Blast wave diagnostic for the Petawatt laser system

We report on a diagnostic to measure the trajectory of a blast wave propagating through a plastic target 400 μm thick. This blast wave is generated by the irradiation of the front surface of the target with ∼400 J of 1 μm laser radiation in a 20 ps pulse focused to a ∼50 μm diameter spot, which produces an intensity in excess of 1018 W/cm2. These 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 travels approximately radially outward from the interaction region. We have utilized streaked optical pyrometry of the blast front to determine its time of arrival at the rear surface of the target. Applications of a self-similar Taylor–Sedov blast wave solution allows the amount of energy deposited to be estimated. The experiment, LASNEX design simulations and initial results are discussed.