Search

Abstract: The cosmic-ray muon count rate and energy loss spectra in plastic scintillator detectors are recorded in the Institute of Physics, Belgrade. Measurements are performed at two different levels: at the surface level (78m a.s.l.) and in the Belgrade underground laboratory at the depth of 25m.w.e. From experimental data and with the use of GEANT4 computer simulation the flux and vertical intensities have been determined. At ground level the muon flux is determined to be and vertical intensity while the same quantities underground are and . Their relation to the results of similar measurements worldwide is discussed. [Copyright &y& Elsevier]

Presented study describes the optimization method of an HPGe detector through implementation of Geant4 toolkit. The optimized model was verified through comparison with experimentally obtained data using a set of point-like radioactive calibration sources. Acquired results displayed good agreement with the experimental data that falls under an average relative deviation of the order of ~ 2% within the energy range of 53–1836 keV. Additionally, in order to test the validity of the code it was also applied to a different detection equipment where an average relative deviation of the order of ~ 1.8% was achieved within the energy range of 121–1112 keV. [ABSTRACT FROM AUTHOR]

The background spectrum of a germanium detector, shielded from the radiations arriving from the lower and open for the radiations arriving from the upper hemisphere, is studied by means of absorption measurements, both in a ground level and in an underground laboratory. The low-energy continuous portion of this background spectrum that peaks at around 100keV, which is its most intense component, is found to be of very similar shape at the two locations. It is established that it is mostly due to the radiations of the real continuous spectrum, which is quite similar to the instrumental one. The intensity of this radiation is in our cases estimated to about 8000 photons/(m2s·2π·srad) in the ground level laboratory, and to about 5000 photons/(m2s·2π·srad) in the underground laboratory, at the depth of 25m.w.e. Simulations by GEANT4 and CORSIKA demonstrate that this radiation is predominantly of terrestrial origin, due to environmental gamma radiations scattered off the materials that surround the detector (the “skyshine radiation”), and to a far less extent to cosmic rays of degraded energy. [ABSTRACT FROM AUTHOR]

Abstract A new method for atmospheric correction of cosmic ray data is designed. It's fully empirical, based on the principal component analysis. The method requires knowledge of the pressure and the temperature profile of the atmosphere. It's applicable to all muon detectors. The method is tested on muon data from two detectors in Belgrade cosmic ray station, one located on the ground level and the other at the depth of 25 mwe. Correction reduces variance by 64.5% in ground level detector data and 38.1% in underground data. At the same time, the amplitude of the annual variation is reduced by 86.0% at ground level and 54.9% underground. With the same data sets the presented method performs better than the integral correction method. [ABSTRACT FROM AUTHOR]

Abstract Applicability of our present setup for solar modulation studies in a shallow underground laboratory is tested on four prominent examples of Forbush decrease during solar cycle 24. Forbush decreases are of interest in space weather application and study of energy-dependent solar modulation, and they have been studied extensively. The characteristics of these events, as recorded by various neutron monitors and our detectors, were compared, and rigidity spectrum was found. Linear regression was performed to find power indices that correspond to each event. As expected, a steeper spectrum during more intense extreme solar events with strong X-flares shows a greater modulation of galactic cosmic rays. Presented comparative analysis illustrates the applicability of our setup for studies of solar modulation in the energy region exceeding the sensitivity of neutron monitors. [ABSTRACT FROM AUTHOR]

The possibility of utilizing a shallow underground laboratory for the study of energy dependent solar modulation process is investigated. The laboratory is equipped with muon detectors at ground level and underground (25mwe), and with an underground asymmetric muon telescope to have a single site detection system sensitive to different median energies of primary cosmic-ray particles. The detector response functions to galactic cosmic rays are determined from Monte Carlo simulation of muon generation and propagation through the atmosphere and soil, based on CORSIKA and GEANT4 simulation packages. The present setup is suitable for studies of energy dependence of Forbush decreases and other transient or quasi-periodic cosmic-ray variations. [ABSTRACT FROM AUTHOR]

Abstract: Long-time background spectra of a well-shielded HPGe detector are recorded in order to estimate the contribution of inelastic neutron scattering on Ge nuclei in the low-energy part of the spectra, mainly influenced by elastic neutron collisions. It is shown that using intensities of several asymmetric peaks characteristic of Ge(n,n′) reactions and some properties of detectors (ability for total absorption or total transmission of gamma photons emitted during de-excitation of Ge nuclei) the contribution of Ge(n,n′) reactions to the low-energy part of spectra can be evaluated. The obtained result is in good agreement with results of simulations available in the literature. [Copyright &y& Elsevier]

The proposed influence of cosmic rays on cloud formation is tested for the effect of sudden intensity changes of CR (Forbush decreases) on cloudiness. An attempt is made to widen the investigated period covered by satellite observation of cloudiness. As an indicator of cloud cover, the diurnal temperature range (DTR - a quantity anticorrelated with cloudiness) is used. The superposed epoch analysis on a set of isolated Forbush decreases is conducted and the results for a region of Europe are presented. The effect of Forbush decrease on DTR is statistically significant only if the analysis is restricted to high amplitude FDs (above the threshold value of 7% with the respect to undisturbed CR intensity). The magnitude of the effect on DTR is estimated to be (0.38 ± 0.06) °C. [ABSTRACT FROM AUTHOR]

Abstract: The low-level gamma-ray spectroscopy as well as the investigation of rare nuclear processes require not only low, but also constant levels of relevant background radiations. In underground laboratories dedicated to this type of measurements, one of the main and hard to control sources of unwanted radiation is the radioactive gas radon. It is well-known that radon concentration varies daily and seasonally, primarily due to the variation of atmospheric parameters. This introduces unwanted and hard to evaluate systematic uncertainties in long-term low-level measurements. In this paper, the system for radon reduction in the underground Low-Background Laboratory for Nuclear Physics at the Institute of Physics in Belgrade is presented in some detail. The laboratory exists for ten years and different measurements of radon concentration were carried out during this period. The indoor radon measurements are performed using nuclear track detectors (type CR-39 and LR-115) for long-term measurements and the commercially available radon monitor for short-term measurements. In this work we present the results of these measurements for the period 2003–2008. [Copyright &y& Elsevier]

Cosmic muon flux is recorded by two plastic scintillator detectors: one located at ground level and the other located in the Belgrade underground laboratory (25 m w.e.). Power spectral analysis of the raw detector data for the period from January 1st 2002 to December 31st 2002 is performed. Similar periodicities are found in both data sets (ground and underground), but with different amplitudes. Main periodicity in the underground detector data has a 26.5 days period, while the highest amplitude signal in the ground detector data has a 243 ± 45 days period. Other signals present in the time series correspond to higher harmonics of the solar rotation period. There is also a wave with a 34.4 days period, whose significance is confirmed by different methods of spectral analysis. The same periodicity is recently found in some processes on the Sun. [ABSTRACT FROM AUTHOR]

Abstract: Experimental results and theoretical studies show that protons from the hydrogen plasma focus are emitted predominantly in the axial direction. In this work the results of the flux and energy distribution measurements of the axial protons using CR-39 detector are presented. The main purpose of the experiment is to test the suitability of a plasma focus device as a source for nuclear reactions, especially and . [Copyright &y& Elsevier]

An experiment on electrical discharges in air under normal atmospheric conditions has been performed. The ratio between output and input energy is greater than 1, which confirms the results already reported by Graneau et al. [Copyright &y& Elsevier]

Angular distribution of emitted protons was measured. The protons were detected with NTD LR-115 placed at the specially constructed semi-spherical holder, which contains 17 different pinhole cameras. The mechanism of proton acceleration and emission are studied theoretically and experimental results are compared with theoretical predictions. [Copyright &y& Elsevier]