Blast wave diagnostic for the Petawatt laser system

We report on a diagnostic to measure the trajectory of a blast wave propaga ting through a plastic target 400 mu m thick. This blast wave is generated by the irradiation of the front surface of the target with similar to 400 J of 1 mu m laser radiation in a 20 ps pulse focused to similar to 50 mu m d iameter spot, which produces an intensity in excess of 10(18) W/cm(2). Thes e conditions approximate a point explosion and a blast wave is predicted to be generated with an initial pressure nearing 1 Gbar which decays as it tr avels approximately radially outward from the interaction region. We have u tilized streaked optical pyrometry of the blast front to determine its time of arrival at the rear surface of the target. Applications of a self-simil ar Taylor-Sedov blast wave solution allows the amount of energy deposited t o be estimated. The experiment, LASNEX design simulations and initial resul ts are discussed. (C) 1999 American Institute of Physics. [S0034-6748(99)58 301-9].