Meysam Akhtar - Detonation under a Microscope: Nanosecond Resolved Temperature Dynamics

Speaker: Meysam Akhtar, University of Illinois, Urbana –Champaign

Abstract: Accurate measurement of the hot spot and combustion temperatures is an essential part of understanding the behavior of insensitive high explosives. These explosives are particularly interesting because they are powerful but insensitive to accidental initiation. In this talk, I will discuss measuring the temperature dynamics of shocked initiated insensitive high explosives with nanosecond time resolution. The explosive temperatures were determined by measuring the spectral radiance in the visible region and fitting the radiance to a graybody model. These measurements are made possible by our shock compression microscope, which looks into materials as they are subjected to controlled high-velocity impacts from laser-launched flyer plates. The tiny plates of metal foil move up to several kilometers per second and can produce a shock wave with up to 200,000 atm pressure jump within one nanosecond while compressing matter up to twice the density. We can fabricate arrays of 1 mm diameter plastic-bonded explosive charges and push them to detonation while we watch. This shock compression microscope lets us see right inside detonating high explosives with high time and space resolution and measure the temperature, pressure, and velocity in real-time. These techniques are not limited to explosives but can find applications in physics, materials science, planetary sciences, biomedicine, chemistry and astronautics.