Fast-Neutron Collimator Studies. The TSF-SNAP Core Mapping Collimator

The Monte Carlo technique has been used to determine some general properties of fast-neutron collimators for the cases in which the sources and detectors were finite disks. Based on these results, a collimator was designed to be used in determining the angular- and spatial-dependent neutron leakage spectrum from the TSF-SNAP reactor with a minimum distortion of the measured results. The detector-collimator response functions were then calculated for use in a separate Monte Carlo calculation of the leakage from the SNAP core. The adequacy of the response functions was determined by comparing the measured and calculated values of detector counts for a number of PoBe source locations off the axis of the collimator.