LINAC 2004 - List of Keywords

A B C D E F G H I K L M O P Q R S T U V

simulation

Paper	Title	Other Keywords	Page
MO201	Linac Coherent Light Source (LCLS) – Accelerator System Overview	linac, damping, feedback, free-electron-laser	7
	P. Krejcik, Z. Huang, J. Wu SLAC, Menlo Park, California P. Emma SLAC/ARDA, Menlo Park, California
	The Linac Coherent Light Source (LCLS) will be the world's first x-ray free-electron laser (FEL). Pulses of LCLS x-ray FEL will be several orders of magnitude brighter and shorter than most existing sources. These characteristics will enable frontier new science in several areas. To ensure the vitality of FEL lasing, it is critical to preserve the high quality of the electron beam during the acceleration and compression. We will give an overview of the LCLS accelerator system. We will address design essentials and technique challenges to satisfy the FEL requirements. We will report studies on the microbunching instability suppression via a Laser-Heater. The studies clearly prove the necessary of adding the Laser-Heater and show how effectively this Laser-Heater suppresses the instability by enhancing the Landau damping. We will report how to minimize the sensitivity of the final energy spread and the peak current to various system ‘jitters’. To minimize this sensitivity, a feedback system is required together with other diagnostics. With all these considerations, full start-to-end simulations show saturation at 1.5 Å, though the LCLS is expected to be a very challenging machine.
	Transparencies

MOP07	High Current Beam Transport to SIS18	emittance, injection, ion, space-charge	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	ion, quadrupole, emittance, space-charge	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

MOP10	The IH Cavity for HITRAP	emittance, rfq, ion, bunching	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	rfq, ion, linac, emittance	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.

MOP17	Design of the SPES-1 LEBT	electron, rfq, ion, proton	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	coupling, linac, vacuum, alignment	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	rfq, linac, beam-transport, injection	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	impedance, linac, proton, resonance	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.

MOP28	A Study of Higher-Band Dipole Wakefields in X-Band Accelerating Structures for the G/NLC	dipole, emittance, linac, impedance	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

MOP40	A Study Of Coupler-Trapped Modes In X-Band Linacs for the GLC/NLC	emittance, linear-collider, collider, linac	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.

MOP42	Linac Alignment and Frequency Tolerances from the Perspective of Contained Emittances for the G/NLC	emittance, alignment, linac, dipole	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	linac, luminosity, feedback, lattice	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	electron, linac, positron, acceleration	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	luminosity, linac, photon, emittance	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	electron, booster, laser, bunching	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	emittance, quadrupole, chromatic-effects, gun	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.

MOP62	Energy Spread in BTW Accelerating Structures at ELETTRA	linac, single-bunch, electron, target	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	coupling, impedance, kicker, synchrotron	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.

MOP67	TESLA RF Power Coupler Thermal Calculations	linac, background	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.

MOP70	A Pass Band Performance Simulation Code of Coupled Cavities	linac, coupling, RF-structure, beam-loading	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	linac, beam-losses, rfq, acceleration	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	plasma, electron, site, radio-frequency	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	extraction, plasma, emittance, permanent-magnet	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.

MOP81	Analysis of the Qualification-Tests Performance of the Superconducting Cavities for the SNS Linac	linac, radiation, electron, ion	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.

MOP88	RF Coupler Design for the TRIUMF ISAC-II Superconducting Quarter Wave Resonator	coupling, acceleration, superconductivity, damping	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.

MOP92	Simulation of the RF Coupler for TRIUMF ISAC-II Superconducting Quarter Wave Resonators	coupling, impedance, cryogenics, acceleration	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.

TU101	Engineering and Building RF Structures - The Works	rfq, vacuum, linac, radio-frequency	237
	D. Schrage LANL, Los Alamos, New Mexico
	The translation of the physics designs of linear accelerators into engineering and manufacturing requirements is discussed. The stages of conceptual design, prototyping, final design, construction, and installation are described for both superconducting (LANL β = 0.175 Spoke Cavity) and normal-conducting (APT/LEDA 6.7 MeV RFQ) accelerators. An overview of codes which have linked accelerator cavity and thermal/structural analysis modules is provided.
	Transparencies

TU203	High Pressure, High Gradient RF Cavities for Muon Beam Cooling	emittance, radiation, collider, vacuum	266
	R. P. Johnson, M. Popovic FNAL, Batavia, Illinois M.M. Alsharo'a, R.E. Hartline, M. Kuchnir, T.J. Roberts Muons, Inc., Batavia C. M. Ankenbrandt, A. Moretti Fermilab, Batavia, Illinois K. Beard, A. Bogacz, Y.S. Derbenev Jefferson Lab, Newport News, Virginia D. M. Kaplan, K. Yonehara IIT, Chicago, Illinois
	High intensity, low emittance muon beams are needed for new applications such as muon colliders and neutrino factories based on muon storage rings. Ionization cooling, where muon energy is lost in a low-Z absorber and only the longitudinal component is regenerated using RF cavities, is presently the only known cooling technique that is fast enough to be effective in the short muon lifetime. RF cavities filled with high-pressure hydrogen gas bring two advantages to the ionization technique: the energy absorption and energy regeneration happen simultaneously rather than sequentially, and higher RF gradients and better cavity breakdown behavior are possible than in vacuum due to the Paschen effect. These advantages and some disadvantages and risks will be discussed along with a description of the present and desired RF R&D efforts needed to make accelerators and colliders based on muon beams less futuristic.
	Transparencies

TUP04	The SPL Front End: A 3 MeV H^- Test Stand at CERN	linac, rfq, proton, quadrupole	294
	R. Garoby, L. Bruno, F. Caspers, J. Genest, K. Hanke, M. Hori, D. Kuchler, A.M. Lombardi, M. Magistris, A. Millich, M. Paoluzzi, C. Rossi, E.Zh. Sargsyan, M. Silari, T. Steiner, M. Vretenar CERN, Geneva P.-Y. Beauvais CEA/DSM/DAPNIA, Gif-sur-Yvette
	In the frame of the SPL (Superconducting Proton Linac) study at CERN, a new 160 MeV proton injector for the CERN PS Booster is presently under development. This linear accelerator (Linac4) would not only be a first step towards a future, multi-MW superconducting linac, but would also improve in the medium term both the beam availability and beam quality for CERN’s proton users. Within the framework of the Linac 4 study and with the support of the EU funded Joint Research Activity HIPPI, a 3 MeV test stand is under construction at CERN. This test stand will explore some of the most critical issues of the linac, such as the beam dynamics at low energy, with special emphasis on the Chopper line that has been designed to generate the required time structure of the beam, to clean the beam halo, and to match it to the subsequent RF structures. In this context, a new Beam Shape and Halo Monitor is under construction. The beam acceleration will be performed by an RFQ that is being developed in France within the IPHI collaboration between CEA and CNRS. Moreover, the test stand will be equipped with an additional 1 MW RF klystron to test different RF structures that are being designed at 352 MHz as preliminary studies for the Linac4. High Intensity Pulsed Proton Injectors
	Transparencies

TUP05	Beam Dynamics for a new 160 MeV H^- Linac at CERN (LINAC4)	linac, emittance, rfq, quadrupole	297
	F. Gerigk CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon E. Benedico Mora, A.M. Lombardi, E.Zh. Sargsyan, M. Vretenar CERN, Geneva
	LINAC4 is a normal conducting H^- linac proposed at CERN to provide a higher proton flux to the CERN accelerator chain. It should replace the existing LINAC2 as injector for the PS booster. The same machine can also operate in the future as the front end of the SPL, a 2.2 GeV superconducting linac with 1.8 mA average current. At present the test set-up for LINAC4 consists of a Radio Frequency Quadrupole (RFQ), a chopper line, a Drift Tube Linac (DTL), and Cell Coupled DTL (CCDTL) operating at 352.2 MHz and finally a Side Coupled Linac (SCL) at 702.2 MHz. This paper discusses the overall beam dynamics concept, presents the optics for the different sections of the machine and compares end-to-end simulations realised with two tracking codes (PATH and IMPACT). Estimates of beam loss due to various error sources are presented and the challenging features in the current design are highlighted.
	Transparencies

TUP07	A Linac-to-Booster Injection Line for Transverse Matching and Correlated Injection Painting	booster, injection, linac, focusing	303
	R. Garnett, L. Rybarcyk LANL, Los Alamos, New Mexico
	In this paper we discuss a compact linac-to-booster ring transfer line originally proposed for the Los Alamos Advanced Hydrotest Facility design to vertically inject a 157 MeV H^- beam from the linac into a 10 GeV booster. TRACE 3-D and PARMILA simulations were used to demonstrate the performance of the transfer line to deliver the required transverse beam to the foil while also allowing correlated longitudinal injection painting. Schemes for both transverse and longitudinal matching are important for high-intensity ring applications where low beam loss operation is desirable. The main features of the beam line layout, a proposed longitudinal painting scheme, and the simulation results will be discussed.

TUP18	Beam Dynamics Issues of SPES-1 Linac	linac, quadrupole, rfq, emittance	330
	E. Fagotti INFN Milano, Milano M. Comunian, A. Palmieri, A. Pisent INFN/LNL, Legnaro, Padova
	An Independent Superconducting Cavity Linac able to accelerate 10 mA CW proton beam up to 20 MeV has been studied for the SPES-1 project. This paper presents the results of beam dynamics studies through SPES linac including mapped fields effects on cavities and magnets.

TUP19	Characterization of Beam Parameter and Halo for a High Intensity RFQ Output under Different Current Regimes	rfq, emittance, space-charge, proton	333
	E. Fagotti INFN Milano, Milano M. Comunian, A. Palmieri, A. Pisent INFN/LNL, Legnaro, Padova
	The characterization of the beam distribution at the exit of a high intensity RFQ is a crucial point in view of a correct simulation of beam behavior in the following linac structure. At this scope we need to know the beam halo quantification as a function of the input beam and RFQ parameters. In this paper, the description of Beam halo based upon moments of the particle distribution at the exit of the TRASCO-RFQ is given.

TUP21	Beam Dynamics Design of J-PARC Linac High Energy Section	linac, injection, beam-transport, rfq	339
	M. Ikegami, T. Kato, S. Noguchi KEK, Ibaraki H. Ao, Y. Yamazaki JAERI/LINAC, Ibaraki-ken K. Hasegawa, T. Ohkawa, A. Ueno JAERI, Ibaraki-ken N. Hayashizaki TIT, Tokyo V.V. Paramonov RAS/INR, Moscow
	J-PARC linac consists of a 3 MeV RFQ linac, a 50 MeV DTL (Drift Tube Linac), a 190 MeV SDTL (Separate-type DTL), and a 400 MeV ACS (Annular-Coupled Structure) linac. Recently, the beam dynamics design of the ACS part has been slightly modified to reduce construction cost. Namely, the number of klystron modules are reduced from 23 to 21, and the number of accelerating cells in one klystron module is increased from 30 to 34 to maintain the total energy gain. This design change curtails the margin for RF power by around 5 %, and the total length of the ACS section is nearly unchanged. The beam matching section between SDTL and ACS is also revised correspondingly. These modifications of the design are described in this paper together with 3D particle simulation results for the new design.

TUP22	A Simulation Study on Chopper Transient Effects in J-PARC Linac	beam-losses, linac, emittance, injection	342
	M. Ikegami KEK, Ibaraki Y. Kondo, T. Ohkawa, A. Ueno JAERI, Ibaraki-ken
	J-PARC linac has an RF chopper system to reduce uncontrolled beam loss in the succeeding ring injection. The chopper system is located in MEBT (Medium Energy Beam Transport line) between a 3 MeV RFQ and a 50 MeV DTL, and consists of two RFD (Radio-Frequency Deflection) cavities and a beam collector. During the rising- and falling-times of the RFD cavities, the beams are half-kicked and cause excess beam loss downstream. In this paper, the behavior of these half-kicked beams is examined with 3D PARMILA simulations, and resulting beam loss is estimated.
	Transparencies

TUP23	A Simulation Study on Error Effects in J-PARC Linac	emittance, linac, injection, beam-losses	345
	M. Ikegami KEK, Ibaraki Y. Kondo, T. Ohkawa, A. Ueno JAERI, Ibaraki-ken
	In high-current proton linacs, prevention of excess beam loss is essentially important to enable hands-on maintenance. In addition, requirements on the momentum spread and transverse emittance are quite severe for J-PARC linac to realize effective injection to the succeeding RCS (Rapid Cycling Synchrotron). As losses and beam-quality deterioration are believed to be mainly caused by various errors, such as misalignment, RF mistuning, etc, it is essentially important to perform particle simulations for J-PARC linac with as realistic errors as possible to estimate their effects. In this paper, effects of realistic errors on beam loss and beam-quality deterioration in J-PARC linac are examined with a systematic 3D simulations with PARMILA. Necessity of transverse collimation is also discussed.

TUP29	Proton Beam Dynamics of the SARAF Linac	linac, emittance, proton, beam-losses	354
	A. Shor, D. Berkovits, G. Feinberg, S. Halfon SOREQ, Yavne K. Dunkel ACCEL, Bergisch Gladbach
	We have performed proton beam dynamics simulation for the SARAF, 40 MeV and 4 mA, linac. The calculation is using the GPT code and includes effects of space charge. It demonstrates that for an initial 6D Waterbag distribution beam, a tune can be obtained with longitudinal rms emittance growth of about 10 % and transverse normalized rms emittance growth of 20%, and a transverse beam envelope of 5000 macro-particle well within the linac beam pipe. Beam loss is estimated by fitting a radial Gaussian to the particle distribution along the linac. A 1 nA beam envelope is obtained by extrapolating the tail of the radial-Gaussian function. The 1nA beam envelope is still well within the beam bore radius. Benchmark simulation with a 6D Gaussian initial distribution, with the same rms quantities, exhibits a more extended tail that may result in a higher beam loss. This point will receive a further study.
	Transparencies

TUP41	Multi-Bunch Beam Dynamics Studies for the European XFEL	emittance, linac, electron, collider	357
	N. Baboi DESY, Hamburg
	In the X-ray free electron laser planned to be built at DESY (TESLA XFEL) the acceleration of the electron bunches will be made with 9-cell superconducting cavities. These cavities have been initially developed within the TESLA linear collider study. The impact of the higher order modes (HOM) has been shown to be within the acceptable beam dynamics limits for the collider. For the XFEL the dynamics is relaxed from point of view of multi-bunch effects (e.g. shorter length, higher emittance). However the lower energy and different time structure of the beam make the study of the HOM effects in the XFEL linac necessary. Multi-bunch beam dynamics studies are ongoing. The results of the HOM measurements at the TESLA Test Facility are used. Several options for the beam structure, as necessary for various applications, are studied. The results will be discussed.
	Transparencies

TUP43	The Superconducting CW Driver Linac for the BESSY-FEL User Facility	linac, emittance, gun, beam-loading	363
	J. Knobloch BESSY GmbH, Berlin
	A CW FEL User Facility for the VUV to soft X-ray spectral range based on a cascaded HGHG-FEL scheme is planned at the BESSY site. The Technical Design Report has recently been submitted to the German Wissenschaftsrat. Beam acceleration to 2.3 GeV is provided by a 144-cavity superconducting driver linac based on TESLA technology modified for CW operation. Initially, a high-rep-rate normal-conducting photoinjector will be used but a fully CW superconducting version is being investigated for a future upgrade. Bunch compression to 2 kA peak current is achieved in a three-stage scheme involving two bunch compressors and an arc. An overview of the linac layout, including the rf and cryogenic distribution, is provided here. We also discuss the impact of CW operation and the modifications to the TESLA technology that are necessary. Predictions of the linac performance are also given.
	Transparencies

TUP48	Progress Report on the Flat Beam Experiment at the Fermilab/Nicadd Photoinjector Laboratory	laser, emittance, cathode, quadrupole	378
	Y.-E. Sun, K.-J. Kim Chicago University, Chicago, Illinois N. Barov Northern Illinois University, DeKalb, Illinois K. Desler DESY, Hamburg H. Edwards, P. Piot, J. Santucci, J. Wennerberg FNAL, Batavia, Illinois M. Huening Fermilab, Batavia, Illinois S. Lidia LBNL/AFR, Berkeley, California R. Tikhoplav Rochester University, Rochester, New York
	We report on our present progress toward the investigation on the generation of flat beam from an incoming angular-momentum-dominated beam, along with the associated diagnostics development. We focus on the evolution of the four-dimensional beam matrix upstream and downstream of the round-to-flat beam transformer. Finally we compare our latest experimental results with numerical and analytical models.

TUP49	Simulations of the Ion-Hose Instability for DARHT-II Long-Pulse Experiments	induction, linac, electron, resonance	381
	K. C. D. Chan, C. Ekdahl LANL, Los Alamos, New Mexico C. Genoni, P. Hughes MRC, Albuquerque, NM
	Ion-hose effect has been described extensively in literatures. Computer simulations of the effect typically use particle-in-cell (PIC) computer codes or codes using the spread-mass formulation [1]. PIC simulations, though offering more reliable results, will require extended running time in large computers To support commissioning experiments in the DARHT-II induction linac in Los Alamos National Laboratory, we have modified a spread-mass code so that we can survey quickly the parameter space for the experiment. It can also be used to provide quick answers during experiment. The code was originally written by Genoni from Mission Research Corporation (MRC) for constant linac parameters. We have modified it so that parameters can have dependence along the length of the linac. In this paper, we will describe simulation results using this code for the DARHT-II commissioning experiment and also our benchmarking results comparing to LSP, a PIC code from MRC. [1] T. C. Genoni and T. P. Hughes, "Ion-hose instability in a long-pulselinear induction accelerator", PRST-AB, 6, 030401 (2003)

TUP53	Temporal Profile of the LCLS Photocathode Ultraviolet Drive Laser Tolerated by the Microbunching Instability	undulator, laser, damping, emittance	390
	J. Wu, Z. Huang SLAC, Menlo Park, California M. Borland ANL, Argonne, Illinois P. Emma SLAC/ARDA, Menlo Park, California C. Limborg SLAC/SSRL, Menlo Park, California
	The high quality LCLS electron beam generated in the photoinjector is subject to all possible instabilities in the downstream acceleration and compression. The instability can be initiated by any possible density modulation of the electron beam when it is generated at the photocathode. In this note, we prescribe the tolerance on the initial electron beam density modulation possibly introduced by the ultraviolet (uv) laser at the cathode. Our study shows that the initial rms density modulation of the electron beam at the photocathode shall be less than 5 % to ensure the FEL lasing and saturation.

TUP56	Simulation of RF Breakdown Effects on NLC Beam	electron, linac, acceleration, ion	396
	V.A. Dolgashev SLAC/ARDB, Menlo Park, California T.O. Raubenheimer SLAC/NLC, Menlo Park, California
	The linacs of the Next Linear Collider (NLC) will contain several thousand traveling wave X-Band accelerator structures operating at input power of about 60 MW. At this input power prototypes of NLC structures have breakdown rates lower than one breakdown in ten hours. RF breakdowns disrupt flow of energy inside the structure and create arcs with electron and ion currents. Electromagnetic fields of these currents interact with the NLC beam. We simulated deflection of the NLC beam caused by breakdown currents using the particle-in-cell code MAGIC. In this paper we present modeling considerations and simulation results.

TUP58	Alternative Linac Layout for European XFEL Project	linac, emittance, space-charge, gun	399
	Y. Kim, K. Flöttmann, T. Limberg DESY, Hamburg Y. Kim, D. Son CHEP Korea, Daegu
	To satisfy required beam parameters and to increase the jitter tolerance, we have designed an alternative linac layout with two bunch compressor stages for the European XFEL project. In this paper, we describe start-to-end (S2E) simulation of the alternative linac layout for the European XFEL project, and compare its results with our current linac layout with one bunch compressor stage.

TUP59	Extraction of High Charge Electron Bunch from the ELSA RF Injector - Comparison Between Simulation and Experiment	space-charge, gun, laser, electron	402
	J. Lemaire, P. Balleyguier, A. Binet, J.M. Lagniel, V. Le Flanchec, N. Pichoff CEA/DAM, Bruyères-le-Châtel R. Bailly-Salins, M. Millerioux, Chr. Quine CEA/DIF/DPTA/SP2A, Bruyeres-le-Chatel
	A new scheme based on a photoinjector and a RF linear accelerator operating at 352 MHz has been recently proposed as a versatile radiographic facility. Beam pulses of 60 ns duration contain 20 succesive electron bunches which will be extracted at 2.5 MeV from a photoinjector then accelerated through the next structure to the final energy of 51 MeV. Bunches carrying 100 nC are required for this purpose. As a first demonstrating step, 50 nC electron bunches have been produced and accelerated to 2.5 MeV with the 144 MHz ELSA photoinjector at Bruyères le Chatel. For this experiment, we compare the results and the numerical simulations made with PARMELA, MAGIC and MAFIA codes.

TUP64	Bunch Length Measurements at LEBRA	electron, linac, klystron, undulator	411
	K. Yokoyama KEK, Ibaraki K. Hayakawa, Y. Hayakawa, K. Nakao, I. Sato, T. Tanaka LEBRA, Funabashi
	The bunch length of the electron beam from the FEL linac at LEBRA (Laboratory for Electron Beam Research and Application) was estimated from the phase ellipse coefficient which is deduced from the dependence of the beam spread on the accelerating phase. The bunch length of FWHM was estimated approximately 0.33 mm from the results of the experiments. Besides, the pulse length of the FEL lights around the wavelength of 1.5 μm was measured by means of the autocorrelation. The pulse length was less than 0.06 mm according to the number of interfacial waves. These results indicate that the pulse length of the FEL lights isn’t equivalent to the electron bunch length.

TUP65	RF Tuning Schemes for J-PARC DTL and SDTL	linac, klystron, injection, diagnostics	414
	M. Ikegami KEK, Ibaraki Y. Kondo, A. Ueno JAERI, Ibaraki-ken
	J-PARC linac consists of a 3 MeV RFQ linac, a 50 MeV DTL (Drift Tube Linac), a 190 MeV SDTL (Separate-type DTL), and a 400 MeV ACS (Annular-Coupled Structure) linac. In high-current proton linacs, precise tuning of RF amplitude and phase is indispensable to reduce uncontrolled beam loss and beam-quality deterioration. Especially, accurate RF tuning is essential for J-PARC linac, because requirement for the momentum spread is extremely severe to enable effective injection to the succeeding RCS (Rapid Cycling Synchrotron). In this paper, planned tuning schemes for the DTL and SDTL are presented together with the beam diagnostic layout for the tuning.

TUP66	An Alternate Scheme for J-PARC SDTL Tuning	emittance, injection, linac, rfq	417
	M. Ikegami KEK, Ibaraki Y. Kondo, A. Ueno JAERI, Ibaraki-ken
	J-PARC linac consists of a 3 MeV RFQ linac, a 50 MeV DTL (Drift Tube Linac), a 190 MeV SDTL (Separate-type DTL), and a 400 MeV ACS (Annular-Coupled Structure) linac. As presented in a separate paper, we plan to perform phase-scan with precise TOF (Time Of Flight) beam-energy measurement in RF tuning of SDTL tanks. As a back-up method, we are considering to prepare an RF tuning scheme with rough TOF measurement for SDTL. In this paper, the principle of this scheme is presented, and its advantages and disadvantages are discussed based on a systematic particle simulation.

TUP70	Systematic Calibration of Beam Position Monitor in the High Intensity Proton Accelerator (J-PARC) LINAC	quadrupole, pick-up, linac, proton	429
	S. Sato, K. Hasegawa, F. Hiroki, J. Kishiro, Y. Kondo, M. Tanaka, T. Tomisawa, A. Ueno, H. Yoshikawa JAERI, Ibaraki-ken Z. Igarashi, M. Ikegami, N. Kamikubota, S. Lee, K. Nigorikawa, T. Toyama KEK, Ibaraki
	In J-PARC, a MW class of proton accelerator is under construction. Improperly- tuned beam would critically result in unacceptable (>0.1%) energy loss. Systematic strategy of fine calibrations of the beam position monitor (BPM) detectors, is therefore required. First, Off-beam-line calibrations of BPMs are taken, with a dedicatedly- designed bench, which has a beam-simulating electric wire carrying 324 MHz. And then discrepancies are calibrated for each BPM between reconstructed electrical center of pick-up plates and measured mechanical center, before the installation of BPM on the beam line. Secondly, after BPMs are installed on the beam line, real beam is used for systematic calibrations (Beam Based Calibration (BBC)). The discrepancies are calibrated between electromagnetic center of Q-magnets and reconstructed beam position. In KEK we have the first stage of J-Parc LINAC with Ion source, RFQ, DTL, Q- and steering-magnets, and lots of BPMs. Implementation of BBC is going with SAD-language, which can also be used for beam steering and beam trajectory simulations, e.g. TRACE-3D. In this presentation, such strategic BPM calibration system will be intensively described.

TUP76	Adaptive Feedforward Cancellation of Sinusoidal Disturbances in Superconducting RF Cavities	damping, feedback, superconducting-RF, linac	447
	T.H. Kandil, T.L. Grimm, W. Hartung, H. Khalil, J. Popielarski, J. Vincent, R.C. York NSCL, East Lansing, Michigan
	A control method, known as adaptive feedforward cancellation (AFC) is applied to damp sinusoidal disturbances due to microphonics in superconducting RF (SRF) cavities. AFC provides a method for damping internal, and external sinusoidal disturbances with known frequencies. It is preferred over other schemes because it uses rudimentary information about the frequency response at the disturbance frequencies, without the necessity of knowing an analytic model (transfer function) of the system. It estimates the magnitude and phase of the sinusoidal disturbance inputs and generates a control signal to cancel their effect. AFC, along with a frequency estimation process, is shown to be very successful in the cancellation of sinusoidal signals from different sources. The results of this research may significantly reduce the power requirements and increase the stability for lightly loaded continuous-wave SRF systems.

TUP79	A New RF System for the CEBAF Normal Conducting Cavities	feedback, linac, electron, extraction	456
	C. Hovater, H. Dong, A. Hofler, G. Lahti, J. Musson, T. Plawski TJNAF, Newport News, Virginia
	The CEBAF Accelerator at Jefferson Lab is a 6 GeV five pass electron accelerator consisting of two superconducting linacs joined by independent magnetic transport arcs. CEBAF also has numerous normal conducting cavities for beam conditioning in the injector and for RF extraction to the experimental halls. The RF systems that presently control these cavities are becoming expensive to maintain, therefore a replacement RF control system is now being developed. For the new RF system, cavity field control is maintained digitally using an FPGA which contains the feedback algorithm. The system incorporates digital down conversion, using quadrature under-sampling at an IF frequency of 70 MHz. The VXI bus-crate was chosen as the operating platform because of its excellent RFI/EMI properties and its compatibility with the EPICS control system. The normal conducting cavities operate at both the 1497 MHz accelerating frequency and the sub-harmonic frequency of 499 MHz. To accommodate this, the new design will use different receiver-transmitter daughter cards for each frequency. This paper discuses the development of the new RF system and reports on initial results.

TUP86	Coupler Development and Gap Field Analysis for the 352 MHz Superconducting CH-Cavity	quadrupole, coupling, linac, proton	477
	H. Liebermann, H. Podlech, U. Ratzinger, A.C. Sauer IAP, Frankfurt-am-Main
	The cross-bar H-type (CH) cavity is a multi-gap drift tube structure based on the H-210 mode currently under development at IAP Frankfurt and in collaboration with GSI. Numerical simulations and rf model measurements showed that the CH-type cavity is an excellent candidate to realize s.c. multi-cell structures ranging from the RFQ exit energy up to the injection energy into elliptical multi-cell cavities. The reasonable frequency range is from about 150 MHz up to 800 MHz. A 19-cell, β=0.1, 352 MHz, bulk niobium prototype cavity is under development at the ACCEL-Company, Bergisch-Gladbach. This paper will present detailed MicroWave Studio simulations and measurements for the coupler development of the 352 MHz superconducting CH cavity. It will describe possibilities for coupling into the superconducting CH-Cavity. The development of the coupler is supported by measurement on a room temperature CH-copper model. We will present the first results of the measurements of different couplers, e.g. capacitive and inductive couplers, at different places of the CH Cavity.

TUP90	Improvements of RF Characteristics in the SDTL of the J-PARC Proton LINAC	insertion, linac, proton, focusing	489
	S. Wang IHEP Beijing, Beijing T. Kato KEK, Ibaraki V.V. Paramonov RAS/INR, Moscow
	A separated drift tube linac (SDTL)* was selected as an accelerator structure of Japan Proton Accelerator Complex (J-PARC), which follows DTL. The SDTL of J-PARC consists of 32 short tanks, ranging from 1.5 to 2.5 m in length. A design of frequency tuners of the SDTL was performed by taking account of 3-D field distribution calculated with MAFIA. The effects of stems on the resonant frequency and field distribution were also analyzed. An easy and effective compensation method for perturbation by stems of both end cells was proposed and applied to the SDTL tanks. * T. Kato. Proposal of a Separated-type Proton Drift Tube Linac for a Medium-Energy Structure. KEK Report 92-10, (1992)

TUP93	Results of a 3D-EM-Code Comparison on the TRISPAL Cavity Benchmark	coupling, resonance, rfq	495
	P. Balleyguier CEA/DAM, Bruyères-le-Châtel
	Several 3D electromagnetic codes (MAFIA, CST MicroWave-Studio, Vector-Fields Soprano, Ansoft HFSS, SLAC Omega3P) have been tested on a 2-cell cavity benchmark. Computed frequencies and Q-factors were compared to experimental values measured on a mock-up, putting the emphasis on the effect of coupling slots. It comes out that MAFIA limitations due to the staircase approximation is overcome by all other codes, but some differences still remain for losses calculations in re-entrant corners

TUP95	Evaluation of Magnetic Field Enhancement Along a Boundary	dipole, linac, linear-collider, collider	501
	Y. Iwashita Kyoto ICR, Kyoto T. Higo KEK, Ibaraki
	Generally, a cavity has convex corners on its inner surface, where the surface field becomes higher than the average accelerating gradient. This effect has been paid attention not to exceed a criterion only on surfaces that have high electric field gradient. A high magnetic field area, however, sometimes seems harmful on a stable operation too. Such enhancement factors are evaluated in a 2D model to show a feasible crossing angle limit on a convex angle of two surfaces.

TUP96	Mechanical Stability Simulations on a Quarter Wave Resonator for the SPIRAL II Project	acceleration, linac, vacuum, coupling	504
	H. Saugnac, J.-L. Biarrotte, S. Blivet, S. Bousson, M. Fouaidy, T. Junquera, G. Olry IPN, Orsay
	In the framework of the SPIRAL II project, IPN Orsay is studying a 88 MHz β=0.12 super conducting quarter wave resonator prototype. Due to its low RF bandwidth (around 60 Hz) the resonator must have a very high mechanical stability and have small sensitivity to dynamic mechanical loads. To simulate the effects of geometrical deformations on the fundamental RF frequency a three dimensional analysis is required. The simulations were made by coupling mechanical FEM analysis performed in COSMOS/GEOSTAR™ with the RF electromagnetic FEM code MICAV™ integrated in the COSMOS/GEOSTAR™ interface. Static mechanical loads were first studied to reduce the effects of external pressure on the RF frequency shift and evaluate the tuning sensitivity of the cavity. Then, simulations on the dynamic response of the resonator, using the modal superposition analysis method, with random external pressure variations and harmonic excitation of the cavity were performed. This paper presents the results of the simulations and mechanical solutions chosen to increase the cavity RF frequency stability.

TUP97	Some Estimations for Correlation Between the RF Cavity Surface Temperature and Electrical Breakdown Possibility	electron, vacuum, photon	507
	V.V. Paramonov RAS/INR, Moscow
	The electrical breakdown in accelerating cavities is the complicated phenomenon and depends on many parameters. Some reasons for breakdown can be avoided by appropriate vacuum system design and the cavity surface cleaning. This case, for normal conducting accelerating cavities free electrons - the dark currents due to Fowler-Nordheim emission can be considered as the main reason of possible electrical breakdown. It is known from the practice - the combination of the high electric field at the cavity surface with high surface temperature is the subject for risk in the cavity operation. In this paper the dependence on the surface temperature is considered and 'effective' electric field enhancement is discussed.

TH103	Summary of the Argonne Workshop on High Gradient RF	electron, linac, ion, linear-collider	564
	J. Norem ANL, Argonne, Illinois
	Workshop on High Gradient rf was held at Argonne from October 7 - 9, 2003. This workshop reviewed the problems encountered when a number of accelerator technologies approached the high gradient limits. The aim of the workshop was to involve materials scientists and try to look at trigger mechanisms and surface interactions, in addition to reviewing progress. Talks were presented on superconducting rf, progress with high and low frequency copper cavities, and dielectrics. The focus was on both experimental and theoretical aspects of the problem. The overall picture presented at the workshop will be summarized.
	Transparencies

TH201	IOT RF Power Sources for Pulsed and CW Linacs	klystron, linac, gun, electron	574
	H.P. Bohlen CPI, Palo Alto, California Y. Li, R.N. Tornoe CPI/EIMAC, San Carlos, California
	For many years, klystrons have been the preferred RF power amplifiers for both pulsed and CW linacs at UHF and higher frequencies. Their properties have earned them that position. But in recent years in UHF terrestrial television transmitters the earlier predominant klystron has been replaced the Inductive Output Tube (IOT) because the IOT provides higher efficiency and, due to its excellent linearity, can handle the simultaneous amplification of both the vision and the sound signal. Its robustness and life expectancy equals that of a klystron, and it more than compensates its lower gain by a lower price and a smaller size. For linac operation, derivates of UHF TV IOTs, capable of up to 80 kW CW output power, are already available and operating. In L-Band, they are presently joined by recently developed 15 to 30 kW CW IOTs. HOM-IOTs are expected to extend the CW range in UHF to 1 MW and beyond. Pulsed operation of an IOT can be achieved without a high-voltage modulator. Since the beam current is grid-controlled it is sufficient to pulse the drive power.
	Transparencies

TH204	End-to-End Beam Dynamics Simulations for the ANL-RIA Driver Linac	linac, emittance, ion, beam-losses	584
	P.N. Ostroumov ANL/Phys, Argonne, Illinois
	The proposed Rare Isotope Accelerator (RIA) Facility consists of a superconducting (SC) 1.4 GV driver linac capable of producing 400 kW beams of any ion from hydrogen to uranium. The driver is configured as an array of ~350 SC cavities, each with independently controllable rf phase. For the end-to-end beam dynamics design and simulation we use a dedicated code, TRACK. The code integrates ion motion through the three-dimensional fields of all elements of the driver linac beginning from the exit of the electron cyclotron resonance (ECR) ion source to the production targets. TRACK has been parallelized and is able to track large number of particles in randomly seeded accelerators with misalignments and a comprehensive set of errors. The simulation starts with multi-component dc ion beams extracted from the ECR. Beam losses are obtained by tracking up to million particles in hundreds of randomly seeded accelerators. To control beam losses a set of collimators is applied in designated areas. The end-to-end simulations with the TRACK code have been extremely useful for studies of different options of the driver linac design with respect to beam quality, beam losses and sensitivity of beam parameters to various types of errors.
	Transparencies

TH302	End-to-End Beam Simulations for the MSU RIA Driver Linac	linac, emittance, ion, alignment	594
	X. Wu, M. Doleans, D. Gorelov, T.L. Grimm, F. Marti, R.C. York, Q. Zhao NSCL, East Lansing, Michigan
	The Rare Isotope Accelerator (RIA) driver linac proposed by Michigan State University (MSU) will use a 10th sub-harmonic based, superconducting, cw linac to accelerate light and heavy ions to final energies of ≤400 MeV/u with beam powers of 100 to 400 kW. The driver linac uses superconducting quarter-wave, half-wave, and six-cell elliptical cavities with frequencies ranging from 80.5 MHz to 805 MHz for acceleration, and superconducting solenoids and room temperature quadrupoles for transverse focusing. For the heavier ions, two stages of charge-stripping and multiple-charge-state acceleration will be used to meet the beam power requirements and to minimize the requisite accelerating voltage. End-to-end, three-dimensional (3D), beam dynamics simulations from the ECR to the radioactive beam production targets have been performed. These studies include a 3D analysis of multi-charge-state beam acceleration, evaluation of transverse misalignment and rf errors on the machine performance, modeling of the charge-stripping and stripping-chicane performance, and beam switchyard design. The results of these beam dynamics studies will be presented, and further planned beam dynamics studies will be discussed.
	Transparencies

THP03	DESIGN IMPROVEMENT OF THE RIA 80.5 MHZ RFQ	rfq, ion, emittance, linac	599
	Q. Zhao, V. Andreev, M. Doleans, D. Gorelov, T.L. Grimm, W. Hartung, F. Marti, S.O. Schriber, X. Wu, R.C. York NSCL, East Lansing, Michigan
	An 80.5 MHz, continuous-wave, normal-conducting, radio-frequency quadrupole (RFQ) was designed for the front end of the Rare Isotope Accelerator (RIA) driver linac. It will accelerate various ion beams (hydrogen up to uranium) from 12 keV/u to about 300 keV/u. The 4-meter-long RFQ accepts the pre-bunched beam from the low energy beam transport (LEBT) and captures more than 80% with a current of ~0.3 mA. Beam dynamics simulations show that the longitudinal output emittance is small for both single^- and two-charge-state ion beams with an external multi-harmonic buncher. A 4-vane resonator with magnetic coupling windows was employed in the cavity design to provide large mode separation, high shunt impedance, and a small transverse dimension. The results of beam dynamics as well as the electromagnetic simulations are presented.

THP08	The Frankfurt Funneling Experiment	rfq, ion, linac, emittance	614
	A. Schempp, U. Bartz, N. Müller, J. Thibus, H. Zimmermann IAP, Frankfurt-am-Main
	Funneling is a procedure to multiply beam currents of rf-accelerators at low energies. In the ideal case the beam current can be multiplied in several stages without emittance growth. The Frankfurt Funneling Experiment consists of two ion sources, a Two-Beam RFQ accelerator, two different funneling deflectors and a beam diagnostic equipment system. The whole set-up is scaled for He⁺ instead of Bi⁺ for the first funneling stage of a HIIF driver. The progress of our experiment and the results of the simulations will be presented.

THP10	Tuner Design for High Power 4-Rod-RFQs	rfq, linac, ion, vacuum	617
	A. Schempp, L. Brendel, B. Hofmann, H. Liebermann IAP, Frankfurt-am-Main
	The performance of high power RFQ linacs, as used in spallations sources and proposed for projects like ADxy, IFMIF or high duty factor drivers for RIB application are limited by beam dynamics properties as well as technical limits like sparking, power density, cooling and thermal stresses. A "one piece structure" even possible in theory has to have means for tuning the real fields like exchangable or moving tuners. Tuner design features will be discussed and results will be presented.

THP21	Calculation of Electron Beam Dynamics of the LUE-200 Accelerator	electron, focusing, target, quadrupole	639
	A.P. Sumbaev, V. Alexandrov, N.Y. Kazarinov, V.F. Shevtsov JINR, Dubna, Moscow Region
	The results of calculations of the focusing and transportation systems of the electron beam of LUE-200 accelerator – the driver of a pulse source of resonant neutrons IREN, JINR (Dubna), are presented. Simulations of the beam dynamics in the traveling wave accelerator were carried out by means of PARMELA code. The calculations have been fulfilled for various parameters of the focusing magnetic fields in the accelerator and the channel, various currents of the beam and various initial distributions of electrons.

THP22	3D Beam Dynamics Simulation in Undulator Linac	ion, undulator, linac, bunching	642
	E.S. Masunov, S.M. Polozov MEPhI, Moscow
	The ion beam can be bunched and accelerated in linear accelerator with RF undulator (UNDULAC-RF). The acceleration and focusing of beam can be realized without using a synchronous wave. In this paper the computer simulation of high intensity ion beam dynamics in UNDULAC-RF was carried out by means of the "superparticles" method. The computer simulation and optimization of ion dynamics consist of two steps. At the first, the equations of particles motion in polyharmonic fields are devised by means of smooth approximation. Hamiltonian analysis of these equations allows to find a velocity of reference particle in polyharmonic field and to formulate the conditions of good longitudinal bunching and transverse focusing beam. At the second, the 3D ion beam dynamics simulation in an UNDULAC is governed by founded functions of reference particle velocity and a ratio of amplitude harmonics. The influence of the space charge on RF focusing conditions, transmission coefficient, longitudinal and transverse emittances, and other acceleration system characteristics are investigated by computer simulation. Masunov E.S., Sov. Phys.-Tech. Phys., vol. 35, No. 8, p. 962, 1990.

THP26	Comparison of 2 Cathode Geometries for High Current (2 kA) Diodes	cathode, electron, emittance, focusing	654
	N. Pichoff CEA/DAM, Bruyères-le-Châtel F. Bombardier, M. Caron, E. Merle, C. Noël, O. Pierret, R. Rosol, C. Vermare CEA, Pontfaverger-Moronvilliers D.C. Moir LANL, Los Alamos, New Mexico A. Piquemal CEA/PTN, Bruyères-le-Châtel
	AIRIX (FRANCE) and DARHT axis-1 (USA) are two high current accelerators designed for flash X-ray radiography. The electron beam produced (2 kA, 3.5 to 3.8 MV, 60 ns) is extracted from a velvet cold cathode. Specific calculations have demonstrated the influence of the cathode geometry on the emitted beam profile [1]. To check this assumption we have made two different experiments (DARHT March 2003 – AIRIX March 2004). We have compared the beam characteristics with two different geometries both theoretically and experimentally. The beam simulations have been done with 3 codes: a home-made code (M2V) and 2 commercial codes (PBGUNS and MAGIC). The extracted beam current and transverse profiles, for the first experiment, have been measured and compared to simulations results. In the second one, we have compared the beam’s extracted current and the energy spread. [1] E. Merle et al., "Efforts to Improve Intense Linear Induction Accelerator (LIA) Sources for Flash Radiography",Proceedings of the LINAC2002 conference. August 19-23, 2002 Gyeongju, Korea.

THP27	Ultra Low Emittance Electron Gun Project for FEL Application	emittance, gun, cathode, electron	657
	R. Ganter, M. Dehler, J. Gobrecht, C. Gough, G. Ingold, S. Leemann, M. Paraliev, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, V. Schlott, A. Streun, A. Wrulich PSI, Villigen A. Candel, K. Li ETH, Zürich
	Most of the current 1Å Free-Electron Laser (FEL) projects are based on thermionic or photocathode guns aiming at an electron beam emittance of 0.5 to 1 mm·mrad. The design of a gun capable of producing a beam with an emittance one or two order of magnitude lower than the state of the art would reduce considerably the cost and size of such a FEL. Due to the recent advances in nanotechnologies and vacuum microelectronics, a field-emitter based gun is a promising alternative scheme. We present first measurements on commercial field emitter arrays as well as 3-D numerical simulations of the electron beam dynamics for typical bunch distributions generated from field emitters in realistic gun geometries. The design and some experimental results on a 500kV pulser is also presented.
	Transparencies

THP33	Progress toward NLC/GLC Prototype Accelerator Structures	dipole, impedance, pick-up, linac	675
	J. Wang, G. Bowden, V.A. Dolgashev, R.M. Jones, J. Lewandowski, C.D. Nantista, S.G. Tantawi SLAC/ARDA, Menlo Park, California C. Adolphsen, D.L. Burke, J.Q. Chan, J. Cornuelle, S. Döbert SLAC/NLC, Menlo Park, California T. Arkan, C. Boffo, H. Carter, N. Khabiboulline FNAL, Batavia, Illinois N. Baboi DESY, Hamburg D. Finley, I. Gonin, S. Mishra, G. Romanov, N. Solyak Fermilab, Batavia, Illinois Y. Higashi, T. Higo, T. Kumi, Y. Morozumi, N. Toge, K. Ueno KEK, Ibaraki Z. Li, R. Miller, C. Pearson, R.D. Ruth, P.B. Wilson, L. Xiao SLAC, Menlo Park, California
	The accelerator structure groups for NLC (Next Linear Collider) and GLC (Global Linear Colliders) have successfully collaborated on the research and development of a major series of advanced accelerator structures based on room-temperature technology at X-band frequency. The progress in design, simulation, microwave measurement and high gradient tests are summarized in this paper. The recent effort in design and fabrication of the accelerator structure prototype for the main linac is presented in detail including HOM (High Order Mode) suppression and couplers, fundamental mode couplers, optimized accelerator cavities as well as plans for future structures. We emphasize techniques to reduce the field on the surface of the copper structures (in order to achieve high accelerating gradients), limit the dipole wakefields (to relax alignment tolerance and prevent a beam break up instability) and improve shunt impedance (to reduce the RF power required).

THP38	High Precision Survey and Alignment of Large Linear Accelerators	alignment, survey, target, vacuum	690
	J. Prenting, M. Schlösser DESY, Hamburg J. Green, G. Grzelak, A. Mitra, A. Reichold OXFORDphysics, Oxford, Oxon A. Herty CERN, Geneva
	For the future linear accelerator TESLA the demanded accuracy for the alignment of the components is 0.5 mm horizontal and 0.2 mm vertical, both on each 600 m section. Other accelerators require similar accuracies. These demands can not be fulfilled with open-air geodetic methods, mainly because of refraction. Therefore the RTRS (Rapid Tunnel Reference Surveyor), a measurement train performing overlapping multipoint alignment on a reference network is being developed. Two refraction-free realizations of this concept are being developed at the moment: the first one (GeLiS) measures the horizontal co-ordinates using stretched wires, combined with photogrammetric split-image sensors in a distance measurement configuration. In areas of the tunnel where the accelerator is following the earth curvature GeLiS measures the height using a new hydrostatic leveling system. The second concept (LiCAS) is based on laser straightness monitors (LSM) combined with frequency scanning interferometry (FSI) in an evacuated system. LiCAS measures both co-ordinates with respect to its LSM-beam and is thus suitable for geometrically straight tunnel sections. Both measurement systems will be placed on a train, which could do the reference survey autonomously.

THP43	Reduction of RF Power Loss Caused by Skin Effect	vacuum, electromagnetic-fields	700
	Y. Iwashita Kyoto ICR, Kyoto
	RF current flows only on a metal surface with very thin skin depth, which decreases with RF frequency. Thus the surface resistance increases with the frequency. Because the skin depth also decreases when the metal conductivity increases, the improvement of the conductivity does not contribute much; it is only an inverse proportion to the square root of the conductivity. Recently, it is shown that such a power loss can be reduced on a dielectric cavity with thin conductor layers on the surface, where the layers are thinner than the skin depth. Some possibilities to implement the idea and to extend the application to general cavities and transmission lines will be discussed.

THP45	The Toshiba E3736 Multi Beam Klystron	klystron, electron, cathode, gun	706
	A. Yano, S. Miyake TETD, Saitama Y.H. Chin KEK, Ibaraki S.Y. Kazakov IHEP Protvino, Protvino, Moscow Region A.V. Larionov, V.E. Teryaev BINP SB RAS, Protvino, Moscow Region
	A 10 MW, L-band multi beam klystron (MBK) for TESLA linear collider and TESLA XFEL has been under development at Toshiba Electron Tubes & Devices Co., Ltd. (TETD) in collaboration with KEK. The TESLA requires pulsed klystrons capable of 10 MW output power at 1300 MHz with 1.5 ms pulse length and a repetition rate of 10 pps. The MBK with 6 low-perveance beams in parallel in the klystron enables us to operate at lower cathode voltage with higher efficiency. The design work has been accomplished and the fabrication is under way. We are going to start conditioning and testing of prototype #0 in the beginning of June 2004. The design overview and the initial test results at the factory will be presented.

THP46	Cable Insulation Breakdowns in the Modulator with a Switch Mode High Voltage Power Supply	linac, power-supply, photon, klystron	709
	A. Cours ANL, Argonne, Illinois
	The Advanced Photon Source modulators are PFN-type pulsers with 40 kV switch mode charging power supplies (PSs). The PS and the PFN are connected to each other by 18 feet of high-voltage (HV) cable. Another HV cable connects two separate parts of the PFN. The cables are standard 75 kV x-ray cables. All four cable connectors were designed by the PS manufacturer. Both cables were operating at the same voltage level (about 35 kV). The PS’s output connector has never failed during five years of operation. One of the other three connectors failed approximately five times more often than the others. In order to resolve the failure problem, a transient analysis was performed for all connectors. It was found that transient voltage in the connector that failed most often was subjected to more high-frequency, high-amplitude AC components than the other three connectors. It was thought that these components caused partial discharge in the connector insulation and led to the insulation breakdown. Modification of the PFN eliminated one HV cable and significantly reduced the AC components during the pulse. A connector with higher partial discharge inception voltage was chosen as a replacement.

THP48	A High-Resolution S-band Down-Converting Digital Phase Detector for SASE FEL Use	linac, photon, feedback, free-electron-laser	715
	A.E. Grelick, N.D. Arnold ANL/APS, Argonne, Illinois J. Carwardine, N. Dimonte, A. Nassiri, T. Smith ANL, Argonne, Illinois
	Each of the rf phase detectors in the Advanced Photon Source linac consists of a module that down converts from S-band to 20 MHz followed by an analog I/Q detector. Phase is calculated from one digitized sample per pulse each of I and Q. The resulting data has excellent long-term stability but is noisy enough so that a number of samples must be averaged to get a usable reading. The more recent requirement to support a SASE FEL has presented the need to accurately resolve the relative phase of a single pulse. Replacing analog detection with digital sampling and replacing internal intermediate frequency reference oscillators with a lower noise external oscillator were used to control the two largest components of noise. The implementation of a central, ultralow noise reference oscillator and a distribution system capable of maintaining the low phase noise is described, together with the results obtained to date. The principal remaining technical issue is determining the processing power required as a function of measurement channels per processor, measured pulse repetition rate, intrapulse data bandwidth, and digital filter characteristics. The options and tradeoffs involved and the present status are discussed.

THP55	Electromagnetic Design of New RF Power Couplers for the S-DALINAC	electron, emittance, electromagnetic-fields, linac	736
	M. Kunze, M. Brunken, H.-D. Gräf, W.F.O. Müller, A. Richter, T. Weiland TU Darmstadt, Darmstadt
	New rf power couplers for the Superconducting Darmstadt Linear Accelerator (S-DALINAC) injector have to be designed to transfer rf power of up to 2 kW to the electron beam. This allows injector operation at beam currents from 0.15 mA to 0.2 mA and electron energies up to 14 MeV. The new couplers should possibly provide a external Q of 5·10⁶. The transverse kick should be as small as possible. The asymmetric field distribution of the couplers causes emittance growth of the electron beam and therefore the transverse kick has to be minimized. Electromagnetic simulations are applied to investigate different coupler designs and to localize possible problems at an early stage. Cavity external Q and transverse kick can be calculated from 3D electromagnetic eigenmode solutions. The present coaxial-coaxial input couplers at the S-DALINAC are limited to power operation below 500 W under full reflection. In order to reach power operation up to 2 kW a realizations of a low-kick waveguide coupler for the S-DALINAC injector is presented, namely a twin-waveguide coupler.
	Transparencies

THP57	Digital Feedback System for J-Parc Linac RF Source	feedback, linac, klystron, proton	742
	S. Michizono, S. Anami, S. Yamaguchi KEK, Ibaraki T. Kobayashi J-PARC, Ibaraki-ken
	At the proton linac of J-Parc (Japan Proton Accelerator Research Complex), an accelerating electric field stability of ±1% in amplitude and ±1° in phase is required for the RF system. In order to accomplish these requirements, a digital feedback system is adopted for flexibility of the feedback (FB) and feed forward (FF) algorism implementation. FPGAs are used for the real-time FB system. A DSP board is also utilized for data processing and communication between FPGAs and a crate control CPU (Host). The system was examined with the DTL cavity and it satisfies the stability specification. In this report, the digital rf system is described and operational stability is also summarized.

THP64	Waveguide Stub Tuner Analysis for CEBAF Application	klystron, coupling, insertion, resonance	757
	H. Wang Jefferson Lab, Newport News, Virginia M. Tiefenback TJNAF, Newport News, Virginia
	Three-stub WR650 waveguide tuners have been used on the CEBAF superconducting cavities for two changes on the external Qs: increasing the Q from 6·10⁶ to 8·10⁶ on 5-cell cavities to reduce the klystron power at operation gradients and decreasing the Q from 2·10⁷ to 8·10⁶ on 7-cell cavities to ease the control system handling the Lorenz Force detuning. To understand the reactive tuning effects in the machine operations with beam current and mechanical tuning, a network analysis model was developed. The S parameters of the stub tuner were simulated by MAFIA and measured on the bench. We used this stub tuner model to study tuning range, sensitivity, frequency pulling as well as cold waveguide and window heating problems. Detailed experimental results will be compared against this model. Pros and cons of this stub tuner application will be summarized.

THP67	Traveling Wave and Standing Wave Single Cell High Gradient Tests	vacuum, coupling, linear-collider, collider	766
	V.A. Dolgashev SLAC/ARDB, Menlo Park, California Y. Higashi, T. Higo KEK, Ibaraki C.D. Nantista, S.G. Tantawi SLAC/ARDA, Menlo Park, California
	Accelerating gradient is one of the crucial parameters affecting design, construction and cost of next-generation linear accelerators. Operating accelerating gradient in normal conducting accelerating structures is limited by rf breakdown. In this paper we describe an experimental setup for study of these limits for 11.4 GHz traveling-wave and standing-wave accelerating structures. The setup uses matched mode converters that launch the circular TM01 mode and short test structures. The test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype structures for the Next Linear Collider. Fields elsewhere in the test structures and in the mode converters are significantly lower then in this single cell. This setup allows economic testing of different cell geometries, cell materials and preparation techniques with short turn around time. In this paper we present design considerations and initial experimental data.

THP68	The Simulation Calculations And Dielectric Characteristics Investigation of a Hybrid Dielectric-Iris-Loaded Travelling Accelerating Structure		769
	C.-F. Wu USTC/NSRL, Hefei, Anhui
	Mafia code has been used to calculate the RF properties versus the geometric parameters and dielectric permittivity of the X-band (f=9.37 GHz) hybrid dielectric-iris-loaded travelling accelerating structure. The simulation results show that when the range of the permittivity is about 5–9 and the geometric parameters are optimized, the new structure may have lower ratio (about 1) of peak surface electric field at the iris to axial accelerating electric field , while r, Q, r/Q of the new structure being comparable to iris-loaded accelerating structure. The experimental investigation of the permittivity of the dielectric (ceramic)has been made by using the cavity perturbation technique. The results show that the permittivity of the ceramic is about 5.8 at the X-band and its stability is good.The above results will be applied to the design of the new accelerating structure, which may be a potential candidate of high gradient Linear accelerator.

THP69	The Tuning Study of the Coupled Cavities for the RF Chopper System of J-PARC	coupling, linac, proton, insertion	770
	S. Wang, S. Fu IHEP Beijing, Beijing T. Kato KEK, Ibaraki
	A 3 MeV medium-energy beam transport line (MEBT) is located between RFQ and DTL in the linac of the Japan Proton Accelerator Research Complex (J-PARC). MEBT accomplishes beam matching and chopping. An rf deflector (RFD), which is a heavily loaded cavity, was adopted as a chopper in J-PARC linac for chopping 500 μs long macropulses from the ion source into sub-pulses for injecting into the following 3 GeV rapid-cycling ring. A coupled RFD system was proposed in the design of chopper system for saving the cost of rf power source. The tuning of the coupled RFD system was successfully performed. The longer rise time of the second RFD and the delay of the second RFD excitation were found during the tuning of the coupled RFD system, and these phenomena were further analyzed and investigated. Both in the high power and beam tests, the chopper worked well without any discharge under 36 kW peak driving power.

THP84	Design of a 300 GHz Broadband TWT Coupler and RF-Structure	coupling, RF-structure, electron, plasma	794
	F.L. Krawczyk, F.E. Sigler LANL/LANSCE, Los Alamos, New Mexico B.E. Carlsten, L.M. Earley LANL, Los Alamos, New Mexico J.M. Potter JP Accelerator Works, Inc., 2245, Los Alamos, NM M.E. Schulze GA, Los Alamos E. Smirnova MIT/PSFC, Cambridge, Massachusetts
	Recent LANL activities in millimeter wave structures focus on 94 and 300 GHz structures. They aim at power generation from low power (100–2000 W) with a round electron beam (120 kV, 0.1–1.0 A) to high power (2–100 kW) with a sheet beam structure (120 kV, 20 A). Applications cover basic research, radar and secure communications and remote sensing of biological and chemical agents. In this presentation the design and cold-test measurements of a 300 GHz RF-structure with a broadband (>6% bandwidth) power coupler are presented. The design choice of two input/output waveguides, a special coupling region and the structure parameters themselves are presented. As a benchmark also a scaled up version at 10 GHz was designed and measured. These results will also be presented.

THP86	Low Power Measurements on a Finger Drift Tube Linac	linac, ion, booster, rfq	800
	A. Schempp, K.-U. Kühnel IAP, Frankfurt-am-Main C.P. Welsch MPI-K, Heidelberg
	The efficiency of RFQs decreases at higher particle energies. The DTL structures used in this energy regions have a defocusing influence on the beam. To achieve a focusing effect, fingers with quadrupole symmetry were added to the drift tubes. Driven by the same power supply as the drift tubes, the fingers do not need an additional power source or feedthrough. Beam dynamics have been studied with PARMTEQ . Detailed analysis of the field distribution was done and the geometry of the finger array has been optimized with respect to beam dynamics. A spiral loaded cavity with finger drift tubes was built up and low power measurements were done. In this contribution, the results of the rf simulating with Microwave Studio are shown in comparison with bead pertubation measurement on a prototype cavity.

THP92	Effect of the Tuner on the Field Flatness of SNS Superconducting RF Cavities	coupling, resonance, superconducting-RF, pick-up	815
	A. Sun ORNL/SNS, Oak Ridge, Tennessee H. Wang, G. Wu Jefferson Lab, Newport News, Virginia
	Field flatness in a multi-cell superconducting cavity affects not only the net accelerating voltage, but also the peak surface field and the Lorenz Force detuning coefficient. Our measurement indicates that the field flatness changes both external Q of the Fundamental Power Coupler (FPC) and external Q of the Field Probe (FP). The field amplitude tilts linearly to the distance between the cell center and the cavity’s geometry center (pivot point). The tilt rate has been measured in a cryomodule cold (2 K) test, being about 2%/100 kHz, relative the field flatness at the cavity’s center frequency of 805 MHz. Bead-pull measurements confirmed that the field flatness change is 2.0%/100 kHz for a medium β cavity with helium vessel, and 1.72%/100 kHz without helium vessel. These results matched the predictions of simulations using ANSYS and SUPERFISH. A detailed analysis reveals that longitudinal capacitive gap deformation is the main cause of the frequency change. Field flatness change was not only due to the uneven stored energy change within the cell, but also due to cell-to-cell coupling.

THP93	A 3D Self-Consistent, Analytical Model for Longitudinal Plasma Oscillation in a Relativistic Electron Beam	plasma, electron, space-charge, linac	818
	G. Geloni, E. Saldin, E. Schneidmiller, M.V. Yurkov DESY, Hamburg
	Longitudinal plasma oscillations are becoming a subject of great interest for XFEL physics in connection with LSC microbunching instability[1] and certain pump-probe synchronization schemes[2]. In the present paper we developed the first exact analytical treatment for longitudinal oscillations within an axis-symmetric, (relativistic) electron beam, which can be used as a primary standard for benchmarking space-charge simulation codes. Also, this result is per se of obvious theoretical relevance as it constitutes one of the few exact solutions for the evolution of charged particles under the action of self-interactions. [1] E. Saldin et al., "Longitudinal Space Charge Driven Microbunching instability in TTF linac", TESLA-FEL-2003-02, May 2003, [2] J. Feldhaus et al., "Two-color FEL amplifier for femtosecond-resolution pump-probe experiments with GW-scale X-ray and optical pulses",DESY 03-091, July 2003

THP94	Cold Tests of a 160 MHz Half-Wave Resonator	resonance, linac, coupling, vacuum	821
	R. Stassen, R. Maier FZJ/IKP, Jülich R. Eichhorn, F. M. Esser, B. Laatsch, G. Schug, H. Singer FZJ, Jülich
	The number of polarized particle in the cooler synchrotron COSY is limited by the present injector system. A new linac was projected based on superconductive half-wave resonators to fill COSY up to the space charge limit. The first prototype of a 160 MHz Half-Wave Resonator (HWR) has been built and tested. RF-measurements in CW as well as in a pulsed operation will be presented. A second prototype with a slightly different way of fabrication will be completed soon. All measurements have been done using the new 4 kW loop-coupler. The use of a cold window allows to change the coupling from 1· 10⁶ to 1· 10¹⁰ without any risk of contamination. The mechanical tuner consisting of a stepper motor driven coarse tuner and a fast piezo system to compensate the Lorentz-Force detuning has successfully integrated into the vertical test-cryostat.

FR102	Muon Ionization Cooling Experiment (MICE)	emittance, factory, collider, focusing	832
	M.S. Zisman LBNL, Berkeley, California
	There is presently considerable activity worldwide on developing the technical capability for a “neutrino factory” based on a muon storage ring and, a muon collider. Muons are obtained from the decay of pions produced when an intense proton beam hits a high-Z target, so the initial muon beam has a large 6-dimensional phase space. To increase the muons’ phase-space density, we use ionization cooling, which is based on energy loss in an absorber, followed by re-acceleration with high-gradient, normal-conducting RF cavities. The absorber of choice is liquid hydrogen to minimize multiple scattering. A superimposed solenoidal focusing channel contains the muons. Although the physics is straightforward, the technology and its implementation are not. The international MICE collaboration will demonstrate ionization cooling of a muon beam in a short section of a typical cooling channel. The experiment is approved for operation at Rutherford Appleton Lab. We will measure the cooling effects of various absorber materials at various initial emittance values using single-particle counting techniques. The experiment layout and goals will be discussed, along with the status of component R&D.
	Transparencies