Hot Electron Distributions from Ultra_Intense Laser Solid Interactions

Summary form only given. Experimental data of electron energy distributions from ultra-intense (>10¹⁹ W/cm²) laser-solid interactions using a petawatt laser containing >300 Joules are presented. Clear signatures for the existence of three populations of energetic electrons, all with distinct effective temperatures, are seen in the spectra. We present simulations and theoretical calculations that explain all three components. We find that the high energy component (~10 MeV) is consistent with a modified form of SRS forward scattering of the main pulse in the long scale length, low density plasma exists in front of the solid. The moderate energy component (~1 MeV) is consistent with the ponderomotive heating from the main pulse near the critical density. The low energy component (~100 keV) is consistent with the fact that laser energy in a halo about the focused spot also generates ponderomotive heating intensity, with reduced intensity