低圧雰囲気におけるアーク現象(第4報)

低圧気中アークにおける探針測定と陰極プラズマ球形成機構に関する考察

抄録

A cathode plasma ball which is formed at the cathode tip end is very interesting from the view point of electric discharge physics. In previous papers, the aathors estimated that this plasma ball would be a cathode-ionization-region which had expanded under the low pressure conditions, but they could not come to the conclusion because the internal construction was not clear.
A fine tungsten probe which was insulated with refractory silica was prepared and it was moved across the arc at high speed in order to avoid both the heat damage of the probe and the arc perturbation by probe insertion. Probe measurements in a low pressure arc were quite successfully carried out by this method, and the axial and radial potentials as well as electron temperature distributions were determined with good reliability both in accuracy and reproducibility.
Inside the cathode plasma ball, a distinct electron beam current is observed. The beam intensity decreases rapidly as the distance from the cathode tip increases and it disappears at the ball end. The electron temperature, on the other hand, increases greatly as the beam is damped. The above indicates that the emitted electrons from the cathode collide with the neutral or ionic particles, resulting in ther-malization of accelerated electrons. Therefore, the authors concluded that the cathode plasma ball is the cathode-ionization-region in the electric discharge as was proposed by Slepian.