Heating of heat-conducting targets by laser pulses with a high-intensity leading spike

The results of an analysis of the solution of a one-dimensional heat conduction equation are used to study the specific features of the thermal effects of laser pulses with a leading spike on a target. Simple criteria are obtained for establishing the ability of a pulse to cause a given increase in the target surface temperature during the leading edge of a spike and also during the tail of the laser pulse. A study is made of the influence of the inhomogeneity of the distribution of surface heat sources on the realization of processes characterized by a threshold in respect of the temperature of the irradiated surface. The results obtained are compared with the experimental delay time in the process of initiation of an air breakdown plasma by interaction of CO₂ laser pulses with a metal target.