Reduction of ejecta from asperities on a metal surface upon shock breakout

Ejecta can be produced when a shock breaks out of a metallic surface with imperfections. The amount of material ejected depends on the wave profile and the surface finish. This work focuses on techniques to reduce the amount of ejecta produced. As a baseline, a Taylor wave loading was produced by detonating a high explosive next to an aluminum target featuring V-grooves on the free surface. The ejecta and free surface velocities were monitored with photonic doppler velocimetry (PDV). In an attempt to suppress the ejecta, the shock pressure was reduced by the addition of an air gap. The effect of a vacuum gap was also investigated. PDV spectrograms show that significant ejecta traveling at roughly three times the free surface velocity was produced when explosives were in contact with the target. The placement of an air gap or a vacuum gap between explosive and target suppressed detectable ejecta.