78 / 2025-03-12 10:03:35

The origins of hot electron generation in planar target hybrid drive experiments at SG-100kJ Facility

laser plasma interaction，two-plasmon-decay instability，hot electrons generation，non-eigenmode

Analysis of the contributions of suprathermal electrons and Stimulated Raman Scattering (SRS) in the planar target hybrid drive experiments within half-cylinder hohlraum indicates that the primary mechanisms for the generation of suprathermal electrons might be the side-scatter of directly driven beams and two-plasmon decay (TPD). Particle-in-cell simulations of SRS and TPD processes near the quarter-critical density surface reveal that the conversion efficiency of TPD to suprathermal electrons is significantly higher than that of SRS. This leads to the conclusion that in half-cylinder hohlraum planar target hybrid drive experiments, TPD is the primary source of suprathermal electrons, followed by SRS. The simulations also study the anomalous absorption of lasers at the quarter-critical density surface under hybrid drive high intensities, establishing a scaling law for TPD anomalous absorption, which can be incorporated into radiation-hydrodynamic codes to account for direct-drive beam TPD effects. Further studies on the scaling relationship of TPD to suprathermal electron conversion efficiency result in a novel scaling law model for TPD suprathermal electrons, consistent with simulations and experiments. This model can be applied to radiation-hydrodynamic simulations to consider the transport and preheat effects of suprathermal electrons. Based on the current simulation-derived scaling laws for high-intensity TPD anomalous absorption and suprathermal electrons, further simulations and experimental data across various parameter spaces are required to validate and refine the model, enhancing its applicability, such as considering the effects of laser beam width, speckle effects on SRS, and the competitive mechanisms between SRS and TPD in three dimensions.