Electrical measurements in reaction zones of high explosives

Abstract

Electrical conductivity profiles with nanosecond and subnanosecond time resolution have been determined for some condensed high explosives using a dynamic conductivity cell. Three explosives are treated in detail, namely, nitromethane, Composition B, and liquid TNT. Each explosive presents a somewhat different conductivity profile as well as a different value for the peak conductivity. The peak conductivity for nitromethane is about 160 mhos per meter, and the peak occurs between 1.5 and 2 nsec behind the detonation front. The conductivity thereafter decreases to a nearly constant value of about 135 mhos per meter, falling off only slightly in the Taylor wave. The conductivity of Composition B, on the other hand climbs steadily, reaching a peak value of 1100 mhos per meter between 80 and 100 nsec after passage of the detonation front. Liquid TNT reaches peak conductivity about 20 nsec after the passage of detonation, front, even though the peak value of the conductivity is nearly an order of magnitude higher than that of Composition B. The profile experiments show that it is unlikely that a single value of the conductivity for detonation products is meaningful. However, the curves of conductivity as a function of time do have certain similarities in their shapes. If the conductivities at corresponding points on each curve, say the maximum, are compared, a strong correlation with the available estimates of the density of solid carbon in the detonation products is evident. This leads to the hypothesis that, in carbon rich explosives, conduction is principally by a continuous network of solid carbon particles.