Spectroscopic measurement of high-pressure argon plasma produced by excimer laser

When a XeCl excimer laser beam was focused in a high-pressure gas of up to 100 atm, a hot and dense plasma was produced at the focal spot. The plasma developed not only backward but also forward. The forward plasma developed by means of a forward breakdown wave. The radius of the forward plasma becomes smaller further from the focal spot because the laser beam transmitted through the plasma was further focused by the plasma. The radiation intensity from plasma produced by an ultraviolet laser was observed using a spectrometer. The temporal spectral intensity signal had two peaks. The first peak was a signal from the plasma produced at the observed point, but the second peak was that diffused from the back. The electron temperature was measured from the ratio of the spectral intensity of Ar II lines. The electron temperature on the order of 10(5) K was obtained.