Fabrication of an Ultra High Vacuum Compatible Faraday Cup for Qualification of Electron Gun for 10 kW Industrial LINAC

In this paper, we report fabrication and testing of a unique Faraday Cup designed for qualification of Electron Gun for a 10 kW industrial LINAC. This is a compact device consisting of a tapered copper cavity electrically isolated by a ceramic cylinder metalized at both ends. Kovar tubes matching with the diameter of ceramic isolator were used at both ends to facilitate high quality UHV compatible joints with copper cavity at one end and standard knife edge stainless steel flange at the other end. The Kovar tube was flared at both ends to form a collar matching with the outer diameter of the ceramic isolator. The joint between Kovar collar and ceramic isolator was done by hydrogen brazing using copper silver eutectic alloy. All the joints were tested with helium leak detector and leak rates were found to be below 1 × 10⁻¹⁰mbar.litre/second.