Prof Peter Norreys FInstP;

Abstract:

Measurements of proton emission have been made from a variety of solid targets irradiated by a 60-fs, 200-mJ, 7 x 10(18)-W cm(-2) laser system operating at 2 Hz. Optimum target conditions were found in terms of target material and thickness. For Mylar targets of thickness 20-40 microm, a maximum proton energy of 1.5 MeV was measured. For aluminum targets, a maximum energy of 950 keV was measured for 12 microm, and for copper, 850 keV for 12.5 microm.

Abstract:

Experiments were performed to distinguish between the origin of various structures present in the energetic proton signal at the rear of the target in high power laser-solid interactions. Three distinct proton populations that contribute to the signal observed on the detectors were identified.

Abstract:

The characterization of multiterawatt laser-solid interactions for proton acceleration was discussed. The stages of ionization of a target gas was investigated using time-of-flight spectrometer. Results showed a factor of 1.5 uncertainity in the focused intensity when ion yields were measured with predictions of an atomic tunneling ionization. A maximum proton energy of 1.5 MeV was also observed.