PIC simulation of laser-driven particle acceleration

It is shown by PIC simulations that the highest proton energy gain is achieved at a certain incidence angle. In addition, the proton beam energy spread can be reduced by adjusting the laser pulse irradiating position on the target. This is shown for proton acceleration by a laser pulse obliquely incident on a double layer target. The proton beam propagates at some angle with respect to the target surface normal as determined by the proton energy and the incidence angle. The high energy protons are found to come from an area shifted from the initial target center towards the propagation direction of the laser pulse. (author)