Accelerating Protons to Therapeutic Energies with Ultra-Intense Ultra-Clean and Ultra-Short Laser Pulses

摘要

Proton acceleration by high-intensity laser pulses from ultra-thin foils forhadron therapy is discussed. With the improvement of the laser intensitycontrast ratio to 10-11 achieved on Hercules laser at the University ofMichigan, it became possible to attain laser-solid interactions at intensitiesup to 1022 W/cm2 that allows an efficient regime of laser-driven ionacceleration from submicron foils. Particle-In-Cell (PIC) computer simulationsof proton acceleration in the Directed Coulomb explosion regime from ultra-thindouble-layer (heavy ions / light ions) foils of different thicknesses wereperformed under the anticipated experimental conditions for Hercules laser withpulse energies from 3 to 15 J, pulse duration of 30 fs at full width halfmaximum (FWHM), focused to a spot size of 0.8 microns (FWHM). In this regimeheavy ions expand predominantly in the direction of laser pulse propagationenhancing the longitudinal charge separation electric field that accelerateslight ions. The dependence of the maximum proton energy on the foil thicknesshas been found and the laser pulse characteristics have been matched with thethickness of the target to ensure the most efficient acceleration. Moreover theproton spectrum demonstrates a peaked structure at high energies, which isrequired for radiation therapy. 2D PIC simulations show that a 150-500 TW laserpulse is able to accelerate protons up to 100-220 MeV energies.