Glow discharge cleaning of stainless steel accelerator beam tubes

Abstract

Glow discharge cleaning has been employed successfully in the CERN ISR to eliminate beam induced pressure bumps and had been adopted as a final surface treatment for the beam vacuum system of CBA. A glow discharge cleaning facility for beam tubes up to 5.5 m in length has been constructed and is in operation. To ensure efficient and thorough cleaning of the long tubes, a residual gas analyzer was used to monitor the exhaust during cleaning. Quantitative studies of the glow discharge process were performed on several tubes by using Ar or Ar/O2 mixture (0.1 to 10 Pa) and by varying the discharge density (≤30 μA/cm2). The results of the studies, such as the desorption yields of H2O, CO, and CO2 with respect to the accumulated dosage, the depletion of O2 in Ar/O2 mixture, will be reported here. The effect of venting to air and CO2, as well as plasma deposition of carbon will also be discussed.