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Papers by pavel povinec

Physical review, Jun 23, 2023

We present limits on the spin-independent interaction cross section of dark matter particles with... more We present limits on the spin-independent interaction cross section of dark matter particles with silicon nuclei, derived from data taken with a cryogenic calorimeter with 0.35 g target mass operated in the CRESST-III experiment. A baseline nuclear recoil energy resolution of ð1.36 AE 0.05Þ eV nr , currently the lowest reported for macroscopic particle detectors, and a corresponding energy threshold of ð10.0 AE 0.2Þ eV nr have been achieved, improving the sensitivity to light dark matter particles with masses below 160 MeV=c 2 by a factor of up to 20 compared to previous results. We characterize the observed low energy excess, and we exclude noise triggers and radioactive contaminations on the crystal surfaces as dominant contributions.

Journal of physics, Dec 1, 2021

The CRESST experiment searches for dark matter induced nuclear recoils inside CaWO4 based cryogen... more The CRESST experiment searches for dark matter induced nuclear recoils inside CaWO4 based cryogenic calorimeters at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy. To identify reliably a potential signal, a precise understanding of its background budget is crucial. An important background category could be “cosmogenics”: radionuclides produced via interactions with cosmic rays, mainly during the crystal production at surface facilities. Albeit CaWO4 is a well-established calorimetric material, no systematic study of its susceptibility for cosmic activation existed so far. In this contribution, we will first report the exposure profile of CRESST’s in-house grown TUM93 crystal to cosmic rays. Then we will identify the most prominent cosmogenics via AcTIVIA calculations. Afterwards we discuss the expected background spectrum based on Geant4 simulations and compare it to measurements.

The Japan Radiation Research Society Annual Meeting Abstracts The 47th Annual Meeting of The Japan Radiation Research Society, 2004

Radiocarbon, 2013

Radiocarbon has been used to define parameters for modeling past, recent, and future CO 2 /carbon... more Radiocarbon has been used to define parameters for modeling past, recent, and future CO 2 /carbon amounts in the atmosphere and in other environmental compartments. In the present paper, we estimate the amount of 14 C in the atmosphere by calculating the molar activity of 14 CO 2 (quantity of 14 CO 2 molecules per mol of air). Data on the reconstruction of the past concentration of atmospheric CO 2 from Antarctic ice cores and Δ 14 C activities from the IntCal09 calibration curve were applied. The results obtained indicate that cosmogenic production had a dominant influence on the 14 C amount in the atmosphere between 50 and 20 ka BP, when the CO 2 concentrations were relatively stable, with a slowly decreasing trend. The decreasing 14 C activity (Δ 14 C) between 20 and 2 ka BP seems to be caused predominantly by a dilution of atmospheric 14 CO 2 by input of CO 2 with a depleted amount of 14 C (probably from deeper oceanic layers), which is evident from a comparison with the Δ 14 C and molar activity time series. A strong linear relation was found between the 14 C activity and CO 2 concentration in the air for the period 20-2 ka BP, which confirms a dominant influence of atmospheric dilution of 14 CO 2. The observed linear relation between the CO 2 and Δ 14 C levels persists even in the prevailing part of the Holocene. Likewise, the quantity of 14 CO 2 in the atmosphere (calculated as molar activity) during the prevailing part of the deglacial period (20-11 ka BP) was surprisingly increasing, although a decreasing trend in the 14 C cosmogenic production rate could be expected.

Astroparticle Physics, Oct 1, 2022

The background of a High Purity Germanium (HPGe) detector measured in a deep underground laborato... more The background of a High Purity Germanium (HPGe) detector measured in a deep underground laboratory was investigated analytically and by Monte Carlo simulations using the GEANT4 toolkit. Contributions of different background sources to the experimental γ-ray background were determined. Namely, contribution of radionuclides in materials of the detector and around the detector, neutrons produced by (α, n) reactions due to presence of radionuclides in rock and concrete and by spontaneous fission of mainly 238 U, and finally, cosmic rays with neutron generation. The simulation, including radionuclides in the material, was in a good agreement with the experiment. At the same time, neutron and muon induced spectra were simulated. The radiation coming from the presence of members of the 238 U, and 232 Th decay series, and 40 K in the detector parts and the laboratory walls contribute to the continuum of the experimental spectrum at the level of around 94%. According to simulations, the contribution of muon events to the experimental energy spectrum was below 1% and it was confirmed that muon induced spectra are about three orders of magnitude lower than the experimental one. The comparison of integral count rates of the experimental spectrum with the simulated spectrum induced by neutrons showed that about 6% of the measured background continuum originated from neutron reactions. Fast neutrons contributed more to the background (at around 65%) than thermal neutrons. Despite only a 6% share of neutron contributions in the total γ-ray background, they contributed mainly to the lower continuum of the spectrum up to 250 keV, which is a region of interest for potential low mass weakly interacting massive particle (WIMP) dark matter interactions. In addition, they interact with the detector and the shield by inelastic scattering and induce unwanted γ-rays. Neutron capture, elastic and inelastic scattering were simulated separately as well. It was found that inelastic scattering is the major contributor to the spectrum induced by neutrons. The effect of neutrons on the background of the HPGe detector operating underground, such as Obelix, is manifested mainly by their contribution to the continuum up to 1 MeV, especially in the lower part up to 500 keV. Thus, neutrons are an important background component in deep underground laboratories, too. Possible detector optimization is also discussed.

82nd Annual Meeting of The Meteoritical Society, Jul 1, 2019

Tunnelling and Underground Space Technology, 2007

A new technology based on in situ underwater gamma-ray spectrometry of radon daughter products in... more A new technology based on in situ underwater gamma-ray spectrometry of radon daughter products in water has been applied for groundwater-seawater interaction studies in the coastal regions of SE Sicily (offshore Donnalucata) and SE Brazil (offshore Ubatuba). The continuous monitoring carried out at the Donnalucata (and Ubatuba) site have revealed an inverse correlation between the 222 Rn concentration versus the tides and salinity, as 222 Rn concentrations in seawater varied from 2 kBq m-3 (1 kBq m-3) during high tide to 5 kBq m-3 (5 kBq m-3) during low tide. The observed variations in 222 Rn concentrations are likely caused by sea level changes, as tidal effects induce variations of hydraulic gradient, which can increase 222 Rn concentrations during a falling tide, while during a high tide, 222 Rn concentrations decrease.

Nucleation and Atmospheric Aerosols, 2015

Double electron capture has been of interest of many theoretical and experimental works as a poss... more Double electron capture has been of interest of many theoretical and experimental works as a possible extension of double beta-decay investigations. The neutrinoless double-electron capture, similarly as the neutrinoless double beta-decay may help to clarify if neutrinos are Majorana or Dirac particles. Results obtained in several double electron capture experiments are reviewed and new experiments to be carried out in deep underground laboratories using enriched sources and multidimensional HPGe-HPGe gamma-ray spectrometry with a few years of counting time are proposed, which should be able to improve half-lives limits by at least an order of magnitude.

Journal of Environmental Radioactivity, Oct 1, 2022

Nuclear Instruments and Methods in Physics Research, Oct 1, 2020

Monte Carlo models based on GEANT4, CONUS and ACTIVIA software packages were used for simulation ... more Monte Carlo models based on GEANT4, CONUS and ACTIVIA software packages were used for simulation of production rates of cosmogenic radionuclides in the Obelix HPGe detector operating in the Modane underground laboratory. Interactions of secondary cosmic-ray nucleons with Ge-crystal (production of 3 H, 54 Mn, 57 CO, 65 Zn and 68 Ge), with copper in the cold finger (production of 46 Sc, 54 Mn, 56 Co, 57 Co, 58 Co, 60 Co and 59 Fe), with Al in bauxite ore (production of 26 Al) and with Al-4%Si alloy in the cryostat (production of 22 Na) were included in the calculations. The contribution of cosmogenic radionuclides to the total detector background of the Obelix detector decreased from 39% (after 10 months of cooling down) to 14% (after three years of cooling down). The calculated production rates of cosmogenic radionuclides and simulated gamma-ray spectra were in reasonable agreement with experimental results.

Journal of Environmental Radioactivity, Apr 1, 2018

Nuclear power plants (NPPs) have been one of the sources of anthropogenic radionuclides in the en... more Nuclear power plants (NPPs) have been one of the sources of anthropogenic radionuclides in the environment. This work combines the results from monitoring stations around NPPs in Slovakia (Mochovce and Jaslovské Bohunice) and academic measurements at the Comenius University campus in Bratislava. Most of the atmospheric 137 Cs in this region come from the resuspension of the Chernobyl-derived 137 Cs, as well as caesium produced during nuclear weapons testing. By comparison of the obtained results at NPPs with Bratislava data, radiation impacts of the NPPs on the local environments have been estimated to be negligible.

Journal of Radioanalytical and Nuclear Chemistry, Jan 9, 2017

Chondrites are the most frequently studied extraterrestrial material. We present new data on the ... more Chondrites are the most frequently studied extraterrestrial material. We present new data on the concentrations of 43 major and trace elements found in the Uhrovec, Vel'ké Borové (Nagy-Borove), Rumanová, Košice and Chelyabinsk meteorites, which were analyzed using INAA. The results are in good agreement with the mean data for an average ordinary chondrite of the respective class; normalization of the values to CI chondrites also showed similar outcome. Additionally, for the Rumanová, Košice and Chelyabinsk meteorites, INAA results of the bulk chemical composition are reasonably consistent with the data obtained by the same and/or different methods published earlier.

Journal of Analytical Science and Technology, Dec 22, 2011

Recent developments in ultra low-level radionuclide analyses using radiometrics and mass spectrom... more Recent developments in ultra low-level radionuclide analyses using radiometrics and mass spectrometry methods, which have had important impacts on new applications of radionuclides as tracers of environmental processes are discussed.

Journal of Environmental Radioactivity, Apr 1, 2020

Recently environmental radionuclide signals were observed in the atmosphere which could be associ... more Recently environmental radionuclide signals were observed in the atmosphere which could be associated with undeclared nuclear activities, not directly connected with development of nuclear weapons. Large-scale contamination of European air with Ru-106 observed in 2017 may represent such an accident, which was probably associated with the Mayak nuclear fuel reprocessing facility in the Chelyabinsk region of Russia. A recently announced nuclear accident at Nyonoska in the Archangelsk region may represent an undeclared nuclear activity associated with the development of a nuclear jet engine which could be based on radionuclide energy generator or a small nuclear reactor. It is concluded that environmental radioactivity impacts associated with recent nuclear activities create new challenges for fast and reliable national and international monitoring systems which would require development of new monitoring strategies.

Solar System Research, Mar 1, 2019

Cosmogenic radionuclides with half-life periods T 1/2 ranging from several days to a million year... more Cosmogenic radionuclides with half-life periods T 1/2 ranging from several days to a million years, produced in the nuclear reactions of galactic cosmic rays (GCR) with meteoritic matter, provide valuable information on the GCR intensity variations on a long time scale (~1 million years) within meteorite orbits 2-4 AU from the Sun. Information on the variations of GCR gradients in the inner heliosphere was obtained by comparing the measured contents of 54 Mn and 22 Na in stone meteorites (chondrites) with known orbits at the time of their fall to Earth with the calculated production rates of these radionuclides in them using balloon intensity measurements of GCR (E > 100 MeV) in the stratosphere at appropriate times. Although individual gradient values show significant uncertainties, the important information is that cosmogenic radionuclides in chondrites predict low gradients (0-10% per 1 AU) for all periods of minimum solar activity in 1957-2013, according to direct measurements in interplanetary space. High gradients (50-100% per 1 AU) are predicted for periods of maximum solar activity, especially in 1992 and 2012 (up to ~200% per 1 AU). Average values of gradients are (20 ± 10)% per 1 AU for modern solar cycles (according to the production rate of 22 Na), similar to the average values for the last ~1 million years (according to the production rate of 26 Al), which indicates the constancy of the solar modulation of the GCR, at least for the last million years.