In inertial confinement fusion implosions, the preheating risks associated with hot electrons generated by laser plasma instabilities (LPI) hinge on the angular characteristics of these hot electrons, given a specific total energy. Here we present our investigations on the angular variations of hot electrons generated from two-plasmon decay (TPD) instability, one of the major LPIs that produce hot electrons, driven collectively by dual laser beams with different incident angles θ_in to the plasma density gradient. Employing particle-in-cell simulations, our study reveals that the hot electrons spread widely in angle with side peaks at up to ∼ 72◦ to the density gradient when θ_in exceeds a threshold θ_th (40◦∼48◦ in our simulations), above which divergent hot electrons are effectively produced due to the growth of the common plasma waves shared by TPD and side stimulating Raman scattering (SRS). Conversely, the hot electrons exhibit narrow angular distributions peaked at ∼ 0◦ for all the θ­­_in < θ_th, albeit through different mechanisms characterized by the directions of common plasma waves. Interestingly, we find that two angularly divergent TPD daughter waves paired with the same common plasma wave can significantly produce collimated hot electrons by forming directional moving electric fields via interference, which occurs for moderate to large θ_in (∼40-55◦).
 

Two-Plasmon-Decay,common plasma wave,hot electrons,laser beam configurations