A collimated beam of fast protons, with energies as high as 1.5 MeV and total number of ≿ 109, confined in a cone angle of 40° ± 10° is observed when a high-intensity high-contrast subpicosecond laser pulse is focused onto a thin foil target. The protons, which appear to originate from impurities on the front side of the target, are accelerated over a region extending into the target and exit out the back side in a direction normal to the target surface. Acceleration field gradients ˜ 10GeV/cm are inferred. The maximum proton energy can be explained by the charge-separation electrostatic-field acceleration due to “vacuum heating.”.
ASJC Scopus subject areas
- Physics and Astronomy(all)