Hot Electron Generation and Laser–Plasma Instabilities in Shock Ignition Relevant Experiments

Abstract

Shock ignition (SI) is an inertial confinement fusion schema that uses a strong convergent shock driven by a high intensity ~10 16 W/cm 2 laser pulse to ignite a pre-compressed fusion capsule. Understanding nonlinear laser-plasma instabilities and hot electron generation is critical towards maximizing the coupling of laser energy into the target during both the high intensity and plasma formation pulses. A series of experiments on the OMEGA EP and OMEGA-60 laser facilities have explored a variety of regimes relevant to shock ignition, with experimental parameters informed iteratively by radiation hydrodynamic simulations and previous experiments. Characterization of a coronal plasma with and without a sequential high intensity pulse was performed utilizing Thomson scattering on OMEGA 60 at variable focal standoff from the initial target surface between 300 – 1100 μm, corresponding to plasma densities between n crit to n crit /10. High intensity laser coupling was additionally studied using backscatter spectrum diagnostics. Derived results will be presented and compared to hydrodynamic simulation results. In addition, simultaneously collected shock breakout measurements are presented using VISAR and SOP diagnostic techniques and are additionally compared to expectations. Such validations of simulation results will aid to inform future experiments conducted in this regime, while the data reveals further insights into the underlying dynamics pivotal to the shock ignition concept.\