Current measurements in plasma produced by the train of 10.6-um subnanosecond laser pulses

Abstract

Results of current probe measurements for a plasma produced by the train of ∼200 ps 10.6 μm laser pulses are reported. The train of pulses was obtained as a result of regenerative amplification (injection mode locking) of ∼ 100 ps laser pulse in a 5 cm aperture 6 atm TE-CO 2 laser. Experiments were carried out for Wo and Al targets disposed in vacuum (10 -2 torr), two values of the interpulse separation in the train ΔT= 9.3 and 29 ns and wide range of energy density on the target, corresponding to peak intensities of sigle pulses Ip = 1 + 300 GW/cm 2 . Experiments had shown large difference of temporal structure of current signals with Wo and Al targets due to the considerable difference in melting temperatures of these materials as well as radiation losses of laser plasma. We detected large (∼2 orders of magnitude) ratio of current signal amplitudes for targets irradiation by the pulse train or gain switched pulse (50 -100 ns FWHM) generated in TE-CO 2 laser without injection of a short pulse. Results of these measurements are compared with those earlier obtained for nanosecond pulse train.