• S. Henderson
  

The Spallation Neutron Source (SNS) will be the world's leading pulsed neutron source, with design beam power capability of 1.4 MW. The SNS Construction Project was completed in June 2006. The accelerator complex was successfully commissioned during the construction phase of the project in seven discrete commissioning runs. The facility is now in the first of a three year performance ramp-up phase, in which the beam power, reliability and operating time will be increased to the baseline design values of 1.4 MW, 90% and 5000 hours respectively. Meanwhile, neutron scattering instruments are being constructed and commissioned in preparation for full user operations in 2009. The progress toward bringing the SNS to its full capabilities will be presented.

• L. Merminga
  

• J. Q. Wang
  
• L. Ma, C. Zhang
  IHEP Beijing, Beijing

• L. S. Cardman
  
• L. Harwood
  Jefferson Lab, Newport News, Virginia

CEBAF is a 5-pass, recirculating cw electron linac operating at ~6 GeV. The 12-GeV Upgrade is a $300M project anticipated to receive Critical Decision 2 approval in late summer of 2007 and begin construction activities in 2008; funding for the project is provided by the DOE Office of Nuclear Physics which will double the beam energy. The new energy reach will permit significant extensions in research into non-perturbative aspects of QCD. Areas of interest are Generalized Parton Distributions (GPDs), measurements at high-xBjorken, and the use of hybrid mesons to explore the nature of quark confinement. The upgrade includes: doubling the accelerating voltages of the linacs by adding 10 new high-performance cryomodules plus the requisite expansion of the 2K cryogenics plant and rf power systems, upgrading the beam transport system from 6 GeV to 12 GeV capability through extensive re-use of existing hardware, adding one recirculation arc, adding a new experimental area and the beamline to it, building new experimental equipment for the GPD, high-xBjorken, and hybrid mesons programs. The presentation will touch on the science and give some details of the accelerator plans.

• M. Eriksson
  
• M. Berglund, M. Brandin, D. Kumbaro, P. Lilja, L.-J. Lindgren, L. Malmgren, M. Sjostrom, S. Thorin, E. J. Wallen, S. Werin
  MAX-lab, Lund
• H. Tarawneh
  SESAME, Amman

• G. Hoffstaetter
  
• I. V. Bazarov, G. W. Codner, M. Forster, S. Greenwald, Y. Li, M. Liepe, C. E. Mayes, C. K. Sinclair, C. Song, A. Temnykh, M. Tigner, Y. Xie
  CLASSE, Ithaca
• D. H. Bilderback, D. S. Dale, K. Finkelstein, S. M. Gruner
  CHESS, Ithaca, New York
• B. M. Dunham
  Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
• D. Sagan
  Cornell University, Department of Physics, Ithaca, New York

The status of plans for an Energy-Recovery Linac (ERL) X-ray facility at Cornell University is described. Currently, Cornell operates the Cornell High Energy Synchrotron Source (CHESS) at the CESR ring and the ERL is planned to be an extension to the CESR ring with the addition of a 5-GeV superconducting c.w. linac. Topics covered in this paper include the full layout on the Cornell campus, the different operation modes of the accelerator, methods to limit emittance growth, control of beam-ion effects and ways to limit transverse instabilities. As an upgrade of the CESR ring, special attention is given to reuse of many of the existing components. The very small electron-beam emittances would produce an x-ray source that is highly superior than any existing storage-ring light source. The ERL includes 18 X-ray beamlines optimized for specific areas of research that are currently being defined by an international group of scientists. This planned upgrade illustrates how other existing storage rings could be upgraded to work as ERL light sources with vastly improved beam qualities and with limited dark time for x-ray users.

• K. Schoenberg
  

• G. Neil
  

• K. C.D. Chan
  
• A. J. Jason, P. J. Turchi
  LANL, Los Alamos, New Mexico

For national security, it is important to detect the presence of Special Nuclear Materials (SNM), especially Highly-Enriched Uranium (HEU). Generally used methods for such detection include interrogation by photons and neutrons. For example, photofission in HEU can be initiated with 14-MeV photons. The resulting delayed neutrons and photons from the fission fragments are clear signatures of the presence of HEU. One can generate high-energy photons using electron accelerators via various mechanisms. In this paper, we will describe two of them, namely electron bremsstrahlung and Compton-backscattered photons. We focus on these two mechanisms because they cover a wide range of accelerator requirements. Electron bremsstrahlung can be generated using a compact low-energy electron linac while the generation of Compton-backscattered photons requires a high-energy electron accelerator of a few hundred MeV. We review these two options, describe their accelerator requirements, and compare their relative merits.

• P. F. Tavares
  
• F. Arroyo, R. H.A. Farias, L. C. Jahnel, C. Pardine, C. Rodrigues
  LNLS, Campinas

• W. R. Rawnsley
  
• R. E. Laxdal, A. K. Mitra
  TRIUMF, Vancouver

• G. E. Le Dem
  
• M. Di Giacomo
  GANIL, Caen

The Eurisol heavy ion post-accelerator and the Spiral2 deuton/ion MEBT should transport a continuous wave (cw) beam from respectively a 88.05 MHz RFQ (β respectively 0.036 and 0.04) to a drift-tube linac. A high frequency chopper is being studied to select only 1 bunch over N, 10 < N < 10000 as asked by the physicists. It requires pulses higher than 3 kV, rising in less than 7 ns at a repetition rate up to 8.8 MHz. These figures are at the border of what can be provided by the travelling wave fast choppers and the capacitive-type chopping technologies. We have reviewed the current fast and slow chopping structures and their associated pulse generator. Some preliminary RF simulations to adapt the present chopping devices to our requirements are presented. The main limitations of these technologies when applied to isolate bunches in ion cw accelerators are also shown. Our first studies and results to solve the arising problems are discussed.

• V. V. Katalev
  
• S. Choroba
  DESY, Hamburg

• S. Simrock
  
• K. C. Czuba
  Warsaw University of Technology, Institute of Electronic Systems, Warsaw
• M. F. Felber, M. Hoffmann, B. Lorbeer, F. Ludwig, H. C. Weddig
  DESY, Hamburg

• K. Fan
  
• H. Kobayashi, H. Matsumoto, Y. Sakamoto
  KEK, Ibaraki

• S. Ohsawa
  
• Y. Hozumi
  Advanced Manufacturing Research Institute, Tsukuba
• M. Ikeda, T. Sugimura
  KEK, Ibaraki

• H. Sato
  
• T. Ise, Y. Miura
  Osaka University, Suita
• S. Nomura
  Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Tokyo
• t.s. Shintomi, M. J. Shirakata
  KEK, Ibaraki

• I. Sugai
  
• T. Hattori, K. K. Kawasaki
  Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Tokyo
• Y. Irie
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• H. Kawakami, M. Oyaizu, A. Takagi, Y. Takeda
  KEK, Ibaraki

• A. Takagi
  
• C. S. Feigerle
  University of Tennessee, Knoxville, Tennessee
• Y. Irie
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• M. A. Plum, R. W. Shaw
  ORNL, Oak Ridge, Tennessee
• I. Sugai, Y. Takeda
  KEK, Ibaraki

Thick carbon stripper foils of >300 μg/cm² will be used as a stripping of H-ion beam for 3GeV Rapid Cycling Synchrotron (3GeV-RCS) of the J-PARC. The carbon foils with long lifetime even at >1800 K are required. For this purpose, we have developed a new irradiation system for the lifetime measurement using high current pulsed and dc H^- beams of the KEK Cockcroft-Walton accelerator. These high power 650keV H^- Ion beams can simulate the high energy deposition in carbon stripper foils at the J-PARC RCS. An automatic data acquisition system is also developed for recording the data of foil temperature and irradiated beam current. The Hybrid Boron mixed Carbon (HBC) stripper foils, which are developed at KEK are irradiated by high current H^- ion beam up to 2000 K. A few SNS-diamond and commercially available carbon (CM) foils are also tested for comparing with HBC-foils. The results of the lifetime measurement of HBC and SNS-diamond including CM stripper foils are reported.

• H. Sako
  
• C. K. Allen
  KEK, Ibaraki
• H. Ikeda
  Visual Information Center, Inc., Ibaraki-ken
• G. B. Shen
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

• Y.-G. Song
  
• Y.-S. Cho, I.-S. Hong
  KAERI, Daejon

Proton Engineering Frontier Project (PEFP) has above 40 magnet power supplies for the 20MeV proton linac. Because some power supplies have analog interfaces, we chose ATEC (Analog Input To Ethernet Converter) to monitor their output currents and voltage by supporting the protocol conversion function. Software components of the Experimental Physics and Industrial Control System (EPICS) have been ported to a VME single board computer based on a PowerPC microprocessor (MPC7410). This paper presents the software component and processing of analog input values between EPICS on the PowerPC based board and ATEC operating as Server Mode.

• S.-C. Kim
  
• J. Choi, K. M. Ha, J. Y. Huang
  PAL, Pohang, Kyungbuk

At 2006, PLS Linac magnet power supply (MPS) has been upgraded for the stable beam injection and 4th generation light source research. New MPS are developed new compact MPS of 16-bit resolution and 20ppm stability using four-quadrant switching scheme with 50kHz MOSFET switching device, and consists of main power board, control power board, regulator board and CPU board. Size of each board is only 100mm width and 240mm depth. Output of MPS is 10V, ±10A for the bipolar and 50V, 50A for the unipolar magnet. Main board is consisted four-quadrant FET switch, driver and output filter. Output filter must be perfectly eliminating switch frequency and compact size. In this paper, we report on development and characteristics of compact output filter of the new MPS for PAL linac.

• A. Andersson
  
• J. P.H. Sladen
  CERN, Geneva

High precision beam phase measurements will be vital for synchronization of main and drive beams in CLIC. Development work is underway with the aim to demonstrate 0.1 degree resolution for a wideband 30GHz measurement. In order to be able to test this with a beam exhibiting much higher phase jitter, two prototypes have been built so that the difference in their outputs can be measured. Results of measurements made with bunch trains in CTF3 are presented.

• C.-K. Chang
  
• H. C. Chen, M. J. Horng, J. A. Li, T. F. Lin, Y. K. Lin, Y.-C. Liu
  NSRRC, Hsinchu

• C. Y. Wu
  
• J. Chen, K. T. Hsu, S. Y. Hsu, J.-Y. Hwang, D. Lee, K.-K. Lin, C.-J. Wang
  NSRRC, Hsinchu

• D. R. Walters
  

A prototype vacuum chamber is under development at the Advanced Photon Source for use in the Linac Coherent Light Source at Stanford Linear Accelerator Center. The chamber will be fabricated from the austenite stainless steels. The chamber requires a continuous aluminum coating on the inner surface in order to reduce the wakefield losses to a level within the resistivity budget. The method being presented here is unique in that it can be applied to a fully fabricated chamber 5 mm high, 11.5 mm wide, and 3460 mm long. In existing methods the chamber aperture has been much larger than is used here. This paper describes a method applicable for these smaller cross sections. This process uses a pair of small electrodes, centered in the aperture, where they are attached to a high frequency AC power supply. In this configuration each electrode is connected to the opposite polarity of the other. The chamber cavity is filled with argon gas to facilitate the formation of a glow discharge causing the aluminum electrodes to sputter onto the chamber walls. This paper presents the laboratory test results from small samples up to the full-sized assemblies.

• I. Terechkine
  
• V. Kashikhin, T. M. Page, M. Tartaglia, J. C. Tompkins
  Fermilab, Batavia, Illinois

• M. Votava
  
• B. Chase, M. Wendt
  Fermilab, Batavia, Illinois

The major controls and instrumentation systems for the ILC test areas and the NML test accelerator at Fermilab are discussed. The test areas include 3 separate areas for Vertical Superconducting RF Cavity Testing, Horizontal Cavity Testing, and NML RF and beam test area. A common control infrastructure for the test areas including a controls framework, electronic logbook and cavity database will be provided, while supporting components supplied by collaborators with diverse areas of expertise (EPICS, DOOCS, LabVIEW, and Matlab). The discussions on the instrumentation systems are focused on overview and requirements.

• J. T. Bradley III
  
• C. J. Andrews, L. F. Fernandez, M. F. Fresquez, W. Reass, W. Roybal, J. B. Sandoval
  LANL, Los Alamos, New Mexico

The proton beam in the LANSCE accelerator is guided and focused almost exclusively by electromagnets. Magnet hysteresis has had significant impacts on the tuning of the LANSCE accelerator.* Magnet hysteresis can also have an impact on Magnet Power Supply (MPS) control, regulation and repeatability requirements. To date, MPS performance requirements have been driven by the requirements on the magnetic fields as determined by the accelerator physicists. Taking hysteresis effects into account can significantly change MPS requirements, as some requirements become more stringent and some are found to be overspecified. Overspecification of MPS requirements can result in significant increases in MPS cost. Conversely, the use of appropriate MPS requirements can result in significant cost savings. The LANSCE accelerator's more than three decades of operation provide a wide variety of magnet power supply technologies and operational experience. We will survey the LANSCE magnet power supply history and determine how performance specifications can be refined to both reduce costs and improve the operators abilities to control the magnetic fields.

*R. McCrady, "Mitigation Of Magnet Hysteresis Effects at LANSCE", LINAC 2006, August, 2006.

• S. S. Kurennoy
  

* S. S. Kurennoy and J. F. Power, EPAC 2000 (Vienna, Austria, 2000), 336.

• R. C. McCrady
  
• S. Assadi, C. Deibele, S. Henderson, M. A. Plum
  ORNL, Oak Ridge, Tennessee
• J. M. Byrd
  LBNL, Berkeley, California
• S.-Y. Lee
  IUCF, Bloomington, Indiana
• R. J. Macek, S. B. Walbridge, T. Zaugg
  LANL, Los Alamos, New Mexico
• M. T.F. Pivi
  SLAC, Menlo Park, California

A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos National Laboratory Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). Evidence obtained from these tests suggests that further improvement in performance is limited by beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizontal plane, which had no feedback. Here we describe the present system configuration, system optimization, results of several recent experimental tests, and results from studies of factors limiting its performance.

• M. Pieck
  
• E. Bjorklund, G. P. Carr, J. A. Faucett, J. O. Hill, D. M. Kerstiens, P. S. Marroquin, P. McGhee, M. A. Oothoudt, S. Schaller
  LANL, Los Alamos, New Mexico

• T. Tajima
  
• M. J. Borden, A. Canabal, J. P. Chamberlin, S. Harrison, F. R. Olivas, M. A. Oothoudt, J. J. Sullivan
  LANL, Los Alamos, New Mexico

• V. P. Yakovlev
  
• J. L. Hirshfield
  Omega-P, Inc., New Haven, Connecticut
• A. Kanareykin
  Euclid TechLabs, LLC, Solon, Ohio
• S. Kazakov
  KEK, Ibaraki
• E. Nenasheva
  Ceramics Ltd., St. Petersburg

A fast, electrically-controlled phase shifter is described with parameters suitable for operation with the SC acceleration structure of the electron cooling system of Relativistic Heavy Ion Collider (RHIC) at BNL. The phase shifter is a key element of the external RF vector modulator that is capable of fast tuning of the cavities against microphonics, Lorentz force and beam instabilities in a way that can possibly lead to an order of magnitude reduction in the required RF power. The phase shifter is based on a shortened low-impendence coaxial line with ferroelectric rings. The dielectric constant of the ferroelectric rings is altered by applying a 4.2 kV voltage that provides an RF phase shift from 0 to 180 deg.

• H. Ma
  
• M. S. Champion, M. T. Crofford, T. W. Hardek, K.-U. Kasemir, M. F. Piller, Y. Zhang
  ORNL, Oak Ridge, Tennessee

The proposed upgrade plan for RF control of the Spallation Neutron Source (SNS) accumulator ring requires that the new digital field control module (FCM) support both the conventional narrow-band feed forward control and a new beam-based feed forward control. Both are necessary for compensating the heavy beam loading in SNS ring. The ring FCM also has the integrated control and monitoring features for the cavity bias, cavity resonance, and tetrode grid boost. A user-friendly Epics GUI for all these FCM functionalities is also a part of the requirement. The ring FCM under development is being implemented on the hardware of the proven FCM of SNS Linac. Both the controller architecture and the design code of the digital hardware for the Linac system will be largely reused in the ring system.

• M. P. McCarthy
  
• D. E. Anderson, I. E. Campisi, F. Casagrande, R. I. Cutler, G. W. Dodson, J. Galambos, D. P. Gurd, Y. W. Kang, K.-U. Kasemir, S.-H. Kim, H. Ma, B. W. Riemer, J. P. Schubert, M. P. Stockli
  ORNL, Oak Ridge, Tennessee

Increasing the pulse repetition rate (PRR) of the SNS Linac to its designed maximum of 60 Hz to provide 1.4 MW of beam on target is in progress. Operation above 60 Hz in the future to provide beam to a second target is also being considered. Increasing the PRR to 80 Hz would allow the additional pulses to be diverted to a second target. This paper discusses the impact of increasing the PRR on the SNS infrastructure including Radio Frequency (RF) systems and structures, the ion source, cryogenics, controls and the target.

• D. C. Williams
  
• X. Geng, P. Ladd
  ORNL, Oak Ridge, Tennessee

The superconducting linac of the Spallation Neutron Source (SNS) has 23 cryomodules each of which incorporate either 3 or 4 niobium cavities. These cavities are submerged in a bath of liquid helium and maintained at an operating temperature of ~ 2K. This bath is surrounded by heat shields and a multilayer blanket within the cryomodule shell. The pressure in this area needs to be maintained at <5·10^-5 torr to limit heat leak due to gas convection. Some cryomodules have developed helium leaks into this vacuum cavity and now need to be actively pumped. This paper provides an overview of the Insulating Vacuum System (IVS) that has been installed for this purpose.

• W. Meng
  
• G. Ganetis, A. K. Jain, D. Kayran, V. Litvinenko, C. Longo, G. J. Mahler, E. Pozdeyev, J. E. Tuozzolo
  BNL, Upton, Long Island, New York

In this paper we describe unique features of magnets for R&D ERL, which is under construction in Collider-Accelerator Department, BNL. The R&D ERL serves as a test-bed future BNL ERLs, such as electron-cooler-ERL for RHIC and 20 GeV ERL for future electron-hadron, eRHIC. We present selected designs of various dipole and quadrupole magnets, which are used in Z-bend merging systems and the returning loop, 3-D simulations of the fields in these magnets, particle tracking and analysis of magnet's influence on the beam parameters. We discuss an uncommon method of setting requirements on the quality of magnetic field and transferring them into measurable parameters as well as into manufacturing tolerances. We compare selected simulation with results magnetic measurements.

• C. R. Prior
  

• A. Adelmann
  
• R. J. Bakker, C. Kraus, K. L. Li, B. S.C. Oswald, M. Pedrozzi, J.-Y. Raguin, T. Schietinger, F. Stulle, A. F. Wrulich
  PSI, Villigen
• J. Qiang
  LBNL, Berkeley, California

• F. Zhou
  
• R. B. Agustsson, G. Andonian, D. B. Cline, A. Y. Murokh, J. B. Rosenzweig
  UCLA, Los Angeles, California
• A. C. Kabel
  SLAC, Menlo Park, California
• V. Yakimenko
  BNL, Upton, Long Island, New York

Space charge and coherent synchrotron radiation may deteriorate electron beam quality when the beam passes through a magnetic bunch compressor. This paper presents the transverse phase-space tomographic measurements for a compressed beam at 60 MeV, around which energy the first stage of magnetic bunch compression takes place in most advanced linacs. Transverse phase-space bifurcation of a compressed beam is observed at that energy, but the degree of the space charge-induced bifurcation is appreciably lower than the one observed at 12 MeV. The Trafic4 simulation confirms the observation.

The paper was published at PRST-AB, November 2006

• R. Duperrier
  
• D. Uriot
  CEA, Gif-sur-Yvette

• S. Choroba
  

• G. J. Caporaso
  
• D. T. Blackfield, Y.-J. Chen, J. R. Harris, S. A. Hawkins, L. Holmes, S. D. Nelson, A. Paul, B. R. Poole, M. A. Rhodes, S. Sampayan, M. Sanders, S. Sullivan, L. Wang, J. A. Watson
  LLNL, Livermore, California
• M. L. Krogh
  University of Missouri - Rolla, Rolla, Missouri
• C. Nunnally
  University of Missouri, Columbia, Columbia, Missouri
• K. Selenes
  TPL, Albuquerque, NM

Progress in the development of compact induction accelerators employing advanced vacuum insulators and dielectrics will be described. These machines will have average accelerating gradients at least an order of magnitude higher than existing machines and can be used for a variety of applications including flash x-ray radiography and medical treatments. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be described.

• J. Carwardine
  
• N. D. Arnold, F. Lenkszus, C. W. Saunders
  ANL, Argonne, Illinois
• B. Banerjee, B. Chase, E. G. Gottschalk, P. W. Joireman, P. A. Kasley, J. R. Lackey, P. M. McBride, J. F. Patrick, V. Pavlicek, M. Votava, S. A. Wolbers
  Fermilab, Batavia, Illinois
• R. W. Downing, R. S. Larsen
  SLAC, Menlo Park, California
• K. Furukawa, S. Michizono
  KEK, Ibaraki
• K. Rehlich, S. Simrock
  DESY, Hamburg

The scale and performance parameters of the ILC require new thinking in regards to control system design. This design work has begun quite early in comparison to most accelerator projects, with the goal of uniquely high overall accelerator availability. Among the design challenges are high control system availability, timing reference distribution, standardization of interfaces, operability, and maintainability. We present the current state of the design and take a prospective look at ongoing research and development projects.

• K. Furukawa
  

• J. Galambos
  
• A. V. Aleksandrov, C. K. Allen, S. Henderson, T. A. Pelaia, A. P. Shishlo, Y. Zhang
  ORNL, Oak Ridge, Tennessee
• P. Chu
  SLAC, Menlo Park, California

The Accelerator Physics group at the Spallation Neutron Source (SNS) has developed numerous codes to assist in the beam commissioning, tuning, and operation of the SNS Linac. These codes have been key to meeting the beam commissioning milestones. For example, a recently developed code provides for rapid retuning of the superconducting Linac in case of RF stations going offline or coming online. Highlights of these "physics applications" will be presented.

• L. Froehlich
  

• G. D'Auria
  
• D. Bacescu, L. Badano, C. Bontoiu, F. Cianciosi, P. Craievich, M. B. Danailov, S. Di Mitri, M. Ferianis, G. C. Pappas, G. Penco, A. Rohlev, A. Rubino, L. Rumiz, S. Spampinati, M. Trovo, A. Turchet, D. Wang
  ELETTRA, Basovizza, Trieste

• A. Gallo
  
• M. Bellaveglia, G. Gatti, C. Vicario
  INFN/LNF, Frascati (Roma)

The SPARC project consists in a 150 MeV B-band, high-brilliance linac followed by 6 undulators for FEL radiation production at 530 nm. The linac assembly has been recently completed. During year 2006 a first experimental phase aimed at characterizing the beam emittance in the first 2m drift downstream the RF gun has been carried out. The low level RF control electronics to monitor and synchronize the RF phase in the gun and the laser shot on the photocathode has been commissioned and extensively tested during the emittance measurement campaign. The laser synchronization has been monitored by measuring the phase of the free oscillation of an RF cavity impulsively excited by the signal of a fast photodiode illuminated by the laser shot. Phase stability measurements are reported, both with and without feedback correction of the slow drifts. A fast intra-pulse phase feedback system to reduce the phase noise produced by the RF power station has been also positively tested.

• C. Vaccarezza
  
• D. Alesini, M. Bellaveglia, S. Bertolucci, R. Boni, M. Boscolo, M. Castellano, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, A. Esposito, M. Ferrario, L. Ficcadenti, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, C. Ligi, M. Migliorati, A. Mostacci, E. Pace, L. Palumbo, L. Pellegrino, M. A. Preger, R. Ricci, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A. Stella, F. Tazzioli, M. Vescovi, C. Vicario
  INFN/LNF, Frascati (Roma)
• F. Alessandria, A. Bacci, R. Bonifacio, I. Boscolo, F. Broggi, F. Castelli, S. Cialdi, C. De Martinis, A. F. Flacco, D. Giove, C. Maroli, V. Petrillo, A. R. Rossi, L. Serafini
  INFN-Milano, Milano
• M. Bougeard, P. Breger, B. Carre, D. Garzella, M. Labat, G. Lambert, H. Merdji, P. Monchicourt, P. Salieres, O. Tcherbakoff
  CEA, Gif-sur-Yvette
• L. Catani, E. Chiadroni, A. Cianchi, E. Gabrielli, C. Schaerf
  INFN-Roma II, Roma
• F. Ciocci, G. Dattoli, A. Dipace, A. Doria, F. Flora, G. P. Gallerano, L. Giannessi, E. Giovenale, G. Messina, P. L. Ottaviani, S. Pagnutti, G. Parisi, L. Picardi, M. Quattromini, A. Renieri, G. Ronci, C. Ronsivalle, M. Rosetti, E. Sabia, M. Sassi, A. Torre, A. Zucchini
  ENEA C. R. Frascati, Frascati (Roma)
• M.-E. Couprie
  SOLEIL, Gif-sur-Yvette
• P. Emma
  SLAC, Menlo Park, California
• M. Mattioli, D. Pelliccia
  Universita di Roma I La Sapienza, Roma
• P. Musumeci, M. Petrarca
  INFN-Roma, Roma
• C. Pellegrini, S. Reiche, J. B. Rosenzweig
  UCLA, Los Angeles, California
• A. Perrone
  INFN-Lecce, Lecce

• T. Kasuga
  
• T. A. Agoh, A. Enomoto, S. Fukuda, K. Furukawa, T. Furuya, K. Haga, K. Harada, S. Hiramatsu, T. Honda, K. Hosoyama, M. Izawa, E. Kako, H. Kawata, M. Kikuchi, Y. Kobayashi, M. Kuriki, T. Mitsuhashi, T. Miyajima, S. Nagahashi, T. Naito, T. Nogami, S. Noguchi, T. Obina, S. Ohsawa, M. Ono, T. Ozaki, S. Sakanaka, H. Sasaki, S. Sasaki, K. Satoh, M. Satoh, T. Shioya, T. Shishido, T. Suwada, M. Tadano, T. Takahashi, Y. Tanimoto, M. Tawada, M. Tobiyama, K. Tsuchiya, T. Uchiyama, K. Umemori, S. Yamamoto
  KEK, Ibaraki
• R. Hajima, H. Iijima, N. Kikuzawa, E. J. Minehara, R. Nagai, N. Nishimori, M. Sawamura
  JAEA/ERL, Ibaraki
• H. Hanaki, H. T. Tomizawa
  JASRI/SPring-8, Hyogo-ken
• A. Ishii, I. Ito, H. Kudoh, N. Nakamura, H. Sakai, S. Shibuya, K. Shinoe, H. Takaki
  ISSP/SRL, Chiba
• M. Katoh, A. Mochihashi, M. Shimada
  UVSOR, Okazaki

• M. Sawamura
  
• T. Furuya, S. Sakanaka, T. Suwada, T. Takahashi, K. Umemori
  KEK, Ibaraki
• H. Sakai, K. Shinoe
  ISSP/SRL, Chiba

• W.-H. Huang
  
• H. Chen, Y.-C. Du, Hua, J. F. Hua, R. K. Li, Y. Lin, J. Shi, C.-X. Tang, D. Xiang, L. X. Yan, P.-CH. Yu
  TUB, Beijing

• A. P. Lee
  
• S.-S. Chang, J.-Y. Hwang, W. K. Lau, C. C. Liang, G.-H. Luo, T.-T. Yang
  NSRRC, Hsinchu

• P. H. Williams
  
• G. J. Hirst
  STFC/RAL, Chilton, Didcot, Oxon
• B. D. Muratori, H. L. Owen, S. L. Smith
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

Studies of the electron beam dynamics for the 4GLS design are presented. 4GLS will provide three different electron bunch trains to a variety of user synchrotron sources. The 1 kHz XUV-FEL and 100 mA High Average Current branches share a common 540 MeV linac, whilst the 13 MHz IR-FEL must be well-synchronised to them. An overview of the injector designs, electron transport, and energy recovery is given, including ongoing studies of coherent synchrotron radiation, beam break-up and wakefields. This work is being pursued for the forthcoming Technical Design Report due in 2008.

• S. L. Smith
  
• N. Bliss
  STFC/DL, Daresbury, Warrington, Cheshire
• A. R. Goulden, G. Priebe
  STFC/DL/SRD, Daresbury, Warrington, Cheshire
• D. J. Holder, P. A. McIntosh
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

• C. Christou
  
• V. C. Kempson
  Diamond, Oxfordshire

• M. Borland
  
• G. Decker, A. Nassiri, M. White
  ANL, Argonne, Illinois

The Advanced Photon Source (APS) is a 7-GeV storage ring light source that has been in operation for over a decade. In order to make revolutionary improvements in the performance of the existing APS ring, we are exploring the addition of a 7-GeV energy recovery linac (ERL) to the APS complex. In this paper, we show the possible configuration of such a system, taking into account details of the APS site and the requirement that stored beam capability be preserved. We exhibit a possible configuration for the single-pass, 7-GeV linac. We discuss optical solutions for transport from 10 MeV to 7 GeV and back, including a large turn-around arc that would support 48 additional user beamlines. Tracking results are shown that include incoherent and coherent synchrotron radiation, resulting in predictions of the beamline performance.

• N. Sereno
  
• M. Borland, H. W. Friedsam
  ANL, Argonne, Illinois

In the recent past, the Advanced Photon Source (APS) was asked by the U. S. Department of Energy to explore a revolutionary upgrade based on emerging energy recovery linac (ERL) technology. In an ERL, the energy of the 7-GeV, 100-mA beam is recovered after the beam passes through user beamlines by decelerating the beam back through the same superconducting linac cavities that accelerated it. The main constraint on this upgrade is that the existing APS beamlines not be disturbed. This requires that the APS storage ring be used as a single-pass transport line in the overall ERL beamline layout. A natural place to locate the ERL is inside the existing APS storage ring ‘‘infield'' area, which has unoccupied space south of the existing APS injector complex. Other important constraints include minimal disturbance of existing building structures and injector beamlines. The existing injector complex would be preserved so that existing operation can be continued through and even possibly beyond ERL commissioning. In this paper, we describe a layout that satisfies these constraints. We also estimate the amount of emittance increase the beam will experience before ring injection.

• E. Trakhtenberg
  
• T. Barsz, P. K. Den Hartog, G. S. Lawrence, E. R. Moog, S. Sasaki, I. Vasserman, M. White
  ANL, Argonne, Illinois
• T. Becker, S. Dufresne, W. Kummerle, R. Schuermann
  Metalex Manufacturing, Cincinnati, Ohio
• G. Goldfarb, N. Lagonsky, S. Lagonsky, S. Sorsher
  Hi-Tech Manufacturing, Schiller Park, Illinois

Design and construction of the undulators for the Linac Coherent Light Source (LCLS) is the responsibility of Argonne National Laboratory. A prototype undulator* was constructed in-house and was extensively tested. The device was tunable to well within the LCLS requirements and was stable over a period of several years. Experience constructing the prototype undulator led us to conclude that with appropriate engineering design and detailed assembly procedures, precision undulators can be constructed by qualified vendors without previous undulator-construction experience. Our detailed technological knowledge and experience were transferred to the successful bidders who have produced outstanding undulators. Our production concept for the 40 3.4 m long, fixed-gap, planar-hybrid undulators with a 30 mm period is presented. Manufacturing, quality assurance, and acceptance testing details are also presented.

*LCLS Prototype Undulator Report, Argonne National Laboratory Report ANL/APS/TB-48, January 2004, R. Dejus, Editor.

• G. J. Waldschmidt
  
• R. M. Lill, L. H. Morrison
  ANL, Argonne, Illinois

A high-resolution X-band cavity beam position monitor (BPM) has been developed for the LCLS in order to achieve micron-level accuracy of the beam position using a dipole mode cavity and a monopole mode reference cavity. The rf properties of the BPM will be discussed in this paper including output power, tuning, and issues of manufacturing. In addition, methods will be presented for improving the isolation of the output ports to differentiate between horizontal/vertical beam motion and to reject extraneous modes from affecting the output signal. The predicted simulation results will be compared to data collected from low-power experimental tests.

• G. Hoffstaetter
  
• Ch. Spethmann, Y. Xie
  CLASSE, Ithaca

In an energy recovery linac (ERL) where beam-loss has to be minimal, and where beam positions and emittances have to be very stable in time, optic errors and beam instabilities due to ion effects have to be avoided. Here we explain why ion clearing electrodes are the least unattractive way of eliminating ions in an ERL and we present calculations of the remnant ion density and its effect on the beam. We also show a design of the clearing electrodes that should be distributed around the accelerator and illustrate their wake-field properties.

• C. Song
  
• G. Hoffstaetter
  CLASSE, Ithaca

Multi-pass, multi-bunch beam-breakup (BBU) can limit the current in linac-based recirculating accelerators. We have therefore made the computation of the transverse and longitudinal BBU-threshold current available in Cornell's main optics design and beam simulation library BMAD. The coupling of horizontal and vertical motion as well as time of flight effects are automatically contained. Subsequently we present a detailed simulation study of transverse and longitudinal BBU in the proposed 5GeV Energy Recovery Linac light source at Cornell University, including the use of frequency randomization, polarized cavities and optical manipulations to improve the threshold current.

• J. Bisognano
  
• R. A. Bosch, M. A. Green, H. Hoechst, K. Jacobs, K. J. Kleman, R. A. Legg, R. Reininger, R. Wehlitz
  UW-Madison/SRC, Madison, Wisconsin
• J. Chen, W. Graves, F. X. Kaertner, J. Kim, D. E. Moncton
  MIT, Cambridge, Massachusetts

The University of Wisconsin-Madison and its partners are developing a design for an FEL operating in the UV to soft x-ray range that will be proposed as a new multidisciplinary user facility. Key features of this facility include seeded, fully coherent output with tunable photon energy and polarization over the range 5 eV to 1240 eV, and simultaneous, independent operation of multiple beamlines. The different beamlines will support a wide range of science from femto-chemistry requiring ultrashort pulses with kHz repetition rates to photoemission and spectroscopy requiring high average flux and narrow bandwidth at MHz rates. The facility will take advantage of the flexibility, stability, and high average pulse rates available from a CW superconducting linac driven by a photoinjector. This unique facility is expected to enable new science through ultra-high resolution in the time and frequency domains, as well as coherent imaging and nano-fabrication. This project is being developed through collaboration between the UW Synchrotron Radiation Center and MIT. We present an overview of the facility, including the motivating science, and its laser, accelerator, and experimental systems.

• J. Bisognano
  
• R. A. Bosch, M. A. Green, K. Jacobs, K. J. Kleman, R. A. Legg
  UW-Madison/SRC, Madison, Wisconsin
• J. Chen, W. Graves, F. X. Kaertner, J. Kim
  MIT, Cambridge, Massachusetts

We present an initial design of the driver for the Wisconsin VUV/Soft Xray FEL facility, which will provide high intensity coherent photons from 5 eV to 1.2 keV. It uses a 2.5 GeV, L-band CW superconducting linac with a 1.7 GeV tap-off to feed the lower energy FELs. In order to support multiple high rep-rate FELs, the average design current is 1 mA. Sub-nanocoulomb bunches with normalized transverse emittances of order 1 micron are generated in a photoinjector for beamlines operating at repetition rates from kHz to MHz. Multi-stage bunch compression provides 1 kA peak current to the FELs, with low energy spread and a suitable current profile. Compressed bunch lengths of several hundred femtoseconds will allow generation of photon pulses in the range 10 to 100 fs using cascaded FELs. Consideration has been given to removing the residual energy chirp from the beam, and minimizing the effects of space charge, coherent synchrotron radiation, and microbunching instabilities. A beam switchyard using RF separators and fast kickers delivers the desired electron bunches to each of the FELs. Details of the design will be presented, including those areas requiring the most development work.

• R. A. Bosch
  
• J. Bisognano, M. D. Medley
  UW-Madison/SRC, Madison, Wisconsin

A 980-MeV energy recovery linac with radiofrequency (rf) of 1.5 GHz is designed. Electrons are accelerated by two passages through a 480-MeV superconducting linac, and decelerated by two subsequent passages. Recirculation is accomplished with six 60-degree bending magnets. The threshold current for beam breakup instability exceeds 100 mA. Gaussian bunches with normalized transverse emittances of 0.1 mm-mrad and rms length of 1.85 ps may be compressed by a factor of 180 (to a bunch length of 10 fs) with only a slight increase in transverse normalized emittance. Bunch charges up to 8 pC may be compressed at 980 MeV without excessive degradation from coherent synchrotron radiation, allowing operation with beam currents up to 12 mA.

• P. Emma
  
• R. Akre, J. Castro, Y. T. Ding, D. Dowell, J. C. Frisch, A. Gilevich, G. R. Hays, P. Hering, Z. Huang, R. H. Iverson, P. Krejcik, C. Limborg-Deprey, H. Loos, A. Miahnahri, C. H. Rivetta, M. E. Saleski, J. F. Schmerge, D. C. Schultz, J. L. Turner, J. J. Welch, W. E. White, J. Wu
  SLAC, Menlo Park, California
• L. Froehlich, T. Limberg, E. Prat
  DESY, Hamburg

The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project presently under construction at SLAC. The injector section, from drive-laser and RF photocathode gun through the first bunch compressor chicane, was installed during the Fall of 2006. Initial system commissioning with an electron beam takes place in the Spring and Summer of 2007. The second phase of construction, including the second bunch compressor and the FEL undulator, will begin later, in the Fall of 2007. We report here on experience gained during the first phase of machine commissioning, including RF photocathode gun, linac booster section, energy spectrometers, S-band and X-band RF systems, the first bunch compressor stage, and the various beam diagnostics.

• Z. R. Wolf
  
• V. Kaplounenko, Yu. I. Levashov, A. W. Weidemann
  SLAC, Menlo Park, California

The LCLS x-ray free electron laser project at SLAC requires 40 undulators: 33 in the beamline, 6 spares, and one reference undulator. A new facility was constructed at SLAC for tuning and fiducializing the undulators. The throughput of the facility must be approximately one undulator per week. Much effort has gone into automating the undulator tuning. Because of tight alignment tolerances, accurate techniques were developed to fiducialize the undulators. The new facility, the tuning techniques, and the fiducialization techniques will be discussed.

• V. Litvinenko
  
• J. Alduino, D. Beavis, I. Ben-Zvi, M. Blaskiewicz, J. M. Brennan, A. Burrill, R. Calaga, P. Cameron, X. Chang, K. A. Drees, G. Ganetis, D. M. Gassner, J. G. Grimes, H. Hahn, L. R. Hammons, A. Hershcovitch, H.-C. Hseuh, A. K. Jain, D. Kayran, J. Kewisch, R. F. Lambiase, D. L. Lederle, C. Longo, G. J. Mahler, G. T. McIntyre, W. Meng, T. C. Nehring, B. Oerter, C. Pai, D. Pate, D. Phillips, E. Pozdeyev, T. Rao, J. Reich, T. Roser, T. Russo, Z. Segalov, J. Smedley, K. Smith, J. E. Tuozzolo, G. Wang, D. Weiss, N. Williams, Q. Wu, K. Yip, A. Zaltsman
  BNL, Upton, Long Island, New York
• H. Bluem, M. D. Cole, A. J. Favale, D. Holmes, J. Rathke, T. Schultheiss, A. M.M. Todd
  AES, Princeton, New Jersey
• B. W. Buckley
  CLASSE, Ithaca
• G. Citver
  Stony Brook University, StonyBrook
• J. R. Delayen, L. W. Funk, H. L. Phillips, J. P. Preble
  Jefferson Lab, Newport News, Virginia

In this paper we present status and plans for the 20-MeV R&D energy recovery linac, which is under construction at Collider Accelerator Department at BNL. The facility is based on high current (up to 0.5 A of average current) super-conducting 2.5 MeV RF gun, single-mode super-conducting 5-cell RF linac and about 20-m long return loop with very flexible lattice. The R&D ERL, which is planned for commissioning in 2008, aims to address many outstanding questions relevant for high current, high brightness energy-recovery linacs.

• J. Rose
  
• I. Pinayev, T. V. Shaftan
  BNL, Upton, Long Island, New York

• J. Smedley
  
• J. Iversen, D. Klinke, D. Kostin, W.-D. Moller, A. Muhs, J. S. Sekutowicz
  DESY, Hamburg
• P. Kneisel
  Jefferson Lab, Newport News, Virginia
• R. S. Lefferts, A. R. Lipski
  SBUNSL, Stony Brook, New York
• T. Rao
  BNL, Upton, Long Island, New York

We report recent progress in the development of a hybrid lead/niobium superconducting (SC) injector. The goal of this effort is to produce an all-SC injector with the SCRF properties of a niobium cavity along with the superior quantum efficiency (QE) of a lead photocathode. Two prototype hybrid injectors have been constructed, one utilizing a cavity with a removable cathode plug, and a second consisting of an all-niobium cavity arc-deposited with lead in the cathode region. We present the results of QE measurements on these cavities, along with tests of the effect of the laser on the cavity RF performance.

• M. Marchetto
  
• R. E. Laxdal, V. Zviagintsev
  TRIUMF, Vancouver

• G. Clemente
  
• L. Groening
  GSI, Darmstadt
• S. Minaev
  ITEP, Moscow
• H. Podlech, U. Ratzinger, R. Tiede
  IAP, Frankfurt am Main

The FAIR facility, under development at GSI, needs a new dedicated proton injector for the production of intense antiprotons secondary beams. This injector will accelerate protons from 3 to 70 MeV at a current of 70 mA, and due to the high voltage gain and shunt impedance will be based on CH cavities powered by a 2.5 MW, 325 MHz klystron. An innovative coupling cell containing one drift tube of length N-beta λ was developed to combine multicell drift tube modules of the CH-type (H210 mode).. In order to study this innovative coupling mechanism a scaled model of the second resonator of GSI Proton injector is under production at IAP. The according full scale prototype, 3 meter long coupled X MV resonator from MeV to MeV is under construction and will be power tested with a 2.5 MW klystron at GSI at the end of 2008. This paper describes in detail the coupled structure together with a general overview of the R&D results achieved on the CH-DTL's cavity.

• H. Podlech
  
• M. Busch, H. Klein, H. Liebermann, U. Ratzinger, A. C. Sauer, R. Tiede
  IAP, Frankfurt am Main

• A. Schempp
  
• B. Hofmann
  IAP, Frankfurt am Main
• O. K. Kester
  GSI, Darmstadt

• A. Schempp
  
• J. G. Alessi, D. Raparia, L. Snydstrup
  BNL, Upton, Long Island, New York
• U. Ratzinger, R. Tiede, C. Zhang
  IAP, Frankfurt am Main

• H. Akikawa
  
• Z. Igarashi, M. Ikegami, S. Lee
  KEK, Ibaraki
• S. Sato, T. Tomisawa, A. Ueno
  JAEA/LINAC, Ibaraki-ken
• G. B. Shen
  JAEA, Ibaraki-ken

• M. Ikegami
  
• H. Asano, T. Kobayashi
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• K. Hasegawa, T. Ito, T. Morishita, S. Sato, A. Ueno
  JAEA/LINAC, Ibaraki-ken
• Z. Igarashi, H. Tanaka
  KEK, Ibaraki
• H. Sako
  JAEA, Ibaraki-ken

• H. Ao
  
• K. Hasegawa
  JAEA, Ibaraki-ken
• K. Hirano, T. Morishita, A. Ueno
  JAEA/LINAC, Ibaraki-ken
• M. Ikegami
  KEK, Ibaraki
• V. V. Paramonov
  RAS/INR, Moscow
• Y. Yamazaki
  KEK/JAEA, Ibaraki-Ken

• T. Ito
  
• H. Ao
  JAEA/LINAC, Ibaraki-ken
• H. Asano, T. Morishita
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• T. Kato, F. Naito, E. Takasaki, H. Tanaka
  KEK, Ibaraki

• T. Morishita
  
• H. Asano, M. Ikegami
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• K. Hasegawa
  JAEA, Ibaraki-ken
• A. Ueno
  JAEA/LINAC, Ibaraki-ken

• T. Morishita
  
• H. Asano, M. Ikegami, T. Ito
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• K. Hasegawa
  JAEA, Ibaraki-ken
• F. Naito, E. Takasaki, H. Tanaka, K. Yoshino
  KEK, Ibaraki
• A. Ueno
  JAEA/LINAC, Ibaraki-ken

• G. B. Shen
  
• H. Sako
  JAEA, Ibaraki-ken
• S. Sato
  JAEA/LINAC, Ibaraki-ken

• M. Yamamoto
  
• S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Toda, M. Yoshii
  KEK, Ibaraki
• K. Hasegawa, M. Nomura, A. Schnase, F. Tamura
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

• Y.-S. Cho
  
• B. Chung, J.-H. Jang, K. Y. Kim, Y.-H. Kim
  KAERI, Daejon

The Proton Engineering Frontier Project (PEFP) will supply 20-MeV and 100-MeV proton beams from a 100 MeV proton linear accelerator for beam applications. The extracted 20 MeV or 100 MeV proton beams will be simultaneously distributed into the five targets through a dipole magnet equipped with a controllable AC power supply. The most important design criterion is the flexibility of the irradiation conditions in order to meet various user requirements in many application fields. For this purpose, we have designed the beamlines to the targets for wide or focused beams, external or in-vacuum beams, and horizontal or vertical beams. This work includes details of the conceptual design of the beamlines.

• J.-H. Jang
  
• Y.-S. Cho, K. Y. Kim, H.-J. Kwon
  KAERI, Daejon

The 100 MeV Linac of the Proton Engineering Frontier Project (PEFP) consists of an ion source, a low energy beam transport (LEBT), a 3 MeV radio frequency quadrupole (RFQ), and an 100 MeV drift tube linac (DTL). The DTL is separated into two parts. The first part includes 4 tanks which accelerate 20 mA proton beams up to 20 MeV. The medium energy beam transport (MEBT) follows the 20 MeV accelerator in order to match proton beams into the next linac as well as to extract and supply 20 MeV proton beams to the user facilities. The second part of the DTL consists of 7 tanks to accelerate proton beams to 100 MeV. This work focuses on the error analysis of the designed 100 MeV linac in order to obtain the tolerance limit in the fabrication and alignment processes of the linac as well as to study the steering magnets which control the beam fluctuations and reduce the potential beam loss.

• Y.-H. Kim
  
• Y.-S. Cho, J.-H. Jang
  KAERI, Daejon

The PEFP DTL II which accelerates a proton beam from the energy of 20MeV Beam to 100MeV is now under fabrication. The DTL II which has some similar specifications with the DTL I which accelerates the proton beam to the energy of 20MeV is made of seamless carbon steel with Cu electroplating inside. The DTL tank is divided into 3 sections whose length is about 2.2m. We verified the mechanical and thermal stability using ANSYS code, and we established the fabrication process of the drift tube. The DTL II is now being fabricated.

• E. S. Masunov
  
• S. M. Polozov
  MEPhI, Moscow

* E. S. Masunov, Technical Physics, V. 46, 11, 2001, pp. 1433-1436.**E. S. Masunov, S. M. Polozov, NIM., A 558, 2006, pp. 184-187.

• E. S. Masunov
  
• A. V. Samoshin
  MEPhI, Moscow

• F. Gerigk
  
• M. Aiba, C. Carli, M. Martini
  CERN, Geneva
• S. M. Cousineau
  ORNL, Oak Ridge, Tennessee

• W. J.M. Weterings
  
• G. Bellodi, J. Borburgh, T. Fowler, F. Gerigk, B. Goddard, K. Hanke, M. Martini, L. Sermeus
  CERN, Geneva

• J. K. Pozimski
  
• J. Alonso, R. Enparantza
  Fundacion Tekniker, Elbr (Guipuzkoa)
• J. J. Back
  University of Warwick, Coventry
• J. Bermejo
  Bilbao, Faculty of Science and Technology, Bilbao
• Y. A. Cheng, S. Jolly, A. Kurup, P. Savage
  Imperial College of Science and Technology, Department of Physics, London
• M. A. Clarke-Gayther, A. Daly, D. C. Faircloth, A. P. Letchford
  STFC/RAL/ISIS, Chilton, Didcot, Oxon
• C. Gabor, D. C. Plostinar
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon
• J. Lucas
  Elytt Energy, Madrid

• M. A. Clarke-Gayther
  

A description is given of slow-wave chopper structures for the 3.0 MeV, 60 mA, H^- MEBT lines of the CERN Linac 4 and RAL Front-End Test Stands (FETS). Transmission line properties and transverse E-field uniformity for the original European Spallation Source (ESS) designs* have been refined by modelling static, and time dependent electromagnetic fields in the 3D CST 'EM Studio', and 'Microwave Studio' codes**. In addition, the original compact, radiation hard, vacuum compatible designs have been simplified and reconfigured to be compatible with standard NC machining practice. Transmission line properties in the frequency and time domain, together with E-field uniformity in the axial and transverse planes, are presented.

* M. A. Clarke-Gayther, 'Slow-wave electrode structures for the ESS 2.5 MeV fast chopper', Proc. of the 2003 Particle Accelerator Conference (PAC), Portland, Oregon, USA, p. 1473-1475.** www.cst.com

• D. C. Plostinar
  

• D. C. Plostinar
  
• E. Zh. Sargsyan
  CERN, Geneva

CERN and RAL are working in parallel to develop Front Ends for future particle accelerators. At CERN the Front End will be part of LINAC4, a potential replacement for the Linac2 accelerator, whilst at RAL the Front End is intended to demonstrate that a high current, high quality chopped beam is achievable and that the design could be used as part of a Proton Driver for a future Neutrino Factory. The two Front End designs have many similarities and basically consist of four main components: an H^- ion source, a Low Energy Beam Transport (LEBT) matching into a Radio-Frequency Quadrupole (RFQ) and a Medium Energy Beam Transport (MEBT) line with a fast beam chopper. The beam choppers are different in the two designs and it is important to compare the effectiveness of the two methods of operation. This paper describes a simulation study of high intensity beam dynamics and beam transport when the RAL and CERN MEBT designs are each fed into the same CERN structure for LINAC4.

• P. N. Ostroumov
  
• B. Mustapha, J. A. Nolen
  ANL, Argonne, Illinois

The Advanced Exotic Beam Laboratory (AEBL) being developed at ANL consists of an 833 MV heavy-ion driver linac capable of producing uranium ions up to 200 MeV/u and protons to 580 MeV with 400 kW beam power. We have designed all accelerator components including a two charge state LEBT, an RFQ, a MEBT, a superconducting linac, a stripper section and beam switchyard. We present the results of an optimized linac design and end-to-end simulations which include possible machine errors.

• P. N. Ostroumov
  
• J. D. Fuerst, M. P. Kelly, B. Mustapha, J. A. Nolen, K. W. Shepard
  ANL, Argonne, Illinois

The Office of Science of the Department of Energy is currently considering options for an advanced radioactive beam facility in the U. S. The U. S. facility will complement capabilities both existing and planned elsewhere. As envisioned at ANL, the facility, called the Advanced Exotic Beam Laboratory (AEBL), would consist of a heavy-ion driver linac, a post-accelerator and experimental areas. The proposed design of the AEBL driver linac is a cw, fully superconducting, 833 MV linac capable of accelerating uranium ions up to 200 MeV/u and protons to 580 MeV with 400 kW beam power. An extensive research and development effort has resolved many technical issues related to the construction of the driver linac and other systems required for AEBL. This paper presents the status of planning, some options for such a facility, as well as, progress in related R&D.

• D. E. Johnson
  
• A. Z. Chen, I. Rakhno
  Fermilab, Batavia, Illinois

A 8 GeV H^- superconducting linac has been proposed as an alternative injector for the Main Injector to support a 2 MW Neutrino program. An injection absorber is required to accept protons generated after the secondary stripping foil which will intercept the un-stripped H^- and H0 particles after the MI primary foil injection point. The motivations underlying the choice of a compact internal absorber over an external absorber will be discussed. We show that using a high-Z material (tungsten) for the inner shielding allows the construction a compact absorber that can take a very intense beam and fits within the existing enclosure. The absorber requirements and a shielding design and the results of energy deposition calculations are presented.

• D. E. Johnson
  
• J. Beebe-Wang, C. J. Liaw, D. Raparia
  BNL, Upton, Long Island, New York

The technique for H^- charge exchange for multi-turn injection utilizing stripping foils in the energy range of a few hundred MeV has been used at many labs for decades and most recently up to 1 GeV at the SNS. Utilization the beam from the proposed Proton Driver* would permit the extension of this technique up to 8 GeV. The injection layout and required accelerator modifications are discussed. Results from transverse and longitudinal simulations are presented.

* W. G. Foster and J. A. MacLachlan, "A Multi-mission 8 GeV Injector Linac as a Fermilab Booster Replacement", Proc. Of LINAC-2002, Gyeongju, Korea, p.86.

• A. I. Drozhdin
  
• W. Pellico, X. Yang
  Fermilab, Batavia, Illinois

• X. Wu
  
• G. Bollen, M. Doleans, T. L. Grimm, F. Marti, S. Schwarz, R. C. York, Q. Zhao
  NSCL, East Lansing, Michigan

Rare Isotope Beams (RIBs) are created at the National Superconducting Cyclotron Laboratory (NSCL) by the in-flight particle fragmentation method. A novel system is proposed to stop the RIBS in a helium filled gas system followed by reacceleration that will provide opportunities for an experimental program ranging from low-energy Coulomb excitation to transfer reaction studies of astrophysical reactions. The beam from the gas stopper will first be brought into a Electron Beam Ion Trap (EBIT) charge breeder on a high voltage platform to increase its charge state and then accelerated initially up to about 3 MeV/u by a system consisting of an external multi-harmonic buncher and a radio frequency quadrupole (RFQ) followed a superconducting linac. The superconducting linac will use quarter-wave resonators with bopt of 0.047 and 0.085 for acceleration and superconducting solenoid magnets for transverse focusing. The paper will discuss the accelerator system design and present the end-to-end beam dynamics simulations.

• Q. Zhao
  
• V. Andreev, F. Marti, S. O. Schriber, X. Wu, R. C. York
  NSCL, East Lansing, Michigan

• Q. Zhao
  
• M. Doleans, T. L. Grimm, F. Marti, S. O. Schriber, X. Wu, R. C. York
  NSCL, East Lansing, Michigan

• K. W. Jones
  
• J. L. Erickson, F. R. Gallegos
  LANL, Los Alamos, New Mexico

At the core of the Los Alamos Neutron Science Center (LANSCE) accelerator lies an 800-MeV proton linac that drives user facilities for isotope production, proton radiography, ultra-cold neutrons, weapons neutron research and for various sciences using neutron scattering. LANSCE is in the planning phase of a refurbishment project that will sustain reliable facility operations well into the next decade. The general goals for LANSCE-R are to (1) preserve dependable operation of the linac and (2) increase the cost effectiveness of operations. Requirements can be met for overall beam intensity, availability, and reliability with long-term sustainability and minimal disruption to scheduled user programs. The baseline refurbishment project consists of replacing the 201 MHz RF systems, upgrading a substantial fraction of the 805 MHz RF systems, updating the control system, and replacing or improving a variety of diagnostics and accelerator subsystems. The plans for the various LANSCE-R improvements will be presented and the preliminary cost and schedule estimates will be discussed.

• L. Rybarcyk
  
• J. T.M. Lyles
  LANL, Los Alamos, New Mexico

The LANSCE linac simultaneously provides both H⁺ and H^- beams to several user facilities. The Weapons Neutron Research (WNR) user facility is configured to accept the H^- beam with a typical pulse pattern of one linac micro-pulse every 1.8 microseconds. To produce this pulse spacing a slow-wave chopper located in the 750 keV injector beam transport is employed to intensity modulate the beam. The beam is subsequently bunched at both 16.77 MHz and 201.25 MHz prior to entering the 100 MeV drift tube linac. One downside of the chopping process is that the majority of the beam produced by the ion source during the WNR macro-pulses is discarded. By applying a longitudinal bunching action immediately following the ion source, simulations have shown that some of this discarded beam can be used to increase the charge in these micro-pulses. Recently, we began an effort to develop this buncher by superimposing 16.77 MHz RF voltage on one of the HVDC electrodes in the 80 kV column located inside H^- Cockcroft-Walton dome. This paper describes the beam dynamics simulations, design and implementation of the rf hardware and the results of tests performed with the system.

• A. V. Aleksandrov
  
• C. Deibele
  ORNL, Oak Ridge, Tennessee

The chopper system for the Spallation Neutron Source (SNS) provides a gap in the beam for clean extraction from the accumulator ring. It consists of a pre-chopper in the low energy beam transport and a faster chopper in the medium energy beam transport (MEBT). The original "meander line" design of the MEBT chopper deflector was successfully tested with low power beam during the SNS linac commissioning but turned out to be unsuitable for high power beam operation due to poor cooling of the copper strip line through the dielectric substrate. We developed a new deflecting structure, with higher deflection efficiency and with rise and fall time easily customizable to match the available high voltage pulse generator. In this paper we describe design, implementation and beam tests results of the new MEBT chopper deflector.

• A. V. Aleksandrov
  
• S. Assadi, W. Blokland, P. Chu, S. M. Cousineau, V. V. Danilov, C. Deibele, J. Galambos, S. Henderson, D.-O. Jeon, M. A. Plum, A. P. Shishlo, M. P. Stockli, Y. Zhang
  ORNL, Oak Ridge, Tennessee

The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H^- injector, capable of producing one-ms-long pulses at 60 Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The 2.5 MeV beam from the Front End is accelerated to 86 MeV in the Drift Tube Linac, then to 185 MeV in a Coupled-Cavity Linac and finally to 1 GeV in the Superconducting Linac. With the completion of beam commissioning, the accelerator complex began operation in June 2006 and beam power is being gradually ramped up toward the design goal. Operational experience with the injector and linac will be presented including chopper performance, transverse emittance evolution along the linac, and the results of a beam loss study.

• J. D. Sherman
  
• F. W. Guy, W. J. Starling, D. A. Swenson, C. A. Willis
  Linac Systems, Albuquerque, New Mexico
• J. M. Potter
  JP Accelerator Works, Los Alamos, New Mexico

• M. E. Conde
  

There has been continued interest in the development of dielectric-loaded wakefield structures that can be used to accelerate particle beams. The present search for materials able to withstand very intense RF fields has renewed this interest. Recent experiments at the Argonne Wakefield Accelerator have generated short RF pulses with accelerating fields in excess of 80 MV/m. These experiments used ceramic-lined cylindrical waveguides, operating at frequencies between 10 and 15 GHz. Other important experiments, at different RF frequencies and using planar or cylindrical geometries, have been carried out at various other facilities. A number of new experiments are planned in the near future to explore the capabilities of this class of structures. This presentation will provide an up-to-date survey of the activities in this area of research.

• S. Seletskiy
  
• P. Tenenbaum
  SLAC, Menlo Park, California

• D. Proch
  

• T. M. Himel
  
• J. Nelson, N. Phinney
  SLAC, Menlo Park, California
• M. C. Ross
  Fermilab, Batavia, Illinois

The International Linear Collider will be the largest most complicated accelerator ever built. For this reason extensive work is being done early in the design phase to ensure that it will be reliable enough. This includes gathering failure mode data from existing accelerators and simulating the failures and repair times of the ILC. This simulation has been written in a general fashion using MATLAB and could be used for other accelerators. Results from the simulation tool have been used in making some of the major ILC design decisions and an unavailability budget has been developed.

• N. Solyak
  
• V. Ivanov, C. S. Mishra, K. Ranjan
  Fermilab, Batavia, Illinois

International Linear Collider (ILC) is a proposed electron-positron accelerator requiring very small spot-size at the interaction point, and thus necessitates very tight tolerances on beamline elements. For static tuning of the machine a few methods like dispersion-free steering (DFS) or kick minimization (KM) techniques was proposed. The further suppression of emittance growth can be achieved by using close orbit emittance bumps. Stability of ILC is determined by the stability of the site, additional noises of beamline component, energy and kicker jitter and performance of the train-to-train and intra-train feedback. We discuss the performances of the Adaptive Alignment technique, which keeps accelerator dynamically aligned in presence of ground motion an technical noises. This presentation is an overview of two posters THPMN107 and THPMN108, presented at PAC07.

• R. Corsini
  

• R. D. Kephart
  

• A. Seryi
  
• I. V. Agapov, G. A. Blair, S. T. Boogert, J. Carter
  Royal Holloway, University of London, Surrey
• M. Alabau, P. Bambade, J. Brossard, O. Dadoun
  LAL, Orsay
• J. A. Amann, R. Arnold, F. Asiri, K. L.F. Bane, P. Bellomo, E. Doyle, A. F. Fasso, L. Keller, J. Kim, K. Ko, Z. Li, T. W. Markiewicz, T. V.M. Maruyama, K. C. Moffeit, S. Molloy, Y. Nosochkov, N. Phinney, T. O. Raubenheimer, S. Seletskiy, S. Smith, C. M. Spencer, P. Tenenbaum, D. R. Walz, G. R. White, M. Woodley, M. Woods, L. Xiao
  SLAC, Menlo Park, California
• M. Anerella, A. K. Jain, A. Marone, B. Parker
  BNL, Upton, Long Island, New York
• D. A.-K. Angal-Kalinin, C. D. Beard, J.-L. Fernandez-Hernando, P. Goudket, F. Jackson, J. K. Jones, A. Kalinin, P. A. McIntosh
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• R. Appleby
  UMAN, Manchester
• J. L. Baldy, D. Schulte
  CERN, Geneva
• L. Bellantoni, A. I. Drozhdin, V. S. Kashikhin, V. Kuchler, T. Lackowski, N. V. Mokhov, N. Nakao, T. Peterson, M. C. Ross, S. I. Striganov, J. C. Tompkins, M. Wendt, X. Yang
  Fermilab, Batavia, Illinois
• K. Buesser
  DESY, Hamburg
• P. Burrows, G. B. Christian, C. I. Clarke, A. F. Hartin
  OXFORDphysics, Oxford, Oxon
• G. Burt, A. C. Dexter
  Cockcroft Institute, Warrington, Cheshire
• J. Carwardine, C. W. Saunders
  ANL, Argonne, Illinois
• B. Constance, H. Dabiri Khah, C. Perry, C. Swinson
  JAI, Oxford
• O. Delferriere, O. Napoly, J. Payet, D. Uriot
  CEA, Gif-sur-Yvette
• C. J. Densham, R. J.S. Greenhalgh
  STFC/RAL, Chilton, Didcot, Oxon
• A. Enomoto, S. Kuroda, T. Okugi, T. Sanami, Y. Suetsugu, T. Tauchi
  KEK, Ibaraki
• A. Ferrari
  UU/ISV, Uppsala
• J. Gronberg
  LLNL, Livermore, California
• Y. Iwashita
  Kyoto ICR, Uji, Kyoto
• W. Lohmann
  DESY Zeuthen, Zeuthen
• L. Ma
  STFC/DL, Daresbury, Warrington, Cheshire
• T. M. Mattison
  UBC, Vancouver, B. C.
• T. S. Sanuki
  University of Tokyo, Tokyo
• V. I. Telnov
  BINP SB RAS, Novosibirsk
• E. T. Torrence
  University of Oregon, Eugene, Oregon
• D. Warner
  Colorado University at Boulder, Boulder, Colorado
• N. K. Watson
  Birmingham University, Birmingham
• H. Y. Yamamoto
  Tohoku University, Sendai

• H. Burkhardt
  
• I. V. Agapov, G. A. Blair
  Royal Holloway, University of London, Surrey
• F. Jackson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• A. Latina, L. Neukermans, D. Schulte
  CERN, Geneva

Halo simulations and estimates are important for the design of future linear accelerators. We present simulations performed for the ILC and CLIC and compare these with semi-analytical estimates and other simulations.

• K. Fong
  
• M. P. Laverty, Q. Zheng
  TRIUMF, Vancouver

• H. Podlech
  
• A. Bechtold, H. Liebermann, U. Ratzinger
  IAP, Frankfurt am Main

The superconducting CH-structure is the first multi-cell cavity for the acceleration of low and medium energy ions and protons. A superconducting prototype cavity has been built and several cold tests have been performed at the IAP in Frankfurt. After the detection of a field emission centre the cavity will be treated by buffered chemical polishing and high pressure rinsing. Additionally the cavity is being prepared for tests in a horizontal cryostat with slow and fast tuner system. We present the status of these developments and the test results which have been gained recently.

• R. Amirikas
  
• A. Bertolini, W. Bialowons
  DESY, Hamburg

The European X-ray Free Electron Laser (XFEL) and the International Linear Collider (ILC) superconducting accelerating modules, containing a string of Niobium (Nb) cavities and a quadrupole, will operate at 2K. In this paper, we will report on the vibration stability studies of a high gradient XFEL/ILC type III superconducting accelerating module quadrupole operating at 4.5K. Measurements are performed via geophones affixed on the cold mass in both horizontal and vertical directions. This data will be compared with piezoelectric accelerometers for the same module. The goal is to study the stability of the cold quadrupole and to compare the results with room temperature conditions.

• M. K. Grecki
  
• W. Koprek, S. Simrock
  DESY, Hamburg

Measurements of effective Radio Frequency (RF) field parameters (amplitude and phase) are tasks of great importance in high-energy accelerators*. The RF signal is downconverted in frequency to intermediate frequency (IF) but keeping the information about amplitude and phase. The IF signal is then sampled in ADC and processed in digital IQ detector computing the I and Q components**. The downconverter is a nonlinear device thus not only the fundamental frequency but also its harmonics are present and sampled by ADC. For a typical downconverter (used in FLASH LLRF system) the higher order harmonics levels depend on RF signal level and are about 40dBm lower than the fundamental frequency component. These harmonics can produce errors in IQ detector of up to few percent in amplitude and few degree in phase. These errors depends not only on nonlinearity of downconverter but also on the IQ detection scheme*** (IF and sampling rate SR). The paper presents the optimization of the IQ detection scheme (choosing the IF and SR) taking into account the nonlinear characteristics of the downconverter.

*Grelick A. et all:A High-Resolution…, Proc. LINAC 2004,715-718**Grecki M. et all:Estimation of IQ…, Proc. MIXDES 2005,783-788***Simrock S. et all:Considerations…, Proc. EPAC 2006,1462-1464

• V. Vogel
  
• A. Cherepenko
  BINP SB RAS, Novosibirsk
• S. Choroba, T. Froelich, T. G. Grevsmuehl, F.-R. Kaiser, V. V. Katalev, I. S. Sokolov, H. Timm
  DESY, Hamburg

• A. Fabris
  
• M. Bocciai, L. Bortolossi, M. Ottobretti, C. Pasotti, M. Rinaldi, M. Svandrlik
  ELETTRA, Basovizza, Trieste

• V. G. Vaccaro
  
• R. Buiano
  Naples University Federico II and INFN, Napoli
• A. D'Elia
  CERN, Geneva
• D. Davino
  Universita' degli Studi del Sannio, Benevento
• C. De Martinis, D. Giove
  INFN-Milano, Milano
• M. R. Masullo
  INFN-Napoli, Napoli

For an assembled structure (module, tank) of a Linac, the single cells, when coupled, loose their individuality and in cooperation contribute to the generation of the structure modes (resonant frequencies) Fm. On the other end these modes are the only measurable quantities. The system of the coupled cells can be modelled, in a narrow frequency band, as a lumped constant circuit. The modes are solution of an equation obtained equating to zero the determinant relevant to the lumped circuit. This is an algebraic equation of the same order as the number N of cells. A plausible question can be posed: is it possible from a manipulation of the measurable quantities (Fm) to draw the lumped circuit parameters, namely coupling constants and single cell resonant frequencies? The answer is positive if a certain degree of symmetry is satisfied. The coefficients of above mentioned equation can be easily related to the measured modes Fm. By varying, by means of tuners, the tune of a single cell of a small unknown amount, any couple of equation coefficient moves on a straight line. Therefore, we have N(N-1) known straight line coefficients which may give the unknowns with extremely high accuracy.

• C. Pagani
  
• A. Bosotti, N. Panzeri
  INFN/LASA, Segrate (MI)

• K. Shirasawa
  
• H. Baba, H. Matsumoto
  KEK, Ibaraki
• T. Inagaki, H. Kitamura, T. Shintake
  RIKEN Spring-8 Harima, Hyogo
• S. Miura
  MHI, Hiroshima

• Z. Fang
  
• S. Anami, S. Michizono, S. Yamaguchi
  KEK, Ibaraki
• T. Kobayashi
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• H. Suzuki
  JAEA, Ibaraki-ken

• T. Higo
  
• F. Furuta, Y. Higashi, T. Saeki, K. Saito, M. Satoh, H. Yamaoka
  KEK, Ibaraki

• S. Michizono
  
• S. Fukuda, H. Katagiri, T. Matsumoto, T. Miura, Y. Yano
  KEK, Ibaraki
• Z. Geng
  IHEP Beijing, Beijing

• K. Yokoyama
  
• Y. Higashi, T. Higo, N. K. Kudo, S. Ohsawa
  KEK, Ibaraki

• F. Tamura
  
• S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Toda, M. Yoshii
  KEK, Ibaraki
• K. Hasegawa, M. Nomura, A. Schnase, M. Yamamoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

• T. Kobayashi
  
• S. Anami, Z. Fang, Y. Fukui, M. Kawamura, S. Michizono, K. Nanmo, S. Yamaguchi
  KEK, Ibaraki
• E. Chishiro, T. Hori, H. Suzuki, M. Yamazaki
  JAEA, Ibaraki-ken

• Y. Iwashita
  
• H. Fujisawa, M. Ichikawa, Y. Tajima
  Kyoto ICR, Uji, Kyoto

• L. Shen
  
• Y. L. Chi, Q. M. Dai, X. W. Yang
  IHEP Beijing, Beijing

• S. An
  
• Y.-S. Cho, B. H. Choi, C. Gao
  KAERI, Daejon

A new type of coaxial higher-order mode (HOM) coupler with one hook and two stubs has been designed for PEFP SRF cavities to satisfy the HOM damping requirements of the superconducting RF (SRF) linac of the Proton Engineering Frontier Project (PEFP), and to overcome the notch frequency shift and feed-through tip melting issues. This paper has presents details on the PEFP HOM coupler?s structure, structure optimization, filter characteristics, electro-magnetic field distribution and a coupler installation tool.

• S. An
  
• Y.-S. Cho, B. H. Choi, C. Gao
  KAERI, Daejon

An elliptical superconducting RF cavity of 700 MHz with βg=0.42 has been designed for the Linac of Proton Engineering Frontier Project (PEFP). A double-ring stiffening structure is used for a low-beta cavity for a Lorentz force detuning. The results of the electron multipacting analysis of the cavity are presented. A HOM analysis shows that the HOM coupler's Qext is lower than 3·10⁺⁵, thus reducing the influence of dangerous modes on the beam instabilities and the HOM-induced power.

• I. S. Park
  
• J. Choi, C. W. Chung, M.-S. Hong, W. H. Hwang, D. T. Kim, Y. C. Kim, I. S. Ko, H. C. Kwon, Y. U. Sohn
  PAL, Pohang, Kyungbuk
• S. W. Kim, S. H. Kim, S. K. Song
  RIST, Pohang

Pohang Accelerator Laboratory has studied SRF cavity and set up SRF test laboratory from January 2006. The first activity for SRF research was to develop SRF 3rd harmonic cavity for Pohang Light Source, which was designed, fabricated and tested in 2006. The cryostat are under design. The fabrication of ICHIRO cavity, which is ILC ACD cavity, is PAL's second activity related to SRF. Deep drawing, trimming and welding by electron beam for a 9-cell ICHIRO cavity were done in PAL. The polishing processes for the RF surface including electropolishing were done in KEK under the collaboration between two institutes. This will be tested with real beam in STF-1 of KEK in second half period of 2007. This paper reports the results of fabrication of ICHIRO single- and nine-cell cavities performed in PAL.

• K. R. Kim
  
• Y.-S. Cho, H.-J. Kwon
  KAERI, Daejon
• W. H. Hwang, H. S. Kim, H.-G. Kim, S. J. Kwon, J. Park, J. C. Yoon
  PAL, Pohang, Kyungbuk

The temperature-controlled cooling water system was designed to obtain the resonance frequency stabilization of the normal conducting drift tube linac (DTL) for the PEFP 100 MeV proton accelerator. The primary sizing of individual closed-loop low conductivity cooling water pumping skids for each DTL system was conducted with a simulation of thermo-hydraulic network model. The temperature control schemes incorporating the process dynamic model of heat exchangers were examined to regulate the input water temperatures into the DTL during the steady state operation. The closed water circuits to achieve system performance and stability for low and full duty operation modes were discussed, and numerical results were also presented.

• P. V. Avrakhov
  
• A. Kanareykin
  Euclid TechLabs, LLC, Solon, Ohio
• S. Kazakov
  KEK, Ibaraki
• N. Solyak
  Fermilab, Batavia, Illinois
• V. P. Yakovlev
  Omega-P, Inc., New Haven, Connecticut

• S. Doebert
  
• C. Adolphsen, L. Laurent
  SLAC, Menlo Park, California
• R. Fandos, A. Grudiev, S. T. Heikkinen, J. A. Rodriguez, M. Taborelli, W. Wuensch
  CERN, Geneva

• I. Syratchev
  
• E. Adli, D. Schulte, M. Taborelli
  CERN, Geneva

• E. Wooldridge
  
• C. D. Beard, B. D. Fell, P. A. McIntosh, B. Todd
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• R. M. Jones, B. Spencer
  UMAN, Manchester

• A. C. Dexter
  
• C. D. Beard, P. Goudket, A. Kalinin, L. Ma, P. A. McIntosh
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• G. Burt, R. G. Carter, R. O. Jenkins, M. I. Tahir
  Cockcroft Institute, Lancaster University, Lancaster

The ILC reference design report (RDR) recommends a 14 mrad crossing angle for the positron and electron beams at the IP. A matched pair of crab cavity systems are required in the beam delivery system to align both bunches at the IP. The use of a multi-cell, 3.9GHz dipole mode superconducting cavity, derived from the Fermilab CKM cavity. Dipole-mode cavities phased for crab rotation are shifted by 90 degrees with respect to similar cavities phased for deflection. Uncorrelated phase errors of 0.086 degrees (equivalent to 61fs) for the two cavity systems, gives an average of 180nm for the relative deflection of the bunch centers. For a horizontal bunch size of 655nm, a deflection of 180nm reduces the ILC luminosity by 2%. The crab cavity systems are to be placed ~28m apart and their synchronization to within 61fs is on the limit of what is presently achievable. This paper describes the design and testing of circuits and control algorithms under development at the Cockcroft Institute in the UK for proof of principle experiments planned on the ERLP at Daresbury and on the ILCTA test beamline at FNAL. Simulation results for measurement and control systems are also given.

• I. R.R. Shinton
  
• R. M. Jones
  Cockcroft Institute, Warrington, Cheshire

• J. Norem
  
• A. Bross, A. Moretti, Z. Qian
  Fermilab, Batavia, Illinois
• D. Huang, Y. Torun
  IIT, Chicago, Illinois
• D. Li, M. S. Zisman
  LBNL, Berkeley, California
• R. A. Rimmer
  Jefferson Lab, Newport News, Virginia

The MuCool Experiment has been continuing to take data with 805 and 201 MHz cavities in the MuCool Test Area. The system uses rf power sources from the Fermilab Linac. Although the experimental program is primarily aimed at the Muon Ionization Cooling Experiment (MICE), we have been studying the dependence of rf limits on frequency, cavity material, high magnetic fields, gas pressure, coatings, etc. with the general aim of understanding the basic mechanisms involved. The 201 MHz cavity, essentially a prototype for the MICE experiment, was made using cleaning techniques similar to those employed for superconducting cavities and operates at its design field with very little conditioning.

• P. N. Ostroumov
  
• V. N. Aseev, A. Barcikowski, E. Clifft, R. C. Pardo, M. Sengupta, S. I. Sharamentov
  ANL, Argonne, Illinois

The Argonne Tandem Linear Accelerator System (ATLAS) is the first superconducting heavy-ion linac in the world. Currently ATLAS is being upgraded with the Californium Rare Ion Breeder Upgrade (CARIBU). The latter is a funded project to expand the range of short-lived, neutron-rich rare isotope beams available for nuclear physics research at ATLAS. To avoid beam losses associated with the existing gridded multi-harmonic buncher, we have developed and built a grid-less four-harmonic buncher with fundamental frequency of 12.125 MHz. In this paper, we are going to report the ATLAS beam performance with the new buncher.

• J. Branlard
  
• G. I. Cancelo, R. H. Carcagno, B. Chase, H. Edwards, R. P. Fliller, B. M. Hanna, E. R. Harms, A. Hocker, T. W. Koeth, M. J. Kucera, A. Makulski, U. Mavric, M. McGee, A. H. Paytyan, Y. M. Pischalnikov, P. S. Prieto, R. Rechenmacher, J. Reid, K. R. Treptow, N. G. Wilcer, T. J. Zmuda
  Fermilab, Batavia, Illinois

As part of the research and development towards the International Linear Collider (ILC), several test facilities have been developed at Fermilab. This paper presents the latest LLRF results obtained with Capture Cavity II at these test facilities. The main focus will be on controls and RF operations using the SIMCON based LLRF system. Details about hardware upgrades and overall system performance will be also explained. Finally, design considerations and objectives for the future test facility at the New Muon Laboratory (NML) will be presented.

• I. G. Gonin
  
• J. F. DeFord, B. Held
  STAR, Inc., Mequon, Wisconsin
• N. Solyak
  Fermilab, Batavia, Illinois

• G. Lanfranco
  
• G. Apollinari, I. G. Gonin, T. N. Khabiboulline, G. Romanov, R. L. Wagner
  Fermilab, Batavia, Illinois
• A. Bosotti
  INFN/LASA, Segrate (MI)

The High Intensity Neutrino Source (HINS) project represents the current effort at Fermi National Accelerator Laboratory to produce an 8-GeV proton linac based on about 400 independently phased superconducting resonators. Eighteen β=0.21 single spoke resonators, operating at 325 MHz, comprise the first stage of the linac cold section. We are presenting the production status of the first two of these resonators and the performance of the tuning mechanism prototype. In particular, we will report on the construction phases, the pre-weld tuning process and the comparison of low power RF measurements with calculations made using Microwave Studio*.

* CST MICROWAVE STUDIO (CST MWS), http://www.cst.com/

• U. Mavric
  
• J. Branlard, B. Chase, E. Cullerton, D. W. Klepec
  Fermilab, Batavia, Illinois

• M. McGee
  
• R. Doremus, R. Wands
  Fermilab, Batavia, Illinois

Operated by Universities Research Association, Inc., under Contract No. DE-AC02-76CH03000 with the U. S. Department of Energy#mcgee@fnal.gov

• L. Ristori
  
• G. Apollinari, I. G. Gonin, T. N. Khabiboulline, G. Romanov
  Fermilab, Batavia, Illinois

The proposed High Intensity Neutrino Source at Fermilab is based on an 8 GeV linear proton accelerator which consists of a normal-conducting and a superconducting section. The normal-conducting (warm) section is composed of an ion source, a radio frequency quadrupole, a medium energy beam transport and 16 normal-conducting crossbar H-type cavities that accelerate the beam from 2.5 MeV to 10 MeV (from β=0.0744 to β=0.1422). These warm cavities are separated by superconducting solenoids enclosed in individual cryostats. Beyond 10 MeV, the design uses superconducting spoke resonators to accelerate the beam up to 8 GeV. In this paper, we illustrate the completion of the first normal-conducting crossbar h-type cavity (β=0.0744) explaining in detail the mechanical engineering aspects related to the machining and brazing processes. The radio-frequency measurements and tuning performed at Fermilab on the resonator and the comparisons with the former simulations are also discussed.

• L. R. Doolittle
  
• J. M. Byrd, A. Ratti, J. W. Staples, R. B. Wilcox
  LBNL, Berkeley, California
• G. D'Auria, M. Ferianis, M. M. Milloch, A. Rohlev
  ELETTRA, Basovizza, Trieste
• M. W. Stettler
  CERN, Geneva

• P. M. McIntyre, P. M. McIntyre, N. Pogue, R. Romero, A. Sattarov
  Texas A&M University, College Station, Texas

A polyhedral superconducting cavity is being developed for possible use in linac colliders. In side view it has the contour of a Tesla-type multi-cell string. The surfaces of the cavity are formed by bonding flat foils to solid copper wedge-shaped segments, so that the end view is a polyhedron of such segments. Several features of this structure make it interesting for linac colliders: the cavity segments are totally open for cleaning, polishing, and inspection until the final assembly step; narrow slot gaps at the boundaries between segments strongly suppress all deflecting modes without penalty to the accelerating mode; the solid copper substrate accommodates cooling channels and eliminates the need for an immersion cryostat; and the open geometry makes it possible to utilize advanced superconductors (e.g. multi-layer Nb/Nb3Sn, YBCO, MgB2) on the cavity surface, opening the possibility of higher gradients.

• J. Popielarski
  
• T. L. Grimm, W. Hartung, R. C. York
  NSCL, East Lansing, Michigan

The Spallation Neutron Source (Oak Ridge), the proposed 8 GeV Proton Driver (Fermilab), and the proposed Rare Isotope Accelerator use multicell elliptical SRF cavities to provide much of the accelerating voltage. This makes the elliptical cavity segment the most expensive part of the linac. A new type of accelerating structure called a half-reentrant elliptical cavity can potentially improve upon existing elliptical designs by reducing the cryogenic load by as much as 30% for the same accelerating voltage. Alternatively, with the same peak surface magnetic field as traditional elliptical cavities, it is anticipated that half-reentrant designs could operate at up to 25% higher accelerating gradient. With a half-reentrant shape, liquids can drain easily during chemical etching and high pressure rinsing, which allows standard multicell processing techniques to be used. A half-reentrant cavity for β = v/c = 1, suitable for the proposed ILC, has been designed and fabricated, with RF tests in progress*. In this paper, we present electromagnetic designs for three half-reentrant cell shapes suitable for an ion or proton linac (β = 0.47, 0.61 and 0.81, f = 805 or 1300 MHz).

* M. Meidlinger et al., in Proc. XXIII Int. Linac Conf., Knoxville, TN, Aug 2006

• V. Veshcherevich
  
• S. A. Belomestnykh, P. Quigley, J. J. Reilly, J. Sears
  CLASSE, Ithaca
• W.-D. Moller
  DESY, Hamburg

First RF power couplers for the ERL injector, currently under construction at Cornell University, have been fabricated. The couplers were assembled in pairs in the liquid nitrogen cryostat, built for their tests. A 15 kW CW IOT transmitter was available for coupler tests. A resonant ring was used for additional increase of the power. The couplers were successfully tested up to the goal power level of 50 kW CW. However, the first pair of couplers showed excessive temperature rise in some points. Therefore, minor changes in the design have been done to improve cooling.

• W. J. DeHope
  
• K. L. Griffin, R. Kihara, M. M. Ong, O. Ross
  LLNL, Livermore, California

The now-mature FXR (Flash X-Ray) radiographic facility at Lawrence Livermore National Laboratory will be briefly described with emphasis on its pulsed power system. The heart of each accelerating cell's pulse-forming Blumlein is it's sulfur hexafluoride-based triggered closing switch. FXR's recent upgrade to a recirculating SF6 gas reclamation system will be described and the resulting accelerator performance and reliability improvements documented. This was accompanied by a detailed switch breakdown study on FXR's Test Stand* and the recent analysis of the resulting statistics will be shown.

* W. DeHope, D. Goerz, R. Kihara, M. Ong, G. Vogtlin, J. Zentler, "An Induction Linac Test Stand", 21st Particle Accelerator Conference, Knoxville, TN, May 20, 2005

• S. Kwon
  
• J. Davis, M. T. Lynch, M. S. Prokop, S. Ruggles, P. A. Torrez
  LANL, Los Alamos, New Mexico

• J. T.M. Lyles
  
• S. Archuletta, D. Baca, J. Davis, D. Rees, P. A. Torrez
  LANL, Los Alamos, New Mexico

A new 200 MHz RF system is being developed for the LANSCE proton drift tube linac (DTL). A planned upgrade will replace parts of the DTL RF system with new generation components. When installed for the LANSCE-R project, the new system will reduce the total number of electron power tubes from twenty-four to seven in the DTL plant. The 3.4 MW final power amplifier will use a Thales TH628 Diacrode. This state-of-the-art device eliminates the large anode modulator of the present triode system, and will be driven by a new tetrode intermediate power amplifier. In this mode of operation, this intermediate stage will provide 150 kW of peak power. The first DTL tank requires up to 400 kW of RF power, which will be provided by the same tetrode driver amplifier. A prototype system is being constructed to test components, using some of the infrastructure from previous RF projects. High voltage DC power became available through innovative re-engineering of an installed system. A summary of the design and construction of the intermediate power amplifier will be presented and test results will be summarized.

• W. Reass
  
• V. P. Derenchuk, T. Rinckel, G. Visser
  IUCF, Bloomington, Indiana
• D. Rees
  LANL, Los Alamos, New Mexico

This paper describes the Klystron RF systems for the Indiana University Low Energy Neutron Source (LENS) accelerator 425 MHz Radio Frequency Quadrupole (RFQ) and Drift Tube Linac (DTL) systems. Of interest in the power conditioning system is the design of the totem-pole grid-catch modulator for the mod-anode klystrons. This topology provides a fast rise and fall and closed loop regulation for the klystron mod-anode to cathode voltage, which minimizes RF amplitude and phase droop while maximizing efficiency. Another advantage is that short pulse high rep-rate operation is viable within the average power capabilities of the klystron. The 425 MHz, 1.25 MW klystron amplifier chain will also be detailed. Of final interest, is the digital low level RF system. This provides vector control of the cavity field using direct conversion, non-I/Q sampling architecture, at a sampling rate of 132 MHz with a 12-bit ADC. Four input and two output channels are integrated into a 6U VME module, with all DSP functions performed in Xilinx Spartan-3 field-programmable gate arrays. The design and implementation of these systems, coupled with LENS operational results, will be presented.

• D. Rees
  
• G. O. Bolme, J. T. Bradley III, S. Kwon, J. T.M. Lyles, M. T. Lynch, M. S. Prokop, W. Reass, K. A. Young
  LANL, Los Alamos, New Mexico

• K. A. Young
  
• G. O. Bolme, J. T.M. Lyles, M. T. Lynch, E. P. Partridge, D. Rees
  LANL, Los Alamos, New Mexico

The LANSCE RF system consists of four RF stations at 201 MHz and 44 klystrons at 805 MHz. In the LANSCE accelerator, the beam source is injected into the RF system at 0.75 MeV. The beam is then accelerated to 100 MeV in four drift tube linac (DTL) tanks, driven at 201.25 MHz. Each 201 MHz RF system consists of a train of amplifiers, including a solid state amplifier, a tetrode, and then at triode. After the DTL, the beam is accelerated from 100 MeV to 800 MeV in the forty-four coupled cavity linac (CCL) tanks at 805 MHz. The machine operates with a normal RF pulse width of 835 microseconds at a repetition rate up to 120 Hz, and sometimes operates with a pulse width up to 1.2 microseconds for single pulses. This RF system has been operating for about 37 years. This paper summarizes the recent operational experience. The reliability of the 805 MHz and 201 MHz RF systems is discussed, and a summary the lifetime data of the 805 MHz klystrons and 201 MHz triodes is presented.

• A. M. Cook
  
• M. P. Dunning, J. B. Rosenzweig, K. M. Serratto
  UCLA, Los Angeles, California
• P. Frigola
  RadiaBeam, Los Angeles, California

The pi-mode resonant frequency of the 1.6 cell SLAC/BNL/UCLA style RF photoinjector electron gun is conventionally tuned using cylindrical copper tuning pieces that extend into the full-cell cavity through holes in the side of the gun. This design begins to fail in many versions of this popular gun design at higher voltage levels, when the cavity undergoes electric breakdown in the vicinity of the tuners. In order to remove the tuners from the region of high electric field, mitigating this problem, the full cell geometry must be changed significantly. We report on a method of accomplishing this, in which we use a mechanical device of custom design to stretch the cavity structure of an existing photoinjector in order to tune the resonant frequency up by over 2 MHz. We present results of testing the modified photoinjector in an RF test bed with both copper and magnesium cathodes, succeeding in putting approximately 8 - 10 MW of RF power into the gun. This is an improvement over the 4 MW routinely achieved in a similar gun using conventional tuning methods installed at the UCLA Neptune laboratory.

• R. Akre
  
• J. M. Byrd
  LBNL, Berkeley, California
• D. Dowell, P. Emma, J. C. Frisch, B. Hong, K. D. Kotturi, P. Krejcik, J. Wu
  SLAC, Menlo Park, California

The Linac Coherent Light Source at SLAC will be the brightest X-ray laser in the world when it comes on line. In order to achieve the brightness a 100fS length electron bunch is passed through an undulator. To creat the 100fS bunch, a 10pS electron bunch, created from a photo cathode in an RF gun, is run off crest on the RF to set up a position to energy correlation. The bunch is then compressed chicanes. The stability of the RF system is critical in setting up the position to energy correlation. Specifications derived from simulations require the RF system to be stable to below 100fS in several critical injector stations and the last kilometer of linac. The SLAC linac RF system is being upgraded to meet these requirements.

• K. L.F. Bane
  
• C. Adolphsen, C. D. Nantista
  SLAC, Menlo Park, California

The nominal design gradient for the ILC is 31.5 MV/m, but the L-band superconducting cavities built to date have demonstrated a range in sustainable gradient extending below this goal, limited by Q-dropoff and quenching. An economically feasible cavity acceptance rate will include in the linacs a certain percentage of sub-performing cavities. We examine how, with a customizable RF distribution scheme, one can most efficiently distribute power from one klystron amongst 24 nine-cell cavities. The nominal cavity fills to the design gradient at the time the beam arrives, after which the beamloading voltage exactly cancels any further rise, yielding constant gradient during the bunch train. Along with adjustable RF power, we assume adjustable cavity coupling, or loaded quality factor, so that the gradient can be leveled in non-nominal cavities, to avoid quench-inducing overshoots. We explore these and related issues for the ILC linac high-power RF.

• L. Ge
  
• C. Adolphsen, K. Ko, L. Lee, Z. Li, C.-K. Ng, G. L. Schussman, F. Wang
  SLAC, Menlo Park, California
• B. Rusnak
  LLNL, Livermore, California

The TTF-III coupler adopted for the ILC baseline cavity design has shown a tendency to have long initial high power processing times. A possible cause for the long processing times is believed to be multipacting in various regions of the coupler. To understand performance limitations during high power processing, SLAC has built a flexible high-power coupler test stand. The plan is to test individual sections of the coupler, which includes the cold and warm coaxes, the cold and warm bellows, and the cold window, using the test stand to identify problematic regions. To provide insights for the high power test, detailed numerical simulations of multipacting for these sections will be performed using the 3D multipacting code Track3P. The simulation results will be compared with measurement data.

• C. D. Nantista
  
• C. Adolphsen, G. B. Bowden, B. D. McKee, R. Swent
  SLAC, Menlo Park, California

An ILC R&D facility is being constructed in the NML building at Fermilab which, in addition to an injector and beam dump with spectrometer, will contain up to three cryomodules worth of ILC-type superconducting 9-cell cavities, 24 in all. This linac will be powered by a single klystron. As part of SLAC?s contribution to this project, we will provide a distribution network in WR650 waveguide to the various cavity couplers. In addition to commercial waveguide components and circulators and loads developed for TESLA, this sytem will include adjustable tap-offs, and customized hybrids. In one configuration, the circulators will be removed to test pair-wise cancellation of cavity reflections through hybrids. The system will be pressurized with nitrogen to 3 bar absolute to avoid the need for SF6 at windows or circulator. The full distribution for the first cryomodule will be delivered and installed later this year. We describe the design of the system and completed RF testing.

• G. C. Pappas
  
• G. D'Auria, P. Delgiusto, L. Veljak
  ELETTRA, Basovizza, Trieste

1. "NLC Hybrdi Solid State Induction Modulator" R. L. Cassel, etal, Lubeck, Germany, Linac 2004.

• Q. S. Shu
  
• G. F. Chen, F. H. Lu, I. M. Phipps, J. T. Susta
  AMAC, Newport News, Virginia
• T. N. Khabiboulline, N. Solyak
  Fermilab, Batavia, Illinois

In order to increase the protons energy up to 8 GeV in a driver Linac, the particles must be accelerated through various stages and three different power levels (25kW, 100kW and 210kW) are required for the 325 MHz Fermilab Proton Driver couplers. The problem identified by the project is that no High RF power coupler for these cavities has ever been produced using US industrial capabilities. AMAC proposed a novel resolution by development of innovative modular, multiple power levels, 325 MHz spoke cavities power couplers, which to meet three type cavities with one coupler design. The simulation and concept design are presented. The results of HFSS, MAFIA, ANSYS, and Multipacting are also discussed.

• M. A. Drury
  
• E. Daly, G. K. Davis, J. F. Fischer, C. Grenoble, W. R. Hicks, J. Hogan, K. King, R. Nichols, T. E. Plawski, J. P. Preble, T. M. Rothgeb, H. Wang
  Jefferson Lab, Newport News, Virginia

The Thomas Jefferson National Accelerator Facility has begun a cryomodule refurbishment project. The goal of this project is robust 6 GeV, 5 pass operation of the Continuous Electron Beam Accelerator Facility (CEBAF). The scope of the project includes removing, refurbishing and replacing 10 CEBAF cryomodules at a rate of three per year. Refurbishment includes reprocessing of SRF cavities to eliminate field emission and increase the nominal gradient from the original 5 MV/m to 12.5 MV/m. New "dogleg" couplers between the cavity and helium vessel flanges will intercept secondary electrons that produce arcing on the 2 K ceramic window in the Fundamental Power Coupler (FPC). Modification of the Qext of the FPC will allow higher gradient operations. Other changes include new ceramic RF windows for the air to vacuum interface of the FPC and improvements to the mechanical tuners. Any damaged or worn components will be replaced as well. Currently, the first of the refurbished cryomodules has been installed and tested both in the Cryomodule Test Facility and in place in the North Linac of CEBAF. This paper will summarize the results of these tests.

• C. Hovater
  
• T. L. Allison, J. R. Delayen, J. Musson, T. E. Plawski
  Jefferson Lab, Newport News, Virginia

We have developed a digital process that emulates an analog oscillator and ultimately a self excited loop (SEL) for field control. The SEL, in its analog form, has been used for many years for accelerating cavity field control. In essence the SEL uses the cavity as a resonant circuit – much like a resonant ?tank? circuit is used to build an oscillator. An oscillating resonant circuit can be forced to oscillate at different, but close, frequencies to resonance by applying a phase shift in the feedback path. This allows the circuit to be phased locked to a master reference, which is crucial for multiple cavity accelerators. For phase and amplitude control the SEL must be forced to the master reference frequency, and feedback provided for in both dimensions. The novelty of this design is in the way digital signal processing (DSP) is structured to emulate an analog system. While the digital signal processing elements are not new, to our knowledge this is the first time that the digital SEL concept has been designed and demonstrated. This paper reports on the progress of the design and implementation of the digital SEL for field control of superconducting accelerating cavities.

• T. E. Plawski
  
• T. L. Allison, G. K. Davis, H. Dong, C. Hovater, K. King, J. Musson
  Jefferson Lab, Newport News, Virginia

The new digital LLRF system for the CEBAF 12GeV accelerator will perform a variety of tasks, beyond field control.* In this paper we present the superconducting cavity resonance control system designed to minimize RF power during gradient ramp and to minimize RF power during steady state operation. Based on the calculated detuning angle, which represents the difference between reference and cavity resonance frequency, the cavity length will be adjusted with a mechanical tuner. The tuner has two mechanical driving devices, a stepper motor and a piezo-tuner, to yield a combination of coarse and fine control. Although LLRF piezo processing speed can achieve 10 kHz bandwidth, only 10 Hz speed is needed for 12 GeV upgrade. There will be a number of additional functions within the LLRF system; heater controls to maintain cryomodule's heat load balance, ceramic window temperature monitoring, waveguide vacuum interlocks, ARC detector interlock and quench detection. The additional functions will be divided between the digital board, incorporating an Altera FPGA and an embedded EPICS IOC. This paper will also address hardware evolution and test results performed with different SC cavities.

*RF Control Requirements for the CEBAF Energy Upgrade Cavities, C. Hovater, J. Delayen, L. Merminga, T. Powers, C. Reece, Proceedings 2000 Linear Accelerator Conference, Monterey, CA , August 2000

• R. A. Rimmer
  
• R. Bundy, G. Cheng, G. Ciovati, E. Daly, R. Getz, J. Henry, W. R. Hicks, P. Kneisel, S. Manning, R. Manus, K. Smith, M. Stirbet, L. Turlington, L. Vogel, H. Wang, K. Wilson
  Jefferson Lab, Newport News, Virginia
• F. Marhauser
  JLAB, Newport News, Virginia

We describe the developments underway at JLab to develop new CW cryomodules capable of transporting up to Ampere-levels of beam currents for use in ERLs and FELs. Goals include an efficient cell shape, high packing factor for efficient real-estate gradient and very strong HOM damping to push BBU thresholds up by two or more orders of magnitude compared to existing designs. Cavity shape, HOM damping and ancillary components are optimized for this application. Designs are being developed for low-frequency (750 MHz), Ampere-class compact FELs and for high-frequency (1.5 GHz), 100 mA configurations. These designs and concepts can easily be scaled to other frequencies. We present the results of conceptual design studies, simulations and prototype measurements. These modules are being developed for the next generation ERL based high power FELs but may be useful for other applications such as high energy light sources, electron cooling, electron-ion colliders, industrial processing etc.

• I. E. Campisi
  
• S. Assadi, F. Casagrande, M. S. Champion, M. T. Crofford, G. W. Dodson, J. Galambos, M. Giannella, S. Henderson, M. P. Howell, Y. W. Kang, K.-U. Kasemir, S.-H. Kim, Z. Kursun, P. Ladd, H. Ma, D. Stout, W. H. Strong, Y. Zhang
  ORNL, Oak Ridge, Tennessee

The Superconducting Linac at SNS has been operating with beam for almost two years. As the first operational pulsed superconducting linac, many of the aspect of its performance were unknown and unpredictable. A lot of experience has been gathered during the commissioning of its components, during the beam turn on and during operation at increasingly higher beam power. Some cryomodules have been cold for well over two years and have been extensively tested. The operation has been consistently conducted at 4.4 K and 10 and 15 pulses per second, with some cryomodules tested at 30 and 60 pps and some tests performed at 2 K. Careful balance between safe operational limits and the study of conditions, parameters and components that create physical limits has been achieved. This paper presents the experience and the performance of the superconducting cavities and of the associated systems with and without beam.

• Y. W. Kang
  
• A. V. Aleksandrov, D. E. Anderson, M. S. Champion, M. T. Crofford, P. E. Gibson, T. W. Hardek, P. Ladd, M. P. McCarthy, D. Stout, A. V. Vassioutchenko
  ORNL, Oak Ridge, Tennessee

A RF power coupling system has been developed for future upgrade of input coupling of the RFQ in the SNS linac. The design employs two coaxial loop couplers for 402.5 MHz operation. Each loop is fed through a coaxial ceramic window that is connected to an output of a magic-T waveguide hybrid through a coaxial to waveguide transition. The coaxial loop couplers are designed, manufactured, and high power processed. Two couplers will be used in parallel to power the accelerating structure with up to total 800 kW peak power at 8% duty cycle. RF and mechanical properties of the couplers are discussed. Result of high power RF conditioning that is performed in the RF test facility of the SNS is presented.

• Y. W. Kang
  
• M. S. Champion, T. W. Hardek, S.-H. Kim, M. P. McCarthy, A. V. Vassioutchenko, J. L. Wilson
  ORNL, Oak Ridge, Tennessee

High power vector modulators can allow a fan-out RF power distribution system that can power many accelerating cavities from a single high-power klystron amplifier. The configuration enables independent control of amplitudes and phases of RF voltages at the cavities. A vector modulator employs either one or two hybrids with two fast phase shifters. Prototype high power RF vector modulators employing a hybrid and two fast ferrite phase shifters in coaxial TEM transmission lines for 402.5 MHz and 805 MHz are built and tested. RF properties of the design and result of high power testing are presented.

• S.-H. Kim
  
• I. E. Campisi, F. Casagrande, M. T. Crofford, Y. W. Kang, Z. Kursun, D. Stout, A. V. Vassioutchenko
  ORNL, Oak Ridge, Tennessee

The cryomodule tests are on going to have better understandings of physics as a whole and eventually to provide safe and reliable operation for neutron production. Some features are revealed to be interesting issues and need more attentions than expected, such as operating condition, collective effects between cavities, HOM coupler issues, end-group stability, cavity-coupler interactions, and vacuum/gas physics, waiting for more investigations. Up to now SNS cryomodules were mainly tested at 4.4 K, 10 pulse per second (pps) and 30 pps/60 pps tests are under progress. This paper presents the experiences and the observations during tests of cryomodules.

• Y. Zhang
  
• I. E. Campisi, C. Deibele, J. Galambos, S. Henderson, Y. W. Kang, H. Ma, J. L. Wilson
  ORNL, Oak Ridge, Tennessee

Beam phase measurement based on detection of transient beam loading signal in a Superconducting (SC) cavity is utilized to setup the cavity synchronous phase. It has the potential to become a fast tune-up technique for a high intensity SC electron linac, as cavity phase could be determined precisely with only a few beam pulses. The paper introduces a transient detector study in the Spallation Neutron Source (SNS) proton linac, and discusses one of the major challenges - stochastic noise in the cavity RF system, which deteriorates the precision and increases the time needed for phase measurement with this technique. We analyze the influence of RF noise to the phase measurement in a simulation study with a beam-cavity model. Beam signal measurement with the cavity Low Level RF (LLRF) system and the initial experiment of prototype detectors are briefly introduced.

• J. Haimson
  
• B. A. Ishii, B. L. Mecklenburg, G. A. Stowell
  HRC, Santa Clara, California

The gain of a high power TW relativistic klystron can be increased substantially with the use of a varying phase velocity, large beam aperture, lengthened output structure, designed for asynchronous interaction to control space charge fields and provide near-adiabatic bunch compression during the power extraction process. While this technique enables the replacement of a pulsed vacuum tube driver system with a small, inexpensive solid state RF source, lengthening the output circuit increases the number (and reduces the separation) of the longitudinal mode resonances in the TM01 operating band. Thus, the probability of exciting parasitic oscillations is increased, especially when the klystron is operated into a mismatched load or a high Q structure. The prevention of such oscillations, even when in close proximity to the operating frequency, using a technique that is unaffected by the phase or amplitude of reflected signals is described; and test results are presented of a solid state driven, 76dB gain 17GHz TW relativistic klystron, recently installed in the linac test facility at the MIT Plasma Science and Fusion Center.

• J. Haimson
  
• B. L. Mecklenburg
  HRC, Santa Clara, California

To avoid surface erosion damage and to assist in understanding RF breakdown limitations imposed on high gradient linac operation, a gradient hardened structure is being fabricated having high temperature brazed and machined stainless steel surfaces located in the high E-field region of the beam apertures and in the high H-field regions of the racetrack shaped coupling cavities. The microwave design parameters and physical dimensions of this 17GHz, 2pi/3 mode, 22-cavity structure were established specifically to allow comparison of its high gradient performance to that of a similar all-copper structure tested under identical conditions, using an existing 4X power amplifying, RF recirculating dual ring system. Use of the 6X thicker skin depth material, the resulting de-Q-ing effects and the minimal reduction of beam energy (2%) associated with the strategically located lossy surfaces are discussed; fabrication techniques are described; and design parameters of the gradient hardened linac and the 17GHz power amplifying system are presented.

• A. Burrill
  
• I. Ben-Zvi, R. Calaga, H. Hahn, V. Litvinenko, G. T. McIntyre
  BNL, Upton, Long Island, New York
• P. Kneisel, J. Mammosser, J. P. Preble, C. E. Reece, R. A. Rimmer, J. Saunders
  Jefferson Lab, Newport News, Virginia

One of the key components for the Energy Recovery Linac being built by the Electron cooling group in the Collider Accelerator Department is the 5 cell accelerating cavity which is designed to accelerate 2 MeV electrons from the gun up to 15-20 MeV, allow them to make one pass through the ring and then decelerate them back down to 2 MeV prior to sending them to the dump. This cavity was designed by BNL and fabricated by AES in Medford, NY. Following fabrication it was sent to Thomas Jefferson Lab in VA for chemical processing, testing and assembly into a string assembly suitable for shipment back to BNL and integration into the ERL. The steps involved in this processing sequence will be reviewed and the deviations from processing of similar SRF cavities will be discussed. The lessons learned from this process are documented to help future projects where the scope is different from that normally encountered.

• X. Chang
  
• I. Ben-Zvi, J. Kewisch, C. Pai
  BNL, Upton, Long Island, New York

• W. Zhang
  
• W. Eng, C. Pai, J. Sandberg, Y. Tan, Y. Tian
  BNL, Upton, Long Island, New York

We have recently developed a simplified model and a set of simple formulas for inductive voltage adder design. This model reveals the relationship of output waveform parameters and hardware designs. A computer simulation has demonstrated that parameter estimation based on this approach is accurate as compared to an actual circuit. This approach can be used in early stages of project development to assist feasibility study, geometry selection in engineering design, and parameter selection of critical components. In this paper, we give the deduction of a simplified model. Among the estimation formulas we present are those for pulse rise time, system impedance, and number of stages. Examples are used to illustrate the advantage of this approach. This approach is also applicable to induction LINAC design.

• R. Ferdinand
  

• M. Liepe
  
• S. A. Belomestnykh, E. P. Chojnacki, V. Medjidzade, H. Padamsee, P. Quigley, J. Sears, V. D. Shemelin, V. Veshcherevich
  CLASSE, Ithaca

Cornell University is developing and fabricating a SRF injector cryomodule for the acceleration of the high current (100 mA) beam in the Cornell ERL prototype and ERL light source. Major challenges include emittance preservation of the low energy, ultra low emittance beam, cw cavity operation, and strong HOM damping with efficient HOM power extraction. Prototypes have been completed for the 2-cell niobium cavity with helium vessel, coaxial blade tuner with piezo fine tuners, twin high power input couplers, and beam line HOM absorbers loaded with ferrites and ceramics. Axial symmetry of HOM absorbers, together with two symmetrically placed input couplers per cavity, avoids transverse on-axis fields, which would cause emittance growth. A one-cavity cryostat has been designed following concepts of the TTF cryostat, and is presently under fabrication and assembly. The cryostat design has been optimized for precise cavity alignment, good magnetic shielding, and high dynamic cryogenic loads from the RF cavities, input couplers, and HOM loads. In this paper we report on the status of the assembly and first test of the one-cavity test cryostat.

• Y. Morozumi
  
• F. Furuta, T. Higo, T. Saeki, K. Saito
  KEK, Ibaraki

• P. Bosland
  
• P.-E. Bernaudin, G. Devanz, A. Perolat, C. G. Thomas-Madec
  CEA, Gif-sur-Yvette
• S. Blivet, T. Junquera, D. Longuevergne, F. Lutton, G. Martinet, G. Olry, H. Saugnac
  IPN, Orsay
• R. Ferdinand
  GANIL, Caen
• M. Fruneau, Y. Gomez-Martinez, F. Vezzu
  LPSC, Grenoble

• V. V. Danilov
  
• A. V. Aleksandrov, S. Assadi, W. Blokland, S. M. Cousineau, C. Deibele, W. P. Grice, S. Henderson, J. A. Holmes, Y. Liu, M. A. Plum, A. P. Shishlo, A. Webster
  ORNL, Oak Ridge, Tennessee
• I. Nesterenko
  BINP SB RAS, Novosibirsk
• L. Waxer
  LJW, Saint Louis

Thin carbon foils are used as strippers for charge exchange injection into high intensity proton rings. However, the stripping foils become radioactive and produce uncontrolled beam loss, which is one of the main factors limiting beam power in high intensity proton rings. Recently, we presented a scheme for laser stripping an H^- beam for the Spallation Neutron Source ring. First, H^- atoms are converted to H0 by a magnetic field, then H0 atoms are excited from the ground state to the upper levels by a laser, and the excited states are converted to protons by a magnetic field. In this paper we report on the first successful proof-of-principle demonstration of this scheme to give high efficiency (around 90%) conversion of H^- beam into protons at SNS in Oak Ridge. The experimental setup is described, and comparison of the experimental data with simulations is presented. In addition, future plans on building a practical laser stripping device are discussed.

• R. E. Laxdal
  

• M. A. Plum
  

The Spallation Neutron Source accelerator complex consists of a 2.5 MeV H^- front-end injector system, a 186 MeV normal-conducting linear accelerator, a 1 GeV superconducting linear accelerator, an accumulator ring, and associated beam transport lines. The linac was commissioned in five discrete runs, starting in 2002 and completed in 2005. The accumulator ring and associated beam transport lines were commissioned in two runs in February and April 2006. With the completed commissioning of the SNS accelerator, the facility has begun initial low-power operations. In the course of beam commissioning, most beam performance parameters and beam intensity goals have been achieved at low duty factor. A number of beam dynamics measurements have been performed, including emittance evolution, transverse coupling in the ring, beam instability thresholds, and beam distributions on the target. The commissioning results, achieved beam performance and initial operating experience of the SNS will be presented.

• A. Feschenko
  
• A. V. Aleksandrov, S. Assadi, J. Galambos, S. Henderson
  ORNL, Oak Ridge, Tennessee
• L. V. Kravchuk, A. A. Menshov
  RAS/INR, Moscow

SNS Linac utilizes several accelerating structures operating at two frequencies. CCL and SCL operate at 805 MHz while 402.5 MHz is used for RFQ and DTL. Beam transfer from the previous part of the accelerator to the subsequent one requires careful longitudinal matching to improve beam transmission and to minimize beam losses. Longitudinal beam parameters have been investigated with the help of three Bunch Shape Monitors installed in the intersegments of the first CCL Module. The results of bunch shape observations for different accelerator settings are presented. Longitudinal beam emittance has been measured and optimized. Longitudinal beam halo has been evaluated as well.

• S. Machida
  

Accelerator of muon has to have very large acceptance and very quick acceleration. Recent study shows that FFAGs (in particular non-scaling) are one of the most promising candidates for muon accelerators as building block for a neutrino factory. There are, however, some unresolved problems which should be studied in more detail. We will talk about mostly beam dynamics issues of the muon accelerators, not only FFAG, but other candidates such as linac and RLA and compare their performance.

• K. Hasegawa
  

• P. Krejcik
  

• S. Molloy
  
• N. Baboi, O. Hensler, R. Paparella, L. M. Petrosyan
  DESY, Hamburg
• N. E. Eddy, L. Piccoli, R. Rechenmacher, M. Wendt
  Fermilab, Batavia, Illinois
• J. C. Frisch, J. May, D. J. McCormick, M. C. Ross, T. J. Smith
  SLAC, Menlo Park, California
• O. Napoly, C. Simon
  CEA, Gif-sur-Yvette

It is well known that an electron beam excites Higher Order Modes (HOMs) as it passes through an accelerating cavity~[panofsky68]. The properties of the excited signal depend not only on the cavity geometry, but on the charge and trajectory of the beam. It is, therefore, possible to use these signals as a monitor of the beam's position. Electronics were installed on all forty cavities present in the FLASH~[flashref] linac in DESY. These electronics filter out a mode known to have a strong dependence on the beam's position, and mix this down to a frequency suitable for digitisation. An analysis technique based on Singular Value Decomposition (SVD) was developed to calculate the beam's trajectory from the output of the electronics. The entire system has been integrated into the FLASH control system.

• M. A. Holloway
  
• S. V. Benson, W. Brock, J. L. Coleman, D. Douglas, R. Evans, P. Evtushenko, K. Jordan, D. W. Sexton
  Jefferson Lab, Newport News, Virginia
• R. B. Fiorito, P. G. O'Shea, A. G. Shkvarunets
  UMD, College Park, Maryland

Optical Transition Radiation Interferometry (OTRI) has proven to be effective tool for measuring rms beam divergence. We present rms emittance measurement results of the 115 MeV energy recovery linac at the Thomas Jefferson National Laboratories Free electron Laser using OTRI. OTRI data from both near field beam images and far field angular distribution images give evidence of two spatial and angular distributions within the beam. Using the unique features of OTRI we segregate the two distributions of the beam and estimate separate rms emittance values for each component.

• T. Semba
  
• Y. Chida, Y. Itou, T. Tagawa, Y. Tsujioka, T. Yoshinari
  Hitachi Ltd., Ibaraki-ken
• N. Shibata
  Hitachi High-Technologies Corp., Ibaraki-ken

• H. Vogel
  

• T. A. Treado
  
• S. J. Einarson
  CPI, Beverley, Massachusetts

• K. Hayashi
  
• M. Irikura, Y. Mitsunaka, Y. Okubo, M. Sakamoto, H. Taoka, K. Tetsuka, H. Urakata
  TETD, Otawara
• M. Y. Miyake, Y. Yano
  Toshiba, Yokohama

• P. Dauguet
  

• M. N. Martins
  
• A. L. Bonini, R. Lima, A. A. Malafronte, T. F. Silva
  USP/LAL, Sao Paulo

The injector linac consists of a beam conforming stage, with chopper and buncher systems, and two acceleration structures, the first one with variable β, and the second one divided into two parts with different β. There are two 3-mm diameter collimators, the first at the entrance to the first chopper cavity and the second at the entrance to the first acceleration structure. The beam focalization is made by solenoids, and correcting coils are provided for steering. In this work we describe the commissioning of the optical lattice of the conforming beam stage. The first beam images are shown.

• M. T. Maier
  
• W. Barth, W. B. Bayer, L. A. Dahl, L. Groening, C. M. Kleffner, B. Schlitt, K. Tinschert, H. Vormann, S. Yaramyshev
  GSI, Darmstadt
• U. Ratzinger, A. Schempp
  IAP, Frankfurt am Main

• U. Emanuele, U. Emanuele, A. Italiano
  INFN - Gruppo Messina, S. Agata, Messina
• L. Auditore, R. C. Barna, D. De Pasquale, D. Loria, A. Trifiro, M. Trimarchi
  Universita di Messina, Messina

• L. Auditore, L. Auditore, R. C. Barna, D. De Pasquale, D. Loria, A. Trifiro, M. Trimarchi
  Universita di Messina, Messina
• U. Emanuele, A. Italiano
  INFN - Gruppo Messina, S. Agata, Messina

• T. Inagaki
  
• H. Baba, H. Matsumoto
  KEK, Ibaraki
• A. Miura
  Nihon Koshuha Co., Ltd., Yokohama
• S. Miura
  MHI, Hiroshima
• T. Shintake, K. Shirasawa
  RIKEN Spring-8 Harima, Hyogo

C-band (5712-MHz) linac is used as the main accelerator of the Japanese X-FEL facility in SPring-8. Since the C-band linac has high acceleration gradient, our 8-GeV accelerator is compact rather than a conventional S-band accelerator. The system consists of following components; two choke-mode-type 1.8-m accelerating structures, an rf pulse compressor (SLED), a 50-MW klystron, a 100-MW compact modulator, and an rf digital control system. We will use 60 to 70 units for the X-FEL accelerator. Since November 2005, we have operated two C-band units in the 250-MeV FEL prototype accelerator (SCSS). After rf conditioning, the accelerating gradient was achieved to 35-MV/m. We successfully accelerated the electron beam by this gradient of electrical field. In this presentation, we will report the detail of each component and its operation status of the SCSS prototype accelerator.

• T. Kamitani
  
• T. Higo, M. Ikeda, K. Kakihara, N. Kudoh, S. Ohsawa, T. Sugimura, T. T. Takatomi, K. Yokoyama
  KEK, Ibaraki

• T. Suwada
  
• R. Chehab
  IN2P3 IPNL, Villeurbanne
• K. Furukawa, T. Kamitani, H. Okuno, M. Satoh, T. Sugimura, K. Umemori
  KEK, Ibaraki
• R. Hamatsu, T. Haruna, T. Sumiyoshi
  TMU, Hatioji-shi, Tokyo
• A. Potylitsyn
  INPR, Tomsk
• I. S. Tropin
  TPU, Tomsk
• K. Yoshida
  SAGA, Tosu

A new tungsten single-crystalline positron target has been successfully employed for generation of the intense positron beam at the KEKB injector linac in September 2006. The target is composed of a tungsten single-crystal with a thickness of 10.5 mm. The positron production target is bombarded at an incident electron energy of 4 GeV, and the produced positrons are collected and accelerated up to the final injection energy of 3.5 GeV in the succeeding sections. A conventional tungsten plate with a thickness of 14 mm has been used previously, and the conversion efficiency (Ne⁺/Ne^-), the ratio between the number of positrons (Ne⁺) captured in the positron capture section and the number of the incident electrons (Ne^-), was 0.20 on average. By replacing the tungsten plate with the tungsten crystal, it increased to 0.25 on average. The increase of the conversion efficiency has boosted the positron intensity to its maximum since the beginning of KEKB operation in 1999. Now this new positron source is stably operating and is contributing to increasing the integrated luminosity of the KEKB B-factory.

• T. Natsui
  
• M. Akemoto, S. Fukuda, T. Higo, N. Kudoh, T. T. Takatomi, M. Yoshida
  KEK, Ibaraki
• K. Dobashi, M. Uesaka, T. Yamamoto
  UTNL, Ibaraki
• F. Sakamoto, A. Sakumi
  The University of Tokyo, Nuclear Professional School, Ibaraki-ken
• E. Tanabe
  AET Japan, Inc., Kawasaki-City

• M. Uesaka
  
• F. Sakamoto, A. Sakumi
  The University of Tokyo, Nuclear Professional School, Ibaraki-ken

• K. Kan
  
• T. Kondoh, J. Yang, Y. Yoshida
  ISIR, Osaka

* J. Yang, T. Kondoh, K. Kan, T. Kozawa, Y. Yoshida and S. Tagawa: Nucl. Instrum. Methods Phys. Res., Sect. A 556 (2006) 52-56

• H. R. Yang
  
• M.-H. Cho, S. H. Kim, S.-I. Moon, W. Namkung
  POSTECH, Pohang, Kyungbuk
• S. D. Jang, S. J. Kwon, J.-S. Oh, S. J. Park, Y. G. Son
  PAL, Pohang, Kyungbuk

An intense L-band electron accelerator is now being installed at PAL (Pohang Accelerator Laboratory) for initial tests. It is capable of producing 10-MeV electron beams with average 30 kW. This accelerator has a diode-type E-gun, a pre-buncher cavity, and an accelerating column with the built-in bunching section. We conduct simulational study for the commissioning scenario by the PARMELA code. At first, we observe the beam position and the beam current when the beam line is misaligned under no fields. Next, turning on focusing solenoids we observe the beam position change to check the alignments of the solenoids. Finally, varying RF power and phase of the pre-buncher we observe beam energy and beam power to obtain the optimum pre-buncher condition. In this paper, we present simulational results for each step. We also present commissioning strategies based on these results.

• S. H. Kim
  
• M.-H. Cho, Y. M. Gil, S.-I. Moon, W. Namkung, H. R. Yang
  POSTECH, Pohang, Kyungbuk
• J. Jang, J.-S. Oh, S. J. Park
  PAL, Pohang, Kyungbuk

For a compact X-ray source, we designed a C-band standing-wave electron accelerator. It is capable of producing 4-MeV electron beams with 50-mA peak beam current. As an RF source, we use 5-GHz magnetron with duty factor of 0.08%. The accelerating structure is bi-periodic and on-axis coupled structure, operated with π/2-mode standing waves. Each cavity in the bunching and normal cell is designed by the MWS code and measured with aluminium prototype cavity. As per the dispersion relation derived from the measurement results, calibration factor obtained for the actual copper cavity.

• S. H. Kim
  
• M.-H. Cho, W. Namkung, H. R. Yang
  POSTECH, Pohang, Kyungbuk
• S. D. Jang, S. J. Kwon, J.-S. Oh, S. J. Park, Y. G. Son
  PAL, Pohang, Kyungbuk

An intense L-band electron accelerator is designed and under development for CESC (Cheorwon Electron-beam Service Center) irradiation applications. It is capable of producing 10-MeV electron beams with average 30 kW. For an RF source, a Thales klystron is used with 1.3 GHz, pulsed 25 MW, and average 60 kW. The accelerator column, fabricated by IHEP in China, is operated with 2π/3 mode traveling-wave under the fully-beam-loaded condition. The modulator was fabricated with inverter power supplies. The klystron was assembled to the klystron tank with pulse transformer. The high-voltage pulse test was conducted for the klystron tube. In this paper, we present design details of the accelerator and current status.

• A. Ferrari
  
• A. Latina, L. Rinolfi, F. Tecker
  CERN, Geneva

• A. Latina
  
• G. Rumolo, D. Schulte, R. Tomas
  CERN, Geneva

Dynamic imperfections in future linear colliders can lead to a significant luminosity loss. We discuss different orbit feedback strategies in the main linac that can mitigate the emittance dilution and compare their efficiency. We also address the impact of ground motion in the beam delivery system and the potential cures.

• A. Latina
  
• P. Eliasson
  Uppsala University, Uppsala
• D. Schulte
  CERN, Geneva

Misalignments in the main linac of future linear colliders can lead to significant emittance growth. Beam-based alignment algorithms, such as Dispersion Free Steering (DFS), are necessary to mitigate these effects. We study how to use the Bunch Compressor to create the off-energy beams necessary for DFS and discuss the effectiveness of this method.

• D. Schulte
  
• P. Eliasson, A. Latina
  CERN, Geneva

Complex beam-based alignment procedures are needed in future linear colliders to reduce the negative effects of static imperfections in the main linac on the beam emittance. The efficiency of these procedures could be affected by dynamic imperfections during their application. In this paper we study the resulting emittance growth.

• F. Tecker
  
• C. Biscari, A. Ghigo
  INFN/LNF, Frascati (Roma)
• E. Bressi
  CNAO Foundation, Milan
• R. Corsini, S. Doebert, P. K. Skowronski, P. Urschutz
  CERN, Geneva
• A. Ferrari
  UU/ISV, Uppsala

• I. R. Bailey, I. R. Bailey, P. Cooke, L. Zang
  Liverpool University, Science Faculty, Liverpool
• D. P. Barber
  DESY, Hamburg
• E. Baynham, T. W. Bradshaw, F. S. Carr, Y. Ivanyushenkov, J. Rochford
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon
• A. Birch
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• A. J. Brummitt, A. J. Lintern
  STFC/RAL, Chilton, Didcot, Oxon
• J. A. Clarke, J. B. Dainton, L. J. Jenner, O. B. Malyshev, L. I. Malysheva, G. A. Moortgat-Pick, D. J. Scott
  Cockcroft Institute, Warrington, Cheshire
• A. F. Hartin
  OXFORDphysics, Oxford, Oxon

Polarized electron and positron beams are foreseen for the future International Linear Collider (ILC), with polarized electrons already included in the baseline design and polarized positrons seen as a highly-desirable upgrade. High precision physics requires the polarization of both beams to be known with a relative uncertainty of approximately 0.5% or better. Therefore all possible depolarization effects that could operate between the polarized sources and the interaction regions have to be carefully modelled. The "heLiCal" collaboration aims to provide a full "cradle-to-grave" analysis of all depolarization effects at the ILC, and to develop software tools to carry out appropriate computer simulations. In this paper we report on the first phase of our work which includes extensive simulations of the ILC spin-dynamics and a detailed study of beam-beam depolarization effects at the interaction point(s).

• F. Gao
  
• M. E. Conde, W. Gai, R. Konecny, W. Liu, J. G. Power, Z. M. Yusof
  ANL, Argonne, Illinois
• C.-J. Jing
  Euclid TechLabs, LLC, Solon, Ohio
• T. Wong
  Illinois Institute of Technology, Chicago, Illinois

We report on the fabrication, simulation, and high-power testing of a C-band RF power extractor recently conducted at the Argonne Wakefield Accelerator (AWA) facility. Dielectric loaded accelerating (DLA) structures can be used for high-power RF generation [*,**] when a high-current electron beam passes through a DLA structure and loses energy into the modes of the structure due to self-wakefields. The AWA generates high charge (up to 100nC), short bunch length (1.5mm~2.5mm) electron beams, which is ideal for high-power RF generation. The generated RF power can be subsequently extracted with a properly designed extraction coupler in order to accelerate a second beam, or for other high power purposes. In this paper, the detailed design of a 7.8 GHz DLA power extractor, MAFIA simulations, and results of the high-power test are presented. Simulation predictions of an 79 MW, 2.2 ns long RF pulse (generated by a single 100 nC electron bunch) and a longer RF pulse of the same power (obtained from a 35 nC periodic bunch train) will be compared to experimental results.

* W. Gai, et al, Experimental Demonstration of Two Beam Acceleration Using Dielectric Step-up Transformer, PAC01, pp.1880-1882.** D. Yu, et al, 21GHz Ceramic RF Power Extractor, AAC02, pp.484-505.

• A. Jansson
  
• V. Balbekov, D. R. Broemmelsiek, M. Hu, N. V. Mokhov, K. Yonehara
  Fermilab, Batavia, Illinois

Within the framework of the Fermilab Muon Collider Task Force, the possibility of developing a dedicated muon test beam for cooling experiments has been investigated. Cooling experiments can be performed in a very low intensity muon beam by tracking single particles through the cooling device. With sufficient muon intensity and large enough cooling decrement, a cooling demonstration experiment may also be performed without resolving single particle trajectories, but rather by measuring the average size and position of the beam. This allows simpler, and thus cheaper, detectors and readout electronics to be used. This paper discusses muon production using 400MeV protons from the linac, decay channel and beamline design, as well as the instrumentation required for such an experiment, in particular as applied to testing the Helical Cooling Channel (HCC) proposed by Muons Inc.

• P. Lebrun
  
• L. Michelotti, J.-F. Ostiguy
  Fermilab, Batavia, Illinois

• N. Solyak
  
• K. Ranjan
  Fermilab, Batavia, Illinois

This paper reports the studies of using global emittance tuning bumps to limit the emittance growth to very small values in the main linac of the proposed International Linear Collider (ILC) machine. Simulation studies indicate that closed-orbit emittance bumps, when used after local or quasi-local beam based alignment techniques, can be utilized to further suppress the emittance growth in the ILC main linac. A series of simulations are performed to find the optimal number of bumps and their locations. A more general method of optimizing the emittance bumps in the ILC main linac is also discussed.

• N. Solyak
  
• V. Ivanov, C. S. Mishra, K. Ranjan
  Fermilab, Batavia, Illinois

The proposed International Linear Collider (ILC) machine requires extremely small transverse emittances of the beam to achieve desired luminosity. A very precise alignment of the beamline elements, both in main linac and in beam delivery system, is required to limit the emittance growth. However, ground motion (GM) and technical noise continuously misaligns the elements and hence spoils the effect of alignment. It is thus very important to understand and analyze the effect of GM on the performance of ILC. Also, it is imperative to find an effective dynamic alignment procedure to preserve the transverse emittances in the presence of GM. In this paper we study the effect of GM and technical noise on the proposed ILC main linac. Initial alignment of the Linac is performed through one-to-one and dispersion free steering (DFS). We then study "Adaptive Alignment" method to mitigate the effects of GM and technical noise.

• A. Valishev
  
• N. Solyak
  Fermilab, Batavia, Illinois
• M. Woodley
  SLAC, Menlo Park, California

• R. A. Marsh
  
• M. A. Shapiro, R. J. Temkin
  MIT/PSFC, Cambridge, Massachusetts
• E. I. Smirnova
  LANL, Los Alamos, New Mexico

Results are reported on experimental wakefield measurements made on a 6 cell, 17 GHz metallic PBG accelerator structure. Wakefields were observed using a variety of detectors and methods. The PBG structure is open, containing no outer wall, and radiation has been observed through a window in the surrounding vacuum vessel. The input and output ports have also been used with windows to observe radiation coupling out of the ports. Estimations of radiation are made using HFSS and an EFIE code. Measurements have been made using video diode detectors, wavemeters, heterodyne receivers, and a bolometer. Plans are discussed for future experiments with injected power and longer structures.

• J. C. Smith
  
• P. Eliasson
  Uppsala University, Uppsala
• K. Kubo
  KEK, Ibaraki
• A. Latina, D. Schulte
  CERN, Geneva
• P. Lebrun, K. Ranjan
  Fermilab, Batavia, Illinois
• F. Poirier, N. J. Walker
  DESY, Hamburg
• P. Tenenbaum
  SLAC, Menlo Park, California

In an effort to compare beam dynamics and create a ‘‘benchmark'' for Dispersion Free Steering (DFS) a comparison was made between different International Linear Collider (ILC) simulation programs while performing DFS. This study consisted of three parts. First, a simple betatron oscillation was tracked through each code. Secondly, a set of component misalignments and corrector settings generated from one program was read into the other to confirm similar emittance dilution. Thirdly, given the same set of component misalignments DFS was performed independently in each program and the resulting emittance dilution was compared. Performance was found to agree exceptionally well in all three studies.

• H. M. Miyadera
  
• A. J. Jason
  LANL, Los Alamos, New Mexico
• K. Nagamine
  UCR, Riverside, California

• E. K. Kallos
  
• T. C. Katsouleas, P. Muggli
  USC, Los Angeles, California
• W. D. Kimura
  STI, Washington
• P. I. Pavlishin, I. Pogorelsky, D. Stolyarov, V. Yakimenko
  BNL, Upton, Long Island, New York

We investigate various plasma wakefield accelerator schemes that rely on multiple electron bunches to drive a large amplitude plasma wave, which are followed by a witness bunch at a phase where it will sample the high acceleration gradient and gain energy. Experimental verifications of various two bunch schemes are available in the literature; here we provide analytical calculations and numerical simulations of the wakefield dependency and the transformer ratio when M drive bunches and one witness bunch are fed into a high density plasma, where M is between 2 and 10. This is a favorable setup since the bunches can be adjusted such that the transformer ratio and the efficiency of the accelerator are enhanced compared to single bunch schemes. The possibility of a five bunch ILC afterburner to accelerate a witness bunch from 100 GeV to 500 GeV is also examined.

• J. E. Spencer
  
• R. J. Noble
  SLAC, Menlo Park, California

Luminosity considerations for microscale accelerators intended for high-energy physics place a high premium on the bunch repetition rate and phase space density at the interaction point. The NLC Test Accelerator (NLCTA) at SLAC was built to address such beam dynamics issues for the Next Linear Collider and beyond. Because an S-Band RF gun has been installed together with a low-energy, high-resolving power spectrometer (LES), it is useful to explore alternatives to conventional scenarios with it. We consider possibilities that can be tested with minimal modification to this system e.g. cases that involve producing multiple bunches from the cathode in different formats such as a 2D planar matrix or 3D tensor beam made of smaller bunches or bunchlets that replace the usual, single higher charge bunches. Thus, we study configurations of interacting bunchlets n_ij or n_ijk coming from the cathode and passing through the emittance compensating solenoids that can be matched to the linac or focussed on the LES focal plane at 6 MeV. Parmela calculations have been done that show no significant space charge effects or emittance increases for pC bunchlet charges.

• J. E. Spencer
  
• E. R. Colby, R. Ischebeck, D. J. McCormick, C. Mcguinness, J. Nelson, R. J. Noble, C. M.S. Sears, R. Siemann
  SLAC, Menlo Park, California
• T. Plettner
  Stanford University, Stanford, Califormia

The NLC Test Accelerator (NLCTA) at SLAC was built to address various beam dynamics issues for the Next Linear Collider. An S-Band RF gun has been installed with diagnostics and a low energy spectrometer (LES) at 6 MeV together with a large-angle extraction line at 60 MeV. This is followed by a matching section, buncher and final focus for the laser acceleration experiment, E163. The laser-electron interaction area is followed by a broad range (2\%), high resolving power (10⁴) spectrometer (HES) for electron bunch analysis. Emittance compensating solenoids and the LES are used to tune for best operating point and match to the linac. Optical symmetries in the design of the 25.5^° extraction line provide 1:1 phase space transfer without use of sextupoles for a large, 6D phase space volume and range of input conditions. Spot sizes of a few microns at the IP (or HES object) allow tests of microscale structures as well as high resolving power at the image of the HES. Tolerances, tuning sensitivities and diagnostics are discussed together with the latest commissioning results and their comparison to design expectations.

• F. Zhou
  
• Y. K. Batygin, Y. Nosochkov, J. Sheppard, M. Woodley
  SLAC, Menlo Park, California
• W. Liu
  ANL, Argonne, Illinois

Undulator-based positron source is adopted as the International Linear Collider baseline design. Complete optics to transport the positron beam having large angular divergence and large energy spread from a thin Ti target to the entrance of the 5 GeV damping ring injection line is developed. Start-to-end multi-particle tracking through the beamline is performed including the optical matching device, capture accelerator system, transport system, superconducting booster linac, spin rotators, and energy compressor. Positron capture efficiency of different schemes (immersed vs shielded target, and flux concentrator vs quarter wave transformation for the optics matching system) is compared. For the scheme of a shielded target and quarter wave transformation, the simulation shows that 15.1% of the positrons from the target are captured within the damping ring 6-D acceptance at the entrance of the damping ring injection line.