THE EFFECTS OF MULTIPULSE IRRADIATION ON X-RAY LASER MEDIA

Multipulse irradiation with 100 ps pulses of stripe Germanium targets is shown to enhance by up to several orders-of-magnitude the output of Ne-like Ge lasing on the J = 0-1 line at 196 Angstrom compared to sin gle pulse pumping. Various pre-pulse and multipulse configurations hav e been experimentally investigated for irradiances of approximate to 4 x 10(13) W/cm(2) with a 1.06 mu m wavelength pumping laser. The ionis ation balance measured by a KeV crystal spectrometer (KAP crystal) has been found to not affect the X-ray laser output. Good agreement betwe en the experimental results and a fluid code incorporating atomic phys ics, gain and X-ray beam ray tracing is obtained. The code results sho w that the enhanced X-ray laser output is produced by multipulse irrad iation reducing the electron density gradients in the gain region and simultaneously increasing the gain region spatial size. These changes reduce the effect of refraction on the X-ray laser beam propagation.