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

Journal Article · Mon Aug 15 00:00:00 EDT 2016 · Physical Review Letters

DOI: https://doi.org/10.1103/PhysRevLett.117.084801 · OSTI ID:1344928

Shao, Jiahang ^[1]; Shi, Jiaru ^[2]; Antipov, Sergey P. ^[3]; Baryshev, Sergey V. ^[3]; Chen, Huaibi ^[2]; Conde, Manoel ^[4]; Gai, Wei ^[4]; Ha, Gwanghui ^[4]; Jing, Chunguang ^[3]; Wang, Faya ^[5]; Wisniewski, Eric ^[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)

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.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: National Natural Science Foundation of China (NSFC); USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1344928
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 8 Vol. 117; ISSN 0031-9007; ISSN PRLTAO
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English