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Title: Evaluation of niobium as candidate electrode material for DC high voltage photoelectron guns

In this study, the field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and gradient. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a gradient of 18.7 MV/m.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3]
  1. Old Dominion Univ., Norfolk, VA (United States)
  2. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  3. NASA Langley Research Center, Hampton, VA (United States)
Publication Date:
Report Number(s):
JLAB-ACC-12-1571; DOE/OR/23177-2169
Journal ID: ISSN 1098-4402; PRABFM; TRN: US201218%%22
Grant/Contract Number:
AC05-06OR23177; AC05-84ER40150
Type:
Published Article
Journal Name:
Physical Review Special Topics. Accelerators and Beams
Additional Journal Information:
Journal Volume: 15; Journal Issue: 8; Journal ID: ISSN 1098-4402
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; DIAMONDS; ELECTRODES; EVALUATION; FIELD EMISSION; KRYPTON; NIOBIUM; STAINLESS STEELS; STEELS
OSTI Identifier:
1074783
Alternate Identifier(s):
OSTI ID: 1049492