Time variations in the pressure exerted on the cathode during the operation of the cathode spot of a vacuum arc

The paper presents preliminary results of experiments on studying the time behaviour of the pressure exerted on the cathode of a vacuum are by the cathode spot. The cathode was made as a copper film deposited on a glass substrate. During the operation of the cathode spot of a vacuum are, sound waves propagate in the cathode, enter the glass and change its optical properties. This results in scattering of incident laser radiation. For a 3-A are current of duration 50 ns an oscillogram of a current pulse of duration 200 ns, taken with a photorecorder, has been modulated with a period of about 25 ns, which suggests that the pressure is cyclic in character.