Laser acceleration of protons from thin film targets

Abstract

A collimated beam of fast protons, witlr energies as high as 10 MeV and total number of 109,109, confined in a cone angle of 40°±10°40°±10° has been observed when a 10 TW laser with frequencies either ω0ω0 (corresponding to 1 μm) or 2ω02ω0 was focused to an intensity of a few times 1018 W/cm21018W/cm2 on the surface of a thin film target. The protons, which originate from impurities on the front side of the target, are accelerated over a region extending into the target and exit out the backside in a direction normal to the target surface. Acceleration field gradients of ∼10 GeV/cm are inferred. The maximum proton energy for 2ω02ω0 can be explained by the charge-separation electrostatic-field acceleration due to “vacuum heating.” In other set of experiments when a deuterated polystyrene layer was deposited on a surface of a Mylar film and a 10B10B sample was placed behind the target, we observed the production of ∼ 105∼105 atoms of positron active isotope 11C11C from the nuclear reaction 10B(d,n)11C.10B(d,n)11C. © 2001 American Institute of Physics.