Comparisons of predictions from two intranuclear-cascade models with measured secondary proton spectra at several angles from 62 - and 39 - MeV protons on various elements

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Abstract
Detailed comparisons of correlated energy-angle proton spectra corresponding to continuum state transtions have been made between experimental data and two versions—Brookhaven National Laboratory (BNL) and Oak Ridge National Laboratory (ORNL)—of the intranuclear-cascade model for 62- and 39-MeV protons incident on carbon, iron, and bismuth. These energies were selected because detailed experimental data are available and because the energy limit of validity of the intranuclear-cascade approach could be examined. The calculated spectra are in good agreement (≤ 30%) with the shapes and magnitudes of the measured integral spectra for the 62-MeV reactions. However, the comparisons of the spectra at angles ≤ 20° and > 90° are poor. There is a much greater discrepancy in the correlated energy-angle data from reactions at 39 MeV. The BNL version, which contains the greater physical detail, tends to reduce the discrepancies in the spectral shape at small and large angles between the experimental data and the simpler intranuclear-cascade version (ORNL). Examples of these discrepancies are: a high estimated quasifree peak at small angles and a small scattering intensity at back angles. However, the BNL version reduces the particle yield for heavy targets so that the comparisons of the predicted absolute cross sections with the experimental data are often poor. The effects of reflection and refraction, which are included in the BNL version only, appear to be in the right direction to compensate for the discrepancies of the ORNL version, but some modification in the manner that this phenomenon is incorporated may be required to avoid the discrepancies in absolute cross sections.