NE213 scintillation detectors are excellent tools for use in a mixed gamma and neutron field due to its established pulse shape discrimination ability. With proper pulse shape discrimination, gamma or neutron responses may be obtained in a mixed radiation field. The neutron response needs to be deconvolved from the detector response function to obtain an energy spectrum. To perform unfolding of neutron spectra, mono-energetic responses are needed and the responses may be obtained via experiment or simulation of the NE213 detector. In this work, response functions were tested with the unfolding of a Cf-252 spectrum. Particularly, experiments were performed at the Los Alamos National Laboratory where Cf-252 spectra were obtained. During the experiment, different pre-amplifier set-ups were tested. Namely, the pulse shape discrimination ability of the system using 50 ohm, 500 ohm, and 1000 ohm termination resistors were compared. However, linear system responses were not observed with the different settings. Thus, the Amoeba Simplex fitting routine was used to augment the charge integration pulse shape discrimination technique to separate the neutron and the gamma signals. Furthermore, a new figure of merit scheme was explored to quantify the pulse shape discrimination ability of the said non-linear system. Alongside the Cf-252 spectra experimental measurements, the program Scinful was used to generate mono-energetic neutron responses needed for unfolding. Consequently, both the Cf-252 neutron spectra and the Scinful responses were used with the program FERD-PC for unfolding. Among the different termination resistors compared with the new figure of merit scheme, the 50 ohm resistor setting was observed to be superior. The resultant unfolded spectrum using the 50 ohm termination resistor shows excellent agreement between 2-10 MeV. However, even with the Amoeba Simplex method, results below 2 MeV are not accurate due to the poor pulse shape discrimination limit of the sys.

A high-energy liquid-organic scintillation spectrometer system is described. This spectrometer was developed to measure neutron spectra in extracted beams from zero-power fast reactors. The highly efficient NE-213 scintillation solution was used as the neutron detection medium. Identification and removal of gamma-ray-induced events was accomplished using electronic pulse shape discrimination. Instrumentation used to process the discrete pulses stemming from neutron and gamma-ray interactions, within the scintillation solution, is described in detail. Evaluation of the system's performance is discussed for a gamma-ray discrimination ratio of nominally 1000:1, a total countrate of 3000 cps, and a dynamic range corresponding to neutron energies from 1 to 10 MeV. Operation above 10 MeV is certainly possible. However, since the neutron flux above 10 MeV was negligible in the radiation fields of interest in this work, the operating characteristics of the spectrometer were not evaluated above 10 MeV. Neutron spectra are reported for extracted beam measurements made on ZPPR assembly 4, phase 2.