Development of a laser produced plasma x-ray source by use of Au thin film targets

Laser produced plasmas are attractive soft x-ray sources for a soft x-ray microscopy, because of their short duration time enough to stop the movement of living nature and the Brownian motion, and to capture images before the structural changes by radiation damages. To develop an intense soft x-ray source, soft x-ray emissions from laser produced plasmas using Au thin film targets were observed with respect to the film thickness. Au thin films having nano-meter order thicknesses evaporated on silicon nitride membranes were irradiated by a high contrast Nd:glass laser pulses with OPCPA system. The spectra of emitted soft x-rays were monitored by an x-ray spectrograph from the rear side to the surface of laser irradiation. The observed emission intensities showed a clear dependence on the film thickness. The results suggest that most of the irradiated laser energy is absorbed by the film, and is efficiently converted from laser to x-rays. (author)