Dynamics of development and spectral composition of radiation emitted by plasma jets generated as a result of interaction between a λ = 10.6 μ laser beam and various materials

An experimental investigation was made of the interaction of λ = 10.6 μ laser pulses with graphite and Duralumin. The power density of the laser pulses was 1–5 MW/cm² and the air pressure during irradiation was 0.5–760 mm Hg. The duration of the laser pulses was ~3.3 μsec and the diameter of the irradiated spot was 15 mm. Throughout the investigated range of power densities and air pressures, the emission spectra of plasma jets resulting from the interaction between laser pulses and the investigated targets were quite similar to the spectrum of laser sparks in air. The brightness temperature of the plasma jets was independent (to within the limits of experimental error) of the target material and was governed by the laser density. The measured values of the velocity of propagation of the luminous jet front at atmospheric pressure were in satisfactory agreement with those calculated from the theory of optical detonation but the rise of the front velocity with decreasing pressure was slower than predicted by this theory.