A new FSA approach for in situ γ\gamma-ray spectroscopy

An increasing demand of environmental radioactivity monitoring comes both from the scientific community and from the society. This requires accurate, reliable and fast response preferably from portable radiation detectors. Thanks to recent improvements in the technology, $\gamma$-spectroscopy with sodium iodide scintillators has been proved to be an excellent tool for in-situ measurements for the identification and quantitative determination of $\gamma$-ray emitting radioisotopes, reducing time and costs. Both for geological and civil purposes not only $^{40}$K, $^{238}$U, and $^{232}$Th have to be measured, but there is also a growing interest to determine the abundances of anthropic elements, like $^{137}$Cs and $^{131}$I, which are used to monitor the effect of nuclear accidents or other human activities. The Full Spectrum Analysis (FSA) approach has been chosen to analyze the $\gamma$-spectra. The Non Negative Least Square (NNLS) and the energy calibration adjustment have been implemented in this method for the first time in order to correct the intrinsic problem related with the $\chi ^2$ minimization which could lead to artifacts and non physical results in the analysis. A new calibration procedure has been developed for the FSA method by using in situ $\gamma$-spectra instead of calibration pad spectra. Finally, the new method has been validated by acquiring $\gamma$-spectra with a 10.16 cm x 10.16 cm sodium iodide detector in 80 different sites in the Ombrone basin, in Tuscany. The results from the FSA method have been compared with the laboratory measurements by using HPGe detectors on soil samples collected in the different sites, showing a satisfactory agreement between them. In particular, the $^{137}$Cs isotopes has been implemented in the analysis since it has been found not negligible during the in-situ measurements.Comment: accepted by Science of Total Environment: 8 pages, 10 figures, 3 table

Preliminary results for the characterization of the radiological levels of rocks in Tuscany Region

http://www.fe.infn.it/u/mantovani/CV/Proceedings/Bezzon_10a.pd

Preliminary results for the characterization of the radiological levels of rocks in Tuscany Region.

The environmental background levels of natural radiation due to the nuclides in rocks vary in significant amounts that depend on the geological and geomorphological features of a territory. The main source of terrestrial gamma-ray radiation exposure to humans is from 238U, 232Th decay chains and 40K decay. This paper reports a part of the results of the Research Project “Measurement of natural radioactivity and mapping of the radioisotope abundances of Tuscany Region”, which started at August 2008 and it is supported by founds of Tuscany Region. The aim of this project is to realize the thematic maps of radioactivity content and in particular of the abundances of eU1, eTh1 and 40K. These goals will be achieved by integrating the information from measurements on samples in laboratory with in-situ investigations and airborne surveys. The Legnaro National Laboratory (LNL) is the national leader for the design and realization of high-resolution gamma-ray spectrometers, portable and massive NaI(Tl) detectors. The MCA_Rad gamma-ray spectrometry system was designed and built up at LNL for measuring large amount of samples with a minimum attendance: these features fit perfectly with the requirements of this project. This system is able to measure any type of materials (solid, liquid, gas), and due to the high efficiency and its geometric symmetry, absolute activity measurements are possible with systematic errors below 5%. http://www.fe.infn.it/u/mantovani/CV/Proceedings/Bezzon_10b.pd

Mapping of natural radioelements using gamma-ray spectrometry: Tuscany Region case of study.

http://www.fe.infn.it/u/mantovani/CV/Proceedings/Bezzon_11a.pd

The 3He(alpha,gamma)7Be S-factor at solar energies: the prompt gamma experiment at LUNA

The 3He(alpha,gamma)7Be process is a key reaction in both Big-Bang nucleosynthesis and p-p chain of Hydrogen Burning in Stars. A new measurement of the 3He(alpha,gamma)7Be cross section has been performed at the INFN Gran Sasso underground laboratory by both the activation and the prompt gamma detection methods. The present work reports full details of the prompt gamma detection experiment, focusing on the determination of the systematic uncertainty. The final data, including activation measurements at LUNA, are compared with the results of the last generation experiments and two different theoretical models are used to obtain the S-factor at solar energies.Comment: Accepted for publication in Nucl. Phys.

Ultra-sensitive in-beam gamma-ray spectroscopy for nuclear astrophysics at LUNA

Ultra-sensitive in-beam gamma-ray spectroscopy studies for nuclear astrophysics are performed at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400 kV accelerator, deep underground in Italy's Gran Sasso laboratory. By virtue of a specially constructed passive shield, the laboratory gamma-ray background for E_\gamma < 3 MeV at LUNA has been reduced to levels comparable to those experienced in dedicated offline underground gamma-counting setups. The gamma-ray background induced by an incident alpha-beam has been studied. The data are used to evaluate the feasibility of sensitive in-beam experiments at LUNA and, by extension, at similar proposed facilities.Comment: accepted, Eur. Phys. J.

Superconducting RFQs

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A multivariate spatial interpolation of airborne {\gamma}-ray data using the geological constraints

In this paper we present maps of K, eU, and eTh abundances of Elba Island (Italy) obtained with a multivariate spatial interpolation of airborne {\gamma}-ray data using the constraints of the geologic map. The radiometric measurements were performed by a module of four NaI(Tl) crystals of 16 L mounted on an autogyro. We applied the collocated cokriging (CCoK) as a multivariate estimation method for interpolating the primary under-sampled airborne {\gamma}-ray data considering the well-sampled geological information as ancillary variables. A random number has been assigned to each of 73 geological formations identified in the geological map at scale 1:10,000. The non-dependency of the estimated results from the random numbering process has been tested for three distinct models. The experimental cross-semivariograms constructed for radioelement-geology couples show well-defined co-variability structures for both direct and crossed variograms. The high statistical correlations among K, eU, and eTh measurements are confirmed also by the same maximum distance of spatial autocorrelation. Combining the smoothing effects of probabilistic interpolator and the abrupt discontinuities of the geological map, the results show a distinct correlation between the geological formation and radioactivity content. The contour of Mt. Capanne pluton can be distinguished by high K, eU and eTh abundances, while different degrees of radioactivity content identify the tectonic units. A clear anomaly of high K content in the Mt. Calamita promontory confirms the presence of felsic dykes and hydrothermal veins not reported in our geological map. Although we assign a unique number to each geological formation, the method shows that the internal variability of the radiometric data is not biased by the multivariate interpolation.Comment: 43 pages, 9 figures, 5 tables. In Remote Sensing of Environment (2013

A γ-Spectroscopy System for Atmospheric Radon Detection

Radon isotopes and their decay products cause most of the natural radioactivity in atmosphere at ground level (Jacobi, 1964; Altshuler et al., 1964; UNSCEAR, 1988, 1993; Porstendorfer, 1994; Kathren, 1998). 222Rn (Radon) and 220Rn (Thoron) enter the atmosphere from the Earths surface, where they are produced via radioactive decay of the precursors 238U and 232Th respectively. The major contribution to the natural radioactivity dose is from the inhalation of the daughters of this gas. They are attached to very fine particles (Bergamini et al., 1973; Porstendorfer, 1994; Mohammed et al., 2000) and deposit on the surface of the different parts of the respiratory system with a probability dependent on aerosol particle sizes (ICRP, 1994). The dynamics of the gas could be similar to that of the atmospheric particulate and the daily change in concentration can be correlated to it. The γ-rays produced by the Radon daughters come both from the earth surface and from the radon contained in the air. For a detector placed in a fixed position, the first contribution remains constant over the time while the second follows the change in gas concentration in air. In order to determine the two contributions a system composed by three sodium iodide detectors has been designed and installed on a tower at the LNL (Laboratori Nazionali di Legnaro). The aim of this project is to understand the behavior of γ emissions from ground surface at different altitudes and also to study the correlation between the atmospheric conditions, like the altitude of the atmosphere inversion layer, and the radon concentration in air. http://www.fe.infn.it/u/mantovani/CV/Proceedings/Bezzon_11b.pd

Astrophysical S-factor of the 3He(alpha,gamma)7Be reaction measured at low energy via prompt and delayed gamma detection

Solar neutrino fluxes depend both on astrophysical and on nuclear physics inputs, namely on the cross sections of the reactions responsible for neutrino production inside the Solar core. While the flux of solar 8B neutrinos has been recently measured at Superkamiokande with a 3.5% uncertainty and a precise measurement of 7Be neutrino flux is foreseen in the next future, the predicted fluxes are still affected by larger errors. The largest nuclear physics uncertainty to determine the fluxes of 8B and 7Be neutrinos comes from the 3He(alpha,gamma)7Be reaction. The uncertainty on its S-factor is due to an average discrepancy in results obtained using two different experimental approaches: the detection of the delayed gamma rays from 7Be decay and the measurement of the prompt gamma emission. Here we report on a new high precision experiment performed with both techniques at the same time. Thanks to the low background conditions of the Gran Sasso LUNA accelerator facility, the cross section has been measured at Ecm = 170, 106 and 93 keV, the latter being the lowest interaction energy ever reached. The S-factors from the two methods do not show any discrepancy within the experimental errors. An extrapolated S(0)= 0.560+/-0.017 keV barn is obtained. Moreover, branching ratios between the two prompt gamma-transitions have been measured with 5-8% accuracy.Comment: to be published in Physical Review