STARTING PROCESS OF LASER-TRIGGERED VACUUM-ARC ION-SOURCE

A laser-triggering method was applied to a vacuum are ion source to im prove triggering reliability. A frequency-doubled Nd-YAG laser was foc used onto the are cathode at a laser power density of (4.5-6.1) x 10(8 ) W/cm(2). Time-resolved observations revealed that a cathode spot was initially formed within the laser focusing area and the distribution of the cathode spots expanded circularly with time because of the retr ograde motion of each cathode spot. The mean square displacement of th e retrograde cathode spot was found to be proportional to the discharg e time. Moreover, are ignition probability with the laser trigger was measured under various conditions. It was found that the ignition prob ability strongly depends on the laser intensity and the gap spacing. T his paper discusses the starting process of the laser-triggered vacuum are discharge on the basis of the experimental results.