Initiation of Lead Azide by High-Intensity Light

Abstract

Radiation from an argon flash-bomb is used to initiate detonation in lead azide aggregates. Optical methods are employed to measure initiation delay as a function of energy absorbed by the azide. It is found that the product of the rate of energy absorption and the initiation delay is constant. This is interpreted in terms of a thermal initiation mechanism as follows: Absorption of flash-bomb radiation causes a continuing increase in azide surface temperature; above a critical temperature Tc, exothermic decomposition of the azide becomes very rapid and leads to thermal explosion and detonation in very short times. Typical initiation delays are of the order of 1 μsec and Tc∼900°K. Reaction-rate parameters calculated on the basis of this model, using measured initiation delays, are in good agreement with those obtained from thermal decomposition studies without explosion. It is shown that, for the experimental conditions used, purely photochemical reactions are unimportant.