Study of strain propagation in laser irradiated silicon crystal by time-resolved diffraction of K-α x-ray probe of different photon energies

摘要

An experimental study on the time resolved x-ray diffraction from laser shocked silicon crystal, carried out using a 10 TW Ti:sapphire laser system, is presented. The characteristic K_α x-ray line radiation generated by 45 fs laser produced plasmas of two different target materials (iron and copper) is used as the probe, whereas the stretched pulse of sub-nanosecond duration (pump), derived from the same laser, is used to compress the sample. The use of x-ray probe of different photon energies yields information about the strain over a greater crystal depth. The dynamics of the strain propagation is inferred by monitoring the evolution of rocking curve width of the shocked sample at different time delays between the pump and the probe pulse. The shock velocity deduced from these measurements is ~10~6cm/s, consistent with the sound velocity in bulk silicon. The maximum elastic compression observed is 0.4%, indicating a pressure of 0.8 GPa.