• K. Oide
  
• T. Abe, K. Akai, M. Akemoto, A. Akiyama, A. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J. W. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, S. Hiramatsu, H. Hisamatsu, H. Honma, K. Hosoyama, T. Ieiri, N. Iida, H. Ikeda, M. Ikeda, S. Isagawa, H. Ishii, A. Kabe, E. Kadokura, T. Kageyama, K. Kakihara, E. Kako, S. Kamada, T. Kamitani, K.-I. Kanazawa, H. Katagiri, S. Kato, T. Kawamoto, S. Kazakov, M. Kikuchi, E. Kikutani, K. Kitagawa, H. Koiso, Y. Kojima, K. Komada, T. Kubo, K. Kudo, N. K. Kudo, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, S. Michizono, K. Mikawa, T. Mimashi, S. Mitsunobu, K. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T. T. Nakamura, H. Nakanishi, K. Nakao, S. Ninomiya, Y. Ogawa, K. Ohmi, Y. Ohnishi, S. Ohsawa, Y. Ohsawa, N. Ohuchi, M. Ono, T. Ozaki, K. Saito, H. Sakai, Y. Sakamoto, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, T. Sueno, M. Suetake, Y. Suetsugu, R. Sugahara, T. Sugimura, T. Suwada, O. Tajima, S. Takano, S. Takasaki, T. Takenaka, Y. Takeuchi, M. Tawada, M. Tejima, M. Tobiyama, N. Tokuda, S. Uehara, S. Uno, Y. Yamamoto, Y. Yano, K. Yokoyama, Ma. Yoshida, M. Yoshida, S. I. Yoshimoto, K. Yoshino
  KEK, Ibaraki
• E. Perevedentsev, D. N. Shatilov
  BINP SB RAS, Novosibirsk

Work presented on behalf of the KEKB Accelerator Group.

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

• M. Guinchard
  
• K. Artoos, A. Catinaccio, K. Kershaw, A. Onnela
  CERN, Geneva

• 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.

• J. C. Jan
  
• C.-H. Chang, J. W. Chen, T.-C. Fan, C.-S. Hwang, F.-Y. Lin
  NSRRC, Hsinchu

• 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. M. McIntyre
  
• A. D. McInturff, A. Sattarov
  Texas A&M University, College Station, Texas

The block coil geometry utilized in recent high-field dipole development has significant benefit for applications requiring rapid cycling, since it intrinsically suppresses coupling currents between strands. A conceptual design for a 6 Tesla dipole has been studied for such applications, in which the intra-strand losses are minimized by using bronze-process Nb3Sn superconducting wire developed for ITER. That conductor provides isolated fine filaments and optimum matrix resistance between filaments. The block-coil geometry further accommodates placement of He cooling channels inside the coil, so that heat from radiation and from AC losses can be removed with minimum temperature rise in the coil. The design could be operated with supercritical helium cooling, and should make it possible to operate with a continuous ramp rate of 5-10 T/s.

• S. S. Kurennoy
  

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

• M. Yeddulla
  
• S. G. Tantawi
  SLAC, Menlo Park, California

*S. G. Tantawi et al., Physical Review Special Topics – Accelerator and Beams. 8, 042002 (2005)

• A. Kanareykin
  
• A. Dedyk
  Eltech University, St. Petersburg
• E. Nenasheva
  Ceramics Ltd., St. Petersburg
• V. P. Yakovlev
  Omega-P, Inc., New Haven, Connecticut

We present recent results on development of a BST(M) ferroelectric composition synthesized for use in advanced technology components for X-band and Ka-band RF systems in high gradient accelerators and offer significant advantages for high power RF manipulation in the 300-1'000 MHz frequency range as well. These low loss ferroelectric materials can be used as key elements of both tuning and phase shifting components. We have identified BST ferroelectric-oxide compounds as suitable materials for a fast electrically-controlled 700 MHz, 50 kW tuner for ERL (BNL) and for high-power fast RF phase shifters to be used for SNS vector modulation applications. We have also developed large diameter (11 cm) BST(M)-based ferroelectric rings planned to be used at high average power (10 kW range) for L-band phase-shifters intended for the ILC. This phase shifter will allow coupling adjustment and control of the power consumption during the process of SC cavity filling.

• W. Zhang
  
• I. Marneris, J. Sandberg
  BNL, Upton, Long Island, New York

Large accelerator main magnet system consists of hundreds, even thousands, of dipole magnets. They are linked together under selected configurations to provide highly uniform dipole fields when powered. Distributed capacitance, insulation resistance, coil resistance, magnet inductance, and coupling inductance of upper and lower pancakes make each magnet a complex network. When all dipole magnets are chained together in a circle, they become a coupled pair of very high order complex ladder networks. In this study, a network of more than thousand inductive, capacitive or resistive elements are used to model an actual system. The circuit is a large scale network. Its equivalent polynomial form has several hundred degrees. Analysis of this high order circuit and simulation of the response of any or all components is often computationally infeasible. We present methods to use frequency decomposition approach to effectively simulate and analyze magnet configuration and power supply topologies.

• W. Zhang
  
• I. Marneris, J. Sandberg
  BNL, Upton, Long Island, New York

A main magnet chain forms a pair of transmission lines. Pulse-reflection-caused voltage and current differentiation throughout the magnet chain can have adverse effect on main magnet field quality. This effect is associated with magnet system configuration, coupling efficiency, and parasitic parameters. A better understanding of this phenomenon will help us in new design and existing system upgrade. In this paper, we exam the transmission line effect due to different input functions as well as configuration, coupling, and other parameters.

• D. O. McCarron
  
• J. F. Amundson, W. Pellico, P. Spentzouris, R. E. Tomlin
  Fermilab, Batavia, Illinois
• L. K. Spentzouris
  Illinois Institute of Technology, Chicago, Illinois

* Synergia: A 3D Accelerator Modelling Tool with 3D Space Charge. Journal of Computational Physics, Volume 211, Issue 1 , 1 January 2006, Pages 229-248.

• K.-J. Kim
  

• Y.-C. Chao
  

• B. Nash
  

• P. Cameron
  
• J. Cupolo, W. C. Dawson, C. Degen, A. Della Penna, L. T. Hoff, Y. Luo, A. Marusic, R. Schroeder, C. Schultheiss, S. Tepikian
  BNL, Upton, Long Island, New York
• M. Gasior
  CERN, Geneva

Tune feedback was first implemented in RHIC in 2002 as a specialist activity. The transition to full operational status was impeded by dynamic range problems, as well as by overall loop instabilities driven by large coupling. The dynamic range problem was solved by the CERN development of the Direct Diode Detection Analog Front End. Continuous measurement of all projections of the betatron Eigenmodes made possible the world's first implementation of coupling feedback during beam acceleration, resolving the problem of overall loop instabilites. Simultaneous tune and coupling feedbacks were utilized as specialist activities for ramp development during the 2006 RHIC run. At the beginning of the 2007 RHIC run there remained two obstacles to making these feedbacks fully operational in RHIC - chromaticity measurement and control, and the presence of strong harmonics of the power line frequency in the betatron spectrum. We report here on progress in tune, coupling, and chromaticity measurement and feedback, and discuss the relevance of our results to the LHC commissioning effort. The results of investigations of power line harmonics in RHIC are presented elsewhere in these proceedings.

• Z. Li
  
• V. Akcelik, A. E. Candel, L. Ge, A. C. Kabel, K. Ko, L. Lee, C.-K. Ng, E. E. Prudencio, G. L. Schussman, R. Uplenchwar, L. Xiao
  SLAC, Menlo Park, California

Under the support of the U. S. DOE SciDAC program, SLAC has been developing a suite of 3D parallel finite-element codes aimed at high-accuracy, high-fidelity electromagnetic and beam physics simulations for the design and optimization of next-generation particle accelerators. Running on the latest supercomputers, these codes have made great strides in advancing the state of the art in applied math and computer science at the petascale that enable the integrated modeling of electromagnetics, self-consistent Particle-In-Cell (PIC) particle dynamics as well as thermal, mechanical, and multi-physics effects. This paper will present 3D results of trapped mode calculations in an ILC cryomodule and the modeling of the ILC Sheet Beam klystron, shape determination of superconducting RF (SCRF) cavities and multipacting studies of SCRF HOM couplers, as well as 2D and preliminary 3D PIC simulation results of the LCLS RF gun.

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

• L. O. Dallin
  
• D. Bodnarchuk, T. Summers
  CLS, Saskatoon, Saskatchewan

• 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

• A. Nadji
  
• J. C. Besson, F. Bouvet, P. Brunelle, A. Buteau, L. Cassinari, M.-E. Couprie, J.-C. Denard, J.-M. Filhol, C. Herbeaux, J.-F. Lamarre, V. Le Roux, P. Lebasque, M.-P. Level, A. Loulergue, P. Marchand, L. S. Nadolski, R. Nagaoka, B. Pottin, M.-A. Tordeux
  SOLEIL, Gif-sur-Yvette

• T.-T. Yang
  
• C.-S. Fann, K. T. Hsu, S. Y. Hsu, J.-Y. Hwang, W. K. Lau, A. P. Lee, C. C. Liang, K.-K. Lin, K.-B. Liu, Y.-C. Liu, H. M. Shih, M.-S. Yeh
  NSRRC, Hsinchu

• I. P.S. Martin
  
• R. Bartolini, R. T. Fielder, E. C. Longhi, B. Singh
  Diamond, Oxfordshire

• R. J. Dejus
  
• I. Vasserman
  ANL, Argonne, Illinois

Two full-length 2.4-m-long undulators, with period lengths 2.3 cm and 2.7 cm, were recently installed in tandem in the 5.6-m-long straight on the storage ring in sector 14. One part of the user research program requires that both undulators be tuned to 12.0 keV and the x-ray intensity maximized. The total intensity is sensitive to the phasing between the undulators, so the distance between the devices must be optimized and the ends tuned appropriately. Because of the different period lengths, the gaps and K values of the undulators will be different: 10.6-mm gap and a K value of 1.17 for the shorter-period device and 15.7-mm gap and a K value of 0.93 for the longer-period device. A special shield was designed and installed between the devices to eliminate interference. Results of magnetic measurements, tuning, and computer simulations of the spectral performance are presented.

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

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

• C. Steier
  
• P. A. Heimann, S. Marks, D. Robin, R. W. Schoenlein, W. Wan
  LBNL, Berkeley, California
• W. Wittmer
  SLAC, Menlo Park, California

An upgraded femtosecond slicing facility has been commissioned successfully at the Advanced Light Source. In contrast to the original facility at the ALS which pioneered the concept, the new beamline uses an undulator (the first in-vacuum undulator at the ALS) as the radiator producing the user photon beam. To spatially separate the femtosecond slices in the radiator, a local vertical dispersion bump produced with 12 skew quadrupoles is used. The facility was successfully commissioned during the last 1.5 years and is now used in routine operation.

• S. F. Mikhailov
  
• S. M. Hartman, J. Li, V. Popov, Y. K. Wu
  FEL/Duke University, Durham, North Carolina

A booster synchrotron has been recently commissioned at Duke University FEL Laboratory as a part of the High Intensity Gamma-ray Source (HIGS) facility. The booster will provide top-off injection into the storage ring in the energy range of 0.27 - 1.2 GeV. In order to minimize the cost of the project, the booster is designed with a very compact footprint. As a result, unconventionally high field bending magnets at 1.76 T are required. A main ramping power supply drives all dipoles and quadrupoles. Quadrupole trims are used to compensate for tune changes caused by the change of relative focusing strength during ramping. Sextupoles compensate for chromatic effects caused by dipole magnet pole saturation. All these compensations have to be performed as a function of beam energy. Above 1.1 GeV, where the magnets are heavily saturated, the reduction of dynamic aperture is compensated by redistribution of strength among the sextupole families. With these compensations, effects of the magnet saturation do not cause any considerable beam loss during energy ramping.

• E. Hemsing
  
• G. Andonian, J. B. Rosenzweig
  UCLA, Los Angeles, California
• M. Babzien, V. Yakimenko
  BNL, Upton, Long Island, New York
• A. Gover
  University of Tel-Aviv, Faculty of Engineering, Tel-Aviv

• S. Reiche
  
• K. Goldammer
  BESSY GmbH, Berlin
• P. Musumeci
  Rome University La Sapienza, Roma

• D. Dowell
  
• E. N. Jongewaard, J. R. Lewandowski, Z. Li, C. Limborg-Deprey, J. F. Schmerge, A. E. Vlieks, J. W. Wang, L. Xiao
  SLAC, Menlo Park, California

The beam quality and operational requirements for the Linac Coherent Light Source (LCLS) currently being constructed at SLAC are exceptional, requiring the design of a new RF photocathode gun for the electron source. Based on operational experience at GTF at SLAC, SDL and ATF at BNL and other laboratories, the 1.6cell s-band (2856MHz) gun was chosen to be the best electron source for the LCLS injector, however a significant re-design was necessary to achieve the challenging parameters. Detailed 3-D analysis and design was used to produce nearly-perfect rotationally symmetric rf fields to achieve the emittance requirement. In addition, the thermo-mechanical design allows the gun to operate at 120Hz and a 140MV/m cathode field, or to an average power dissipation of 4kW. Both average and pulsed heating issues are addressed in the LCLS gun design. The first LCLS gun is now fabricated and has been operated with high-power RF. The results and analysis of these high-power tests will be presented.

• B. Podobedov
  
• L. Yang
  IUCF, Bloomington, Indiana

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

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

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

• C. Milardi
  
• D. Alesini, M. E. Biagini, C. Biscari, R. Boni, M. Boscolo, B. Buonomo, A. Clozza, G. O. Delle Monache, T. Demma, E. Di Pasquale, G. Di Pirro, A. Drago, A. Gallo, A. Ghigo, S. Guiducci, M. Incurvati, P. Iorio, C. Ligi, F. Marcellini, C. Marchetti, G. Mazzitelli, L. Pellegrino, M. A. Preger, L. Quintieri, P. Raimondi, R. Ricci, U. Rotundo, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A. Stecchi, A. Stella, S. Tomassini, C. Vaccarezza, M. Zobov
  INFN/LNF, Frascati (Roma)
• J. D. Fox, D. Teytelman
  SLAC, Menlo Park, California
• E. Levichev, S. A. Nikitin, P. A. Piminov, D. N. Shatilov
  BINP SB RAS, Novosibirsk

• N. Iida
  
• J. W. Flanagan, Y. Funakoshi, K. Oide
  KEK, Ibaraki

• 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

• Y. Wei
  

Due to the errors in all kinds of components of storage ring, the real ring optics is different from the design one. A computer code LOCO is developed to calibrate the linear optics based on the closed orbit response matrix. This paper discusses mainly on the procedure and results of optics correction at BEPCII BPR. Using LOCO, we have determined the errors of quadrupole strengths, BPM gains and corrector kicks, and found the quadrupole strengths that best restore the design optics with sextupoles on. Optics measurement after correction shows the real optics agrees well with the design optics.

weiyy@mail.ihep.ac.cn

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

• N. M. Gelfand
  

Measurements of the tune on the front porch of the Tevatron* showed a drift of the tune which tracked the time dependence of the sextupole moment in the dipoles. Calculations using survey data to calculate the closed orbit failed to reproduce the observed tune shifts. The feed down of these sextupole moments generates a quadrupole field at the ends of the dipoles. It is suggested, based on calculations, that the change in the sextupole moment of the dipoles also produces a change in the strength of the strength of the zero length quadrupole incorporated in the end of the dipoles and that this change can account for the observed tune drifts.

*Tevatron Chromaticity and Tune Drift and Snapshot Studies Report, G. Annala, P. Bauer, M. Martens, D. Still, G. Velev, Beams-doc-1236 (Jan. 5,2005)

• 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.

• R. Calaga
  
• K. Akai, K. Ohmi, K. Oide
  KEK, Ibaraki
• U. Dorda, R. Tomas, F. Zimmermann
  CERN, Geneva

A small angle (< 1mrad) crab scheme is an attractive option for the LHC luminosity upgrade to recover the geometric luminosity loss from the finite crossing angle, which steeply increases to unacceptable levels as the IP beta function is reduced below its nominal value. The crab compensation in the LHC can be accomplished using only two sets of deflecting rf cavities, placed in collision-free straight sections of LHC to nullify the crossing angles at IP1 & IP5. We present IR optics configurations with low-angle crab crossing, study the beam-beam performance and proton-beam emittance growth in the presence of crab compensation, lattice errors, crab RF noise sources. We also explore a 400MHz superconducting cavity design and discuss the pertinent RF challenges.

• W. Fischer
  
• M. Blaskiewicz, R. Calaga, P. Cameron, Y. Luo
  BNL, Upton, Long Island, New York
• T. Pieloni
  CERN, Geneva

We use transverse beam transfer functions to measure tune distributions of colliding beams in RHIC. The tune has a distribution due to the beam-beam interaction, nonlinear magnetic fields – particularly in the interaction region magnets, and non-zero chromaticity in conjunction with momentum spread. The measured tune distributions are compared with calculations.

• J. C. Smith
  

Polarized positron and electron beams are ideal for searching for new physics at the International Linear Collider (ILC). In order to properly orient and preserve the polarization of both beams at the Interaction Point (IP) the beam polarization must be manipulated by a series of spin rotators along the beam line. Furthermore, the polarization for both beams should be known with a relative uncertainty of about 0.5% or better, therefore, all sources of depolarization along the ILC should be identified. We report on a spin rotator design for the ILC and polarization studies between Damping Ring extraction and the Interaction Point.

• 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

• A. V. Burov
  
• V. A. Lebedev
  Fermilab, Batavia, Illinois

The more beam is cooled, the less stable it is. In the Recycler Ring, antiprotons are cooled both with stochastic and electron cooling. To stabilize it against the resistive wall instability, a digital damper is successfully used. Digital dampers can be described as linear operators with explicit time dependence, and that makes a principle difference with analogous dampers. Theoretical description of the digital dampers is presented. Electron cooling makes possible a two-beam instability of the cooled beam with the electron beam. Special features of this instability are described, and the remedy is discussed.

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

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

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

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

• S. Sakanaka
  

* S. Sakanaka, Phys. Rev. ST Accel. Beams 8, 072002 (2005).** E. A. Knapp, B. C. Knapp, and J. M. Potter, Rev. Sci. Instrum. 39, 979 (1968).

• C.-F. Wu
  
• S. Dong, X. D. He, H. Lin, L. Wang
  USTC/NSRL, Hefei, Anhui

Some model cavities have been further developed and investigated for a X-band (f=9.37GHz) hybrid dielectric-iris-loaded accelerating structure based on the calculated results about the effect of the dimension tolerance on the RF properties. The dispersion curve fitted by using the measurement value is consistent with the one calculated. The r/Q values of the dipole modes have been calculated by the Mafia code. The theoretical results show that the r/Q values of dipole modes for the new accelerating structure are lower than those for the iris-load accelerating structure.

• C.-F. Wu
  
• S. Dong, X. D. He, H. Lin
  USTC/NSRL, Hefei, Anhui

The coupler design for X-band hybrid dielectric-iris-loaded accelerator has been studied. Firstly, the S parameters versus the coupler cavity radius, the width and the height of the coupling hole have been simulated by Microwave Studio for the ordinary coupling cavity. We have obtained the primary measurement result of the standing-wave ratio of the coupling cavities being 1.8275. Secondly, the new couplers, which first converts RF from TE to TM mode in a pure metal section and then a tapered transition section is added for high efficiency transmission to the accelerator section, have been calculated for both single and dual coupling ports. The simulated results show that both types are capable to convert the TE 10 mode into TM 01 mode with high efficiency over a relatively wide bandwidth.

• 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

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

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

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

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

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

• P. Goudket
  
• C. D. Beard, P. A. McIntosh
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• G. Burt
  Cockcroft Institute, Lancaster University, Lancaster
• N. Chanlek, R. M. Jones
  UMAN, Manchester
• A. C. Dexter
  Cockcroft Institute, Warrington, Cheshire

In order to verify detailed impedance simulations, the modes in an aluminium model of the ILC crab cavity were investigated using a bead-pulling technique as well as a stretched-wire frequency domain measurement. The combination of these techniques allow for a comprehensive study of the modes of interest. For the wire measurement, a transverse alignment system was fabricated and rf components were carefully designed to minimize any potential impedance mismatches. The measurements are compared with direct simulations of the stretched-wire experiments using numerical electromagnetic field codes. High impedance modes of particular relevance to the ILC crab cavity are identified and characterized

• G. Burt
  
• C. D. Beard, P. Goudket, P. A. McIntosh
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• L. Bellantoni
  Fermilab, Batavia, Illinois
• R. G. Carter, A. C. Dexter, R. O. Jenkins
  Cockcroft Institute, Lancaster University, Lancaster

The ILC crab cavity will require the design of an appropriate power coupler. The beamloading in dipole cavities is considerably more variable than accelerating cavities, hence simulations have been performed to establish the required external Q. Simulations of a suitable coupler were then performed and were verified using a normal conducting prototype with variable coupler tips.

• 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.

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

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

• T. N. Khabiboulline
  
• I. G. Gonin, N. Solyak
  Fermilab, Batavia, Illinois

• J. Li
  
• N. Solyak
  Fermilab, Batavia, Illinois
• T. Wong
  Illinois Institute of Technology, Chicago, Illinois

Fermilab has developed a third harmonic superconducting cavity operating at the frequency of 3.9 GHz to improve the beam performance for the FLASH user facility at DESY. It is interesting to investigate the coupling interaction between the SRF cavity and the power coupler with or without beam loading. The coupling of the power coupler to the cavity needs to be determined to minimize the power consumption and guarantee the best performance for a given beam current. In this paper, we build and analyze an equivalent circuit model containing a series of lumped elements to represent the resonant system. An analytic solution of the required power from the generator as a function of the system parameters has also been given based on a vector diagram.

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

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

• V. D. Shemelin
  

The introduction of reentrant shape for superconducting cavities has made it possible to achieve record high gradients. In this paper it is shown that lowest losses in the cavities are also achievable employing the reentrant shape. Influence of the cavity wall slope angle on the extreme gradient and losses is analyzed.

• 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.

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

The Pulse-Line Ion Accelerator* (PLIA) is a helical distributed transmission line. A rising pulse applied to the upstream end appears as a moving spatial voltage ramp, on which an ion pulse can be accelerated. This is a promising approach to acceleration and longitudinal compression of an ion beam at high line charge density. In most of the studies carried out to date, using both a simple code for longitudinal beam dynamics and the Warp PIC code, a circuit model for the wave behavior was employed; in Warp, the helix I and V are source terms in elliptic equations for E and B. However, it appears possible to obtain improved fidelity using a "sheath helix" model in the quasi-static limit. Here we describe an algorithmic approach that may be used to effect such a solution.

*R. J. Briggs, PRST-AB 9, 060401 (2006).

• F. L. Krawczyk
  
• G. O. Bolme, W. L. Clark, J. P. Kelley, F. A. Martinez, D. C. Nguyen, K. A. Young
  LANL, Los Alamos, New Mexico
• J. Rathke, D. L. Schrage, T. Schultheiss, L. M. Young
  AES, Medford, NY

An experiment has been conducted to measure small differences in cavity Q caused by various cavity surface treatments. A requirement of the experiment was that it show little sensitivity to the reassembly with various test pieces. We chose a coaxial half-wave resonator, with an outer conductor extending significantly beyond the length of the inner conductor. The outer conductor acts as a cut-off tube, eliminating the need for electric termination and thus any RF-contacts that can influence the Q-measurements. The experiment is aimed at qualifying the performance of cyanide-copper plated GlidCop in comparison with that of a machined GlidCop surface. To maximize the sensitivity of the measurement we use a fixed outer conductor made of annealed OFE copper and only replace the inner conductor, which is mounted on a low-loss Teflon pedestal located in the low electric field region. The Q-values of machined GlidCop and cyanide-copper plated GlidCop inner conductors are measured against the reference Q of the annealed OFE co-axial cavity. This simple configuration allows a statistically significant number of repetitions of measurements and should provide accurate comparative measurements.

• 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.

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

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

• B. D. O'Shea
  
• D. Alesini, M. Ferrario, B. Spataro
  INFN/LNF, Frascati (Roma)
• A. Boni, A. Fukasawa, J. B. Rosenzweig
  UCLA, Los Angeles, California
• L. Ficcadenti, A. Mostacci, L. Palumbo
  Rome University La Sapienza, Roma

The hybrid photoinjector is a high current, low emittance photoinjector/accelerator and is under design and collaboration at Roma University La Sapienza, INFN - Laboratori Nazionali di Frascati and the UCLA Particle Beam Physics Lab. The hybrid standing wave-traveling wave photoinjector uses a coupling cell to divide power between a high-field 1.6 cell standing wave photoinjector, for electron emission and collection, and a low power traveling wave accelerator, for acceleration to desired energies at low emittances. Simulation results show promising beam properties of less than 4 mm-mrad emittance, energy spreads of 1.5%, and currents as high as 1.2 kA at energies of 21 MeV. We report on the progress of RF design and results of cold test RF measurements at the UCLA Pegasus Laboratory, including methods for measurements and difficulties arising in the transition from simulation to physical measurements.

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

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

• J. Guo
  
• S. G. Tantawi
  SLAC, Menlo Park, California

• Z. Li
  
• L. Ge, K. Ko, L. Lee, C.-K. Ng, G. L. Schussman, L. Xiao
  SLAC, Menlo Park, California
• T. Higo, Y. Morozumi, K. Saito
  KEK, Ibaraki
• P. Kneisel
  Jefferson Lab, Newport News, Virginia
• J. S. Sekutowicz
  DESY, Hamburg

The Low-Loss shape cavity design has been proposed as a possible alternative to the baseline TESLA cavity design for the ILC. The advantages of this design over the TESLA cavity are its lower cryogenic loss, and higher achievable gradient due to lower surface fields. High gradient prototypes for such designs have been tested at KEK (ICHIRO) and JLab (LL). However, issues related to HOM damping and multipacting (MP) still need to be addressed. Preliminary numerical studies of the prototype cavities have shown unacceptable damping for some higher-order dipole modes if the typical TESLA HOM couplers are directly adapted to the design. The resulting wakefield will dilute the beam emittance thus reduces the machine luminosity. Furthermore, high gradient tests on a 9-cell prototype at KEK have experienced MP barriers although a single LL cell had achieved a high gradient. From simulations, MP activities are found to occur in the end-groups of the cavity. In this paper, we will present the optimization results of the end-groups for the Low-Loss shape for effective HOM damping and alleviation of multipacting. Comparisons of simulation results with measurements will also be presented.

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

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

• L. Xiao
  
• C. Adolphsen, V. Akcelik, A. C. Kabel, K. Ko, L. Lee, Z. Li, C.-K. Ng
  SLAC, Menlo Park, California

The actual cell shape of the TESLA cavities differ from the ideal due to fabrication errors, the addition of stiffening rings and the frequency tuning process. Cavity imperfection shift the dipole mode frequencies and alter the Qext's from those computed for the idea cavity. A Qext increase could be problematic if its value exceeds the limit required for ILC beam stability. To study these effects, a cavity imperfection model was established using a mesh distortion method. The eigensolver Omega3P was then used to find the critical dimensions that contribute to the Qext spread and frequency shift by comparing predictions to TESLA cavity measurement data. Using the imperfection parameters obtained from these studies, artificial imperfection models were generated and the resulting wakefields were used as input to the beam tracking code Lucretia to study the effect on beam emittance. In this paper, we present the results of these studies and suggest tolerances for the cavity dimensions.

• L. Xiao
  
• L. Bellantoni
  Fermilab, Batavia, Illinois
• G. Burt
  Cockcroft Institute, Lancaster University, Lancaster
• P. Goudket, P. A. McIntosh
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• K. Ko, Z. Li, C.-K. Ng, G. L. Schussman, A. Seryi, R. Uplenchwar
  SLAC, Menlo Park, California

The FNAL 9-cell 3.9GHz deflecting cavity designed for the CKM experiment was chosen as the baseline design for the ILC BDS crab cavity. Effective damping is required for the lower-order TM01 modes (LOM), the same-order TM11 modes (SOM) as well as the HOM modes to minimize the beam loading and beam centroid steering due to wakefields. Simulation results of the original CKM design using the eigensolver Omega3P showed that both the notch filters of the HOM/LOM couplers are very sensitive to the notch gap, and the damping of the unwanted modes is suboptimal for the ILC. To meet the ILC requirements, the couplers were redesigned to improve the damping and tuning sensitivity. With the new design, the damping of the LOM/SOM/HOM modes is significantly improved, the sensitivity of the notch filter for the HOM coupler is reduced by one order of magnitude and appears mechanically feasible, and the LOM coupler is simplified by aligning it on the same plane as the SOM coupler and by eliminating the notch filter. In this paper, we will present the coupler optimization and tolerance studies for the crab cavity.

• S. V. Kuzikov
  
• J. L. Hirshfield, V. P. Yakovlev
  Omega-P, Inc., New Haven, Connecticut
• M. E. Plotkin, D. Yu. Shegolkov, A. A. Vikharev
  IAP/RAS, Nizhny Novgorod

Basic studies of factors that limit RF fields in warm accelerator structures require experiments at RF power that can be produced using pulse compression. This approach is being implemented to compress output pulses from the Yale/Omega-P 34-GHz magnicon to produce ~100-200 MW, 100 ns pulses. A new approach for passive pulse compression is a SLED-II type circuit operating with axisymmetrical modes of the TE0n type that requires only a single channel instead of the usual double channel scheme. This allows avoidance of a 3-dB coupler and need for simultaneous fine tuning of two channels. A 30 GHz passive prototype was tested at low power level in order to demonstrate key principles. The prototype showed a power gain 3,8 at a compression ratio 6:1 for an efficiency 63%. An active version of the one-channel pulse compressor is also suggested. It is attractive due to a possibility to achieve higher power gain. The mentioned active version naturally requires an electrically controlled coupler. In particular, as active elements of the coupler we suggest to use gas filled discharge tubes or ferroelectrics which have well recommended itself at 11.4 GHz experiments.

• V. P. Yakovlev
  
• J. L. Hirshfield
  Omega-P, Inc., New Haven, Connecticut
• S. Kazakov
  KEK, Ibaraki

A relatively simple and inexpensive two-cavity 45 MW, 22.8 GHz second-harmonic multiplier is considered as an RF source for High-Gradient experiments. The design is to be based on use of an existing SLAC electron gun, such as the XL-4 gun. RF drive power would be supplied from a 50 MW SLAC klystron and modulator, and a second modulator would be used to power the gun in the multiplier. An important feature of the harmonic multiplier is TE 01 circular waveguide for output RF power extraction.

• 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

• H. Wang
  
• F. Marhauser
  JLAB, Newport News, Virginia
• R. A. Rimmer
  Jefferson Lab, Newport News, Virginia

After initial cavity shape optimization* and cryomodule development** for an Ampere-class FEL, we have simulated the whole 5-cell high-current (HC) cavity structure with six waveguide couplers for HOM damping and fundamental power coupling. The time-domain wakefield method using MAFIA is primarily used for calculation of the broadband impedance. Microwave Studio and Omega-3P are also used for the calculation of external Q (Qext) of individual HOMs. A half scale (1497MHz) single-cell model and a 5-cell copper cavity including dummy HOM waveguide loads were fabricated. Details of measurement results on these prototypes including HOM Qext spectrum, bead-pull data, data analysis technique and comparison to the simulations will be presented.

* H. Wang et. al., "Elliptical Cavity Shape Optimization for Acceleration and HOM Damping," Proc. PAC 05, Knoxville TN, USA, 2005* R. A.Rimmer et al.; EPAC 2006, paper MOPCH182

• 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.

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

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

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

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

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

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

We describe a conceptual design for a superconducting traveling wave accelerator for the ILC. The RF feedback system plus phase shifter can redirect the accelerating wave that passed through the STWA section back to the input of the accelerating structure. In this paper, the STWA cell shape optimization, coupler cell design and rat race ring coupler in the feedback loop are presented. The STWA cell shape is similar to the LL cavity with a 60 mm disk diameter. A 9-cell STWA operates at the mode with group velocity as low as 0.0106 c. Both the ratio of peak electric field and magnetic field to the axial electric field are smaller than in the TESLA 9-cell cavity. The STWA structure has more cells per unit length than a TESLA structure but provides an accelerating gradient higher than a TESLA structure, consequently reducing the cost. The designed rat race directional coupler with four ports has ?3 dB direct coupling coefficients, 16.5 MHz bandwidth between ?30 dB isolations and 1.1 MHz bandwidth between ?30 dB reflection coefficients. Effects of the mechanical tolerances are also discussed.

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

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

• M. A. Plum
  

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

• O. R. Jones
  

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

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

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

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

• M. Apollonio
  

• H. Wang
  
• W. Gai, W. Liu
  ANL, Argonne, Illinois
• A. Kanareykin
  Euclid TechLabs, LLC, Solon, Ohio
• T. Wong
  Illinois Institute of Technology, Chicago, Illinois

* H. Brechna, D. A. Hill and B. M. Bally, "150 KOe Liquid Nitrogen Cooled Flux Concentrator Magnet", Rev. Sci. Instr., 36 1529,1965.

• 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.

• P. Tenenbaum
  
• K. Kubo
  KEK, Ibaraki
• A. Latina
  CERN, Geneva
• J. C. Smith
  CLASSE, Ithaca

The very small vertical beam emittance in the International Linear Collider (ILC) can be degraded by dispersion, xy coupling, transverse wakefields, and time-varying transverse fields introduced by elements with misalignments, strength errors, xy rotation errors, or yz rotation errors in the Ring to Main Linac (RTML) transfer line. We present a plan for emittance preservation in this beamline which uses local, quasi-local, and global correction schemes. Results of simulations of the emittance preservation algorithm are also presented and discussed.

• H. Bluem
  

High power RF testing has been performed on a novel axisymmetric radiofrequency electron gun at a frequency of 11.43 GHz using the magnicon facility at the Naval Research Laboratory. This gun utilizes coaxial coupling from the upstream end of unit and allows for axisymmetric tuning of both the cathode cell and the second cell. The features of the gun have been proven to operate at high gradients. The overall design of the gun will be discussed along with the results of the high power RF testing.

• R. B. Yoder
  
• J. B. Rosenzweig, G. Travish
  UCLA, Los Angeles, California

*R. Yoder and J. Rosenzweig, Phys. Rev. STAB 8, 111301 (2005); Z. Zhang et al., Phys. Rev. STAB 8, 071302 (2005); A. Mizrahi and L. Schachter, Phys. Rev. E 70, 016505 (2004).

• P. V. Avrakhov
  
• N. Solyak
  Fermilab, Batavia, Illinois

• 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.

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

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

• F. Poirier
  
• D. Kruecker, N. J. Walker
  DESY, Hamburg

The small energy-spread, weak wakefields and relatively weak focusing in the ILC superconducting Main Linac result in little or no filamentation beam mismatch errors: linear correlations such as dispersion or cross-plane coupling from transverse misalignment or rotation errors of the quadrupoles respectively do not decohere as the beam is transported (accelerated) along the linac. Using correction available in the Beam Delivery System, the increase in projected emittance due to this linear correlations can to a large degree be corrected. In this paper we present component tolerances based on the assumption of a global correction at the end of the Main Linac. Some discussion on the impact of ground motion is also discussed.

• J. Shi
  
• H. Chen, C.-X. Tang, S. Zheng
  TUB, Beijing
• D. Li
  LBNL, Berkeley, California

• K. M. Hock
  
• A. Wolski
  Liverpool University, Science Faculty, Liverpool

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

• M. Min
  
• Y.-C. Chae, P. F. Fisher
  ANL, Argonne, Illinois

• A. Xiao
  
• M. Borland
  ANL, Argonne, Illinois

The Touschek effect is a major concern for lepton storage rings of low emittance (i.e., high bunch density) and low or moderate beam energy, such as third-generation synchrotron light sources. Piwinski's formula, which includes beam shape variation along the beamline and which is suitable for any beam energy, has been incorporated into a program that interoperates with elegant for use in lifetime calculations. The difference between using Piwinski's method and other simplified methods for the APS is shown in this paper. Furthermore, because of the generality of this formula, we also applied it to transport lines to predict beam loss rates and beam loss locations for the first time. An example related to a possible energy recovery linac upgrade of the APS (APS-ERL) is also given in this paper.

• K. Tian
  
• G. Bai, B. L. Beaudoin, D. W. Feldman, R. B. Fiorito, I. Haber, R. A. Kishek, P. G. O'Shea, M. Reiser, D. Stratakis, D. F. Sutter, J. C.T. Thangaraj, M. Walter, C. Wu
  UMD, College Park, Maryland

Longitudinal perturbations can be generated in the space-charge dominated regimes in which most beams of interest are born. To study the modification of transverse beam distributions by longitudinal beam dynamics, we have conducted experimental studies using low energy electron beams by taking time resolved images of a beam with longitudinal density perturbations. Two different diagnostics are used: optical transition radiation (OTR) produced from an intercepting silicon based aluminum screen and a fast (<5ns decay time) phosphor screen. It is found that the beam is significantly affected by the perturbation. However the OTR signal is very weak and requires over 45 minutes of frame integration. The fast phosphor screen has much better sensitivity (~1'000 times enhancement). In this paper, we also report on the time resolved measurement of a parabolic beam, showing interesting correlations between transverse and longitudinal distributions of the beam.

• J. Li
  
• S. Huang, S. F. Mikhailov, V. Popov, Y. K. Wu
  FEL/Duke University, Durham, North Carolina

As part of the High Intensity Gamma-Ray Source (HIGS) upgrade, the booster synchrotron has been recently commissioned. The booster ramps the electron beam between 0.27 and 1.2 GeV for top-off injection into the Duke storage ring. It has symmetrical injection/extraction schemes with a bumped orbit. The injection/extraction kickers and corresponding septa are located in the opposite straight sections of the booster ring separated by about 1/4 of the vertical betatron wave. Due to the nonideal properties of the magnetic material, the magnetic field leaks out into the stored beam chamber, which directly results in orbit distortion, tune and chromaticity shifts and change of coupling. These effects caused by the extraction septum have been measured as a function of extraction energy. Based upon the measurements, we have developed a scheme to compensate the dynamics effects mentioned above.

• J. R. Harris
  
• R. Feldman, P. G. O'Shea
  UMD, College Park, Maryland

This paper describes the longitudinal expansion of a 10 keV, 100 mA electron beam in the University of Maryland Electron Ring. The expansion of the beam tail was found to be sensitive to the choice of transverse focusing settings due to the presence of an abnormality in the beam current profile. Expansion of the beam head, where no abnormality was observed, is in good agreement with the one-dimensional cold fluid model.

• F.-J. Decker
  
• Y. Nosochkov, M. K. Sullivan, G. Yocky
  SLAC, Menlo Park, California

Orbit bumps in sextupoles are routinely used for tuning the luminosity in the PEP-II B-Factory. Anti-symmetric bumps in a sextupole pair generate dispersion, while symmetric bumps induce a tune shift and beta beat. By coming two of these symmetric bumps with opposite signs where the second pair is 90 degree away, the tune shift cancels and the beta beat doubles. In the low energy ring (LER) we have four sextupole pairs per arc, where pair 1 and 3 are at the same betatron phase and pair 2 and 4are 90 degree away. By making two symmetric bumps with opposite sign in pair 1 and 3 the tune shift and the beta beat outside this region cancel, BUT the LER lifetime improved by a factor of three, losses by a factor of five, and the beam-beam background in the drift chamber of the BaBar detector by 20%. Simulations showed that the phase change at the second sextupole pair introduced by the beta beat can completely cancel the third order chromaticity.

• F.-J. Decker
  
• Y. Cai, Y. Nosochkov, Y. T. Yan, G. Yocky
  SLAC, Menlo Park, California

The low energy ring (LER) in PEP-II has a design emittance of 0.5 nm-rad in the vertical, compared to nearly 0.1 nm-rad for the HER ring. This was thought to come from the "vertical step" of about 1 m in the interaction straight, where the LER beam after horizontal separation gets bend vertical so it sits on top of the HER in the rest of the ring. Since the program MAD does not easily reveal the location of the major emittance contribution, a program was written to calculate the coupled "curly H" parameter of mode 2 (mainly vertical) along z. Weighting it with the magnet bending revealed that the weak long bends inside the "vertical step" did less than 20% of the emittance growth. More than 80% comes from the ends of the adjacent arcs with strong bends. This is caused by the coupling cancellation of the solenoid starting already there with the skew quadrupoles SK5 and 6. By introducing additional skews in the straight instead of SK5 and 6 the emittance could be reduced by a factor of ten in simulations, but with very strong skews. Reasonable strong magnets might generate a workable compromise, since a factor of two in emittance promises 50% more luminosity in beam-beam simulations.

• W. Wittmer
  

The PEP II lattices are unique in their detector solenoid field compensation scheme by utilizing a set of skew quadrupoles in the IR region and the adjacent arcs left and right from the IP. Additionally the design orbit through this region is nonzero. This combined with the strong local coupling wave makes it very difficult to calculate IP tuning knobs which are orthogonal and closed. The usual approach results either in non-closure, not being orthogonal or the change in magnet strength being too big. To find a solution the set of tuning quads had to be extended which resulted having more degrees of freedom than constrains. To find the optimal set of quadrupoles which creates a linear, orthogonal and closed knob and simultaneously minimizing the changes in magnet strength, the method using Singular Value Decomposition, Response Matrices and an Adapted Moore Penrose Method had to be extended. The results of these simulations are discussed below and the results of first implementation in the machine are shown.

• Y. T. Yan
  
• Y. Cai, W. S. Colocho, F.-J. Decker
  SLAC, Menlo Park, California

For optics measurement and modeling of the PEP-II electron (HER) and position (LER) storage rings, we have been doing well with MIA* which requires analyzing turn-by-turn Beam Position Monitor (BPM) data that are resonantly excited at the horizontal, vertical, and longitudinal tunes respectively. However, in anticipating that certain BPM buttons or even pins in the PEP-II IR region will be missing for the next run starting in January 2007, we have been developing a data validation process, hoping to reduce the effect due to the reduced BPM data accuracy on PEP-II optics measurement and modeling. Besides the routine process for ranking BPM noise level through data correlation among BPMs, allowing BPMs to have linear gains and linear cross couplings, we can also check BPM data symplecticity by comparing the invariant ratios. We may also work out nonlinear BPM data correction if needed. Results on PEP-II measurement will be presented.

* Y. T. Yan, et. al. EPAC06 Proceedings, WEPCH062, (2006)

• 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.

• H. Qin
  
• R. C. Davidson, E. Startsev
  PPPL, Princeton, New Jersey

In 3D high-intensity bunched beams, the collective effects associated with strong coupling between the longitudinal and transverse dynamics are of fundamental importance. A direct consequence of this coupling is that the particle dynamics does not conserve transverse energy and longitudinal energy separately, and there exists no exact kinetic equilibrium which has an anisotropic energy in the transverse and longitudinal directions. The strong coupling also introduces a mechanism for the electrostatic Harris-type instability driven by strong temperature anisotropy, which exists naturally in beams that have been accelerated to large velocities. The self-consistent Vlasov-Maxwell equations are applied to high-intensity bunched beams, and a generalized low-noise delta-f particle simulation algorithm is developed for bunched beams with or without energy anisotropy. Systematic studies are carried out that determine the particle dynamics, the approximate equilibrium, and stability properties under conditions corresponding to strong 3D nonlinear space-charge force. Finite bunch-length effects on collective excitations and anisotropy-driven instabilities are also investigated.

• F. Gerigk
  
• N. Alharbi, M. Pasini, S. Ramberger, M. Vretenar, R. Wegner
  CERN, Geneva

• 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.

• M. Mangano
  

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

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

• K. Fiuza
  
• R. Pakter, F. B. Rizzato
  IF-UFRGS, Porto Alegre

This paper analyzes the combined envelope-centroid dynamics of magnetically focused high-intensity charged beams surrounded by conducting walls. Similarly to the case were conducting walls are absent, we show that the envelope and centroid dynamics decouples from each other. Mismatched envelopes still decay into equilibrium with simultaneous emittance growth, but the centroid keeps oscillating with no appreciable energy loss. Some estimates are performed to analytically obtain some characteristics of halo formation seen in the full simulations.

• W. Simeoni
  

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

• F. Marcellini
  

• L. Ficcadenti
  
• D. Alesini, G. Di Pirro, C. Vaccarezza
  INFN/LNF, Frascati (Roma)
• A. Mostacci, L. Palumbo
  Rome University La Sapienza, Roma
• J. B. Rosenzweig
  UCLA, Los Angeles, California

This work has been partially supported by the EU in the sixth framework program, Contract no. 011935 EUROFEL-DS1.

• M. Takao
  
• M. Masaki, J. Schimizu, K. Soutome, S. Takano
  JASRI/SPring-8, Hyogo-ken

• A. Y. Molodozhentsev
  
• T. Koseki, M. Tomizawa
  KEK, Ibaraki
• S. Machida
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon

• S. H. Shin
  
• Y. Honda, J. Urakawa
  KEK, Ibaraki
• E.-S. Kim, H.-S. Kim
  Kyungpook National University, Daegu

• E. Metral
  
• G. Rumolo, R. R. Steerenberg
  CERN, Geneva
• B. Salvant
  EPFL, Lausanne

• F. Zimmermann
  

• F. Roncarolo
  
• R. Appleby, R. M. Jones
  UMAN, Manchester

* Cox, Brian et al., "FP420 : An R&D Proposal to Investigate the Feasibility of Installing Proton Tagging Detectors in the 420 m Region of the LHC", CERN-LHCC-2005-025

• S. R. Babel
  

High voltage power modules find uses in many applications like the Photo multiplier Tubes (PMT), Ionization chambers, CRT systems testing, high voltage biasing for Avalanche Photodiodes, Photo detectors, X-ray tubes, Pulse generators which are used in radars, lasers, EMC testing and other imaging applications. Providing high voltage, to these applications, which can be remotely controlled in a small, confined area, is a problem many laboratories around the world face. The LV and the HV series of high voltage systems from BiRa Systems present experimenters with voltages ranging from several hundreds upto ± 5kV in a rugged CompactPCI / PXI chassis, running National Instruments' LabView. The CompactPCI architecture offers modularity, tight integration and low cost. Apart from that, the deterministic and real time nature of the operating system also allows these modules to be remotely controlled and monitored over the Ethernet. The high voltage cards can be easily custom tailored to a particular voltage and current requirement

• 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.

• R. M. Lill
  
• L. H. Morrison, W. E. Norum, N. Sereno, G. J. Waldschmidt, D. R. Walters
  ANL, Argonne, Illinois
• S. Smith, T. Straumann
  SLAC, Menlo Park, California

In this paper we present the design of the beam position monitor (BPM) system for the LCLS undulator, which features a high resolution X-band cavity BPM. Each BPM has a TM010 monopole reference cavity and a TM110 dipole cavity designed to operate at a center frequency of 11.384 GHz. The signal processing electronics features a low-noise single-stage three-channel heterodyne receiver that has selectable gain and a phase locking local oscillator. We will discuss the system specifications, design, and prototype test results.

• M.-J. Yang
  

• S. Walston
  
• S. T. Boogert
  Royal Holloway, University of London, Surrey
• C. C. Chung, P. Fitsos, J. Gronberg
  LLNL, Livermore, California
• J. C. Frisch, S. Hinton, J. May, D. J. McCormick, S. Smith, T. J. Smith, G. R. White
  SLAC, Menlo Park, California
• H. Hayano, Y. Honda, N. Terunuma, J. Urakawa
  KEK, Ibaraki
• Yu. G. Kolomensky, T. Orimoto
  UCB, Berkeley, California
• P. Loscutoff
  LBNL, Berkeley, California
• A. Lyapin, S. Malton, D. J. Miller
  UCL, London
• R. Meller
  Cornell University, Department of Physics, Ithaca, New York
• M. C. Ross
  Fermilab, Batavia, Illinois
• M. Slater, M. Thomson, D. R. Ward
  University of Cambridge, Cambridge
• V. Vogel
  DESY, Hamburg

• S. S. Kurennoy
  

* J. D. Gilpatrick et al. These proceedings.** S. S. Kurennoy and R. E. Shafer, EPAC 2000 (Vienna, Austria, 2000), 1768.

• W. J. Corbett
  
• X. Huang, M. J. Lee, P. Lui
  SLAC, Menlo Park, California
• B. Sayyar-Rodsari
  Pavilion Technologies, Inc, Austin, Texas

The primary contributing factors to electron beam lifetime in a storage ring are elastic and inelastic gas scattering, and intrabeam scattering. In order to further quantify the relative contributions of each mechanism, a series of measurements using vertical scraper position and rf-voltage sweeps were performed in SPEAR3 with fill patterns featuring different single-bunch and total beam currents. In parallel, an analytic beam-lifetime simulator was developed taking scattering cross-sections, rf-bucket height and bunch lengthening effects into account. In this paper, we compare measured results with the simulated results in an effort to develop a comprehensive model for electron beam lifetime under a variety of operating conditions.

• R. M. Jones
  
• G. Burt
  Cockcroft Institute, Lancaster University, Lancaster
• N. Chanlek, B. Spencer
  UMAN, Manchester
• P. Goudket
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

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