Gamma rays associated with neutron scattering in fusion reactor materials

Abstract

The gamma-rays produced by the inelastic scattering of 14 MeV neutrons. in
fusion reactor materials have been studied using a gamma-ray spectrometer
employing a sodium iodide scintillation detector. The source neutrons are
produced by the T(d,n)4He reaction using the SAMES accelerator at the University
of Aston in Birmingham. In order to eliminate the large gamma-ray background
and neutron signal due to the sensitivity of the sodium iodide detector to neutrons, the gamma-ray detector is heavily shielded and is used together with a particle time of flight discrimination system based on the associated particle time of flight method. The instant of production of a source neutron is determined by
detecting the associated alpha-particle enabling discrimination between the
neutrons and gamma-rays by their different time of flight times. The electronic
system used for measuring the time of flight of the neutrons and gamrna-rays over the fixed flight path is described.
The materials studied in this work were Lithium and Lead because of their
importance as fuel breeding and shielding materials in conceptual fusion reactor
designs. Several sample thicknesses were studied to determine the multiple
scattering effects. The observed gamma-ray spectra from each sample at several
scattering angles in the angular range Oº - 90° enabled absolute differential
gamma-ray production cross-sections and angular distributions of the resolved
gamma-rays from Lithium to be measured and compared with published data. For the Lead sample, the absolute differential gamma-ray production cross-sections for discrete 1 MeV ranges and the angular distributions were measured.
The measured angular distributions of the present work and those on Iron from previous work are compared to the predictions of the Monte Carlo programme M.O.R.S.E. Good agreement was obtained between the experimental results and the theoretical predictions. In addition an empirical relation has been constructed which describes the multiple scattering effects by a single parameter and is capable of predicting the gamma-ray production cross-sections for the
materials to an accuracy of ± 25%.

Date of Award	May 1984
Original language	English
Supervisor	A.J. Cox (Supervisor)