The role of electromagnetic radiation in hypervelocity impact mechanics

Abstract

This paper is based upon an acceptance presentation I made for the 1998 Distinguished Scientist award presented by the Hypervelocity Impact Society. Nearly thirty years ago, I recorded a cine sequence of a gaseous debris plume expanding behind a thin cadmium plate impacted by a cadmium sphere. The plume stagnated on a second plate where it glowed so brightly that it must have been heated to over 50,000 oK. The fact went unnoticed for nearly twenty years until it was predicted theoretically and then finally observed. The theoretical analysis showed that virtually all gaseous impact debris that is intercepted gives up its energy to electromagnetic radiation. Potential exists to use the resulting radiation for a variety of research opportunities. More recently, tungsten plasma accelerated electrically with a 10 MV pulse generator at Sandia National Laboratories has been imploded onto the axis of an evacuated cylindrical cavity where it stagnates against itself to produce enormous pulses of incoherent electromagnetic radiation. The intensity of the radiation is so great that it vaporizes and launches surface material off samples exposed to it. Extremely intense shockwaves are produced that are being used for extending material equation-of-state determinations well above pressure levels reachable by laboratory impacts.