MOPB  —  Sources and Injectors   (16-May-05   13:50—17:20)

Chair: R.L. Sheffield, LANL, Los Alamos, New Mexico

Paper Title Page
MOPB001 An 8 GeV Superconducting Injector Linac
  • G.W. Foster
    Fermilab, Batavia, Illinois
  Funding: U.S. Department of Energy, Office of Science.

The Fermilab Proton Driver is an 8 GeV Superconducting H- injector linac which replaces both the Fermilab 8 GeV Booster Synchrotron and its injector linac. In addition to its primary mission of enabling 2 MW beam power at 120 GeV for the Fermilab Main Injector neutrino program, it also provides stand alone beam power of 0.5-2 MW at 8 GeV for a variety of physics goals. The main linac from 1.3-8 GeV uses 1300 MHz TESLA klystrons and cryomodules, and thus represents a ~1.5% system test of the Linear Collider. The front end linac uses a combination of 1300 MHz beta<1 eliptical cavities and 325 MHz spoke resonators. By extending the TESLA technique of driving many superconducting cavities from a single large klystron, the 8 GeV linac requires only 11 klystrons. This has required the development of fast, high power YIG-ferrite phase shifters to provide individual RF phase and amplitude control at each cavity. Using this technique, the linac up to 100 MeV is powered by a single JPARC/Toshiba 325 MHz 2.5 MW Klystron. Proton Driver project status will be discussed in light of recent program developments at Fermilab.

MOPB002 High Intensity High Charge State ECR Ion Sources 179
  • D. Leitner, C.M. Lyneis
    LBNL, Berkeley, California
  Funding: This work was supported by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Nuclear Physics Division of the U.S. Department of Energy under Contract DE AC03-76SF00098.

The next-generation heavy ion beam accelerators such as the proposed Rare Isotope Accelerator (RIA), the Radioactive Ion Beam Factory at RIKEN, the GSI upgrade project, the LHC-upgrade, and IMP in Lanzhou require a great variety of high charge state ion beams with a magnitude higher beam intensity than currently achievable. High performance Electron Cyclotron Resonance (ECR) ion sources can provide the flexibility since they can routinely produce beams from hydrogen to uranium. Over the last three decades, ECR ion sources have continued improving the available ion beam intensities by increasing the magnetic fields and ECR heating frequencies to enhance the confinement and the plasma density. With advances in superconducting magnet technology, a new generation of high field superconducting sources is now emerging, designed to meet the requirements of these next generation accelerator projects. The talk will briefly review the field of high performance ECR ion sources and the latest developments for high intensity ion beam production. The currently most advanced next-generation superconducting source ECR ion source VENUS will be described in more detail.

MOPB003 Progress with the 2Q-LEBT Facility for the RIA Project 253
  • N. Vinogradov, V.N. Aseev, M.R.L. Kern, P.N. Ostroumov, R.C. Pardo, R.H. Scott
    ANL, Argonne, Illinois
  Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. W-31-109-ENG-38.

The Rare Isotope Accelerator (RIA) facility utilizes the concept of simultaneous acceleration of two charge states from the ion source. We are building a prototype two charge-state (2Q) injector of the RIA Driver Linac, which includes an ECR ion source originally built by Berkeley Ion Equipment Corporation, a LEBT and one-segment of the prototype RFQ. The reassembly and commissioning of the ECR source has been completed. During the commissioning process we modified and replaced several major components of the BIE-100 to increase the source performance. A new diagnostic station has been designed and built for accurate measurements of the output beam emittance. The paper will discuss detailed beam dynamics studies together with extensive emittance measurements of various ion beams. The status of the design and fabrication of 100 kV high voltage platform, achromatic bending system, multi-harmonic buncher, and a full power 57.5 MHz RFQ segment will be presented.

MOPB004 Progress on Test EBIS and the Design of an EBIS-Based RHIC Preinjector 363
  • J.G. Alessi, E.N. Beebe, O. Gould, A. Kponou, R. Lockey, A.I. Pikin, K. Prelec, D. Raparia, J. Ritter, L. Snydstrup
    BNL, Upton, Long Island, New York
  Funding: Work supported under the auspices of the U.S. DOE.

Following the successful development of the Test EBIS at BNL,* we now have a design for an EBIS-based heavy ion preinjector which would serve as an alternative to the Tandem Van de Graaffs in providing beams for RHIC and the NASA Space Radiation Laboratory. This baseline design includes an EBIS producing mA-level currents of heavy ions (ex. Au 32+) in ~ 10-20 microsecond pulses, injecting into an RFQ which accelerates the beams to 300 keV/amu, followed by an IH linac accelerating to 2 MeV/amu. Some details of this design will be presented, as well recent experimental results on the Test EBIS.

*E.N. Beebe et al., Proc. Ninth International Symposium on Electron Beam Ion Sources and Traps, Journal of Physics: Conference Series 2 (2004) 164–173.

MOPB005 Advances in the Performance of the SNS Ion Source 472
  • R.F. Welton, S.N. Murray, M.P. Stockli
    ORNL, Oak Ridge, Tennessee
  • R. Keller
    LBNL, Berkeley, California
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.

The ion source developed for the Spallation Neutron Source* (SNS) is a radio frequency, multi-cusp source designed to produce ~ 40 mA of H- with a normalized rms emittance of less than 0.2 pi mm mrad. To date the source has been utilized in the commissioning of the SNS accelerator, delivering beams of 10-50 mA with duty-factors of typically ~0.1% for operational periods of several weeks and availabilities now ~99%. Ultimately the SNS facility will require beam duty-factors of 6% (1 ms pulse length, 60 Hz repetition rate, 21 day run-period). Over the last year, several experiments were performed in which the ion source was continuously operated at full duty-factor and maximum beam current on a dedicated test stand. Recently, a breakthrough in our understanding of the Cs release process has led to the development of a new source conditioning technique which resulted in a dramatic increase in beam persistence with time. Average H- beam attenuation rates have been improved from ~5 mA/day to ~0.4 mA/day, allowing beams in excess of 30 mA to be delivered continuously at full duty factor for periods of ~20 days. Prior to this development, full duty factor beams could only be sustained for periods of several hours.

MOPB006 Frontiers of RF Photoinjectors 530
  • M. Ferrario
    INFN/LNF, Frascati (Roma)
  New ideas have been recently proposed to achieve ultra-high brightness electron beams, as particularly needed in SASE-FEL experiments, and to produce flat beams, as required in linear colliders. Low emittance schemes already foreseen for split normal conducting photoinjectors have been applied to the superconducting case in order to produce high peak and high average beam brightness. RF compressor techniques have been partially confirmed by experimental results and more compact RF photoinjector designs including compression scheme are under development. Research and experiments in the flat beam production from a photoinjector as a possible alternative to damping rings are in progress. An overview of recent advancements and future perspectives in photoinjector beam physics is reported in this talk.  
MOPB007 Future Directions in Electron Sources 563
  • J.W. Lewellen
    ANL, Argonne, Illinois
  Funding: Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

The emittance-compensated rf photoinjector is in the process of evolving from an experiment in and of itself, to a laboratory instrument, to a workhorse component of large user facilities such as next-generation light sources. In recent years the performance achieved by the standard p-mode design has approached the levels predicted by theory and experiment. The basic design has been scaled from X-band down to less than 1 GHz in terms of operating frequency, and superconducting designs are presently undergoing initial testing at various locations. The requirements for linac-based light sources will require at least one order of magnitude improvement in beam quality; other applications, such as electron microscopes or high-energy electron lithography, require still greater improvements. The migration towards fully superconducting accelerators provides some additional design challenges. This paper briefly presents requirements for some future applications, and presents four new approaches to extending injector performance: the diamond-emitter photocathode, the planar focusing cathode, the magnetic-mode emittance compensation technique, and the field-emission-gated cathode.

MOPB008 Temporal E-Beam Shaping in an S-Band Accelerator 642
  • H. Loos, D. Dowell, A. Gilevich, C. Limborg-Deprey
    SLAC, Menlo Park, California
  • M. Boscolo, M. Ferrario, M. Petrarca, C. Vicario
    INFN/LNF, Frascati (Roma)
  • J.B. Murphy, B. Sheehy, Y. Shen, T. Tsang, X.J. Wang, Z. Wu
    BNL, Upton, Long Island, New York
  • L. Serafini
    INFN-Milano, Milano
  Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contracts DE-AC02-98CH10886 and DE-AC03-76SF00515.

New short-wavelength SASE light sources will require very bright electron beams, brighter in some cases than is now possible. One method for improving brightness involves the careful shaping of the electron bunch to control the degrading effects of its space charge forces. We study this experimentally in an S-band system, by using an acousto-optical programmable dispersive filter to shape the photocathode laser pulse that drives the RF photoinjector. We report on the efficacy of shaping from the IR through the UV, and the effects of shaping on the electron beam dynamics.

MOPB009 Review of the Production Process of TTF and PITZ Photocathodes 671
  • D. Sertore, P. Michelato, L. Monaco
    INFN/LASA, Segrate (MI)
  • A. Bonucci
    SAES Getters S.p.A., Lainate
  • J.H. Han
    DESY Zeuthen, Zeuthen
  • S. Schreiber
    DESY, Hamburg
  In the present article, the production process of the photocathodes for the TESLA Test Facility (TTF) at DESY Hamburg and the Photo Injector Test Facility at DESY-Zeuthen (PITZ) is reviewed in order to highlight key elements for the final photocathode performances. Since the first photocathode production in 1998, we have continuosly collected relevant paramenters of the cathode plugs and deposition process. These data are now critically analized in view of an optimization of the photocathode performances for the next generation of high brilliance sources.  
MOPB010 Simulations and Experiments of Electron Beams Pre-Modulated at the Photocathode 704
  • J.G. Neumann, R.B. Fiorito, P.G. O'Shea
    IREAP, College Park, Maryland
  • G.L. Carr, T.V. Shaftan, B. Sheehy, Y. Shen, Z. Wu
    BNL, Upton, Long Island, New York
  • W. Graves
    MIT, Middleton, Massachusetts
  • H. Loos
    SLAC, Menlo Park, California
  Funding: Work is supported by the Office of Naval Research, the Joint Technology Office, and the Department of Energy.

The University of Maryland and the Source Development Laboratory at Brookhaven National Laboratory have been collaborating on a project that explores the use of electron beam pre-modulation at the cathode to control the longitudinal structure of the electron beam. This technique could be applied to creating deliberate modulations which can lead to the generation of terahertz radiation, or creating a smooth profile in order to supress radiation. This paper focuses on simulations that explore some of the pre-modulated cases achieved experimentally.

MOPB011 Axial RF Power Input in Photocathode Electron Guns 743
  • D. Janssen
    FZR, Dresden
  • H. Bluem, A.M.M. Todd
    AES, Princeton, New Jersey
  • V. Volkov
    BINP SB RAS, Novosibirsk
  We discuss the coaxial power input in normal and superconducting RF (SRF)photoinjector cavities. Upstream coaxial power input has been previously used at the PITZ facility where the output beam tube is an intrinsic part of the coaxial transmission line into the gun. In this paper, we describe coaxial coupling from the cathode side of the gun. For normal conducting RF guns, in addition to the advantage from symmetric coupling, an emittance compensation solenoid can now be positioned close to the gun cavity to deliver optimal transverse emittance. Beam dynamics calculations demonstrate 0.8 mm-mrad at 1 nC in X-band. For an SRF gun, we present a design for coaxial input around the cathode using a superconducting coupling cell. This cell matches the external quality factor of the gun for different beam powers and there is no RF loss associated with the axial gap of the cathode. The heat input into the coaxial feed and the surface field of the coupler are discussed. For a 1.3 GHz half-cell gun cavity with stored energy of 6.6 J, a 2.5 MeV electron beam can be delivered with a peak accelerating field of 50 MV/m. At 10 mA,the external Q is 2.1 x 106 and the coaxial line power loss that must be cooled is 28 W.