I. Aničin

User-friendly Monte-Carlo program for the generation of gamma-ray spectral responses in complex source–detector arrangements

Abstract The Monte Carlo program has been developed which generates the spectral responses of gamma-ray spectrometers (NaI, Ge, etc.) for radiations of arbitrarily complex composition and for easily definable disposition of sources, passive absorbers and/or scatterers and detectors, all of which can be of prismoidal, cylindrical and toroidal shapes as well as of arbitrary chemical composition. Any spectrum may be collected either as a single one or in coincidence with any other spectrum. The program is comfortably run on any PC of modest configuration.

Radon measurements during the building of a low-level laboratory

Abstract Radon measurements were provided during the different stages of building of a low-level laboratory in Belgrade. The depth of the laboratory is 12 m, equivalent to 30 m of water with an area of 45 m 2 . The whole of the laboratory is hermetically lined with 1 mm Al foil and is ventilated with filtered air. Radon concentrations were measured with the CR-39 detector as well as via the gamma-ray spectroscopic measurements. The radon concentrations in the air were achieved to 20 Bqm −3 and reduction of secondary and tertiary cosmic-ray fluxes is five times when ventilation, filtering and sealing was applied.

Erosion rate study at the Allchar deposit (Macedonia) based on radioactive and stable cosmogenic nuclides (26Al, 36Cl, 3He, and 21Ne)

Abstract This paper focuses on constraining the erosion rate in the area of the Allchar Sb‐As‐Tl‐Au deposit (Macedonia). It contains the largest known reserves of lorandite (TlAsS2), which is essential for the LORanditeEXperiment (LOREX), aimed at determining the long‐term solar neutrino flux. Because the erosion history of the Allchar area is crucial for the success of LOREX, we applied terrestrial in situ cosmogenic nuclides including both radioactive (26Al and 36Cl) and stable (3He and 21Ne) nuclides in quartz, dolomite/calcite, sanidine, and diopside. The obtained results suggest that there is accordance in the values obtained by applying 26Al, 36Cl, and 21Ne for around 85% of the entire sample collection, with resulting erosion rates varying from several tens of m/Ma to ∼165 m/Ma. The samples from four locations (L‐8 CD, L1b/R, L1c/R, and L‐4/ADR) give erosion rates between 300 and 400 m/Ma. Although these localities reveal remarkably higher values, which may be explained by burial events that occurred in part of Allchar, the erosion rate estimates mostly in the range between 50 and 100 m/Ma. This range further enables us to estimate the vertical erosion rate values for the two main ore bodies Crven Dol and Centralni Deo. We also estimate that the lower and upper limits of average paleo‐depths for the ore body Centralni Deo from 4.3 Ma to the present are 250–290 and 750–790 m, respectively, whereas the upper limit of paleo‐depth for the ore body Crven Dol over the same geological age is 860 m. The estimated paleo‐depth values allow estimating the relative contributions of 205Pb derived from pp‐neutrino and fast cosmic‐ray muons, respectively, which is an important prerequisite for the LOREX experiment.

Monte Carlo simulations of the response of a plastic scintillator and an HPGe spectrometer in coincidence

A simulation programme based on the Geant4 toolkit has been developed to simulate the coincident responses of a plastic scintillator and an HPGe detector to the cosmic-ray muons. The detectors are situated in a low-level underground laboratory (25 m.w.e). Primary positions, momentum directions and energies of the muons are sampled from the angular and energy distributions of the cosmic-ray muons at the shallow underground level. Obtained coincident spectra of both detectors are presented and discussed.

Status and New Data of the Geochemical Determination of the pp-Neutrino Flux by LOREX

LOREX (LORandite EXperiment) addresses the determination of the solar (pp) neutrino flux during the last four million years by exploiting the reaction with an incomparably low-energy threshold of 50 keV for the capture of solar neutrinos. The ratio of 205Pb/205Tl atoms in the Tl-bearing mineral lorandite provides, if corrected for the cosmic-ray induced background, the product of the flux of solar neutrinos and their capture probability by 205Tl, averaged over the age of lorandite. To get the mean solar neutrino flux itself, four problems have to be addressed: (1) the geological age of lorandite, (2) the amount of background cosmic-ray-induced 205Pb atoms which strongly depends on the erosion rate of the lorandite-bearing rocks, (3) the capture probability of solar neutrinos by 205Tl and (4) the extraction of lorandite and the appropriate technique to “count” the small number of 205Pb atoms in relation to the number of 205Tl atoms. This paper summarizes the status of items 1 (age) and 3 (neutrino capture probability) and presents in detail the progress achieved most recently concerning the items 2 (background/erosion) and 4 (“counting” of 205Pb atoms in lorandite).

Depopulation of the 6h isomeric state of 99Tc by photon irradiation

The depopulation of 99mTc by the bremsstrahlung radiation of a 15 MeV LINAC has been investigated. A depopulation effect of up to 2% was observed. The effect was found to depend linearly on the absorbed photon flux. The explanation of the effect is discussed qualitatively.

The planets, after all, may run only in perfect circles - but in the velocity space!

On the basis of the laws of conservation of energy and angular momentum we demonstrate that possible trajectories in 1/r fields, represented in the velocity space, are always circles. Different conic sections correspond to different radii of the circles. This approach facilitates the derivation of all the quantities pertaining to the Keplerian problem.

Geochemical Determination of the Solar pp-Neutrino Flux with LOREX: A Progress Report

LOREX (LORandite EXperiment) is a geochemical experiment addressing the solar (pp) neutrino flux for the period of 4.3 Ma from the reaction 205Tl + ve → 205Pb + e- with an unprecedentedly low threshold (52 keV) for solar pp-neutrino capture. A decisive step for this purpose is getting the precise, background-corrected ratio of 205Pb/205Tl in lorandite (TlAsS2). This report presents the status of major challenges being addressed, in particular the determination of the paleo-depth of lorandite, including the eroded layer over 4.3 Ma, as well as the choice of appropriate techniques for extraction, separation and quantitative determination of the ultra-low 205Pb concentration in the extracted lorandite samples.

Neutrons produced by muons at 25 mwe

The flux of fast neutrons produced by CR muons in lead at the depth of 25 mwe is measured. Lead is a common shielding material and neutrons produced in it in muon interactions are unavoidable background component, even in sensitive deep underground experiments. A low background gamma spectrometer, equipped with high purity Ge detector in coincidence with muon detector is used for this purpose. Neutrons are identified by the structure at 692 KeV in the spectrum of delayed coincidences, caused by the neutron inelastic scattering on Ge-72 isotope. Preliminary result for the fast neutron rate is 3.1(5) × 10−-4n/cm2 · s.

ON THE POSSIBILITY TO SIMULTANEOUSLY DETERMINE THE LONG-TERM AVERAGE FLUXES OF SOLAR pp-NEUTRINOS AND COSMIC RAY MUONS

The Allchar mine in the southern FYR Macedonia contains the worlds largest known concentration of thallium bearing minerals. LOREX (acronym for the geo-chemical LORandite EXperiment) is an international collaboration exploring the opportunity to use the rare mineral lorandite (TlAsS2) for the determination of the solar pp-neutrino flux, averaged over the 4.3 million year age of the deposit. Here we discuss the possibility to determine simultaneously both the solar neutrino and the cosmic ray muon flux, averaged over the same period of time. Cosmic-ray muons participate in the reaction 205Tl(μp, n)205Pb, whereas the neutrinos induce the capture reaction 205Tl(νe, e)205Pb* → 205Pb. Both fluxes can in principle be determined by counting the number of atoms of the long-lived 205Pb present in the mineral, produced by both muons and neutrinos in the reactions with the most abundant stable isotope, 205Tl.