(
) and (
) reactions induced by the alpha decays of uranium, thorium, and their daughter nuclides generate the intrinsic neutron and gamma backgrounds in modern ultralow background neutrino and dark ...matter detectors. In order to minimize the background, it is essential to select materials on the basis of a detailed analysis of relative concentrations of radionuclides and calculations of neutron and gamma-radiation yields. The NeuCBOT (Neutron Calculator Based On TALYS) program makes it possible to perform such calculations. The present article gives a review of a new version of the NeuCBOT program and a comparison of the results of calculations with different software tools.
Abstract According to the focal cortical theory of absence epilepsy, spike-and-wave discharges (SWDs) have a cortical focal origin in the perioral region of the somatosensory cortex in rats. In the ...present study the role of peripheral afferents of the perioral (snout) region in the occurrence of spontaneous SWDs was investigated in the WAG/Rij (Wistar Albino Glaxo from Rijswijk) rat model of absence epilepsy in order to examine whether an input from peripheral sources is imperative for the occurrence of SWDs. Twelve male WAG/Rij rats were chronically equipped with cortical EEG electrodes. Peripheral afferents of the perioral region of the snout nervus trigeminus were pharmacologically blocked with a local injection of 2% Novocain, a blockade of nervus facialis and saline injections were used as controls. ECoGs were recorded before and after bilateral injection of the drug. Blockade of the n. trigeminus decreased the incidence and duration of SWD, while similar injections with Novocain near the n. facialis had no effect. Injections with saline were also not effective. Our data demonstrate that intact peripheral afferent input may be primarily involved in the initiation of SWDs. It suggests that the cortico-thalamo-cortical circuits need the peripheral stimulations from the snout and vibrissae for an initiation of the spontaneous SWDs.
Scintillation detectors with organic scintillators are widely used for fast neutrons detection in high gamma ray background. The peculiarity of this type of detector is that the pulse shape depends ...on the type of the detected particle. Traditionally, the Pulse Shape Discrimination (PSD) histogram is used to determine the number of detected neutrons. The PSD parameter is calculated from the shape of the detector pulse and assigned to each pulse. A typical PSD histogram contains two peaks corresponding to neutrons and gamma rays that overlap in the region between the peaks. With this approach, it is impossible to identify each individual signal in the area between the peaks. Therefore, it is not possible to calculate the overall signal identification coefficient. We have proposed a new method for the identification of neutrons and gamma quanta, which includes a combination of three signal separation algorithms: the traditional histogram PSD, the dependence of the area of signals on their amplitude, Tau histogram (tau means the fall constant of the detector pulses). This combination of three algorithms makes it possible to calculate the value of the signal identification coefficient. To test a new method for identifying neutrons and gamma quanta, we used a Pu-Be neutron source, a scintillation detector with a p-terphenyl crystal and a CAEN DT5730 Digitizer (14 bit, 500 MHz). When a scintillation detector registered neutron from a Pu-Be source, the signal identification coefficient was 91.6%. A new method for identifying signals from a scintillation detector is used to register neutrons at the light ion accelerator.
Thin luminescent films of the organometallic complex of lithium 8-hydroxyquinolate Liq on glass substrates were fabricated by capillary deposition and lithography. The spectral-luminescent properties ...of the obtained film structures were investigated. The film surface was analyzed. The light yield and the kinetics of scintillation emission of the obtained film structures are estimated.
Abstract The role of cholinergic nucleus basalis (of Meynert) and the reticular thalamic nucleus in mechanisms of the generation spontaneous spike-and-wave discharges (SWDs) was investigated in the ...WAG/Rij rat model of absence epilepsy. Selective lesions were affected by local unilateral intraparenchymal infusions of immunotoxin 192 IgG-saporin and cholinotoxin AF64A to the nucleus basalis and the rostral pole of reticular thalamic nucleus. Injections of 192 IgG-saporin into the nucleus basalis increased the number of spontaneous SWDs, while injections in the reticular thalamic nucleus were not effective. Thereby, a loss of cholinergic activity in the nucleus basalis stimulates the appearance of SWDs. At the same time, AF64A infused into reticular thalamic nucleus, besides the reduction of choline acetyltransferase immunoreactive neurons within contralateral nucleus basalis, produced some unspecified lesion of adjacent neuronal tissue, resulted in decrease of number and duration of SWDs as well as in spectral changes in EEG. Considering that the nucleus basalis is an important source of cortical and thalamic cholinergic afferentation, we conclude that cholinergic excitatory input from this structure is important in the control of SWDs in the WAG/Rij rat model of absence epilepsy.
The conception of operation of the pyroelectric accelerator and X-ray source in pulsed mode is at first proposed and demonstrated experimentally. The pulsed mode became possible due to application of ...the additional controlled source of electrons in the pyroelectric accelerator. In the proof-of-principle experiment, the power of X-ray radiation in pulsed mode increased one in common quasi-continuous mode in more than two orders of magnitude. Perspectives for further increasing of the power and application of pulsed pyroelectric X-ray source in fast X-ray imaging are discussed.
In the coming years, the compact monoenergetic neutron generators (CNG) producing up to 104 n/s may become an alternative to the standard neutron sources based on radioactive isotopes for the ...calibrations of neutrino and dark matter detectors. Such neutron generators have a typical size of about several centimetres, they may be manufactured using low-background materials and may require only low voltage power supply for operation. We discuss the advantages and disadvantages of two main types of the compact neutron generators, namely a pyroelectric neutron source and a high voltage neutron generator. Also the results of the technical analysis of the possibilities to apply such sources for the calibration of low-background experiments are given, the variant of the internal device design is shown and the full-size compact neutron generator prototype are presented.
A laboratory technique was developed for obtaining an ultra-low-background hybrid material based on organic glass — polymethyl methacrylate (PMMA).
157
Gd nuclei are used as an efficient absorber of ...thermal neutrons in the hybrid material. A uniform distribution of gadolinium in the PMMAmatrix is achieved by introducing the gadolinium in the form of a coordination compound — gadolinium acetylacetonate — into the hybrid material. A uniform gadolinium distribution was achieved in a 5 cm thick matrix of hybrid material with gadolinium mass content from 1.0 to 1.5%. It is shown that at 298 K the mechanical characteristics of the hybrid material samples coincide with nominally pure PMMA, but at 77 K the hybrid material is inferior to pure PMMA within admissible requirements.
The aim of the study is to consider the features of the physico–chemical processes in the near-contact region of the semiconductor SiC phase doped with radionuclide by solid-phase diffusion of
C ...atoms, generation of nonequilibrium carriers and the semiconductor phase distinctive characteristic features. The DFT approach in this paper is aimed at obtaining evidence of the vacancy mechanism of diffusion during the formation of the SiC phase in the Si wafer. Radionuclide and silicon atoms counter-diffuse through a growing layer of silicon carbide, forming layers by solid-phase chemical transformation of silicon of
- or
-type conductivity into heterostructures of anisotypic or isotypic type of conductivity relative to the SiC phase, with superstecheometric alloying with conservation of the valence and the type of impurity conductivity, forming, depending on the phase, effects energetically manifested as the effect of ‘‘the inner sun,’’ which is the source of electrons and electron–hole pairs at ionization losses. This is due to interactions with the electrons of the shells of neighboring atoms, leading to the formation of electrons and holes in the region of spatial charge and carrying by built-in electric fields. The purpose of the study is due to an increase in the efficiency of separation of electron–hole pairs.
The solution of the problem how to register fast neutrons in the presence of intense gamma radiation is required when solving such fundamental and applied problems as registration of the neutron and ...gamma background in underground low-background experiments (the low background detectors of the neutrino and dark matter); beam diagnostic at particle accelerators; radiation monitoring at nuclear facilities, nuclear medicine; environmental monitoring. To separate signals from neutrons and gamma quanta, scintillation detectors with organic scintillators are used. The best scintillators are organic crystals of stilbene and p-terphenyl. The efficiency of separating signals from neutrons and gamma quanta can be increased using various methods of digital signal processing of the pulse shapes of the registered signals. A parameter traditionally called the Figure of Merit (FOM) is used to compare these methods. The experimental setup consisted of a Pu-Be neutron source, a scintillation detector with organic crystal p-terphenyl, a Hamamatsu R6094 photomultiplier, a CAEN DT5730 Digitizer (500 MHz, 14bit), which store the shape of each pulse for the following digital processing. A new "method of normalized signals" was developed. Three variants of the new method of normalized signals are described, which give the following FOM values: 1.6, 1.7, and 2.1. The traditional method of signals separation on the same array of experimental data showed the efficiency FOM = 1.6. The new method of signal separation is used to register fast neutrons in the installation dedicated for the development of a compact neutron generator, which is necessary for the calibration of low-background detectors of neutrinos and dark matter particles.
PDF
