Electrostatic beam separation system of TRISTAN Main Ring

Sixteen electrostatic separators have been installed in the TRISTAN Main Ring. The maximum designed voltage is 240 kV across a gap of 8 cm between 4.6 or 3.2-m long titanium electrodes. In order to make the HV (high voltage) sparking rate as low as possible, the chemical cleaning process of the electrodes and the chamber surfaces was studied carefully. All of the HV-bushing and ceramic supports were tested by applying up to 150 kV, and assembled into the separator chamber in a clean room. Special care was given to securing the passage of the wall current produced by the passing bunched beam, preventing HV breakdown. The power of the parasitic mode was pulled out and damped by the ferrite microwave absorbers inside the shield box, making direct cooling of the electrodes unnecessary and simplifying the structure of the separator. No HV spark was observed over two days for 16 separators at 240 kV with the beam not circulating in the ring. With beams of 9-mA total current, neither beam loss nor sparks were observed at a separation voltage of 200 kV