Noble Gas Retention Effect on Klystron High Voltage Stability

Several fielded klystrons experienced operational interruption due to sporadic arc events. Root cause analysis at CPI Canada revealed that VacIon pumps used to process these klystrons were saturated with nobble gases. Pressure bursts in pumping process indicated spontaneous release of gases back into the system. This process resulted in residual pressure of noble gases in the klystron. The cycle of adsorption and spontaneous release continued in the operating klystron resulting in sporadic high voltage arcing. This paper describes the details of root cause analysis and preventive actions.