LINAC 2004 - List of Sessions

MOP — Monday Poster Session (16-Aug-04 15:30—17:30)

Paper	Title	Page
MOP01	Beam Intensity Adjustment in the RIA Driver Linac	33
	P.N. Ostroumov, J.A. Nolen, I. Sharamentov ANL/Phys, Argonne, Illinois A.V. Novikov-Borodin RAS/INR, Moscow
	The Rare Isotope Accelerator Facility currently being designed in the U.S. will use both heavy ion and light ion beams to produce radionuclides via the fragmentation and spallation reactions, respectively. Driver beam power of up to 400 kW will be available so that beam sharing between target stations is a viable option to increase the number of simultaneous users. Using a combination of rf-sweepers and DC magnets the driver beams can be delivered to up to four targets simultaneously. With simultaneous beam delivery to more than one target independent adjustment of the relative beam intensities is essential. To enable such intensity adjustment we propose to use a fast chopper in the Medium Energy Beam Transport (MEBT) section. Several options of fast chopper design are discussed. The MEBT beam optics is being designed to accommodate and match the chopper technical specifications. Possible solutions and performance with the fast chopper are proposed.
MOP03	Proposal for Reduction of Transverse Emittance of BNL 200 MeV Linac	36
	J. Alessi, J. Beebe Wang, D. Raparia, W.-T. Weng BNL, Upton, Long Island, New York
	BNL plans to upgrade the AGS proton beam from the current 0.14 MW to higher than 1.0 MW and beyond for such a neutrino facility which consists of two major subsystems. First is a 1.2 GeV super-conducting linac (SCL) to replace the booster as injector for the AGS. Second is the performance upgrade for the AGS itself for the higher intensity and repetition rate. For high intensity proton accelerators, such as the upgraded AGS, there are very stringent limitations on uncontrolled beam losses. A direct effect of linac beam emittance is the halo/tail generation in the circulating beam. Studies show the estimated halo/tail generation in the beam for present normalized RMS emittance of linac beam is unacceptable. To reduce the transverse emittance of 200 MeV linac, the existing radio frequency quadrupole linac (RFQ) has to be relocated closer to drift tube linac (DTL) tank 1 to meet emittance requirement for the AGS injection with low loss. This paper will present the various options of matching between RFQ and DTL, and chopping options in the low energy beam transport (LEBT).
MOP05	The HITRAP-Decelerator for Heavy Highly-Charged Ions	39
	L. Dahl, W. Barth, T. Beier, W. Vinzenz GSI, Darmstadt C. A. Kitegi, U. Ratzinger, A. Schempp IAP, Frankfurt-am-Main
	The GSI accelerator facility provides highly charged ions up to U⁹²⁺ by stripping the ions at 400 MeV/u in the transfer line from the SIS18 (Heavy Ion Synchrotron) to the ESR (Experimental Storage Ring). The ESR provides high quality beams by means of stochastic cooling and electron cooling. Deceleration down to 4 MeV/u was already successfully demonstrated. After suitable rebunching, further deceleration down to 6 keV/u, neccessary for the capture of the ions by a penning trap, is done by IH/RFQ-structures. All cavities are operated at 108 MHz. Recently the HITRAP-project (Heavy Ion Trap), described in a Technical Design Report, was approved. The layout of the decelerator and the beam dynamics in different sections are reported.
MOP06	A Dedicated 70 MeV Proton Linac for the Antiproton Physics Program of the Future Facility for Antiproton and Ion Research (FAIR) at Darmstadt	42
	L. Groening, W. Barth, L. Dahl, R. Hollinger, P. Spädtke, W. Vinzenz, S. Yaramishev GSI, Darmstadt B. Hofmann, Z. Li, U. Ratzinger, A. Schempp, R. Tiede IAP, Frankfurt-am-Main
	The antiproton physics program of the future International Accelerator Facility at Darmstadt is based on a rate of 7·10¹⁰ cooled antiprotons per hour. To provide the primary proton intensities a proton linac is planned, which will be operated independently from the existing UNILAC for heavy ions. The proposed linac comprises a proton source, a RFQ, and a DTL. Its operation frequency of 352 MHz allows for an efficient acceleration to up to 70 MeV using normal conducting Crossed-bar H-cavities. These CH-cavities show high shunt impedances as known from IH-structures, but allow for much higher relative particle velocities of up to 40%. The beam pulses with a length of 25 μs, a current of 70 mA, and total transverse emittances of 7 μm will allow to fill the existing synchrotron SIS within one multi-turn-injection up to its space charge limit of 7·10¹² protons. The maximum SIS ramping rate limits the applied proton linac repetition rate to 5 Hz. This paper gives an overview of the proposed proton linac. The status of the design including beam dynamic studies will be reported.
	Transparencies
MOP07	High Current Beam Transport to SIS18	45
	S. Richter, W. Barth, L. Dahl, J. Glatz, L. Groening, S. Yaramishev GSI, Darmstadt
	The optimized transversal and longitudinal matching of space charged dominated ion beams to SIS18 is essential for a loss free injection. This paper focuses on the beam dynamics in the transfer line (TK) from the post-stripper accelerator to the SIS18. Transverse beam emittance measurements at different positions along the TK were done. Especially, the different foil stripping modes were investigated. A longitudinal emittance measurement set-up was commissioned at the entry to the TK. It is used extensively to tune all the rebunchers along the UNILAC. An addition, a test bench is in use for measurements of longitudinal bunch profiles, which enables to monitor for the final debunching to SIS18. Multi particle simulations by means of PARMILA allow a detailed analysis of experimental results for different ion currents.
MOP08	Investigation of the Beam Matching to the GSI-Alvarez DTL under Space Charge Conditions	48
	S. Yaramishev, W. Barth, L. Dahl, L. Groening, S. Richter GSI, Darmstadt
	The UNILAC consists of the 36 MHz high current RFQ/IH-injector, a gas stripper section at an energy of 1.4 MeV/u and a 108 MHz Alvarez poststripper, accelerating all ions up to of 11.4 MeV/u. The design beam current for U²⁸⁺ is 12.6 emA at full energy. After the stripping process the electrical beam current is increased by a factor of 7 for uranium. This leads to a significant beam emittance growth during the transport through the charge state separator and the matching section to the Alvarez DTL. The paper reports results of beam experiments focused on the matching of the high intensity beams to the Alvarez for different ion species. Measured data are compared with the results of beam dynamics simulations. Possible improvements of the transverse focusing in the Alvarez linac are discussed and the total impact to the beam quality at the synchrotron injection is evaluated.
	Transparencies
MOP09	Status of the 7 MeV/u, 217 MHz Injector Linac for the Heidelberg Cancer Therapy Facility	51
	B. Schlitt, K. Dermati, G. Hutter, F. Klos, C. Mühle, W. Vinzenz, C. Will, O. Zurkan GSI, Darmstadt A. Bechtold, U. Ratzinger, A. Schempp IAP, Frankfurt-am-Main Y.R. Lu PKU/IHIP, Beijing
	A clinical synchrotron facility for cancer therapy using energetic proton and ion beams (C, He and O) is under construction and will be installed at the Radiologische Universitätsklinik in Heidelberg, Germany, starting in 2005. The status of the ECR ion source systems, the beam line components of the low energy beam transport lines, the 400 keV/u RFQ and the 20 MV IH-cavity as well as the linac rf system will be reported. Two prototype magnets of the linac quadrupole magnets have been built at GSI and have been tested successfully. A test bench for the 1.4 MW, 217 MHz cavity amplifier built by industry has been installed at GSI including a 120 kW driver amplifier which will be used also for high power tests of the RFQ. A test bench for the RFQ using proton beams is presently being set up at the IAP. RF tuning of the 1:2 scaled IH-DTL model as well as Microwave Studio simulations of the model and the power cavity have been also performed at the IAP [1]. [1] Y.Lu, S.Minaev, U.Ratzinger, B.Schlitt, R.Tiede, this conference.
	Transparencies
MOP10	The IH Cavity for HITRAP	54
	C. A. Kitegi, U. Ratzinger IAP, Frankfurt-am-Main S. Minaev ITEP, Moscow
	RFQs are already successfully used to decelerate ions and to match them to ion traps. Within the Heavy Ions TRAP project HITRAP at GSI a combination of an IH drift tube cavity operating at the H11(0) mode and a 4-rod RFQ is proposed to decelerate the 1 ms long heavy ion bunches (up to U⁹²⁺) from 4 A×MeV to 6 A keV after storage ring extraction. The transition energy from the IH into the RFQ is 0.5AmeV. The operating frequency is 108.408 MHz. The A/q range of the linac is up to 3.A 4-gap quarter wave resonator working at 108.408MHz provides theμbunch structure for the IH. The transmission mainly defined by the buncher is about 30%. An alternative 2nd harmonic bunching section, which allows higher transmission and/or smaller longitudinal emittance, will be discussed.By applying the KONUS dynamics, the 2.7 meter long IH cavity will perform a high efficient deceleration by up 10.5 MV with 200kW rf power. The beam dynamics performed with the LORASR simulation code will be shown. It is aimed to reach an effective shunt impedance around 220MW/m for the IH cavity
MOP11	The Compact 20 MV IH-DTL for the Heidelberg Cancer Therapy Facility	57
	Y.R. Lu, Y.R. Lu, B. Schlitt GSI, Darmstadt S. Minaev ITEP, Moscow U. Ratzinger, R. Tiede IAP, Frankfurt-am-Main
	A clinical synchrotron facility for cancer therapy using energetic proton and ion beams (C, He and O) is under construction and will be installed at the Radiologische Universitätsklinik in Heidelberg, Germany, starting in 2005. The different rf tuning concepts and tuning results for an 1:2 scaled IH-DTL model cavity are presented. Microwave Studio simulations have been carried out for the model and for the real power cavity. Results from the model measurements and the field simulations agree very well also for the higher order modes. The beam matching from the RFQ to the IH-DTL was optimised. Beam dynamics simulations using the LORASR code and starting with a particle distribution at the RFQ exit as calculated with PARMTEQ are presented. The IH drift tube array was matched with the gap voltage distribution resulting from rf model measurements.
MOP12	KONUS Beam Dynamics Design of a 70 mA, 70 MeV Proton CH-DTL for GSI-SIS12	60
	R. Tiede, G. Clemente, H. Podlech, U. Ratzinger IAP, Frankfurt-am-Main W. Barth, L. Groening GSI, Darmstadt Z. Li IMP, Lanzhou S. Minaev ITEP, Moscow
	The future scientific program at GSI needs a dedicated proton injector into the synchrotron SIS, in order to increase the proton intensity of the existing UNILAC/SIS12 combination by a factor of 70, resulting in 7· 10¹² protons in the synchrotron. A compact and efficient 352 MHz RFQ - CH-DTL combination based on novel structure developments for RFQ and DTL was worked out. For DTLs operated in an H-mode like CH-cavities (H210-mode), the shunt impedance is optimized by use of the KONUS beam dynamics. Beam dynamics simulation results of the CH-DTL section, covering the energy range from 3 to 70 MeV, with emphasis on the low energy front end are presented. Optimization aims are the reduction of emittance growth, of beam losses and of capital costs, by making use of the high acceleration gradients and shunt impedance values provided by the Crossbar H-Type (CH) structure. In addition, the beam dynamics design of the overall DTL layout has to be matched to the power limits of the available 352 MHz power klystrons. The aim is to power each cavity by one klystron with a peak rf power of around 1 MW.
MOP14	Development of Intense Beam Proton Linac in China	63
	S. Fu, S.X. Fang, H. Ouyang, S. Zhao IHEP Beijing, Beijing B. Cui, X. Guan CIAE, Beijing J. Fang, Z.Y. Guo PKU/IHIP, Beijing
	Study on intense beam proton linac was started about four years ago in a national program for the basic research on ADS in China. This ADS program is meant for the future development of the clean nuclear power generation. Another important application of HPPA for Chinese Spallation Neutron Source was also proposed recently in China, and it is financially supported by Chinese Academy of Sciences. In this paper, the research progress on intense beam proton linac in these two application fields will be outlined. It involves the test result of an high-current ECR proton source, construction status of a 3.5 MeV RFQ accelerator and the design of a DTL linac.
MOP15	TRASCO-RFQ as Injector for the SPES-1 Project	66
	P. Posocco, M. Comunian, A. Pisent INFN/LNL, Legnaro, Padova E. Fagotti INFN Milano, Milano
	The funded first phase of SPES foresees the realization at LNL of a facility able, on one hand, to accelerate a 10 mA protons beam up to 20 MeV for nuclear studies and, on the other hand, to accelerate a 30 mA protons beam up to 5 MeV for BNCT and preliminary ADS studies. In this two-way facility, the TRASCO RFQ will operate in two different current regimes. Moreover a specific MEBT has to be designed able to match the beam to the following superconducting linac and to deliver a beam with the correct characteristics to the neutron production target for the BNCT studies.
MOP16	The TRASCO-SPES RFQ	69
	A. Pisent, M. Comunian, J. Esposito, A. Palmieri INFN/LNL, Legnaro, Padova E. Fagotti INFN Milano, Milano G. Lamanna CINEL, Vigonza (PD) M. S. Mathot CERN, Geneva
	A high intensity RFQ is under construction at LNL. Developed within TRASCO research program, the Italian feasibility study an ADS (Accelerator Driven System), it will be employed as the first accelerating element of SPES facility, the ISOL project of LNL. The RFQ operates at the frequency of 352 MHz in CW mode, is able to deliver a proton current up to 30 mA and consists of six brazed segments whose length is 1.2 m. In this article the results obtained from the construction of a 20 cm “technological model”, aimed at testing the construction procedure of the final structure, will be discussed. Finally we will report about the machining and the outcomes obtained after RF testing of the first two segments built up to now.
MOP17	Design of the SPES-1 LEBT	72
	E. Fagotti INFN Milano, Milano M. Comunian, A. Pisent INFN/LNL, Legnaro, Padova
	The low-energy-beam transport (LEBT) system for the SPES-1 accelerator transports the beam at 80 keV and 30 mA from the ion-source TRIPS to the TRASCO RFQ entrance. A second mode of operation corresponding to 10 mA current is also foreseen. The code PARMELA performed these simulations of the beam transport through the LEBT. This code is used to transport H⁺ and H²⁺ in the electrostatic fields of the ion-source extraction, in the magnetic fields of both the source and the solenoid lenses and under space charge and neutralization influence.
MOP18	Cold-Model Tests and Fabrication Status for J-PARC ACS	75
	H. Ao, H. Akikawa JAERI/LINAC, Ibaraki-ken K. Hasegawa, A. Ueno JAERI, Ibaraki-ken N. Hayashizaki TIT, Tokyo M. Ikegami, S. Noguchi KEK, Ibaraki V.V. Paramonov RAS/INR, Moscow Y. Yamazaki J-PARC, Ibaraki-ken
	The J-PARC (Japan Proton Accelerator Research Complex) LINAC will be commissioned with energy of 181-MeV using 50 keV ion source, 3 MeV RFQ, 50 MeV DTL and 181 MeV SDTL (Separated DTL) on September 2006. It is planed to be upgraded by using 400 MeV ACS (Annular Coupled Structure), which is a high-beta structure most suitable for the J-PARC, in a few years from the commissioning. The first ACS cavity, which will be used as the first buncher between the SDTL and the ACS, is under fabrication. Detailed design and tuning procedure of ACS cavities has been studied with RF simulation analysis and cold-model measurements. The results of cold-model measurements, fabrication status, and related development items are described in this paper.
MOP19	Particle Distributions at the Exit of the J-PARC RFQ	78
	Y. Kondo, A. Ueno JAERI, Ibaraki-ken K. Ikegami, M. Ikegami KEK, Ibaraki
	A 324 MHz, 3 MeV RFQ (Radio-Frequency Quadrupole) linac with 3.115 m vane length is used as the first RF linac of the J-PARC linac. The results of the J-PARC linac end-to-end (from the RFQ entrance to the injection point of the RCS) simulations significantly depend on the initial particle distributions. In the transverse phase spaces, Gaussian particle distributions, whose parameters were decided to reproduce the emittance measured in the LEBT (Low Energy Beam Transport), was used at the entrance of the RFQ. Two simulation codes, PARMTEQM and TOUTATIS, were used to produce the particle distributions at the exit of the RFQ. Since the simulated emittances showed good agreements with the emittances measured at downstream of the RFQ, they were confirmed to have the validity to be used as the initial distribution of the end-to-end simulation.
MOP20	Design of the R.T. CH-Cavity and Perspectives for a New GSI Proton Linac	81
	Z. Li IMP, Lanzhou W. Barth, K. Dermati, L. Groening GSI, Darmstadt G. Clemente, H. Podlech, U. Ratzinger, R. Tiede IAP, Frankfurt-am-Main
	The CH-Structure has been studied at the IAP Frankfurt and at GSI for several years. Compared with the IH structure (H110-mode), the CH structure (H210-mode) can work at higher frequency (700 MHz) and can accelerate ions to higher energy (up to 150 AMeV). Detailed Microwave Studio (MWS) simulations were performed for this structure. Since a multi-gap cavity can be approximated as a quasi-periodic structure, it is possible to analyze one βλ/2-cell at an energy corresponding to the cavity center. Additionally, a reduced copper conductivity of 85% was assumed. Geometry variations with respect to rf frequency and shunt impedance can be performed rapidly by that method in the first stage of optimization. Effective shunt impedances from 100 MΩ/m down to 25 MΩ/m were obtained for the energy range from 5 AMeV to 150 AMeV by this method. The rf frequency was 350 MHz up to 70 MeV and 700 MHz above. A systematic analysis of the influence of the cell number in long CH cavities on the effective shunt impedance is presented. The possibility to apply this structure to a 70 mA, 70 MeV, 352 MHz proton linac for GSI is discussed.
MOP21	The Pre-Injector Linac for the Diamond Light Source	84
	C. Christou, V. Kempson DIAMOND, Chilton, Didcot, Oxon K. Dunkel, C. Piel ACCEL, Bergisch Gladbach
	The Diamond Light Source is a new medium-energy high brightness synchrotron light facility which is under construction on the Rutherford Appleton Laboratory site in the U.K. The accelerator facility can be divided into three major components; a 3 GeV 561 m circumference storage ring, a full-energy booster synchrotron and a 100 MeV pre-injector linac. This paper describes the linac design and plans for operation. The linac is supplied by ACCEL Instruments GmbH under a turn-key contract, with Diamond Light Source Ltd. providing linac beam diagnostics, control system hardware and standard vacuum components. Commissioning of the linac will take place in early 2005 and user operation of the facility will commence in 2007.
MOP24	Using a Solid State Switch for a 60kV Bouncer to Control Energy Spread during the Beam Pulse*	87
	L. Donley, J.C. Dooling, G.E. McMichael, V. F. Stipp ANL, Argonne, Illinois
	The beam injected into the IPNS Linac is from a column utilizing a Cockcroft-Walton voltage source. The accelerating column consists of a single high gradient gap. To lessen the likelihood of gap voltage breakdown, we pulse (“bounce”) the column voltage up during the beam pulse allowing the column DC voltage to be lower. The accelerating voltage is supplied through a 5 MΩ resistor and has only small capacitance to hold the voltage constant during the beam pulse. A capacitor is connected between the high voltage end of the column and the bouncer pulse generator. The bouncer pulse increases the column voltage to the proper level just microseconds before the beam pulse. A slope on the top of the bouncer pulse allows for correction to be added, compensating for the voltage droop that results from beam loading. The bouncer that has served this purpose in the past utilized a tube amplifier. In searching for a suitable replacement system it was decided that the system should be able to deliver a 60 kV pulse and the slope on the top of the pulse could be controlled by an RC rise. A solid state switch was purchased for this application. Switch protection and other design decisions will be discussed.
MOP25	The LEBRA 125 MeV Electron Linac for FEL And PXR Generation	90
	K. Hayakawa, Y. Hayakawa, K. Ishiwata, K. Kanno, K. Nakao, T. Sakai, I. Sato, T. Tanaka LEBRA, Funabashi K. Yokoyama KEK, Ibaraki
	A 125 MeV electron linac has been constructed at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University for Free Electron Laser (FEL) and Parametric X-ray (PXR) generation. Two klystrons feed rf power of approximately 20 MW peak and 20 μsec pulse duration each to an injector and three 4 m accelerating structures. Phase of the rf fed to each component is controlled independently. Two accelerating structures connected with the second klystron and a ninety degrees bending system as a momentum analyzer constitute a magnetic bunching system. Electron bunches of 3 to 4 psec width formed at the injector are compressed to within 1 psec during passing through the magnetic bunching system. Peak current of the electron beam injected to the FEL system installed downstream of the momentum analyzer is expected to be about 50 A. FEL lasing has been achieved at the wavelength range from 1 to 6 mm. Estimated peak power of the extracted FEL light pulse is about 2 MW. Applied researches using the FEL started last autumn. Preliminary experiment for the PXR generation has been continued.
MOP26	ERLP Gun Commissioning Beamline Design	93
	D.J. Holder, C.K.M. Gerth, F.E. Hannon CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire R.J. Smith CLRC, Daresbury, Warrington, Cheshire
	The 4GLS project is a novel next-generation solution for a UK national light source. It is based on an energy recovery linac (ERL) operating at high average beam currents up to 100 mA and with compression schemes producing pulses in the 10 - 100 fs range. This challenging accelerator technology, new to Europe, necessitates a significant R&D programme and a major part of this is a low-energy prototype, the ERLP, which is currently under construction at Daresbury Laboratory, in the north-west of England. The first components of ERLP to be built will be the DC photocathode gun and low-energy beam transport and diagnostics. The gun will initially be operated with a diagnostic beamline in order to measure the properties of the high-brightness beams generated as fully as possible. This will allow comparison of its performance with the results of multi-particle tracking codes, prior to its integration into the ERLP machine. The diagnostic beamline will include diagnostics for measuring the transverse and longitudinal properties of the electron beam. This paper will describe the design of this diagnostic beamline and demonstrate through simulation, the expected characteristics and performance achievable from this system.
MOP27	Commissioning of a 6 MeV X-Band SW Accelerating Guide	96
	Q. Jin, Y. Lin, X. Sun, X. Tao, D. Tong TSINGHUA, Beijing B. Chen, B. Sun, Y. Zou BIEVT, Beijing 100016
	A 6 MeV, X-band on-axis SW electron linear accelerating guide is being developed in Accelerator laboratory of Tsinghua University. It can be suitable for portable radiation therapy and radiography. The design, manufacture and high power test of the guide are given in this paper. The guide is 38 cm long and contains 25 accelerating cells with 24 coupling cells, operated in the π/2 mode. The RF power source is a pulsed magnetron at 9300 MHz with 1.5 MW peak power. The results of beam tests are following: the electron energy is more than 6 MeV at 50 mA and focal spot size is less than φ 1.5 mm without any focusing solenoid.
MOP28	A Study of Higher-Band Dipole Wakefields in X-Band Accelerating Structures for the G/NLC	99
	R.M. Jones SLAC/ARDA, Menlo Park, California
	The X-band linacs for the GLC/NLC (Global Linear Collider/Next Linear Collider) have evolved from the DDS (Damped Detuned Structure) series [1,2]. The present series of accelerating structures are each 60 cm in length and incorporate both damping and detuning of the dipole modes which comprise the wakefield. In order to adequately damp the wakefield the dipole frequencies of adjacent structures are interleaved. The properties of the first dipole band have been extensively studied. However, limited analysis has been done on the higher order dipole bands. Here, we calculate the contribution of the higher order bands of the interleaved structures to the wakefield using a mode matching computer code [3]. Beam dynamics issues are also studied by tracking the beam through the complete linac using the particle beam tracking code LIAR [4]. [1] R.M Jones et al,1996,Proc. EPAC96 (also SLAC-PUB-7187) [2] J.W. Wang et al, 2000, Proc. LINAC2000 (also SLAC-PUB-8583) [3] V.A. Dolgashev, Ph.D. thesis, Budker INP, Novosibirsk, 2002.[4] R. Assman et al, LIAR, SLAC-PUB AP-103
MOP29	RHIC Electron Cooler	102
	J. Kewisch, I. Ben-Zvi, R. Calaga, X.Y. Chang, A. Jain, V. Litvinenko, C. Montag, V. Yakimenko BNL, Upton, Long Island, New York
	Electron cooling has been applied in many accelerators with low energies where cooling times are short. Electron cooling is now considered for RHIC, where gold ions are stored at 100 GeV/u. For a cooling time of one hour an electron beam with 55 MeV and 10 nC/bunch is necessary. The transverse normalized emittance must be 50 mm·mrad, the energy spread 10^-4. Only a Photo-cathode Energy Recovery LINAC (PERL) promises such quality. For a minimum electron temperature inside the 1 Tesla cooling solenoid it is necessary to have a "magnetized beam", i.e. a beam from a cathode immersed in a longitudinal magnetic field. The emittance compensation scheme used in RF guns was adapted so that the magnetization does not lead to strong emittance growth. A super-conducting cavity was developed for the RHIC electron cooler, optimized for high current operation. Simulations with the TBBU computer code show a multi-bunch beam breakup threshold of 3 Amperes. After acceleration the bunches are lengthened and the energy spread is reduced by rotation in the longitudinal phase space. The original bunch length must be restored by a second rotation before deceleration and energy recovery.
MOP30	Linear Accelerator LINAC-800 of the DELSY Project	105
	V.V. Kobets, N. Balalykin, I.N. Meshkov, I.A. Seleznev, G. Shirkov JINR, Dubna, Moscow Region
	In the report the modernization of electron linear accelerator MEA (Medium Energy Accelerator) is discussed. The goal of the work is to create on the base of MEA a complex of free electron lasers overlaying a range of radiation waves from infrared to ultraviolet. Status of the work is reported.
MOP31	Development of a C-band Accelerating Module for SUPERKEKB	108
	S. Ohsawa, M. Ikeda, K. Kakihara, T. Kamitani, T. Oogoe, T. Sugimura, S. Yamaguchi, K. Yokoyama KEK, Ibaraki
	High power rf processing of 1 m C-band accelerating section for Super KEKB was successfully performed and power corresponding to 42 MV/m was achieved. Processing data were accumulated including acoustic sensor to find the arcing position. No structural damage was observed from the phase shift measurement performed after the processing. Processed accelerator was installed in the beam line of KEKB linac and being re-processed. The beam acceleration of 40 MV/m was successfully achieved in October 2003. Present status of C-band accelerator development is reported.
MOP34	Injector Linac Upgrade for the BEPCII Project	111
	S.H. Wang IHEP Beijing, Beijing
	BEPCII- an upgrade project of Beijing Electron Positron Collider (BEPC) is a factory type of e⁺e^- collider. It requests its injector linac to have the higher beam energy (1.89 GeV) for on-energy injection and the higher beam current (40 mA e⁺ beam) for higher injection rate (≥50 mA/min). The low beam emittance (1.6 π·mm·mrad for e⁺ beam, and 0.2 π·mm·mrad for 300 mA e^- beam) and low beam energy spread (±0.5%) are also requested to meet the storage ring acceptance. Hence the original BEPC injector linac must be upgraded to have a new electron gun with its complete tuning system, a new positron source with a flux concentrator, a new RF power system with its phasing loops and a new beam tuning system with orbit correction and optics tuning devices. These new components have been designed, fabricated, tested and now being installed in their final positions, which are described in this paper. The beam commissioning is expected to start from the October of 2004.
	Transparencies
MOP35	The Research of a Novel SW Accelerating Structure with Small Beam Spot	114
	X. Yang, H. Chen, Y. Chen, X. Jin, M. Li, H. Lu, Z. Xu CAEP/IAP, Mianyang, Sichuan
	A new kind of on-axis coupled biperiodic standing-wave (SW) accelerating structure has been built for a 9 MeV accelerator. The research progress was introduced in this paper, it includes the choice of the accelerating structure, the analysis of electron beam dynamics, the tuning of the cavity, the measurement of the accelerating tube and the powered test. The small beam spot is the most interesting feature of this accelerating structure, the diameter of the beam spot is 1.4 mm. This accelerator has been used for the x photons generation and the x-ray dose rate is about 3400 rad/min/m.
MOP36	Preliminary Study on HOM-Based Beam Alignment in the TESLA Test Facility	117
	N. Baboi, G. Kreps, M. Wendt DESY, Hamburg G. Devanz, R. Paparella CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex O. Napoly CEA/DSM/DAPNIA, Gif-sur-Yvette
	The interaction of the beam with the higher order modes (HOM) in the TESLA cavities has been studied in the past at the TESLA Test Facility (TTF) in order to determine whether the modes with the highest loss factor are sufficiently damped. The same modes can be used actively for beam alignment. At TTF the beam alignment based on the HOM signals is planned to be studied in the first cryo-module, containing 8 accelerating cavities. One of several modes with higher loss factor will be used. Its polarization has to be determined. The options to use single bunches or bunch trains will be analyzed. The results will be discussed in this paper.
MOP37	Optimization of Positron Capture in NLC	120
	Y.K. Batygin SLAC, Stanford
	In the Next Linear Collider design, the positron capture system includes a positron production target, a flux concentrator, and a linac to accelerate positrons up to 1.9 GeV, the injection energy of the positron pre-damping ring. Two schemes for positron production have been studied: a conventional approach with a 6.2 GeV electron beam interacting with a high-Z target and polarized positron production using polarized photons generated in a helical undulator by a 150 GeV electron beam which then interact with a positron production target. The capture system has been optimized to insure high positron yield into the 6-dimensional acceptance of the pre-damping ring. Various parameters affecting the positron capture have been analyzed, including: positron deceleration after the flux concentrator, transverse and longitudinal electron beam sizes for positron generation, energy compression after acceleration, etc. As a result of these optimization studies, the positron yield in the conventional scheme has been increased from 1.0 to at least 1.5 and for the polarized positron scheme from 0.25 to 0.30 while maintaining 60% positron polarization.
	Transparencies
MOP38	Background from Undulator in the Proposed Experiment with Polarized Positrons	123
	Y.K. Batygin SLAC, Stanford
	E-166 is a proposed experiment for verification of polarized positron production for linear collider. According to polarized positron source design, high energy electrons pass through helical undulator and produce circularly polarized photons, which interact with tungsten target and produce longitudinally polarized positrons. In the proposed E-166 experiment, 50 GeV beam propagates inside 1m long undulator followed by a drift space of 35 m before interaction with target. Polarized positrons are analyzed by Si-W calorimeter, which is placed along the axis. Polarized positrons are analyzed by CsI calorimeter after reconversion of positrons to photons at the second target. Background is an issue for a considered experiment. GEANT3 simulations were performed to model production of secondary particles from primary electrons hitting undulator. Energy density distribution of background particles at the target and effect of background collimation are discussed.
MOP39	Positron Transmission and Polarization in E-166 Experiment	126
	Y.K. Batygin SLAC, Stanford
	The proposed experiment E-166 at SLAC is designed to demonstrate the possibility of producing longitudinally polarized positrons from circularly polarized photons. Experimental set-up utilizes a low emittance 50 GeV electron beam passing through a helical undulator in the Final Focus Test Beam line of SLAC accelerator. Circularly polarized photons generated by the electron beam in undulator hit a target and produce electron-positron pairs. The purpose of post-target optics is to select the positron beam and to deliver it to a polarimeter keeping positron beam polarization as high as possible. Paper analyzes the positron transmission and polarization both numerically and analytically. The value of positron transmission has a maximum of 3% for positron energy of 7 MeV while positron polarization is around 80%.
MOP40	A Study Of Coupler-Trapped Modes In X-Band Linacs for the GLC/NLC	129
	R.M. Jones, V.A. Dolgashev SLAC/ARDA, Menlo Park, California Z. Li SLAC, Menlo Park, California J. Wang SLAC/ARDB, Menlo Park, California
	Each of the X-band accelerating structures for the GLC/NLC consist of 55 cells which accelerate a train of charged particles. The cells are carefully designed to ensure that the transverse wakefield left behind each bunch does not disrupt the trailing bunches. However, unless attention is paid to the design of the fundamental mode coupler, then a dipole mode is trapped in the region of the coupler and cells. This mode can give rise to severe emittance dilution if care is not taken to avoid a region of resonant growth in the emittance. Here, we present results on HFSS simulations, cold test experimental measurements and beam dynamics simulations arising as a consequence of the mode trapped in the coupler. The region in which the trapped mode has little influence on the beam is delineated.
MOP41	Emittance-Imposed Alignment and Frequency Tolerances for the TESLA Linear Collider	132
	N. Baboi DESY, Hamburg R.M. Jones SLAC/ARDA, Menlo Park, California
	One option in building a future 500 GeV c.m. collider is to use superconducting 1.3 GHz 9-cell cavities. Wakefields excited by the bunch train in the TESLA linac can resonantly drive the beam into unstable operation such that a BBU (Beam Break Up) mode results or at the very least significant emittance dilution occurs. The largest kick factors (proportional to the transverse fields which transversely kick the beam off axis) are found in the first three dipole bands and hence multi-bunch emittance growth is mainly determined from these bands. These higher order dipole modes are damped by carefully orientating higher order mode couplers at the downstream end of the cavities. We investigate the dilution in the emittance of a beam injected with an initial offset from the axis of the cavities. The dependence of beam emittance on systematic errors in the cell frequencies is investigated. We also vary the bunch spacing in order to simulate a systematic frequency error. While scanning the bunch spacing over a wide range, the emittance presents sharp peaks since only few modes contribute effectively to emittance growth. The locations of these peaks sets the frequency tolerances on the structures.
MOP42	Linac Alignment and Frequency Tolerances from the Perspective of Contained Emittances for the G/NLC	135
	R.M. Jones SLAC/ARDA, Menlo Park, California
	We maintain the stable progress of a beam consisting of a train of bunched charges, by a careful design of the geometry of the structures [1]. In practice, the next generation of linear colliders will consist of several tens of thousands of X-band accelerating structures and this will entail inevitable errors in the dimensions and alignments of cells -and groups thereof. These errors result in a dilution of the beam emittance and consequently a loss in overall luminosity of the collider. For this reason it is important to understand the alignment tolerances and frequency tolerances that are imposed for a specified emittance budget. Here we specify an emittance dilution of no more than 10% of the initial value and we track the progress of the beam down the linac whilst accelerating structures (and sub-groups thereof) are misaligned in a random manner and at the same time random frequency are incorporated with structures. This results in tolerances in both frequency errors and sets of alignment errors to be imposed on the structures for a specified emittance dilution. [1] R.M. Jones, 1997, SLAC NLC-Note 24.
MOP43	The Impact of Longitudinal Drive Beam Jitter on the CLIC Luminosity	138
	D. Schulte, E. J. N. Wilson, F. Zimmermann CERN, Geneva
	In the compact linear collider (CLIC) now under study at CERN, the RF power which accelerates the main beam is provided by decelerating a high current drive beam. Errors in the timing and intensity of the drive beam can turn into RF phase and amplitude errors that are coherent along the whole main linac and the resulting error of the final beam energy, in combination with the limited bandwidth of the beam delivery system, can lead to a significant loss of luminosity. We discuss the stability tolerances that must be applied to the drive beam to avoid this loss. We also examine one of the most important sources of this jitter, which stems from the combination of RF jitter in the drive beam accelerator and subsequent bunch compression. Finally we give details of a potential feedback system that can reduce the drive beam jitter.
MOP44	Electron-Cloud Effects in the Positron Linacs of Future Linear Colliders	141
	D. Schulte, A. Grudiev, F. Zimmermann CERN, Geneva K. Oide KEK, Ibaraki
	Inside the rf structures of positron linacs for future linear colliders, electron multipacting may occur under the combined influence of the beam field and the electromagnetic rf wave. The multipacting could lead to an electron-cloud build up along the bunch train. We present simulation results of this effect for various proposed designs, and discuss possible consequences and eventual countermeasures.
	Transparencies
MOP45	A Potential Signal for Luminosity Optimisation in CLIC	144
	D. Schulte CERN, Geneva
	Luminosity optimisation will be challenging in the compact linear collider (CLIC) studied at CERN. In particular, the signals which can be used for luminosity optimisation need to be identified. The strong beam-beam interaction in CLIC will give rise to the emission of a few megawatts of beamstrahlung; this is a potential candidate for such a signal. In this paper luminosity optimisation using the beamstrahlung is attempted for realistically shaped bunches.
MOP46	Experimental Investigation of the Longitudinal Beam Dynamics in a Photo-Injector using a Two-Macroparticle Bunch	147
	R. Tikhoplav, A.C. Melissinos Rochester University, Rochester, New York N. Barov, D. Mihalcea Northern Illinois University, DeKalb, Illinois P. Piot FNAL, Batavia, Illinois
	We have developed a two-macroparticle bunch to explore the longitudinal beam dynamics through various component of the Fermilab/NICADD photoinjector laboratory. Such a two-macroparticle bunch is generated by splitting the photocathode drive laser impinging the photocathode. The presented method allows the exploration of rf-induced compression in the 1+1/2 cell rf-gun and in the 9-cell TESLA cavity. It also allows a direct measurement of the magnetic chicane bunch compressor parameters such as its momentum compaction. The measurements are compared with analytical and numerical models. Finally we present possible extension of the technique to investigate the transverse beam dynamics.
MOP47	Limiting Effects in the Round-To-Flat Beam Transformation	150
	Y.-E. Sun, K.-J. Kim Chicago University, Chicago, Illinois P. Piot FNAL, Batavia, Illinois
	The transformation of an angular-momentum-dominated beam into a flat beam was analyzed in Ref. [K.-J. Kim, Phys. rev. ST A&B, vol 6, 104002 (2003)]. The analysis was performed assuming that the beam and the transport channel upstream of the flat beam transformer are cylindrically symmetric and that the particle dynamics is symplectic. We extend the analysis to include chromatic and space-charge effects as well as asymmetries in the four dimensional transverse phase space distribution.
MOP48	Gamma and X-rays Production for Experiments at ELSA Facility	153
	J. Lemaire CEA/DAM, Bruyères-le-Châtel
	The ELSA facility is a high brightness 18 MeV electron source dedicated to electron radiation, gamma-rays and picosecond hard and soft X-rays. It consists of a 144 MHz RF photoinjector producing short bunches which are further accelerated to a final energy varying from 2 to 18 MeV thanks to three 433 MHz RF cavities. Former beam compression design used a half turn magnet compressor system. It has been recently replaced by a double alpha magnet compressor. Electron beams are now delivered to a new experimental room. We present the new panel of interests offered by this facility in term of gamma-ray and X-ray production.
MOP49	Status And Operating Experience of The TTF Coupler	156
	W.-D. Möller, D. Kostin DESY, Hamburg
	Five accelerating modules are installed in the VUV FEL linac so far. This includes 40 high power couplers connected to the superconducting cavities, eight in every module. All of them are processed and operated up to the cavity performance limits. The coupler processing procedure is described. The performance in relation to the test results on the coupler test stands are discussed.
	Transparencies
MOP62	Energy Spread in BTW Accelerating Structures at ELETTRA	159
	P. Craievich, R.J. Bakker, G. D'Auria, S.D. Di Mitri Sincrotrone Trieste S.C.p.A., Basovizza, Trieste
	The FEL project FERMI@ELETTRA will use the existing 1.0 GeV Linac, based on Backward Travelling Wave (BTW) structures, to produce VUV radiation between 100–10 nm. The project will be articulated in two different phases (100–40 nm/40–10 nm) and will require high quality beam with short bunches (500/160 fsec). Hence, wakefield effects have to be considered with respect to the electron beam quality. The single bunch energy spread induced by the short-range longitudinal wakefield is analyzed and results of start-to-end simulations are reported.
MOP63	Numerical Calculation of Coupling Impedances in Kicker Modules for Non-Relativistic Particle Beams	162
	B. Doliwa, T. Weiland TU Darmstadt, Darmstadt
	In the context of heavy-ion synchrotrons, coupling impedances in ferrite-loaded structures (e.g. fast kicker modules) are known to have a significant influence on beam stability. While bench measurements are feasible today, it is desirable to have the coupling impedances in hands already during the design process of the respective components. To achieve this goal, as a first step, we have carried out numerical analyses of simple ferrite-containing test systems within the framework of the Finite Integration Technique[1]. This amounts to solving the full set of Maxwell's equations in frequency domain, the particle beam being represented by an appropriate excitation current. With the resulting electromagnetic fields, one may then readily compute the corresponding coupling impedances. Despite the complicated material properties of ferrites, our results show that their numerical treatment is possible, thus opening up a way to determine a crucial parameter of kicker devices before construction. [1] Weiland, T., Electronics and Communication (AEÜ), Vol. 31 (1977), p. 116.
MOP64	Wire Measurement of Impedance of an X-Band Accelerating Structure	165
	N. Baboi DESY, Hamburg G. Bowden, V.A. Dolgashev, R.M. Jones, J. Lewandowski, S.G. Tantawi, J. Wang SLAC/ARDA, Menlo Park, California
	Several tens of thousands of accelerator structures will be needed for the next generation of linear collders known as the GLC/NLC (Global Linear Collider/Next Linear Collider). To prevent the beam being driven into a disruptive BBU (Beam Break Up) mode or at the very least, the emittance being signifcantly diluted, it is important to damp down the wakefield left by driving bunches to a manageable level. Manufacturing errors and errors in design need to be measurable and compared with predictions. We develop a circuit model of wire-loaded X-band accelerator structures. This enables the wakefield (the inverse transform of the beam impedance) to be readily computed and compared with the wire measurement. We apply this circuit model to the latest series of accelerating for the GLC/NLC. This circuit model is based upon the single-cell model developed in [1] extended here to complete, multi-cell structures. [1] R.M. Jones et al, 2003, Proc. PAC2003 (also SLAC-PUB 9871)
MOP65	Simple Theory of Thermal Fatigue Caused by RF Pulse Heating	168
	S. Kuzikov IAP, Nizhniy Novgorod
	The projects of electron-positron linear colliders imply that accelerating structures and other RF components will undergo action of extremely high RF fields. Except for breakdown threat there is an effect of the damage due to multi-pulse mechanical stress caused by Ohmic heating of the skin layer. A new theory of the thermal fatigue is considered. The theory is based on consideration of the quasi-elastic interaction between neighbor grains of metal due to the expansion of the thermal skin-layer. The developed theory predicts a total number of the RF pulses needed for surface degradation in dependence on temperature rise, pulse duration, and average temperature. The unknown coefficients in the final formula were found, using experimental data obtained at 11.4 GHz for the copper. In order to study the thermal fatigue at higher frequencies and to compare experimental and theoretical results, the experimental investigation of degradation of the copper cavity exposed to 30 GHz radiation is carried out now, basing on a 30 GHz free electron maser.
MOP66	Calculation of RF Properties of the Third Harmonic Cavity	171
	K. Rothemund, D. Hecht, U. van Rienen Rostock University, Faculty of Engineering, Rostock
	Recently a third harmonic structure has been proposed for the injector of the TTF-FEL to avoid nonlinear distortions in the longitudinal phase space. This structure, consists of four nine cell TESLA-like cavities. For the use of this structure in combination with the TTF-FEL it might be interesting to investigate higher order modes (HOM) in the structure and their effect on the beam dynamics. The complexity of the structure, four nine cell cavities assembled with four input couplers and eight HOM-couplers, results in an extremely high numerical effort for full 3D modelling. Therefor Coupled S-Parameter Calculation (CSC) [1] has been applied. This method is based on the scattering parameter description of the rf components found with field solving codes or analytically for components of special symmetry. This paper presents the results of the calculation of rf properties (e.g. scattering parameters, Q-values) of the complete four times nine cell structure equipped with all input- and HOM-couplers. [1] H.-W. Glock, K. Rothemund, U. van Rienen, CSC - A Procedure for Coupled S-Parameter Calculations, IEEE Trans. Magnetics, vol. 38, pp. 1173 - 1176, March 2002
MOP67	TESLA RF Power Coupler Thermal Calculations	174
	D. Kostin, M. Dohlus, W.-D. Möller DESY, Hamburg
	The main RF power coupler is one of the key elements of the accelerating module for the superconducting linac. It provides RF power to the cavity and interconnect different temperature layers in the module. Therefore statistical and dynamical thermal losses have to be optimized. Different operating modes as well as geometries were investigated. Coupler design optimization studies are carried out for TESLA and for the XFEL case. Especially long pulse operation for the X-FEL is being investigated.
MOP68	Ribbon Ion Beam Dynamics in Undulator Linear Accelerator	177
	E.S. Masunov, S.M. Polozov MEPhI, Moscow
	The possibility to use radio frequency undulator fields for ion beam focusing and acceleration in linac (UNDULAC-RF) is discussed. In periodical resonator structure the accelerating force is produced by the combination of two or more space harmonics of a longitudinal or a transverse undulator field. The particle motion equations in Hamilton form are carried out by means of smooth approximation. The analysis of 3D effective potential permits to find the conditions under which focusing and acceleration of the particles occur simultaneously. The analytical results are verified with a numerical simulation. Examples illustrating the efficiency of the proposed method of acceleration are given for longitudinal and transverse undulators. The results are compared with a conventional linac and the other possibility of ion beam acceleration in UNDULAC-E(M) where electrostatic and magnetic fields are used. E.S. Masunov, Technical Physics, Vol. 46, No.11, 2001, pp. 1433-1436.
MOP69	RF Control Modelling Issues for Future Superconducting Accelerators	180
	A. Hofler, J. R. Delayen TJNAF, Newport News, Virginia V. Ayvazyan, A. Brandt, S. Simrock DESY, Hamburg T. Czarski WUT, Warsaw T. Matsumoto KEK, Ibaraki
	The development of superconducting accelerators has reached a high level of maturity following the successes of ATLAS at Argonne, CEBAF at Jefferson Lab, the TESLA Test Facility at DESY and many other operational accelerators. As a result many new accelerators under development (e.g. SNS) or proposed (e.g. RIA) will utilize this technology. Covering all aspects from cw to pulsed rf and/or beam, non-relativistic to relativistic particles, medium and high gradients, light to heavy beam loading, linacs, rings, and ERLs, the demands on the rf control system can be quite different for the various accelerators. For the rf control designer it is therefore essential to understand these issues and be able to predict rf system performance based on realistic rf control models. This paper will describe the features that should be included in such models and present an approach which will drive the development of a generic rf system model.
MOP70	A Pass Band Performance Simulation Code of Coupled Cavities	183
	X. Tao, D. Tong TSINGHUA, Beijing
	A simulation code of accelerating cavities named PPSC is developed by the solutions of the microwave equivalent circuit equations. PPSC can give the pass band performance of periodic or non-periodic accelerating structures, such as the dispersion frequency and the reflection factor of the cavity, the field distribution of each mode and so on. The natural parameters of the structure, such as the number of the cavities, the resonant frequencies and Q-factors of each cavity, the coupling factor between two cavities, and the locations of the couplers, can be changed easily to see the different results of the simulation. The code is written based on MS Visual Basic under MS windows. With these, a user-friendly interface is made. Some simple examples was simulated and gave reliable results.
MOP71	Advanced Beam-Dynamics Simulation Tools for RIA	186
	T.P. Wangler, R. Garnett LANL, Los Alamos, New Mexico N. Aseev, P.N. Ostroumov ANL/Phys, Argonne, Illinois R. Crandall TechSource, Santa Fe, NM D. Gorelov, R.C. York NSCL, East Lansing, Michigan J. Qiang, R. Ryne LBNL, Berkeley, California
	Understanding beam losses is important for the high-intensity RIA driver linac. Small fractional beam losses can produce radioactivation of the beamline components that can prevent or hinder hands-on maintenance, reducing facility availability. Operational and alignment errors in the RIA driver linac can lead to beam losses caused by irreversible beam-emittance growth and halo formation. We are developing multiparticle beam-dynamics simulation codes for RIA driver-linac simulations extending from the low-energy beam transport (LEBT) line to the end of the linac. These codes run on the NERSC parallel supercomputing platforms at LBNL, which allow us to run simulations with large numbers of macroparticles for the beam-loss calculations. The codes have the physics capabilities needed for RIA, including transport and acceleration of multiple-charge-state beams, and beam-line elements such as high-voltage platforms within the linac, interdigital accelerating structures, charge-stripper foils, and capabilities for handling the effects of machine errors and other off-normal conditions. We will present the status of the work, including examples showing some initial beam-dynamics simulations.
MOP72	RF Breakdown in Accelerator Structures: From Plasma Spots to Surface Melting	189
	P.B. Wilson SLAC, Menlo Park, California
	Plasma spots are known to form at field emission sites in regions of high dc or rf electric field. Several mechanisms for the formation of plasma spots in an rf field have been proposed, and one such mechanism which fits experimental data is presented in this paper. However, a plasma spot by itself does not produce breakdown. A single plasma spot, with a lifetime on the order of 30 ns, extracts only a negligible amount of energy from the rf field. The evidence for its existence is a small crater, on the order of 10 microns in diameter, left behind on the surface. In this paper we present a model in which plasma spots act as a trigger to produce surface melting on a macroscopic scale (~0.1 mm²). Once surface melting occurs, a plasma that is capable of emitting several kiloamperes of electrons can form over the molten region. A key observation that must be explained by any theory of breakdown is that the probability of breakdown is independent of time within the rf pulse–breakdown is just as likely to occur at the beginning of the pulse as toward the end. In the model presented here, the conditions for breakdown develop over many pulses until a critical threshold for breakdown is reached.
	Transparencies
MOP73	Development of a Permanent Magnet ECR Source to Produce a 5 mA Deuteron Beam at CEA/Saclay	192
	R. Gobin, D.D. De Menezes, O. Delferriere, R. Ferdinand, F. Harrault CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex P.-Y. Beauvais, G. Charruau, Y. Gauthier CEA/DSM/DAPNIA, Gif-sur-Yvette N. Comte CEA/Saclay, Gif-sur-Yvette P. Lehérissier, J.Y. Pacquet GANIL, Caen
	The high intensity light ion source, SILHI, is an ECR ion source operating at 2.45 GHz which produces high intensity (over 100 mA) proton or deuteron beams at 95 keV. It has been moved in the IPHI building after a complete dismantling. At the beginning of 2003, after tuning the source parameters at standard values, the first extracted beam reached more than 70 mA within a few minutes. This encouraged us to propose a permanent magnet source based on the SILHI design to fit in with the injector of the Spiral2 project, requesting 5 mA of D⁺ beam with an energy of 40 keV and a normalized rms emittance lower than 0.2 π·mm·mrad. The new source has been recently assembled and the first beam (proton) extracted. After a brief source description, the preliminary results will be reported and discussed.
MOP74	Recent Results of the 2.45 GHz ECR Source Producing H^- Ions at CEA/Saclay	195
	R. Gobin, K. Benmeziane, O. Delferriere, R. Ferdinand, F. Harrault CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex A. Girard CEA DSM Grenoble, Grenoble
	Low frequency ECR plasma sources have demonstrated their efficiency, reproducibility and long life time for the production of positive light ions. In 2003, the new 2.45 GHz ECR test stand based on a pure volume H^- ion production, developed at CEA/Saclay, showed a dramatic increase of the H^- extracted ion beam. In fact, a stainless steel grid now divides the plasma chamber in two different parts: the plasma generator zone and the negative ion production zone. By optimizing the grid position and its potential with respect to the plasma chamber, the negative ion current reached close to 1 mA. Ceramic plates, covering the plasma chamber walls help electron density and lead to an optimisation of the ion production. A 50 % improvement has been observed. A new 6 kW magnetron RF generator now replaces the 1.2 kW previous one and the current will be soon plotted versus the RF power. New Langmuir probe measurements are also expected on both sides of the grid. The last results will be reported and discussed.
	Transparencies
MOP75	Hminus Distribution in the HERA RF-Volume Source	198
	J. Peters DESY, Hamburg
	The HERA RF-Volume Source is the only source available that delivers routinely an Hminus current of 40 mA without Cs. The production mechanism for Hminus ions in this type of source is still under discussion. Laser photodetachment measurements have been started at DESY in order to measure the Hminus distribution in the source. The measurements have also been done under extraction conditions at high voltage. The results of the measurements with and without extraction are a basis for the development of a theory for the transition between plasma and vacuum (sheath), a cornerstone for beam transport programs. Knowledge of the H^- distribution and where they are produced makes further source improvements possible.
MOP76	Ultra-High-Vacuum Problem for 200 keV Polarized Electron Gun with NEA-GaAs Photocathode	201
	T. Nakanishi, F. Furuta, M. Kuwahara, K. Naniwa, S. Okumi, M. Yamamoto, N. Yamamoto, K. Yasui DOP Nagoya, Nagoya H. Kobayakawa, Y. Takashima DOE Nagoya, Nagoya-City M. Kuriki, H. Matsumoto, M. Yoshioka KEK, Ibaraki
	For a polarized electron source based on photoemission from GaAs, a NEA (Negative Electron Affinity) surface makes an indispensable role to extract polarized electrons in conduction band into vacuum. The NEA surface is also considered as a best surface to provide a beam with a minimum initial beam-emittance. However, the NEA surface state is realized by a mono-layer of electric dipole moment (that is Ga(-)-Cs(+)) formed at the surface and thus it is easily degraded by desorption of harmful residual gas, desorption of harmful gas created by field emission from HV-cathodes and ion back-bombardment. In order to reduce the effects of (a) and (c), extremely good UHV is required. Presently total pressure of 4·10^-12 torr and respective partial pressures of 3·10^-13 torr and 4·10^-13 torr for H₂O and CO₂ were achieved at our gun chamber. Field emission dark current must be extremely suppressed to reduce the effect of (c). The maximum field gradient of 7.8 MV/m is applied for electrode envelope (3.0 MV/m for cathode surface) at 200 kV DC bias-voltage, but total dark current was suppressed below 1 nA for our electrodes. The NEA lifetime under these conditions will be reported at the conference.
MOP77	Design Parameters of the Normal Conducting Booster Cavity for the PITZ-2 Test Stand	204
	V.V. Paramonov, N.I. Brusova, A.I. Kvasha, A. Menshov, O.D. Pronin, A.K. Skasyrskaya, A.A. Stepanov RAS/INR, Moscow A. Donat, M. Krasilnikov, A. Oppelt, F. Stephan DESY Zeuthen, Zeuthen K. Flöttmann DESY, Hamburg
	The normal conducting booster cavity is intended to increase the electron bunch energy in the Photo Injector Test (DESY, Zeuthen) stage 2 experiments. The normal conducting cavity is selected due to infrastructure particularities. The L-band cavity is designed to provide the accelerating gradient up to 14 MV/m with the total input RF power 8.6 MW, RF pulse length up to 900 mks and repetition rate 5 Hz. The multi-cell cavity is based on the CDS compensated accelerating structure with the improved coupling coefficient value. The main design ideas and decisions are described briefly together with cavity parameters - RF properties, cooling and pumping circuits.
MOP80	Development of Adaptive Feedback Control System of Both Spatial and Temporal Beam Shaping for UV-Laser Light Source for RF Gun	207
	H. Tomizawa, T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, A. Mizuno, S. Suzuki, T. Taniuchi, K. Yanagida JASRI-SPring-8, Hyogo F. Matsui FKLAB, Fukui City
	The ideal spatial and temporal profiles of a shot-by-shot single laser pulse are essential to suppress the emittance growth of the electron beam from a photo-cathode rf gun. We have been developing highly qualified UV-laser pulse as a light source of the rf gun for an injector candidate of future light sources. The gun cavity is a single-cell pillbox, and the copper inner wall is used as a photo cathode. The electron beam was accelerated up to 4.1 MeV at the maximum electric field on the cathode surface of 175 MV/m. For emittance compensation, two solenoid coils were used. As the first test run, with a microlens array as a simple spatial shaper, we obtained a minimum emittance value of 2 π·mm·mrad with a beam energy of 3.1 MeV, holding its charge to 0.1 nC/bunch. In the next test run, we prepared a deformable mirror for spatial shaping, and a spatial light modulator based on fused-silica plates for temporal shaping. We applied the both adaptive optics to automatically shape the both spatial and temporal UV-laser profiles with a feedback routine at the same time. We report herein the principle and developing process of our laser beam quality control system.
MOP81	Analysis of the Qualification-Tests Performance of the Superconducting Cavities for the SNS Linac	210
	J. R. Delayen, J. Mammosser, O. Ozelis Jefferson Lab, Newport News, Virginia
	Thomas Jefferson National Accelerating Facility (Jefferson Lab) is producing superconducting radio frequency (SRF) cryomodules for the Spallation Neutron Source (SNS) cold linac. This consists of 11 medium-beta (β=0.61) cyomodules of 3 cavities each, and 12 high-beta (β=0.81) cryomodules of 4 cavities each. Before assembly into cavity strings the cavities undergo individual qualification tests in a vertical cryostat (VTA). In this paper we analyze the performance of the cavities during these qualification tests, and attempt to correlate this performance with cleaning, assembly, and testing procedures. We also compare VTA performance with performance in completed cryomodules.
MOP82	SRF Cavity and Materials R&D at Fermilab	213
	N. Khabiboulline, P. Bauer, L. Bellantoni, T. Berenc, C. Boffo, R. Carcagno, C. Chapman, H. Edwards, L. Elementi, M. Foley, E. Hahn, D. Hicks, D. Mitchell, A. Rowe, N. Solyak, I. Terechkine FNAL, Batavia, Illinois A. Gurevich, M. Jewell, D. C. Larbalestier, P. Lee, A. Polyanskii, A. Squitieri UW-Madison/ASC, Madison, Wisconsin
	Two 3.9 GHz superconducting RF cavities are under development at FNAL for use in the upgraded Photoinjector Facility. A TM110 mode cavity will provide streak capability for bunch slice diagnostics, and a TM010 mode cavity will provide linearization of the accelerating gradient before compression for better emittance. The status of these two efforts and a review of the FNAL infrastructure development will be given.
MOP84	First Cryogenic Tests with JLab's new Upgrade Cavities*	216
	P. Kneisel, G. Ciovati, G. Myneni, G. Wu Jefferson Lab, Newport News, Virginia J. Halbritter FZ Karlsruhe, Karlsruhe J. Sekutowicz DESY, Hamburg
	For the upgrade of CEBAF to 12 GeV two types of 7-cell cavities have been developed: the High Gradient type (HG) has been optimized with respect to the ratio of E_peak/E_acc and for the Low Loss (LL) type the shunt impedance has been maximized. Each cavity type features four DESY type coaxial HOM couplers and a waveguide input coupler. Design goals for these cavities have been set to E_acc = 20 MV/m with a Q-value at 2.05 K of Q₀ = 8·10⁹. A niobium prototype of each cavity has been fabricated at JLab and in a first test the HG cavity has been evaluated at cryogenic temperatures after appropriate buffered chemical polishing. Data for Q(E) were taken at several temperatures after R(T) was measured during initial pump down. In addition the pressure sensitivity as well as the Lorentz force detuning were evaluated. The damping of approximately 20 High Order Modes was measured to verify the room temperature data. Measurements on the LL prototype are in progress. We present in this contribution a summary of measured results of tests we performed on the new proposed shapes of the upgrade cavities.
MOP85	Influence of Ta Content in High Purity Niobium on Cavity Performance: Preliminary Results*	219
	P. Kneisel, G. Myneni Jefferson Lab, Newport News, Virginia T. Carneiro RMC, Bridgeville M. Imagumbai CBMM, Tokyo Chr. Klinkenberg NPC, Düsseldorf D. Proch, W. Singer, X. Singer DESY, Hamburg
	In a previous paper* a program designed to study the influence of the residual tantalum content on the superconducting properties of pure niobium metal for RF cavities was outlined. The main rationale for this program was based on a potential cost reduction for high purity niobium, if a less strict limit on the chemical specification for Ta content, which is not significantly affecting the RRR–value, could be tolerated for high performance cavities. Four ingots with different Ta contents have been melted and transformed into sheets. In each manufacturing step the quality of the material has been monitored by employing chemical analysis, neutron activation analysis, thermal conductivity measurements and evaluation of the mechanical properties. The niobium sheets have been scanned for defects by an eddy current device. From three of the four ingots—Ta contents 100, 600 and 1,200 wppm—two single cell cavities each of the CEBAF variety have been fabricated and a series of tests on each cavity with increasing amount of material removal have been performed. This contribution reports about the results from different tests and gives an analysis of the data. *T. Carneiro et al; http://conference.kek.jp/SRF2001/
MOP86	Cold Test Results of the ISAC-II Medium Beta High Gradient Cryomodule	222
	R.E. Laxdal, Y. Bylinskii, G.S. Clark, K. Fong, A.K. Mitra, R. L. Poirier, B. Rawnsley, T. Ries, I. Sekatchev, G. Stanford, V. Zvyagintsev TRIUMF, Vancouver
	Many proposals (RIA, Eurisol, ISAC-II) are emerging for a new generation of high gradient heavy ion accelerators. The ISAC-II medium beta cryomodule represents the first realized application that encorporates many new techniques to improve the performance over machines presently being used for beam delivery. The machine lattice, compatible with multi-charge acceleration, uses high field (9T) superconducting solenoids with bucking coils for active fringe field compensation. The bulk niobium quarter wave medium beta cavity produces 6 MV/m over an effective length of 18cm with a peak surface field of ~30 MV/m. TRIUMF has developed a mechanical tuner capable of both coarse (kHz) and fine (Hz) frequency adjustments of the cavity. The demonstrated tuner resolution is better than 0.1 μm (0.6 Hz). A new rf coupling loop has been developed that operates at 200 Watts forward power with less than 0.5 Watt of power being added to the helium load. Cold alignment in ISAC-II has been done with rf pick-ups using a stretched wire technique. Finally all cryomodule and testing has been done in a clean environment. The alignment cryogenic, solenoid and rf performance will be presented.
	Transparencies
MOP87	Conceptual Layout of the European X-FEL Linear Accelerator Cryogenic Supply	225
	B. Petersen, H. Lierl, A. Zolotov DESY, Hamburg
	As a source for the European x-ray free electron laser (European X-FEL project) at DESY a superconducting linear accelerator will deliver a pulsed electron beam of about 20 GeV. A conceptual layout for the cryogenic supply of the linac is presented. The linac will consist of about 1000 superconducting niobium 1.3 GHz 9-cell cavities, which will be cooled in a liquid helium bath at a temperature of 2 K. Eight cavities and one superconducting magnet package will be assembled to a cryomodule of 12.2 m length. The cryomodules are equipped with two thermal shields at a 5 K and 80 K temperature level respectively. The linac of about 1.6 km length will be divided in 10 cryogenic sub units. Each sub unit will consist of 12 cryomodules. In addition to the main linac, two injector sections have to be supplied separately by means of helium refrigerators and a related helium distribution system.
MOP88	RF Coupler Design for the TRIUMF ISAC-II Superconducting Quarter Wave Resonator	228
	R. L. Poirier, K. Fong, P. Harmer, R.E. Laxdal, A.K. Mitra, I. Sekatchev, B. Waraich, V. Zvyagintsev TRIUMF, Vancouver
	An RF Coupler for the ISAC-II medium beta (β=0.058 and 0.071) superconducting quarter wave resonators was designed and tested at TRIUMF. The main goal of this development was to achieve stable operation of superconducting cavities at high acceleration gradients and low thermal load to the helium refrigeration system. The cavities will operate at 6 MV/m acceleration gradient in overcoupled mode at a forward power 200 W at 106 MHz. The overcoupling provides ±20 Hz cavity bandwidth, which improves the stability of the RF control system for fast helium pressure fluctuations, microphonics and environmental noise. Choice of materials, cooling with liquid nitrogen, aluminum nitride RF window and thermal shields insure a small thermal load on the helium refrigeration system by the Coupler. An RF finger contact which causedμdust in the coupler housing was eliminated without any degradation of the coupler performance. RF and thermal calculations, design and test results on the coupler are presented in this paper.
MOP89	A Wire Position Monitor System for the ISAC-II Cryomodule Components Alignment	231
	B. Rawnsley, Y. Bylinskii, G. Dutto, K. Fong, R.E. Laxdal, T. Ries TRIUMF, Vancouver D. Giove INFN/LASA, Segrate (MI)
	TRIUMF is developing ISAC-II, a superconducting (SC) linac. It will comprise 9 cryomodules with a total of 48 niobium cavities and 12 SC solenoids. They must remain aligned at liquid He temperatures: cavities to ±400 μm and solenoids to ±200 μm after a vertical contraction of ~4 mm. A wire position monitor (WPM) system based on a TESLA design has been developed, built, and tested with a prototype cryomodule. The system is based on the measurement of signals induced in pickups by a 215 MHz signal carried by a wire through the WPMs. The wire is stretched between the warm tank walls parallel to the beam axis providing a position reference. The sensors, one per cavity and two per solenoid, are attached to the cold elements to monitor their motion during pre-alignment, pumping and cool down. A WPM consists of four 50 Ω striplines spaced 90° apart. A GaAs multiplexer scans the WPMs and a Bergoz card converts the RF signals to DC X and Y voltages. National Instruments I/O cards read the DC signals. The data acquisition is based on a PC running LabVIEW. System accuracy is ~7 μm. The paper describes system design, WPM calibration and test results.
MOP92	Simulation of the RF Coupler for TRIUMF ISAC-II Superconducting Quarter Wave Resonators	234
	V. Zvyagintsev TRIUMF, Vancouver
	The inductive RF coupler for the TRIUMF ISAC-II 106 MHz superconducting accelerating quarter wave resonators was used as a basis for the simulation model of stationary transmission processes of RF power and thermal fluxes. Electromagnetic simulation of the coupler was done with ANSOFT HFSS code. Transmission line theory was used for electromagnetic wave calculations along the drive line to the Coupler. An analogy between electric and thermal processes allows the thermal calculations to be expressed in terms of electrical circuits. The data obtained from the simulation are compared to measured values on the RF coupler.