Emission and Absorption of Light behind the Detonation Front

Abstract

WHEN a high explosive detonates, the measurement of the true emission of light from the detonation gases is of great interest. In air, however, the expanding detonation gas is enveloped in a compressed layer of the displaced air, which acquires a high temperature (c. 8,000° K. at atmospheric pressure) and emits an intense light. An easy way of eliminating the luminous layer of air is to immerse the charge in water. Charges of TNT and phlegmatized PETN, for example, then show a narrow luminous zone behind the detonation front. Fig. 1 shows instantaneous pictures (exposure time, 0.03 µsec.) of detonating cylinders of phlegmatized PETN of 1.55 gm./cm.³ density and 25-mm. diameter, first with (1a) then without (1b) background light of a detonated TNT-ball, (In Fig. 1b and Fig. 2 the upper end of the charge was above the surface.)