavity detuning becomes a mismatched uncertainty. The error bound of outputs is made arbitrary small by a control, only boundedness of the cavity fields of each TITO subsystem is guaranteed. In this paper, the properties of the TITO and the TIMO cavity RF systems are investigated.

THPPC093

SRF Cavity Surface Topography Characterization Using Replica Techniques

SRF, niobium, superconductivity, radio-frequency

3497

C. Xu, M.J. Kelley
The College of William and Mary, Williamsburg, USA
C.E. Reece
JLAB, Newport News, Virginia, USA

Funding: This work is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
To better understand the roll of topography on SRF cavity performance, we seek to obtain detailed topographic information from the curved practical cavity surfaces. Replicas taken from a cavity interior surface provide internal surface molds for fine Atomic Force Microscopy (AFM) and stylus profilometry. In this study, we confirm the replica resolution both on surface local defects such as grain boundary and etching pits and compare the surface uniform roughness with the aid of Power Spectral Density (PSD) where we can statistically obtain roughness parameters at different scales. A series of sampling locations are at the same magnetic field chosen at the same latitude on a single cell cavity to confirm the uniformity. Another series of sampling locations at different magnetic field amplitudes are chosen for this replica on the same cavity for later power loss calculation. We also show that application of the replica followed by rinsing does not adversely affect the cavity performance.

THPPP007

Proton-Beam Emittance Growth in SPS Coasts

emittance, vacuum, proton, simulation

3737

R. Calaga, L. Ficcadenti, E. Métral, R. Tomás, J. Tückmantel, F. Zimmermann
CERN, Geneva, Switzerland

Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP).
Proton-beam transverse emittance growth rates have been measured during SPS coasts to assess the possibility of using the SPS as a testbed for the LHC prototype crab cavities. The SPS measurements in coasts were performed at different beam energies, for varying RF voltage, beam intensity, and chromaticity. Results from these measurements are presented with potential explanations for the observed emittance growth.

THPPP011

Studies on a Wideband, Solid-state Driven RF System for the CERN PS Booster

impedance, feedback, acceleration, booster

3749

M.M. Paoluzzi, L. Arnaudon, N. Chritin, M. Haase, K. Hanke, B. Mikulec, T. Tardy
CERN, Geneva, Switzerland

In the framework of the LHC Injectors Upgrade project (LIU) the PS Booster (PSB) RF systems will undergo in depth consolidation and upgrade programs. The aim is increasing the extraction energy to 2 GeV and allowing reliable operations during next 25 years. Substantial improvements could come from the replacement of the existing narrowband, tuned systems covering the h=1 and h=2 frequency ranges (0.6 / 1.8 MHz and 1.2 / 3.6 MHz respectively) with wideband (0.5 / 4 MHz) Finemet® loaded cavities. The new system would be modular, allow multi-harmonic operation, use solid-state power stages and include fast RF feedback to compensate beam loading effects to some extent. A prove of principle system providing ≈3.0 kV accelerating voltage has been designed, constructed and installed in one of the PSB rings. This paper provides details on the design and measurements as well as information on the project status.

THPPP015

A Clamped Be Window for the Dump of the HiRadMat Experiment at CERN

vacuum, synchrotron, simulation, beam-loading

3758

M. Delonca, T. Antonakakis, D. Grenier, C. Maglioni, A. Sarrió Martínez
CERN, Geneva, Switzerland

At CERN, the High Radiation to Materials facility (HiRadMat) is designed to test accelerator components under the impact of high-intensity pulsed beams and will start operation in 2012. In this frame a LHC TED -type dump was installed at the end of the line, working in nitrogen over-pressure, and a 258μm-thick beryllium window was placed as barrier between the inside of the dump and the external atmosphere. Because of the special loading conditions, a clamped window design was especially developed, optimized and implemented, the more standard welded window not being suitable for such loads. Considering then the clamping force and the applied differential pressures, the stresses on the window components were carefully evaluated thanks to empirical as well as numerical models, to guarantee the structural integrity of the beryllium foil. This paper reports on choices and optimizations that led to the final design, presenting also comparative results from different solutions and the detailed results for the adopted one.

THPPP016

Upgrade Strategies for the Proton Synchrotron Booster Dump at CERN

proton, booster, extraction, synchrotron

3761

A. Sarrió Martínez, F. Loprete, C. Maglioni
CERN, Geneva, Switzerland

CERN’s LHC Injection chain Upgrade (LIU) involves a revision of the Proton Synchrotron Booster dump, which was designed in the 1960’s to cope with beam energies reaching 800 MeV and intensities of 10⁺¹³ particles per pulse. Thermo-mechanical studies highlighted the need for an upgrade of the dump, so that it is capable of withstanding energies in the order of 2 GeV and intensities up to 10⁺¹⁴ particles per pulse. This paper proposes a new design of the dump in the light of various constraints and choices such as the geometry, materials and the integration of the required cooling system. Further topics discussed include the strategy for dismantling the old device, which has been continuously irradiated for almost 40 years and presents a difficult access. Therefore, a detailed ALARA procedure is being prepared in order to carry out the upgrade works in the area.

THPPP031

RF Design of ESS RFQ

rfq, simulation, coupling, linac

3800

O. Piquet, M. Desmons, A. France
CEA/DSM/IRFU, France
O. Delferrière
CEA/IRFU, Gif-sur-Yvette, France

The low energy front end of ESS is based on a 352 MHz, 5-m long Radiofrequency Quadrupole (RFQ) cavity. It will accelerate and bunch proton beams from 75 keV to 3 MeV. The beam current is 50 mA (75 mA as an upgrade scenario) for 4% duty cycle. A complete RF analysis of the ESS RFQ has been performed using 3D RF simulating codes and a RFQ 4-wire transmission line model. Proposed RFQ is a 4 vane-type structure where 2D cross-section is optimized for lower power dissipation, while featuring simple geometrical shape suitable for easy machining. RF calculations are performed for the whole RFQ, and mainly for the following parts: end cells, vacuum port, tuners and RF coupling ports. Power losses are particularly calculated in order to achieve Thermo-mechanical calculations.

THPPP032

Advanced Layout Studies for the GSI CW-Linac

linac, solenoid, ion, heavy-ion

3803

W.A. Barth, S. Mickat
GSI, Darmstadt, Germany
S. Jacke
HIM, Mainz, Germany

Beam dynamics studies were made with the LORASR code for the planned superconducting (sc)continuous wave (cw) linear accelerator. It comprises a fixed accelerating part with an output energy of 3.5 MeV/u at a design mass/charge ratio of 6 and an energy variable part with an output energy of up to 7.3 MeV/u. The general layout, which provides for nine cavities combined with seven separate solenoids for a total length of 12.7 m, is based on a basic design by A. Minaev*. The recent studies show the parameter study for output energy variation. The statistical rotational and transverse offset error calculations illuminate the tolerances for acceptable errors. These are particularly relevant in the beam dynamics within a superconducting environment. Further calculations focus on varying the charge-to-mass ratio to reach linac energies up to 10 MeV/u, meeting the requirements of future UNILAC experiments.
*A. Minaev et al., “Superconducting, energy variable heavy ion linac with constant beta, multicell cavities of CH-type,” PRST-AB 12, 120101 (2009).

THPPP033

New Developments for the Present and Future GSI Linacs

linac, ion, emittance, proton

3806

L. Groening, W.A. Barth, G. Clemente, V. Gettmann, B. Schlitt
GSI, Darmstadt, Germany
M. Amberg, K. Aulenbacher, S. Mickat
HIM, Mainz, Germany
F.D. Dziuba, H. Podlech, U. Ratzinger, C. Xiao
IAP, Frankfurt am Main, Germany

For more than three decades, GSI has successfully operated the Universal Linear Accelerator (UNILAC), providing ions from protons to uranium at energies from 3 to 11 MeV/u. The UNILAC will serve for a comparable period as injector for the upcoming FAIR facility which will ask for short pulses of high peak currents of heavy ions. The UNILAC Alvarez-type DTL has been in operation since the earliest days of the machine, and it needs to be replaced to assure reliable operation for FAIR. This new DTL will serve the needs of FAIR, while demands of high duty cycles of moderate currents of intermediate-mass ions will be met by construction of a dedicated superconducting cw-linac. FAIR requires additionally provision of primary protons for its pbar physics program. A dedicated proton linac is under design for that task. The contribution will present the future linacs to be operated at GSI. Finally we introduce a novel method to provide flat ion beams for injection into machines having flat injection acceptances.

THPPP036

First Measurements of an Coupled CH Power Cavity for the FAIR Proton Injector

linac, coupling, proton, DTL

3812

R. M. Brodhage, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
G. Clemente, L. Groening
GSI, Darmstadt, Germany

For the research program with cooled antiprotons at FAIR a dedicated 70 MeV, 70 mA proton injector is required. The main acceleration of this room temperature linac will be provided by six CH cavities operated at 325 MHz. Each cavity will be powered by a 2.5 MW klystron. For the second acceleration unit from 11.5 MeV to 24.2 MeV a 1:2 scaled model has been built. Low level RF measurements have been performed to determine the main parameters and to prove the concept of coupled CH cavities. For this second tank technical and mechanical investigations have been performed to develop a complete technical concept for manufacturing. In Spring 2011, the construction of the first power prototype has started. The main components of this cavity were ready for measurements in fall 2011. At that time, the cavity was tested with a preliminary aluminum drift tube structure, which will allow precise frequency and field tuning. This paper will report on the recent technical developments and achievements. It will outline the main tuning and commissioning steps towards that novel type of proton DTL and it will show very promising results of the latest measurements.

THPPP039

Simulations for a Buncher-Cavity at GSI

simulation, impedance, resonance, induction

3821

P.L. Till, B. Koubek, A. Schempp, J.S. Schmidt
IAP, Frankfurt am Main, Germany

Buncher cavities can be used to bunch and rebunch or re-accelerate particle beams. A special form of these buncher cavities is a spiral structure. one of its main features is the easy adjustable frequency. A two-gap structure for the GSI has been simulated and will be build at the University of Frankfurt. This structure shall replace an existing buncher at GSI. It is designed to an frequency of 36 MHz. Also general simulations of spiral bunchers will be presented.

THPPP046

ESS End-to-End Simulations: a Comparison Between IMPACT and MADX

linac, simulation, space-charge, DTL

3841

E. Laface, R. Miyamoto
ESS, Lund, Sweden
D.C. Plostinar, C.R. Prior
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

The European Spallation Source will be a 5 MW superconducting proton linac for the production of spallation neutrons. It is composed of an ion source, a radio frequency quadrupole, a drift tube linac and a superconducting linac as well as the low, medium and high, energy beam transport sections. At present these components of the linac are in the design phase: the optimization of the accelerator parameters requires an intensive campaign of simulations to test the model of the machine under possible operational conditions. In this paper the results of simulations performed with the IMPACT and MADX-PTC codes are presented and a comparison is made between them and independent simulations using TraceWin. The dynamics of the beam envelope and single and multi-particle tracking are reported.

THPPP049

Tuning Procedure for the LINAC4 PI Mode Structure (PIMS)

simulation, linac, coupling, electron

3850

P. Ugena Tirado, F. Gerigk, R. Wegner
CERN, Geneva, Switzerland

PI-Mode-Structure (PIMS) cavities will be used in the high energy section of LINAC4 (10²-160 MeV). Each cavity is made of 7 coupled cells, operated in the π-mode at a resonant frequency of 352.2 MHz. The cell length remains constant for each of the 12 cavities but changes from cavity to cavity to synchronise with the increased beam energy. This paper reports on the tuning process required to get a constant voltage in each cell at the resonant frequency and consisting in re-machining to the required level the tuning rings located on each cell-wall. An algorithm based on single cell detuning, equivalent circuit simulations and precise 3D simulations for the 3 different cell types of each cavity has been developed and successfully applied to the tuning of the first PIMS cavity. In order to reduce the simulation effort for the remaining 11 cavities, an interpolation algorithm based on 3 cavities has been developed and validated. In a second tuning step, after the electron beam welding of all cells, the final adjustment of single-cell frequencies and field flatness is achieved by cutting the length of one plunger tuner per cell.

THPPP054

A New Half-Wave Resonator Cryomodule Design for Project-X

cryomodule, alignment, vacuum, focusing

3865

Z.A. Conway, A.O. Bergado, R.L. Fischer, M. Kedzie, M.P. Kelly, B. Mustapha, P.N. Ostroumov
ANL, Argonne, USA
V.A. Lebedev
Fermilab, Batavia, USA

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics and Nuclear Physics, under Contract DE-AC02-76CH03000 and DE-AC02-06CH11357.
We present the current status of our Project-X half-wave resonator cryomodule development effort. The Project-X injector requires a single cryomodule with 9 superconducting, 162.5-MHz, β = 0.11, half-wave resonators interleaved with 6 integrated superconducting solenoids/steering coils. This cryomodule is being designed and build by ANL with the intent of delivering a device which has all external connections to the cryogenic, RF, and instrumentation systems located at removable junctions separated from the clean cavity vacuum system. Issues include the ease of assembly, cavity cleanliness, interfacing to subsystems (e.g., cryogenics, couplers, tuners, etc.), and satisfying the ANL/FNAL/DOE guidelines for vacuum vessels. We employ proven warm-to-cold low-particulate beamline transitions to minimize unused space along the linac, a top-loading box design that minimizes the size of the clean room assembly, and compact beamline devices to minimize the length of the focusing period.

THPPP057

PXIE Optics and Layout

focusing, cryomodule, rfq, solenoid

3871

V.A. Lebedev, S. Nagaitsev, J.-F. Ostiguy, A.V. Shemyakin, B.G. Shteynas, N. Solyak
Fermilab, Batavia, USA

The Project X Injector Experiment (PXIE) will serve as a prototype for the Project X front end. The aim is to validate the Project-X design and to decrease technical risks, known to be mainly related to the front end. PXIE will accelerate a 1 mA CW beam to about 25 MeV. It will consist of an ion source, LEBT, CW RFQ, MEBT, two SC cryomodules, a diagnostic section and a beam dump. A bunch-by-bunch chopper located in the MEBT section will allow formation of an arbitrary bunch structure. PXIE deviates somewhat from the current Project-X front end concept in that it provides additional instrumentation and relies on a reduced number of kickers for bunch chopping; the diagnostic section also include an RF separator to allow studying extinction of removed bunches. The paper discusses the main requirements and constraints motivating the facility layout and optics. Final adjustments to the Project X front end design, if needed, will be based on operational experience gained with PXIE.
Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.

THPPP062

The Six-Cavity Test - Demonstrated Acceleration of Beam with Multiple RF Cavities and a Single Klystron

controls, rfq, klystron, proton

3877

J. Steimel, J.-P. Carneiro, B. Chase, S. Chaurize, E. Cullerton, B.M. Hanna, R.L. Madrak, R.J. Pasquinelli, L.R. Prost, L. Ristori, V.E. Scarpine, P. Varghese, R.C. Webber, D. Wildman
Fermilab, Batavia, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The High Intensity Neutrino Source (HINS) ‘Six-Cavity Test’ has demonstrated the use of high power RF vector modulators to control multiple RF cavities driven by a single high power klystron to accelerate a non-relativistic beam. Installation of 6 cavities in the existing HINS beamline has been completed and beam measurements have started. We present data showing the energy stability of the 7 mA proton beam accelerated through the six cavities from 2.5 MeV to 3.4 MeV.

THPPP063

CW Room Temperature Re-buncher for the Project X Front End

linac, simulation, beam-transport, vacuum

3880

G.V. Romanov, M.H. Awida, M. Chen, I.V. Gonin, S. Kazakov, R.A. Kostin, V.A. Lebedev, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, USA

At Fermilab there is a plan to construct the Project X Injector Experiment (PXIE) facility - a prototype of the front end of the Project X, a multi-MW proton source based on a superconducting linac. The construction and successful operations of this facility will validate the concept for the Project X front end, thereby minimizing the primary technical risk element within the Project. The front end of the linac contains a cw room-temperature MEBT section which comprises an ion source, RFQ, and high-bandwidth bunch selective chopper. The length of the MEBT exceeds 9 m, so three re-bunching cavities are used to support the beam longitudinal dynamics. The paper reports RF design of the re-bunchers along with preliminary beam dynamic and thermal analysis of the cavities.

THPPP066

Beam Tuning Strategy of the FRIB Linac Driver

linac, solenoid, coupling, ion

3889

Y. Zhang
FRIB, East Lansing, Michigan, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
The FRIB linac driver will deliver heavy ion beams up to uranium, with an energy of 200 MeV/u and total power on target of 400 kW. To reach the design power for heaviest ions, multi-charge-state beams will be accelerated simultaneously in this SRF linac. Beam tuning of the linac driver is among the most challenging tasks. In this paper, we discuss the beam tuning strategy, which includes the cavity synchronous phase and acceleration gradient setup, beam trajectory correction, and transverse matching with horizontal-vertical coupled beams as superconducting solenoids are used for transverse focusing in the linac segments.

THPPP068

Investigation of a Multi-cell Cavity Structure Proposed for Improved Hydroforming

focusing, coupling, HOM, SRF

3895

K.R. Shin
ORNL RAD, Oak Ridge, Tennessee, USA
A.E. Fathy
University of Tennessee, Knoxville, Tennessee, USA
J.A. Holmes, Y.W. Kang
ORNL, Oak Ridge, Tennessee, USA

A multi-cell cavity structure with rectangular coupling aperture between cavity cells is proposed. This investigation is to study the RF properties of such structure that may provide high yield in hydroforming. In mechanical point of view, the rectangular aperture iris may provide much improved structure quality in hydroforming since it can help to reduce the stress incurring within the sheet metal with improved structural malleability. The necking procedure can be easier because of greater perimeter in the iris geometry. Peak electric and magnetic fields per accelerating gradient may increase however, compared to traditional TESLA type elliptical cavity structure. The rectangular iris shape provides asymmetric transverse focusing per half RF period. If the horizontal and vertical rectangular irises are interleaved, the net transverse focusing may be achieved. 3D simulations with CST MWS have been carried out to analyze EM field properties and the cavity parameters.

THPPP069

Double-Gap Rebuncher Cavity Design of SNS MEBT

DTL, simulation, linac, impedance

3898

K.R. Shin
ORNL RAD, Oak Ridge, Tennessee, USA
A.E. Fathy
University of Tennessee, Knoxville, Tennessee, USA
Y.W. Kang
ORNL, Oak Ridge, Tennessee, USA

A double-gap rebuncher cavity has been studied through design and analysis with computer simulations. This cavity shape is a two cell abridged form of drift tube linac (DTL), instead an omega form of existing single gap elliptical cavity. The cavity operates in TM010 mode, likewise the commonly used single-gap cavities in some medium energy beam transport (MEBT) line of proton accelerators. The new cavity is more power efficient even with slightly lower Q factor because of utilization of two interactive gaps. The breakdown field can be lowered with adjustment of gap and tube length ratio. Electromagnetic, beam envelope, and thermal simulations are presented with comparison to the properties of the conventional elliptical cavity.

THPPP075

Present Status and Developments of the Linear IFMIF Prototype Accelerator (LIPAc)

rfq, solenoid, linac, SRF

3910

A. Mosnier, P. Cara, R. Heidinger
Fusion for Energy, Garching, Germany
P.-Y. Beauvais, S. Chel
CEA/IRFU, Gif-sur-Yvette, France
A. Facco, A. Pisent
INFN/LNL, Legnaro (PD), Italy
A. Ibarra, J. Molla
CIEMAT, Madrid, Spain
V. Massaut, D. Vandeplassche
SCK•CEN, Mol, Belgium
H. Matsumoto, G. Pruneri, Ch. Vermare
IFMIF/EVEDA, Rokkasho, Japan
M. Sugimoto, H. Suzuki
JAEA, Aomori, Japan

The International Fusion Materials Irradiation Facility (IFMIF) aiming at generating materials irradiation test data for DEMO and future fusion power plants is based on an accelerator-driven, D-Li neutron source to produce high energy neutrons at sufficient intensity and irradiation volume. IFMIF Engineering Validation and Engineering Design Activities (EVEDA) have been conducted since mid 2007 in the framework of the Broader Approach Agreement and the scope of the project has been recently revised to set priority on the validation activities, especially on the Accelerator Prototype (LIPAc) with extending the duration up to mid 2017 in order to better fit the development of the challenging components and the commissioning of the whole accelerator. This paper summarizes the present status of the LIPAc, currently under construction at Rokkasho in Japan, outlines the engineering design and the developments of the major components, as well as the expected outcomes of the engineering work, associated with the experimental program.

THPPP082

RF Feedforward System for Beam Loading Compensation in the J-PARC MR

impedance, injection, beam-loading, proton

3924

F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
K. Hara, K. Hasegawa, C. Ohmori, M. Yoshii
KEK, Tokai, Ibaraki, Japan
M. Toda
KEK/JAEA, Ibaraki-Ken, Japan

For acceleration of high intensity proton beams in the J-PARC MR, beam loading compensation is important. In the MA-loaded RF cavity in the MR, which has a Q-value in the order of 20, the wake voltage consists of the accelerating harmonic (h=9) and the neighbor harmonics (h=8, 10). We employ the RF feedforward method for the beam loading compensation, like in the J-PARC RCS, in which the impedance seen by the beam is greatly reduced by the feedforward. The full-digital feedforward system developed for the MR has a similar architecture to that of the RCS. The system compensates the beam loading of the important three harmonics (h=8, 9, 10). We present the structure of the RF feedforward system. Also, we report the preliminary results of the beam tests.

THPPP093

Progress on MICE RFCC Module

vacuum, coupling, solenoid, controls

3954

D. Li, D.L. Bowring, A.J. DeMello, S.A. Gourlay, M.A. Green, N. Li, T.O. Niinikoski, H. Pan, S. Prestemon, S.P. Virostek, M.S. Zisman
LBNL, Berkeley, California, USA
A.D. Bross, R.H. Carcagno, V. Kashikhin, C. Sylvester
Fermilab, Batavia, USA
Y. Cao, S. Sun, L. Wang, L. Yin
SINAP, Shanghai, People's Republic of China
A.B. Chen, B. Guo, L. Li, F.Y. Xu
ICST, Harbin, People's Republic of China
D.M. Kaplan
Illinois Institute of Technology, Chicago, Illinois, USA
T.H. Luo, D.J. Summers
UMiss, University, Mississippi, USA

Funding: This work was supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC02-05CH11231, US Muon Accelerator Program and NSF MRI award: 0959000.
Recent progress on the design and fabrication of the RFCC (RF and Coupling Coil) module for the international MICE (Muon Ionization Cooling Experiment) will be reported. The MICE ionization cooling channel has two RFCC modules; each having four 201-MHz normal conducting RF cavities surrounded by one superconducting coupling coil (solenoid) magnet. The magnet is designed to be cooled by 3 cryocoolers. Fabrication of the RF cavities is complete; preparation for the cavity electro-polishing, low power RF measurements and tuning are in progress at LBNL. Fabrication of the cold mass of the first coupling coil magnet has been completed in China and the cold mass arrived at LBNL in late 2011. Preparations for testing the cold mass are currently under way at Fermilab. Plans for the RFCC module assembly and integration are being developed and will be described.

THPPR005

The Preliminary Test of a Digital Control System Based on the FPGA for a PEFP 120-keV RF Cavity

controls, resonance, accelerating-gradient, proton

3975

Y.M. Li, S. Cha
UST, Daejeon City, Republic of Korea
Y.-S. Cho, J.-H. Jang, H.S. Kim, H.-J. Kwon, Y.M. Li, K.T. Seol, Y.-G. Song
KAERI, Daejon, Republic of Korea

Funding: Proton Engineering Frontier Project, Korea Atomic Energy Research Institute, Ministry of Education, Science and Technology of the Republic of Korea.
PEFP developed a 120-keV RF cavity for their ion implantation applications. Due to ambient disturbances, the cavity’s resonance frequency may vary in long-term test. We designed a digital control system to change the frequency of the RF sources for tracking the cavity’s frequency variations. The digital control system has functions such as, phase shift, phase comparison, proportional-integral compensation, waveform generation and frequency/pulse modulation, and driving signal generator. Most of them are implemented digitally in a Virtex II 4000 Field Programmable Gate Array (FPGA). In this research we show the design and the preliminary test results of the digital control system.
* Work supported by the Ministry of Science and Technology

THPPR012

Lorentz Force Compensation for Long Pulses in SRF Cavities

linac, controls, SRF, cryomodule

3990

Y.M. Pischalnikov, G.I. Cancelo, B. Chase, D.J. Crawford, D.R. Edstrom, Jr, E.R. Harms, R.A. Kostin, W. Schappert, N. Solyak
Fermilab, Batavia, USA

Lorentz force compensation of 8ms pulses in Tesla style elliptical cavities has been studied in Fermilab SRF Test Facility. Detuning measurements and compensation results are presented.

THPPR030

High Power Test of RF Separator For 12 GeV Upgrade of CEBAF at Jefferson Lab

vacuum, ion, extraction, coupling

4032

S. Ahmed, C. Hovater, G.A. Krafft, J.D. Mammosser, M. Spata, M.J. Wissmann
JLAB, Newport News, Virginia, USA
J.R. Delayen
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
CEBAF at JLab is in the process of an energy upgrade from 6 GeV to 12 GeV. The existing setup of the RF separator cavities in the 5th pass will not be adequate enough to extract the highest energy (11 GeV) beam to any two existing halls (A, B or C) while simultaneously delivering to the new hall D in the case of the proposed 12 GeV upgrade of the machine. To restore this capability, several options including the extension of existing normal conducting (NC) and a potential 499 MHz TEM-type superconducting (SC) cavity design have been investigated using computer simulations. Detailed numerical studies suggest that six 2-cell normal conducting structures meet the requirements; each 2-cell structure will require up to 4 kW RF input power in contrast with the current nominal operating power of 1.0 to 2.0 kW. A high power test to 4 kW is required to confirm the cavity’s operate-ability at these elevated gradient and power levels. We have assembled a 2-cell cavity, pumped down to 2.0·10^-9 torr using ion pump and confirmed the low level RF performance. A high power test is in progress and will be completed soon. The detailed numerical and experimental results will be discussed in the paper.

THPPR070

Development of Multi-collision Laser Compton Scattering X-ray Source on the Basis of Compact S-band Electron Linac

laser, electron, photon, linac

4139

R. Kuroda, M. Koike, E. Miura, Y. Taira, H. Toyokawa, K. Yamada, E. Yamaguchi
AIST, Tsukuba, Ibaraki, Japan
M. Kumaki
RISE, Tokyo, Japan

A compact hard X-ray source via laser Compton scattering is required for biological, medical and industrial science because it has many benefits about generated X-rays such as short pulse, quasi-monochromatic, energy tunability and good directivity. Our X-ray source is conventionally the single collision system between an electron pulse and a laser pulse. To increase X-ray yields, we have developed a multi-collision system with a multi-bunch electron beam and a laser optical cavity. The multi-bunch electron beam has already been generated from a Cs-Te photocathode rf gun system using a multi-pulse UV laser. The laser optical cavity have developed like a regenerative amplification including the collision point between the electron pulse and the laser pulse which is based on the Ti:Sa laser with a mode-locked frequency of 79.33 MHz. In this preliminary experiment, the modulated seed laser pulses were generated and leaded to the cavity, so that laser build-up amplification was performed in the cavity length of 3.78 m with two seed pulses. In this conference, we will describe the results of preliminary experiments for the multi-collision system and future plans.

FRXAA02

Advanced Solid State Lasers are Merging with Accelerators

laser, acceleration, higher-order-mode, alignment

4157

A. Tünnermann, J. Limpert
Friedrich Schiller Universität, Jena, Germany
T. Schreiber
Fraunhofer-Institute for Applied Optics and Precision Engineering, Jena, Germany

In recent years, lasers have been developed to an essential tool in accelerator science, for acceleration and diagnostics. Novel applications require for high average power lasers in continuous and pulsed operation with diffraction limited beam quality. Lasers are known as sophisticated systems with a notorious poor efficiency. Most recently, rare-earth-doped fibers have established themselves as an attractive and power scalable solid-state laser concept. Using advanced large mode area fibers, in continuous-wave operation output powers in the 10 kW-regime with diffraction-limited beam quality at electrical to optical efficiencies of 30 percent have been demonstrated. In the pulsed regime average powers of the order of 1 kW even for femtosecond fiber laser systems have been reported. Coherent beam combination of these lasers allows for the generation of high peak power pulses at high repetition rates and output powers. In this contribution the state of the art in solid state laser technology operating at high average powers with inherent high efficiencies is reviewed. The prospects for future developments that will meet the demands set by the accelerator community will be discussed.

Slides FRXAA02 [11.729 MB]