ABSTRACT
The localisation of an unknown neutron source in various bulky homogeneous media was studied. For the planar case two (3)He detectors on the opposite faces of a box were used. It is shown that the location of a single small neutron emitting source in a large box can be found to a better than 7% by using two neutron detectors positioned on parallel faces of the box, coplanar with the source. The localisation requires measurement of the count rate of both the unknown source (ratio of the count rates of the two detectors is R(x)) and an extra source positioned on one of the faces of the box (ratio of the count rates of the two detectors R(0)). The location of the neutron source is found according to the equation. (formula see text). The localisation is based on the finding that the ratio of the count rates of the two detectors is an exponential function of the distance of the source from one of the detectors.
Subject(s)
Algorithms , Models, Chemical , Neutrons , Radiometry/methods , Computer Simulation , Radiation Dosage , Scattering, RadiationABSTRACT
The possibility of localisation of an unknown neutron source in various bulky homogeneous media (box) was studied. Previous study showed that for the planar case, neutron source could be localised with accuracy better than 7%, by using the count rates ratio of two (3)He detectors, positioned on the opposite faces of the box. The influence of the deviation of the source from the virtual plane connecting the two (3)He detectors was studied. It was found that for detectors placed on the centres of the sample faces, larger distance of the source from the central line leads to larger error, up to 15%. It was found that while using the measurement of the ratio R(0) of external source placed on the box face coplanar with unknown source, accuracy does not depend on the distance from central line. Different ways to determine the plane of the unknown source were investigated. It was found that it is impossible to determine it by looking for maximum count rate of one detector or geometric mean of a pair of detectors. The experimental results were confirmed with Monte-Carlo N-particle (MCNP) simulations.
Subject(s)
Algorithms , Models, Chemical , Neutrons , Radiometry/methods , Computer Simulation , Radiation Dosage , Scattering, RadiationABSTRACT
Validity of the model of a virtual point detector (implying existence of a point where all interactions virtually occur) was confirmed for measurements of radioactive disk sources with HPGe detectors. The existing correlation of the count rates with the distance between the virtual plain detector and the detector face makes it possible to inter- and extrapolate calibration curves for disk radioactive sources for use at different source-detector face distances. The dependence of the distance between the virtual plane detector and the detector face on the photon energy was studied for sources of various radii.
