LINAC 2004 - List of Sessions

TUP — Tuesday Poster Session (17-Aug-04 15:30—17:30)

Paper	Title	Page
TUP01	RFQ Drift-Tube Proton Linacs in IHEP	285
	Yu. Budanov, O.K. Belyaev, S.V. Ivanov, A.P. Maltsev, I.G. Maltsev, V.B. Stepanov, S.A. Strekalovskyh, V.A. Teplyakov, V. Zenin IHEP Protvino, Protvino, Moscow Region
	A linac with drift tubes and RF quadrupoles (alias, an RFQ DTL) constitutes a natural extension of the RFQ concept towards higher beam energies. Complementing an RFQ with drift tubes intermitted by spacer electrodes separates functions of focusing and acceleration. Such a structure allows for an increased accelerating rate and upgrades shunt impedance to values competitive against those inherent in the other common accelerator types. Various accelerating/focusing structures for the RFQ DTLs were implemented in IHEP. Their succession is marked by a progress in performance, which is due to efforts in design, manufacturing technology and calculation technique advances that facilitated R&D of such the structures. A sound practical expertise in the field is accumulated. The 30 MeV RFQ DTL is in service as an injector for a 1.5 GeV PS of IHEP since 1985. An upgraded successor – the RFQ DTL, employing a cavity loaded by a novel accelerating/focusing structure with an increased accelerating rate, is now being assembled and tested. Its pre-commissioning results will be outlined. Prospects in R&D of a structure suitable for a front-end part of the CERN SPL will be evaluated.
	Transparencies
TUP02	Development of a 352 MHz Cell-Coupled Drift Tube Linac Prototype	288
	M. Vretenar, Y. Cuvet, J. Genest, C. Völlinger CERN, Geneva F. Gerigk CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
	At linac energies above 40 MeV, alternative structures to the conventional Drift Tube Linac can be used to increase efficiency and to simplify construction and alignment. In the frame of the R&D activities for the CERN SPL and Linac4, a prototype of Cell-Coupled Drift Tube Linac (CCDTL) at 352 MHz has been designed and built. This particular CCDTL concept is intended to cover the energy range from 40 to 90 MeV and consists of modules of ~5 m length made of 3 or 4-gap DTL tanks linked by coupling cells. The focusing quadrupoles are placed between tanks, and are aligned independently from the RF structure. The CCDTL prototype consists of two half tanks connected by a coupling cell and requires an RF power of 120 kW to achieve the design gradient. RF tests will be made at low and high power, the latter up to a 20% duty cycle. This paper introduces the main features of this CCDTL design, describes the RF and mechanical design of the prototype and presents the first measurement results.
TUP03	Design of the LINAC4, A New Injector for the CERN Booster	291
	M. Vretenar, R. Garoby, K. Hanke, A.M. Lombardi, C. Rossi CERN, Geneva F. Gerigk CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
	A new H^- linac (LINAC4) is presently under study at CERN. This accelerator, based on normal conducting structures at 352 and 704 MHz, will provide a 40 mA 160MeV H^- beam to the CERN booster, thus overcoming the present space-charge bottleneck at injection with a 50 MeV proton beam. LINAC4 is conceived as the first stage of a future 2.2 GeV superconducting linac (SPL) and it is therefore designed for a higher duty cycle than required for injection in the booster. This paper discusses the design choices, presents the layout of the facility and illustrates the advantages for the LHC and other CERN users. An R&D and construction strategy mainly relying upon international collaborations is also presented.
TUP04	The SPL Front End: A 3 MeV H^- Test Stand at CERN	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)	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
TUP06	Results of the High-Power Conditioning and the First Beam Acceleration of the DTL-1 for J-PARC	300
	F. Naito, S. Anami, J. Chiba, Y. Fukui, K. Furukawa, Z. Igarashi, K. Ikegami, M. Ikegami, E. Kadokura, N. Kamikubota, T. Kato, M. Kawamura, H. Kobayashi, C. Kubota, E. Takasaki, H. Tanaka, S. Yamaguchi, K. Yoshino KEK, Ibaraki K. Hasegawa, Y. Kondo, A. Ueno JAERI, Ibaraki-ken T. Itou, Y. Yamazaki JAERI/LINAC, Ibaraki-ken T. Kobayashi J-PARC, Ibaraki-ken
	The first tank of the DTL for Japan Proton Accelerator Research Complex (J-PARC) was installed in the test facility at KEK. The DTL tank is 9.9 m in length and consists of the 76 cells. The resonant frequency of the tank is 324 MHz. After the installation of the tank, the high-power conditioning was carried out deliberately. Consequently the peak rf power of 1.3 MW (pulse repetition 50 Hz, pulse length 600 μs) was put into the tank stably. (The required power is about 1.1 MW for the designed accelerating field of 2.5 MV/m on the axis.) Following the conditioning, negative hydrogen beam, accelerated by the RFQ linac up to 3 MeV, was injected to the DTL and accelerated up to its design value of 19.7 MeV. The peak current of 30 mA was achieved with almost 100% transmission. In this paper, the conditioning history of the DTL and the result of the first beam test will be described.
TUP07	A Linac-to-Booster Injection Line for Transverse Matching and Correlated Injection Painting	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.
TUP08	Carbon Ion Injector Linac for a Heavy Ion Medical Synchrotron	306
	D.A. Swenson LLC, Albuquerque, New Mexico
	The design of a Carbon Ion Injector Linac for a heavy ion medical synchrotron will be presented. The linac is designed to accelerate quadruply-ionized carbon ions (¹²C⁴⁺) with a charge/mass ratio (q/A) of 0.333, and all other ions with the same or higher charge/mass ratios, such as H¹⁺, H₂¹⁺, D¹⁺, T¹⁺, ³He¹⁺, ⁴He²⁺, ⁶Li²⁺, ¹⁰B⁴⁺, and ¹⁶O⁶⁺ to an output energy of 7 MeV/u. The 200 MHz linac consists of an Radio Frequency Quadrupole (RFQ) linac to accelerate the ions from an input energy of 0.008 MeV/u to an intermediate energy of 0.800 MeV/u, and an Rf-Focused Interdigital (RFI) linac to accelerate these ions to the output energy. The combined linac structures have a total length of 7.8 meters and a total peak rf power requirement of about 600 kW. The RFQ linac employs a radial-strut, four-bar design that is about twice as efficient as the conventional four-bar RFQ design. The RFI linac, which is basically an interdigital drift tube structure with rf quadrupole focusing incorporated into each drift tube, is about 5 times more efficient than the conventional Drift Tube Linac (DTL) structure. Details of the linac structures and their calculated performance will be presented.
TUP09	The Heidelberg High Current Injector: A Versatile Injector for Storage Ring Experiments	309
	R. von Hahn, M. Grieser, R. Repnow, D. Schwalm, C.P. Welsch MPI-K, Heidelberg
	The High Current Injector (HCI) was designed and built as a dedicated injector for the Test Storage Ring in Heidelberg to deliver mainly singly charged Li- and Be-ions. After start for routine operation in 1999 the HCI delivered stable beams during the following years for about 50 % of the experiments with very high reliability. Due to the requirements from the experiment the HCI changed during that period from a machine for singly charged positive ions to an injector for a large variety of molecules as well as positively or negatively charged light ions. After successful commissioning of the custom built 18 GHz high power ECR-source at its present test location various modifications and additions were made in preparation of a possible conversion into an injector for highly charged heavy ions as a second phase. This paper gives an overview of the experience gained in the passed 5 years and presents the status of the upgrade of the HCI.
TUP10	Design of a Deuteron RFQ for Neutron Generation	312
	Z.Y. Guo, J. Chen, J. Fang, Y.R. Lu, S.X. Peng, Z.Z. Song, J.X. Yu, C. Zhang, K. Zhu PKU/IHIP, Beijing A. Schempp IAP, Frankfurt-am-Main
	A deuteron RFQ is designed for neutron generation with 9Be(d,n)10B reaction. Considering the limitation of available RF transmitter, the frequency was chosen as 201.5 MHz and the peak RF power was set to 400 kW with 10% duty factor. The deuteron beam will be extracted from an ECR ion source also with 10% duty factor and then be accelerated to about 2 MeV by RFQ with high transmission efficiency. The system will be described and the design results of particle dynamics and structure will be given.
TUP11	High current RFQ using laser ion source	315
	M. Okamura, R.A. Jameson, J. Takano, K. Yamamoto RIKEN, Saitama R. Becker, A. Schempp IAP, Frankfurt-am-Main T. Fujimoto AEC, Chiba T. Hattori, N. Hayashizaki TIT, Tokyo Y. Iwata, S. Shibuya NIRS, Chiba-shi H. Kashiwagi JAERI/ARTC, Gunma-ken
	A new RFQ was fabricated for very high current heavy ions. The designed target current is 100 mA with cabon 4⁺ beam. Acceleration test result will be reported at the conference.
TUP13	Test and First Experiments with the new REX-ISOLDE 200 MHz IH-Structure	318
	T. Sieber CERN, Geneva D. Habs, O.K. Kester LMU, Garching
	For the REX-ISOLDE accelerator, a new accelerating structure is at the moment installed and tested. It willl raise the final energy from the present 2.3 MeV/u to 3 MeV/u. The aim is to increase the mass range of the nuclei available for nuclear spectroscopy from mass 40 to mass 80. The new accelerator component is a 0.5 m IH-structure, working at the double REX frequency of 202.56 MHz. It was originally developed as a 7-Gap resonator for the MAFF* project and later adapted to the requirements at REX by changing from a 7-Gap to a 9-Gap resonator to match the lower injection energy. The poster presents the design of the resonator and the results of the rf-tests, commissioning and first operation during the 2004 running period. *H. Bongers et al., The IH-7-Gap Resonators of the Munich Accelerator for Fission Fragments (MAFF) Linac, proceedings of the PAC2001, Chicago, June 2001, p.3945
TUP14	Status of the RFI Linac Prototype	321
	D.A. Swenson, W.J. Starling LLC, Albuquerque, New Mexico
	A prototype of the Rf Focused Interdigital (RFI) linac structure is currently under construction at Linac Systems. The RFI linac structure is basically an interdigital (or Wideröe) linac structure with rf quadrupole focusing incorporated into each drift tube. The 200 MHz RFI prototype, consisting of a short RFQ linac followed by a short RFI linac, will accelerate a 20 mA beam of protons from an injection energy of 25 keV to an output energy of 2.50 MeV in a total linac structure length of 1.44 meters. The linac structures are designed for continuous (cw) operation, and will be tested initially at a 33% duty factor. The peak structure power of 66 kW and peak beam power of 50 kW will be supplied by a 144 kW, 33% duty rf power system. A microwave ion source will supply the proton beam and an articulated Einzel lens will steer and focus the beam into the RFQ aperture. The mechanical design of the linac structures will be presented, the calculated performance will be described, the status of the components will be reported. The prototype is scheduled to come into operation in the fall of this year.
TUP15	Space Charge Compensation in Low Energy Proton Beams	324
	A.B. Ismail, U.D. Uriot CEA/DSM/DAPNIA, Gif-sur-Yvette R. Duperrier CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex N. Pichoff CEA/DAM, Bruyères-le-Châtel
	High power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. In this low energy part, the space charge self force, induced by a high intensity beam, has to be carefully managed. This nonlinear force can generate a high irreversible emittance growth of the beam. To reduce space charge effects, neutralization of the beam charge can be done by capturing some particles of the ionised residual gas in the vacuum chamber. This space charge compensation (SCC) regime complicates the dynamic study. Modelling the beam behaviour in such regime would be a significant contribution to the development of high intensity accelerators. Numerical and experimental study of SCC is in progress on the Saclay High Intensity Proton Injector. Experimental measurements and 2D/3D simulations of proton beam SCC will be presented.
TUP16	Investigation on Beam Dynamics Design of High-Intensity RFQs	327
	C. Zhang, A. Schempp IAP, Frankfurt-am-Main J. Chen, J. Fang, Z.Y. Guo PKU/IHIP, Beijing
	Recently various potential uses of high-intensity beams bring new opportunities as well as challenges to RFQ accelerator research because of the new problems arising from the strong space-charge effects. Unconventional concepts of beam dynamics design, which surround the choice of basic parameters and the optimization of main dynamics parameters’ variation along the machine, are illustrated by the designing Peking University (PKU) Deuteron RFQ. An efficient tool of LANL RFQ Design Codes for beam dynamics simulation and analysis, RFQBAT, is introduced. Some quality criterions are also presented for evaluating design results.
TUP18	Beam Dynamics Issues of SPES-1 Linac	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	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.
TUP20	Some Relevant Aspects in the Design and Construction of a 30-62 MeV Linac Booster for Proton Therapy	336
	V.G. Vaccaro, S. Falco Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli A. D'Elia Naples University Federico II, Napoli D. Davino Universita' degli Studi del Sannio, Benevento M.R. Masullo INFN-Napoli, Napoli
	Recent results in accelerator physics showed the feasibility of a coupling scheme between a cyclotron and a linac for proton acceleration. Cyclotrons with energies up to 30 MeV, mainly devoted to radioisotopes production, are available in a large number of medical centres. This suggested to design a linac booster able to increase the proton energy up to 62 MeV as required for treating tumours like the ocular ones. In this paper we will review the rationale of the project; we will discuss the basic design of a compact 3 GHz SCL (Side Coupled Linac) with a new approach to the linac cavities. Among the many challenges of such a project one of the most interesting is the tuning of the cavities. Because the tuning can be done only after assembling the system, it is difficult to detect which cavities are responsible for the detuning: indeed the resonant behavior of single cavity is lost since the resonances merge into the resonant modes of the whole system. It is shown how, from the measured mode frequencies of the system, it is possible to derive the unknown resonances of each cavity and then refine the tuning. The proposed procedure is quite general and is not restricted to the SCL.
TUP21	Beam Dynamics Design of J-PARC Linac High Energy Section	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	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	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.
TUP26	Alternating Phase Focusing in Low-Velocity Heavy-Ion Superconducting Linac	348
	P.N. Ostroumov, K.W. Shepard ANL/Phys, Argonne, Illinois A. Kolomiets ITEP, Moscow E.S. Masunov MEPhI, Moscow
	The low-charge-state injector linac of the RIA post-accelerator is based on ~60 independently phased SC resonators providing total ~70 MV accelerating potential. The low charge-state beams, however, require stronger transverse focusing, particularly at low velocities, than is used in existing SC ion linacs. For the charge-to-mass ratios considered here (q/A = 1/66) the proper focusing can be reached by the help of strong SC solenoid lenses with the field up to 15 T. Magnetic field of the solenoids can be reduced to 9 T applying an Alternating Phase Focusing (APF). A method to set the rf field phases has been developed and studied both analytically and by the help of the three-dimensional ray tracing code. The paper discusses the results of these studies.
TUP27	Acceleration of Several Charge States of Lead Ion in CERN LINAC3	351
	V. Coco, J.A. Chamings, A.M. Lombardi, E.Zh. Sargsyan, R. Scrivens CERN, Geneva
	CERN’s LINAC3 is designed to accelerate a 100 μAe Pb²⁵⁺ ion beam from 2.5 keV/u to 4.2 MeV/u. The beam is then stripped using a carbon foil and the resulting 25 μAe 54⁺ beam is accumulated and cooled in the Low Energy Ion Ring (LEIR) before transfer to the Proton Synchrotron (PS) and ultimately to the Large Hadron Collider (LHC). The Pb²⁵⁺ ions are selected with a spectrometer from a mixture of ten charge states produced by an Electron Cyclotron Resonance (ECR) source. In view of the fact that the stripping efficiency to Pb⁵⁴⁺ is mostly dependent on energy and not on initial charge state, the feasibility of simultaneously accelerating to 4.2 MeV/u several charge states has been investigated. In this paper we report two possible technical solutions, their advantage in terms of intensity for the downstream machines and the experimental results supporting these conclusions.
TUP29	Proton Beam Dynamics of the SARAF Linac	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	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
TUP42	Beam Optics Studies for the TESLA Test Facility Linac	360
	P. Castro, V. Balandin, N. Golubeva DESY, Hamburg
	The aim of the TESLA Test Facility Linac is to create electron bunches of small transverse emittance and high peak current with energies up to 1 GeV for the VUV-FEL at DESY. The linac consists of a RF photo-cathode gun, a superconducting linac, two magnetic chicanes (for bunch compression), a long undulator magnet section and a beam line bypassing the undulator (for commissioning purposes). A study of (linear) beam optics of the linac is presented for the case of beam commissioning (and beam measurements), FEL operation and long bunch train operation. The requirements of each part of the linac upon the optics are discussed in detail and an appropriate solution for each case is shown, as well as the matching solution to the rest of the accelerator. The chromatic properties of the linac have been studied also.
TUP43	The Superconducting CW Driver Linac for the BESSY-FEL User Facility	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
TUP44	Linac Upgrades for FERMI@ELETTRA	366
	G. D'Auria, R.J. Bakker, P. Craievich, G. De Ninno, S.D. Di Mitri, M. Ferianis, P.G. Pangon, R.L. Rumiz, T.L. Tosi, D. Zangrando Sincrotrone Trieste S.C.p.A., Basovizza, Trieste C. Bocchetta, M. Danailov, B. Diviacco, V. Verzilov ELETTRA, Basovizza, Trieste
	To fulfill the stringent requirements expected from the FERMI project, the existing Linac needs some modifications in the layout and an upgrading of the present plants. Moreover, for the next two years, until the new injection system (now under construction) is fully commissioned, the Linac has to be kept in operation as injector for the ELETTRA Storage Ring. Therefore most of the planned activities have to be carried out without interfering with the normal operation of the machine. Details on the new Linac layout and related activities are discussed.
TUP45	Extended Parametric Evaluation for 1 Å FEL - Emittance and Current Requirements	369
	M. Pedrozzi, G. Ingold PSI, Villigen
	In the synchrotron radiation community there is a strong request for high brightness, coherent X-ray light pulses, especially in the 1 to 0.1 nm wave length range. A Free Electron Laser (FEL), driven by a linear single pass accelerator, is today the most promising mechanism able to produce such radiation. Since the electron beam brightness plays a major role in the laser saturation process and in the final energy of the driving linac, many laboratories are presently working on a new generation of low emittances sources. The present analysis will give an indication about the FEL behaviour and the undulator parameters versus the slice beam quality (emittance, current, energy spread).
TUP46	A New Control System for the S-DALINAC	372
	M. Brunken, W. Ackermann, A. Araz, U. Bonnes, H.-D. Gräf, M. Hertling, A. Karnaukhov, W.F.O. Müller, O. Patalakha, M. Platz, A. Richter, B. Steiner, O. Titze, B. Truckses, T. Weiland TU Darmstadt, Darmstadt
	We will present recent results of the development of a new control system for the superconducting cw electron accelerator S-DALINAC. This system will be based on common industrial standards. Due to the large number of special devices existing to control the beamline, a simple and cheap communication interface is required to replace the current proprietary bus topology. The existing devices will be upgraded by a microcontroller based CAN bus interface as communication path to a control server. The servers themselves may be distributed over the location, giving required applications access to the device parameters through a TCP/IP connection. As application layer protocol for the Client Server communication a special binary protocol and a text protocol based on XML are considered.
TUP47	The Photo Injector Test Facility at DESY Zeuthen: Results of the First Phase	375
	A. Oppelt, K. Abrahamyan, I. Bohnet, J. Bähr, U. Gensch, H.-J. Grabosch, J.H. Han, M. Krasilnikov, D. Lipka, V. Miltchev, B. Petrosyan, L. Staykov, F. Stephan DESY Zeuthen, Zeuthen W. Ackermann, W.F.O. Müller, S. Setzer, T. Weiland TU Darmstadt, Darmstadt J.-P. Carneiro, K. Flöttmann, S. Schreiber DESY, Hamburg E. Jaeschke, D. Krämer, D. Richter, M. von Hartrott BESSY GmbH, Berlin P. Michelato, C. Pagani, D. Sertore INFN/LASA, Segrate (MI) J. Rossbach Uni HH, Hamburg W. Sandner, I. Will MBI, Berlin I. Tsakov INRNE, Sofia
	The photo injector test facility at DESY Zeuthen successfully concluded it's first phase of operation in November 2003 (PITZ1). After a complete characterization of the injector, the gun has been delivered to Hamburg and has already been taken into operation on the VUV-FEL. The measurement program for the year 2003 included RF commissioning, emittance studies, momentum and bunch length measurements, and studies of the influence of the drive laser parameters. We provide an overview on the latest achievements in all of these topics.
	Transparencies
TUP48	Progress Report on the Flat Beam Experiment at the Fermilab/Nicadd Photoinjector Laboratory	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	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)
TUP50	Cumulative Beam Breakup with Time-Dependent Parameters	384
	J. R. Delayen Jefferson Lab, Newport News, Virginia
	A general analytical formalism developed recently for cumulative beam breakup (BBU) in linear accelerators with arbitrary beam current profile and misalignments [1] is extended to include time-dependent parameters such as energy chirp or rf focusing in order to reduce BBU-induced instabilities and emittance growth. Analytical results are presented and applied to practical accelerator configurations. [1] J. R. Delayen, Phys. Rev. ST Accel. Beams 6, 084402 (2003)
TUP52	Methods for Measuring and Controlling Beam Breakup in High Current ERLs	387
	C. Tennant, K. Jordan, E. Pozdeyev, R.A. Rimmer, H. Wang Jefferson Lab, Newport News, Virginia S. Simrock DESY, Hamburg
	It is well known that high current Energy Recovery Linacs (ERL) utilizing superconducting cavities are susceptible to a regenerative type of beam breakup (BBU). The BBU instability is caused by the transverse deflecting higher-order modes (HOMs) of the cavities which can have high impedance. We present MATLab simulation results for the BBU stability using the analysis tools of control theory. In this framework, methods of experimentally determining the threshold current and the means of suppressing the onset of the instability become more transparent. A scheme was developed to determine the threshold current due to a particular HOM by measuring the decay and rise times of the mode's field in response to an amplitude modulated beam as a function of the average electron beam current. To combat the harmful effects of a particularly dangerous mode, two methods of directly damping HOMs through the cavity HOM couplers were demonstrated. In an effort to suppress the BBU in the presence of multiple, dangerous HOMs, a conceptual design for a bunch-by-bunch transverse feedback system has been developed. By implementing beam feedback, the threshold for instability can be increased substantially.
TUP53	Temporal Profile of the LCLS Photocathode Ultraviolet Drive Laser Tolerated by the Microbunching Instability	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.
TUP54	Resistive-Wall Wake Effect in the Beam Delivery System	393
	J. Wu SLAC, Menlo Park, California J. R. Delayen Jefferson Lab, Newport News, Virginia T.O. Raubenheimer SLAC/NLC, Menlo Park, California J.-M. Wang BNL/NSLS, Upton, Long Island, New York
	The resistive wall instability is investigated in the context of the final beam delivery system of linear colliders. The emittance growth is calculated analytically and compared against the results of full numerical simulations. Criteria for the design of final beam delivery systems are developed.
TUP56	Simulation of RF Breakdown Effects on NLC Beam	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	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	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.
TUP61	Beam Analysis Using the IPNS Linac ESEM	405
	J.C. Dooling, F. R. Brumwell, L. Donley, G.E. McMichael, V. F. Stipp ANL, Argonne, Illinois
	The Energy Spread and Energy Monitor (ESEM) is an on-line, non-intrusive diagnostic used to characterize the output beam from the 200 MHz, 50 MeV linac. The energy spread is determined from a 3-size, longitudinal emittance measurement and energy is derived from TOF analysis. Presently, a single particle distribution is used to yield energy and energy-spread results. Effort is on-going to allow for more realistic distributions to be included. Signals are detected on terminated 50 Ω, stripline BPMs. Each BPM is constructed with four striplines: top, bottom, left and right. Until recently, the ESEM signals were taken solely from bottom striplines in four separate BPM locations in the transport line between the linac and synchrotron. We have begun to use the top stripline data to examine, in more detail, beam position and attempt to measure beam size. The electrostatic coupling between the stripline and the beam depends on the capacitance, which in turn is inversely related to the beam-stripline separation. The electrostatic portion of fluctuations in beam motion will be nonlinear, possibly allowing one to infer beam size.
TUP63	The First Results of Bunch Shape Measurements in SNS Linac	408
	A. Feschenko, A. Gaidash, Yu. Kisselev, L.V. Kravchuk, A. Liyu, A. Menshov, A.N. Mirzojan RAS/INR, Moscow S. Assadi, W. Blokland, S. Henderson, E.P. Tanke ORNL/SNS, Oak Ridge, Tennessee D.-O. Jeon ORNL, Oak Ridge
	Three Bunch Shape Monitors with transverse scanning of low energy secondary electrons for the SNS Linac have been developed and fabricated. The peculiarity of the detectors is using of energy separation of the electrons. The separation enables to minimize influence of detached electrons originated from dissociation of H-minus ions in the detector wire target. The first detector was used at the exit of the first DTL tank during its commissioning. The results of Bunch Shape measurements are presented and discussed. These results were used to verify beam quality, to set parameters of the accelerating field, to estimate a longitudinal beam halo and to restore a longitudinal beam emittance.
	Transparencies
TUP64	Bunch Length Measurements at LEBRA	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	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	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.
TUP67	Beam-Based Alignment Measurements of the LANSCE Linac	420
	R.C. McCrady, L. Rybarcyk LANL, Los Alamos, New Mexico
	We have made measurements of the alignment of the LANSCE Drift Tube linac (DTL) and Side Coupled linac (SCL) using beam position measurements and analyzing them with linear models. In the DTL, we varied the injection steering, measured the beam position after each DTL tank, and analyzed the data with a linear model using R-matrices that were computed by the Trace-3D computer program. The analysis model allowed for tank-to-tank misalignments. The measurements were made similarly in the SCL, where the analysis model allowed for misalignments of each quadrupole doublet lens. We present here the analysis techniques, the resulting alignment measurements and comparisons to measurements made with optical instruments.
TUP68	The LANSCE Low Momentum Beam Monitor	423
	R. Merl LANL, Los Alamos, New Mexico F. R. Gallegos, C. Pillai, S. Schaller, F. E. Shelley, A. I. Steck LANL/LANSCE, Los Alamos, New Mexico B. J. Sanchez ORNL/SNS, Oak Ridge, Tennessee
	A diagnostic has been developed at the Los Alamos Neutron Science Center (LANSCE) for the purpose of identifying low momentum beam tails in the linear accelerator. These tails must be eliminated in order to maintain the transverse and longitudinal beam size. Instead of the currently used phosphor camera system, this instrument consists of a Multi Wire Proportional Chamber (MWPC) front end coupled to an EPICS compliant VME-based electronics package. Low momentum tails are detected with a resolution of 5 mm in the MWPC at a high dispersion point near a bending magnet. While phosphor is typically not sensitive in the nano amp range, the MWPC is sensitive down to about a pico amp. The electronics package processes the signals from each of the MWPC wires to generate an array of beam currents at each of the lower energies. The electronics has an analog front end with a high-speed analog to digital converter for each wire. Data from multiple wires are processed with an embedded digital signal processor and results placed in a set of VME registers. An EPICS application assembles the data from these VME registers into a display of beam current vs. beam energy (momentum) in the LANSCE control room.
TUP69	Precision Alignments of Stripline BPMs with Quadrupole Magnets for TTF2	426
	G. Priebe, D. Nölle, M. Wendt, M. Werner DESY, Hamburg
	We report on our alignment setup to calibrate beam position monitors (BPM) with respect to the magnetic axis of the quadrupole magnets used in the warm sections of the TESLA Test Facility (TTF2). The Stripline BPM's are fixed inside the quadrupole magnets. A streched wire measurement was used to calibrate the electrical axis of the BPM wrt. to the magnetic axis of the quadrupole.
TUP70	Systematic Calibration of Beam Position Monitor in the High Intensity Proton Accelerator (J-PARC) LINAC	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.
TUP71	Highly Sensitive Measurements of the Dark Current of Superconducting Cavities for TESLA Using a SQUID Based Cryogenic Current Comparator	432
	W. Vodel, R. Neubert, S. Nietzsche FSU, Jena K. Knaack, M. Wendt, K. Wittenburg DESY, Hamburg A. Peters GSI, Darmstadt
	This contribution presents a Cryogenic Current Comparator (CCC) as an excellent tool for detecting dark currents generated, e.g. by superconducting cavities for the upcoming TESLA project (X-FEL) at DESY. To achieve the maximum possible energy the gradient of the superconducting RF cavities should be pushed close to the physical limit of 50 MV/m. The undesired field emission of electrons (so-called dark current) of the superconducting RF cavities at strong fields may limit the maximum gradient. The absolute measurement of the dark current in correlation with the gradient will give a proper value to compare and classify the cavities. The main component of the CCC is a highly sensitive LTS-DC SQUID system which is able to measure extremely low magnetic fields, e.g. caused by the dark current. For this reason the input coil of the SQUID is connected across a special designed toroidal niobium pick-up coil for the passing electron beam. A noise limited current resolution of nearly 2 pA/√(Hz) with a measurement bandwidth of up to 70 kHz was achieved in the laboratory. Design issues of the CCC and the application in the CHECHIA cavity test stand at DESY as well as experimental results will be discussed.
TUP72	TTF II Beam Monitors for Beam Position, Bunch Charge and Phase Measurements	435
	M. Wendt, D. Nölle DESY, Hamburg
	An overview of the basic beam instrumentation with regard to elecromagnetic beam monitors for the TESLA Test Facility phase II (TTF II) is given. Emphasis is put on beam position monitor (BPM) and toroid transformer systems for beam orbit and bunch charge observations. Furthermore broadband monitors, i.e. wall current and bunch phase monitors, are briefly presented.
TUP73	Beam Instrumentation Using BPM System of the SPring-8 Linac	438
	K. Yanagida, T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, A. Mizuno, S. Suzuki, T. Taniuchi, H. Tomizawa JASRI-SPring-8, Hyogo
	A beam position monitor (BPM) system of the SPring-8 linac has been operated since 2002. The following upgrade programs have been carried out during this period: The BPMs were installed in the linac's dispersive sections. A synchronized accumulation of beam position data into the database system started. A feedback control of steering magnets for beam position stabilization has been under development. In this conference the authors report a performance of the BPM system, and discuss its usefulness for beam diagnostics, machine diagnostics and beam stabilization.
TUP74	The Beam Diagnostics System in the J-PARC LINAC	441
	S. Lee, Z. Igarashi, T. Toyama KEK, Ibaraki H. Akikawa JAERI/LINAC, Ibaraki-ken F. Hiroki, J. Kishiro, S. Sato, M. Tanaka, T. Tomisawa JAERI, Ibaraki-ken H. Yoshikawa JAERI/FEL, Ibaraki-ken
	Large amount of beam monitors will be installed in J-PARC linac. Electrostatic computations are used to adjust the BPM cross-section parameters to obtain 50 Ω transmission lines. BPMs are designed to control the offset between quadrupole magnet and BPM electrical centers less than 0.1mm. We present a procedure of beam based calibration/alignment (BBC/BBA) method to confirm the displacement of linac BPMs. The fast current transformer (FCT) has response of relative bunch phase <1%. To measure the beam energy at every accelerator tank and injection point of 3 GeV RCS, phase difference of FCT pairs are used, and 10^-4 order energy resolutions can be expected. The loss monitor system (BLM) is composed of scintillator and Ar-CH₄/CO₂ gas filled proportional counter. To prevent the activation and heat load by intense beam loss, fast time response of loss signals is required. Profile measurements can also be used to determine the beam emittance of a matched beam in a periodic focusing lattice. The thin sensing wire scanner (WS) has been designed to obtain a current density distribution of the beam. This paper describes the instruments and R&D result of beam monitors in J-PARC linac.
TUP75	The High Accuracy RF Phase Detector Research for 200 MeV LINAC	444
	S. Dong, G. Huang, D. Jia, G. Li, Y.G. Zhou USTC/NSRL, Hefei, Anhui
	The basic configuration of one experimental RF Phase detector and its research significance is introduced by characteristic of Hefei 200 MeV RF Linear accelerator and developments of RF Phase detector technology. The beam energy could be stabilized by implementing RF Phase detector into phase locked system for 5 cascaded accelerator tubes, which composed 200 MeV linac as the injector of Hefei Light Source (HLS). The tabletop experiments are given and the RF Phase detector is tuned in the off-line status. The microwave in 2856 MHz under CW mode is differentiated accurately by the developed RF phase detector. The measured results are better than prediction. The accuracy of the basic configuration of the RF Phase detector is verified, which establishes foundations for further in-line experiments.
TUP76	Adaptive Feedforward Cancellation of Sinusoidal Disturbances in Superconducting RF Cavities	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.
TUP77	Status of RF Control System for ISAC II Superconducting Cavities	450
	K. Fong, S. Fang, M.P. Laverty TRIUMF, Vancouver
	The rf control system for ISAC II superconducting cavities is a hybrid analogue/digital system using self-excited feedback loop. It has undergone more than a year of testing and improvements have been made to every aspect of the system, including power up sequencing, phase detection, loop regulation, data acquisition as well as communication with EPICS. With a loaded Q of 100,000, amplitude regulation bandwidth of 20 Hz, phase regulation bandwidth of 5 Hz have been achieved.
TUP78	Diagnostics for the Low Level RF Control for the European XFEL	453
	T. Jezynski, P. Pucyk WUT, Warsaw S. Simrock DESY, Hamburg
	One of the most important aims of the diagnostic system is to provide high reliability. This article describes the concept and the proposal for diagnostic system for Low Level Radio Frequency system for EU-XFEL. It enables immediate location of faults and understanding of their causes, tests the functionality of LLRF system, tests each the electronic board and connections. Diagnostic system tests different system components and compares results from these tests with e.g. from power supplies monitors. Hardware, software and database aspect of diagnostic system is presented. The main part of this paper is devoted to hardware and software specification.
TUP79	A New RF System for the CEBAF Normal Conducting Cavities	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.
TUP80	A Long-Pulse Modulator for the TESLA Test Facility (TTF)	459
	W. Kaesler PPT, Dortmund
	The long-pulse (1.6 ms) klystron modulator for TTF is a hardtube pulser using a Bouncer-circuit for droop compensation. It is built up with new advanced components representing industrial standards. The on-/off switch is a rugged 12 kV IGCT-stack with a fast 4kA turn-off capability. The 100 kJ storage capacitor bank contains only three capacitors with self-healing, segmented PP-foil technology. A new 100 kA solid-state switch based on light triggered thyristors (LTT) replaced the standard ignitrons as crowbar switches. The 300 kW high voltage power supply is based on modern switched mode technology.
TUP81	Superstrong Adjustable Permanent Magnet for a Linear Collider Final Focus	462
	Y. Iwashita, T. Mihara Kyoto ICR, Kyoto A. Evgeny, M. Kumada NIRS, Chiba-shi C. M. Spencer SLAC, Menlo Park, California E. Sugiyama NEOMAX, Osaka
	Super-strong permanent magnets are being considered as one of the candidates for the final focus quadrupole magnets in a linear collider. A short prototype with temperature compensation included and variable strength capability has been designed and fabricated. Fabrication details and some magnetic measurement results will be presented.
	Transparencies
TUP82	Low Energy Beam Transport using Space Charge Lenses	465
	O. Meusel, A. Bechtold, H. Klein, J. Pozimski, U. Ratzinger, A. Schempp IAP, Frankfurt-am-Main
	Gabor lenses provide strong cylinder symmetric electric focusing using a confined nonneutral plasma. The density distribution of the enclosed space charge is defined by the enclosure conditions in transverse and longitudinal direction. For a homogeneous charge density distribution the resulting electrostatic field and therefrom the focusing forces inside the space charge cloud are linear. Additionally in case of a positive ion beam the space charge of the confined electrons causes compensation of the ion beam space charge forces. To study the capabilities of a Gabor double lens system to match an ion beam into a RFQ a testinjector was installed at the IAP and put into operation successfully. First beam profiles and emittance measurements as well as measurements of the beam energy and energy spread have already been performed and show satisfactory results and no significant deviation from the theoretical predictions. To verify the beam focusing of bunched beams using this lens type at beam energies up to 500 keV a new high field Gabor lens was build and will be installed behind of the RFQ.
TUP83	Results of the Magnetic Field Measurements of the DTL Quadrupole Magnets for the J-PARC	468
	E. Takasaki, F. Naito, H. Tanaka, K. Yoshino KEK, Ibaraki H. Ino, Z. Kabeya, S. Kakizaki, T. Kawasumi Mitsubishi Heavy Industries Ltd., Nagoya Aerospace Systems Works, Nagoya T. Itou JAERI/LINAC, Ibaraki-ken
	A quadrupole electromagnet is installed in the drift tube, which has an outer diameter of 140 mm and its minimum length of 53 mm. Hence, a coil of this magnet was made by the advanced periodic reverse copper electroforming method instead of the conventional hollow conductor. Recently, 149 quadrupole electromagnets were completed and then installed in the drift tube within a high accuracy. The magnetic field measurements have been carried out with two different measurement methods at each stage of the manufacturing process. The discrepancies between the magnetic field center and the mechanical center are within about ±35 μm after installation of the quadrupole magnet inside the drift tube. This paper will describe methods and results of the magnetic field measurements.
TUP84	Spectrographic Approach to Study of RF Conditioning Process in Accelerating RF Structures	471
	H. Tomizawa, H. Hanaki, T. Taniuchi JASRI-SPring-8, Hyogo A. Enomoto, Y. Igarashi, S. Yamaguchi KEK, Ibaraki
	The acceleration gradient of a linac is limited by rf breakdown in its accelerating structure. We applied an imaging spectrograph system to study the mechanism of rf breakdown phenomena in accelerating rf structures. Excited outgases emit light during rf breakdown, and the type of outgases depend on surface treatments and rinsing methods for their materials. To study rf breakdown, we used 2-m-long accelerating structures and investigated the effects when high-pressure ultrapure water rinsing (HPR) treatment was applied to these rf structures. We performed experiments to study the outgases under rf conditioning with quadruple mass spectroscopy and imaging spectrography. As a result, we could observe instantly increasing signals at mass numbers of 2 (H₂), 28 (CO), and 44 (CO₂), but not 18 (H₂O) just after the rf breakdown. We also conducted spectral imaging for the light emissions from the atoms in a vacuum that are excited by rf breakdown. Without HPR, we observed the atomic lines at 511 nm (Cu I), 622 nm (Cu II), and 711 nm (C I). With HPR, 395 nm (O I), 459 nm (O II), 511 nm (Cu I), 538 nm (C I), 570 nm (Cu I), 578 nm (Cu I), 656 nm (H I), and 740 nm (Cu II) were observed.
TUP85	J-PARC Linac Alignment	474
	M. Ikegami, C. Kubota, F. Naito, E. Takasaki, H. Tanaka, K. Yoshino KEK, Ibaraki H. Ao, T. Itou JAERI/LINAC, Ibaraki-ken K. Hasegawa, T. Morishita, N. Nakamura, 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, and its total length is more than 400 m including the beam transport line to the succeeding RCS (Rapid Cycling Synchrotron). In high-current proton accelerators, precise alignment of accelerator components is indispensable to reduce uncontrolled beam loss and beam quality deterioration. In this paper, planned schemes for the linac alignment is presented together with instrumentation for the long-term ground-motion watching.
TUP86	Coupler Development and Gap Field Analysis for the 352 MHz Superconducting CH-Cavity	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.
TUP87	Technologies of The Peripheral Equipments of The J-PARC DTL1 for the Beam Test	480
	K. Yoshino, Y. Fukui, E. Kadokura, T. Kato, C. Kubota, F. Naito, E. Takasaki, H. Tanaka KEK, Ibaraki T. Itou JAERI/LINAC, Ibaraki-ken
	First beam test of the DTL1 was performed in November of 2003 at KEK site. A 30 mA H^- beam was successfully accelerated from 3 to 19.7 MeV. In order to prepare the beam test, various peripheral equipments were developed: the electrode plates for connecting the hollow-conductor coil and the power cable were developed since quadrupole electromagnets are built in all DTs (77 sets) of the DTL1, the water-cooled multiconductor copper tube (Control Copper Tube) were used as the power cable from the electrode plate to power supply, and the interlock system assembled by PLCs (Programmable Logic Controller) was also prepared for the surveillance of many cooling channel.
TUP88	CLIC Magnet Stabilization Studies	483
	S. Redaelli, R.W. Assmann, W. Coosemans, G. Guignard, D. Schulte, I. Wilson, F. Zimmermann CERN, Geneva
	One of the main challenges for future linear colliders is producing and colliding high energy e⁺e^- beams with transverse spot sizes at the collision point in the nanometre range. Preserving small emittances along several kilometres of linac requires the lattice quadrupoles to be stable to the nanometre level. Even tighter requirements are imposed on the stability of the final focus quadrupoles, which have to be stable to a fraction of the colliding beam size to reliably steer the opposing beams in collision. The Compact LInear Collider (CLIC), presently under investigation at CERN, aims at colliding e⁺e^- beams with a vertical spot size of 0.7 nm, at a centre-of-mass energy of 3 TeV. This requires a vertical stability to the 1.3 nm level for the 2600 linac quadrupoles and to the 0.2 nm level for the two final focus quadrupoles. The CLIC Stability Study has demonstrated for the first time that CLIC prototype quadrupoles can be stabilized to the 0.5 nm level in a normal working area on the CERN site. Detailed tracking simulations show that with this level of stability, approximately 70% of the CLIC design luminosity would be achieved. This paper summarizes the work and the achievements of the CLIC Stability Study.
	Transparencies
TUP89	Static Absolute Force Measurement for Preloaded Piezoelements Used for Active Lorentz Force Detuning System	486
	S. P. Sekalski, A. Napieralski, S. P. Sekalski TUL, Lodz A. Bosotti INFN/LASA, Segrate (MI) M. Fouaidy IPN, Orsay L. Lilje, S. Simrock DESY, Hamburg R. Paparella, P.F. Puricelli INFN Milano, Milano
	To reach high gradients in pulsed operation of superconducting (SC) cavities an active Lorentz force detuning compensation system is needed. For this system a piezoelement can be used as an actuator (other option is a magnetostrictive device). To guarantee the demanded lifetime of the active element, the proper preload force adjustment is necessary. To determine this parameter an absolute force sensor is needed which will be able to operate at cryogenic temperatures. Currently, there is no calibrated commercial available sensor, which will be able to measure the static force in such an environment. The authors propose to use a discovered phenomenon to estimate the preload force applied to the piezoelement. The principle of the proposed solution based on a shape of impedance curve, which changes with the value of applied force. Especially, the position of resonances are monitored. No need of specialized force sensor and measurement in-situ are additional advantages of proposed method.
TUP90	Improvements of RF Characteristics in the SDTL of the J-PARC Proton LINAC	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)
TUP91	Compact Electron-Linac Design Concept for a Gamma Ray Source	492
	K. C. D. Chan, B.E. Carlsten, G. Dale, R. Garnett, C. Kirbie, F.L. Krawczyk, S.J. Russell, T.P. Wangler LANL, Los Alamos, New Mexico E. Wright CPI, Palo Alto, California
	Gamma-ray sources, particularly sources that are easily transportable, are in high demand for different homeland security applications. We have carried out a review of commercially available electron-linac-based sources, and have investigated alternative compact electron-linac systems that use updated technologies compared with sources that are available commercially. As the results, we propose to develop a new source using an electron linac operating at 17 GHz. It uses a klystron, instead of a magnetron, and a IGBT-switched HV power supply. The source design takes advantages of the advances in X-band linac technology and solid-state HV technology. The higher frequency and upgraded technologies offer smaller size, lighter weight, better efficiency, easier operation, and higher reliability, compared with commercially-available linacs. In this paper, we will describe the source design and our choice of technologies.
TUP93	Results of a 3D-EM-Code Comparison on the TRISPAL Cavity Benchmark	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
TUP94	Parallel Particle in Cell Computation of an Electron Gun with GdfidL	498
	W. Bruns TU Berlin TET, Berlin
	The paper describes an efficient algorithm to integrate the equations of a fast moving charge cloud of small size in a large electron gun. Particle in cell computations of a realistic electron gun is challenging due to the large discrepancy between the size of the cavity and the size of the cloud. A fine grid must be used to resolve the small volume of the charge, with a grid spacing in the order of 0.1 mm. The cavity has extensions of about 100 mm. Therefore one has to deal with about 1000 million gridcells. Such a large grid is handled best with parallel systems. Each node of the parallel system computes the electromagnetic field in its subvolume. As the extension of the charge keeps being small during the flight, at each timestep the charged particles will be located in only a few subvolumes of the nodes of the parallel system. This would lead to a strong load imbalance, if the particle related computations for each particle would be performed by the node where the particle is in. GdfidL instead spreads the data of all particle over all processors, which perform the particle related computations, and send back the results to the processors where the particles are in.
TUP95	Evaluation of Magnetic Field Enhancement Along a Boundary	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	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	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.
TUP98	The Finite State Machine for Klystron Operation for VUV-FEL and European X-FEL Linear Accelerator	510
	W. Cichalewski, B. Koseda, A. Napieralski TUL, Lodz F.-R. Kaiser, S. Simrock DESY, Hamburg
	In order to provide a pulsed RF power signal that fulfills all designers and users demands the work on power supplies, pulse transformers, waveguides and klystrons has to be well coordinated. Because operators not engineers will operate mention user facility therefore software has to be implemented in order to automate the enormous quantity of hardware operation accompanying regular operation of linear accelerator collider. A finite state machine is adequate formal description of reactive systems that has become starting point for designing our control software. To present the complexity of the task that establishing FSM for Klystron system would be, one has to become acquainted with complexity of the system itself. Therefore this article describes the construction and principles of the klystron and modulator as well as ideas concerning the implementation of a FSM for such a system.