Laser-produced collimated proton beam by a tailored thin foil target

A thin-foil tailored hole target is proposed for an efficient production of a collimated proton beam in a laser target interaction. The tailored target has holes at the target surface. When an intense short pulse laser illuminates the thin foil hole target, transverse edge fields of an accelerated electron cloud and a proton source cloud are shielded by a protuberant part of the hole so that the proton beam divergence is suppressed. This paper presents a robustness of the hole target against laser parameter changes, against a contaminant proton source layer and against a laser alignment error. The 2.5-dimensional PIC (particle-in-cell) simulations also present that a multiple-hole target serves a high energy efficiency of the proton beam generation. Recent researches in this field have demonstrated acceleration of ions to a high energy in an interaction between an intense laser pulse and a thin foil target. The ion beams are expected to be useful for basic particle physics, medical therapy, controlled nuclear fusion, high-energy sources and so on. The important issues of the ion beam production include a quality of the ion beam and an efficient energy convergence to the ion beam from the laser. This paper presents a new method for the efficient collimated proton beam in the laser foil interaction.