Author: Thoma, C.H.
Paper Title Page
THPPC028 Kinetic Modeling of RF Breakdown in High-Pressure Gas-filled Cavities 3341
  • D. Rose, C.H. Thoma
    Voss Scientific, Albuquerque, New Mexico, USA
  • J.M. Byrd, D. Li
    LBNL, Berkeley, California, USA
  • R.P. Johnson, M.L. Neubauer, R. Sah
    Muons, Inc, Batavia, USA
  • A.V. Tollestrup, K. Yonehara
    Fermilab, Batavia, USA
  Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86352
Recent studies have shown that high gradients can be achieved quickly in high-pressure gas-filled cavities without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual vacuum and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of radiofrequency and surface preparation. A series of experiments at 805 MHz using hydrogen fill pressures up to 0.01 g/cm3 of H2 have demonstrated high electric field gradients and scaling with the DC Paschen law limit, up to ~30 MV/m, depending on the choice of electrode material. For higher field stresses, the breakdown characteristics deviate from the Paschen law scaling. Fully-kinetic 0D collisional particle-in-cell (PIC) simulations give breakdown characteristics in H2 and H2/SF6 mixtures in good agreement with the 805 MHz experimental results below this field stress threshold. The impact of these results on gas-filled RF accelerating cavity design will be discussed.