Particle-in-cell simulations of hot electron generation using defocused laser light in cone targets

The effects of defocusing a high intensity pulse of laser light on the generation of hot electrons in a cone are investigated using particle-in-cell simulations. The results indicate that defocused laser light can soften the electron energy spectrum and increase the coupling efficiency compared to the use of a laser in tight focus. It is shown that this is a consequence of the density profile of plasma produced by the laser prepulse, which is less dense in the case of the defocused laser. The relevance of this result to fast ignition inertial confinement fusion is discussed.