D-25 Observations of Shocked Metallic Surfaces with Single-Pulse X-ray Diffraction

Abstract

A single-pulse X-ray diffraction (XRD) diagnostic has been developed for the investigation of shocked material properties on a very short time scale. The diagnostic, which consists of a 37-stage Marx bank high-voltage pulse generator coupled to a needle-and-washer electron beam diode via coaxial cable, produces line and bremsstrahlung X-ray emission in a 40-ns pulse. A selected anode of either silver or molybdenum produces characteristic K lines used for diffraction. The X-ray beam passes through a pinhole collimator and is incident on the sample with an approximately 2-mm by 5-mm spot and 1-width-half-maximum angular divergence. Coherent scattering from the sample produces a Debye-Scherrer diffraction pattern on an image plate 75 mm from the polycrystalline sample surface. An experimental study of the polycrystalline structures of zirconium and tin under high-pressure shock loading has been conducted with single-pulse XRD. The experimental targets were 0.1-mm-thick foils of zirconium and tin using 0.4-mm-thick vitreous carbon back windows for shock-loading, and the shocks were produced by either Detasheet or PBX-9501 high explosives buffered by 1-mm-thick 6061-T6 aluminum. The diffraction patterns from both shocked zirconium and tin indicated a phase transition into a polymorphic mix of amorphous and new solid phases.