Experimental comparison of the measurement results of two different silicon photomultipliers and organic scintillator to detect fast neutrons

Using natural helium (helium-4), the Arktis 180-bar pressurized gas scintillator is capable of detecting and distinguishing fast neutrons and gammas. The detector has a unique design of three optically separated segments in which 12 silicon-photomultiplier (SiPM) pairs are positioned equilaterally across the detector to allow for them to be fully immersed in the helium-4 gas volume; consequently, no additional optical interfaces are necessary. The SiPM signals were amplified, shaped, and readout by an analog board; a 250 MHz, 14-bit digitizer was used to examine the output pulses from each SiPMpair channel. The SiPM over-voltage had to be adjusted in order to reduce pulse clipping and negative overshoot, which was observed for events with high scintillation production. Pulse shaped discrimination (PSD) was conducted by evaluating three different parameters: time over threshold (TOT), pulse amplitude, and pulse integral. In order to differentiate high and low energy events, a 30ns gate window was implemented to group pulses from two SiPM channels or more for the calculation of TOT. It was demonstrated that pulses from a single SiPM channel within the 30ns window corresponded to low-energy gamma events while groups of pulses from two-channels or more were most likely neutron events. Due to gamma pulses having lower pulse amplitude, the percentage of measured gamma also depends on the threshold value in TOT calculations. Similarly, the threshold values were varied for the optimal PSD methods of using pulse amplitude and pulse area parameters. Helium-4 detectors equipped with SiPMs are excellent for in-the-field radiation measurement of nuclear spent fuel casks. With optimized PSD methods, the goal of developing a fuel cask content monitoring and inspection system based on these helium-4 detectors will be achieved.

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A study of possibility to design a fast neutron spectrometer based on the organic scintillator with surrounding materials

Nuclear Technology and Radiation Protection ◽

10.2298/ntrp1401001a ◽

2014 ◽

Vol 29 (1) ◽

pp. 1-9

Author(s):

Senada Avdic ◽

Predrag Marinkovic ◽

Alma Osmanovic ◽

Izet Gazdic ◽

Sejla Hadzic ◽

...

Keyword(s):

Fast Neutron ◽

Neutron Energy ◽

Pulse Height ◽

Simulated Data ◽

Nuclear Safeguards ◽

Numerical Code ◽

Fast Neutrons ◽

Neutron Spectrometer ◽

Neutron Sources ◽

Organic Scintillator

This paper deals with the design of a novel spectrometer of fast neutrons in nuclear safeguards applications based on the liquid organic scintillator EJ-309 with materials of different thickness surrounding the detector. The investigation was performed on the simulated data obtained by the MCNPX-PoliMi numerical code based on the Monte Carlo method. Among the various materials (polyethylene, iron, aluminum, and graphite) investigated as layers around the scintillator, polyethylene and iron have shown the most promising characteristics for evaluation of fast neutron energy spectra. The simulated pulse height distributions were summed up for each energy bin in the neutron energy range between 1 MeV and 15 MeV in order to obtain better counting statistics. The unfolded results for monoenergetic neutron sources obtained by a first order of Tikhonov regularization and non-linear neural network show very good agreement with the reference data while the evaluated spectra of neutron sources continuous in energy follow the trend of the reference spectra. The possible advantages of a novel spectrometer include a less number of input data for processing and a less sensitivity to the noise compared to the scintillation detector without surrounding materials.

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Measurement and simulation of the new liquid organic scintillator response to fast neutrons

EPJ Web of Conferences ◽

10.1051/epjconf/202125311006 ◽

2021 ◽

Vol 253 ◽

pp. 11006

Author(s):

Jaroslav Jánský ◽

Jiřĺ Janda ◽

Zdeněk Matěj ◽

Filip Mravec ◽

Michal Košťál ◽

...

Keyword(s):

Functional Dependence ◽

Neutron Radiation ◽

Dissipated Energy ◽

Fast Neutrons ◽

Function Evaluation ◽

Neutron Spectrometry ◽

Carbon Ion ◽

Organic Scintillator ◽

Organic Scintillators ◽

Liquid Organic Scintillator

Liquid organic scintillators are important devices for measurements of neutron radiation. This work aims to develop and optimize the composition of liquid organic scintillators so it can be used for fast neutron spectrometry. As the neutron radiation is usually accompanied with γ ray radiation, it is important to have quality γ/n discrimination. The new cocktail for house made liquid organic scintillator is prepared and studied with intention of being able to separate gamma and neutron for neutron energies above 0.5 MeV while keeping lower constraints on practical use (e.g., sealing because of oxygen) than commercial liquid scintillators. In preceding work the composition of liquid scintillators was optimized. Two twocomponent scintillators were selected for further studies. Solvent DIPN (Di-iso-propyl-naphthalene Mixed Isomers) is selected for both. First is mixed with luminophore PYR (1-Phenyl-3-(2,4,6-trimethyl-phenyl)-2-pyrazoline) of concentration 5 g/l. Second is mixed with luminophore THIO (2,5-Bis(5-tert-butyl-benzoxazol-2-yl)thiophene) of concentration 5 g/l. In this work the response of scintillator to monoenergetic beam of neutrons was measured for multiple neutron energies at PTB in Braunschweig. The two parameter spectrometric system NGA-01 is used to analyze the energy and discrimination characteristics. 137 Cs and 60 Co are used as radiation sources for calibration with pure γ rays. Then the response of scintillator for same neutron energies was simulated using GEANT4. The dissipated energy in the scintillator in response to monoenergetic neutrons is obtained. Both, measured and simulated responses are compared. Functional dependence for yield of recoiled products is estimated. It is seen that main recoil product hydrogen proton is well observed in both. From the edge of proton response one can assume the yield for given neutron energy. The recoiled carbon ion (from elastic collision) is on the other side diﬃcult to observe in measured results but clearly seen in dissipated energy plots. It suggests that yield of carbon ion is very small relatively to proton yield. These results will serve as basis for response function evaluation of scintillator which is necessary for evaluation of unknown neutron spectra from measurements with scintillator.

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An Empirical Study on Chinese And American College Students’ Moral Value Recognition

ETHICS IN PROGRESS ◽

10.14746/eip.2018.1.6 ◽

2018 ◽

Vol 9 (1) ◽

pp. 118-127

Author(s):

Zhu Hailong

Keyword(s):

College Students ◽

Undergraduate Students ◽

Filial Piety ◽

Chinese Culture ◽

Experimental Comparison ◽

Moral Value ◽

Chinese College Students ◽

American Students ◽

Measurement Results ◽

Helping Others

This study used a self-designed questionnaire to empirically evaluate Chinese and American undergraduate students’ recognition of moral values in six dimensions: honesty, civility & self-discipline, benevolence, unity & helping others, esteem, and filial piety. In total, 743 valid samples from 8 Chinese universities and 157 valid samples from 4 American universities were collected for an experimental comparison. Measurement results showed that the differences between Chinese and American college students were not significant in the dimensions of honesty, benevolence, esteem, and filial piety. These values, which originated in traditional Chinese culture, had the same priorities in both groups, confirming a certain degree of universality. However, significant intergroup differences existed in the civility and self-discipline dimension and the unity and helping others dimension. These results highlight the importance of enhancing Chinese college students’ moral consciousness, especially with esteem, and of enhancing American students’ consciousness of unity and helping others.

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