Theoretical analysis of the conditions for a thermal explosion and of a photoionization instability of transparent insulators containing absorbing inclusions

An analysis is made of the conditions favoring thermal explosion of an absorbing inclusion under the influence of laser radiation. The concept of a threshold function is introduced in such a way that the extrema of this function determine the threshold temperature and the intensity for a thermal explosion of an inclusion. A two-threshold model of damage to a transparent insulator is discussed. It is shown that photoionization of the insulator matrix by the thermal radiation emitted from a heated inclusion results in a thermal explosion in the vicinity of the inclusion. The explosion induction time is found and an experimental method for the determination of this time is discussed. Numerical estimates are given of the threshold intensity of a photoionization thermal explosion and of its induction time.