PULSED VACUUM-ARC PLASMA SOURCE WITH LASER ARC EXCITATION

Abstract

A method of solution to the issue of contamination of the laser beam input window in pulsed vacuum-arc plasma sources with vacuum arc laser excitation is proposed. The method involves the periodic introduction of energy through an unfocused laser beam into a layer of condensate formed on the surface of the laser beam input window. The focus of such a cleansing laser beam is located outside the vacuum chamber, ensuring the absence of unauthorized activation of the plasma source, and the optical axis is perpendicular to the input window surface, providing optimal conditions for removing the formed condensate film. The periodicity of cleansing the laser beam input window, which determines the window throughput, is based on the condition of ensuring the probability of vacuum arc excitation not below a specified level. The area of the cleansing laser beam unfocusing spot Sunf on the laser beam input window surface facing the plasma source cathode is determined under the condition of ensuring the power density q of the laser radiation on the cleansed surface in the range of 104 ≤ q ≤ 105  W/cm2 and the condition Sunf ≥ Sexc, where Sexc is the area of the laser beam spot that excites the vacuum arc discharge on the input window surface facing the plasma source cathode. The vacuum arc excitation in the pulsed plasma source using the proposed method, which allows removing the condensate layer on the laser beam input window, is characterized by a stable 95% probability of exciting the vacuum arc at a pulse repetition frequency of 300 Hz, regardless of the plasma source operating duration.