Update on the R&D of vertical buffered electropolishing on Nb samples and SRF single cell cavities

Conference · Fri Jun 01 00:00:00 EDT 2012

OSTI ID:1994845

Wu, Andy; Jin, Song; Lu, X.Y.; Rimmer, Robert; Zhao, K.; Lin, L.; Mammosser, John

Electropolishing (EP) has become a popular choice as the final step of the surface removal process during the fabrication of Nb superconducting radio frequency (SRF) cavities. One of the major reasons for the choice is that Nb SRF cavities treated by EP tend to have a better chance to reach an accelerating gradient of 30 MV/m or higher than those treated by buffered chemical polishing (BCP). This advantage of EP over BCP can at least be partially attributed to the smoother Nb surfaces that EP can produce. Recently a Nb surface removal technique called buffered electropolishing (BEP) was developed at JLab. The root mean square of the Nb surfaces treated by BEP can be as smooth as 20nm over a surface area of 200X200 ?m2. In this contribution, R&D efforts of vertical BEP on Nb small flat samples and SRF single cell cavities since the last SRF conference in 2009 will be updated. It is shown that under a suitable condition, BEP can have a Nb removal rate as high as 10 ?m/mim that is more than 25 and 5 times quicker than those of EP and BCP(112) respectively. Possible mechanisms responsible for the high Nb removal rate are proposed. Clues on the optimization of vertical BEP and EP treatments on Nb SRF cavities from recent experimental results obtained on a Nb single cell demountable cavity will be discussed.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1994845
• Report Number(s): JLAB-ACC-11-1533; DOE/OR/23177-6954
• Resource Relation: Conference: SRF 2011, Chicago, IL USA, July 21, 2011
• Country of Publication: United States
• Language: English