Associated Particle Measurements of (n,p) and (n,α) Cross-Sections using the D-D Reaction

Abstract

This thesis includes a discussion of the design criteria used in constructing a stigmatic focussing magnetic analyzer for the purpose of improving the resolution of recoiling 3He particles from the D(d,n)3He reaction produced in a thick target. The greatly improved resolution of 3He particles detected in the image plane of this analyser with a surface barrier detector enables accurate flux measurements of the associated neutron beam to be made even where the recoil particles are emitted at backward angles, and consequently neutron beams can now be generated over a range of neutron energy while still retaining the precision of the associated particle method. In addition fast coincidence experiments with nanosecond timing resolution can be made. Since the angular position and energy of a neutron beam defined by the associated particle method are important in cross-section experiments the stability of these parameters is investigated. In the case where the D-D target is formed by the drive-in mechanism this investigation has lead to a model which predicts the changes that occur in the neutron beam profile during the period when the target media is saturating with deuterium implanted by the incident deuteron beam. A detailed account is given of the experimental method used in studies made of the (n,p) and (n,α) total cross-sections of 39K and 40Ca, over the neutron energy range from 2.4 to 2.9 MeV, using a KI(Tl) and a CaF2(Eu) crystal respectively as the neutron target. Tabulated cross-sections are given, and these are compared with earlier data.