Hot electron scaling for two-plasmon decay in ICF plasmas

We present a parametric scaling of hot electron (HE) generation at quarter critical density from the two-plasmon decay process. The study is conducted with the laser plasma simulation environment code, considering Langmuir decay instabilities (LDI) and laser pump depletion in 2D. The parameter scan is conducted as a function of electron temperature, ion-electron temperature ratio, drive strength, and density scale length. The scaling shows an hot electron (HE) conversion fraction up to 40%, HE fluxes up to 6 similar to 1014 W=cm2, and average temperatures in the range of 30 to 100 keV. The electron angular distributions exhibit two main regions: the plasma bulk, characterized by homogeneous emission, up to energies of 30 similar to 60 keV depending on the individual laser-plasma conditions, and a HE tail after ' 50 similar to 60 keV. The midenergy electrons are homogeneously emitted toward the end of the plasma bulk and acquire energy through electron plasma wave (EPW) Landau damping from Langmuir wave collapse and LDI cascade. The HE tail has electrons emitted in the forward direction and at low divergence, due to turbulence and EPW Landau damping from multi-staged acceleration. Finally, the laser power transmitted through the quarter critical region reaches values from similar to 80% down to similar to 35% for increasing HE generation, with absorption due to EPW collisional damping in the range of similar to 10% similar to 35%.

Automated summary

We propose a parametric scaling method for hot electron (HE) generation, using laser plasma simulation and considering Langmuir decay instabilities (LDI) and laser pump depletion. By conducting a parameter scan, we find that the conversion fraction of HE can reach 40%, HE fluxes can reach 6x10^14 W/cm^2, and average temperatures range from 30 to 100 keV. The electron angular distributions exhibit two regions: plasma bulk with homogeneous emission up to energies of 30-60 keV, and a HE tail after 50-60 keV. The results provide insights into HE generation and transmission in laser plasma interactions.