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 (γm) 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 γm 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 γm or the work function φ.