Effects of preplasma scale length and laser intensity on the divergence of laser-generated hot electrons.

We report on a numerical study of the effects of preplasma scale length and laser intensity on the hot-electron (≥1 MeV) divergence angle using full-scale 2D3V (two dimensional in space, three dimensional in velocity) simulations including a self-consistent laser-plasma interaction and photoionization using the particle-in-cell code LSP. Our simulations show that the fast-electron divergence angle increases approximately linearly with the preplasma scale length for a fixed laser intensity. On the other hand, for a fixed preplasma scale length, the laser intensity has little effect on the divergence angle in the range between 10(18) and 10(21) W/cm(2). These findings have important implications for the interpretation of experimental results.