Author: Sah, R.
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.
THPPC065 Phase and Frequency Locked Magnetron 3440
  • M.L. Neubauer, A. Dudas, R. Sah
    Muons, Inc, Batavia, USA
  • A. Moretti, M. Popovic
    Fermilab, Batavia, USA
  Funding: Supported in part by SBIR Grant 4724 · 09SC02766
Phase and Frequency locked magnetrons have many important uses from phased array ground penetrating radars to SRF sources. We report on the recent progress in making such a magnetron. The ferrite/garnet material has passed bakeout and outgassing tests with outgassing rates well below the requirements. The magnetic field requirements for adjusting the frequency by changing the microwave properties of the ferrite/garnet have been determined. The design of the anode structure with ferrites, magnetic shielding, and magnetic bias has been completed for a low power test. We report on the design status. Muons, Inc. has negotiated an contract with a manufacturing firm, L-3 Electron Devices California Tube Laboratory, Inc., to be the Manufacturing Partner for the commercialization of this technology and support these Phase II efforts.
THPPC066 Adjustable High Power Coax RF Coupler without Moving Parts 3443
  • M.L. Neubauer, A. Dudas, R. Sah
    Muons, Inc, Batavia, USA
  • A. Nassiri
    ANL, Argonne, USA
  A high power fundamental RF power coupler (FPC) with an adjustable in situ coupling factor would be highly desirable for a number of applications; for example, the 352 MHz light source at APS and Project X. A Phase I project has been completed with a prototype constructed and modeled. The prototype includes a coaxial TEE with two windows a quarter wavelength apart, and a ferrite tuner. Two materials were tested and their characteristics measured in terms of loss and magnetic field requirements to produce the desired change in coupling. A VSWR of better than 1.05:1 and a bandwidth of at least 8% at 1.15:1 was measured. The tradeoffs of a final design are proposed based upon these results.  
THPPC032 Conditioning and Future Plans for a Multi-purpose 805 MHz Pillbox Cavity for Muon Acceleration 3353
  • G.M. Kazakevich, A. Dudas, G. Flanagan, R.P. Johnson, F. Marhauser, M.L. Neubauer, R. Sah
    Muons, Inc, Batavia, USA
  • S.S. Kurennoy
    LANL, Los Alamos, New Mexico, USA
  • A. Moretti, M. Popovic, G.V. Romanov, K. Yonehara
    Fermilab, Batavia, USA
  • Y. Torun
    IIT, Chicago, Illinois, USA
  Funding: Supported in part by grant 4735 · 10 LANL and Dept. of Energy STTR grant DE-FG02-08ER86352.
An 805 MHz RF pillbox cavity has been designed and constructed to investigate potential muon beam acceleration and cooling techniques for a Muon Collider or Neutrino Factory. The cavity can operate in vacuum or under pressure to 100 atmospheres, at room temperature or in a liquid nitrogen bath at 77 K. The cavity has been designed for easy assembly and disassembly with bolted construction using aluminum seals. To perform vacuum and high pressure breakdown studies of materials and geometries most suitable for the collider or factory, the surfaces of the end walls of the cavity can be replaced with different materials such as copper, aluminum, beryllium, or molybdenum, and with different geometries such as shaped windows or grid structures. The cavity has been designed to fit inside the 5-Tesla solenoid in the MuCool Test Area at Fermilab. In this paper we present the vacuum conditioning results and discuss plans for testing in a 5-Tesla magnetic field. Additionally, we discuss the testing plan for beryllium (a material research has shown to be ideal for the collider or factory) end walls.