Influence of the laser pulse shape on plasma formation near absorbing targets

An experimental justification is given for an expression relating the energy density of laser radiation interacting with a target to the time of the initial formation of plasma, and a simple formula following from it is proposed for estimating this time as a function of the shape of the leading edge of the laser pulse and of the maximum density of the high-power laser radiation. The proposed formula enables a detailed analysis to be made of the results of measurements, obtained under differing experimental conditions, of the formation time of a laser plasma.