03 Linear Colliders, Lepton Accelerators and New Acceleration Techniques

T02 Lepton Sources

Paper Title Page
MOPP069 A Prototype Target Wheel for the ILC Positron Source 706
 
  • I. R. Bailey, L. J. Jenner, C. J. Nelson
    Liverpool University, Science Faculty, Liverpool
  • I. R. Bailey
    Cockcroft Institute, Warrington, Cheshire
  • D. G. Clarke, K. P. Davies, A. Gallagher
    STFC/DL, Daresbury, Warrington, Cheshire
  • J. A. Clarke
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • J. Gronberg, L. B. Hagler, W. T. Piggott
    LLNL, Livermore, California
 
  In this paper we describe the design, construction and commissioning of a prototype based on the positron production target wheel planned for the ILC positron source. The efficiency of the current baseline positron source design for the ILC can be improved if the conversion target is partially immersed in the magnetic field of the capture optics, thereby increasing the overall capture efficiency for positrons by a factor of two or more. However, immersion of the rotating target wheel generates strong eddy currents leading to additional heating and stresses on the wheel. The primary purpose of our prototype, which had been assembled at Daresbury Laboratory, is to investigate the effects of eddy currents induced in a titanium alloy wheel moving with rim speeds up to 100 metres per second in magnetic fields of the order of 1 Tesla.  
MOPP070 Construction of a Full Scale Superconducting Undulator Module for the International Linear Collider Positron Source 709
 
  • J. A. Clarke, O. B. Malyshev, D. J. Scott, B. J.A. Shepherd
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • I. R. Bailey, J. B. Dainton, K. M. Hock, L. J. Jenner, L. I. Malysheva, L. Zang
    Liverpool University, Science Faculty, Liverpool
  • E. Baynham, T. W. Bradshaw, A. J. Brummitt, F. S. Carr, A. J. Lintern, J. Rochford
    STFC/RAL, Chilton, Didcot, Oxon
  • A. Bungau
    UMAN, Manchester
  • N. A. Collomb
    STFC/DL, Daresbury, Warrington, Cheshire
  • A. F. Hartin
    OXFORDphysics, Oxford, Oxon
  • S. Hesselbach, G. A. Moortgat-Pick
    Durham University, Durham
  • Y. Ivanyushenkov
    ANL, Argonne, Illinois
  • N. C. Ryder
    University of Bristol, Bristol
 
  The positron source for the ILC is dependent upon a >200m long undulator to generate a high flux of multi-MeV photons. The undulator system is broken down into a series of 4m cryomodules, which each contain two superconducting helical undulators. Following a dedicated R&D phase and the construction and measurement of a number of short prototypes a full scale cryomodule has now been completed for the first time. This paper reports on the design, manufacture, and test results of this cryomodule.  
MOPP071 Intense Stopping Muon Beams 712
 
  • M. A.C. Cummings, R. J. Abrams, R. P. Johnson, C. Y. Yoshikawa
    Muons, Inc, Batavia
  • C. M. Ankenbrandt, M. A. Martens, D. V. Neuffer, K. Yonehara
    Fermilab, Batavia, Illinois
 
  The study of rare processes using stopping muon beams provides access to new physics that cannot be addressed at energy frontier machines. The flux of muons into a small stopping target is limited by the kinematics of the production process and by stochastic processes in the material used to slow the particles. Innovative muon beam cooling techniques are being applied to the design of stopping muon beams in order to increase the event rates in such experiments. Such intense stopping beams will also aid the development of applications such as muon spin resonance and muon-catalyzed fusion.  
MOPP072 A Study of Mechanical and Magnetic Issues for a Prototype Positron Source Target 715
 
  • L. J. Jenner, I. R. Bailey
    Cockcroft Institute, Warrington, Cheshire
  • D. G. Clarke, K. P. Davies, A. Gallagher
    STFC/DL, Daresbury, Warrington, Cheshire
  • J. A. Clarke
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • J. Gronberg, L. B. Hagler, W. T. Piggott
    LLNL, Livermore, California
  • S. Hesselbach
    Durham University, Durham
  • C. J. Nelson
    STFC/RAL, Chilton, Didcot, Oxon
  • J. Rochford
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
 
  In order to construct a high yield, positron source that can meet the intensity requirements of future facilities, a robust conversion target is needed. One solution is to use a rotating titanium alloy wheel upon which a beam of photons is incident. The efficiency of capturing the resulting positrons can be optimised by immersing this system in a magnetic field. As described elsewhere*, a prototype of such a target has been built at Daresbury Laboratory, to investigate the mechanical challenges associated with its construction and to study the magnetic effects that the wheel will experience. In this paper, calibration of the instrumentation, the data acquisition system and the initial results from operating the wheel in a strong magnetic field are described. Such phenomena as the eddy current heating experienced by the wheel are measured and compared to results from modelling codes. Vibrational issues surrounding the wheel and supporting structure at various speeds are studied.

*ID: 3894 A Prototype Target Wheel for the ILC Positron Source

 
MOPP073 Plasma Lens for Muon and Neutrino Beams 718
 
  • S. A. Kahn, S. Korenev
    Muons, Inc, Batavia
  • M. B. Bishai, M. Diwan, J. C. Gallardo, A. Hershcovitch, B. M. Johnson
    BNL, Upton, Long Island, New York
 
  The plasma lens is examined as an alternate to focusing horns and solenoids for use in a neutrino or muon beam facility. The plasma lens concept is based on a combined high current lens/target configuration. The current is fed at electrodes located upstream and downstream form the target where pion capturing is needed. The current flows primarily in the plasma, which has a lower resistivity than the target. A second plasma lens section, with an additional current feed, follows the target to provide shaping of the plasma for optimum focusing. The plasma lens is immersed in an additional solenoidal magnetic field to facilitate the plasma stability. The geometry of the plasma is shaped to provide optimal pion capture. Simulations of this plasma lens system have shown a 25% higher neutrino production than the horn system. Plasma lenses have additional advantages: larger axial currents than horns, minimal neutrino contamination during antineutrino running, and negligible pion absorption or scattering. Results from particle simulations using plasma lens will be presented.  
MOPP074 Improvement of an S-band RF-gun cavity with a Cs-Te Photo-cathode 721
 
  • A. Murata, Y. Hama, T. Hirose, Y. Kato, K. Sakaue, T. Suzuki, M. Washio
    RISE, Tokyo
  • H. Hayano, N. Kudoh, T. T. Takatomi, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • Y. Kamiya
    University of Tokyo, Tokyo
  • S. Kashiwagi
    ISIR, Osaka
  • M. Kuriki
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima
  • R. Kuroda
    AIST, Tsukuba, Ibaraki
 
  A 1.6cell S-band photo-cathode RF-Gun is one of the good alternatives of the short pulse electron source. Therefore,we are operating as a high brightness short pulse electron source for studying a reaction of radiation chemistry,an inverse Compton scattering at Waseda University and as an injector at KEK-ATF. To improve an electron beam quality and to reduce a dark current,we decided to improve the RF-Gun cavity. Frequency tuning of the half cell of existing RF-gun was performed by the torque control of Helicoflex seal on the cathode plate and two moving rod type tuners were installed on the full cell. Newly designed RF-Gun cavity has four compact tuners on each cell,which can be tune the frequency to deform the cavity wall,to remove the Helicoflex seal and tuning holes that were considered to be the major cause of electric discharge and/or a dark current source. According to these improvements,the Q-value and shunt impedance of the cavity is 30% larger than that of existing guns. As the result,the reduction of dark current is succeeded and the beam energy is reached up to 5.5MeV at 10MW RF input. The detailed results of electron beam generation will be reported at the conference.  
MOPP075 Experimental Generation and Characterization of Uniformly Filled Ellipsoidal Electron Beam Distributions 724
 
  • P. Musumeci, J. Moody, J. B. Rosenzweig, C. M. Scoby
    UCLA, Los Angeles, California
 
  For forty years, uniformly filled ellipsoidal beam distributions have been studied theoretically, as they have had the promise of generating self-fields that produce forces linear in the coordinate offset in all three directions. More recently, a scheme for producing such distributions, which depends on the strong longitudinal expansion of an initially very short beam under its own space charge forces, has been proposed. Here we present the experimental demonstration of this scheme, obtained by illuminating the cathode in an rf photogun with an ultra-short laser pulse (~35 fs rms) with an appropriate transverse profile. The resulting 4 MeV beam spatiotemporal (x,t) distribution is imaged using an rf deflecting cavity with 50 fsec resolution. A temporal asymmetry in the ellipsoidal profile, due to image charge effects at the photocathode, is observed at higher charge operation. This distortion is also found to degrade the transverse beam quality.  
MOPP076 L-Band RF Gun with a Thermionic Cathode 727
 
  • S. Nagaitsev, R. Andrews, M. Church, A. Lunin, O. A. Nezhevenko, N. Solyak, D. Sun, V. P. Yakovlev
    Fermilab, Batavia, Illinois
 
  In this talk we present a design for an L-band (1.3 GHz) rf gun with a two-grid thermionic cathode assembly. The rf gun is design to provide a 10-mA average beam current for 1ms at 5 Hz. These parameters match the requirements of both the ILC and Fermilab Project X test facilities. In our simulations we are able to attain the bunch length at 20-30 degrees (FW), while the output energy can vary 2-4 MeV. We will present the results of our simulations as well as preliminary designs.  
MOPP078 Femtosecond Photocathode Electron Source 730
 
  • J. Yang, K. Kan, T. Kondoh, K. Tanimura, Y. Yoshida
    ISIR, Osaka
  • J. Urakawa
    KEK, Ibaraki
 
  A photocathode-based low-emittance femtosecond-bunch electron source is developed to reveal the hidden dynamics of intricate molecular and atomic processes in materials through experimentation such as time-resolved pulse radiolysis or time-resolved electron diffraction. The transverse and longitudinal dynamics of femtosecond electron beam in a photocathode rf gun were studied. The growths of the emittance, bunch length and energy spread due to the rf and the space charge effects in the rf gun were investigated by changing the laser injection phase, the laser pulse width and the bunch charge. The beam simulation indicates that a sub-100-fs MeV electron source with the normalized transverse emittance of 0.1 mm-mrad and the relative energy spread of 10-4 at bunch charge of 0.1-1pC is achievable in the photocathode rf gun driven by a femtosecond laser light.  
MOPP079 Studies on the Role of a Photon Collimator for the ILC Positron Source 733
 
  • L. Zang
    Cockcroft Institute, Warrington, Cheshire
  • I. R. Bailey, A. Wolski, L. Zang
    Liverpool University, Science Faculty, Liverpool
 
  Use of a helical undulator in the ILC positron source provides the possibility of producing a polarised positron beam. The degree of polarisation of the positrons depends upon the polarisation of the photons produced from the undulator, where the polarisation depends on the photon energy and production angle. We calculate these quantities for one design of the helical undulator for the ILC, investigate approximations commonly made in calculating the undulator photon spectrum and explore the role of of a photon collimator in determining the positron polarisation.  
WEOBG03 The Design of the Positron Source for the International Linear Collider 1915
 
  • J. A. Clarke, O. B. Malyshev, D. J. Scott
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • I. R. Bailey, J. B. Dainton, K. M. Hock, L. J. Jenner, L. I. Malysheva, L. Zang
    Liverpool University, Science Faculty, Liverpool
  • E. Baynham, T. W. Bradshaw, A. J. Brummitt, F. S. Carr, A. J. Lintern, J. Rochford
    STFC/RAL, Chilton, Didcot, Oxon
  • V. Bharadwaj, J. Sheppard
    SLAC, Menlo Park, California
  • A. Bungau
    UMAN, Manchester
  • N. A. Collomb
    STFC/DL, Daresbury, Warrington, Cheshire
  • R. Dollan
    Humboldt Universität zu Berlin, Berlin
  • W. Gai, Y. Ivanyushenkov, W. Liu
    ANL, Argonne, Illinois
  • J. Gronberg, W. T. Piggott
    LLNL, Livermore, California
  • A. F. Hartin
    OXFORDphysics, Oxford, Oxon
  • S. Hesselbach, G. A. Moortgat-Pick
    Durham University, Durham
  • K. Laihem, S. Riemann, A. Schaelicke, A. Ushakov
    DESY Zeuthen, Zeuthen
  • T. Lohse
    Humboldt University Berlin, Institut für Physik, Berlin
  • A. A. Mikhailichenko
    Cornell University, Department of Physics, Ithaca, New York
  • N. C. Ryder
    University of Bristol, Bristol
 
  The high luminosity requirements and the option of a polarized positron beam present a great challenge for the positron source of a future linear collider. This paper provides a comprehensive overview of the latest proposed design for the baseline positron source of the International Linear Collider. We report on recent progress and results concerning the main components of the source: including the undulator, collimators, capture optics, and target.  
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WEOBG04 First Experimental Results from DEGAS, the Quantum Limited Brightness Electron Source 1918
 
  • M. S. Zolotorev, J. W. ONeill, F. Sannibale, W. Wan
    LBNL, Berkeley, California
  • E. D. Commins, A. S. Tremsin
    UCB, Berkeley, California
 
  The construction of DEGAS (DEGenerate Advanced Source), a proof of principle for a quantum limited brightness electron source, has been completed at the Lawrence Berkeley National Laboratory. The commissioning and the characterization of this source, designed to generate coherent low energy (10-100 eV) single electron "bunches" with brightness approaching the quantum limit at a repetition rate of few MHz, has been started. In this paper the first experimental results are described.  
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