Efficiency of a BaF, scintillator detector for 15-150 MeV neutrons

BaF, scintillator detectors are now in common use for the measurement of y-rays over a wide energy range because of the relatively high detection efficiency and the fast response which allows subnanosecond timing [1,2]. The BaF, scintillation light consists primarily of two components with decay times of or = 600 ps and TV = 620 ns [2], and the ratio of the intensities associated with each of these components is sensitive to the incident radiation type [3]. One particularly interesting feature of BaF, detectors is that it is possible to distinguish neutron-induced interactions from -y-ray interactions for relatively high energy neutrons (E, > 10 MeV) using pulse shape discrimination (PSD) techniques [4,6]. This separation is thought to result from neutron reactions in the BaF, which emit light charged particles (p, d, 4He, ) in contrast to y-rays which interact primarily through electrons [4]. The n/y pulse shape discrimination coupled with the good timing properties make BaF, a potentially attractive neutron detector. Unfortunately, there is very little information currently available regarding the neutron efficiency of BaF,, in contrast to the situation with standard organic scintillators such as NE213 where computer codes are commonly available to calculate detector efficiencies over a wide range of neutron energies [5]. In fact, only two BaF, neutron efficiency measurements have been reported for neutron energies above 10 MeV [4,6]. Matulewicz et al. [4] measured the BaF, neutron efficiency for neutron energies up to 22 MeV, but they did not employ neutron/y pulse-shape discrimination. In the second paper, Kubota et al. [6] reported the neutron efficiency of a BaF, detector for neutron energies between 15 and 45 MeV after impos-