Laser-driven high-energy ion generation for a compact cancer therapy accelerator

We started a project to develop a very compact accelerator for cancer therapy. To reduce the size of the system, we adopted a laser plasma ion source using a compact ultra-high intensity laser. We have performed ion generation experiments in which the laser parameters were as follows: The wave length and the pulse duration were 800 nm and 50 fs, respectively. Peak power was 4 - 5TW. The laser pulse with normal incidence angle to the target was focused onto the target with 15 μm diameter giving power density of 3 - 4x1018W/cm2. The thin foil metals (Ti, Al) and plastics (polypropylene, polyethylene) with the thicknesses of 4 - 100 μm were used for targets. We found that the angular distribution of ions with an energy of ~0.1 MeV had a significant peak in the backward and forward in respect to the laser incidence direction.