Laser acceleration system for generating monoenergetic protons

A controller for a proton acceleration system including a laser source generating a pulsed laser beam having a wavelength λL and intensity;

• and further including a target formed of foil which is irradiated by the laser beam and transformed into a plasma having a target density causing a treatment energy to be emitted from the foil due to the irradiation, wherein the controller comprising:
• a tangible processor;
• and
• a memory with instructions to be executed by the tangible processor for selecting a thickness of the foil of the target so that the foil has a thickness within a range of optimal thickness Δs to 2×Δs, wherein Δs is less than the laser wavelength and is a function of the laser intensity, laser wavelength, and target density sufficient to achieve radiation pressure acceleration (RPA).