80 / 2025-03-12 21:49:33

Intensity spikes dominate hot electron production in moderate-bandwidth laser plasma interactions

intensity spike,hot electron,two-plasmon decay,broadband

Suppressing detrimental hot electrons generated by laser-plasma instabilities (LPI) remains a critical challenge in achieving high-gain inertial confinement fusion (ICF). While broadband laser pulses are believed to suppress LPI by disrupting matching conditions, recent experiments on the Kunwu broadband laser facility revealed consistent, counterintuitive enhancements of hot electron energy under moderate bandwidth conditions. This raises key questions about the mechanisms driving hot electron amplification and the specific broadband laser characteristics most effective in mitigating LPI. Addressing these questions, we report theoretical and numerical studies on hot electrons generated by two-plasmon decay (TPD), a major LPI, under various bandwidth schemes. Our findings attribute the enhanced hot electron production to intensity spikes in the wave fields, with similar effects for well-above-threshold and near-threshold cases. Statistical analysis of spike heights and numbers qualitatively explains variations in hot electron energy across different broadband schemes. Preliminary simulation results reveal that the overlapping of multiple broadband laser beams effectively weakens intensity spikes, leading to a subsequent reduction in hot electron energy. These results establish practical guidelines for optimizing laser conditions to suppress hot electrons, offering valuable insights for the design of future ICF lasers.