Measuring energy spectra of proton generated by 100 TW laser-plasma interaction at rear side of target

In the experiment of 100 TW laser interacting with 5 μm thick Cu target, CR39 and Thomson spectrum are used to detect the energy spectra of proton and radiochromic HD810 is used to detect the distribution of protons at the normal direction of the target's back. The results show that the protons are emitted from the normal direction of target-back and have 570 keV cut-off energy and the jet angle is about 10 degree. The results of the experiment verify that target normal sheath acceleration of proton in the ultra-short and ultra-intense laser interacts with plasmas. (authors)