Energy loss of swift protons in liquid water and ethanol

Energy loss measurement has been performed for the first time for MeV energy hydrogen ions passing through a liquid jet target produced by our newly developed liquid-in-vacuum apparatus. Liquid jet targets of water and ethanol were ejected into vacuum through an aperture of 20 μm in diameter. Preliminary experimental results of energy loss spectra are reported. It was found that the energy loss of swift protons in liquids are slightly different from the conventional stopping power data obtained from the SRIM code. However, this discrepancy is possibly attributable to our incorrect estimation of the liquid jet diameter.