X-RAY-EMISSION FROM PLASMAS FORMED USING AN EXCIMER-LASER WITH VARIOUS PULSE LENGTHS

We report experiments to study the effects of the laser-pulse duration , angle of incidence and target material on x-ray generation. Metallic targets (Cu and Al) were illuminated with picosecond and sub-picoseco nd KrF excimer laser pulses focused to maximum intensities of 5 x 10(1 4) W cm(-2) with 5 ps and 6 x 10(15) W cm(-2) with 150 fs pulses. The resulting plasma produces soft x-rays in the 1 keV range. Copper targe ts illuminated at about 45 degrees with 5 ps pulses gave the highest x -ray conversion efficiency (1.6%). In addition to the soft x-rays, a h ard x-ray signal (h nu > 20 keV) was also detected with 450 fs pulses. This is assumed to be due to the fast electrons generated by the inte raction of the higher intensity sub-picosecond laser pulse with the so lid target.