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Hirshfield, J.L.

Paper Title Page
TPAE012 Rectangular Diamond-Lined Accelerator Structure 1282
 
  • C. Wang, V.P. Yakovlev
    Omega-P, Inc., New Haven, Connecticut
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT
 
  Funding: Work supported by U.S. DOE.

For high frequency accelerators with normal-conducting structures studied by the NLC/GLC collaboration and the CLIC group, rf breakdown is the main gradient limitation. In this paper, a Ka-band rectangular dielectric-lined structure is described as an attempt to increase accelerating gradient beyond the limits suitable for metallic structures. The structure is based on amorphous dielectrics that are known to exhibit high breakdown limits (~ GV/m). An example is artificial diamond that has already been successfully used on an industrial basis for large-diameter output windows of high power gyrotrons, and is produced industrially in increasing quantities. Artificial diamond has low loss tangent, moderate dielectric constant and high breakdown limit of ~2 GV/m. In the proposed structure diamond-slabs are employed to support high-gradient acceleration fields. Interposition of vacuum gaps between the dielectric slabs and the side walls is shown to reduce Ohmic losses substantially, leading to an increase in shunt impedance and reduced susceptibility to rf breakdown and fatigue on metal surfaces.

 
TPAE013 Rectangular Dielectric-Lined Two-Beam Wakefield Accelerator Structure 1333
 
  • C. Wang, V.P. Yakovlev
    Omega-P, Inc., New Haven, Connecticut
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT
  • T.C. Marshall
    Columbia University, New York
 
  Funding: Work supported by U.S. DOE.

A novel dielectric structure is described for a two-beam wake field accelerator (WFA), which consists of three or four rectangular dielectric slabs positioned within a rectangular conducting pipe. This structure can be thought of as equivalent to two symmetric dielectric-lined three-zone rectangular waveguides, joined side-by-side. The design mode in the two-beam structure is the LSM-31 mode, a combination of two symmetric LSM-11 modes of the two three-zone waveguides. This two-channel mode can be employed to decelerate drive particles in one channel and accelerate test particles in the other. It is possible to find structure parameters that give a high ratio of acceleration gradient for the test beam, to deceleration gradient for the drive beam, of the order of 100.

 
TPAE063 Observation of Superposition of Wake Fields Generated by Electron Bunches in a Dielectric-Lined Waveguide 3609
 
  • S.V. Shchelkunov, T.C. Marshall
    Columbia University, New York
  • M. Babzien
    BNL, Upton, Long Island, New York
  • J.L. Hirshfield, M.A. LaPointe
    Yale University, Physics Department, New Haven, CT
 
  Funding: Research supported by the Department of Energy, Division of High Energy Physics.

We report results from an experiment, done at the Accelerator Test Facility, Brookhaven National Laboratory, which demonstrates the successful superposition of wake fields excited by 50MeV bunches which travel ~50cm along the axis of a cylindrical waveguide which is lined with alumina. Wake fields from two short (5-6psec) 0.15-0.35nC bunches are superimposed and the energy losses of each bunch are measured as the separation between the bunches is varied so as to encompass approximately one wake field period (~21cm). A spectrum of 40 TM0m eigenmodes is excited by the bunch. A substantial retarding wake field (2.65MV/m×nC for just the first bunch) is developed because of the short bunches and the narrow vacuum channel diameter (3mm) through which they move. The energy loss of the second bunch exhibits a narrow resonance with a 4mm (13.5psec) footprint. This experiment may be compared with a related experiment reported by a group at the Argonne National Laboratory where a much weaker wake field (~0.1MV/m×nC for the first bunch) having ~10 eigenmodes was excited by a train of much longer bunches,* and the bunch spacing was not varied.

*J. G. Power, M. E. Conde, W. Gai, R. Konecny, and P. Schoessow, Phys. Rev. ST Accel. Beams 3, 101302 (2000).

 
WPAT026 Status of 34 GHZ, 45 MW Pulsed Magnicon 1922
 
  • O.A. Nezhevenko, V.P. Yakovlev
    Omega-P, Inc., New Haven, Connecticut
  • J.L. Hirshfield, M.A. LaPointe
    Yale University, Physics Department, New Haven, CT
  • E.V. Kozyrev
    BINP SB RAS, Novosibirsk
  • S.V. Shchelkunov
    Columbia University, New York
 
  Funding: Research supported by the Department of Energy, Division of High Energy Physics.

A high efficiency, high power magnicon at 34.272 GHz has been designed and built as a microwave source to develop RF technology for a future multi-TeV electron-positron linear collider. To develop this technology, this new RF source is being perfected for necessary tests of accelerating structures, RF pulse compressors, RF components, and to determine limits of breakdown and metal fatigue. After preliminary RF conditioning the magnicon produced an output power of 10.5 MW in 0.25 microsecond pulses, with a gain of 54 dB. The new results of the experimental tests after the tube conditioning was resumed are presented in the paper.

 
WPAT027 Recent Results from the X-Band Pulsed Magnicon Amplifier 1979
 
  • O.A. Nezhevenko, V.P. Yakovlev
    Omega-P, Inc., New Haven, Connecticut
  • A.W. Fliflet, S.H. Gold
    NRL, Washington, DC
  • J.L. Hirshfield, M.A. LaPointe
    Yale University, Physics Department, New Haven, CT
  • A.K. Kinkead
    ,
 
  Funding: Research supported by the Department of Energy, Office of High Energy Physics, and the Office of Naval Research.

A frequency-doubling magnicon amplifier at 11.4 GHz has been designed and built as the prototype of an alternative microwave source for the Next Linear Collider project, and to test high power RF components and accelerating structures. The tube is designed to produce ~60 MW, ~1.2 microsecond pulses at 58% efficiency and 59 dB gain, using a 470 kV, 220 A, 2 mm-diameter beam. In the first tests the output power was limited to a level of 26 MW in a 200 nsec pulse. This limitation was caused by the oscillations in the tube collector. Experimental results of the magnicon tests with the new collector are presented in this paper

 
WPAT028 High Power Ferrolelectric Switches at Centimeter and Millimeter Wavelengths 2056
 
  • V.P. Yakovlev, O.A. Nezhevenko
    Omega-P, Inc., New Haven, Connecticut
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT
 
  Funding: Research supported by the Department of Energy, Division of High Energy Physics.

High-power ultra-fast, electrically-controlled switches based on ferroelectric elements for accelerator applications in the centimeter and millimeter wavelength ranges are discussed. Examples of fast switches and phase shifters for pulse compression and power distribution systems at X– and Ka- band are presented. It is shown that such proposed switch designs based on modern ferroelectric materials allow the generation of pulsed power of hundreds of MW’s in both the centimeter and millimeter wave ranges.