CENTRIFUGAL BARREL POLISHING OF CAVITIES WORLDWIDE

Much interest was generated in the mid to late 1990s in an alternative cavity surface processing technique called centrifugal barrel polishing, that mechanically polishes the inside of superconducting RF (SRF) cavities by rotating them at high speeds while filled with abrasive media. This work, which was originally done at the KEK High Energy Accelerator Research Organization (KEK) by Kenji Saito & Tamawo Higuchi, has received renewed interest recently because of work done at the Fermi National Accelerator Lab (Fermilab) which has produced mirror like finishes on the 1.3 GHz Tesla-type cavity SRF surface. In addition to Fermilab & KEK, the Cornell University SRF Group (Cornell), the Thomas Jefferson National Accelerator Facility (JLab) and the Raja Ramanna Centre for Advanced Technology (RRCAT) are all exploring CBP as a cavity processing technique. CBP is interesting as a cavity processing technique because it removes defects associated with the manufacturing process, it can yield surface finishes (Ra) on the order of 10s of nanometers, it is a simple technology that could transfer easily to industry, it could help increase cavity yields and it requires less acid than other techniques. Recent progress and the current status of CBP as a baseline and repair technique will be discussed.