Large volume neutron detectors with subnanosecond time dispersions

Abstract

Design criteria and performance characteristics are described for large-volume (13.1 1 to 118 1) mean-timed plastic-scintillator detectors for neutrons from ≈2 MeV to 2 GeV. Detectors were constructed in six sizes (all 0.102 m thick) from 0.126 m × 1.016 m × 0.102 m to 0.762 m × 1.524 m × 0.102 m. Overall energy resolutions of 230 keV for 80 MeV neutrons, 320 keV for 133 MeV neutrons, and 440 keV for 157 MeV neutrons were achieved in time-of-flight experiments with flight paths of 76, 68, and 91 m, respectively. The detectors have pulse-height responses uniform to ±5% except close to the ends, position resolutions less than 5 cm, and intrinsic time dispersions less than 400 ps. Typical neutron detection efficiencies are 20% for 20 MeV neutrons at a pulse-height threshold of 2 MeV equivalent-electron energy (MeV ee) and 3.5% for 200 MeV neutrons at a pulse-height threshold of 50 MeV ee.