• M. K. Sullivan
  

The achievements of the e⁺e^- Factories have been impressive. The KEK B- Factory has achieved a peak luminosity of 1.7x10³⁴ cm²/s and the PEP-II B-Factory has reached 1.2x10³⁴ cm²/s while the Dafne Phi-Factory has obtained 1.5x10³² cm²/s. Early in the B-Factory running, CP violation in the B meson system was found to be consistent with the prediction of the Standard Model. Now all three factories are integrating as much luminosity as they can in order to look for rare decay channels that may have a rate that differs from the value predicted by the Standard Model and therefore hint at New Physics. I will give a status report on the most recent accomplishments of all three factories PEP-II, KEKB and Dafne and will show what the three facilities have for plans to further improve performance.

• J. Seeman
  
• Y. Cai, M. K. Sullivan, U. Wienands
  SLAC, Menlo Park, California

For the PEP-II Operation Staff: PEP-II is an asymmetric e⁺e^- collider operating at the Upsilon 4S and has recently set several performance records. The luminosity has reached 1.2x10³⁴/cm²/s and has delivered an integrated luminosity of 910/pb in one day. PEP-II operates in continuous injection mode for both beams boosting the integrated luminosity. The peak positron current has reached 3.0 A of positrons and 1.9 A of electrons in 1732 bunches. The total integrated luminosity since turn on in 1999 has reached over 410/fb. This paper reviews the present performance issues of PEP-II and also the planned increase of luminosity in the near future to over 2 x 10³⁴/cm²/s.

• A. Novokhatski
  

We describe the method to measure total HOM losses and synchrotron losses in a storage ring based on a straightforward model of beam-cavity interaction and precise knowledge of RF power distribution. This method works well at higher currents. The comparison of the measured HOM losses and estimation for cavity and resistive wall losses is given for both LER and HER rings of the PEP-II B-factory.

• S. V. Benson
  
• K. Beard, G. H. Biallas, J. Boyce, D. B. Bullard, J. L. Coleman, D. Douglas, H. F.D. Dylla, R. Evans, P. Evtushenko, C. W. Gould, A. C. Grippo, J. G. Gubeli, D. Hardy, C. Hernandez-Garcia, C. Hovater, K. Jordan, J. M. Klopf, R. Li, S. W. Moore, G. Neil, M. Poelker, T. Powers, J. P. Preble, R. A. Rimmer, D. W. Sexton, M. D. Shinn, C. Tennant, R. L. Walker, G. P. Williams, S. Zhang
  Jefferson Lab, Newport News, Virginia

Operation of the JLab IR Upgrade FEL at CW powers in excess of 10 kW requires sustained production of high electron beam powers by the driver ERL. This in turn demands attention to numerous issues and effects, including: cathode lifetime; control of beamline and RF system vacuum during high current operation; longitudinal space charge; longitudinal and transverse matching of irregular/large volume phase space distributions; halo management; management of remnant dispersive effects; resistive wall, wake-field, and RF heating of beam vacuum chambers; the beam break up instability; the impact of coherent synchrotron radiation (both on beam quality and the performance of laser optics); magnetic component stability and reproducibility; and RF stability and reproducibility. We discuss our experience with these issues and describe the modus vivendi that has evolved during prolonged high current, high power beam and laser operation.

• T. Shintake
  

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

• R. Kersevan
  
• L. Goirand
  ESRF, Grenoble

• U. B. Blell
  
• A. V. Batrakov, S. A. Onischenko, G. E. Ozur
  Institute of High Current Electronics, Tomsk
• J. Florenkowski, U. Kopf, C. Muehle, M. Petryk, I. J. Petzenhauser, P. J. Spiller
  GSI, Darmstadt

• A. Bonucci
  
• A. Conte, P. Manini, S. Raimondi
  SAES Getters S.p. A., Lainate

• A. Conte
  
• A. Bonucci, P. Manini, S. Raimondi
  SAES Getters S.p. A., Lainate

• M. M. Shehab
  
• G. Vignola
  SESAME, Amman

• H.-S. Kang
  
• J. Choi, K. M. Ha, E.-H. Lee, W. W. Lee, I. S. Park
  PAL, Pohang, Kyungbuk

• E. Al-Dmour
  
• D. Einfeld, M. Q. Quispe
  ALBA, Bellaterra (Cerdanyola del Valles)

• A. Kumar
  
• S. C. Bapna, S. Dutta, K. Swarna
  RRCAT, Indore (M. P.)
• A. Poncet
  CERN, Geneva

Superconducting magnets are subjected to various forces during their cool down and alignment. Their construction invariably includes bellows, gimbals, hoses and composite supports. A good estimate of the deformations arising out of the cool down and alignment operations is necessary as these induce relative displacements between the fiducialised external vessel and hidden cold mass of the magnet. The nonlinear and orthotropic behaviour of these elements may make the model complicated and if solved as a nonlinear problem, would entail a large solution time as the overall model size runs into million nodes. Authors developed a unified Finite Element Model of the LHC Short Straight Section and during this process many innovative modeling techniques evolved. The developed model uses isotropic material constitutive laws with linear material properties. The paper is presenting some of the salient features of these modeling techniques.

• H.-H. Chen
  
• C.-H. Chang, T.-C. Fan, M.-H. Huang, C.-S. Hwang, J. C. Jan, F.-Y. Lin
  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

• N. Marks
  
• B. J.A. Shepherd
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

• 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.

• A. V. Zlobin
  
• G. Ambrosio, N. Andreev, E. Barzi, R. Bossert, R. H. Carcagno, G. Chlachidze, J. DiMarco, SF. Feher, V. Kashikhin, V. S. Kashikhin, M. J. Lamm, A. Nobrega, I. Novitski, D. F. Orris, Y. M. Pischalnikov, P. Schlabach, C. Sylvester, M. Tartaglia, J. C. Tompkins, D. Turrioni, G. Velev, R. Yamada
  Fermilab, Batavia, Illinois

Accelerator magnets based on Nb3Sn superconductor advances magnet operation fields above 10T and increases the coil temperature margin. Development of a new accelerator magnet technology includes the demonstration of main magnet parameters (maximum field, quench performance, field quality, etc.) and their reproducibility using short models, and then the demonstration of technology scale up using long coils. Fermilab is working on the development of Nb3Sn accelerator magnets using shell-type dipole coils and react-and-wind method. As a part of the first phase of technology development Fermilab built and tested six 1-m long dipole models and several dipole mirror configurations. The last three dipoles and two mirrors reached their design fields of 10^-11 T. Reproducibility of magnet field quality was demonstrated by all six short models. The technology scale up phase has started by building 2m and 4m dipole coils and testing them in a mirror configuration. This effort complements the Nb3Sn scale up work being performed in the framework of US LHC Accelerator Research Program (LARP). The status and main results of the Nb3Sn accelerator magnet development at Fermilab are reported.

• S. Marks
  
• K. Kennedy, D. W. Plate, D. Schlueter, M. S. Zisman
  LBNL, Berkeley, California

The positron and electron damping rings for the ILC (International Linear Collider) will contain long straight sections consisting of twenty wiggler/quadrupole pairs. The wigglers will be based upon the CESR-C superconducting design* . There are a number of challenges associated with the design of the wiggler straight vacuum system, in particular, the absorption of photon power generated by the wigglers. This paper will present the overall conceptual design of the wiggler straight vacuum system developed for the ILC RDR. Particular emphasis will be placed on photon power load calculations and the absorber design.

* A. Mihailichenko, Optimized Wiggler Magnet for CESR, Proceedings of PAC2001, Chicago, Il, June 18-22, 2001

• S. P. Virostek
  
• M. A. Green, D. Li, M. S. Zisman
  LBNL, Berkeley, California

The Muon Ionization Cooling Experiment (MICE) will demonstrate ionization cooling in a short section of a realistic cooling channel using a muon beam at Rutherford Appleton Laboratory (RAL) in the UK. A five-coil, superconducting spectrometer solenoid magnet at each end of the cooling channel will provide a 4 T uniform field region for the scintillating fiber tracker within the magnet bore tubes. The tracker modules are used to measure the muon beam emittance as it enters and exits the cooling channel. The cold mass for the 400 mm warm bore magnet consists of two sections: a three-coil spectrometer magnet and a two-coil matching section that matches the uniform field of the solenoid into the MICE cooling channel. The detailed design and analysis of the two spectrometer solenoids has been completed, and the fabrication of the magnets is in its final stages. The primary features of the spectrometer solenoid magnetic and mechanical designs are presented along with a summary of key fabrication issues and photos of the fabrication process.

• M. A. Green
  
• X. L. Guo, G. Han, L. Jia, L. K. Li, S. Y. Li, C. S. Liu, X. K. Liu, L. Wang, H. Wu, F. Y. Xu
  ICST, Harbin
• S. P. Virostek
  LBNL, Berkeley, California

The Muon Ionization Cooling Experiment (MICE) will demonstrate ionization cooling in a short section of a realistic cooling channel using a muon beam at Rutherford Appleton Laboratory (RAL) in the UK. The MICE RF and Coupling Coil Module comprises a superconducting solenoid mounted around four normal conducting 201.25-MHz RF cavities. Each cavity has a pair of thin curved beryllium windows to close the conventional open beam irises. The coil package that surrounds the RF cavities is to be mounted on the outside of a 1.4 m diameter vacuum vessel. The coupling coil confines the beam in the cavity module and, in particular, within the radius of the cavity beam windows. The two MICE coupling solenoids will be operated in series using a 300 A, 10 V power supply. The maximum longitudinal force that will be carried by the cold mass support system is 0.5 MN during the expected operating and failure modes of the experiment. The detailed design and analysis of the two coupling coils has been completed, and the fabrication of the magnets is under way. The primary magnetic and mechanical design features of the coils are presented along with a summary of key fabrication issues.

• P. Quigley
  
• S. A. Belomestnykh, M. Liepe, V. Medjidzade, J. Sears, V. Veshcherevich
  CLASSE, Ithaca

Cornell is building a 1.3 GHz Injector Cryomodule for an ERL prototype. The cryomodule consists of five two-cell niobium cavities each cavity having two coaxial power input couplers. Cavity and coupler pairs will require acceptance testing at high power prior to assembly in the injector cryomodule. A liquid nitrogen cryostat for testing the couplers at high power has been built and the first input coupler test is complete. In addition, a Horizontal Test Cryostat (HTC) is being built to test input coupler pairs and cavities as a set. The first HTC test is scheduled for spring 2007. Details for instrumentation of the Coupler Test Cryostat (CTC) and HTC are presented.

• E. R. Olivas
  

Thin windows are devices required by some particle accelerator physics experiments. These windows must be thin and light enough so they have a minimum effect on the beam. However, due to the boundary and loading conditions a window might observe; nonlinear structural behavior can occur from a number of different causes, such as geometric and material nonlinearities. If a structure experiences large plastic deformation, its changing geometric relationship can cause the structure to respond in a nonlinear manner. Material nonlinearities occur when the material's stress-strain relation depends on the load history as in plasticity models. The method of analysis for this study entails an FEA analysis, in which the stress and displacement are solved for a metallic membrane; these results are then compared to results obtained from an iterative process in relating the stress and strain with respect to the deformed geometry of the membrane. In addition, multiple experimental tests will be carried out to determine the membrane displacement from a prescribed load. Also included in this test will be the burst pressure or failure point of the membrane. The study is conducted on 1100 series Al.

• 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

• W. Wittmer
  
• W. S. Colocho, G. R. White
  SLAC, Menlo Park, California

The controls software in use at PEP II had originally been developed in the eighties. The functionality and maturity of the applications in that system have made it very successful in routine operation, but this same longevity and orientation toward fixed requirements, make it largely unsuitable for rapid machine development and ad-hoc online experimentation. A successful recent trend at light sources has been to use the so called MATLAB Middle Layer (MML). This package abstracts each underlying control system framework to which it is connected, such as Channel Access. We describe the middle layer implementation for PEP II and LCLS based on AIDA (described elsewhere in these proceedings), which is unusual in that it provides access to the high level functionality of the legacy control system, as well as to a very large assortment of useful data in addition to channel access read and control. The MML had to be adapted for the implementation at PEP II since colliders differ significantly from light sources by scale and symmetry of the lattice, and PEP II is the first collider at which such an implementation is being done.

• L. Bees
  
• L. Simpson, A. Tydeman
  Lambda, Neptune, New Jersey

• G. Cheng
  
• E. Daly, R. A. Rimmer, M. Stirbet, L. Vogel, H. Wang, K. Wilson
  Jefferson Lab, Newport News, Virginia

For an ongoing high current cryomodule project, a total of 5 higher order mode (HOM) absorbers are required per cavity. The load is designed to absorb RF heat induced by HOMs in a 748.5MHz cavity. Each load is targeted at a 4 kW dissipation capability. Embedded cooling channels are employed to remove the heat generated in ceramic tiles and by surface losses on the waveguide walls. A sequentially coupled RF-thermal-structural analysis was developed in ANSYS to optimize the HOM load design. Frequency dependent dielectric material properties measured from samples and RF power spectrum calculated by the beam-cavity interaction codes were considered. The coupled field analysis capability of ANSYS avoided mapping of results between separate RF and thermal/structural simulation codes. For verification purposes, RF results obtained from ANSYS were compared to those from MAFIA, HFSS, and Microwave Studio. Good agreement was reached and this confirms that multiple-field coupled analysis is a desirable choice in analysis of HOM loads. Similar analysis could be performed on other particle accelerator components where distributed RF heating and surface current induced losses are inevitable.

• D. Stout
  
• S. Assadi, I. E. Campisi, F. Casagrande, M. T. Crofford, W. R. DeVan, X. Geng, T. W. Hardek, S. Henderson, M. P. Howell, Y. W. Kang, W. C. Stone, W. H. Strong, D. C. Williams, P. A. Wright
  ORNL, Oak Ridge, Tennessee

The SNS project was completed with only limited SRF facilities installed as part of the project, namely a 5 MW, 805 MHz RF test stand, a fundamental power coupler processing system, a concrete test cave shell, and temporary cleaning/assembly facilities. A concerted effort has been initiated to install the infrastructure and equipment necessary to maintain and repair the superconducting Linac, and to support power upgrade R&D. Installation of a Class10/100/10,000 cleanroom and outfitting of the test cave with RF, vacuum, controls, personnel protection and cryogenics systems is underway. A horizontal cryostat, which can house a helium vessel/cavity and fundamental power coupler for full power, pulsed testing, is being procured. Equipment for cryomodule assembly/disassembly and cavity processing also is being designed. This effort, while derived from the experience of the SRF community, will provide a unique high power test capability as well as long term maintenance capabilities. This paper presents the current status and the future plans for the SNS SRF facilities.

• 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.

• C. Nieter
  
• P. J. Mullowney, S. Ovtchinnikov, D. S. Smithe, P. Stoltz
  Tech-X, Boulder, Colorado

* C. Nieter, J. R. Cary, J. Comp. Phys. 196 (2004) 448.** S. Dey, R. Mittra, IEEE Microwave and Guided Wave Letters 7 (1997) 273.

• G. Leyh
  

Construction of the ILC 'Reference Design' Marx Modulator is complete, and testing is currently underway at SLAC. The Reference Design prototype is oil-free, air-cooled, and capable of delivering 120kV, 140A pulses at a rate of 5Hz. Total energy per pulse is 23,500 joules. Projected efficiency is greater than 96%. The Reference Design Marx modulator employs a stack of 12kV Marx modules that generate high-voltage output pulses directly from a 12kV input supply voltage. This direct switching eliminates the requirement for a massive transformer and reduces the capacitor bank size by more than a factor of four, yielding a considerably cheaper and more compact mechanical solution. Advantages of the Marx design include higher efficiency, smaller physical size, and a modular architecture that provides greater reliability and cost-effective PC board-level integration. This paper outlines the ILC Marx Modulator Development Program currently underway at SLAC. The paper presents detailed mechanical and electrical design diagrams, 3D field simulations, and operational test results for the full-scale Reference Design modulator prototype.

• W. L. Waldron
  
• R. J. Briggs
  SAIC, Alamo, California
• A. Friedman
  LLNL, Livermore, California
• E. Henestroza, L. R. Reginato
  LBNL, Berkeley, California

The Pulse Line Ion Accelerator concept was motivated by the need for an inexpensive way to accelerate intense short pulse heavy ion beams to regimes of interest for studies of High Energy Density Physics and Warm Dense Matter. A pulse power driver applied to one end of a helical pulse line creates a traveling wave that accelerates and axially confines the heavy ion beam pulse. The concept has been demonstrated with ion beams at modest acceleration gradients. Acceleration scenarios with constant parameter helical lines are described which result in output energies of a single stage much larger than the several hundred kilovolt peak voltages on the line, with a goal of 3-5 MeV/m acceleration gradients. This method has the potential to reduce the length of an equivalent induction accelerator by a factor of 6-10 while simplifying the pulsed power systems. The performance of prototype hardware has been limited by high voltage flashover across the vacuum insulator. Bench tests and analysis have led to significantly improved flashover thresholds. Further studies using a variety of experimental configurations are planned.

• 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.

• P. Chen
  
• M. Lundquist, R. Yi, D. Yu
  DULY Research Inc., Rancho Palos Verdes, California

High-gradient electron guns can suppress space-charge induced transverse emittance growth when the electron beam is still in the low-energy injection stage. A synchronizable, high-voltage pulser can be used to power up a high-gradient gun. We propose to build a 200 kV pulser using a special trigger that utilizes a laser-photocathode sub-system. A laser trigger beam will first energize a spark gap, and then provide a second trigger signal from a photocathode using its leftover energy, to further close the gap. This system will not only raise the utilization efficiency of the laser beam energy, but also enhance the reliability of the trigger circuit. Our preliminary analysis shows that the proposed system will significantly improve the performance of the laser trigger pulse with the jitter on the order of hundreds of picoseconds. It is expected that the pulser can be used in the applications of high gradient guns as well as in other devices that need high precision trigger such as short pulse lasers, streak cameras, impulse radiating antennas, etc.

• J. A. Ellison
  
• G. Bassi, K. A. Heinemann
  UNM, Albuquerque, New Mexico
• M. Venturini
  LBNL, Berkeley, California
• R. L. Warnock
  SLAC, Menlo Park, California

We discuss our progress on integration of the coupled Vlasov-Maxwell equations in 4D. We emphasize Coherent Synchrotron Radiation from particle bunches moving on arbitrary curved planar orbits, with shielding from the vacuum chamber, but also include space charge forces. Our approach provides simulations with lower numerical noise than the macroparticle method, and will allow the study of emittance degradation and microbunching in bunch compressors. The 4D phase space density (PSD) is calculated in the beam frame with the method of local characteristics (PF). The excited fields are computed in the lab frame from a new double integral formula. Central issues are a fast evaluation of the fields and a deep understanding of the support of the 4D PSD. As intermediate steps, we have (1) developed a parallel self-consistent code using particles, where an important issue is the support of the charge density*; (2) studied carefully a 2D phase space Vlasov analogue; and (3) derived an improved expression of the field of a 1D charge/current distribution which accounts for the interference of different bends and other effects usually neglected**. Results for bunch compressors are presented.

* Self Consistent Particle Method to Study CSR Effects in Bunch Compressors, Bassi, et.al., this conference.** CSR from a 1-D Bunch on an Arbitrary Planar Orbit, Warnock, this conference.

• J. J. Petillo
  
• K. Jensen, B. Levush
  NRL, Washington, DC
• J. N. P. Panagos
  SAIC, Burlington, Massachusetts

Low emittance, high current density sources are required to achieve the small beam size needed for high frequency vacuum electronic devices and for high power free electron lasers (FELs). Emission models are of particular importance in the emittance-dominated regime, where emission non-uniformity and surface structure of the cathode can have an impact on beam characteristics. We have been developing comprehensive time-dependent photoemission models for the simulation codes that account for laser and cathode material and surface characteristics. MICHELLE* is NRL's finite-element self-consistent electrostatic time-domain code: it has the ability to import an RF field, and has unique capabilities for modeling the emission and the self fields, near the cathode. In particular, some instances of surface irregularities and emission non-uniformity (due to work function variation) leading to such effects as beam emittance and high frequency oscillations are possible to model due to the code's conformal meshing capabilities. We will present results of the implementation of the 'next generation' photoemission models in the MICHELLE code for modeling surface roughness and non-uniformity.

* John Petillo, et al., "The MICHELLE Three-Dimensional Electron and Collector Modeling Tool: Theory and Design", IEEE Trans. Plasma Sci., vol. 30, no. 3, June 2002, pp. 1238-1264.

• A. Jackson
  

• M. J. Spencer
  
• M. J. Boland, R. T. Dowd, G. LeBlanc, Y. E. Tan
  ASP, Clayton, Victoria

• C. Benabderrahmane
  
• P. Berteaud, F. Briquez, P. Brunelle, O. V. Chubar, M.-E. Couprie, J.-M. Filhol, M. Girault, O. Marcouille, F. Marteau, M. Massal, F. Paulin, M. Valleau, J. Veteran
  SOLEIL, Gif-sur-Yvette

• S. Casalbuoni
  
• T. Baumbach, A. Bernhard, D. Wollmann
  University of Karlsruhe, Karlsruhe
• A. W. Grau, M. Hagelstein, B. K. Kostka, R. Rossmanith
  FZK, Karlsruhe
• E. Mashkina, E. Steffens
  University of Erlangen-Nurnberg, Physikalisches Institut II, Erlangen
• F. Zimmermann
  CERN, Geneva

• S. Lederer
  
• G. Asova, J. W. Baehr, C. H. Boulware, H.-J. Grabosch, M. Hanel, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, B. Petrosyan, S. Rimjaem, T. A. Scholz, L. Staykov, F. Stephan
  DESY Zeuthen, Zeuthen
• K. Boyanov
  INRNE, Sofia
• L. H. Hakobyan
  YerPhI, Yerevan
• P. Michelato, L. Monaco, C. Pagani, D. Sertore
  INFN/LASA, Segrate (MI)
• R. Richter
  BESSY GmbH, Berlin
• J. Roensch
  Uni HH, Hamburg

Beginning 2007, a new gun cavity will be installed at the photo injector test facility at DESY in Zeuthen (PITZ). It will be conditioned towards gradients as high as 60 MV/m. This gradient is required for the operation of the European XFEL. Results from the conditioning for high peak power and high duty cycle will be reported.

• G. D'Auria
  
• D. Bacescu, L. Badano, F. Cianciosi, P. Craievich, M. B. Danailov, G. Penco, L. Rumiz, M. Trovo, A. Turchet
  ELETTRA, Basovizza, Trieste
• H. Badakov, A. Fukasawa, B. D. O'Shea, J. B. Rosenzweig
  UCLA, Los Angeles, California

• C. Ronsivalle
  
• A. Bacci, A. R. Rossi, L. Serafini
  INFN-Milano, Milano
• M. Boscolo, E. Chiadroni, M. Ferrario, D. Filippetto, V. Fusco, G. Gatti, M. Migliorati, A. Mostacci, C. Vaccarezza, C. Vicario
  INFN/LNF, Frascati (Roma)
• A. Cianchi
  INFN-Roma II, Roma
• L. Giannessi, M. Quattromini
  ENEA C. R. Frascati, Frascati (Roma)
• M. Petrarca
  Universita di Roma I La Sapienza, Roma

• G. Gatti
  
• A. M. Cook, J. B. Rosenzweig, R. Tikhoplav
  UCLA, Los Angeles, California

• N. Nakamura
  
• H. Sakai, H. Takaki
  ISSP/SRL, Chiba

* J. M. Wang and J. Wu, PRST-AB 7, 034402(2004)

• S. Takama
  
• R. T. Dowd, A. Jackson, G. LeBlanc, K. Zingre
  ASP, Clayton, Victoria
• Y. Hirata, H. Kamikubo, Y. Nobusada, H. Suzuki
  Toshiba, Yokohama

• D. Einfeld
  

• E. Trakhtenberg
  
• G. E. Wiemerslage
  ANL, Argonne, Illinois

Multiple vacuum chambers for the insertion devices with 1-mm wall thickness were developed at Argonne for the APS and many other synchrotron radiation facilities.* Using the extrusion for the insertion device vacuum chamber (ID VC) for the DESY FEL project with a 9.5-mm inner diameter, we decreased the wall thickness to 0.6, 0.5, and 0.4 mm to test the vacuum integrity for a thin wall in these extrusions. A special ultrasonic transducer with a 1/8" diameter was required to do the job. Also some additional short samples, machined exactly as the experimental piece, were used to verify wall thickness mechanically. Experimental setup and test results are presented.

* Trakhtenberg E., Wiemerslage G., Den Hartog P. "New insertion device vacuum chambers at the Advanced Photon Source", PAC 2003 Particle Accelerator Physics Conference; Portland, OR.

• V. D. Shiltsev
  

• H. Nishimura
  
• R. J. Donahue, R. M. Duarte, D. Robin, F. Sannibale, C. Steier, W. Wan
  LBNL, Berkeley, California

We plan to commission top-off injection at the Advanced Light Source in the near future. In order to guarantee radiation safety, we have been simulating the injection process to exclude the possibility of injected electrons traveling down the user's photon beam lines. As the final stage of our simulation study, we use photon beam line CAD drawings to define the beam line's aperture in the phase space which electrons must not enter. Then we virtually inject electrons from within these phase spaces backwards into the storage ring to prove that such electrons can never get back to the real injection point under any possible scenario. This paper summarizes such inverse tracking studies.

• C. K. Sinclair
  
• I. V. Bazarov, B. M. Dunham, Y. Li, X. G. Liu
  Cornell University, Department of Physics, Ithaca, New York
• K. W. Smolenski
  CLASSE, Ithaca

We have constructed a very high voltage photoemission electron gun as the electron source of a high brightness, high average current injector for an energy recovery linac (ERL) synchrotron radiation light source. The source is designed to deliver 100 mA average current in a CW 1300 MHz pulse train (77 pC/bunch). The cathode voltage may be as high as 750 kV. Negative electron affinity photocathodes are employed to obtain small thermal emittances. The electrode structure is assembled without touching any electrode surface. A load-lock system allows cleaning and activation of cathode samples prior to installation in the electron gun. Cathodes are cleaned by heating and exposure to atomic hydrogen, and activated with cesium and nitrogen trifluoride. Two cathode electrode sets, of 316LN stainless steel and Ti4V6Al alloy, have been used. The anode is beryllium. The internal surface of the ceramic insulator of the gun has a high resistivity fired coating, providing a path to drain away charge from field emission. Non-evaporable getters provide a very high pumping speed for hydrogen. Operating experience with this gun will be presented.

• J. Kulesza
  
• N. Chen
  SSRF, Shanghai
• A. Deyhim
  Advanced Design Consulting, Inc, Lansing, New York

This paper summarizes the primary controller that is based on Schneider Premium PLC for two in-vacuum undulators to be installed at SSRF. The PLC controls a single gap stepper motor and driver, both made by Parker-Hannifin. Position feedback is derived from a TR Electronics linear absolute LTS-240 encoder mounted across the gap. The encoder resolution is programmable down to .1 um per count. Since the encoder is absolute there will be no need to home the gap axis. The advantage of linear encoders is the measurement is more direct and is not subject to wind-up and deflection that a rotary encoder would see on the end of a ball screw. Two encoders are planned, one on each end of the magnet array. One encoder will be the primary feedback for the axis and the other will detect deflection errors and girder taper. Four limits are provided as well as 4 kill switches. The 4 switches (2 limits and 2 kills) at min gap are optical and the 4 outer switches (2 limits and 2 kills) are mechanical. The limits prevent further motion in the direction they protect but allow the axis to be driven in the other direction (off the switch).

• R. A. Bosch
  

A 2.1 GeV electron storage ring can serve as a third-generation light source for photon energies of 1-2000 eV. We design a ring with emittance of 1.5 nm-rad, circumference of 215 m, and twelve 5.5 m long straight sections. With a 100 MHz radiofrequency (rf) system, the computed Touschek current-lifetime product is 2800 mA-hr. Two passive fifth-harmonic cavities may be used to suppress parasitic coupled-bunch instabilities while increasing the bunchlength and lifetime by a factor of four. For stable operation with ring currents up to 600 mA, microwave-instability simulations indicate that the reduced longitudinal impedance should not exceed 1.5Ω.

• D. Dowell
  
• E. N. Jongewaard, C. Limborg-Deprey, J. F. Schmerge, A. E. Vlieks
  SLAC, Menlo Park, California

The field emission was measured during the high-power testing of the LCLS photocathode RF gun. A careful study and analysis of the field emission electrons, or dark current is important in assessing the gun's internal surface quality in actual operation, especially those surfaces with high fields. The charge per 2 microsecond long RF pulse (the dark charge) was measured as a function of the peak cathode field for the 1.6 cell, 2.856GHz LCLS RF gun. Faraday cup data was taken for cathode peak RF fields up to 120MV/m producing a maximum of 0.6nC/RF pulse for a diamond-turned polycrystalline copper cathode installed in the gun. The field dependence of the dark charge is analyzed using a temperature-dependent Fowler-Nordheim (FN) theory to obtain the field enhancement factor and other emitter parameters. Digitized images of the dark charge were taken using a 100 micron thick YAG crystal for a range of solenoid fields to determine the location and angular distribution of the field emitters. The FN plots and emitter image analysis will be described in this paper.

• T. Plettner
  
• R. L. Byer
  Stanford University, Stanford, Califormia

• A. France
  
• O. Delferriere, M. Desmons, O. Piquet
  CEA, Gif-sur-Yvette

• C. Omet
  
• D. Hoffmann, P. J. Spiller
  GSI, Darmstadt

Beam loss caused by charge changing process in connection with dynamic vacuum effects may limit the maximum number of accelerated heavy ions with low charge states in the existing synchrotron SIS18 and the planned SIS100/SIS300 of the FAIR project. With the aim to stabilize the vacuum dynamics and to control ionization beam loss, a substantial upgrade program has been defined for SIS18 and is presently realized. For SIS100, a new lattice design concept has been developed, where each lattice cell acts as a charge seperator and thereby enables the local control of beam loss. Simulation, conducted with the code STRAHLSIM, of the time dependent evolution of beam loss, dynamic residual gas pressure and the effect of the proposed dedicated ion catcher systems will be presented.

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

• V. Variale
  
• P. A. Bak, G. I. Kuznetsov, B. A. Skarbo, M. A. Tiunov
  BINP SB RAS, Novosibirsk
• A. Boggia
  Universita e Politecnico di Bari, Bari
• T. Clauser, V. Valentino
  INFN-Bari, Bari
• A. C. Raino
  Bari University, Science Faculty, Bari

The Radioactive Ion Beam (RIB) production with ISOL technique should require a charge breeder device to increase the ion acceleration efficiency and reduce greatly the production cost. The "charge breeder" is a device designed to accept RIB with charge state +1 and in order to increase their charge state up to +n. Recently, at the INFN section of Bari first and at LNL (Italy) then, a new charge breeder device, based on an EBIS ion source called BRIC, has been developed. The new feature of BRIC, with respect to the classical EBIS, is given by the insertion, in the ion drift chamber, of a Radio Frequency (RF) - Quadrupole aiming to filtering the unwanted masses and then making a selective more efficient containment of the wanted ions. The RF test measurements for Ar gas confirm, as foreseen by simulation results* that the selective containment can be obtained. More measurements on the selective containment of heavier element ions (more close to the radioactive ion produced with ISOL technique) like Xe are needed to study with more details that effect. In this contribution new measurements on the rf selective containement in BRIC for Xe gas will be presented and discussed.

* V. Variale and M. Claudione, "BRICTEST: a code for charge breeding simulations in RF quadrupolar field", NIM in Phys. res. A 543 (2005) 403-414.

• S. Tomassini
  
• D. Alesini, A. Beatrici, A. Clozza, E. Di Pasquale, G. Fontana, F. Marcellini, G. Mazzitelli, M. Paris, P. Raimondi, C. Sanelli, G. Sensolini, F. Sgamma, M. Troiani, M. Zobov, A. Zolla
  INFN/LNF, Frascati (Roma)
• M. E. Esposito
  Rome University La Sapienza, Roma

* DAPHNE Upgrade Team, "DAPHNE Upgrade for Siddharta run", DAPHNE Tech. Note G-68, Dec. 2006.

• Y. Funakoshi
  

• 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

• 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.

• M. J. Barnes
  
• F. Caspers, L. Ducimetiere, N. Garrel, T. Kroyer
  CERN, Geneva

• Th. Weiler
  
• O. Aberle, R. W. Assmann, R. Chamizo, Y. Kadi, J. Lettry, S. Redaelli
  CERN, Geneva

• 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

• B. C. Brown
  
• D. Capista, I. Kourbanis, N. V. Mokhov, V. Sidorov
  Fermilab, Batavia, Illinois

A collimation system has been created for removing proton beam halo in the 8 GeV transfer line from the Fermilab Booster to Main Injector. A pair of 1.14 meter collimators with 5.08 cm rectangular apertures are installed in a 5 meter straight section. Horizontal and vertical motion systems allow them to be positioned such that halo can be scraped from four sides. An additional pair of collimators, placed one cell (90 degrees) downstream scrape halo which is of opposite phase. Each collimator pair can scrape about 600 Watts of beam power, limited by long term activation of materials outside of the beam line tunnel. Personnel exposure is reduced by surrounding the iron absorber with a layer of marble. Design features,radiation calculations and instrumentation considerations will be described.

• V. Kamerdzhiev
  
• R. J. Hively, G. F. Kuznetsov, H. Pfeffer, G. W. Saewert, V. D. Shiltsev, X. Zhang
  Fermilab, Batavia, Illinois

• M. A. Kostin
  
• L. Ahle, S. Reyes, K. L. Whittaker
  LLNL, Livermore, California
• I. Baek, V. Blideanu, G. Bollen, D. Lawton, R. M. Ronningen
  NSCL, East Lansing, Michigan
• T. Burgess, D. L. Conner, T. A. Gabriel, R. Remec
  ORNL, Oak Ridge, Tennessee
• D. J. Vieira
  LANL, Los Alamos, New Mexico

• U. Wienands
  
• W. S. Colocho, S. DeBarger, F.-J. Decker, S. Ecklund, A. S. Fisher, J. D. Fox, A. Kulikov, A. Novokhatski, M. Stanek, M. K. Sullivan, W. Wittmer, D. Wright, G. Yocky
  SLAC, Menlo Park, California

During Run 5, PEP-II has been plagued by beam instabilities causing beam aborts due to radiation in the BaBar detector or due to fast beam loss triggering the dI/dt interlock. The latest of such instabilities occurred in the High Energy Ring (HER), severely curtailing the maximum beam current achievable during physics running. Techniques used in tracking down this instability included fast monitoring of background radiation, temperatures and vacuum pressure. In this way, the origin of the instability was localized and inspection of the vacuum system revealed several damaged bellows shields. Replacing these units significantly reduced the incident rate but did not eliminate it fully. After the end of the run, a number of damaged rf seals were found, possibly having caused the remaining incidents of instability. In this paper we will outline the steps taken to diagnose and remedy the issue and also compare the different signatures of vacuum-induced instabilities we have seen in both rings of PEP-II during the run.

• S. Y. Zhang
  
• D. Trbojevic
  BNL, Upton, Long Island, New York

There are three main sources of the experimental background at RHIC. The beam-gas induced background is associated with the vacuum pressure, the beam-chamber-interaction induced background can be improved by collimations, and the beam-beam induced background is somewhat inherent, and probably harmless for the experimental data taking. The zero degree calorimeter (ZDC) is an essential luminosity detector for heavy ion operations in RHIC. It is shown that, however, the ratio of ZDC singles (background) and coincident rate is also useful in proton runs for background evaluations. In this article, the experimental background problem in RHIC polarized proton runs is reported.

• M. T.F. Pivi
  
• R. E. Kirby, T. W. Markiewicz, T. O. Raubenheimer, J. Seeman, L. Wang
  SLAC, Menlo Park, California
• F. Le Pimpec
  PSI, Villigen

Possible remedies for the electron cloud in the Damping Ring of the International Linear collider includes conditioning of the surface and chamber with grooves. We installed chambers in PEP-II to test the secondary electron yield (SEY) of coated TiN and TiZrV NEG samples and study the effect of electron and photon conditioning in situ. We have also installed vacuum chambers with rectangular groove profile in straight sections to test this possible mitigation technique. In this paper, we will describe the PEP-II test layout, results and impact on impedance.

• F. Caspers
  
• F.-J. Behler
  Eisenwerke Fried. Wilh. Dueker GmbH & Co. KGaA, Laufach
• P. P. Hellmold
  Clausthal, Inst für Nichtmetall. Werkstoffe, Clausthal-Zellerfeld
• T. Kroyer, E. Metral, F. Zimmermann
  CERN, Geneva
• J. Wendel
  Wendel GmbH, Dillenburg

• X. Chang
  
• I. Ben-Zvi, A. Burrill, J. G. Grimes, T. Rao, Z. Segalov, J. Smedley
  BNL, Upton, Long Island, New York
• Q. Wu
  IUCF, Bloomington, Indiana

• K. Dunkel
  
• B. A. Aminov
  CRE, Wuppertal
• J. Hottenbacher, C. Piel
  ACCEL, Bergisch Gladbach

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

In this presentation, we will report on a comprehensive vibration measurement program of a superconducting accelerating module designed for the European X-ray Free Electron Laser (XFEL), currently planned at DESY, at room temperature. This module is a type III, high gradient module which is also the basis of module design for the International Linear Collider (ILC). We will discuss stability within the vessel, for example, cold mass vs. He Gas Return Pipe (GRP), as well as stability along the length of the module. Results of this study may be used for the design of future XFEL/ILC module prototypes.

• 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.

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

• T. Semba
  
• Y. Itou, S. Kajiura, T. Masumoto, T. Tagawa
  Hitachi Ltd., Ibaraki-ken
• S. Noguchi, N. Ohuchi, K. Saito, A. Terashima, K. Tsuchiya
  KEK, Ibaraki

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

* C. Ohmori at. al, "High Field-Gradient Cavity for J-PARC 3 GeV RCS", PAC 2004

• Z. G. Zong
  
• F. Furuta, H. Inoue, T. Saeki, K. Saito
  KEK, Ibaraki
• J. Gao, M. Q. Ge, Q. J. Xu, J. Y. Zhai
  IHEP Beijing, Beijing

• X. D. He
  
• S. Dong, Y. J. Pei, C.-F. Wu
  USTC/NSRL, Hefei, Anhui

We have developed the mathod to determine the permittivity and permeability of Kanthal alloy available. The alloy is coated on the inside walls of disk-loaded cavities,which is used for the collinear load. The collinear load absorbs the remaining rf-power over the last cells of the section while still accelerating the beam. Based on the experimental results of the permittivity and permeability,the computation study of the constant power-loss collinear load has been made by Microwave Studio. The design data about the S-band collinear load are present.

• B. H. Chung
  
• K.-H. Chung
  KAPRA, Cheorwon
• J. S. Hong, J. H. Jeon, S. J. Noh
  Dankook University, Seoul
• S. K. Ko
  University of Ulsan, Ulsan

• Y. U. Sohn
  
• J. Choi, M.-H. Chun, J. Y. Huang, I. S. Ko, I. S. Park
  PAL, Pohang, Kyungbuk

Pohang Accelerator Laboratory has prepared to SRF 3rd harmonic cavity to increase beam lifetime and to damp orbit instability by lengthening electron bunch in PLS. The SRF cavity was developed and its vertical test was done already with success. Higher order modes were analyzed to optimize its performance in beam orbit. Most of them are not effective to electron beam, while the others have possibility to impact orbit stability. These harmful HOMs can be removed by HOM absorber installed in beam pipe. This paper reports the HOM analysis and design of its removal system.

• 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

• D. Horan
  
• D. J. Bromberek, D. A. Meyer, G. J. Waldschmidt
  ANL, Argonne, Illinois

High-power tests were conducted on a 350MHz, single-cell copper accelerating cavity driven simultaneously by two H-loop input couplers for the purpose of determining the reliability, performance, and power-handling capability of the cavity and related components, which have routinely operated at 100kW power levels. The test was carried out utilizing the APS 350MHz RF Test Stand, which was modified to split the input rf power into two 1/2-power feeds, each supplying power to a separate H-loop coupler on the cavity. Electromagnetic simulations of the two-coupler feed system were used to determine coupler match, peak cavity fields, and the effect of phasing errors between the coupler feedlines. The test was conducted up to a maximum total rf input power to the cavity of 200kW CW. Test apparatus details and performance data will be presented.

• K. W. Shepard
  
• Z. A. Conway, J. D. Fuerst, M. P. Kelly, G. J. Waldschmidt
  ANL, Argonne, Illinois
• A. M. Porcellato
  INFN/LNL, Legnaro, Padova

This paper reports the development of a 5-10 kW cw variable coupler for 345 MHz spoke-loaded superconducting (SC)cavities. The coupler inserts an 80K copper loop into a 5 cm diameter coupling port on several types of spoke-loaded cavity operating at 2 - 4K. The coupling loop can be moved during operation to vary the coupling over a range of 40 dB. The coupler is designed to facilitate high-pressure water rinsing and low-particulate clean assembly. Design details and operating characteristics are discussed.

• T. W. Koeth, T. W. Koeth
  Rutgers University, The State University of New Jersey, Piscataway, New Jersey
• J. Branlard, H. Edwards, R. P. Fliller, E. R. Harms, A. Hocker, M. McGee, Y. M. Pischalnikov, P. S. Prieto, J. Reid
  Fermilab, Batavia, Illinois

Valuable experience in operating and maintaining superconducting RF cavities in a horizontal test module has been gained with Capture Cavity II. We report on all facets of our experience to date.

• E. R. Harms
  
• T. T. Arkan, L. Bellantoni, H. Carter, H. Edwards, M. Foley, T. N. Khabiboulline, D. V. Mitchell, D. R. Olis, A. M. Rowe, N. Solyak
  Fermilab, Batavia, Illinois

Fermilab is involved in an effort to assemble 3.9 GHz superconducting RF cavities into a four cavity cryomodule for use at the DESY TTF/FLASH facility as a third harmonic structure. The design gradient of these cavities is 14 MV/m limited by thermal heat transfer. This effort involves design, fabrication, intermediate testing, assembly, and eventual delivery of the cryomodule. We report on all facets of this enterprise from design through future plans. Included will be test results of single 9-cell cavities, lessons learned, and current status.

• 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/

• J. Li
  
• E. R. Harms, T. Kubicki, D. J. Nicklaus, D. R. Olis, P. S. Prieto, J. Reid, N. Solyak
  Fermilab, Batavia, Illinois
• T. Wong
  Illinois Institute of Technology, Chicago, Illinois

The FLASH user facility providing free electron laser radiation is built based on the TTF project at DESY. Fermilab has the responsibility for the design and processing of a third harmonic, 3.9 GHz, superconducting cavity which is powered via a coaxial power coupler. Six power couplers have been manufactured at CPI after successful design of the power coupler including RF simulation, multipacting calculation, and thermal analysis. The power couplers are being tested and processed with high pulsed power in an elaborate test stand at Fermilab now. This paper presents the RF design and processing work of the power coupler.

• M. McGee
  
• Y. M. Pischalnikov
  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

• 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

• J. P. Ozelis
  
• R. H. Carcagno, C. M. Ginsburg, Y. Huang, B. Norris, T. Peterson, V. Poloubotko, R. Rabehl, I. Rakhno, C. Reid, D. A. Sergatskov, C. Sylvester, M. Wong, C. Worel
  Fermilab, Batavia, Illinois

As part of a program to improve cavity performance reproducibility for the ILC, Fermilab is developing a facility for vertical testing of SRF cavities. It operates at a nominal temperature of 2K, using an existing cryoplant that can supply LHe in excess of 20g/sec and provides steady-state bath pumping capacity of 125W at 2K. The below-grade cryostat consists of a 4.9m long vacuum vessel and 4.5m long LHe vessel. The cryostat is equipped with external and internal magnetic shielding to reduce the ambient magnetic field to <10mG. Internal fixed and external movable radiation shielding ensures that radiation levels from heavily field-emitting cavities remain low. In the event that radiation levels exceed allowable limits, an integrated personnel safety system consisting of RF switches, interlocks, and area radiation monitors disables RF power to the cavity. In anticipation of increased throughput requirements that may be met with additional test stand installations, sub-systems have been designed to be easily upgradeable or to already meet these anticipated needs. Detailed facility designs, performance during system commissioning, and results from initial cavity tests are presented.

• 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.

• T. N. Khabiboulline
  
• C. A. Cooper, N. Dhanaraj, H. Edwards, M. Foley, E. R. Harms, D. V. Mitchell, A. M. Rowe, N. Solyak
  Fermilab, Batavia, Illinois
• W.-D. Moller
  DESY, Hamburg

• K. M. Baptiste
  
• P. W. Casey, S. Kwiatkowski, CA. Timossi
  LBNL, Berkeley, California

ALS, one of the first third generation synchrotron light sources which has been operating since 1992 at Berkeley Lab has been upgraded from its present operation scenario of injecting the 1.5GeV electron beam from the Booster ring into the Storage ring every 8 hours where it is accelerated to the final energy of 1.9GeV to full energy (1.9GeV) injection from the Booster ring into the Storage ring every 3 seconds for filling and every 30-35 seconds for Top-Off mode. Additionally the beam current has been increased from the time averaged value of 250mA to 500mA to increase the brightness. In this paper we will present the results of the new ALS injector RF system set-up for Top-Off mode of operation, the final design and operational results of the Booster RF power source and control system upgrades.

• S. P. Virostek
  
• M. D. Hoff, D. Li, J. W. Staples, R. P. Wells
  LBNL, Berkeley, California

A high-yield neutron source to screen sea-land cargo containers for shielded Special Nuclear Materials (SNM) has been designed at LBNL. The Accelerator-Driven Neutron Source (ADNS) utilizes the D(d,n)³He reaction to produce a forward directed neutron beam. Key components are a high-current radio-frequency quadrupole (RFQ) accelerator and a high-power neutron production target capable of delivering a neutron flux of >10⁷ n/(cm² s) at a distance of 2.5 m. The mechanical design and analysis of the four-module, bolt-together RFQ will be presented here. Operating at 200 MHz, the 5.1 m long RFQ will accelerate a 40 mA deuteron beam to 6 MeV. At a 5% duty factor, the time-average d+ beam current on target is 1.5 mA. Each of the 1.27 m long RFQ modules will consist of four solid OFHC copper vanes. A specially designed 3-D O-ring will be used to provide vacuum sealing between both the vanes and the modules. RF connections are made by means of canted coil spring contacts. Quadrupole mode stabilization is obtained with a series of 60 water-cooled pi-mode rods. A set of 80 evenly spaced fixed slug tuners is used for final frequency adjustment and local field perturbation correction.

• C. Chen
  
• J. Z. Zhou
  MIT/PSFC, Cambridge, Massachusetts

A concept for a high-power ribbon-beam klystron (RBK) employing a novel large-aspect ratio elliptic electron beam instead of a conventional circular electron beam is presented. Both cold-fluid and kinetic equilibrium theories are developed and applied in the design of the elliptic electron beam for the RBK. A small-signal theory is developed and applied in the design of the beam tunnel and the input, idler and output cavities. The electron gun and beam matching is being studied. Design results of a 10 MW 1.3 GHz RBK for the International Linear Collider (ILC) and of a 50 MW 22 GHz RBK for high-gradient research will be discussed.

• G. V. Eremeev
  
• H. Padamsee
  CLASSE, Ithaca

The heat treatment of a niobium cavity between 100 C - 120 C for 48 hours substantially improves cavity performance, presumably by healing the nature of the oxide-metal interface, although the nature of the healing is not yet understood. The heat treatment at higher temperatures is found to deteriorate the performance. Our tests on 1500 MHz single cell cavities are always equipped with a temperature mapping system consisting of 700 thermometers. The effect of heat treatment at various temperatures has been studied in detail using the temperature mapping system. In this contribution we report on several interesting findings from studies of a 400 C heat treatment.

• R. L. Geng
  
• G. V. Eremeev, H. Padamsee, V. D. Shemelin
  CLASSE, Ithaca

Based on the encouraging results of the first 1300 MHz 70 mm aperture single cell re-entrant cavities*, we continue the high gradient studies for ILC with new re-entrant cavities made of fine-grain as well as large-grain niobium. These new cavities have smaller aperture of 60 mm, providing a further reduced Hpk/Eacc or a further improved ultimate gradient. Four 1300 MHz 60 mm aperture re-entrant cavities are made, two out of fine grain niobium and the other two out of large-grain niobium. In addition, two elliptical shape 1500 MHz cavities are also made out of large-grain niobium. We present the testing results of these cavities.

* R. L. Geng et al., PAC2005, p.653.

• 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.

• J. R. Harris
  
• D. T. Blackfield, G. J. Caporaso, Y.-J. Chen, M. Sanders
  LLNL, Livermore, California
• M. L. Krogh
  University of Missouri - Rolla, Rolla, Missouri

As part of our ongoing development of the Dielectric Wall Accelerator, we are studying the performance of multilayer high-gradient insulators. These vacuum insulating structures are composed of thin, alternating layers of metal and dielectric, and have been shown to withstand higher gradients than conventional vacuum insulator materials. This paper describes these structures and presents some of our recent results.

• B. Rusnak
  
• C. Adolphsen, G. B. Bowden, L. Ge, R. K. Jobe, Z. Li, B. D. McKee, C. D. Nantista, J. Tice, F. Wang
  SLAC, Menlo Park, California
• R. Swent
  Stanford University, Stanford, Califormia

Fundamental power couplers for superconducting accelerator applications like the ILC are complicated RF transmission line assemblies due to their having to simultaneously accommodate demanding RF power, cryogenic, and cleanliness constraints. When these couplers are RF conditioned, the observed response is an aggregate of all the parts of the coupler and the specific features that dominate the conditioning response are unknown. To better understand and characterize RF conditioning phenomena toward improving performance and reducing conditioning time, a high-power coupler component test stand has been built at SLAC. Operating at 1.3 GHz, this test stand was designed to measure the conditioning behavior of select components of the TTFIII coupler independently, including outer-conductor bellows, diameter changes, copper plating and surface preparations, and cold window geometries and coatings. A description of the test stand, the measurement approach, and a summary of the results obtained are presented.

• K. Nielsen
  
• J. Barraza, M. Kang
  LANL, Los Alamos, New Mexico
• F. M. Bieniosek, K. Chow, W. M. Fawley, E. Henestroza, L. R. Reginato, W. L. Waldron
  LBNL, Berkeley, California
• R. J. Briggs, B. A. Prichard
  SAIC, Alamo, California
• T. E. Genoni, T. P. Hughes
  Voss Scientific, Albuquerque, New Mexico

• E. I. Smirnova
  
• B. E. Carlsten, L. M. Earley, W. B. Haynes
  LANL, Los Alamos, New Mexico

We propose to use the photonic band gap (PBG) structures for the construction of a traveling-wave tube (TWT) at W-band. Interest in millimeter-waves has increased in recent years due to applications in environmental monitoring and remote sensing. The development of wide-band mm-wave TWT amplifiers is underway at Los Alamos National Laboratory. A TWT would present a wide bandwidth source for remote mm-wave spectroscopy. PBG TWT structures have great potential for very large bandwidth and linear dispersion. In addition, being cheap to fabricate, the PBG structures enhance the commercial transferability of the W-band TWT technology. We employ an omniguide which is a one-dimensional version of the PBG structure representing a periodic system of concentric dielectric tubes as a slow-wave structure. A silica omniguide was designed to support a TM01-like mode with a phase velocity matching the one of a 120keV electron beam. The structure was fabricated, cold-tested and installed at our laboratory for the hot test.

• T. Tajima
  
• M. J. Borden, A. Canabal, T. A. Harden, P. C. Pittman
  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.

• V. A. Dolgashev
  
• Y. Higashi, T. Higo
  KEK, Ibaraki
• C. D. Nantista, S. G. Tantawi
  SLAC, Menlo Park, California

We report results of the first high power tests of single-cell traveling-wave and standing-wave accelerating structures. These tests are part of an experimental and theoretical study of RF breakdown in normal conducting structures at 11.4 GHz*. The goal of this study is to determine the gradient potential of normal conducting, RF powered particle beam accelerators. The test setup consists of reusable mode converters and short test structures powered by SLAC?s XL-4 klystron. This setup was created for economic testing of different cell geometries, cell materials and preparation techniques with short turn-around time. The mode launchers and structures were manufactured at SLAC and KEK and tested in the klystron test laboratory at SLAC.

* V. A. Dolgashev et al., "RF Breakdown In Normal Conducting Single-Cell Structures," SLAC-PUB-11707, Particle Accelerator Conference (PAC 05), Knoxville, Tennessee, 16-20 May 2005, pp. 595- 599.

• 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.

• 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.

• J. L. Hirshfield, J. L. Hirshfield, E. V. Kozyrev, M. A. LaPointe
  Yale University, Physics Department, New Haven, CT
• S. V. Shchelkunov
  Columbia University, New York
• M. Y. Shmelyov
  IAP/RAS, Nizhny Novgorod
• V. P. Yakovlev
  Omega-P, Inc., New Haven, Connecticut

Development of a future multi-TeV warm collider demands new technological solutions and new accelerator structure materials. The Ka-Band test facility being put into operation at Yale University that centers on the Yale/Omega-P 34-GHz magnicon allows users to carry out high gradient experiments on RF breakdown, pulse fatigue, tests of new high power pulse manipulation systems, and RF components. The magnicon is now conditioned for a pulse width up to 1 μs, at an output power level high enough for basic studies of electric and magnetic RF field limits at surfaces of conductors and dielectrics. The high-power waveguide transmission system for the facility is assembled and ready for tests. It includes RF windows, phase shifters, 13 mm diameter TE 11 waveguides, mode converters, etc. Recently the assembled system has undergone conditioning in preparation for carrying out first "user" experiments.

• 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.

• P. Kneisel
  
• G. Ciovati, J. S. Sekutowicz
  Jefferson Lab, Newport News, Virginia
• A. Matheisen, W. Singer, X. Singer
  DESY, Hamburg

Several, partially successful attempts have been made to develop a superconducting connection between adjacent niobium cavities with the capability to carry up to 30 mT of the magnetic flux. Such a connection would be particularly of great benefit to layouts of long accelerators like ILC because it would shorten the distances between structures and therefore the total length of an accelerator with the associated cost reductions. In addition the superconducting connection would be ideal for a super-structure, two multi-cell cavities connected through a half wavelength long beam pipe providing the coupling. Two welded prototypes of super-structure have been successfully tested with the beam at DESY. The chemical treatment and water rinsing was rather complicated for these prototypes. We have engaged in a program to develop such a connection based on the Nb55Ti material. Several options are pursued such as e.g.a two-cell cavity is being used to explore the reachable magnetic flux for the TESLA like connection with a squeezed niobium gasket between the flanges. In this contribution we will report about the progress of our investigations.

• P. Kneisel
  
• R. Bundy, G. Ciovati, W. Clemens, D. Forehand, B. Golden, S. Manning, R. Manus, R. B. Overton, R. A. Rimmer, G. Slack, L. Turlington, H. Wang
  Jefferson Lab, Newport News, Virginia
• F. Marhauser
  JLAB, Newport News, Virginia

In a previous paper the cavity* design for an Ampere-class cryomodule was introduced. We have since fabricated a 1500 MHz version of a single cell cavity with waveguide couplers for HOM and fundamental power, attached to one end of the cavity, a 5-cell cavity made from large grain niobium without couplers and a complete 5-cell cavity from polycrystalline niobium featuring waveguide couplers on both ends. A 750 MHz single cell cavity without endgroups has also been manufactured to get some information about obtainable Q-values, gradients and multipacting behavior at lower frequency. This contribution reports on the various tests of these cavities.

* R. A.Rimmer et al.; EPAC 2006, paper MOPCH182

• 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.

• M. BastaniNejad
  
• M. Alsharo'a, P. M. Hanlet, R. P. Johnson, M. Kuchnir, D. J. Newsham
  Muons, Inc, Batavia
• C. M. Ankenbrandt, A. Moretti, M. Popovic, K. Yonehara
  Fermilab, Batavia, Illinois
• A. A. Elmustafa
  Old Dominion University, Norfolk, Virginia
• D. M. Kaplan
  Illinois Institute of Technology, Chicago, Illinois

Microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 800 MHz RF cavity experiments are used to investigate the mechanism of RF breakdown. The images show evidence for melting and boiling in small regions of ~10 micron diameter on tungsten, molybdenum, and beryllium electrode surfaces. In these experiments, the dense hydrogen gas in the cavity prevents electrons or ions from being accelerated to high enough energy to participate in the breakdown process so that the only important variables are the fields and the metallic surfaces. The distributions of breakdown remnants on the electrode surfaces are compared to the maximum surface gradient E predicted by an ANSYS model of the cavity. The surface local density of spark remnants, presumably the probability of breakdown, shows a power law dependence on the maximum gradient, with E¹⁰ for tungsten and molybdenum and E⁷ for beryllium. This is reminiscent of Fowler-Nordheim behavior of electron emission from a cold cathode, which is explained by the quantum-mechanical penetration of a barrier that is characterized by the work function of the metal.

• 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.

• 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.

• C.-J. Jing
  
• W. Gai, F. Gao, R. Konecny
  ANL, Argonne, Illinois
• A. Kanareykin
  Euclid TechLabs, LLC, Solon, Ohio
• S. Kazakov
  KEK, Ibaraki

• 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.

• 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

• Y. Suetsugu
  
• K. Shibata
  KEK, Ibaraki

• R. E. Laxdal
  

• E. C. Bonnema
  
• J. J. Sredniawski
  AES, Medford, NY

• K. Sennyu
  
• H. Hara, M. Matsuoka
  MHI, Kobe

• 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

• J. Yoshida
  
• K. Hara, K. Hosoyama, Y. Kojima, H. Nakai, K. Nakanishi
  KEK, Ibaraki
• T. Ichitani, S. Kaneda
  Taiyo Nippon Sanso Corporation, Kawasaki-city Kanagawa Pref.
• T. Kanekiyo
  Hitachi Technologies and Services Co., Ltd., Kandatsu, Tsuchiura
• M. Noguchi
  Mayekawa MFG. Co., Ltd., Moriya
• S. Sakuma, K. Suzuki
  Taiyo Nippon Sanso Higashikanto Corporation, Hitachi-shi, Ibaraki-Perf.

• S. P. Møller
  
• T. Andersen, F. Bødker, A. Baurichter, P. A. Elkiaer, C. E. Hansen, N. Hauge, T. Holst, I. Jensen, L. K. Kruse, S. M. Madsen, M. Sager, S. V. Weber
  Danfysik A/S, Jyllinge
• K. Blasche
  BTE Heidelberg, Ingeniurburo, Schriesheim
• B. Franczak
  GSI, Darmstadt

• R. Nathawat
  
• A. K. Kumar, Y. K. Vijay
  UOR, Jaipur

Atomic force microscopy (AFM) study of low energy (10 keV) electron beam irradiated Polymethylmethacrylate (PMMA)20 micron thick surface was performed. PMMA film has been used in lithography applicatiion by this technique. AFM in tapping mode has been utilized to investigate the morphological changes on the samples surface as a function of fluence. TM-AFM showed the hills of the nano size surrounded by the craters type features in all the irradiated samples. The shape and size of these features varied with fluence. The root-mean-square (rms) surface roughness of the samples changed from 2.666 nm to 5.617 nm with fluence from 2x10¹⁴ electrons/cm² to 1x10¹⁶ electrons/cm². It shows that roughness increases as increasing fluence.

• L. Monaco
  
• J. W. Baehr, M. Krasilnikov, S. Lederer, F. Stephan
  DESY Zeuthen, Zeuthen
• J. H. Han, S. Schreiber
  DESY, Hamburg
• P. Michelato, C. Pagani, D. Sertore
  INFN/LASA, Segrate (MI)

The FLASH (DESY-Hamburg) and PITZ (DESY-Zeuthen) photoinjectors routinely use high quantum efficiency (QE) photocathodes produced at LASA (INFN-Milano), since 1998. To further understand the photocathode behavior during beam operation, photocathode QE measurements have been performed at different operating conditions in both RF photoinjectors. The analysis of these measurements will be used to improve the photocathode preparation procedures and to deeper understand the photocathode properties, whose final goal would be the further increase of their lifetime and beam quality preservation during the RF gun operations.

• 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.

• A. Sakumi
  
• Y. Muroya, T. Ueda, M. Uesaka
  The University of Tokyo, Nuclear Professional School, Ibaraki-ken

• Y. Kamiya
  
• Y. Kato, A. Murata, K. Sakaue, M. Washio
  RISE, Tokyo
• N. Kudoh, M. Kuriki, T. T. Takatomi, N. Terunuma, J. Urakawa
  KEK, Ibaraki
• R. Kuroda
  AIST, Tsukuba, Ibaraki

• G. Feng
  
• Y. Hong, Y. J. Pei, X. Wang
  USTC/NSRL, Hefei, Anhui

• A. Ferrari
  

Strong beam-beam effects at the interaction point of a high-energy e⁺e^- linear collider such as CLIC lead to an emittance growth for the outgoing beams, as well as to the production of beamstrahlung photons and e⁺e^- coherent pairs. We present a conceptual design of the post-collision line for CLIC at 3 TeV, which separates the various components of the outgoing beam in a vertical magnetic chicane and then transports them to their respective dump.

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

An undulator based positron source is a baseline for the International Linear Collider (ILC). The HeliCal collaboration in the UK is working on the development of a full scale 4-m long undulator module. Several prototypes have been built and tested in the R&D phase of the programme that culminated in the development of manufacturing techniques suitable for construction of the first full scale undulator sections. This paper details the design and the construction status of 4-m long undulator module.

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

An undulator based positron source is a baseline for the International Linear Collider (ILC). The HeliCal collaboration in the UK is carrying out an R&D programme on a short period supercoducting helical undulator with the goal to develop manufacturing technique as well as modelling and measurement techniques. Several undulator prototypes have been built and successfully tested. This paper summarizes the results of the R&D phase of the project.

• J.-L. Fernandez-Hernando
  
• G. A. Blair, S. T. Boogert
  Royal Holloway, University of London, Surrey
• G. Ellwood, R. J.S. Greenhalgh
  STFC/RAL, Chilton, Didcot, Oxon
• L. Keller
  SLAC, Menlo Park, California
• N. K. Watson
  Birmingham University, Birmingham

• 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.

• M. Church
  
• A. Z. Chen, N. V. Mokhov, S. Nagaitsev, N. Nakao
  Fermilab, Batavia, Illinois

• K. Yonehara
  
• R. J. Abrams, M. A.C. Cummings, R. P. Johnson, S. A. Kahn, T. J. Roberts
  Muons, Inc, Batavia
• D. R. Broemmelsiek, M. Hu, A. Jansson, V. D. Shiltsev
  Fermilab, Batavia, Illinois

MANX is an experiment to prove that effective six-dimensional (6D) muon beam cooling can be achieved a Helical Cooling Channel (HCC) using ionization-cooling with helical and solenoidal magnets in a novel configuration. The aim is to demonstrate that 6D muon beam cooling is understood well enough to plan intense neutrino factories and high-luminosity muon colliders. The experiment consists of the HCC magnets that envelop a liquid helium energy absorber, upstream and downstream instrumentation to measure the particle or beam parameters before and after cooling, and emittance matching sections between the detectors and the HCC. We describe and compare the experimental configuration for both single particle and beam profile measurement techniques based on G4Beamline simulations.

• M. Venturini
  
• M. A. Furman, J.-L. Vay
  LBNL, Berkeley, California
• M. T.F. Pivi
  SLAC, Menlo Park, California

Electron cloud build-up and related beam instabilities are a serious concern for the positron damping ring of the International Linear Collider (ILC). To mitigate the effect use of grooved vacuum-chamber walls is being actively investigated in addition to more conventional techniques like surface coating, scrubbing, and/or conditioning. Experimental and simulation studies have characterized the effectiveness of the grooved surface by means of an effective secondary emission yield (SEY), which has been measured to be significantly lower than the SEY of a smooth surface of the same material. However, some inconsistencies of the results, and the need to model the experimental testing of the grooved surface concept in more detail, have motivated us to simulate the grooved surfaces directly. Specifically, we have augmented the code POSINST by adding the option to simulate the electron-cloud build-up in the presence of a grooved surface geometry. By computing the accumulated e-cloud density and comparing it with the same quantity computed for a smooth surface, we infer an effective SEY, and we thereby make contact with the effective SEY estimates obtained from previous studies.

• M. S. Zisman
  

An international experiment to demonstrate muon ionization cooling is scheduled for beam at Rutherford Appleton Laboratory in 2007. The experiment comprises one cell of the Study II cooling channel*, along with upstream and downstream detectors to identify individual muons and measure their initial and final 6D phase-space parameters to a precision of 0.1%. Magnetic design of the beam line and cooling channel are complete and portions are under construction. The experiment will be described, including hardware designs, fabrication status, and running plans. Phase 1 of the experiment will prepare the beam line and provide detector systems, including time-of-flight, Cherenkov, scintillating-fiber trackers and the spectrometer solenoids, and an electromagnetic calorimeter. The Phase 2 system will add the cooling channel components, including liquid-hydrogen absorbers embedded in superconducting focus solenoids, 201-MHz normal-conducting RF cavities, and their surrounding coupling coil solenoids. The MICE Collaboration goal is to complete the experiment by 2010; progress toward this goal will be indicated. The supporting R&D program and its present results will also be described.

*S. Ozaki, R. Palmer, M. Zisman, and J. Gallardo (eds.), "Feasibility Study II of a Muon-based Neutrino Source," BNL-52623, 2001; http://www.cap.bnl.gov/mumu/studyii/final_draft/The-Report.pdf.

• 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.

• M. A. Shapiro
  
• J. R. Sirigiri, R. J. Temkin
  MIT/PSFC, Cambridge, Massachusetts

We present the results of our recent research on 3D metal-wire lattices operating at microwave frequencies, with applications to advanced accelerator structures and radiation sources based on the Smith-Purcell effect. Bulk and surface electromagnetic waves supported by a diamond-like lattice are calculated using HFSS. The bulk modes are determined using primitive cell calculations. The surface mode is determined using the simulations of the stack of cells with the perfect-matching layer (PML) boundary.

• N. Vinogradov
  
• C. L. Bohn, P. Piot
  Northern Illinois University, DeKalb, Illinois
• J. W. Lewellen, J. Noonan
  ANL, Argonne, Illinois

• Y. Fukui
  
• D. B. Cline, A. A. Garren
  UCLA, Los Angeles, California
• H. G. Kirk
  BNL, Upton, Long Island, New York

• M. Zhou
  
• M. K. Berry, I. Blumenfeld, F.-J. Decker, M. J. Hogan, R. Ischebeck, R. H. Iverson, N. A. Kirby, R. Siemann, D. R. Walz
  SLAC, Menlo Park, California
• C. E. Clayton, C. Huang, C. Joshi, W. Lu, K. A. Marsh, W. B. Mori
  UCLA, Los Angeles, California
• T. C. Katsouleas, P. Muggli, E. Oz
  USC, Los Angeles, California

In the recent plasma wakefield accelerator experiments at SLAC, the energy of the particles in the tail of the 42 GeV electron beam were doubled in less than one meter [1]. Simulations suggest that the acceleration length was limited by a new phenomenon – beam head erosion in self-ionized plasmas. In vacuum, a particle beam expands transversely in a distance given by beta*. In the blowout regime of a plasma wakefield [2], the majority of the beam is focused by the ion channel, while the beam head slowly spreads since it takes a finite time for the ion channel to form. It is observed that in self-ionized plasmas, the head spreading is exacerbated compared to that in pre-ionized plasmas, causing the ionization front to move backward (erode). A simple theoretical model is used to estimate the upper limit of the erosion rate for a bi-gaussian beam by assuming free expansion of the beam head before the ionization front. Comparison with simulations suggests that half this maximum value can serve as an estimate for the erosion rate. Critical parameters to the erosion rate are discussed.

[1] I. Blumenfeld et al., Nature 445, 741(2007)[2] J. B. Rosenzweig et al., Phys. Rev. A 44, R6189 (1991)

• K. L.F. Bane
  
• A. Seryi
  SLAC, Menlo Park, California

The main linac of the International Linear Collider (ILC) accelerates short, high peak current bunches into the Beam Deliver System (BDS) on the way to the interaction point. In the BDS wakefields are excited by the resistance of the beam pipe walls and by beam pipe transitions that will tend to degrade the emittance of the beam bunches. In this report we calculate the effect on emittance of incoming jitter or drift, and of misalignments of the beam pipes with respect to the beam axis, both analytically and through multi-particle tracking. Finally, we discuss ways of ameliorating the wake effects in the BDS.

• R. J. Noble
  
• E. R. Colby, B. M. Cowan, C. M.S. Sears, R. Siemann, J. E. Spencer
  SLAC, Menlo Park, California

Photonic bandgap (PBG) fibers with hollow core defects have been suggested for use as laser driven accelerator structures. The modes of a periodic PBG fiber lie in a set of allowed bands. A fiber with a central vacuum defect can support so-called defect modes with frequencies in the bandgap and electromagnetic fields confined spatially near the central defect. A defect mode suitable for relativistic particle acceleration must have a longitudinal electric field in the central defect and a phase velocity near the speed of light (SOL). We explore the design of the defect geometry to support well-confined accelerating modes in such PBG fibers. The details of the surface boundary separating the defect from the surrounding matrix are found to be the critical ingredients for optimizing the accelerating mode properties. We give examples of improved accelerating modes in fiber geometries with modified defect surfaces.

• C. M.S. Sears
  
• R. L. Byer, T. Plettner
  Stanford University, Stanford, Califormia
• E. R. Colby, B. M. Cowan, R. Ischebeck, C. Mcguinness, R. J. Noble, R. Siemann, J. E. Spencer, D. R. Walz
  SLAC, Menlo Park, California

• J. M. Grames
  
• P. A. Adderley, J. Brittian, J. Clark, J. Hansknecht, D. Machie, M. Poelker, M. L. Stutzman, R. Suleiman, K. E.L. Surles-Law
  Jefferson Lab, Newport News, Virginia

A new 100 kV GaAs DC Load Lock Photogun has been constructed at Jefferson Laboratory, with improvements for photocathode preparation and for operation in a high voltage, ultra-high vacuum environment. Although difficult to gauge directly, we believe that the new gun design has better vacuum conditions compared to the previous gun design, as evidenced by longer photocathode lifetime, that is, the amount of charge extracted before the quantum efficiency of the photocathode drops by 1/e of the initial value via the ion back-bombardment mechanism. Photocathode lifetime measurements at DC beam intensity of up to 10 mA have been performed to benchmark operation of the new gun and for fundamental studies of the use of GaAs photocathodes at high average current*. These measurements demonstrate photocathode lifetime longer than one million Coulombs per square centimeter at a beam intensity higher than 1 mA. The photogun has been reconfigured with a high polarization strained superlattice photocathode (GaAs/GaAsP) and a mode-locked Ti:Sapphire laser operating near band-gap. Photocathode lifetime measurements at beam intensity greater than 1 mA are measured and presented for comparison.

"Further Measurements of Photocathode Operational Lifetime at Beam Intensity >1mA using the CEBAF 100 kV DC GaAs Photogun", J. Grames et al., Proc. of the 17th Inter. Spin Symposium, Japan (2006).

• F. W. Meyer
  
• M. R. Fogle, J. W. Hale
  ORNL, Oak Ridge, Tennessee

We report on the development and implementation of a new beam line floatable at up to -15 kV and injected by a 10 GHz CAPRICE ECR ion source at the ORNL Multicharged Ion Research Facility MIRF as part of a major facility upgrade project [1]. With the floating beamline operating at negative high voltage, and the ECR source at ground potential, intense dc beam deceleration into grounded experimental chambers to energies as low as a few eV/q is made possible. The primary application of these ion beams is to study fundamental collisional interactions [2] of multicharged ions with electrons, atoms, and surfaces. Design details of the floating beam line, including source extraction, deceleration optics and voltage isolation will be presented at the conference. The novel features of a LABVIEW-based supervisory control and data acquisition (SCADA) system developed for the floating beam line will be described as well.

[1]F. W. Meyer et al. "The ORNL MIRF Upgrade project," NIMB B242,71(2006).[2]F. W. Meyer,"ECR-Based Atomic Collisions Research at ORNL MIRF," in Trapping Highly Charged Ions: Fundamentals & Applications, Nova Sci. Pub., New York, 2000, pp. 117-164.

• C.-J. Jing
  
• S. H. Gold
  NRL, Washington, DC
• A. Kanareykin
  Euclid TechLabs, LLC, Solon, Ohio
• S. Kazakov
  KEK, Ibaraki
• R. Konecny, J. G. Power
  ANL, Argonne, Illinois

* C. Jing, W. Gai, J. Power, R. Konecny, S. Gold, W. Liu and A. Kinkead, IEEE, Trans. PS, vol.33 No.4, Aug. 2005, pp.1155-1160.

• C.-J. Jing
  
• V. A. Dolgashev, S. G. Tantawi
  SLAC, Menlo Park, California
• W. Gai, R. Konecny, J. G. Power, Z. M. Yusof
  ANL, Argonne, Illinois
• S. H. Gold
  NRL, Washington, DC
• A. K. Kinkead
  LET

• C.-J. Jing
  
• A. Kanareykin
  Euclid TechLabs, LLC, Solon, Ohio
• S. Kazakov
  KEK, Ibaraki

Due to the high magnetic field-induced surface currents on its conducting sleeve, a conventional single layer Dielectric-Loaded Accelerating (DLA) structure exhibits a relatively high RF loss. One possible way to solve this problem is to use multilayered DLA structures*. In these devices, the RF power attenuation is reduced by making use of the Bragg Fiber concept: the EM fields are well confined by multiple reflections from multiple dielectric layers. This paper presents the design of an X-band dual layer DLA structure as well as the results of bench tests of the device. We will also present results on the design, numerical modeling, and fabrication of structures for coupling RF into multilayer DLAs such as a novel TM03 mode launcher and a TM01-TM03 mode converter using dielectric-loaded corrugated waveguide.

* C. Jing, W. Liu, W. Gai, J. G. Power, and T. Wong, Nucl. Instr. Meth. Phy. Res. A 539 (2005) 445-454.

• A. Kanareykin
  
• M. E. Conde, W. Gai
  ANL, Argonne, Illinois
• R. Gat
  Coating Technology Solution, Inc., Somerville
• C.-J. Jing, P. Schoessow
  Euclid TechLabs, LLC, Solon, Ohio

In this talk, we present our recent developments on a high gradient diamond-based cylindrical dielectric loaded accelerator (DLA). The final goal of this research is to achieve a record accelerating gradient (~ 600 MV/m) in a demonstration of the structure at high power and with accelerated beam. We discuss here a new technology for the development of cylindrical diamond-based waveguides and the design, fabrication and high power testing of a cylindrical diamond-based DLA accelerating structure. The electrical and mechanical properties of diamond make it an ideal candidate material for use in dielectric accelerators: high RF breakdown level, extremely low dielectric losses and the highest thermoconductive coefficient available. Multipacting of the CVD diamond can be suppressed by diamond surface dehydrogenation. A plasma supported Chemical Vapor Deposition (CVD) technology to produce low loss high quality cylindrical diamond layers is presented. Special attention is devoted to the numerical optimization of the coupling section, where the surface magnetic and electric fields are minimized relative to the accelerating gradient and within known metal surface breakdown limits.

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

• T. Plettner
  
• R. L. Byer, P. P. Lu
  Stanford University, Stanford, Califormia

• R. Pakter
  
• Y. Levin, F. B. Rizzato
  IF-UFRGS, Porto Alegre

We start by analyzing the image effects of a cylindrical conducting pipe on a continuous beam with elliptical symmetry. In particular, we derive an exact expression for the self-field potential of the beam inside the pipe without using any sort of multipole expansion. By means of a variational method, the potential for beams with varying density profiles along an elliptical shape is used to search for equilibrium solutions for intense beams. For that, we assume a uniform focusing in the smooth-focusing approximation. A curious result is that the product of the rms sizes along the ellipsis semi-axis stays constant as the pipe radius is varied. Finally, we prove that despite the nonlinear forces imposed by the image charges of an arbitrary shape conducting pipe, intense beams in uniform focusing fields preserve a uniform density in the equilibrium.

• M. K. Craddock
  
• S. R. Koscielniak
  TRIUMF, Vancouver

• Y. H. Chin
  
• Y. Shobuda
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• K. Takata
  KEK, Ibaraki

• W. Bruns
  
• D. Schulte, F. Zimmermann
  CERN, Geneva

The electrostatic Particle in Cell code 'Faktor2' is extended to 3D, and is parallelised. Results for electron cloud buildup in end regions of damping ring dipoles for next generation linear colliders are presented.

• G. Bassi
  
• J. A. Ellison, K. A. Heinemann
  UNM, Albuquerque, New Mexico
• R. L. Warnock
  SLAC, Menlo Park, California

We report on the implementation of a self consistent particle code to study CSR effects on particle bunches traveling on arbitrary planar orbits. Shielding effects are modeled with parallel perfectly conducting plates. The "vertical" charge distribution is assumed to be stationary. The macroscopic Maxwell equations are solved in the lab frame while the equations of motion are integrated in the beam frame interaction picture where the dynamics is governed by the self fields alone. We study different methods to construct a smooth charge density from particles, e.g. gridless nonparametric curve estimation and charge deposition plus filtering. We present numerical results for bunch compressors. In particular, we study different initial distributions. The transverse initial distribution is Gaussian and we study different initial longitudinal distributions: Gaussian, parabolic and nonlinear chirp. A parallel version of the code has been implemented and this will speed up parameter analysis and allow micro-bunching studies.

• M. Min
  
• Y.-C. Chae, P. F. Fischer, K.-J. Kim
  ANL, Argonne, Illinois
• Y. H. Chin
  KEK, Ibaraki

• E. Gianfelice-Wendt
  
• Y. Alexahin
  Fermilab, Batavia, Illinois

The Main Injector (MI) is a rapid cycling multipurpose accelerator. After completion of the Tevatron Run II, its primary application will be the acceleration of high intensity proton beams for neutrino experiments. To achieve the intensity goal a detailed knowledge of the optics and transverse impedances is necessary which can be obtained from Turn-By-Turn (TBT) beam position measurements. The recent MI Beam Position Monitor system upgrade made it possible to apply the TBT data analysis methods which were successfully used by the authors for the Tevatron. We present the results of MI optics measurements and the impedance estimates obtained from the betatron phase advance dependence on beam current.

• X. Zhang
  
• A. Z. Chen, W. Chou, B. M. Hanna, K. Y. Ng, J.-F. Ostiguy, L. Valerio, R. M. Zwaska
  Fermilab, Batavia, Illinois

Estimates indicate that the electron cloud effect could be a limiting factor for Main Injector intensity upgrades, with or without a the presence of a new 8 GeV superconducting 8GeV Linac injector. The effect may turn out to be an issue of operational relevance for other parts of the Fermilab accelerator complex as well. To improve our understanding of the situation, two sections of specially made vacuum test pipe outfitted for electron cloud detection with ANL provided Retarding Field Analyzers (RFAs), were installed in the Tevatron and the Main Injector. In this report we present some measurements, compare them with simulations and discuss future plans for studies.

• X. Zhang
  
• J.-F. Ostiguy
  Fermilab, Batavia, Illinois

To assess the effects of the electron cloud on Main Injector intensity upgrades, simulations of the cloud buildup were carried out using POSINST and compared with ECLOUD. Results indicate that even assuming an optimistic 1.3 maximum secondary electron yield, the electron cloud remains a serious concern for the planned future operational of mode of 500 bunches, 3·10¹¹ proton per bunch. Electron cloud buildup can be mitigated in various ways. We consider a plausible scenario involving solenoids in straight section and a single clearing strip electrode (like SNEG in Tevatron)held at a potential of 500V. Simulations with parameters corresponding to Tevatron and Main Injector operating conditions at locations where special electron cloud detectors have been installed have been carried out and are in satisfactory agreement with preliminary measurements.

• Y. Sato
  
• J. A. Holmes
  ORNL, Oak Ridge, Tennessee
• S.-Y. Lee
  IUCF, Bloomington, Indiana
• R. J. Macek
  LANL, Los Alamos, New Mexico

We present ORBIT code simulations to examine the sensitivity of electron cloud properties to different proton beam profiles and to reproduce experimental results from the proton storage ring at Los Alamos National Laboratory. We study the recovery of electron clouds after sweeping, and also the characteristics of two types of electrons signals (prompt and swept) as functions of beam charge. The prompt signal means the peak height of electron sweeper signal before high voltage pulse applied on its electrode and after beam accumulation, and the swept signal means the spike height of electron sweeper signal during the high voltage pulse. To concentrate on the electron cloud dynamics, we use a cold proton bunch to generate primary electrons and electromagnetic field for electron dynamics. However, the protons receive no feedback from the electron cloud. Our simulations indicate that the proton loss rate in the field-free straight section might be an exponential function of proton beam charge and may also be lower than the averaged proton loss rate in a whole ring.

• T. W. Koeth
  
• L. Bellantoni, D. A. Edwards, H. Edwards, R. P. Fliller
  Fermilab, Batavia, Illinois

An experiment is being constructed at Fermilab's A0 Photoinjector to exchange longitudinal and transverse beam emittances. The exchange is preformed by an optics channel consisting of two dogleg bend sections with a transverse deflecting mode cavity between them. In this paper we discuss the construction of the TM110 Mode Cavity. The cavity, based on a superconducting design will be constructed of copper. In addition, the cavity will be cooled with liquid nitrogen to fit within power and mode spacing requirements. The TM110 cavity operating requirements are presented as will the detail of the design, construction, tuning, and commissioning of the TM110 cavity.

• E. Pozdeyev
  
• I. Ben-Zvi, A. V. Fedotov, D. Kayran, V. Litvinenko, G. Wang
  BNL, Upton, Long Island, New York

Electron cooling at RHIC-II upgrade imposes strict requirements on the quality of the electron beam at the cooling section. Beam current dependent effects such as the space charge, wake fields, CSR in bending magnets, trapped ions, etc., will tend to spoil the beam quality and decrease the cooling efficiency. In this paper, we estimate the defocusing effect of the space charge at the cooling section and describe our plan to compensate the defocusing space charge force by focusing solenoids. We also estimate the energy spread and emittance growth cased by wake fields. Finally, we discuss ion trapping in the electron cooler and consider different techniques to minimize the effect of ion trapping.

• M. Poelker
  
• P. A. Adderley, J. Brittian, J. Clark, J. M. Grames, J. Hansknecht, J. McCarter, M. L. Stutzman, R. Suleiman, K. E.L. Surles-Law
  Jefferson Lab, Newport News, Virginia

• B. Brajuskovic
  
• J. T. Collins, P. K. Den Hartog, L. H. Morrison, G. J. Waldschmidt
  ANL, Argonne, Illinois

A normal-conducting deflecting cavity is being designed at the Advanced Photon Source (APS) as a part of the short x-ray pulse project intended to provide users with approximately 2 picosecond x-rays. The system will use two pairs of 3-cell cavities in sectors 6ID and 7ID for the generation of the x-ray pulse in the 7ID beamline. The 3-cell cavities are designed to provide the desired beam deflection while absorbing in excess of 4 kW of power from a pulsed rf system and up to 2.6 kW in the damper system of high-order mode (HOM) and low-order mode (LOM) waveguides. Since the cavity frequency is very sensitive to thermal expansion, the cooling water system is designed so that it is able to control cavity temperature to within 0.1?C. This paper describes the optimization of the thermomechanical design of the cavity based on calculation of thermal stresses and displacement caused by the generated heat loads, and presents the design of a cooling water system required for the proper operation of the cavities.

• S. R. Marques
  
• O. R. Bagnato, R. H.A. Farias, M. J. Ferreira, J. B. Gonzalez, C. Rodrigues, P. F. Tavares
  LNLS, Campinas

• A. Paech
  
• W. Ackermann, T. Weiland
  TEMF, Darmstadt
• O. Grimm
  DESY, Hamburg

One method to measure the bunch shape at the FLASH facility at DESY, Hamburg is based on the observation of synchrotron radiation generated at the first bunch compressor. For the correct interpretation of the results it is mandatory to know how various parameters of the real setup, in contrast to theoretical assumptions, influence the observed spectrum. The aim of this work therefore is to calculate the generation of synchrotron radiation of a moving point charge inside the bunch compressor with the emphasis of including the effects of the vertical and horizontal vacuum chamber walls in the vicinity of the last dipole magnet. Because of the small wavelength in comparison with the chamber geometries this is a demanding task. One idea to cope with the difficulties is to use optical methods such as the uniform theory of diffraction (UTD). In this paper the applicability and limitations of the proposed method are discussed. Furthermore a comparison of simulated and new measured fields is shown.

• E. Arevalo
  
• W. Ackermann, R. Hampel, W. F.O. Muller, T. Weiland
  TEMF, Darmstadt

The computation of wake fields excited by ultra short electron bunches in accelerator components with geometrical discontinuities is a challenging problem, as an accurate resolution for both the small bunch and the large model geometry are needed. Several computational codes (PBCI, ROCOCO, CST PARTICLE STUDIO etc.) have been developed to deal with this type of problems. Wake field simulations of the RF electron gun of the Photoinjector Test Facility at DESY Zeuthen (PITZ) are performed whith different specialized codes. Here we present a comparison of the wake potentials calculated numerically obtained from the different codes. Several structures of the photoinjector are considered.

• R. Wanzenberg
  
• K. Balewski
  DESY, Hamburg
• E. Gjonaj, T. Weiland
  TEMF, Darmstadt

• P. Craievich
  
• C. Bontoiu, G. Ciani, M. Ferianis
  ELETTRA, Basovizza, Trieste

• G. Penco
  
• C. Bontoiu, P. Craievich, V. Forchi', E. Karantzoulis
  ELETTRA, Basovizza, Trieste

• F. Marcellini
  

• K. R. Kim
  
• Y.-S. Cho, I.-S. Hong, H. S. Kim, B.-S. Park, S. P. Yun
  KAERI, Daejon
• H. J. Kim, J. H. So
  Kyungpook National University, Daegu

The test beam line was installed at the MC-50 cyclotron of KIRAMS (Korea Institute of Radiological And Medical Sciences). It has been supporting many pilot and feasibility studies on the development of beam utilization technologies of PEFP (Proton Engineering Frontier Project). The energy measurement with high accuracy is very important for the some experiments such as radiation hardness test of semiconductor devices, nuclear physics, detector test, etc. SSB and Si(Li) detector was used as del-E and E detector and the thickness of detectors are 2mm and 5mm each. The available energy range is 10MeV~39MeV and the flux was controlled not to be exceed 1·10⁺⁰⁵/cm²-sec using a 0.5mm diameter collimator.

• B. Dehning
  
• E. Effinger, J. E. Emery, G. Ferioli, G. Guaglio, E. B. Holzer, D. K. Kramer, L. Ponce, V. Prieto, M. Stockner, C. Zamantzas
  CERN, Geneva

• E. Metral
  
• B. Salvant
  EPFL, Lausanne
• B. Zotter
  Honorary CERN Staff Member, Grand-Saconnex

• F. Zimmermann
  

• P. J. Chou
  
• H.-P. Chang, K. T. Hsu, K. H. Hu, C.-C. Kuo, G.-H. Luo, M.-H. Wang
  NSRRC, Hsinchu

• G. Bassi
  
• J. A. Ellison, K. A. Heinemann
  UNM, Albuquerque, New Mexico

We discuss the longitudinal dynamics of an unbunched beam with a collective effect due to the vacuum chamber and with the discretness of an N-particle beam (Schottky noise) included. We start with the 2N equations of motion (in angle and energy) with random initial conditions. The 2D phase space density for the N-Particles is a sum of delta functions and satisfies the Klimontovich equation. An arbitrary function of the energy also satisfies the Klimontovich equation and we linearize about a convenient equilibrium density taking the initial conditions to be independent, identically distributed random vaiables with the equilibrium distribution. The linearized equations can be solved using a Laplace transform in time and a Fourier series in angle. The resultant stochastic process for the phase space density is analyzed and compared with a known result*. Work is in progress to study the full nonlinear problem. To gain further insight we are studying three alternative approaches: (1) a BBGKY approach, (2) an approach due to Elskens and Escande** and (3) the 'three-level-approach' of Donsker and Varadhan (see "Entropy, Large Deviations and Statistical Mechanics'', by R. S. Ellis).

* V. V. Parkhomchuk and D. V. Pestrikov, Sov. Phys. Tech. Phys. 25(7), July 1980 ** "Microscopic Dynamics of Plasmas and Chaos", Y. Elskens and D. Escande, IoP, Series in Plasma Physics, 2003.

• J. L. Bailey
  
• D. Capatina, J. W. Morgan
  ANL, Argonne, Illinois
• H.-D. Nuhn
  SLAC, Menlo Park, California

The Linac Coherent Light Source (LCLS), currently under design, requires accurate alignment between the electron beam and the undulator magnetic centerline. A Beam Finder Wire (BFW) instrument has been developed to provide beam location information that is used to move the undulators to their appropriate positions. A BFW instrument is mounted at each of the 33 magnets in the undulator section. Beam detection is achieved by electrons impacting two carbon fiber wires and then sensing the downstream radiation. The wires are mounted vertically and horizontally on a wire card similar to that of a traditional wire scanner instrument. The development of the BFW presents several design challenges due to the need for high accuracy of the wires' location and the need for removal of the wires during actual operation of the LCLS (30 microns repeatability is required for the wire locations). In this paper, we present the technical specification, design criteria, mechanical design, and results from prototype tests for the BFW.

• K. C. Harkay
  
• Y.-C. Chae, L. Emery, L. H. Morrison, A. Nassiri, G. J. Waldschmidt
  ANL, Argonne, Illinois

The Advanced Photon Source storage ring is normally operated with 100 mA of beam current. A number of high-current studies were carried out to determine the multibunch instability limits. The longitudinal multibunch instability is dominated by the rf cavity higher-order modes (HOMs), and the coupled-bunch instability (CBI) threshold is bunch-pattern dependent. We can stably store 200 mA with 324 bunches, and the CBI threshold is 245 mA. With 24 bunches, several components are approaching temperature limits above 160 mA, including the HOM dampers. We do not see any CBI at this current. The transverse multibunch instabilities are most likely driven by the resistive wall impedance; there is little evidence that the dipole HOMs contribute. Presently, we rely on the chromaticity to stabilize the transverse multibunch instabilities. When we stored beam up to 245 mA, we used high chromaticity, and the beam was transversely stable. The stabilizing chromaticity was studied as a function of current. We can use these experimental results to predict multibunch instability thresholds for various upgrade options, such as smaller-gap or longer ID chambers and the associated increased impedance.

• K. C. Harkay
  
• V. Sajaev, B. X. Yang
  ANL, Argonne, Illinois

The horizontal bursting instability was first observed in a single bunch in the APS in 1998, soon after operation began. Above the instability threshold, the bursting is characterized by exponentially growing bunch centroid oscillations that saturate, then decay, repeating quasi-periodically. More recently, bursting was also observed with multiple bunches in both the horizontal and vertical planes, showing that this is not purely a single-bunch phenomenon. On the other hand, the multibunch instability threshold is strongly dependent on bunch spacing, and the dependence is markedly different for the two transverse planes. Depending on the bunch spacing, the bunch-to-bunch oscillations are sometimes coupled, sometimes not. In this paper, we discuss the threshold in terms of the chromaticity required to stabilize the beam. We present instability imaging data using a streak camera that shows the bunch-to-bunch oscillation phase, and turn-by-turn beam position histories that give the bursting time dependence for different bunch spacings. Finally, we discuss the machine impedance and measured tune shift with current.

• S. De Santis
  
• J. M. Byrd
  LBNL, Berkeley, California
• M. T.F. Pivi
  SLAC, Menlo Park, California

We present the results of measurements of the electron cloud intensity in the PEP-II low energy ring (LER) by propagating a TE wave into the beam pipe. Connecting a pulse generator to a beam position monitor button we can excite a signal above the vacuum chamber cut-off and measure its propagation with a spectrum analyzer connected to another button a few meters away. The measurement can be performed with different beam conditions and also at different settings of the solenoids used to reduce the build up of electrons. The presence of a modulation in the TE wave transmission, synchronous with the beam revolution frequency and only measurable with the solenoids off, would be directly correlated to the intensity of the electron cloud phenomenon in the relative region of the ring. In this paper we present and discuss our measurements taken near Interaction Region 12 on the LER, during 2006 and early 2007.

• J. F. O'Hara
  
• M. J. Borden, A. A. Browman, N. A. Gillespie, D. Martinez, K. G. McKeown, F. R. Olivas
  LANL, Los Alamos, New Mexico
• J. E. Ledford, R. J. Macek
  TechSource, Santa Fe, New Mexico

In order to better understand the two stream e-p instability issue in the LANSCE Proton Storage Ring, a new diagnostic instrument has been developed to measure the electron cloud formation and trapping in a quadrupole magnet at the LANSCE, PSR. The device called the Electron Cloud Detector (ECD) was fabricated and has successfully been installed in the PSR. Along with the Electron Cloud Detector, an additional device was developed to manipulate electrons ejected from the quadrupole and allow additional information to be obtained from ECD measurements. This paper will discuss the mechanical design and fabrication issues encountered during the course of developing both devices.

• J. F. O'Hara
  
• M. J. Borden, D. C. Bruhn, J. L. Erickson, J. D. Gilpatrick, S. S. Kurennoy
  LANL, Los Alamos, New Mexico

A prototype Beam Position and Phase Monitor (BPPM) beam line device is being designed to go in the LANSCE 805-MHz linac. The concept is to install two beam line devices in locations where their measurements can be compared with older existing Delta-T loop and wire scanner measurements. The plan is to install two devices so that transverse position, angular trajectory, as well as central beam phase and energy will be measured. The mechanical design will combine features from previous LANL designs that were done for the LANSCE Isotope Production Facility, LANSCE Switchyard project, and those done for the SNS linac. This paper will discuss the mechanical design and fabrication issues encountered during the course of developing the BPPM.

• W. D. Zacherl
  
• I. Blumenfeld, M. J. Hogan, R. Ischebeck
  SLAC, Menlo Park, California
• C. E. Clayton, P. Muggli, M. Zhou
  UCLA, Los Angeles, California

A typical diagnostic used to determine the bunch length of ultra-short electron bunches is the autocorrelation of coherent transition radiation. This technique can produce artificially short bunch length results due to the attenuation of low frequency radiation if corrections for the material properties of the Michelson interferometer and detector response are not made. Measurements were taken using FTIR spectroscopy to determine the absorption spectrum of various materials and the response of a Molectron P1-45 pyroelectric detector. The material absorption data will be presented and limitations on the detector calibration discussed.

• A. Novokhatski
  
• J. Seeman, M. K. Sullivan
  SLAC, Menlo Park, California

The PEP-II B-factory at SLAC has recently experienced unexpected aborts due to anomalously high radiation levels at the BaBar detector. Before the problem was finally traced we performed the wake field analysis of the Q-2 bellows, which is situated at a distance of 2.2 m from the interaction point. Analysis showed that electric field in a small gap between a ceramic tile and metal flange can be high enough to produce sparks or even breakdowns. Later the traces of sparks were found in this bellows.

• A. Novokhatski
  
• S. A. Heifets, D. Teytelman
  SLAC, Menlo Park, California

Wake fields defining beam stability affect also the beam optics and beam properties in high current machines. We present observations and analysis of the optical effects in the PEP-II SLAC B-factory, which has the record in achievement of high electron and positron currents. We study the synchronous phase and the bunch length variation along the train of bunches, overall bunch lengthening and effects of the wakes on the tune and on the Twiss parameters. This analysis is being used in upgrades of PEP II and may be applied to future B-factories and damping rings for Linear Colliders.

• L. Wang
  
• A. Chao
  SLAC, Menlo Park, California
• J. Wei
  BNL, Upton, Long Island, New York

• R. L. Warnock
  

Realistic modeling of coherent synchrotron radiation (CSR) and the space charge force in single-pass systems and rings usually requires at least a two-dimensional (2-D) description of the charge/current density of the bunch. Since that leads to costly computations, one often resorts to a 1-D model of the bunch for first explorations. This paper provides several improvements to previous 1-D theories, eliminating unnecessary approximations and physical restrictions.

• J. Wu
  
• A. Chao
  SLAC, Menlo Park, California
• J. R. Delayen
  Jefferson Lab, Newport News, Virginia

For accelerator projects with ultra short electron beam, beam dynamics study has to invoke the short-range wakefield. In this paper, we first obtain the short-range dipole mode resistive wall wakefield. Analytical approach is then developed to study the single bunch transverse beam dynamics due to this short-range resistive wall wake. The results are applied to the LCLS undulator and some other proposed accelerators.

• A. Blednykh
  
• S. Krinsky
  BNL, Upton, Long Island, New York

• A. Blednykh
  
• S. Krinsky, J. Rose
  BNL, Upton, Long Island, New York

• A. Blednykh
  
• S. Krinsky
  BNL, Upton, Long Island, New York