Energy measurement of laser-accelerated protons by using a nuclear emulsion

The purpose of this study is measuring energy of laser-accelerated protons from the hydrogen cluster target by using a nuclear emulsion, and crosschecking the results of CR-39 detectors. The CR-39 detectors, which are the most sensitive solid state nuclear track detectors (SSNTD), have been used for long time to understand the both of spatial distributions and energy spectra of laser-accelerated ions. In such a situation, we have studied the applicability of a nuclear emulsion as the alternative ion detector for laser-accelerated ions. In the laser-driven ion acceleration experiments, not only ions, but also copious energetic electrons and X rays are simultaneously generated. Threfore, to suppress the background noise signals from the electrons and X rays, pH level of the developer and the development time of a nuclear emulsion are optimized. As a result, we have for the first time succeeded in identifying the signals from laser-accelerated protons up to 11.5 MeV and obtained an energy spectrum. The spectrum shows a good agreement with that obtained by CR-39.第2回QST国際シンポジウ