Laser acceleration of protons from thin film targets

Abstract

Abstract.A collimated beam of fast protons, with energies as high as 10 MeV and total number of 10 9 , confined in a cone angle of 40°±10° has been observed when a 10 TW laser with frequencies either co 0 (corresponding to 1 Jim) or 2o) 0 was focused to an intensity of a few times 10 18 W/cm 2 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 2co 0 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 10