Interferometric measurement of preheating in laser shocks

We present a preliminary study of preheating in laser shocks using an interferometric diagnostic. A low energy probe laser divided in two by a biprism produces an interference pattern on the rear side of a target. The expansion due to preheating causes a fringe shift before shock arrival. A streak camera produces time-resolved images of the target rear side, which are filtered to reduce noise and correct for instrumental effects. Results are compared with an analytical model, which assumes that preheating is due to x rays, and with results from reflectivity measurements.