Erosion jet breakdown accompanying pulsed irradiation of metals by a neodymium laser

A calculation was made of the surface temperature of a metal at the moment of breakdown accompanying interaction with rectangular neodymium laser radiation pulses of microsecond duration and of ~ 500 MW/cm² intensity. The surface temperature at the moment of plasma formation was found to be weakly dependent on the incident radiation intensity, to be practically constant for each metal, and to exceed the metal boiling point by several hundred degrees. Calculations were performed for a number of metals and the results were compared with experiment. A comparison with previous studies of the breakdown of metal vapors accompanying the interaction of millisecond laser pulses having an intensity of the order of 1 MW/cm² snowed that the sharp fall in the surface temperature (at the moment of breakdown) on increase in the intensity, which was discovered in these studies, was due to a different dependence of the ionization coefficient on the intensity.