Comparison of neutron fluence spectra measured with NE213 proton recoil spectrometer and NE230 deuteron recoil spectrometer

Abstract

A (5 cm × 5 cm) cylindrical NE213 liquid organic scintillator and a (2.5 cm × 2.5 cm)cylindrical NE230 liquid organic scintillator were used as spectrometers. A series of measurements was made with both the NE213 and NE230 spectrometers, with the time-of- flight technique used for neutron energy selection. Pulse height spectra for quasi- monoenergetic neutron beams of ~5-64 MeV produced by bombarding either a (1 mm) lithium metal target, or a (10 mm) beryllium target, or a (10 mm) graphite target with 66 MeV proton beam were measured with both spectrometers. Deuteron events identified by pulse shape discrimination were selected for measurements with the NE230 spectrometer while proton events were selected for measurements with the NE213 spectrometer. Response of the scintillator to protons using NE213 and deuterons using NE230 were obtained from the measured pulse height spectra. Detector efficiency of the NE213 spectrometer as a function of neutron energy was determined for n-p elastic scattering. The detector efficiency of the NE230 was determined relative to the well-known efficiency of the NE213 spectrometer, selecting either all or n-d elastic events in the pulse height spectra measured with the NE230 spectrometer. The detection efficiency of the NE230 spectrometer was also determined from the available cross-section for n-d elastic scattering as exploratory work. Neutron fluence spectra could be determined using the appropriate neutron detection efficiency for each spectrometer and were compared with each other. The results showed good comparison and encouragement demonstrating the reliability of neutron fluence spectral measurements withthe NE230 spectrometer using the time-of-flight technique.