Energy and angle straggling effects in a D(d, n) 3He neutron source using a gas target

Abstract

The angular dependence of the energy width of neutrons produced in gas targets via the reaction D(d, n) 3He has been investigated by analytical approximation, Monte Carlo simulations and time-of-flight (tof) experiments. The effective energy width ΔE p (fwhm) of the projectiles is calculated on the basis of the Bethe-Bloch stopping power formula and appropriate models for the energy straggling. The angular dependent neutron tof-width is also sensitive to the angle straggling parameter Δϑ n (fwhm). The experimental data for various projectile energies and target entrance foils confirm numerical calculations using extended theories for the multiple small angle scattering in the entrance window of the gas target. The angle straggling parameter was determined with an uncertainty of 5%. As the reaction is strongly pronounced in the forward direction, this angle straggling must be considered in the analysis of neutron scattering experiments as well as in absolute neutron fluence measurements.