Study of a B-10+ZnS(Ag) neutron detector as an alternative to He-3-based detectors in Homeland Security

摘要

The response of a scintillation neutron detector of ZnS(Ag) with B-10 was calculated, using the MCNPX Monte Carlo Code. The detector consists of four panels of polymethyl methacrylate (PMMA) and five thin layers of similar to 0.017 cm thick B-10+ZnS(Ag) in contact with the PMMA. The response was calculated for the bare detector and with different thicknesses of High Density Polyethylene, HDPE, moderator for 29 monoenergetic sources as well as (AmBe)-Am-241 and Cf-252 neutrons sources. In these calculations the reaction rate B-10(n, alpha)Li-7 and the neutron fluence in the sensitive area of the detector B-10+ZnS(Ag) was estimated. Measurements were made at the Neutron Measurements Laboratory, Universidad Politecnica de Madrid, LMN-UPM, to quantify the detections in counts per second in response to a Cf-252 neutron source separated 200 cm. The MCNPX computations were compared with measurements to estimate the efficiency of ZnS(Ag) for detecting the a that is created in the B-10(n, alpha)Li-7 reaction. After validating new models with different geometries it will be possible to improve the detector response trying to achieve a sensitivity of 2.5 cps-ng(252)Cf comparable with the response requirements for He-3 detectors installed in the Radiation Portal Monitors, RPMs. This type of detector can be considered an alternative to the He-3 detectors for detection of Special Nuclear Material, SNM. (C) 2016 Elsevier Ltd. All rights reserved.