Optical emissions from spherical charges

Optical emissions from 50 and 100-g spherical charges were investigated. When the detonation products (DP) expand, they act like a spherical piston-driving a spherical blast wave into the atmosphere. Emissions from this blast wave come from: shock-heated air molecules, detonation-products molecules, combustion products molecules, and carbon particles formed in the detonation wave. Six HEs were studied: TNT, Comp B, PBX-N5, Comp A5, Tritonal, and AP-NM. HE powder was pressed in hemispherical molds. For TNT and Tritonal, a central booster of PBXN-5 and a RP-80 were used to detonate the charges. Experiments were conducted in air versus N₂ to control combustion, and at different pressures (1, 0.1 and 0.01 bars) to control emissions from the shock-heated air. Emission histories were measured with an Andor fast kinetics spectrometer. In the visible regime, emission spectra were well fit by a Planckian function-thereby allowing us to compute the evolution of the emission temperature of the fireball. Maximum temperatures in the 1^st peak correlate with CJ temperature of the particular explosive. Estimated temperatures fall due to the adiabatic expansion of the fireball gases. The 2^nd optical peak was caused by re-heating of the fireball and carbon particles by the shock reflections from the chamber floor.