A high energy component of the intense laser-accelerated proton beams detected by stacked CR-39

A precise measurement has been made utilizing a stacked CR-39 detectors unit for laser-accelerated high intensity protons. The proton beams are derived from a thin polyimide target exposed to an high intense Ti:sapphire laser 8 J energy and 40 fs duration. The sample sets, stacked radiochromic film and CR-39 detectors covered with 13 μm aluminum filter, are irradiated under vacuum condition. By analyzing the etch pits on the last layer of CR-39 which recorded etchable tracks, the energies of each proton in high-energy region are evaluated more precisely than in the past. The residual ranges for each particle in the last layer has been obtained from etch pit growth curves with multi-step etching technique. The maximum energy of proton is 14.39 ± 0.05 MeV. This method allows us to measure the maximum energy of proton precisely, which can obtain high energy resolution with uncertainty ΔE = 0.1 MeV in the laser-driven particle acceleration experiment.

► Laser-driven particle acceleration, CR-39, etch pit growth curve. ► A precise measurement of laser-accelerated proton beams is demonstrated. ► We obtained up to the hundredth place of the energy in unit of MeV, 14.39 ± 0.05 MeV ► This method allows us to obtain high energy resolution with uncertainty ΔE = 0.1 MeV.