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The absolute efficiency of a plastic scintillator neutron counter has been measured as a function of bias at thirteen neutron energies between 1.0 and 200 MeV, using two techniques: above 4 MeV, protons from free np charge exchange were used to tag a neutron beam, while below 4 MeV the tagged neutrons came from a 252Cf fission source. Data is available for biases between 0.20 and 4.0 MeV electron equivalent. A Monte Carlo program was written to interpolate the measurements to different neutron energies and extend them to other counter geometries. A comparison of the results of the program with our measurements and those of others is presented.

The design and performance of an array of plastic scintillator neutron counters are discussed. The array uses counters of three sizes to detect neutrons of 1.0 to 450 MeV, measuring their energy by time-of-flight and their production angles by counter identification and end-to-end timing. Information from 180 000 neutron-proton charge exchange events is used to investigate the resolution stability and internal consistency of the system. Neutron pulse height distributions for narrow bins of neutron energy between 1.25 and 313 MeV are presented and compared with the predictions of a Monte Carlo program.