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Title: Electrostatic design and conditioning of a triple point junction shield for a –200 kV DC high voltage photogun [Electrostatic design of a triple point junction shield for a -200 kV DC high voltage photogun using COMSOL]

Abstract

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. Furthermore, 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.

Authors:
 [1];  [2];  [2]; ORCiD logo [2];  [2]
  1. Old Dominion Univ., Norfolk, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  2. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1489811
Alternate Identifier(s):
OSTI ID: 1475477
Report Number(s):
[JLAB-ACC-18-2842; DOE/OR/23177-4563]
[Journal ID: ISSN 0034-6748]
Grant/Contract Number:  
[AC05-06OR23177]
Resource Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
[ Journal Volume: 89; Journal Issue: 10]; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION

Citation Formats

Palacios-Serrano, Gabriel G., Hannon, Fay E., Hernandez-Garcia, Carlos, Poelker, Matt, and Baumgart, Helmut. Electrostatic design and conditioning of a triple point junction shield for a –200 kV DC high voltage photogun [Electrostatic design of a triple point junction shield for a -200 kV DC high voltage photogun using COMSOL]. United States: N. p., 2018. Web. doi:10.1063/1.5048700.
Palacios-Serrano, Gabriel G., Hannon, Fay E., Hernandez-Garcia, Carlos, Poelker, Matt, & Baumgart, Helmut. Electrostatic design and conditioning of a triple point junction shield for a –200 kV DC high voltage photogun [Electrostatic design of a triple point junction shield for a -200 kV DC high voltage photogun using COMSOL]. United States. doi:10.1063/1.5048700.
Palacios-Serrano, Gabriel G., Hannon, Fay E., Hernandez-Garcia, Carlos, Poelker, Matt, and Baumgart, Helmut. Wed . "Electrostatic design and conditioning of a triple point junction shield for a –200 kV DC high voltage photogun [Electrostatic design of a triple point junction shield for a -200 kV DC high voltage photogun using COMSOL]". United States. doi:10.1063/1.5048700. https://www.osti.gov/servlets/purl/1489811.
@article{osti_1489811,
title = {Electrostatic design and conditioning of a triple point junction shield for a –200 kV DC high voltage photogun [Electrostatic design of a triple point junction shield for a -200 kV DC high voltage photogun using COMSOL]},
author = {Palacios-Serrano, Gabriel G. and Hannon, Fay E. and Hernandez-Garcia, Carlos and Poelker, Matt and Baumgart, Helmut},
abstractNote = {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. Furthermore, 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.},
doi = {10.1063/1.5048700},
journal = {Review of Scientific Instruments},
number = [10],
volume = [89],
place = {United States},
year = {2018},
month = {10}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Figures / Tables:

Figure 1 Figure 1: (left) Current CEBAF photogun with un-doped ceramic insulator, (right) updated photogun with doped ceramic insulator and triple-point-junction shield. Vacuum chamber with (a) anode structure, (b1,b2) tapered ceramic insulators with (c) cathode electrode attached. HV conductor surrounded with (d) vulcanized rubber, (e) grounded non-evaporable getter vacuum pumps.

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.