In this work, we compare the pulse-shape discrimination (PSD) properties of newly developed liquid scintillator LSB-200, EJ-299-33A, BC-501A, stilbene, p-terphenyl, and Hidex Aqualight in neutron field generated by the LVR-15 reactor with silicon filter utilization. Pulses from the scintillators are processed by the Neutron-Gamma spectrometer. This spectrometric system with fast digitizer card contains two analog–digital converters with a resolution of 12 bits and sampling frequency 500 × 106 Hz. For photomultiplier linearity improvement, the active divider has been used. Measured data from scintillators have been processed using the integration method and compared. The results are presented.

This article focuses on description of two different neutron fields from linear and cylindrical Inertial Electrostatic Confinement (IEC) neutron generators. Both of these generators are well defined and commonly used. They use a deuterium-tritium reaction that produces neutrons with energies in the range 13 – 16 MeV, depending on the direction and the energy of the incoming deuterium nucleus. Two-parametric spectrometric system for neutron/gamma mixed fields NGA-01 was used to characterize neutron spectra in the proximity of generators. The cylindrical 45x45 mm stilbene scintillator was connected to this device using an active voltage divider. This way, we were able to measure neutron energies in the range 1 - 15 MeV while filtering out gamma radiation, even when counts per second is high. For the neutron spectrum calculation recoil spectra using deconvolution through maximum likelihood estimation was used. Measured neutron spectra have been compared with simulations realized via MCNP6. According to the theoretical prediction, these two types of generators produce different neutron fields. In case of the linear generator the target is very close to point located tritium bombarded by deuterons. Thus the neutron spectrum varies depending on the angle between the detector axis and the axis of the generator. Both experimental results and simulation show a shift of the neutron energy peak in pulse height histogram. For IEC type generators the neutron spectrum is more complicated. The shape and the position of the neutron energy peak depend heavily on the position of the detector. The most prominent effect is in the position in the plane perpendicular to the generator axis. In this case, the peak splits into two peaks that can be measured and distinguished. These results were verified by the diamond detector which was also used for characterization of the IEC type generator.

Proportional counters filled with hydrogen are suitable for fast neutron detection and spectrometry. As their sensitivity is not limited only to this type of ionizing radiation as desired, an approach suitable for event discrimination was investigated. Several counters of the given construction were subjected to various radiation fields and the effort was directed to the examination of pulse-shape discrimination method intended to distinguish neutrons from gamma rays and parasitic events (microdischarges) if these also occurred. Rising edge duration of the output pulses and their amplitudes were mapped into diagrams enabling visual discrimination while the criteria for further computational processes are to be determined. Pulse waveforms from charge-sensitive preamplifier with the proportional counters connected were recorded using an FPGA-based custom-build acquisition unit and then post-processed. Moreover, the possibility of operation verification and energy calibration based on the introduction of helium-3 admixture into the gas filling was studied, as well as the energy resolution abilities. Also, the theoretical basis for particle discrimination is presented in the form of description of events and principles involved.

In this work, we studied the light-output properties, efficiency function, as well as the pulse-shape discrimination (PSD) capability of p-Terphenyl scintillator. The selected solid cylindrical scintillation detector has a thickness of 45 mm and a diameter of 45 mm. Recently presented studies of light-output functions have only been measured for low-neutron energies. Our motivation has been to determine the light output function for p-Terphenyl scintillator more accurately over a wider neutron energy range. The measurements have been carried out with mono-energetic neutron beams in the wide energy range from 1.1 to 19 MeV. The neutron–gamma spectrometric system which we developed has been used for the measurement. The input analog signal from the detector was digitized with a fast 12-bits analog to digital converter with a sampling frequency of 1 GHz. Measured data from the detector are processed into the gamma and neutron spectra. The accurate light output function for the p-Therphenyl scintillator has been calculated. The pulse-shape discrimination capability, as well as the detection efficiency, of a p-Terphenyl scintillator are lower in comparison with a NE-213 equivalent detector.

In this paper, we study the effect of decreasing aperture diameter on signal transmission from the scintillator to the PMT. The apertures have been inserted directly between the scintillator and the photomultiplier. Three different aperture diameters have been used over a wide energy range. A newly developed fast digital spectrometer has been utilized for experimental measurement in the radial channel of the VR-1 research reactor. The detector signals with and without inserted apertures have been measured and evaluated. The aim of our research was to determine the effect of the apertures on the spectral quality, energy range and the evaluated physical quantities.