Multiple Scattering Correction for Proton Ranges and the Evaluation of theL-Shell Correction andIValue for Aluminum

Multiple scattering corrections to proton range-energy measurements are discussed. Curves are plotted which give the fractional transmission of protons through a finite thickness of stopping material as a function of the initial proton energy and for various values of the ratio of the straggling and multiple scattering parameters. An application of these results to particular experimental situations shows that the Moli\`ere multiple scattering distribution gives a nearly correct representation of the experimental data on transmission and that a simple exponential distribution is not satisfactory. The case of straggling in gold is discussed in detail. Application of the results to the experimental range-energy relation in aluminum for protons of energy lying between 1 and 20 Mev is made. The experimental ranges can be described consistently with a mean excitation potential $I=163$ ev and with reasonable values of the L-shell binding energy correction.