Collimation of fast electron beams by strong external magnetic field in laser-solid interaction using Monte Carlo simulation

In this paper, the effect of the external magnetic field on the fast electron beam angular spread and spatial divergence in laser-solid interaction were investigated and energy deposition of these electrons into the high-density fuel was evaluated using Monte Carlo simulation by Geant4 simulation toolkit. In our simulation, two types of the energy distribution function, exponential energy distribution, and quasi-two temperature energy distribution function, for electrons were considered. Our simulations in the presence of an external magnetic field B-ext = (0- 10) kT show that the dynamics and spatial divergence of the high energy electrons are strongly affected by the external magnetic field. It was shown that in the case with the two-temperature energy distribution, the number of electrons (electron number density) with a large angular spread in the momentum space which were trapped by the magnetic fields lines and collimated toward the fuel were more populated than that of the exponential function. Comparison of the results indicate that the acceptable condition is obtained for the density rho(c) similar to 300 g cm(-3) in the presence of a magnetic field of about B-ext similar to 1- 2 kT with a laser wavelength lambda(if) = 0.35 mu m and laser intensity I = 10(21) Wcm(-2). It was presented that in the case with the sufficiently strong external fields, B-ext similar to 1- 2 kT, it seems that the optimal results for suppression of electron spatial divergence, electron beam collimation, and energy deposition rate are obtained.