Influence of the thickness and absorption coefficient of a copper oxide film on the ignition delay of PENT by a laser pulse

Numerical modeling of PETN ignition by a copper oxide film absorbing laser radiation has been performed. The calculation results showed the presence of a minimum in the curve of the dynamic delay of PETN ignition by a rectangular laser pulse versus thickness of the absorbing film. This effect is due to the fact that when the film thickness is commensurate with the reciprocal of the absorption coefficient, the amount of heat generated in the thin film due to the multiple reflection of the light flux is proportional to its thickness. Therefore, the smaller the film thickness, the more time is required to heat it to the ignition temperature of PETN. In the case of a thick film, additional energy and time are required to heat its cold part to the ignition temperature of PETN.