Abstract
In the present work we found the maximum discovery distance for 239Pu-Be source using the detectors based on ZWO (ZnWO4) and BGO (Bi4Ge3O12) oxide scintillators. Detection distance was defined by using the radiation monitoring system ”PORTAL”. This research gives us data for estimation of the contribution of low-energy cascade gamma quanta CGQ. The CGQ emitted by excited scintillator nuclei defined the effective discovery distance of the fast neutrons source. The maximum detection distance was obtained with PMT in a single-photon counting mode. The maximum discovery distance for a BGO scintillator of size Ø40×40 mm – 38 cm, ZWO scintillator of size Ø52×40 mm – 54 cm, with reliability about 0.001. The results of the experiment on the ZWO scintillator can be explained by the registration of additional gamma quanta from the inelastic scattering reaction and the CGQ arising from resonant neutron capture region. This two mechanisms further lead to increase the sensitivity of the detector and increase the detection distance of the monitoring system. The key features of the monitoring system are: ZWO oxide scintillator, wide band measuring path, utilize PMT in single photon mode. The obtained detection distance was about 1.4 times higher in comparison with the spectrometric recording mode and 1.9 times higher in values of efficiency. Our results demonstrate the advantages of the ZWO scintillator compared to the BGO and demonstrate the possibility of using the resonant capture mechanism by ZWO detector nuclei to increase the fast neutrons sensitivity. The resonance capture mechanism increase sensitivity and maximum detection distance of the monitoring system. The low-energy gamma-quanta, which discharge of compound nuclei, are substantially suppressed in comparison with the classic spectrometric recording mode.
Highlights
Earlier [3,4,5], the signals of oxide scintillation detectors in order to suppress CGQ were amplified in the spectrometric mode, while the time of formation of the signal from the PMT in this mode was in the range 1 – 10 microseconds
In the present work we found the maximum discovery distance for 239Pu-Be source using the detectors based on ZWO (ZnWO4) and BGO (Bi4Ge3O12) oxide scintillators
Our results demonstrate the advantages of the ZWO scintillator compared to the BGO and demonstrate the possibility of using the resonant capture mechanism by ZWO detector nuclei to increase the fast neutrons sensitivity
Summary
Earlier [3,4,5], the signals of oxide scintillation detectors in order to suppress CGQ were amplified in the spectrometric mode, while the time of formation of the signal from the PMT in this mode was in the range 1 – 10 microseconds. The aim of this work is a comparative assessment of the maximum neutron detection distance of a 239Pu-Be source by a monitoring system using ZWO, BGO detectors in two significantly different modes - spectrometric and single photon counting mode. It was the use of the single photon counting mode in the monitoring system with the highly sensitive wideband preamplifier that made it possible to estimate the contribution of low energy CGQ generated in the compound nuclei of the oxide scintillator to the maximum detection distance.
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