Minimum Sparking Potentials of Barium, Magnesium, and Aluminum in Argon

Abstract

Minimum sparking potentials of barium, magnesium, and aluminum in argon are found to be 93±½ v, 123±1 v, and 155±1 v, respectively. Utilizing the data in measuring the minimum sparking potentials, the ratios of electrons emitted from the cathode per bombarding positive ion (γ_m) are determined and found to be .149±.001 for barium, .089±.033 for magnesium, and .045±.002 for aluminum. A relationship is found such that, at a given field per unit pressure, a lower work function indicates a lower sparking potential and a higher γ_m indicates a lower sparking potential, for the case of the three metals studied. A graphical method is proposed for predicting the minimum sparking potentials for metals, whose sparking potential values have not been determined, based upon the values of γ_m or the work function φ.