K-shell Emission Spectroscopy of Aluminium Plasma Irradiated by Intense Laser Pulses

Abstract

In order to characterise several parameters of solid-density aluminium plasma irradiated by laser pulses (800 nm, 100 ps, 30 mJ), K-alpha emissions are measured using an x-ray spectrometer consists of a flat PET(002) crystal and x-ray CCD detector. K-alpha photon yields for various incident angles to the laser target are measured. The experimental data could be understood based on the angular dependency of laser absorption mechanisms, i.e. resonance absorption and inverse bremsstrahlung. With a laser intensity of 1.0 x 10^14 W/cm^2, both resonance absorption and inverse bremsstrahlung work effectively, and a plasma temperature 98 eV, collisional frequency 4.8 x 10^13 s^-1, and a plasma scale length 6 μm are determined.