Measurement of proton jet in the interaction of ultra-short ultra-intense laser with Cu foil target

This paper reports the experimental research on the interaction of ultra-short and ultra-intense laser with Cu foil target. The spatial distributions and yield of the protons with different target thicknesses were recorded by nuclear track detector CR39. And the proton energy spectrum was measured by Thomson magnetic spectrometer. The results show that about 105-106 high energy protons jet only in the direction normal to the surface of target within a little cone angle. A sharp cutoff energy exists in the proton energy spectrum, and it depends on the target thickness. (authors)