Experimental characterization of hot electron emission and shock dynamics in the context of the Shock Ignition Approach to Inertial Confinement Fusion

Abstract : We report on planar target experiments conducted on the OMEGA-EP laser facility performed in the context of the Shock Ignition (SI) approach to inertial confinement fusion. The experiment aimed at characterizing the propagation of strong shock in matter and the generation of hot-electrons (HE), with laser parameters relevant to SI (1-ns UV laser beams with I ∼10 16 W/cm 2). Time-resolved radiographies of targets were performed in order to study the hydrodynamic evolution. The hot-electron source was characterized in terms of maxwellian temperature T h and laser to hot-electron energy conversion efficiency η using data from different x-rays spectrometers. The post-processing of these data gives a range of possible values for T h and η (i.e. T h [keV] ∈ [20,50] and η ∈ [2%,13%]). These values are used as input in hydrodynamic simulations to reproduce the results obtained in radiographies, thus constraining the range for the HE measurements. According to this procedure, we found that the laser converts ∼10% ±4% of energy into hot-electrons with T h = 27 keV ±7 keV. Such electrons have enough low temperature that they should not be a prehaeat concern in SI.