Abstract: The wall current probe, as a probe for measuring the longitudinal size and intensity of the bunch, is widely used in the accelerator system. The accelerator vacuum system is an ultra-high vacuum system, and the alumina ceramics are resistant to high temperature with high insulation performance, low outgassing rate and high dielectric strength. Stainless steel is resistant to corrosion, can be baked and has low outgassing rate, which is a common and excellent material for ultra-high vacuum system. This paper introduces the brazing technology of ceramic and Kovar, the argon arc welding structure of Kovar and stainless steel and the helium mass spectrometer leak detection.

Key words: vacuum brazing, brazing of ceramic and Kovar, welding structure of Kovar and stainless steel, helium mass spectrometer leak detection