Soft X-ray radiation from metal targets at interaction of 9-ns laser pulses

A neodymium YAG laser operating at fundamental frequency (energy of 300 mJ) and at the second harmonics (at 200 mJ) and generating pulses of 9 ns duration was applied to irradiate Al, Cu, and Ta targets in the conditions of high vacuum. The plasma generated from these targets was investigated with the use of X-rays and optical diagnostics. X-rays were measured with the use of X-ray vacuum diodes (XRDs) and a semiconductor detector. The emission in the visible range was observed with the use of a CCD camera and an optical spectrometer. Different thin filters were used to choose energy ranges of observed photons. The dependence of X-ray yield on the energy of the laser and the focus position in the relation to the position of target were investigated. The CCD camera showed plasma light flashes of dimension of the order of 1 mm³. The optical spectrometer in the visible region detects characteristic lines of neutral and single ionised atoms. The X-ray and optical diagnostics were evaluated for their possible use for detailed characterisation and optimisation of the X ray source based on a small nanosecond laser.