POTENTIAL AND LIMITATIONS OF SEVERAL NEUTRON COINCIDENCE EQUIPMENTS
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON
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Coincident neutron detectors which can distinguish between neutrons occurring as a result of fission and those due to alpha, n or Gamma, n nuclear reactions have been described in a preceding report. The report discusses several methods of developing follow-on equipments with greater potential for the nondestructive assay of plutonium samples. The effect on equipment performance of the efficiency and neutron lifetime in the neutron detector and of analysis gate length and equipment dead times are treated in considerable detail and several illustrative examples are presented. Performance is generally improved by an increase of neutron efficiency accompanied by a decrease in neutron lifetime and the use of optimized analysis circuitry. Good performance can be obtained with complex 4 pi moderating detectors which employ an array of enriched BF3 or 3He neutrons detection tubes dispersed in a hydrogeneous moderator.