J. D. Anderson

Hydrogen and helium production cross sections for 15-MeV neutrons on types 316 and 304 stainless steel

Hydrogen and helium production cross sections have been measured for 15-MeV neutrons incident on Types 316 and 304 stainless steel. A charged-particle magnetic-quadrupole spectrometer was used to measure the (n,xp), (n,xd), and (n,x..cap alpha..) cross sections and the charged-particle spectra. The measured gas production cross sections, 260 +- 38 mb for hydrogen and 48 +- 7 mb for helium, differ by as much as 73 percent from those used in previous assessments of candidate materials for fusion reactors. The energy spectrum of recoil nuclei from (n,x..cap alpha..) reactions, deduced here directly from the alpha-particle spectra, also differs from calculated spectra used in predicting displacement damage.

A New Method for Estimating Neutron Reaction Cross Sections Based on Wick’s Limit

Wick’s limit is an inequality that relates the zero‐degree differential elastic scattering cross section to the total cross section. The deviation of Wick’s limit from an exact equality is small over a wide range of incident energies and target masses. Under these circumstances we show that Wick’s limit can be used to correlate the uncertainties in the two terms of the reaction (nonelastic) cross section expressed as the difference between the total and angle‐integrated elastic cross sections. When suitable elastic angular distributions are available, we show that the reaction cross section may be obtained with small errors (typically 1.5–3%). Examples are shown for 208Pb, 54–56Fe, 232Th, and 238U.

Comparison of Ramsauer and Optical Model Neutron Angular Distributions

Abstract In a recent paper it has been shown that the nuclear Ramsauer model does not do well in representing details of the angular distribution of neutron elastic scattering for incident energies of <60 MeV for 208Pb. In this paper, we show that the default angular bin dispersion most widely used in Monte Carlo transport codes is such that the observed differences in angular shapes are on too fine of a scale to affect transport calculations. The effect of increasing the number of Monte Carlo angle bins is studied to determine the dispersion necessary for calculations to be sensitive to the observed discrepancies in angular distributions. We also show that transport calculations are sensitive to differences in the elastic-scattering cross section given by recent fits of 208Pb data compared with older fits.