Influence of the cathode work function on the sparking potential in hydrogen

Abstract

The Kelvin or vibrating electrode method of measuring contact potential differences has been used to follow changes in work function of evaporated metallic films in a parallel plate electrode system in hydrogen at about 10 mm of mercury pressure. A reduction in cathode work function of the order of 0.3 eV was effected by passing a current of 10-7 A for 10 s. After about 30 min the cathode work function returned to its original value. Similar treatment caused a reduction in the sparking potential of 30 V, which also returned to its original pre-discharge value in times of the order of 30 min. This, together with other experimental data, is consistent with the fact that positive ions from the discharge current remained on the cathode surface for periods up to 30 min after the current was switched off. It has been possible to demonstrate that, while these positive ions are being neutralized, there is a relationship between the work function of a cathode and its sparking potential in hydrogen.