Author: Ge, L.
Paper Title Page
TUPEA087 Experiment on Multipactor Suppression in Dielectric-loaded Accelerating Structures with a Solenoid Field 1319
  • C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • C. Chang, L. Ge, L. Xiao
    SLAC, Menlo Park, California, USA
  • M.E. Conde, W. Gai, R. Konecny, J.G. Power
    ANL, Argonne, USA
  • S.H. Gold
    NRL, Washington, DC, USA
  Funding: US DoE SBIR Phase I project under contract #DE-SC0007629
Efforts by numerous institutions have been ongoing over the past decade to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external rf source. Multipactor is the major issue limiting the gradient that was revealed in earlier experiments. A theoretical model predicts that the strength of solenoid field within an optimal range applied to DLA structures may completely block the multipactor. To demonstrate this approach, two DLA test structures have been built and the first high power test will be conducted in December 2012. The results will be reported.
WEPWO072 HOM Damping Coupler Design for the 400-MHz RF Dipole Compact Crab Cavity for the LHC HiLumi Upgrade 2468
  • Z. Li, L. Ge
    SLAC, Menlo Park, California, USA
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515.
Crab cavities are adapted as the baseline design for the LHC HiLumi upgrade to achieve head-on beam-beam collisions for further improvement in luminosity. A 400-MHz compact RF dipole crab cavity design was developed by a joint effort between Old Dominion University and SLAC under the support of US LARP program. This design has shown very favorable RF parameters and can fit into the available beamline spacing for either vertical and horizontal crabbing schemes. A niobium prototype cavity based on such a design has been manufactured for vertical test. In addition, there are stringent wakefield requirements that needed to be met for such a cavity in order to preserve the quality of the circulating beams. In this paper, we will discuss different damping schemes for such a compact design and present the HOM coupler designs to meet the damping requirements.
WEPFI073 A Modular Cavity for Muon Ionization Cooling R&D 2860
  • D.L. Bowring, A.J. DeMello, A.R. Lambert, D. Li, S.P. Virostek, M.S. Zisman
    LBNL, Berkeley, California, USA
  • C. Adolphsen, L. Ge, A.A. Haase, K.H. Lee, Z. Li, D.W. Martin
    SLAC, Menlo Park, California, USA
  • D.M. Kaplan
    Illinois Institute of Technology, Chicago, Illinois, USA
  • T.H. Luo, D.J. Summers
    UMiss, University, Mississippi, USA
  • A. Moretti, M.A. Palmer, R.J. Pasquinelli, Y. Torun
    Fermilab, Batavia, USA
  • R.B. Palmer
    BNL, Upton, Long Island, New York, USA
  The Muon Accelerator Program (MAP) collaboration is developing an ionization cooling channel for muon beams. Ionization cooling channel designs call for the operation of high-gradient, normal-conducting RF cavities in multi-Tesla solenoidal magnetic fields. However, strong magnetic fields have been shown to limit the maximum achievable gradient in RF cavities. This gradient limit is characterized by RF breakdown and damage to the cavity surface. To study this issue, we have developed an experimental program based on a modular pillbox cavity operating at 805 MHz. The modular cavity design allows for the evaluation of different cavity materials - such as beryllium - which may ameliorate or circumvent RF breakdown triggers. Modular cavity components may furthermore be prepared with different surface treatments, such as high-temperature baking or chemical polishing. This poster presents the design and experimental status of the modular cavity, as well as future plans for the experimental program.  
WEPFI092 Multipacting Simulation of the MICE 201 MHz RF Cavity 2914
  • T.H. Luo, D.J. Summers
    UMiss, University, Mississippi, USA
  • D.L. Bowring, A.J. DeMello, D. Li, P. Pan, S.P. Virostek
    LBNL, Berkeley, California, USA
  • L. Ge
    SLAC, Menlo Park, California, USA
  The international Muon Ionization Cooling Experiment (MICE) aims to demonstrate transverse cooling of muon beams by ionization. The MICE ionization cooling channel requires eight 201-MHz normal conducting RF cavities to compensate for the longitudinal beam energy loss in the cooling channel. Multipacting is a resonant electron discharge produced by the synchronization of emitted electrons with the RF fields, which can cause breakdown at high power RF operation. In this paper, we present the study of the multipacting effect in the MICE 201 MHz cavities with the SLAC ACE3P code. The simulation is carried out in the cavity body, the RF coupler region, and the coaxial waveguide, with the external magnetic field from the Coupling Coil. We will identify potential RF breakdowns due to multipacting and propose a solution to suppress them.