Abstract
The object of this work was to study the response of the detectors based on the oxide scintillators under irradiation by a flux of fast neutrons from 239Pu-Be source by counting photomultiplier tube pulses. In the process of the research the counting efficiency of the detectors was measured in units of (pulse×s-1×cm-2)/(neutron×s-1×cm-2) for single-crystal and multilayer composite detectors ZWO (ZnWO4), CWO (CdWO4), BGO (Bi4Ge3O12, composite). The measured response for ZWO detector was ~ 64 pulse/neutron, for CWO ~ 36 pulse/neutron, for BGO ~ 0.44 pulse/neutron. The detectors response was registered by a fast preamplifier with the operation speed of up to 500 MHz, based on high-speed operational amplifiers with voltage feedback. The statistical error of measurement for the neutron registration efficiency by the broadband channel made 7% for the detectors with the effective thickness of ~ 40-50 mm, which is due to the spherical geometry of the experiment. The formation of the detector response is affected by the following parameters of neutron reactions: cross section of inelastic and resonant scattering of scintillator nuclei, density of composite nuclei levels, resonance region width, lifetimes of long-lived states and their number. The measured values of the counting efficiency of fast neutrons registration are accounted for the fact that the inelastic scattering reaction for some nuclei is the starting point that triggers the cascade process of the nuclear states discharge. The registration of the cascade of the discharge gamma-quanta, ranging from nanoseconds to a few microseconds, causes an increase in the detector counting efficiency and, as a consequence, an increase in the detector sensitivity to neutron detection. The observed increase in the counting efficiency of secondary gamma quanta is realized when the neutrons are slowed down in the detectors having sufficiently noticeable thickness and appropriate isotopic composition.
Highlights
The object of this work was to study the response of the detectors based on the oxide scintillators under irradiation by a flux of fast neutrons from 239Pu-Be source by counting photomultiplier tube pulses
If the lifetimes of nuclear states are in the range from nanoseconds to tens of microseconds, the detector response registration causes an increase in the detector counting efficiency and, as a result, an increase in its sensitivity to gamma-neutron flux
This paper presents the measurement data and the analysis of contributions of the conversion mechanisms during the fast neutrons slowing down to the genetically bound cascades of gamma-quanta from inelastic and resonant inelastic scattering of fast neutrons on the nuclei of single-crystal and multilayer oxide ZWO, BGO, CWO detectors
Summary
The object of this work was to study the response of the detectors based on the oxide scintillators under irradiation by a flux of fast neutrons from 239Pu-Be source by counting photomultiplier tube pulses. The measured values of the counting efficiency of fast neutrons registration are accounted for the fact that the inelastic scattering reaction for some nuclei is the starting point that triggers the cascade process of the nuclear states discharge. In [1, 2] it was shown that the mechanism of inelastic scattering (n, n'γ) can be used for registration of the fast neutrons by detector, in which heavy oxide scintillators are utilized as the working material [3,4,5] Fast neutrons in this detector are registered by counting pulses induced by the secondary gamma quanta. If the lifetimes of nuclear states are in the range from nanoseconds to tens of microseconds, the detector response registration causes an increase in the detector counting efficiency and, as a result, an increase in its sensitivity to gamma-neutron flux
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
