No Access Submitted: 17 July 2018 Accepted: 17 September 2018 Published Online: 03 October 2018
Review of Scientific Instruments 89, 104703 (2018);
more...View AffiliationsView Contributors
  • G. Palacios-Serrano
  • F. Hannon
  • C. Hernandez-Garcia
  • M. Poelker
  • H. Baumgart
Nuclear physics experiments performed at the Continuous Electron Beam Accelerator Facility (CEBAF) at the Jefferson Lab require a DC high voltage photogun to generate polarized electron beams from GaAs photocathodes. The photogun uses a tapered ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. Increasing the operating voltage from nominal −130 kV to −200 kV will provide lower beam emittance, better transmission through injector apertures, and improved photocathode lifetime. This desire to increase the photogun operating voltage led to the design of a triple-point-junction shield electrode which minimizes the electric field at the delicate insulator-metal-vacuum interface and linearizes the potential across the insulator, thus reducing the risk of arcing along the ceramic insulator. This work describes the results obtained using COMSOL® electrostatic-field simulation software and presents the high voltage conditioning results of the upgraded −200 kV CEBAF photogun.
This article was authored by Jefferson Science Associates, LLC, under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. The authors wish to thank J. Hansknecht, D. Machie, and K. Harding for assistance with CAD files.
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