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Johnson, R.P.

Paper Title Page
MOP011 An 8 GeV CW Linac With High Potential Beam Power 76
 
  • M. Popovic, C.M. Ankenbrandt, A. Moretti, S. Nagaitsev, T.J. Peterson, G.V. Romanov, N. Solyak, V.P. Yakovlev, K. Yonehara
    Fermilab, Batavia
  • R.A. Baartman
    TRIUMF, Vancouver
  • I.B. Enchevich, R.P. Johnson, M.L. Neubauer
    Muons, Inc, Batavia
  • R.A. Rimmer
    JLAB, Newport News, Virginia
 
 

Modern technology allows us to consider operating an 8 GeV Linac in a cw mode to accelerate a high-current H- beam. By using appropriate accumulation rings, the linac could provide simultaneous beams for direct neutrino production, neutrino factories, fixed target experiments, and muon colliders. Several other unique accelerator applications could also be served and improved by the same continuous beam, including studies of energy production and nuclear waste reduction by transmutation, rare muon decay searches, and muon catalyzed fusion. The trade-offs between cw operation compared to pulsed operation that are considered include the maximum rf gradient and corresponding linac length or energy, the rf frequency, rf peak power and coupler requirements, and refrigeration. Methods for accumulating the beam from a cw linac to serve the special needs of the potential future Fermilab programs mentioned above are considered. In this paper we also examine the use of a cyclotron as a source of high current beams to reduce the cost and complexity of the linac front end.

 
THP066 Breakdown in Pressurized RF Cavities 945
 
  • R. Sah, M. Alsharo'a, R.P. Johnson, M.L. Neubauer
    Muons, Inc, Batavia
  • M. BastaniNejad, A.A. Elmustafa
    Old Dominion University, Norfolk, Virginia
  • J.M. Byrd, D. Li
    LBNL, Berkeley, California
  • D. Rose, C.H. Thoma, D.R. Welch
    Voss Scientific, Albuquerque, New Mexico
  • G.M. Wang
    ODU, Norfolk, Virginia
 
 

The performance of many particle accelerators is limited by the maximum electric gradient that can be realized in rf cavities. Recent studies have shown that high gradients can be achieved quickly in 805 MHz cavities pressurized with dense hydrogen gas, because the gas can suppress, or essentially eliminate, dark currents and multipacting. In this project, two new test cells operating at 500 MHz and 1.3 GHz will be built and tested, and the high pressure technique will be used to suppress the vacuum effects of evacuated rf cavities, so that the role of metallic surfaces in rf cavity breakdown can be isolated and studied as a function of external magnetic field, frequency, and surface preparation. Previous studies have indicated that the breakdown probability is proportional to a high power of the surface electromagnetic field, in accordance with the Fowler-Nordheim description of electron emission from a cold cathode. The experiments will be compared with computer simulations of the rf breakdown process.

 
FR202 Linacs for Future Muon Facilities 1119
 
  • S.A. Bogacz
    JLAB, Newport News, Virginia
  • R.P. Johnson
    Muons, Inc, Batavia
 
 

Funding: Supported in part by DOE STTR grant DE-FG02-05ER86253
Neutrino Factories and Muon Colliders require rapid acceleration of short-lived muons to multi-GeV and TeV energies. A Recirculated Linear Accelerator (RLA) that uses a single Linac and teardrop return arcs (the so called 'Dogbone' RLA) can provide exceptionally fast and economical acceleration to the extent that the focusing range of the RLA quadrupoles allows each muon to pass several times through each high-gradient cavity. Since muons are generated as a tertiary beam they occupy large phase-space volume and the accelerator must provide very large transverse and longitudinal acceptances. The above requirements drive the design to low rf frequency. A new concept of rapidly changing the strength of the RLA focusing quadrupoles as the muons gain energy is being developed to increase the number of passes that each muon will make in the rf cavities, leading to greater cost effectiveness. We are developing the optics and technical requirements for RLA designs, using superconducting rf cavities capable of simultaneous acceleration of both μ+ and μ- species, with pulsed Linac quadrupoles to allow the maximum number of passes.

 

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