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Title: In Situ observation of dark current emission in a high gradient rf photocathode gun

Undesirable electron field emission (also known as dark current) in high gradient rf photocathode guns deteriorates the quality of the photoemission current and limits the operational gradient. To improve the understanding of dark current emission, a high-resolution (~100 μm) dark current imaging experiment has been performed in an L-band photocathode gun operating at ~100 MV/m of surface gradient. Scattered strong emission areas with high current have been observed on the cathode. The field enhancement factor β of selected regions on the cathode has been measured. Finally, the postexaminations with scanning electron microscopy and white light interferometry reveal the origins of ~75% strong emission areas overlap with the spots where rf breakdown has occurred.
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [2] ;  [4] ;  [4] ;  [4] ;  [3] ;  [5] ;  [4]
  1. Tsinghua Univ., Beijing (People's Republic of China); Argonne National Lab. (ANL), Lemont, IL (United States)
  2. Tsinghua Univ., Beijing (People's Republic of China)
  3. Argonne National Lab. (ANL), Lemont, IL (United States); Euclid Techlabs LLC, Bolingbrook, IL (United States)
  4. Argonne National Lab. (ANL), Lemont, IL (United States)
  5. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 117; Journal Issue: 8; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
National Natural Science Foundation of China (NNSFC); USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
OSTI Identifier:
1344928
Alternate Identifier(s):
OSTI ID: 1294720