A Study of the Gamma-Rays Associated with the Inelastic Scattering of Neutrons in Extended Target Samples

Abstract

The gamma-rays produced’ in the inelastic scattering of 14 MeV
neutrons have been studied using a gamma-ray spectrometer employing a
sodium iodide scintillation detector. The source neutrons are
produced by the T(d,n)"He reaction using the Radiation Centre Dynamitron
and.the SAMES accelerator. In order to overcome the large gamma-ray
background and large stray neutron signal due to the sensitivity of the
sodium iodide detector to neutrons, heavy shielding around the gamma-ray
detector 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 defined by detecting the
associated alpha-particle which enables discrimination between the
neutrons and gamma-rays because of their different time of flight times.
The electronic system used for measuring the time of flight of the
neutrons and gamma-rays over the fixed flight path is described.

The materials studied in this work were iron and concrete because
of their importance as structural and shielding materials in the
construction of both fission and fusion reactors. Several sample
thicknesses were studied to determine the multiple scattering effects
in large sample. The observed gamma-ray spectra from each sample
at several scattering angles in the angular range 0°-90° enabled
absolute differential gamma-ray production cross-sections and angular
distributions of the resolved gamma-rays from iron to be measured and
compared with published data where available. For the concrete sample,
the absolute differential gamma-ray production cross-sections for
discrete 1 MeV ranges and the angular distributions were measured and
compared with cross-sections synthesized from the published cross-section
data for the elements constituting concrete.

The number of gamma-rays produced from each sample in the angular
range studied were compared with the predictions of a theoretical model
based on the continuous slowing down model and Fermi-Age equation,
Good agreement between experiment and theory is obtained and a single
parameter found which describes the effects of multiple scattering
in both materials.

Date of Award	1981
Original language	English