Formation and decay of micropinch in a laser initiated vacuum spark

Results of experimental studies of the development and decay of a micropinch produced in a laser-induced vacuum spark are presented. The studies were performed with X-ray pinhole frame camera supplied with a micro-channel plate as a photocathode and the following visualization of the image by a luminous screen. The pinhole was covered with an Al foil of 0.8 micrometer thick that transmitted the X-ray emission in the range of 15-84 eV. The experiments were performed with the initiating laser pulse energy in the range of 0.5-200 mJ at the discharge voltage of 4, 8, 15 kV. It was found that process of the cathodic plasma jet pinching at the specified discharge current was governed just the mass of the laser produced plasma. It was shown also that dependence of the pinch position distance from the cathode against the laser pulse energy has a power-low dependence L ~ J^α where the index α increases with the discharge voltage and ranged from 0.26 to 0.35.