Energy-Loss Straggling of Protons in Silicon

Abstract

The energy-loss straggling distributions for protons incident on a 200-μ silicon surface-barrier detector were measured in the energy region between 5 and 42 MeV. Experimental results were compared to the predictions of the Vavilov theory and found to be in excellent agreement at the higher energies. However, a systematic difference between theory and experiment was observed for proton energies less than 20 MeV, the discrepancy increasing with decreasing incident proton energy. This effect is due to appreciable variation of proton energy over the thickness of the detector. Tschalär's distribution functions, which specifically consider this variation, yield good fits to the data for energy losses as much as 80% of the incident proton energy.