BC501A Liquid Scintillator Research Articles

Study of n-γ discrimination with NE213 and BC501A liquid scintillators of different size

A comparative study of n-γ discrimination by the digital charge comparison method was carried out for NE213 and BC501A scintillators of different size coupled to a 130 mm diameter XP4512B photomultiplier. Particularly, the scintillators of diameter 50 mm × 50 mm size are compared with those of 4 l volume (160 mm in diameter and 200 mm in depth). The figure of merit, M, of 3.81 measured with the diameter 50 mm × 50 mm BC501A scintillator at 1 MeV energy lost by recoil electrons, is much better than M of 2.05 as observed with the 4 l volume cell. This is the effect of the reduced photoelectron yield by about 50% determined for the 4 l volume scintillator. Moreover, the slowing down of the light pulse and multiscattering of neutrons have a further influence on the lowering of the M factor. The study of the M factor versus the initial delay and width of the gate set at the slow component showed that the early light of the slow component represented often by the intermediate component with the decay time constant of about 30 ns is of great importance for the n-γ discrimination. Particularly, for the 4 l volume cells it is sufficient to limit the width of the gate at the slow component to about 300 ns. The comparison of the NE213 and BC501A scintillators showed that the BC501A scintillator exhibits a larger light yield evidently observed for the 4 l volume cell and thus giving a better n-γ discrimination.

Identification of different reaction channels of high energy neutrons in liquid scintillators by the pulse shape discrimination method

A study of the n-γ discrimination with NE213 and BC501A liquid scintillators, carried out with 40 and 56 MeV neutron beams, reflects different reaction channels involved in the detection process of high energy neutrons. Up to seven different reaction channels were identified in the pulse shape discrimination spectrum measured by a digital charge comparison method. The analysis of the energy spectra of the secondary particles allowed the cross sections for different reaction channels to be estimated as well. This is shown for the important 12C(n, d) reaction and the non-negligible contribution of the 12C(n, t) reaction to the total efficiency of the NE 213 liquid scintillator for neutrons.

Study of n-γ discrimination by digital charge comparison method for a large volume liquid scintillator

The study of the n-γ discrimination for a large 4 I volume BC501A liquid scintillator coupled to a 130 mm diameter XP4512B photomultiplier was carried out by digital charge comparison method. A very good n-γ discrimination down to 100 keV of recoil electron energy was achieved. The measured relative intensity of the charge integrated at the slow component of the scintillation pulse and the photoelectron yield of the tested counter allow the factor of merit of the n-γ discrimination spectra to be calculated and to be compared with those measured experimentally. This shows that the main limitation of the n-γ discrimination is associated with the statistical fluctuation of the photoelectron number at the slow component. A serious effect of the distortion in the cable used to send the photomultiplier pulse to the electronics for the n-γ discrimination was studied. This suggests that the length of RG58 cable should be limited to about 40 m to preserve a high quality n-γ discrimination.