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TY - UNPB AU - Yamamoto, M. AU - Nishimori, N. ED - Ramberger, Suitbert ED - Draper, Mick ED - Schaa, Volker RW TI - Discharge Mechanism of Ultra-High Vacuum Gap Derived From the HV Conditioning Result of the cERL DC-Gun J2 - Proc. of ERL2017, Geneva, Switzerland, June 18-23, 2017 C1 - Geneva, Switzerland T2 - ICFA Advanced Beam Dynamics Workshop T3 - 59 LA - english AB - Development of a high brightness electron beam source is indispensable for realizing high repetition X-FEL and CW EUV-FEL as a next generation light source. The high voltage (HV) DC-gun that realized acceleration voltage of > 500 kV and electric field of > 5 MV/m is one of the candidates. In order to stably DC-gun operation, the HV conditioning process is an essential step as preparation of DC-gun operation. The HV conditioning was carried out on compact-ERL (cERL) electron gun and clarified the following four points. i) The voltage at which discharge stops (discharge stop voltage) exists, ii) The discharge stop voltage increases almost continuously with the number of discharges, iii) The gas released at the occurrence of discharge is almost proportional to the difference between the discharge start voltage and the discharge stop voltage, iv) The hold-off time of the voltage is very long under the discharge stop voltage. We focused on the electron stimulated desorption (ESD) phenomenon occurring at the anode can explain these phenomena in a consistent and considered the mechanism of discharge generation in DC field and HV conditioning progression in ultrahigh vacuum (UHV). PB - JACoW Publishing CP - Geneva, Switzerland ER -