Energetic proton production from relativistic laser interaction with high density plasmas

Energetic protons up to 30 MeV have been measured from high intensity laser interactions ${\text{(⩽5×10}}^{19} {\mathrm{W/cm}}^{\mathrm{2}})$ with solid density plasmas. Up to ${10}^{12}$ protons (> 2 MeV) were observed at the rear of thin aluminum foil targets and measurements of their angular deflection were made. Similar energies were measured from ions produced from the front of the foils. Nuclear activation and track detector measurements suggest that the protons measured at the rear originate from the front surface of the target and are bent by large magnetic fields that exist in the plasma interior, which are likely generated by a laser-produced beam of fast electrons.