This paper reports on the development of a gamma-ray spectroscopic system for the (i) recording and (ii) processing of spectra. The utilized data read-out unit consists of a PCI digital oscilloscope, personal computer and LabVIEW™ programming environment. A pulse-height spectra of various sources were recorded with two NaI(Tl) detectors and analyzed, demonstrating the proper usage of the detectors. A multichannel analyzer implements the Gaussian photopeak fitting. The presented method provides results which are in compliance to the ones taken from commercial spectroscopy systems. Each individual hardware or software unit can be further utilized in different spectrometric user-systems. An application of the developed system for research and teaching purposes regarding the design of digital spectrometric systems has been successfully tested at the laboratories of the Department of Experimental Physics.
The absorption cross sections of low energy neutrons obey 1/v law for most materials. Therefore, the detection efficiency of a particular detector increase with decreasing neutron energy. Consequently, most of neutron measuring instruments consist of the detector of thermal neutrons which is located inside of the polyethylene moderator. Development of such instruments requires testing and response calibrations in the field of thermal neutrons. Availability of thermal neutron beams on nuclear reactors is limited and access to them is rather complicated, so it is more convenient to moderate neutrons from the radionuclide neutron sources. Since radiunuclide neutron sources are producing fast neutrons it is necessary to use an appropriate moderator material like heavy water or graphite to thermalize neutrons from the source and to avoid thermal neutron capture in the same time.Thermal neutron fluence rate is commonly measured by means of gold activation detectors. The quality of a moderated thermal neutron source spectra is then characterized by so called 'cadmium ratio' parameter. This parameter is based on properties of Cd-113 isotope (12.2% natural abundance of Cd) with very high neutron cross-section as depicted in Fig. 1. Gold foil is activated in the thermal neutron field both bare and encapsulated in a Cd housing and the correspondig activity ratio characterize the thermal neutron field. Au-197 has strong resonance at 4.9 eV which allows measurable activation of the gold inside the cadmium capsule.
Basic moderated thermal neutron field characteristics are: Cadmium ratio: = Cadmium coefficient:where A tot is activity of openly irradiated Au foil and A epi is activity of a Au foil irradiated in the Cd capsule. The effective energy cut-off E Cd of used cadmium covers is 0.5 eV.
In this work, we compare the pulse-shape discrimination (PSD) properties of newly developed liquid scintillators 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 (A/D) converters with a resolution of 12 bits and sampling frequency of 500 MHz. We used active divider to improve linearity of the photomultiplier (PMT). Measured data from scintillators have been processed using the integration method and compared. The results are presented.
This paper has been formally retracted because it has been accidentally published twice in the same volume. Request approved by the proceedings Editor and the Publisher on June 02, 2023.
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