Robustness of a tailored hole target in laser-produced collimated proton beam generation

The robustness of the hole target against laser parameter changes in a laser spot size and in a laser pulse length against a contaminated proton source layer and against a laser alignment error are described. The multiple-hole target is robust against a laser alignment error and a target positioning error and it has served as a robust target for practical uses to produce a collimated proton beam.