Arc initiation at metal surfaces in a hydrogen Penning discharge

摘要: Arc formation at metal surfaces in a hydrogen plasma has been studied gas pressures of 25-60 mtorr. The was generated by means high current cold cathode Penning-type discharge with axial magnetic field, which defined the electrode areas receiving ion bombardment. Planar cathodes and probe wires various metals were subjected to 100 μsec 30 pulses respectively, each about 10 A cm-2 2 kv. occurrence arcs investigated over long periods, up 106 rate one per second. Measurements time-lag arc showed two distinct stages conditioning under Initially, specimens contaminated or oxidized arced every pulse, mean time-lags increasing from full pulse length number pulses; this dependent on degree contamination. Finally, when sputtering had removed surface impurities, few still occurring formed near start occurred randomly pulses. final arcing is shown correlate impurity content metal. effects heat treatment before test heating during examined. For example, zero obtained 5 × 105 purity platinum maintained 700°C hydrogen. Local particles bombardment consistent initial behaviour. Field emission associated impurities within may account for behaviour after conditioning.