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Li, D.

Paper Title Page
MOPP080 Studies of Breakdown in a Pressurized RF Cavity 736
 
  • M. BastaniNejad, A. A. Elmustafa
    Old Dominion University, Norfolk, Virginia
  • M. Alsharo'a, P. M. Hanlet, R. P. Johnson, S. Korenev, M. Kuchnir, D. J. Newsham, R. Sah
    Muons, Inc, Batavia
  • C. M. Ankenbrandt, A. Moretti, M. Popovic, K. Yonehara
    Fermilab, Batavia, Illinois
  • D. M. Kaplan
    Illinois Institute of Technology, Chicago, Illinois
  • D. Li
    LBNL, Berkeley, California
  • D. Rose, C. H. Thoma, D. R. Welch
    Voss Scientific, Albuquerque, New Mexico
 
  Previous studies of RF breakdown in a cavity pressurized with dense hydrogen gas have indicated that breakdown probability is proportional to a high power of the surface electromagnetic field. This behavior is similar to the Fowler-Nordheim description of electron emission from a cold cathode, and it implies that breakdown is a quantum mechanical effect that is characterized by the work function of the cavity metal. We describe our present efforts to measure the distributions of work functions at the nanoscale level on the surfaces of the electrodes used in breakdown studies, and to understand how the RF conditioning process affects them.  
MOPP098 A 201-MHz Normal Conducting RF Cavity for the International MICE Experiment 784
 
  • D. Li, A. J. DeMello, S. P. Virostek, M. S. Zisman
    LBNL, Berkeley, California
  • R. A. Rimmer
    Jefferson Lab, Newport News, Virginia
 
  MICE is a demonstration experiment for the ionization cooling of muon beams. Eight RF cavities are proposed to be used in the MICE cooling channel. These cavities will be operated in a strong magnetic field; therefore, they must be normal conducting. The cavity design and construction are based on the successful experience and techniques developed for a 201-MHz prototype cavity for the US MUCOOL program. Taking advantage of a muon beam’s penetration property, the cavity employs a pair of curved thin beryllium windows to terminate conventional beam irises and achieve higher cavity shunt impedance. The cavity resembles a round, closed pillbox cavity. Two half-shells spun from copper sheets are joined by e-beam welding to form the cavity body. There are four ports on the cavity equator for RF couplers, vacuum pumping and field probes. The ports are formed by means of an extruding technique.  
MOPP155 Superconducting RF Deflecting Cavity Design and Prototype for Short X-ray Pulse Generation 913
 
  • J. Shi, H. Chen, C.-X. Tang
    TUB, Beijing
  • G. Cheng, G. Ciovati, P. Kneisel, R. A. Rimmer, G. Slack, L. Turlington, H. Wang
    Jefferson Lab, Newport News, Virginia
  • D. Li
    LBNL, Berkeley, California
  • A. Nassiri, G. J. Waldschmidt
    ANL, Argonne, Illinois
 
  Deflecting RF cavities are proposed to be used in generating short x-ray pulses (on ~1-picosecond order) at the Advanced Photon Source (APS) at Argonne National Laboratory (ANL)* using a novel scheme by Zholents**. To meet the required deflecting voltage, impedance budget from higher order, lower order and the same order modes (HOM, LOM and SOM) of the APS storage ring, extensive deflecting cavity design studies have been conducted with numerical simulations and cavity prototypes. In this paper, we report recent progress on a single cell S-band (2.8-GHz) superconducting deflecting cavity design with waveguide damping. A copper and a niobium prototype cavity were fabricated and tested, respectively to benchmark the cavity and damping designs. A new damping scheme has been proposed which provides stronger damping to both HOM and LOM by directly coupling to a damping waveguide on the cavity equator.

* A. Nassiri, private communication, 2007
** A. Zholents et al. NIM, 1999, A425:385-389.

 
MOPP156 Fabrication and Low Power Testing of an L-band Deflecting Cavity for Emittance-exchange at ANL 916
 
  • J. Shi, H. Chen, W.-H. Huang, C.-X. Tang, D. Tong
    TUB, Beijing
  • W. Gai, C.-J. Jing, K.-J. Kim, J. G. Power
    ANL, Argonne, Illinois
  • D. Li
    LBNL, Berkeley, California
 
  An L-Band RF deflecting cavity has been built at Tsinghua University for a planned transverse-to-longitudinal emittance exchange experiment at Argonne National Laboratory (ANL). The deflector is a 1.3-GHz, 3-cell cavity operated in a TM110-like mode that delivers a deflecting voltage of 3.4 MV. In this paper, we review the cavity design and present detail of the fabrication, cold testing and tuning progress. Cell radii were left undercut to account for simulation errors, which yielded a higher frequency in the first bench measurement but removed by the final tuning on the lathe. Field distribution on axis was measured using the ‘‘bead-pull'' method and tuned to balance in the 3 cells.