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scattering

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MOPLT047 Lattice Design Study for HESR background, wiggler, extraction, undulator 653
 
  • Y. Senichev, S. An, K. Bongardt, R. Eichhorn, A. Lehrach, R. Maier, S. Martin, D. Prasuhn, H. Stockhorst, R. Tölle
    FZJ/IKP, Jülich
  The important feature of High Energy Storage Ring is the combination of phase space cooled beams with internal targets, which allows to reach high luminosities up to 2*1032cm-2s-1. However, the requirement to have the strongly focused beam on the target causes the high chromaticity value on the target straight section and as in result to the squeezing of dynamic aperture after sextupole correction of the chromaticity. Simultaneously, the momentum-compaction factor is one of the most important characteristics of an accelerator, which defines the collective instability threshold. Therefore, the HESR lattice has to have the following features: low or negative momentum compaction factor, dispersion free straight sections, convenient method to correct the chromaticity by the sextupoles, sufficiently large dynamic aperture. In this work we develop lattice, which meets all these requirements for HESR.  
 
MOPLT048 High Current Switch-mode Power Converter Prototype for LHC Project 6kA, 8V background, wiggler, extraction, undulator 656
 
  • E. Jauregi, J.M. Del Río, J.M. Dela Fuente, M. Tellería, J.R. Zabaleta
    JEMA GJ, Lasarte-Oria
  • F. Bordry, V. Montabonnet
    CERN, Geneva
  • E.F. Figueres
    E.T.S.I.I., Valencia
  For the Large Hadron Collider (LHC) accelerator being constructed on the CERN site, very precise variable DC currents are required. The company JEMA had during year 2002, designed, manufactured and tested a power converter prototype according to CERN specifications, particularly demanding in terms of dc stability and dynamic response. The power converter is formed by four sub-converters 8V, 2kA in parallel. Isolation between mains input and magnet load is at high frequency done, 40 kHz, which means a volume reduction and better mains perturbations rejection. IGBT inverter soft switch-mode power conversion in ZVS operation reduces dramatically commutation losses, increasing total efficiency of the power converter. The sub-converter, regulated by a wide band width current loop in ACC mode, follows the current reference calculated by the overall voltage loop, providing a good sharing of the output currents and high output stability. The design of the water cooled power converter, results in a very reduce volume and modular structure, providing the system a very flexible exchangeability. The power converter was tested and accepted by CERN into year 2003, some minor points were left to be adjusted during the pre-series stage.  
 
THPLT046 The Synchrotron Radiation Beamline at TTF2 antiproton, positron, radiation, simulation 2583
 
  • O. Grimm, S. Casalbuoni, L. Fröhlich, O. Peters, J. Rossbach
    DESY, Hamburg
  The VUV-FEL at DESY, Hamburg, will require novel techniques to characterize the longitudinal charge distribution of the electron bunches that drive the free-electron laser. Conventional methods are inadequate at the short bunch lengths that will be obtained. One technique under study uses coherent far-infrared radiation to reconstruct the bunch shape through Fourier analysis of the spectrum. In a first step, a beam line to guide both far-infrared (50-1000 um) and optical synchrotron radiation from one of the bunch compressor magnets of the linear accelerator to a diagnostic station outside of the controlled area is currently under construction. It will also allow a comparison between streak camera and far-infrared measurements for features on length scales above some 100 um (the streak camera resolution). Later, infrared techniques extending to shorter wavelengths, i.e. to shorter bunch lengths, will also be used further downstream the accelerator, employing synchrotron, transition and undulator radiation. The beam line design, measurement principle and first measurements will be presented.  
 
THPLT047 Beam Position Monitor Development for the IThemba LABS Cyclotron Beamlines antiproton, positron, radiation, simulation 2586
 
  • J. Dietrich, I. Mohos
    FZJ/IKP, Jülich
  • A.H. Botha, J.L. Conradie, J.L.G. Delsink, P.F. Rohwer
    IThemba Labs, Somerset West
  In cooperation of iThemba LABS (South Africa) and Forschungszentrum Juelich the specification of a sensitive tunable rf narrowband beam position monitor system for cyclotron beamlines has been elaborated. iThemba LABS developed and manufactured the four section stripline monitor chamber. The monitor electronics were developed in the Forschungszentrum Juelich-IKP. The electronics consisting of an RF signal processing module (BPM-RF) and a data acquisition and control module (BPM-DAQ) sequentially processes and measures the monitor signals and deliver via serial network calculated horizontal and vertical beam position data. First measurements with cyclotron beam has been performed in the iThemba LABS in November 2003. Changed beam position due to changing different cyclotron parameters could be studied with high accuracy. The resolution of the beam position measurement was better than 0.1 mm with beam currents down to 0.0005 mA.  
 
THPLT048 Progress in 3D Space-charge Calculations in the GPT Code antiproton, positron, radiation, simulation 2589
 
  • G. Pöplau, U. Van Rienen
    Rostock University, Faculty of Engineering, Rostock
  • M.J. de Loos
    PP, Soest
  • S.B. van der Geer
    TUE, Eindhoven
  The mesh-based 3D space-charge routine in the GPT (General Particle Tracer, Pulsar Physics) code scales linearly with the number of particles in terms of CPU time and allows a million particles to be tracked on a normal PC. The crucial ingredient of the routine is a non-equidistant multi-grid Poisson solver to calculate the electrostatic potential in the rest frame of the bunch. The solver has been optimized for very high and very low aspect ratio bunches present in state-of-the-art high-brightness electron accelerators. In this paper, we explore the efficiency and accuracy of the calculations as function of meshing strategy and boundary conditions.  
 
THPLT050 End to End Simulations of the RX2 Beam Transport antiproton, positron, radiation, simulation 2592
 
  • N. Pichoff, J.-M. Lagniel
    CEA/DAM, Bruyères-le-Châtel
  RX2 is a project aiming to produce a high flux of X-rays for radiography purpose. We proposed an RF linac using a DC photo-injector producing 20 bunches with 100nC each at 352 MHz. The beam is then injected in 4 RF superconducting cavities and accelerated to 40 MeV. It is then focused on a target producing X-rays. Here is presented the design, the specificities, and the beam simulations from the cathode to the target by coupling 2 multiparticle codes : PARMELA and PARTRAN.  
 
THPLT051 End to End Multiparticle Simulations of the AIRIX Linac antiproton, positron, radiation, simulation 2595
 
  • N. Pichoff, A. Compant La Fontaine
    CEA/DAM, Bruyères-le-Châtel
  AIRIX is a working 3 kA, 20 MeV induction accelerator. It has been designed with an enveloppe code : ENV. A new set of multiparticle codes (PBGUNS, MAGIC, PARMELA and PARTRAN) has been used recently to simulate the beam transport with an higher accuracy especially taking into account the field non-linearities. A dedicated space-charge routine has been written. The calculation results have been compared to experimental measurements.  
 
THPLT052 Measurement of Relative Gas Chamber Pressure in Narrow Straight Section Vacuum Vessels by Observing Gas Bremstrahlung vacuum, antiproton, positron, radiation 2598
 
  • G.A. Naylor, B. Joly, D. Robinson
    ESRF, Grenoble
  The measurement of gas pressure inside long, small cross section, vacuum vessels is difficult due to the distance between the centre of the vacuum vessel and vacuum gauges (leading to a low vacuum conductance). Following initial chamber installation, significant out-gassing is observed leading to a significant pressure bump within the chamber. A modified beam loss detector has been developed in order to monitor the gamma radiation produced by the collision of the 6GeV electrons in the storage ring with residual gas atoms. The narrow beam of gamma radiation is intercepted at various points by high Z materials in the beam line front-end allowing a radiation shower to be detected outside the vacuum vessel proportional to the gas pressure in the corresponding storage ring straight section. Various locations are considerred and results shown.  
 
THPLT056 Horizontal Instability and Feedback Performance in DAFNE e+ Ring vacuum, antiproton, feedback, radiation 2610
 
  • A. Drago
    INFN/LNF, Frascati (Roma)
  In DAFNE, after the 2003 shutdown for the installation of FINUDA, a strong horizontal multibunch instability was found to limit the positron beam current at the level of ~450 mA. We have performed transverse grow-damp measurements in order to estimate the instability growth rates as well as the feedback damping rates for each bunch at different beam currents and to evaluate the tune shift along the bunch train. In particular, a strong dependence of oscillation amplitudes on the relative position of the bunch in the train has been observed. In this paper we describe the setup for multibunch oscillation amplitude recording, discuss the transverse feedback performance and summarize some observations on the transverse instability. The feedback rises the threshold by about a factor of two, depending on the machine configuration.  
 
THPLT057 An RF Deflector Design for 6d Phase Space Characterization of the Sparc Beam vacuum, antiproton, feedback, radiation 2613
 
  • C. Vaccarezza, D. Alesini
    INFN/LNF, Frascati (Roma)
  • M. Amadei, P. Cascavola, A. Mostacci, L. Palumbo
    Rome University La Sapienza, Roma
  • J. Rosenzweig
    UCLA, Los Angeles, California
  The characterization of the longitudinal and transverse phase space of the beam provided by the SPARC photoinjector is a crucial point to establish the performance quality of the photoinjector itself. By means of an RF deflector and a dispersive system, the six dimensional beam phase space can be analyzed. A five cell SW aluminum prototype of the SPARC RF deflector has been realized and tested. We report in this paper the design issues together with the RF measurement results. The simulation results of the 6D phase space reconstruction of the SPARC beam are also presented.  
 
THPLT058 Commissioning of the OTR Beam Profile Monitor System at TTF/VUV-FEL Injector vacuum, antiproton, feedback, cyclotron 2616
 
  • A. Cianchi, L. Catani, E.C. Chiadroni
    INFN-Roma II, Roma
  • M. Castellano, G. Di Pirro
    INFN/LNF, Frascati (Roma)
  • K. Honkavaara
    DESY, Hamburg
  • M. Raparelli
    Università di Roma II Tor Vergata, Roma
  The TESLA Test Facility (TTF) linac at DESY is being extended to an energy of 1 GeV to drive a new Free Electron Laser facility (VUV-FEL)with wavelengths between 100 nm and 6 nm.Beam profile monitors based on optical transition radiation (OTR) are one of the most important electron beam diagnostics tools. The OTR imaging system is designed to measure the transverse beam size and shape with a resolution down to 10 um. The images are digitized by CCD cameras. A network structure allows a simpler topology to connect the large number of cameras (24).This paper considers the commissioning of the OTR beam profile monitors during the first running period of the injector in spring 2004.  
 
THPLT059 Design Study of a Movable Emittance Meter Device for the SPARC Photoinjector vacuum, antiproton, emittance, feedback 2619
 
  • A. Cianchi, L. Catani
    INFN-Roma II, Roma
  • M. Boscolo, M. Castellano, A. Clozza, G. Di Pirro, M. Ferrario, D. Filippetto, V. Fusco
    INFN/LNF, Frascati (Roma)
  • L. Giannessi, L. Picardi, M. Quattromini, C. Ronsivalle
    ENEA C.R. Frascati, Frascati (Roma)
  Preliminary studies of the SPARC rf gun are planned to obtain an accurate analysis and optimization of the emittance compensation scheme, measuring the beam emittance evolution downstream the RF gun with an appropriate diagnostic system. Since with a space charge dominated beam the use of the quad-scan method is not possible a 1D pepper-pot method will be used. A mask with narrow slits will be mounted on a movable support, spanning a 1.5 m meters region to measure the emittance in several positions and reconstruct its behavior in the post gun section. Numerical simulations of the measurement process, mainly based on PARMELA and TREDI, are used to estimate the achievable accuracy and to optimize the experimental setup. Wake field effects induced by the beam propagation through the long bellows have been also investigated with HOMDYN. Based on these simulations the design of the apparatus, called emittance-meter, has been realized and is under construction at LNF.  
 
THPLT060 An Automatic Beam Characterization Instrument for Proton Therapy Applications vacuum, antiproton, emittance, feedback 2622
 
  • D. Giove, C. De Martinis, M. Mauri
    INFN/LASA, Segrate (MI)
  • C. Cirrone, G. Cuttone
    INFN/LNS, Catania
  The characterization in the transverse plane of the beam is a fundamental step in the design of a proton therapy facility. In this paper we will describe an automatic system able to measure the transverse profiles of the proton beam used in the Catana facility at LNS-Catania. The system has been designed as an autonomous equipment able to acquire optical images of the beam (after an interaction with a converter) and to elaborate them to extract the relevant parameters. The equipment may be interfaced to the rest of the control system of the facility and to the operator interface to provide high level control and monitoring tools. Operational experience will be discussed and the results so far obtained will be outlined.