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Paper Title Other Keywords Page
MO102 The European XFEL SC Linac Project linac, FEL, undulator, radiation 6
  • R. Brinkmann
    DESY, Hamburg

The European XFEL project is entering the construction phase, based on the very successful experience of the TESLA linac technology and the SASE FEL concept, now serving the FLASH user facility at DESY. The EU-XFEL will be realized by a widespread international collaboration and it is also relevant for the ILC planning. A description of the overall layout of the facility, of the technical developments and industrialization efforts for the accelerator components, and of the international collaboration will be given.


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MOP027 Heavy Ion Injector for NICA/MPD Project ion, rfq, ion-source, linac 121
  • G.V. Trubnikov, E.D. Donets, E.E. Donets, A. Govorov, V. Kobets, I.N. Meshkov, V. Monchinsky, A.O. Sidorin
    JINR, Dubna, Moscow Region
  • O.K. Belyaev, Yu.A. Budanov, A. Maltsev, I.A. Zvonarev
    IHEP Protvino, Protvino, Moscow Region

Goal of the NICA/MPD project under realization at JINR is to start in the coming 5-7 years an experimental study of hot and dense strongly interacting QCD matter and search for possible manifestation of signs of the mixed phase and critical endpoint in heavy ion collisions. The Nuclotron-based Ion Collider fAcility (NICA) and the Multi Purpose Detector (MPD) are proposed for these purposes. The NICA collider is aimed to provide experiment with heavy ions like Au, Pb or U at energy up to 3.5 x 3.5 GeV/u with average luminosity of 1027 cm-2s-1. The existing Nuclotron injection complex consists of HV fore-injector and Alvarez-type linac LU-20. The LU-20 accelerates the protons up to the energy of 20 MeV and ions at Z/A=0.33 up to the energy of 5 MeV/u. New injector designed for efficient operation of the NICA facility is based on Electron String Ion Source providing short (< 10 ns) and intensive (up to 10 mA) pulses of U32+ ions, one section of RFQ and four sections of RFQ Drift Tube Linac accelerating the ions at Z/A=0.12 up to 6 MeV/u of the kinetic energy. General parameters of the injector are discussed.

MOP043 Simulation of Multipacting in HINS Accelerating Structures with CST Particle Studio simulation, cavity, accelerating-gradient, background 166
  • G.V. Romanov
    Fermilab, Batavia

Recently high power tests of the room temperature cross-bar H-type resonators (CH resonators) and high gradient tests of a superconducting single spoke resonator (SSR) have been performed under the High Intensity Neutrino Source (HINS) project at Fermilab. The resonators have shown a tendency of having multipacting at various levels of input power and therefore longer processing time. To provide insights for the problem, detailed numerical simulations of multipacting for these resonators have become necessary. New generation of accelerating structures like superconducting spoke resonators and room temperature CH resonators need a full 3D treatment. Simulations and study of multipacting in the resonators have been carried out using CST Particle Studio. The problematic regions and power levels have been identified for both types of resonators. This presentation will give the result of simulations and comparison with experimental data.

MOP063 High-Power Lithium Target for Accelerator-Based BNCT target, linac, neutron, gun 223
  • C.A. Willis, D.A. Swenson
    Linac Systems, LLC, Albuquerque, New Mexico

A 50 kW, water-cooled conical target for producing neutrons via the Li-7(p,n)Be-7 reaction at 2.5 MeV proton energy is under development at Linac Systems. This target is intended to accept a stationary, expanded CW beam with a diameter of 8 cm directly from an rf linac, resulting in peak surface heat flux of 7.5 MW m-2 (a 'waterbag' beam power distribution is assumed). The target is predicted to meet the intensity requirements for practical accelerator-based boron neutron capture therapy (BNCT), in concert with Linac Systems' CW RFI linac. Lithium metal targets present well-known physical and mechanical challenges at high beam power density that are addressed in our design. For instance, lithium melts at 180 C, necessitating efficient removal of heat at a low ΔT relative to ambient temperature. CFD modeling indicates that with 50 kW incident beam power, the peak lithium temperature can be held below 150 C with a water flow rate near 80 l min-1 and corresponding pressure drop of 170 kPa. The target prototype has been fabricated and is undergoing experimental thermal-hydraulic testing using an electron beam at the Plasma Materials Test Facility, Sandia National Laboratory.

MOP064 Bent Solenoid Tuning Simulations for the COMET Beamline solenoid, simulation, target, dipole 226
  • A. Kurup
    Imperial College of Science and Technology, Department of Physics, London

The COMET experiment beamline uses bent solenoids for the muon transport and the spectrometer used to analyse the decay electrons from stopped muons. The bent solenoid includes not just a solenoid field but also a vertical dipole field. It is therefore important to have the ability to tune the field distribution. However, since the field distribution is mainly determined by the geometry it is difficult to adjust once the solenoids have been constructed. A cost effective method to provide tuning capability of the field distribution of the bent solenoids is proposed and the results of simulations presented.

MOP067 High Gradient Excitation and RF Power Generation Using Dielectric Loaded Wakefield Structures wakefield, gun, klystron, laser 232
  • M.E. Conde, S.P. Antipov, F.J. Franchini, W. Gai, F. Gao, R. Konecny, W. Liu, J.G. Power, Z.M. Yusof
    ANL, Argonne
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio

Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
Dielectric loaded wakefield structures are being developed to be used as high gradient accelerator components. The high current electron beam at the Argonne Wakefield Accelerator Facility was used to excite wakefields in cylindrical dielectric loaded wakefield structures in the frequency range of 8 to 14 GHz, with pulse duration of a few nanoseconds. Short electron bunches (13 ps FWHM) of up to 86 nC drove these wakefields, and accelerating fields as high as 100 MV/m were reached. These standing-wave structures have a field probe near the outer edge of the dielectric to sample the RF fields generated by the electron bunches. Monitoring of the field probe signal serves to verify the absence of electric breakdown. Similar structures were used to extract RF power from the electron beam; however, in this case they were travelling-wave structures, driven by electron bunch trains of up to 16 bunches. RF pulses of up to 40 MW were measured at the output coupler of these structures.

MOP068 Trains of Sub-Picosecond Electron Bunches for High-Gradient Plasma Wakefield Acceleration plasma, wakefield, emittance, simulation 235
  • P. Muggli
    UCLA, Los Angeles, California
  • M. Babzien, K. Kusche, J.H. Park, V. Yakimenko
    BNL, Upton, Long Island, New York
  • M.J. Hogan
    SLAC, Menlo Park, California
  • E. Kallos
    USC, Los Angeles, California

Funding: Work Supported by US Department of Energy
In the plasma wakefield accelerator (PWFA), high quality accelerated electron bunches can be produced by injecting a witness bunch behind a single drive bunch or a train of N bunches. To operate at large gradient the plasma density must be in the 1017/cc range, corresponding to a typical bunch separation of the order of the plasma wavelength or ≈100μm. We have demonstrated that such a sub-picosecond temporal bunch structure can be produced using a mask to selectively spoil the emittance of temporal slices of the bunch*. The bunches spacing, as well as their length can be tailored by designing the mask and choosing the beam parameters at the mask location. The number of bunches is varied by using an adjustable width energy limiting slit. The bunches spacing is measured with coherent transition radiation interferometry. Experimental results will be presented and compared to simulations of the bunch train formation process with the particle tracking code ELEGANT.

*P. Muggli et al., to appear in Phys. Rev. Lett. (2008).

MOP074 Beam Dynamics Simulations of Sub-ps Electron Bunch Produced in a Photo-Injector emittance, simulation, laser, gun 248
  • R. Roux
    LAL, Orsay

A growing number of experiments require low emittance ultra-short electron bunches in the 100 fs range (rms value) for the production of coherent light or the injection in plasma for laser-plasma acceleration. Especially in the last case it is highly desirable to have a compact accelerator; hence a strong experimental activity is carried out to get such a beam directly from a photo-injector. We have performed beam dynamic simulations using the PARMELA code to study the performances of the alphaX photo-injector installed in the University of Strathclyde in UK. This rf gun is aimed to produce electron bunches of 100 pC bunch charge, 100 fs bunch length and 1 mmmrad transverse emittance. We will show the results of systematic parametric studies as a function of charge and laser pulse duration as well as the natural evolution of the beam phase space as a function of the distance from the photo-cathode.

MOP076 Integration of Fringe Field Alpha Magnets into the V-Code Beam Dynamics Simulation Tool simulation, multipole, dipole, focusing 254
  • S. Franke, W. Ackermann, B. Steiner, T. Weiland
    TEMF, TU Darmstadt, Darmstadt
  • J. Enders, C. Heßler, Y. Poltoratska
    TU Darmstadt, Darmstadt

Funding: This work was partially funded by DESY Hamburg and DFG (SFB 634).
At the Superconducting DArmstadter LINear Accelerator (S-DALINAC) a new 100 keV polarized electron source is currently being installed. Therefore, a new low energy injection concept has to be designed. One of the main components of the injector are a polarized electron source, an alpha magnet and a Wien filter used for spin rotation as well as various beam forming elements. Fast beam dynamics simulations can advantageously assist the design process because of the flexible parameter variations combined with nearly simultaneous solution responses. Based on the moment approach a fast tracking code named V-Code has been implemented at TEMF. In order to simulate the entire injector an alpha magnet model was added to the V-Code database of beam line elements. In this paper a summary of issues regarding the implementation complemented with simulation results will be provided.

MOP082 Multipacting Simulation in RF Structures simulation, multipactoring, cavity, linac 266
  • N.P. Sobenin, M. Gusarova, V.I. Kaminsky, S.V. Kutsaev, M.V. Lalayan
    MEPhI, Moscow
  • L.V. Kravchuk, S.G. Tarasov
    RAS/INR, Moscow

A new computer code for 3D simulation of multipacting phenomenon in axisymmetric and non-axisymmetric rf structures is presented. The goal of the simulation is to determine resonant electron trajectories and electron multiplication in rf structure. Both SW and TW structures of normal- and superconductivity have been studied. Simulation results are compared with theoretical calculations and experimental measurements.

MOP083 Analysis of Input Coupler Asymmetry Influence on Beam Dynamics in Accelerators with Superconducting Cavities emittance, cavity, superconducting-cavity, simulation 269
  • N.P. Sobenin, S.V. Kutsaev, M.V. Lalayan, V.A. Makarov
    MEPhI, Moscow
  • A.A. Krasnov
    ScanTech, Atlanta, Georgia
  • V.I. Shvedunov
    MSU, Moscow
  • A.A. Zavadtsev
    Introscan, Moscow

Analysis of input coupler asymmetry influence on beam dynamics in superconducting cavities of Energy Recovery Linac (ERL) injector is presented. Both coaxial and waveguide, single and twin input couplers were analyzed. Using computer simulation electromagnetic fields distribution in accelerating cavity was obtained and recalculated to the transverse-kick to the bunch passing the coupler. Also calculation of external coupling was done. RTMTRACE code was adapted for particle beams dynamic simulation. Acceptable transverse emittance growth was achieved for twin-coaxial (4%) and waveguide (5%) input coupler designs.


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MOP087 Status of Longitudinal Beam Dynamics Studies in CTF3 simulation, wakefield, space-charge, cavity 278
  • H. Shaker
    IPM, Tehran
  • E. Adli
    University of Oslo, Oslo
  • R. Corsini, A.E. Dabrowski, A. Latina, T. Lefèvre, H. Shaker, P.K. Skowronski, F. Tecker, P. Urschütz
    CERN, Geneva

The aim of the CLIC Test Facility CTF3, built at CERN by an international collaboration, is to address the main feasibility issues of the CLIC electron-positron linear collider technology by 2010. One key-issue studied in CTF3 is the generation of the very high current drive beam, used in CLIC as the rf power source. It is particularly important to simulate and control the drive beam longitudinal dynamics in the drive beam generation complex, since it directly affects the efficiency and stability of the rf power production process. In this paper we describe the ongoing effort in modelling the longitudinal evolution of the CTF3 drive beam and compare the simulations with experimental results.

MOP092 Monte Carlo Simulation of Touschek Effects in a Linac Beam scattering, simulation, beam-losses, linac 293
  • A. Xiao, M. Borland
    ANL, Argonne

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
We present a Monte-Carlo method implemented in the code elegant for simulating Touschek scattering effects in a linac beam. The local scattering rate and the distribution of scattered particles can be obtained from the code. In addition, scattered particles can be tracked to the end of the beam line and the local beam loss rate and beam halo information recorded. This information can be used for beam collimation system design.

MOP098 The Open Architecture Software Integration System (OASIS) for Creating PBO Lab Modules optics, target 302
  • G.H. Gillespie, W. Hill
    G.H. Gillespie Associates, Inc., Del Mar, California

A specialized software package has been developed that enables the rapid implementation of custom beam optics modules that run in the Particle Beam Optics Laboratory (PBO Lab). PBO Lab is a commercially available software application that supports a suite of accelerator codes for design, operations, and personnel education. The intuitive and easy-to-use graphic user interface (GUI) is largely responsible for the popularity of PBO Lab. The Open Architecture Software Integration System, or OASIS, builds upon the capability of PBO Lab to host a suite of different codes, and provides an innovative framework that allows users to readily integrate their own optics programs into PBO Lab. The OASIS GUI can be used to readily create new PBO Lab modules without writing or compiling any source code. OASIS has been used to develop several new modules for PBO Lab. This paper presents a summary of the OASIS framework and describes some of the features used in creating the new PBO Lab modules for several popular optics codes.

MOP101 Simulation of Emittance Growth Using the UAL String Space Charge Model simulation, emittance, space-charge, synchrotron 308
  • R.M. Talman
    CLASSE, Ithaca, New York
  • N. Malitsky
    BNL, Upton, Long Island, New York
  • F. Stulle
    CERN, Geneva

Evolution of short intense electron bunches passing through bunch-compressing beamlines is simulated using the UAL (Unified Accelerator Libraries) string space charge formulation. Excellent agreement is obtained with results obtained experimentally at CTF-II, the CERN "Compact Linear Collider'' test facility. The 40 MeV energy of these data is low enough for Coulomb and Biot-Savart forces to be important and high enough for coherent synchrotron radiation and centrifugal space charge forces to be important. UAL results are also compared with CSRtrack results for emittance growth in a 40 MeV 'standard' chicane. Vertical space charge forces are found to be important in this (low energy) case.

MOP102 Electron Beam Dynamics in the DARHT-II Linear Induction Accelerator induction, dipole, focusing, impedance 311
  • C. Ekdahl, E.O. Abeyta, P. Aragon, R.D. Archuleta, G.V. Cook, D. Dalmas, K. Esquibel, R.J. Gallegos, R.W. Garnett, J.F. Harrison, E.B. Jacquez, J.B. Johnson, B.T. McCuistian, N. Montoya, S. Nath, K. Nielsen, D. Oro, L.J. Rowton, M. Sanchez, R.D. Scarpetti, M. Schauer, G.J. Seitz, H.V. Smith, R. Temple
    LANL, Los Alamos, New Mexico
  • H. Bender, W. Broste, C. Carlson, D. Frayer, D. Johnson, C.-Y. Tom, C.P. Trainham, J.T. Williams
    NSTec, Los Alamos, New Mexico
  • T.C. Genoni, T.P. Hughes, C.H. Thoma
    Voss Scientific, Albuquerque, New Mexico
  • B.A. Prichard, M.E. Schulze
    SAIC, Los Alamos, New Mexico

Funding: Work supported by USDOE under contract DE-AC52-06NA25396
The DARHT-II linear induction accelerator (LIA) accelerates a 2 kA electron beam to more than 17 MeV. The beam pulse has a greater than 1.5-microsecond flattop region over which the electron kinetic energy is constant to within 1%. The beam dynamics are diagnosed with 21 beam-position monitors located throughout the injector, accelerator, and after the accelerator exit, where we also have beam imaging diagnostics. I will discuss the tuning of the injector and accelerator, and I will present data for the resulting beam dynamics. Beam motion at the accelerator exit is undesirable for its application as a bremsstrahlung source for multi-pulse radiography of explosively driven hydrodynamic experiments. I will discuss the tuning procedures and other methods we use to minimize beam motion, and to suppress the beam-breakup (BBU) and ion-hose instabilities*.

*"Long-pulse beam stability experiments on the DARHT-II linear induction accelerator", Carl Ekdahl, et al., IEEE Trans. Plasma. Sci. Vol. 34, 2006, pp. 460-466.

MOP110 Precise Control of Cooling Water System for Stabilization of 125 MeV Linac at LEBRA linac, klystron, FEL, target 331
  • T. Sakai, M. Inagaki, T. Kuwada, I. Sato
    Nihon University, Advanced Research Institute for the Sciences and Humanities, Funabashi
  • K. Hayakawa, Y. Hayakawa, K. Nakao, K. Nogami, Y. Takahashi, T. Tanaka
    LEBRA, Funabashi

The 125 MeV linac at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been used for generation of the near-infrared FEL and the Parametric X-ray Radiation (PXR). Currently the FELs from 0.86 to 6 microns and the PXR X-rays from 5 to 20 keV are available at LEBRA. Precise experiments using the light sources require a high stability in both the wavelength and the intensity of the lights. Though the linac was operated with the cooling water stabilized at 30 plus or minus 0.2 deg C, periodical fluctuation of the electron beam energy and the beam orbit suggested that the stability of the cooling water temperature was not sufficient. With this condition a large fluctuation (plus or minus 15%) was observed for the PXR intensity. After the improvement of the fine cooling water system and the water flow path, fluctuation of the cooling water temperature at the supply head of the accelerating tubes and the electromagnets was suppressed to within plus or minus 0.01 deg C. As a result of the improvement the PXR intensity fluctuation at the X-ray output port has been suppressed to within plus or minus 2% for the operation over several hours.

TU301 Positron Beams Propagation in Plasma Wakefield Accelerators plasma, positron, emittance, laser 374
  • P. Muggli
    UCLA, Los Angeles, California

Funding: Work Supported by US Department of Energy
Plasma-based accelerators are one of the emerging technologies that could revolutionize e-/e+ colliders, significantly reducing their size and cost by operating at multi-GeV/m accelerating gradients. Proof-of-principle experiments at SLAC have demonstrated the energy doubling of 42 GeV incoming e- in a plasma only ≈85 cm-long,* corresponding to an unloaded gradient of ≈50 GeV/m. Plasma wakes driven by e+ bunches are different from those driven by e- bunches. The acceleration of e+ in plasmas has been demonstrate,** but the acceleration of high-quality e+ beams is challenging. Measurements show that single e+ bunches suffer halo formation and emittance growth when propagating through dense meter-scale, uniform plasmas.*** Advanced schemes, such as hollow plasma channels, or e+ bunch acceleration on the wake driven by a e bunch, may have to be used in a future plasma-based linear collider. Experimental results obtained with e+ beams in plasmas will be reviewed and compared to those obtained with e- beams. Future experiments including a new scheme to produce a drive e bunch closely followed by a witness e+ bunch appropriate for PWFA experiments will also be discussed.

*I. Blumenfeld et al., Nature 445, 741-744 (15 February 2007).
**B.E. Blue et al., Phys. Rev. Lett. 90, 214801 (2003).
***P. Muggli et al., accepted for publication in Phys. Rev. Lett. (2008).


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TUP002 ARIEL and the TRIUMF E-Linac Initiative, a 0.5 MW Electron Linac for Rare Isotope Beam Production linac, cavity, TRIUMF, target 383
  • S.R. Koscielniak, F. Ames, R.A. Baartman, I.V. Bylinskii, R.J. Dawson, J.T. Drozdoff, K. Fong, A. Hurst, R. Keitel, R.E. Laxdal, F. Mammarella, M. Marchetto, L. Merminga, A.K. Mitra, K.W. Reiniger, T.C. Ries, R. Ruegg, I. Sekachev, G.M. Stinson, V.A. Verzilov
    TRIUMF, Vancouver
  • D. Karlen
    Victoria University, Victoria, B.C.

TRIUMF, in collaboration with university partners, proposes to construct a megawatt-class electron linear accelerator (e-linac) as a driver for U(γ,f) of actinide targets for nuclear astrophysics studies, and 9Be(γ,p)8Li for beta-NMR materials science. The e-linac is part of a broader proposal for an expansion of the TRIUMF rare isotope beams capability through a new facility to be named ARIEL. The e-linac design and prospects for funding are elaborated.

TUP003 Proposal for a 15 MeV Superconducting Electron Linac for the DEINOS Project laser, linac, high-voltage, cavity 386
  • J.-L. Lemaire, P. Balleyguier, J.-L. Flament, D. Guilhem, V. Le Flanchec, M.M. Millerioux, S.J. Pichon
    CEA, Bruyeres-le-Chatel

The design of a 15 MeV, 2 kA peak current, electron accelerator for the DEINOS project is presented. It is dedicated to a new radiographic facility. The accelerator design is based on a dc photo-injector and a rf superconducting linac. Up to twenty electron micro-pulses, 100 ps time duration and 200 nC bench charge are emitted at 352 MHz repetition rate from a CS2Te photocathode and accelerated to 2.5 MeV in the dc diode before injection into a superconducting linac. A general description of the main accelerator components and the beam dynamics simulations are presented.

TUP007 The Power and Polarisation Upgrade Project at the S-DALINAC Injector cavity, cathode, polarization, vacuum 398
  • R. Eichhorn, R. Barday, U. Bonnes, M. Brunken, J. Conrad, C. Eckardt, J. Enders, H.-D. Gräf, C. Heßler, T. Kuerzeder, C. Liebig, M. Platz, Y. Poltoratska, M. Roth, S.T. Sievers, T. Weilbach
    TU Darmstadt, Darmstadt
  • W. Ackermann, W.F.O. Müller, B. Steiner, T. Weiland
    TEMF, TU Darmstadt, Darmstadt
  • K. Aulenbacher
    IKP, Mainz
  • J.D. Fuerst
    ANL, Argonne

Funding: Work supported by the DFG through SFB 634
At the superconducting Darmstadt linear accelerator S-DALINAC currently two upgrades of the injector are underway: The current upgrade for the injector mainly involves the superconducting rf part. In order to increase the maximum current from 60 uA to 150 or 250 uA the power coupler design had to be modified, resulting in major changes in the whole cryo-module. Second, an additional polarized electron source (SPIN) has been set-up at an offline test area. There, the polarized electrons are produced by photoemission at a strained GaAs cathode on a 100 kV platform. The test beam line includes a Wien filter for spin manipulation, a Mott polarimeter for polarization measurement and additional diagnostic elements. We will give an overview over the project, report on the status and present first measurement results including the proof of polarisation.

TUP008 Recent Changes to the e- / e+ Injector (Linac II) at DESY linac, target, positron, gun 401
  • M. Hüning, M. Schmitz
    DESY, Hamburg

The Linac II at DESY consists of a 6A/150kV DC electron gun, a 400 MeV primary electron linac, a 800 MW positron converter, and a 450 MeV secondary electron/positron linac. The Particle Intensity Accumulator (PIA) is also considered part of the injector complex accumulating and damping the 50 Hz beam pulses from the linac and transferring them with a rate of 6.25 Hz or 3.125 Hz into the Synchrotron DESY II. The typical positrons rates are 6·1010/s. DESY II and Linac II will serve as injectors for the two synchrotron light facilities PETRA III and DORIS. Since PETRA III will operate in top-up mode, Linac availability of 98-99% are required. DORIS requires positrons for operation. Therefore during top-up mode positrons are required for both rings. In order to maintain its reliability over the operation time of the new facility PETRA III, the major components of the linac were renovated. Some components were redesigned taking into account experience from 30 years of operation.

TUP010 Pulse-to-Pulse Mode Switching of KEKB Injector Linac target, injection, positron, linac 407
  • T. Kamitani, K. Furukawa, N. Iida, M. Ikeda, K. Kakihara, M. Kikuchi, T. Mimashi, S. Ohsawa, M. Satoh, A. Shirakawa, T. Sugimura, T. Suwada, K. Yokoyama
    KEK, Ibaraki

KEKB injector linac supplies electron and positron beams to the KEKB storage rings and the synchrotron radiation facility rings (PF, AR) as well. Injection modes to these four destinations are switched by inserting and extracting positron generation target, changing magnet parameters and acceleration rf phases. To enable pulse-by-pulse switching in three out of the four modes, a pulse bend and pulse steerings are introduced. For DC quads and DC steerings, compatible beam-optical settings for beams of different beam-energy profiles are introduced. We have been performing beam studies to establish the pulse-by-pulse mode switching for daily beam operation. This paper describes a scheme for the mode switching and reports on an achievement of the beam studies.

TUP011 Observations of Two Microbunches After a 180-Degree Arc Section at the KEKB Linac linac, acceleration, injection, single-bunch 410
  • Y. Ogawa, M. Yoshida
    KEK, Ibaraki

The KEKB linac continuously injects 8 GeV electron and 3.5 GeV positron beams into the KEKB rings: HER(high energy ring) and LER(low energy ring). The energy spread of the 8-GeV electron beam, which is accelerated to an 1.7 GeV 180-degree arc section and reaccelerated after this arc to a final energy of 8 GeV, is optimized by adjusting rf acceleration phases so as to assure efficient injections. When rf phases are slightly changed or drifted for some reasons, the beam not only shows larger energy spreads but also indicates two clusters on a beam profile monitor located at large energy dispersions. In this connection, a longitudinal beam profile was measured after the arc section with a streak-camera system utilizing an OTR(Optical Transition Radiation) bunch monitor. The observed bunch shape clearly shows a two-microbunch structure, suggesting that it could be generated in the arc section. Various experimental data as well as some CSR-related speculations are presented.

TUP012 Design and Performance of Optics for Multi-energy Injector Linac optics, injection, quadrupole, linac 413
  • Y. Ohnishi, K. Furukawa, N. Iida, T. Kamitani, M. Kikuchi, Y. Ogawa, K. Satoh, K. Yokoyama
    KEK, Ibaraki

KEK injector linac provides an injection beam for four storage rings, KEKB high energy electron ring(HER), low energy positron ring(LER), PF-AR electron ring, and PF electron ring. The injection beams for these rings have different energies and intensities. Recently, a requirement of simultaneous injection among these rings arises to make a top-up injection possible. Magnetic fields of DC magnets to confine the beam to the accelerating structures can not be changed between pulse to pulse, although the beam energy can be controlled by fast rf phase shifters of klystrons. This implies that a common magnetic field of the bending magnets and the quadrupole magnets should be utilized to deliver beams having different characteristics. Therefore, we have designed multi-energy optics for the KEKB-HER electron ring(8 GeV, 1 nC/pulse), the PF electron ring(2.5 GeV, 0.1 nC/pulse), and the KEKB-LER positron ring(3.5 GeV, 0.4 nC/pulse). We present a performance of the multi-energy injector linac.

TUP013 Present Status of the KEK Injector Upgrade for the Fast Beam-Mode Switch linac, injection, positron, target 416
  • M. Satoh
    KEK, Ibaraki

The KEK electron/ positron linac is a 600 m long linear accelerator with the maximum energy 8 GeV electron and 3.5 GeV positron, and it is used as an injector for 4-rings (KEKB e-/ e+, PF, PF-AR). To increase the operation efficiency, we have an injector upgrade plan for a simultaneous injection operation. In this paper, we will present the operation scheme and the progress of upgrade project.


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TUP014 Present Status of the BEPCII Linac linac, injection, positron, bunching 419
  • G. Pei
    IHEP Beijing, Beijing

After the major upgrade in 2005, the BEPC injector linac has been commissioning and working smoothly for more than two years. A 2.1 GeV, 66 mA positron beam at the linac end has been obtained, and the highest injection rate into the ring of 80 mA/min. at 50 pps is reached, much higher than the design goal of 50 mA/min. The machine is working stable, the mal function was about 2% in the past two years, including the system test and the commissioning.

TUP018 A 150 MeV Pulse Electron Linac with a 1 mA Average Current linac, simulation, target, emittance 428
  • V.A. Kushnir, M.I. Ayzatskiy, V.N. Boriskin, A.N. Dovbnya, I.V. Khodak, S.G. Kononenko, V.V. Mytrochenko, S.A. Perezhogin, Y.D. Tur
    NSC/KIPT, Kharkov

Funding: The present work is supported by the STCU project #P233
The accelerator driven subcritical assembly facility is under development in the National Science Center Kharkov Institute of Physics and Technology. The important component of the facility is an electron linac with energy of particles of 100-200 MeV and average beam current of 1 mA. In this paper we focus on the S-band electron linac design. The accelerator scheme includes the injector based on evanescence waves, rf chopper, five accelerating structures and energy compression system. The results of calculation of accelerating structure performances and linac systems are considered in the paper

TUP019 Injector of Intense Electron Beam simulation, bunching, cavity, emittance 431
  • V.V. Mytrochenko, M.I. Ayzatskiy
    NSC/KIPT, Kharkov

The results of beam dynamic simulation in an S-band injector that can be used for creation of the powerful electron linac are presented in the report. The injector consists of a diode electron gun with beam current of up to 2 A at energy of electrons of 25 keV, the klystron type prebuncher and the three cavity buncher. In the buncher, due to the special choice of eigen frequencies of resonators, maximal amplitude of the field on the axis of resonators exponentially increase from the first (downstream of the beam) resonator to the last resonator. It allows effective bunching the intensive electron beam and accelerating it to relativistic velocities. For providing of low transversal beam emittance the injector is placed in the external magnetic field. The injector provides more than 1 A of beam current at particle energies of about 1 MeV. Attention is paid to research of transients and stability of injector work.

TUP028 Status of High Current R&D Energy Recovery Linac at Brookhaven National Laboratory cavity, emittance, gun, SRF 453
  • A. Kayran, D. Beavis, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, A. Burrill, R. Calaga, P. Cameron, X. Chang, K.A. Drees, G. Ganetis, D.M. Gassner, J.G. Grimes, H. Hahn, L.R. Hammons, A. Hershcovitch, H.-C. Hseuh, A.K. Jain, R.F. Lambiase, D.L. Lederle, V. Litvinenko, G.J. Mahler, G.T. McIntyre, W. Meng, T.C. Nehring, B. Oerter, C. Pai, D. Pate, D. Phillips, E. Pozdeyev, T. Rao, J. Reich, T. Roser, T. Russo, Z. Segalov, A.K. Sharma, J. Smedley, K. Smith, T. Srinivasan-Rao, J.E. Tuozzolo, G. Wang, D. Weiss, N. Williams, Q. Wu, K. Yip, A. Zaltsman
    BNL, Upton, Long Island, New York
  • H. Bluem, M.D. Cole, A.J. Favale, D. Holmes, J. Rathke, T. Schultheiss, A.M.M. Todd
    AES, Medford, NY
  • J.R. Delayen, L.W. Funk, H.L. Phillips, J.P. Preble
    JLAB, Newport News, Virginia

Funding: Work performed under contract No. DE-AC02-98CH10886 with the auspices of the DoE of United States.
An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under construction at Brookhaven National Laboratory (BNL) for testing concepts for high-energy electron cooling and electron-ion colliders. One of the goals is to demonstrate an electron beam with high charge per bunch (~5 nC) and extremely low normalized emittance (~5 mm-mrad) at an energy of 20 MeV. Flexible lattice of ERL loop provides a test-bed for testing issues of transverse and longitudinal instabilities and diagnostics of intense cw e-beam. The superconducting 703 MHz rf photoinjector is considered as an electron source for such a facility. At first we develop the straight pass (gun – 5 cell cavity – beam stop) test for the SRF Gun performance studies. Then the novel injection line concept of emittance preservation at the lower energy will be tested at this ERL. In this paper we present the status and our plans for construction and commissioning of this facility.

TUP029 Electron Linac Based Coherent Radiation Light Source Project at OPU radiation, linac, synchrotron, gun 456
  • S. Okuda, T. Kojima, Y. Sakamoto, R. Taniguchi
    Osaka Prefecture University, Sakai

The coherent synchrotron and transition radiation from electron bunches of a linear accelerator (linac) has continuous spectra in a submillimeter to millimeter wavelength range at relatively high peak-intensities. This light source has been applied to absorption spectroscopy by the authors for various kinds of matters with relatively strong light absorbance such as water and aqueous solutions. The other important characteristics of the coherent radiation are picosecond pulsed light and the high peak intensity of the electric field which can be introduced into matters. In our new project the light source using the pulsed coherent synchrotron and transition radiation will be developed by using the electron beams of a 18 MeV S-band electron linac at Osaka Prefecture University (OPU). The pulse shape of the radiation has been evaluated from the shape of the electron bunch. The system of the light source has been optimized and is under construction. The light source will be applied to the pulsed excitation of matters and to the pump-probe experiment using the electron beam and the coherent radiation.

TUP033 Lattice Studies for the XFEL-Injector optics, laser, diagnostics, undulator 468
  • Y.A. Kot, V. Balandin, W. Decking, C. Gerth, N. Golubeva, T. Limberg
    DESY, Hamburg

The XFEL injector building has a length of 74.3 metres and is divided by 2.5 m long concrete shielding wall. The section upstream the shielding wall will have a length of 42.3 m and give place for the gun, accelerating module, 3rd harmonic section, laser heater and the beam diagnostics section. At its end the possibility for the beam dump is foreseen so that the tuning of the beam in the injector would become possible without any impact on the subsequent parts of the XFEL. Each of these components sets certain requirements on beam optics which may compete with each other. Downstream the shielding the beam will be vertically displaced by 2.75 m over the distance of 20 m by means of the so called dogleg - a combination of two four cell arcs (8 cell system). Since the vertical displacement takes place there it is important to optimize cells in such an order that the chromatic effects don't impact the beam quality noticeably. In this paper we describe the solution for the beam optics at the XFEL injector.

TUP034 Status of the 3rd Harmonic Systems for FLASH and XFEL in Summer 2008 cavity, klystron, linac, controls 471
  • E. Vogel, W. Decking, M. Dohlus, M.G. Hoffmann, M. Hüning, J. Iversen, K. Jensch, G. Kreps, T. Limberg, A. Matheisen, W.-D. Möller, K. Rehlich, A. Schmidt, J.K. Sekutowicz, W. Singer
    DESY, Hamburg
  • A. Bosotti, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI)
  • H.T. Edwards, E.R. Harms, T.N. Khabiboulline
    Fermilab, Batavia

Ultra short bunches with high peak current are required for the creation of high brilliance coherent light in the VUV and X-ray range in undulators. At the Free Electron Laser in Hamburg (FLASH) and the European X-ray free electron laser (XFEL) they are obtained by a two stage bunch compression scheme based on acceleration off the rf field crest and transverse magnetic chicanes. The deviation of the rf field's sine shape from a straight line leads to long bunch tails and reduces the peak current. This effect can be eliminated by adding a third harmonic rf system. The paper gives an overview on the actual status of the beam dynamical examinations and as well on the development of the third harmonic sub-systems like modules, cavities and radio frequency systems for FLASH and the XFEL.

TUP038 MIR-FEL with 4.5-Cell Thermionic RF-Gun FEL, gun, undulator, klystron 477
  • T. Kii, K. Higashimura, R. Kinjo, K. Masuda, H. Ohgaki, H. Zen
    Kyoto IAE, Kyoto

An MIR-FEL facility, Kyoto University FEL (KU-FEL), has been developed for applications in "sustainable energy science", such as fundamental studies on high-efficiency solar cells. The KU-FEL, consisting of an S-band thermionic rf gun, a 3 m accelerator tube and a planer undulator, aims to generate 4-13 μmeter tunable FEL. The first lasing was achieved on March, 2008 at 12.4 μmeters by using a beamloading compensation method both in the rf gun and in the accelerator tube. *Furthermore, we introduced detuning to the rf gun and succeeded to generate an electron beam with macropulse duration of 5.1 μseconds, average current of 100 mA and energy spread of 0.5% which led to power saturation in FEL. In the conference, the improvements of the electron beam properties and power saturation of the KU-FEL will be discussed.

*H. Ohgaki et al., 'First Lasing at 12 um Mid Infrared Free Electron Laser at Kyoto University', Japanese Journal of Applied Physics, accepted for publication. (2008).

TUP039 Status of the LINAC-800 Construction at JINR linac, acceleration, gun, FEL 480
  • G.V. Trubnikov, N. Balalykin, A.G. Kobets, V. Kobets, I.N. Meshkov, V. Minashkin, G. Shirkov, G.I. Sidorov
    JINR, Dubna, Moscow Region
  • V. Shabratov
    JINR/LHE, Moscow

800 MeV electron linac (LINAC-800) is under construction at JINR. It will be used as a driver for Volume FEL and as a test bench for commissioning of elements of the ILC. Presently the electron injector is commissioned and the electron beam of 50 keV of the energy at current of about 15 mA was obtained. The results of the injector operation at nominal parameters (400 keV, 300 mA) and commissioning of the first accelerating section at 20 MeV are discussed.

TUP043 Development of a Beam Loss Monitor System for the LCLS Undulator Beamline undulator, beam-losses, simulation, radiation 492
  • W. Berg, J.C. Dooling, A.F. Pietryla, B.X. Yang
    ANL, Argonne
  • H.-D. Nuhn
    SLAC, Menlo Park, California

Funding: Work Argonne supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357.
A Beam-Loss Monitor (BLM) system based on the detection of Cerenkov radiation is in development at the Advanced Photon Source (APS) for the Linac Coherent Light Source (LCLS) free-electron laser. The electron beam will vary in energy nominally from 4 to 14 GeV with a beam charge of 0.2 to 1.0 nC and a maximum repetition rate of 120 Hz. To limit radiation-induced demagnetization of the undulator permanent magnets, the BLM will provide beam-loss threshold detection as part of the Machine Protection System (MPS). The detector incorporates a large volume (30 cc) fused silica Cerenkov radiator coupled to a photomultiplier tube (PMT). The output of the PMT is conditioned locally by a charge amplifier circuit and then digitized at the front end of the MPS rack electronics. During commissioning, the device will be calibrated by inserting a 1-micron aluminum foil into the beam, upstream of the undulator magnets. The present design calls for five BLM detector units to be distributed throughout the 33 undulator magnets. Beam-based testing is to begin at the APS storage ring during the summer of 2008. Details and status of the detector hardware, electronics, and simulations will be discussed.

TUP045 Generation of Femtosecond Bunch Trains Using a Longitudinal-to-Transverse Phase Space Exchange Technique emittance, dipole, simulation, cavity 498
  • Y.-E. Sun, P. Piot
    Fermilab, Batavia

Funding: Work supported by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. DOE and by Northern Illinois University under Contract No. DE-FG02-08ER41532 with the U.S. DOE
We demonstrate analytically and via numerical simulation, how a longitudinal-to-transverse phase space manipulation* can be used to produce a train of femtosecond electron bunches. The technique uses an incoming transversely-modulated electron beam obtained via destructive (e.g. using a multislits mask) or non destructive (e.g. transversely shaping the photocathode drive laser) methods. A transverse-to-longitudinal exchanger insertion is used to map this transverse modulation into a temporal modulation. Limitation of the proposed method and scalability to the femtosecond regime are analysed analytically and with the help of numerical simulation. Application of the method to generation of super-radiant far infrared (and shorter wavelength) radiation in an FEL is explored. Finally, a proof-of-principle experiment is discussed in the context of the Fermilab's A0 photoinjector.

*P. Emma, Z. Huang, K.-J. Kim, and P. Piot, Phys. Rev. ST Accel. Beams 9, 100702 (2006).

TUP046 Linac Design for an Array of Soft X-Ray Free Electron Lasers linac, FEL, emittance, lattice 501
  • A. Zholents, G. Penn, J. Qiang, M. Venturini, R.P. Wells
    LBNL, Berkeley, California
  • E. Kur
    UCB, Berkeley, California

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The design of the linac delivering the electron bunches into ten independent soft x-ray free electron lasers (FELs) is presented. The bunch repetition rate in the linac is 1 MHz and the bunch repetition rate in each FEL beam line is 100 kHz. Various issues regarding machine layout and lattice, bunch compression, collimation, and the beam switch yard are discussed. Particular attention is given to collective effects. A demanding goal is to preserve both a low beam slice emittance and low slice energy spread during acceleration, bunch compression and distribution of the electron bunches into the array of FEL beamlines. Detailed studies of the effect of the electron beam microbunching resulting from longitudinal space-charge forces and coherent synchrotron radiation as the beam undergoes compression have been carried out and are presented.

TUP047 Manipulating the Two-Stream Instability for Efficient Terahertz Generation bunching, radiation, coupling, simulation 504
  • K. Bishofberger, B.E. Carlsten, R. Faehl
    LANL, Los Alamos, New Mexico

Particle beams have exhibited a two-stream instability for many decades; this undesirable trait has been well-understood for many years. We propose creating a scheme that uses a beam of electrons with two distinct energies that will develop the two-stream instability as a bunching mechanism. By controlling the beam parameters and seeding them with a low-level rf signal, a gain as high as 2.5 dB per centimeter is predicted. We show the theory behind this concept and recent progress in a developing experiment.

TUP049 The Electron Bunch Initial Energy Profile on a Seeded Free Electron Laser Performance FEL, undulator, free-electron-laser, laser 509
  • J. Wu, A. Chao
    SLAC, Menlo Park, California
  • J. Bisognano
    UW-Madison/SRC, Madison, Wisconsin

Funding: The work of AWC and JW was supported by the US Department of Energy under contract DE-AC02-76SF00515. The work of JB was supported by National Science Foundation Award No. DMR-0537588.
A single-pass high-gain X-ray free electron laser (FEL) calls for a high quality electron bunch. In particular, for a seeded FEL, and for a cascaded harmonic generation (HG) FEL, the electron bunch initial energy profile uniformity is crucial to preserve an FEL narrow bandwidth. After the acceleration, compression, and transport, the electron bunch energy profile entering the undulator can acquire temporal non-uniformity. During the cascading stages, the electron bunch energy profile is also not uniform temporally entering the next stage. We study the effects of the electron bunch initial energy profile on the FEL performance, cascaded HG FEL or single stage FEL amplifier. Concrete examples are discussed for seeded FEL projects being studied.

TUP050 Design and Optimization of Electron Bunch Acceleration and Compression wakefield, linac, acceleration, cavity 512
  • J. Wu, P. Emma
    SLAC, Menlo Park, California
  • R.A. Bosch, K.J. Kleman
    UW-Madison/SRC, Madison, Wisconsin

Funding: The work of PE and JW was supported by the US Department of Energy under contract DE-AC02-76SF00515. The work of RAB and KJK was supported by National Science Foundation Award No. DMR-0537588.
For electron bunches driving a hard X-ray free electron laser, the electron bunch high qualities should be preserved as well as possible in the acceleration and compression. For typical configuration, the electron bunch is accelerated in rf cavity and compressed in magnetic chicane. Besides the rf curvature and high-order optics terms in a chicane, the collective effects during the bunch acceleration, transportation, and compression can further distort the phase space and even lead to instability. Among these collective effects, the coherent edge radiation dominates and governs the overall bunch property; while the longitudinal space charge is the main cause for microbunching instability. Random jitter couples to the wakefields and affect the final bunch properties. We study these effects and discuss their implication to general linac design and optimization.

TUP051 Design of Microwave Undulator Cavity undulator, cavity, radiation, synchrotron 515
  • M. Yeddulla, S.G. Tantawi
    SLAC, Menlo Park, California

Static magnetic field undulators are capable of producing quasi-monochromatic synchrotron radiation of very high brightness. However, it is not possible to quickly change the properties such as polarization of the radiation in a static undulator. It is possible to construct an undulator using microwaves instead of static magnets where the electron beam is undulated by both electric and magnetic fields of an rf wave. A major advantage with a microwave undulator is that the radiation properties can be changed very quickly. The biggest challenge in developing a microwave undulator is in keeping the rf losses low. We are designing a microwave undulator with the aim of achieving at least a tenth of the flux obtained by the BL13 static magnetic field Elliptical Polarized Undulator in the SPEAR ring. We have considered circular waveguide modes and hybrid HE11 mode in a corrugated waveguide as possible candidates for the microwave undulator. It is found that a corrugated waveguide has the lowest rf losses with a very desirable field profile. It is also possible to use this device for a linac driven FEL. Our analysis of the corrugated waveguide cavity for the rf undulator will be presented.


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TUP052 Status of the NPS Free-Electron Laser FEL, booster, undulator, laser 518
  • J.W. Lewellen, W.B. Colson, S.P. Niles
    NPS, Monterey, California
  • T.I. Smith
    Stanford University, Stanford, Califormia

Funding: This research is supported by the Office of Naval Research and the Joint Technology Office.
The Naval Postgraduate School (NPS) has begun the design and assembly of the NPS Free-Electron Laser (NPS-FEL). The basic NPS-FEL design parameters are for 40 MeV beam energy, 1 nC bunch charge, and 1 mA average beam current, in an energy-recovery linac configuration. The NPS-FEL will make use of portions of the Stanford Superconducting Accelerator (decommissioned in 2007), in particular the injector system, Stanford/Rossendorf-style cryomodules and rf system. The injector will be gradually upgraded to improve beam properties and increase the injection voltage. Each cryomodule contains two, 9-cell TESLA-type 1.3 GHz cavities, each cavity powered by an individual 10 kW cw klystron. NPS has committed to refurbishing a building for the FEL, with approximate interior vault dimensions of 7 m x 20 m x 2.5 m. The building has overall dimensions of 12 m x 49 m and will house the vault, control room, and support equipment. This paper describes the overall goals of the program, initial experimental plans, and progress to date.

TUP053 Experimental Characterization and Optimization of High-brightness Electron Beam at the NSLS SDL emittance, laser, injection, solenoid 521
  • X. Yang, J.B. Murphy, H.J. Qian, S. Seletskiy, Y. Shen, X.J. Wang
    BNL, Upton, Long Island, New York

The Source Development Laboratory (SDL) at the National Synchrotron Light Source (NSLS) is a laser linac facility dedicated for laser seeded FEL and beam physics R&D. The SDL consists of a RF synchronized Ti:sapphire laser, a BNL photocathode RF gun, a four-magnet chicane bunch compressor, and a 300 MeV linac. To further improve the performance of the laser seeded FEL at the NSLS SDL, we have carried out a systematic experimental characterization of the high-brightness electron beam generated by the photocathode RF gun. We will present the experimental studies of both transverse and longitudinal emittance of electron beam as a function of RF gun phase and solenoid magnet for electron beam charge ranging from 350 pC to 1 nC and their influences on FEL output.

TUP063 Development of a New Highly Bright X-ray Generator brightness, radiation, target, synchrotron 539
  • S. Ohsawa, M. Ikeda, N. Sakabe, T. Sugimura
    KEK, Ibaraki

A new type of rotating anticathode X-ray generator has been developed, in which the electron beam irradiates the inner surface of a U-shaped anticathode. A high-flux electron beam is focused on the inner surface by optimizing the shape of the bending magnet. In order to minimize the sizes of the X-ray source, the electron beam is focused strongly in a short distance by the bending magnet which is small and is close to the rotating anticathode. The power of the electron beam can be increased to the point at which the irradiated part of the inner surface is melted, because a strong centrifugal force fixes the melted part on the inner surface. We have achieved emission of X-rays 10 times more brilliant than can be attained by a conventional rotating anticathode. The development is still in progress. New results will be reported in detail.

TUP064 Nuclear Reaction Analysis by Using Quasi-Elastic Scattering of Ultra Low Intensity Electron Beams neutron, target, radiation, scattering 542
  • R. Taniguchi, T. Kojima, S. Okuda, R. Sasaki
    Osaka Prefecture University, Sakai

Energetic electron beams higher than several MeV occasionally induce direct nuclear reactions with the target nuclei. These processes are attributed to the quasi-elastic scattering of electrons (e,e') with the target nuclei and similar to the photo-nuclear reactions. These reactions are considered to be useful for the non-destructive analysis of heavy elements such as U and Th. In addition, a two-dimensional analysis is realized only by scanning of electron beam. On the other hand, the huge X-ray burst caused by the bremsstrahlung with the electron pulse bombardment is the most harmful phenomenon for the radiation measurement system. In this study, an ultra low intensity electron beam was used for relieving the problem, which has been developed by modifying an electron linear accelerator. The minimum beam charge about several aC/pulse has been achieved at the present. Consequently, the neutron emitted by Pb(e,e'n)Pb reaction was measured successfully by the use of the low intensity beams. The linearity between the neutron count and the concentration of Pb in the target was verified experimentally.

TUP065 Demonstration of Multi-Pulse X-ray Generation via Laser-Compton Scattering Using Pulsed-Laser Super-Cavity laser, cavity, photon, linac 545
  • K. Sakaue, M. Washio
    RISE, Tokyo
  • S. Araki, M.K. Fukuda, Y. Higashi, Y. Honda, T. Taniguchi, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • N. Sasao
    Kyoto University, Kyoto

Funding: Work supported by a Grant-In-Aid for Creative Scientific Research of JSPS (KAKENHI 17GS0210) and a Grant-In-Aid for JSPS Fellows (19-5789)
A compact and high quality X-ray source is required for various field, such as medical diagnosis, drug manifacturing and biological sciences. Laser-Compton based X-ray source that consist of a compact electron storage ring and a pulsed-laser super-cavity is one of the solutions of a compact X-ray source. Pulsed-laser super-cavity has been developed at Waseda University for a compact high brightness X-ray source. The pulsed-laser super-cavity enables to make high peak power and small waist laser at the collision point with the electron beam. 357 MHz mode-locked Nd:VAN laser pulses can be stacked stably in a 420 mm long Fabry-Perot cavity with "burst mode", which means stacking of electron beam synchronized amplified pulses in our R&D. In view of this successful result, we have started an X-ray generation experiment using a super-cavity and a multi-bunch electron beam at KEK-LUCX. Recently, the demonstration experiment between the burst mode pulsed-laser super-cavity and the 100bunch multi-bunch electron beam is successfully performed. Development of the super-cavity and the experimental results of X-ray generation will be presented at the conference.

TUP066 Commissioning of 10-MeV L-band Electron Linac for Industrial Applications klystron, linac, gun, high-voltage 548
  • S.H. Kim, M.-H. Cho, W. Namkung, H.R. Yang
    POSTECH, Pohang, Kyungbuk
  • S.D. Jang, S.J. Park, Y.G. Son
    PAL, Pohang, Kyungbuk
  • J.-S. Oh
    NFRI, Daejon

Funding: This work is supported by KAPRA and POSTECH Physics BK21 Program.
An intense L-band electron linear accelerator is now being commissioned at CESC (Cheorwon Electron-beam Service Center) for industrial applications. It is capable of producing 10 MeV electron beams with 30 kW average beam power. For a high-power capability, we adopted the traveling-wave structure operated with the 2π/3 mode at 1.3 GHz. The structure is powered by a 25 MW pulsed klystron with 60 kW average rf power. The rf pulse length is 7 μs while the beam pulse length is 6 μs due to the filling time in the accelerating structure. The accelerating gradient is 4.2 MV/m at the beam current of 1.45 A which is the fully beam-loaded condition. In this paper, we present details of the accelerator system and commissioning results.

TUP068 Project of a Neutron Source Based on the Sub-Critical Assembly Driven by Electron Linear Accelerator neutron, target, octupole, shielding 551
  • I.M. Karnaukhov, V. Azhazha, A.N. Dovbnya, A.S. Kostromin, V.E. Krasnorutzkiy, I.M. Neklyudov, S.A. Perezhogin, S. Soldatov, A.Y. Zelinsky
    NSC/KIPT, Kharkov
  • I. Bolshinsky
    Idaho National Laboratory, Idaho
  • M.Y.A. Gohar
    ANL, Argonne

Today accelerator driven subcritical assembly is candidate for the next generation of energy-generating nuclear facility, which could provide safe energy production, burning of transuranium elements and transmutation of radionuclides. Use of the electron beam with particle energy up to 150-200 MeV secures several advantages. Electron linear accelerators are much cheaper compared to hadron accelerators. Homogeneous irradiation of the assembly with neutrons could be provided. NSC KIPT together with ANL develops the project of a neutron source based on the sub-critical assembly driven by electron linear accelerator. Energy of electrons is 100-200 MeV. The target and assembly design is optimized to maximize the neutron source intensity with subcriticality of 0.98. Accelerator on average beam power of 100 kW, with repetition rate up to 300 Hz and pulse duration of 3,2 ms is under development. Transportation line should provide beam transfer with minimal losses of electrons and should form homogeneous distribution of the particle density at the target. Maximal value of a neutron flux is Fm=2x1013 n/(cm2s), and power of energy release in the result of nuclei fission is Pm≈ 100 kW.

TUP069 Low Energy Photoemission Electron Source for Applications in THz Radiation Production and Time-Resolved Electron Microscopy laser, cathode, radiation, FEL 554
  • N. Vinogradov, P. Piot, C.R. Prokop
    Northern Illinois University, DeKalb, Illinois
  • J.W. Lewellen, J. Noonan
    ANL, Argonne

Funding: Work supported by the Department of Education under contract P116Z010035 with Northern Illinois University.
A simple, inexpensive, and compact low-energy (~20 KeV) photoemission electron source was designed, built and recently commissioned. It uses a commercial ultraviolet photocathode drive laser producing 3 ns RMS pulse. The source will eventually be used to drive a table-top THz radiation source, based on the Smith-Purcell free-electron laser scheme, and could also have potential application to time-resolved electron microcopy. We present experimental measurements of the photoemitted electron beam and numerical simulations of the anticipated parameters. We also discuss the generation of flat beams required to efficiently drive the THz radiation source.

TUP072 AIRIX Diagnostic Devices for Focal Spot Size and Dose Measurements target, diagnostics 560
  • O. Pierret
    CEA, Pontfaverger-Moronvilliers

Funding: CEA-DAM, Polygone d'Experimentation de Moronvilliers 51 490 Pontfaverger Moronvilliers (France). olivier.pierret@cea.fr
AIRIX is a 2 kA, 19 MeV, 60 ns, single shot linear accelerator that produces X-rays from the interaction between relativistic electrons and a Tantalum solid target (Ta). Focal spot size, integrated and temporal dose are the main characteristics that we need for the successful development of flash radiography at hydro test facilities. MTFX is a 12 bit Charge-Coupled Device (CCD) intensified camera which is equipped with a scintillator. It can give focal spot size measurements in two directions using a two dimensional wedge. By another way Mucaddix is a CVD Diamond detector which is integrated nearby the AIRIX X-ray beam source. It gives integrated dose, time resolve dose, temporal characteristics of the X-ray flash and timing of the flash respect to the start of object implosion. These two measurement systems are described and the quantified results are reviewed here.

TUP073 Tailoring the Emittance of a Charged Particle Beam with a Tunnel Emittance Meter emittance, ion, brilliance, ion-source 561
  • R. Becker
    IAP, Frankfurt am Main

Based on the 'tunnel' emittance used for electron focusing, a similar procedure with two pairs of slits with variable widths is proposed to evaluate fractional emittances and brilliances for ion beams. The measurement starts with closing both slits (one after the other), until a certain fraction of the beam current is cut out. The emittance and brilliance then is well defined for the passing beam part. Formulae are given for the emittance as well as for the brilliance in dependence of the slit width and current. This emittance measurement is free from the background subtraction problem found in the classical density measurement of phase space(s). The functions for the decrease of the emittance and for the increase of the brilliance in dependence of the transmitted beam current provide a figure of merit for the quality of the investigated beam. The device at the same time is also an adjustable emittance filter for the passing beam. At the expense of current the emittance and/or brilliance of a beam can be tailored to any value, which is available by the beam quality.

TUP074 Commissioning of the HITRAP Decelerator Using a Single-Shot Pepper Pot Emittance Meter emittance, ion, rfq, linac 564
  • J. Pfister, R. Nörenberg, U. Ratzinger
    IAP, Frankfurt am Main
  • W. Barth, L.A. Dahl, P. Forck, F. Herfurth, O.K. Kester, T. Stöhlker
    GSI, Darmstadt

Funding: Work supported by BMBF under contract 06FY160I.
The Heavy highly charged Ion TRAP (HITRAP) project at GSI is in the commissioning phase. Highly charged ions up to U92+ provided by the GSI accelerator facility will be decelerated and subsequently injected into a large Penning trap for cooling to the MeV/u energy level. A combination of an IH- and an RFQ-structure decelerates the ions from 4 MeV/u down to 6 keV/u. In front of the decelerator a double drift-buncher-system is provided for phase focusing and a final de-buncher integrated in the RFQ-tank reduces the energy spread in order to improve the efficiency for beam capture in the cooler trap*. This contribution concentrates on the beam dynamics simulations and corresponding measurements in the commissioning beam times up to the position of the entrance to the RFQ. Single-shot emittance measurements at higher energies using the GSI pepper pot device and construction of a new device using Micro-Channel Plate technology for low energies as well as profile measurements are presented.

*HITRAP webpage of AP division at GSI, http://www.gsi.de/forschung/ap/projects/hitrap/index_e.html

TUP075 DITANET: A European Initiative in the Development of Beam Instrumentation for Future Particle Accelerators diagnostics, ion, instrumentation, optics 567
  • C.P. Welsch
    KIP, Heidelberg
  • C.P. Welsch
    MPI-K, Heidelberg

Without an adequate set of beam instrumentation, it would not be possible to operate any particle accelerator, let aside optimize its performance. In a joint effort between several major research centres, Universities, and partners from industry, DITANET aims for the development of beyond-state-of-the-art diagnostic techniques for future accelerator facilities and for training the next-generation of young scientists in this truly multi-disciplinary field. The wide research program covers the development of beam profile, current, and position measurements, as well as of particle detection techniques and related electronics. This contribution introduces this new Marie Curie Initial Training Network, presents the DITANET partner institutes, and gives an overview of the networks broad research and training program.

TUP077 Development of Screen Monitor with a Spatial Resolution of Ten Micro-meters for XFEL/SPring-8 target, vacuum, focusing, undulator 573
  • K. Yanagida, H. Tomizawa, A. Yamashita
    JASRI/SPring-8, Hyogo-ken
  • S.I. Inoue, Y. Otake
    RIKEN/SPring-8, Hyogo

At SPring-8, the 8 GeV linac for an X-ray free electron laser (XFEL) is now under construction. In order to realize the XFEL, highly qualified electron beams are required. A measurement of spatial structure of such beam is very important for the beam tuning of XFEL. The spatial structure is measured with a screen monitor, which we now develop. The resolution of the measurement is required within 10 um. The screen monitor comprises a vacuum chamber with a thin metal (100 um, SUS) foil to emit OTR, lenses for focusing and a CCD camera system. The main feature of the monitor is a bright and high-resolution optical system. In order to realize this system, the lenses are placed close to the foil, the distance between the lenses and the foil is 100 mm, and the lenses have a large diameter (2 in.). This optical-geometrical structure also contributes much to reduce the airy radius of a near field image. Although the range of an observation wavelength is wide as which is form 400 to 800 nm, the resolution of the measurement on the foil is calculated as 2.5 um. The experimental data of the developed screen monitor also suggested the same resolution.

TUP078 Development of Integrator Circuit for Charge Monitoring controls, linac, injection, storage-ring 576
  • K. Yanagida, H. Hanaki, S. Suzuki
    JASRI/SPring-8, Hyogo-ken

At the SPring-8 1 GeV linac, a beam current or charge is measured by means of an integrator circuit. A signal from a current transformer is processed into an integrated voltage. The Fast Gated Integrator and Boxcar Averager Module (Stanford Research Systems) is presently used as the integrator. However we plan to expand a dynamic range and an integration time of the integrator. Because the noise level of the present integrator becomes too large for the expansion, we developed a low-noise and high-resolution integrator. Both the present and developed integrators have the same functions such as signal gating, accumulation of analog signal and sample hold. The principal noise of the integrator was found to be a switching noise of the gate switch. To reduce the switching noise a GaAs transfer switch SW-283-PIN (M/A-COM) was adopted as the gate switch. The experimental data of the developed integrator showed 1/10 of the noise level of the present integrator.

TUP080 Numerical Study of a New Bunch Length Monitor Utilizing a Detection of Electromagnetic Fields in Millimeter-Wave Region radiation, vacuum, linac, dipole 582
  • T. Suwada, M. Satoh
    KEK, Ibaraki

A new nondestructive bunch-length monitor has been numerically investigated. The monitor detects electromagnetic fields generated through a ceramic gap of a vacuum pipe when a charged particle beam passes through the pipe gap. The frequency spectrum of the electromagnetic fields detected in wave zone spreads over a millimeter-wave length from a microwave length region for a short pulse beam with a bunch length of pico-second region. The frequency spectrum strongly depends on the bunch length of the relativistic charged beam if the geometrical structure of the pipe gap is fixed. The detection principle of the bunch-length monitor and some numerical analysis results applied to a single-bunch electron beam of the KEKB injector linac are described in this report.

TUP081 Transient Beam Loading Compensation in CTF3 linac, beam-loading, cavity, radiation 585
  • A.E. Dabrowski, S. Bettoni, H.-H. Braun, E. Bravin, R. Corsini, S. Döbert, C. Dutriat, T. Lefèvre, M. Olvegård, P.K. Skowronski, F. Tecker
    CERN, Geneva

In the CLIC Test Facility 3 (CTF3), the strong coupling between the beam and the accelerating cavities (full beam loading) induces transient effects such that the head of the pulse is accelerated almost twice as much as the steady-state part of the pulse. The beam optics in the machine is tailored for the steady-state and not for the higher energy electrons, which are gradually lost. This can lead to inefficiency and contributes to the activation of the machine. A beam loading compensation scheme has been proposed to minimize this effect. By delaying appropriately the arrival time of rf pulse in accelerating cavities with respect to the beam, the transient energy can be brought close (to within a few percent) of the steady-state one. This paper presents the measurements done on CTF3 using time resolved energy measurements.

TUP082 Bunch Length Measurements in CTF3 pick-up, klystron, radiation, linac 588
  • A.E. Dabrowski, S. Bettoni, H.-H. Braun, R. Corsini, S. Döbert, T. Lefèvre, H. Shaker, P.K. Skowronski, F. Tecker
    CERN, Geneva
  • J.J. Jacobson, M. Velasco
    NU, Evanston

The CLIC Test Facility CTF3, being built at CERN by an international collaboration, should demonstrate the feasibility of the CLIC two-beam technology by 2010. One of the issues addressed is the control of the electron bunch length in the whole complex. A bunch length measurement system with good resolution is therefore paramount. Two different systems are presently used in CTF3, based on microwave spectroscopy and on transverse rf deflectors, respectively. In the paper we describe the two systems, we discuss the different experimental methods used and present the results of the latest measurement campaigns.

TUP086 Initial Commissioning of a Dual-Sweep Streak Camera on the A0 Photoinjector laser, emittance, cavity, optics 600
  • A.H. Lumpkin, T.W. Koeth, J. Ruan
    Fermilab, Batavia

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Characterization of the micropulse bunch lengths and phase stability of the drive laser and the electron beam continue to be of interest at the Fermilab A0 Photoinjector facility. Upgrades to the existing Hamamatsu C5680 streak camera were identified, and initially a synchroscan unit tuned to 81.25 MHz was installed to provide a method for synchronous summing of the micropulses from the drive laser and the optical transition radiation (OTR) generated by the e-beam. A phase-locked delay box was also added to the system to provide phase stability of ~1 ps over tens of minutes. Initial e-beam measurements identified a significant space-charge effect on the bunch length. Recent measurements with a re-optimized transverse emittance allowed the reduction of the micropulse number from 50 to 10 with 1 nC each to obtain a useful streak image. This increased signal also would facilitate dual-sweep operations of the streak camera to explore macropulse effects. Installation of the recently procured dual-sweep module in the mainframe has now been done. Initial commissioning results and sub-macropulse effects in the beams will be presented as available.

TUP089 Electron Beam Timing Jitter and Energy Modulation Measurements at the JLab ERL FEL, wiggler, instrumentation, cavity 606
  • P. Evtushenko, S.V. Benson, D. Douglas, D.W. Sexton
    JLAB, Newport News, Virginia

When operating JLab high current ERL a strong reduction of the FEL efficiency was observed when increasing the average electron beam current. Investigating the FEL efficiency drop-off with the electron beam average current we also have measured the electron beam phase noise and the fast energy modulations. The so-called phase noise is essentially a variation of the time arrival of the electron bunches to the wiggler. That could be a very effective way of reducing the FEL efficiency if one takes in to account that the accelerator is routinely operated with the RMS bunch length of about 150 fs. Under a fast energy modulation we mean a modulation which can not be followed by the FEL due to its time constant, defined by the net gain. Such a modulation also could be a possible cause of the efficiency drop-off. Having the measurements made we could rule out the FEL efficiency drop-off due to either the fast energy modulation or the phase modulation. We also have learned a lot about instrumentation and techniques necessary for this kind of beam study. In this contribution we describe the used instrumentation and present results of the measurements.

TUP090 Optical Diffraction Radiation Measurements at CEBAF radiation, background, diagnostics, beam-losses 609
  • P. Evtushenko, A. Freyberger
    JLAB, Newport News, Virginia
  • C. Liu
    CASA, newport news
  • A.H. Lumpkin
    Fermilab, Batavia

Optical diffraction radiation (ODR) is a promising technique, which could be used for non interceptive beam size measurements at future light sources. An ODR diagnostic station was designed and installed on a CEBAF transfer beam line. The purpose of the setup is to evaluate experimentally the applicability range for an ODR based non interceptive beam size monitor and to collect data to benchmark numerical modeling of the ODR. An extensive set of measurements were made at the electron beam energy of 4.5 GeV. The ODR measurements were made for both pulsed and CW electron beam of up to 80 uA. The wavelength dependence and polarization components of the ODR were studied using a set of insertable bandpass filters and polarizers. The typical transverse beam size during the measurements was ~150 microns. Complete ODR data, wavelength and polarization, were recorded for different beam sizes and intensities. The beam size was also measured with an optical transition radiation (OTR) as well as wire scanner located next to the ODR station. In this contribution we describe the experimental setup and present first results of the measurements with the comparison to the numerical simulations.

TUP092 Laser-Based Profile and Energy Monitor for H- Beams laser, space-charge, ion, linac 615
  • R. Connolly, J.G. Alessi, S. Bellavia, W.C. Dawson, C. Degen, W. Meng, D. Raparia, T. Russo, N. Tsoupas
    BNL, Upton, Long Island, New York

A beam profile and energy monitor for H- beams based on laser photoneutralization is being developed at Brookhaven National Laboratory for use on the High Intensity Neutrino Source at Fermilab. An H- ion has a first ionization potential of 0.75 eV and can be neutralized by light from a Nd:YAG laser (λ = 1064 nm). To measure beam profiles, a narrow laser beam is stepped across the ion beam removing electrons from the portion of the H- beam intercepted by the laser. A curved axial magnet field channels these electrons into a Faraday cup. To measure the energy spread of the electrons the laser position is fixed and the voltage on a screen in front of the cup is raised in small steps. We deduce the energy spread of the H- beam by deconvolving the electron spectrum into components from beam energy and from space-charge fields. Measurements are reported from experiments in the BNL linac MEBT at 750 keV.


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TUP094 Development of a Photocathode RF Gun for an L-Band Electron Linac cavity, gun, cathode, emittance 621
  • G. Isoyama, S. Kashiwagi, R. Kato
    ISIR, Osaka
  • H. Hayano, T. Muto, J. Urakawa
    KEK, Ibaraki
  • M. Kuriki
    HU/AdSM, Higashi-Hiroshima

Funding: This research is partly supported by the accelerator support program to universities conducted by the High Energy Accelerator Research Organization in Japan.
We have begun a three-year project to develop a photocathode rf electron gun for the 40 MeV L-band linac at ISIR, Osaka University in collaboration with KEK. The L-band linac with an rf frequency of 1.3 GHz is equipped with a thermionic electron gun and it can accelerate a high-intensity single-bunch electron beam with charge up to 91 nC/bunch. Because the large emittance of ~100 pi mm x mrad is a limiting factor in the experiments, it is required to develop a new electron gun capable of providing an electron beam with much lower emittance. Since a group at the Accelerator Laboratory of KEK is developing a photocathode rf electron gun in the L-band for the International Linear Collider Project, we have joined the group to learn how to develop such an rf gun and also to obtain support from KEK. In this first year, characteristics of the rf gun will be measured at KEK for ILC fabricated by FNAL. We plan to optimize the structure of the rf gun for ISIR with computer simulation. We will report the plan and progress to develop a photocathode rf gun for the L-band linac.

TUP095 Development of a Cs-Te Cathode RF Gun at Waseda University cavity, gun, cathode, resonance 624
  • Y. Kato, A. Fujita, Y. Hama, T. Hirose, C. Igarashi, A. Masuda, A. Murata, T. Nomoto, K. Sakaue, T. Suzuki, M. Washio
    RISE, Tokyo
  • H. Hayano, T. Takatomi, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • Y. Kamiya
    University of Tokyo, Tokyo
  • S. Kashiwagi
    ISIR, Osaka
  • M. Kuriki
    HU/AdSM, Higashi-Hiroshima
  • R. Kuroda
    AIST, Tsukuba, Ibaraki

Funding: Work supported by MEXT High Tech Research Project HRC707, JSPS Grant-in-Aid for Scientific Research (B)(2) 16340079
At Waseda University, we have been developing a high quality electron source based on photo-cathode rf gun which has a Cs-Te cathode with high quantum efficiency. Until now, at the Waseda University we have succeeded the soft X-ray generation via inverse-Compton scattering and pulse radiolysis system for studying the early processes of radiation chemistry with electron beams generated by copper cathode rf gun. Cs-Te rf gun is expected to generate higher charge electron bunches with a low emittance than a copper cathode because of its high quantum efficiency and also the high-quality multi-bunch electron beams. That enables us to extend the range of electron beam parameters for our application experiments. However, a Cs-Te cathode has a short life compared with a copper, so it has to be exchanged occasionally, thus we have developed a new rf-gun cavity which can be attached the compact cathode load-lock system. Moreover, we improved the design of an existing rf-gun cavity for the reduction of the dark current and the higher electric field. In this conference, the performance of the improved cavity and the result of electron beam generation experiments will be reported.

TUP097 Measurements and Modeling at the PSI-XFEL 500 kV Low-Emittance Electron Source emittance, cathode, simulation, laser 630
  • T. Schietinger, A. Adelmann, Å. Andersson, M. Dietl, R. Ganter, C. Gough, C.P. Hauri, R. Ischebeck, S. Ivkovic, Y. Kim, F. Le Pimpec, S.C. Leemann, K.B. Li, P. Ming, A. Oppelt, M. Paraliev, M. Pedrozzi, V. Schlott, B. Steffen, A.F. Wrulich
    PSI, Villigen

Paul Scherrer Institute (PSI) is presently developing a low emittance electron source for the PSI-XFEL project. The electron gun consists of an adjustable diode configuration subject to pulses of 250 ns (FWHM) with amplitude up to 500 kV from an air-core transformer- based high-voltage pulser. The facility allows high gradient tests with different cathode configurations and emission processes (field emission and photo emission). In the first stage, the beamline is only made up of focussing solenoids followed by an emittance monitor. Selected beam characterization measurements, from photo-cathode operation driven by a 266 nm UV laser system delivering 4 uJ energy during 6.5 ps (FWHM), are presented and compared to the results of 3D particle tracking simulations.


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TUP098 Lienard-Wiechert Potentials and Method of Images in RF Free Electron Laser Photoinjector cathode, acceleration, cavity, electromagnetic-fields 633
  • R.M. Jones
    UMAN, Manchester
  • W. Salah
    The Hashemite University, Zarka

Based on Lienard-Weichert method of retarded potentials and the potential due to the image of charges on the cathode, a rigorous relativistic description of the beam transport inside the rf-photoinjector is presented. The velocity dependent effects are explicitly taken into account in a complete analytical description. Simulations are presented for parameters of the ELSA photo-cathode.

TUP100 The Optimization of a DC Injector for the Energy Recovery Linac Upgrade to APS emittance, laser, gun, linac 639
  • Y.-E. Sun, M. Borland, K.C. Harkay, Y.L. Li, H. Shang
    ANL, Argonne

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An energy recovery linac based light source is a potential revolutionary upgrade to the Advanced Photon Source (APS) at Argonne National Laboratory. The concept relies on several key research areas, one of which is the generation of ultra-low emittance, high-average-current electron beams. In this paper, we present our investigation of a dc-gun-based system for ultra-low emittance bunches in the 20 pC range. A parallel multi-objective numerical optimization is performed in multi-parameter space. Parameters varied include experimentally feasible drive-laser shapes, the dc gun voltage, and the thermal energy of the emitted photo-electrons. Our goal is to deliver a 10 MeV, 20 pC bunch at the entrance of the linac with an emittance of 0.1 μm or lower, rms bunch length of 2 to 3 ps, and energy spread no larger than 140 keV. We present the machine parameters needed to generate such an injector beam, albeit without a merger.

TUP101 Photocathode R&D Program at LBNL photon, emittance, gun, cathode 642
  • W. Wan, C.E. Coleman-Smith, C.M.R. Greaves, H.A. Padmore, E. Pedersoli, A. Polyakov
    LBNL, Berkeley, California
  • G. Ferrini, M. Montagnese, S. Pagliara, F. Parmigiani
    Università Cattolica-Brescia, Brescia

Funding: US Deparment of Energy
The photocathode R&D program at Lawrence Berkeley National Laboratory is presented, including the status of the lab and experimental results. We will also present experimental result obtained at Brescia Italy and theoretical work on predicting minimum thermal emittance from metal cathodes and emittance growth due to stochastic Coulomb interaction.

TUP103 Analysis of Halo Formation in a DC Photoinjector cathode, space-charge, emittance, laser 645
  • D. Mihalcea, P. Piot
    Northern Illinois University, DeKalb, Illinois

Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University
We discovered, by modeling the AES/JLab direct-current photoinjector with several beam-simulation codes, that nominal injector settings would create a large diffuse beam halo as a consequence of the internal space-charge force in the beam. The injector-induced halo is sensitive to the injector settings, but if the settings are judiciously chosen, it can be largely circumvented. We present an exploration of the parameter space for the AES/JLab photoinjector. Measurement of beam halo will be a crucial aspect of commissioning this machine.

TUP104 A High-Brightness Low-Energy Photoinjector Option for the Fermilab Electron Accelerator Facility radiation, synchrotron, synchrotron-radiation, collective-effects 648
  • P. Piot, D. Mihalcea
    Northern Illinois University, DeKalb, Illinois
  • M. Church, S. Nagaitsev, Y.-E. Sun
    Fermilab, Batavia
  • I.V. Pogorelov
    LBNL, Berkeley, California

Funding: Work supported by Fermi Research Alliance LLC. Under DE-AC02- 07CH11359 with the U.S. DOE and by the Department of Education under contract P116Z010035 with Northern Illinois University
Fermilab is currently constructing a GeV-scale electron accelerator test facility. The accelerator will serve as a backbone for several Fermilab R&D programs, e.g., to test subsystem associated to project-X, ILC and the muon collider program. It is also anticipated that this facility will support beam physics and accelerator R&D programs such as testing of novel acceleration techniques, beam diagnostics and radiation sources concepts. In this paper we describe a possible option for the electron injector based on a photoemission rf gun. Optimization and performance studies of this ~50 MeV photoinjector are performed with various tracking programs (Astra, GPT, Impact-T, Impact-Z). We explore the performances of the magnetic bunch compressor which is extremely challenging at 50 MeV due to strong phase space dilution via collective effects (space charge and coherent synchrotron radiation). We also investigate the generation of flat beams with very high transverse emittance ratio using a round-to-flat beam transformer.

TUP106 Simulation of Field-Emission Cathodes for High Current Electron Injectors cathode, simulation, FEL, gun 652
  • D. Mihalcea, P. Piot
    Northern Illinois University, DeKalb, Illinois

Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University
From the prospect of the high average current electron injectors, the most important advantage of the field-emission cathodes is their capability to generate very large current densities. Simulation of field-emission cathodes is complicated by the large range of spatial dimensions: from sub-micron scale, for a single field-emission tip, to millimeter scale, for a field-emitter array. To overcome this simulation challenge our numerical model is split in two steps. In the first step, only electrons emitted by a single tip are considered. In the second step, the beams originating from many single emitting tips are merged together to mimic the field-emitter array configuration. We present simulation results of injector based on field array emitters cathodes.

TUP111 Longitudinal Bunch Lengthening Compensation in a High Charge RF Photoinjector emittance, gun, booster, solenoid 661
  • S. Pei, C. Adolphsen
    SLAC, Menlo Park, California

Funding: Work supported by DOE contract DE-AC02-76SF00515
In high charge rf photo-injectors, due to the strong longitudinal space charge, bunch lengthening can readily occur. This paper presents beam dynamics studies of such bunch lengthening and methods to compensate it. With these methods, not only can the bunch length be preserved, but it can be shortened at the photo-injector exit.

TUP112 Laser Timing Jitter Measurements at the Fermilab A0 Photoinjector laser, cavity, linac, emittance 664
  • J.K. Keung
    University of Pennsylvania, Philadelphia, Pennsylvania
  • S. Nagaitsev, J. Ruan
    Fermilab, Batavia

The Fermilab A0 Photoinjector is a 16 MeV high-intensity, low emittance electron linac used for advanced accelerator R&D. To achieve a high quality beam here it is important to maintain a stable laser in terms of both intensity and timing. This paper presents our measurement of the laser timing jitter, which is the random late or early arrival of the laser pulse. The seed laser timing jitter has been measured to less than 200 fs, by examining the power spectrum of the signal of a fast photodiode illuminated by it. The pulsed and pumped laser timing jitter has been measured with limited resolution to less than 1.4 ps, by examining the phase of a cavity impulsively excited by the signal from a fast photodiode illuminated by the laser pulse.

TUP113 Emittance Exchange at the Fermilab A0 Photoinjector cavity, emittance, optics, dipole 667
  • T.W. Koeth
    Rutgers University, The State University of New Jersey, Piscataway, New Jersey
  • L. Bellantoni, H.T. Edwards, R.P. Fliller, A.S. Johnson, A.H. Lumpkin, J. Ruan, R. Thurman-Keup
    Fermilab, Batavia

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
An experiment has been developed at the Fermilab A0 Photoinjector Lab to demonstrate the exchange of longitudinal emittance with the horizontal emittance. Our apparatus consists of a 3.9 GHz TM110 deflecting rf cavity placed between two magnetic dogleg channels. The first dogleg generates the needed dispersion to appropriately position the off-momentum electrons in the TM110 cavity. The TM110 cavity reduces the momentum spread and imparts a time dependent transverse kick. The second dogleg finishes the exchange and yields the exchange of the emittances. We report on the measurement of the exchange beamline matrix elements as well as an inital report on measuring the exchange emittances directly.


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TUP115 Beam Transport Effects for ECRIS ion, extraction, ECRIS, ion-source 670
  • P. Spädtke, R. Lang, J. Mäder, J. Roßbach, K. Tinschert
    GSI, Darmstadt

Experimental results from ion beams, extracted from an Electron Cyclotron Resonance ion source (ECRIS) are presented and compared with different models used for simulation. The model for the simulation has to satisfy different facts: The energy of ions within the plasma is in the eV-range. Electrons have a different energy distribution: there are hot electrons (up to MeV range), but also low energy electrons, responsible for charge neutrality within the plasma. Because the gyration radius of ions is within the mm-range and below, ions can be extracted only if they are located on a magnetic field line which goes through the extraction aperture. Because of the gradient dBz/dz of the mirror field only these ions can be extracted, which have enough energy in direction of the field line. These conditions are fulfilled for ions which are going to be lost through the loss cone created by the hexapole. The extracted beam shows a typical behavior for an ECRIS: when the beam is focused by a lens (here a solenoid) directly behind extraction, the initial round and hollow beam develops wings with a 120-degree symmetry. These wings has influence on the beam emittance.

TUP117 Development of Ultra-Low Emittance Injector for Future X-Ray FEL Oscillator emittance, linac, cavity, gun 676
  • P.N. Ostroumov, K.-J. Kim
    ANL, Argonne
  • P. Piot
    Northern Illinois University, DeKalb, Illinois

Funding: This work was supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC-02-06CH11357.
An XFELO proposed recently* requires a continuous sequence of electron bunches with ultra-low transverse emittance less than 0.1 mm-mr, a bunch charge of 40 pC, an rms energy spread of 1.4 MeV, repeating at a rate between 1 MHz to 100 MHz. The bunches are to be compressed to an rms lengths less than 2 ps at the final energy of 7 GeV. Following the successful commissioning of the pulsed injector based on a thermionic gun** we discuss a concept for ultra-low emittance injector to produce 100 MHz CW electron bunches. The electron beam is extracted by ~1MV rf voltage using low frequency ~100 MHz room temperature rf cavity. The injector also includes a chicane and slits to form a short ~1 nsec bunch, a pre-buncher a booster buncher to form low longitudinal emittance of the bunched beam, an accelerating section to ~50 MeV using higher harmonic cavities, and an rf cosine-wave chopper to form any required bunch repetition rate between 1 MHz and 100 MHz. The results of initial optimizations of the beam dynamics with the focus on extracting and preserving ultra-low emittance will be presented.

*K.-J. Kim, Y. Shvyd'ko, and S. Reiche, to be published in Physical Review Letters (2008)
**K. Togawa, et al., Phys. Rev. STAB 10, 020703 (2007)

TUP120 EBIS Preinjector Construction Status linac, ion, rfq, booster 685
  • J.G. Alessi, D.S. Barton, E.N. Beebe, S. Bellavia, O. Gould, A. Kponou, R.F. Lambiase, E.T. Lessard, V. LoDestro, R. Lockey, M. Mapes, D.R. McCafferty, A. McNerney, M. Okamura, A. Pendzick, D. Phillips, A.I. Pikin, D. Raparia, J. Ritter, J. Scaduto, L. Snydstrup, M. Wilinski, A. Zaltsman
    BNL, Upton, Long Island, New York
  • U. Ratzinger, A. Schempp
    IAP, Frankfurt am Main

Funding: Work supported by the US Department of Energy and the National Aeronautics and Space Agency
A new heavy ion preinjector is presently under construction at Brookhaven National Laboratory. This preinjector uses an Electron Beam Ion Source (EBIS), and an RFQ and IH Linac, both operating at 100 MHz, to produce 2 MeV/u ions of any species for use, after further acceleration, at the Relativistic Heavy Ion Collider, and the NASA Space Radiation Laboratory. Among the increased capabilities provided by this preinjector are the ability to produce ions of any species, and the ability to switch between multiple species in 1 second, to simultaneously meet the needs of both physics programs. Fabrication of all major components for this preinjector is in process, with testing of the EBIS and RFQ starting this year. The status of this construction will be presented.


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WE101 Energy Recovered Linacs linac, emittance, laser, storage-ring 688
  • G.A. Krafft
    JLAB, Newport News, Virginia

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In the last decade, stimulated by the success of the energy recovered free electron lasers, many projects have been initiated exploring the applications and limitations of beam energy recovery in recirculated linear accelerators (linacs). In this talk the performance of many existing energy recovered linacs is briefly reviewed. Looking forward, potential applications of energy recovered linacs such as

  1. recirculated linac light sources,
  2. high energy beam electron cooling devices, and
  3. electron beam sources for high energy colliders have been pursued with varying degrees of effort.
The types of new technology that must be developed for applications, and more broadly, some of the open issues regarding this technology, are discussed in detail. The talk concludes with some thoughts on the future developments in this important, and expanding field.


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TH104 An Overview of Linac Ion Sources ion, plasma, ECR, ion-source 740
  • R. Keller
    LANL, Los Alamos, New Mexico

Funding: This work was supported by the US Department of Energy under Contract Number DE-AC52-06NA25396
For the purpose of this presentation, the term Linac is narrowed down to comprise rf machines that accelerate ion beams at duty factors between about 5% and continuous operation. This group of Linacs includes proton and H- machines as well as accelerators utilizing multi-charged heavy ions, mostly for nuclear physics applications. Main types of ion sources serving these Linacs include Electron Cyclotron Resonance (ECR) sources, filament and rf driven multi-cusp sources, Penning (PIG) sources and duoplasmatrons. This presentation does not strive to attain encyclopedic character but rather to highlight current trends in performance parameters, major lines of development and type-specific limitations and problems, with emphasis on ECR and multi-cusp sources. The main technical aspects being discussed are ion production and beam formation.


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TH201 Charge State Boosters for Radioactive Ion Acceleration ion, ECRIS, plasma, ion-source 745
  • F. Ames
    TRIUMF, Vancouver

For the post acceleration of radioactive ions produced at ISOL facilities the increase of the charge state is essential to reduce the A/q requirements of the accelerators. Many of those existing or proposed facilities are relying on the performance of charge state boosters of EBIS or ECRIS type. Although, in principle both types of sources can be used in pulsed or continuous mode operation an EBIS is better suited for pulsed beams whereas an ECRIS is most efficient in a continuous mode. The present state of the art with respect to existing data of both sources will be presented and potential future developments will be discussed. Latest results from the on line commissioning of a PHOENIX ECRIS charge breeder at ISAC will be presented.


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THP001 Nb-RRR Sheet Inspection by Means of Ultrasonic Microscopy cavity, niobium, diagnostics, superconducting-RF 771
  • R. Grill, H. Kestler, L.S. Sigl, H. Traxler
    Plansee Metall GmbH, Reutte

Nb-RRR sheet material is one of the key components of super conducting linear particle accelerator projects (e.g. XFEL, ILC). The high quality requirements led to sophisticated quality systems in the manufacturing line. A major aspect is the development of non-destructive inspection methods for the detection of surface defects, delaminations, and inclusions. Up to now the standard inspection technologies for quality assurance of Nb-RRR sheet material are based on electromagnetic techniques, e.g. SQUID and eddy current. For these methods the detection limit is in the range of 0.1 mm. Ultrasonic microscopy (USM) in the frequency range of 1 GHz is a well established and economic technique for non-destructive surface inspection. For volume inspection of sheet material ultrasonic frequencies of 50 to 100 MHz are applied. For Nb-RRR sheets with typical thickness of 2.8 mm a detection limit of 0.1 mm is expected. First results of USM on Nb-RRR sheet material are presented.

THP016 Analysis of Quenches Using Temperature Mapping in 1.3 GHz SCRF Cavities at DESY cavity, superconducting-cavity, superconductivity, synchrotron 812
  • D. Reschke
    DESY, Hamburg

The local thermal breakdown (quench) behavior of one- and nine-cell SCRF Nb accelerator cavities is investigated systematically. For more than 50 cavities, temperature mapping data have been analyzed with respect to surface preparation, Nb material etc. Results on quench location and characteristic correlations are presented.

THP027 Welding Helium Vessels to the 3.9 GHz Superconducting Third Harmonic Cavities cavity, monitoring, cryomodule, emittance 842
  • M.H. Foley, T.T. Arkan, H. Carter, H.T. Edwards, J. Grimm, E.R. Harms, T.N. Khabiboulline, D.V. Mitchell, D.R. Olis, T.J. Peterson, P.A. Pfund, N. Solyak, D.J. Watkins, M. Wong
    Fermilab, Batavia
  • G. Galasso
    University of Udine, Udine

Funding: This work was supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The 3.9 GHz 3rd harmonic cavities are designed to serve as compensation devices for improving the longitudinal emittance of the free-electron laser FLASH at DESY. These cavities operate in the TM010 mode, and will be located between the injector and the accelerating cavities. Fermilab is obligated to provide DESY with a cryomodule containing four 3rd harmonic cavities. In this paper we discuss the process of welding helium vessels to these cavities. Included will be a description of the joint designs and weld preparations, development of the weld parameters, and the procedure for monitoring the frequency spectrum during TIG welding to prevent the cavity from undergoing plastic deformation. Also discussed will be issues related to qualifying the dressed cavities as exceptional vessels (relative to the ASME Boiler and Pressure Vessel Code) for horizontal testing and eventual installation at DESY, due to the necessary use of non-ASME code materials and non-full penetration electron beam welds.

THP035 Multipactor in Minimum Electric Field Regions of Transmission Lines and Superconducting RF Cavities cavity, multipactoring, simulation, superconducting-RF 860
  • S.A. Belomestnykh, V.D. Shemelin
    CLASSE, Ithaca, New York

Funding: Work is supported by the National Science Foundation grant PHY 0131508
Multipactor in beam-pipe transitions of superconducting rf cavities can be explained using rf potential well theory*. In this paper we present simulation results supporting this explanation for both rf cavities and transmission lines.

*S. Belomestnykh and V. Shemelin, "Multipacting-free Transitions between Cavities and Beam-pipes," submitted to Nuclear Instruments and Methods in Physics Research A.

THP037 RF Design of a Spoke Resonator for High Power Free-Electron Lasers HOM, free-electron-laser, laser, acceleration 866
  • F.L. Krawczyk, D.C. Nguyen
    LANL, Los Alamos, New Mexico
  • S.J. Cooke
    NRL, Washington, DC
  • B. Rusnak
    LLNL, Livermore, California
  • T.I. Smith
    Stanford University, Stanford, Califormia
  • E.L. Wright
    Beam-Wave Research, Inc., Union City

Funding: Supported by the High-Energy Laser Joint Technology Office
We are investigating spoke resonators that originally were proposed for moderate energy proton acceleration for application in high-average-current free-electron lasers (FEL). This structure holds the promise of alleviating the BBU limitations of conventional rf structures. Spoke resonator have several advantages: 1) strong coupling simplifies the access to higher order modes (HOM), 2) at the same frequency a spoke resonator is about half the size of an elliptical resonator, 3) the spokes provide additional mechanical stability and stiffening , 4) the power and HOM couplers can be attached to the cavity body and do not take up additional space along the length of the accelerator, 5) the presence of the spokes limits the polarizations of the HOMs to two orientations which facilitates the selection of HOM coupler positions. The rf performance of a spoke resonator specifically designed for high-current electron applications (beta=1.0) will be presented and compared with the expected performance of elliptical resonators designed for such applications. Besides the structure's effectiveness for acceleration also HOM properties will be presented.


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THP043 Preliminary Results from Multi-Cell Seamless Niobium Cavities Fabricated by Hydroforming cavity, niobium, cryogenics, vacuum 882
  • W. Singer, I. Jelezov, A. Matheisen, X. Singer
    DESY, Hamburg
  • G. Ciovati, P. Kneisel, M. Morrone
    JLAB, Newport News, Virginia

Funding: This manuscript has been partially authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The technology of forming multi-cell seamless niobium cavities has been developed at DESY within the European CARE (Coordinated Accelerator Research in Europe) program. Three cell units have been manufactured successfully and a 9-cell cavity has recently been completed from three sub-sections and will be tested in the near future. Meanwhile, we have equipped two 3-cell units – one center unit of a 9-cell cavity and one end-unit – with niobium beam pipes, have tuned these units and carried out cryogenic rf tests after standard bcp surface treatments had been applied to these cavities. In addition, we will take temperature maps with Jlab's two-cell thermometry system; since in cavities fabricated by 'standard' methods such as deep drawing of half cells and electron beam welding cavity performance limitations have often been found at or near equator welds. It will be of particular interest to compare the seamless cavity quench locations to those from standard cavities. This contribution will report about the cryogenic test results and the T-mapping findings.

THP045 Twisted Structures and Their Application as Accelerating Structures cavity, simulation, superconducting-cavity 888
  • J.L. Wilson, Y.W. Kang
    ORNL, Oak Ridge, Tennessee
  • A.E. Fathy
    University of Tennessee, Knoxville, Tennessee

Funding: This work has been sponsored by ORNL-SNS. The Spallation Neutron Source is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
Normally, reactive loading is employed to construct accelerating cavities in order to slow the phase velocity of the electromagnetic wave. However, due to their non-uniform cross section, they tend to be difficult to machine, requiring complicated welding or brazing processes which increase the total cost. Although empty straight waveguides can only support faster-than-light propagation, empty twisted waveguides can support propagation at or below c. Because twisted structures have a uniform cross section in the transverse plane, they offer several potential advantages over dielectric loaded structures or other types of periodic structures. Of particular interest are twisted structures whose longitudinal cross section has been selected to resemble well-known accelerating structures, such as the iris-loaded accelerating structure and the TESLA type elliptical cavity. Comparisons are drawn between these conventional cavities and their twisted counterparts. Specifically, the phase velocity and dispersion relationship are discussed, the accelerating mode is found and analyzed, and R/Q is calculated. Design guidelines for the design of twisted structures are given.

THP057 Development of RF Cavities for the SHB System of the L-band Electron Linac at Osaka University cavity, linac, resonance, single-bunch 918
  • G. Isoyama, S. Kashiwagi, R. Kato, M. Morio, S. Suemine
    ISIR, Osaka

Funding: This research is partly supported by the accelerator support program to universities conducted by the High Energy Accelerator Research Organization in Japan.
The 40 MeV L-band electron linac at the Institute of Scientific and Industrial Research, Osaka University is operated for joint-use in Osaka University. It is equipped with a three-stage sub-harmonic buncher (SHB) system consisting of two 108 MHz and a 216 MHz rf cavities to produce a high-intensity single-bunch beam. They were quarter-wavelength coaxial cavities made of a clad plate of copper on stainless steel and were inefficiently cooled with water flowing through a pipe wound on their outer surfaces made of stainless steel. We have renewed the cavities with new ones made only of oxygen-free copper to solve the problem. We made physical design and basic mechanical design of the new rf cavities by ourselves by taking a mechanical design of the SHB cavity of the electron-positron linac at KEK, Japan as a model. Special care was devoted in the mechanical design to cool the most part of the cavities directly with water instead of relying on heat conductivity in copper so that they are stable in regard to temperature. They have been installed in the linac and have been working well in expected performance. We will report details of design and fabrication of the new SHB cavities.

THP058 Accelerating Structure for C-Band Electron Linear Accelerator Optimization impedance, coupling, vacuum, cavity 921
  • S.V. Kutsaev, A. Anisimov, N.P. Sobenin
    MEPhI, Moscow
  • M.A. Ferderer, A.A. Krasnov, A.A. Zavadtsev
    ScanTech, Atlanta, Georgia

The results of analysis and comparison of different linear accelerator designs for 10 MeV facility powered by 4.5 MW klystron on 5712 MHz operation frequencies presented. Several concepts of accelerator including standing wave and traveling wave ones with either rf or magnetic focusing were considered. Cells geometry and beam dynamics parameters in these types of accelerators featuring high capture factor were obtained using numeric simulation methods. The computer simulation code for traveling wave linac optimization based on beam dynamics with space charge consideration was developed. Accelerating structures and input coupler for traveling wave linac along with standing wave one were designed. The task of energy variation was solved.

THP066 Breakdown in Pressurized RF Cavities cavity, simulation, vacuum, emittance 945
  • R. Sah, M. Alsharo'a, R.P. Johnson, M.L. Neubauer
    Muons, Inc, Batavia
  • M. BastaniNejad, A.A. Elmustafa
    Old Dominion University, Norfolk, Virginia
  • J.M. Byrd, D. Li
    LBNL, Berkeley, California
  • D. Rose, C.H. Thoma, D.R. Welch
    Voss Scientific, Albuquerque, New Mexico
  • G.M. Wang
    ODU, Norfolk, Virginia

The performance of many particle accelerators is limited by the maximum electric gradient that can be realized in rf cavities. Recent studies have shown that high gradients can be achieved quickly in 805 MHz cavities pressurized with dense hydrogen gas, because the gas can suppress, or essentially eliminate, dark currents and multipacting. In this project, two new test cells operating at 500 MHz and 1.3 GHz will be built and tested, and the high pressure technique will be used to suppress the vacuum effects of evacuated rf cavities, so that the role of metallic surfaces in rf cavity breakdown can be isolated and studied as a function of external magnetic field, frequency, and surface preparation. Previous studies have indicated that the breakdown probability is proportional to a high power of the surface electromagnetic field, in accordance with the Fowler-Nordheim description of electron emission from a cold cathode. The experiments will be compared with computer simulations of the rf breakdown process.

THP075 X-Band Traveling Wave RF Deflector Structures impedance, kicker, emittance, factory 966
  • J.W. Wang, S.G. Tantawi
    SLAC, Menlo Park, California

Funding: Work supported by U.S. Department of Energy, contract DE-AC02-76SF00515 (SLAC)
Design studies on the X-Band transverse rf deflectors operating at HEM11 mode have been made for two different applications. One is for beam measurements of time-sliced emittance and slice energy spread for the upgraded LCLS project, its optimization in rf efficiency and system design are carefully considered. Another is to design an ultra-fast rf kicker in order to pick up single bunches from the bunch-train of the B-factory storage ring. The challenges are to obtain very short structure filling time with high rf group velocity and good rf efficiency with reasonable transverse shunt impedance. Its rf system will be discussed.

THP086 Cold Cathode Electron Tube Toward Plenty Multi Beam Tube cathode, cavity, high-voltage, simulation 990
  • M. Yoshida
    KEK, Ibaraki
  • H. Hioka, S. Someya
    SUT, Noda-shi, Chiba
  • U. Utsunomiya
    University of Tokyo, Tokyo

The multi beam electron tube with a lot of beam pipes is required for the low applied voltage and the high frequency because the efficiency has a limit according to the perveance. However, the total heater power becomes too high if many thermal cathodes are used. Thus the cold cathode such as the carbon nano tube (CNT) is suitable for such a multi beam electron tube. Further the cold cathode has the advantage to work as a switching device since the metal grid close to the cathode can be used. The design and the fundamental test of the partial model will be presented.

THP122 Overview of the First Five Refurbished CEBAF Cryomodules cryomodule, cavity, vacuum, linac 1084
  • M.A. Drury, E. Daly, G.K. Davis, J.F. Fischer, C. Grenoble, J. Hogan, F. Humphry, L.K. King, J.P. Preble, K. Worland
    JLAB, Newport News, Virginia

Funding: Authored by JSA, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The Thomas Jefferson National Accelerator Facility is currently engaged in a cryomodule refurbishment project. The goal of this project is robust 6 GeV, 5 pass operation of the Continuous Electron Beam Accelerator Facility (CEBAF). The scope of the project includes removing, refurbishing and replacing ten CEBAF cryomodules at a rate of three per year. Refurbishment includes reprocessing of SRF cavities to eliminate field emission and increase the nominal gradient from the original 5 MV/m to 12.5 MV/m. New 'dogleg' couplers between the cavity and helium vessel flanges will intercept secondary electrons that produce arcing at the 2 K ceramic window in the Fundamental Power Coupler (FPC). Modification of the Qext of the FPC will allow higher gradient operations. Other changes include new ceramic rf windows for the air to vacuum interface of the FPC and improvements to the mechanical tuners. Any damaged or worn components will be replaced as well. Currently, five refurbished cryomodules have been installed in CEBAF. These cryomodules have been installed in CEBAF and are currently operational. This paper will summarize the test results and current operational experience.

FR101 8-GeV C-Band Accelerator Construction for XFEL/SPring-8 klystron, high-voltage, FEL, cavity 1090
  • T. Inagaki
    RIKEN/SPring-8, Hyogo

The 8 GeV C-band electron linear accelerator is under construction at the SPring-8 site aiming at generating an FEL X-ray beam in 2010. C-band accelerator technology has been developed initially at KEK for the e+e- linear collider project, and employed at the XFEL project in Japan. Since C-band generates a high gradient acceleration field as high as 35 MV/m, the total length of the accelerator fits within 400 m, including the injector and three bunch compressors. C-band uses normal conducting rf technology, thus it runs in pulse mode at 60 Hz, which is well suited to XFEL operation and is less expensive. The talk will cover the current status of the XFEL project and hardware production.


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FR102 Commissioning of the LCLS Linac emittance, laser, linac, FEL 1095
  • H. Loos, R. Akre, A. Brachmann, F.-J. Decker, Y.T. Ding, D. Dowell, P. Emma, J.C. Frisch, A. Gilevich, G.R. Hays, P. Hering, Z. Huang, R.H. Iverson, C. Limborg-Deprey, A. Miahnahri, S. Molloy, H.-D. Nuhn, J.L. Turner, J.J. Welch, W.E. White, J. Wu
    SLAC, Menlo Park, California
  • D.F. Ratner
    Stanford University, Stanford, Califormia

Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
Construction of the Linac Coherent Light Source (LCLS) X-ray free electron laser at the Stanford Linear Accelerator Center (SLAC) is nearing completion. A new injector and upgrades to the existing accelerator were installed in two phases in 2006 and 2007. We report on the commissioning of the injector, the two new bunch compressors at 250 MeV and 4.3 GeV, and transverse and longitudinal beam diagnostics up to the end of the existing linac at 13.6 GeV. The commissioning of the new transfer line from the end of the linac through the undulator beam line to the main dump is scheduled to start in January 2009 and for the undulator magnets in March 2009 with first light to be expected by May 2009.


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FR103 Operation of FLASH as an FEL User Facility FEL, radiation, photon, gun 1100
  • K. Honkavaara
    DESY, Hamburg

FLASH, the FEL user facility at DESY, is operated with an electron beam energy up to 1 GeV corresponding to a photon wavelength down to 6.5 nm. The full year 2008 is dedicated to beam operation: about half of the time is scheduled for FEL users, and the rest for accelerator and FEL physics studies. Operational experience gathered at FLASH is very important not only for further improvements of the FLASH facility itself, but also for the European XFEL and for the ILC R&D effort. This talk reports our experience operating FLASH as a user facility. Failure statistics are included as well.


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FR104 Review of Advanced Laser Technologies for Photocathode High-Brightness Guns laser, polarization, cathode, gun 1105
  • H. Tomizawa, H. Dewa, H. Hanaki, A. Mizuno, T. Taniuchi
    JASRI/SPring-8, Hyogo-ken

I developed a 3-D pulse shaping system in UV as an ideal laser for yearlong stable photoinjector. At SPring-8, the laser's pulse-energy stability has been improved to 0.7~1.4% at the UV (263 nm) under the laser environmental control included humidity. In addition, the ideal spatial and temporal profiles of an UV-laser pulse are essential to suppress emittance growth in an rf gun. I apply a deformable mirror that automatically shapes the spatial profile with a feedback routine, based on a genetic algorithm, and a pulse stacking system consisting of three birefringence Alpha-BBO crystal rods for temporal shaping at the same time. The 3D shape of the laser pulse is spatially top-hat (flattop) and temporally a square stacked chirped pulse. Using a 3D-shaped laser pulse with diameter of 0.8 mm on the cathode and pulse duration of 10 ps (FWHM), we obtain a normalized emittance of 1.4 pi mm mrad with a beam energy of 26 MeV. To keep the mirror away from beam axis, I developed a new hollow laser incidence with an axicon final focusing. Furthermore, I am developing a laser-induced Schottky-effect-gated photocathode gun using Z-polarization of the laser source with the hollow incidence.


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FR105 Billion Particle Linac Simulations for Future Light Sources linac, simulation, space-charge, FEL 1110
  • J. Qiang, R.D. Ryne, M. Venturini, A. Zholents
    LBNL, Berkeley, California

Funding: This work was supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC03-76SF00098.
In this paper, we will report on a billion macroparticle simulation of beam transport in a free electron laser (FEL) linac for future light source applications. The simulation includes a self-consistent calculation of 3D space-charge effects, short-range geometry wakefields, longitudinal coherent synchrotron radiation (CSR) wakefields, and detailed modeling of rf acceleration and focusing. We will discuss the needs and the challenges for such large-scale simulation. Application to the study of microbunching instability in the FEL linac will also be presented.


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