Comparative study of the pulse shape discrimination (PSD) performance of fast neutron detectors

Abstract

Certain scintillating materials are sensitive to both gamma and neutron radiation and can give information about the type of interacting radiation due to differences in the light output response. By collecting the light pulses and converting them to electrical signals the nature of the radiation can be determined by measuring the amount of electrical charge in the pulse tail -for neutrons, the pulses are longer, with more charge in the tail than for the shorter gamma pulses. This determination called Pulse Shape Discrimination (PSD) can nowadays be performed in real-time onboard digitisers during data collection. In this work several detectors (EJ301, EJ309 liquids; EJ299-33 plastic and p-terphenyl scintillators) of various shapes and sizes were connected to several digital Data Acquisition (DAQ) systems as well as the established digital / analogue hybrid Mesytec MPD8 / MADC-32 set up in a comparative study. The aim of the campaign was to produce a Figures of Merit (FOM) for the PSD performance of the various detector / DAQ combinations to give relative performance estimates of the CAEN V1751 10-bit 1 GSample/s digitiser in comparison with other DAQ solutions within a near-standardised experimental environment. It islikely that the DAQ set ups were not equivalent as significant differences in the matching of the detector outputs to the dynamic range of the digitisers were observed -however, with the configurations used in this campaign the CAEN V1751 digitiser showed superior FOM values to the Struck SiS3320, Bridgeport usbBase and Mesytec MPD-8 DAQ systems tested. Furthermore, there seemed little difference between the FOM from the faster but lower voltage resolution (1 GSample/s with 10 bits) CAEN V1751 compared to the slower but higher resolution (250 MSample/s with 12 bits) CAEN N6720 digitiser for this application.

Assessing the suitability of three proxy sources for the development of detectors of special nuclear materials

“…Good PSD performance is generally defined as a 3σ separation of the neutron and γ peaks [1,44], which equates to a FoM of 1.27. The 15 mm cube generally provides poorer PSD performance than the smaller scintillator, which fits the commonly observed trend in these plastic scintillators of worsening PSD performance as the volume of the scintillator increases [45,46]. It can be seen from table 3 that for the EJ-299 material the PSD performance at a threshold of 500 keV ee fails to meet the 3σ criterion.…”

“…With the successful performance of this system in mind, the next stages of development must surely be in the direction of deployable equipment. Current radiation portal monitors use substantially larger volumes of scintillator than have been investigated in this work, and it has been shown previously that scintillator size has a direct effect on PSD performance [45,46]. The degradation observed in PSD as detector volume increases is a combination of parameters: the optical attenuation as the photon transverses the scintillator; the increased variation in transit time due to multiple reflections within the material; and the relatively similar durations of neutron and γ ray time constants.…”

Studies on the Luminescence and Scintillation Properties of 9,10-Diphenylanthracene Crystals Grown by Two Methods

“…According to these definitions, the FOM of DPA-Melt, DPA-Solution, and stilbene are 2.432, 1.356, and 3.26, respectively. Although the definitions vary, many international research groups have tested similar curves. − To the best of our knowledge, all of these assessments are essentially the same. A recent study by Iwanowska et al reported on the test results for the capabilities of pulse-shape discrimination of stilbene crystal and p -terphenyl-based crystal, and the p -terphenyl-based one is determined as a few better than stilbene.…”

Pulse-shape discrimination scintillators for homeland security applications

“…The full details of the study can be found in Ref. 6, but the main findings that are relevant to this paper are summarized here.…”

“…9,10 These experiments showed up to a four-fold variation in FOM for any given detector depending on the data acquisition system used. 6 The results from this workshop have been used to inform the choice of data acquisition digitizer used on the designs developed for the applications described later.…”