Proton beam quality improvement by a tailored target illuminated by an intense short-pulse laser

Suppression effect of proton beam divergence is numerically demonstrated in a tailored thin foil target with a hole at the opposite side of laser illumination. When an intense short pulse laser illuminates the thin foil target with the hole, edge effects of an accelerated electron cloud and an ion source cloud are eliminated by a protuberant part of the hole: the edge effects of the electron and ion-source clouds induce the proton beam divergence. Therefore the transverse proton beam divergence was suppressed well. In this study, we present the robustness of the hole target against laser parameter changes in a laser spot size and a laser pulse length, against a contaminated proton source layers, the laser alignment error, and the target positioning error by using particle-in-cell simulations.