Oxford Centre for High Energy Density Science (OxCHEDS)

Abstract:

Multikilobar transient strains were produced in single-crystal silicon by laser irradiation. Variations of the lattice spacing with time and in depth were observed by pulsed X-ray diffraction. Targets were (111) silicon wafers, overcoated with 1000-angstrom aluminum to provide a short laser absorption depth, and further overcoated with a 25- mu m plastic layer. The temporal development of pressure pulse was observed by measuring the change in interplanar spacing of the (111) silicon planes, using the technique of pulsed X-ray Bragg diffraction. Peak lattice compressions (strains) were directly measured and lattice stress inferred as a function of irradiance and time. The compression was followed from its initial rise on through its crest and subsequent fall to values near, but above, solid density. Linear compressions of up to 4% were measured. Crystallinity was preserved throughout this process.