Measurement of 14.1 MeV neutrons with a Th-scintillator optical fibre detector

The flux of 14.1 MeV neutrons was measured with high spatial resolution in the vicinity of the target of a D–T neutron generator. The measurements were made by a thin optical fibre detector with a ZnS(Ag) scintillation tip mixed with a 232Th neutron converter. The detector concept was originally developed at Nagoya University. The flux of 14.1 MeV neutrons could be measured with a spatial resolution of about 1 mm. The position of the impact area of the deuterium beam on the target surface was determined by the method as an application. A simple model for the calculation of the space dependence of the flux was developed, and it was shown to agree very well with the measurements. With the help of the model, both the vertical and horizontal position of the beam impact area centre can be determined from one single measurement through parameter fitting.