69 research outputs found
A new FSA approach for in situ -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, -spectroscopy with sodium
iodide scintillators has been proved to be an excellent tool for in-situ
measurements for the identification and quantitative determination of
-ray emitting radioisotopes, reducing time and costs. Both for
geological and civil purposes not only K, U, and Th have
to be measured, but there is also a growing interest to determine the
abundances of anthropic elements, like Cs and 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
-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
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 -spectra instead of calibration pad spectra. Finally, the new
method has been validated by acquiring -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
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
Effect of Pressure-Assisted Heat Treatment on Photoluminescence Emission of α-Bi2O3 Needles
Materials with high photoluminescence (PL)
intensity can potentially be used in optical and electronic
devices. Although the PL properties of bismuth(III) oxide with a
monoclinic crystal structure (α-Bi2O3) have been explored in
the past few years, methods of increasing PL emission intensity
and information relating PL emission to structural defects are
scarce. This research evaluated the effect of a pressure-assisted
heat treatment (PAHT) on the PL properties of α-Bi2O3 with a
needlelike morphology, which was synthesized via a microwaveassisted
hydrothermal (MAH) method. PAHT caused an
angular increase between the [BiO6]â[BiO6] clusters of α-
Bi2O3, resulting in a significant increase in the PL emission
intensity. The Raman and XPS spectra also showed that the α-
Bi2O3 PL emissions in the low-energy region (below âŒ2.1 eV) are attributed to oxygen vacancies that form defect donor states.
The experimental results are in good agreement with first-principles total-energy calculations that were carried out within
periodic density functional theory (DFT).This research was funded by The State of Sao Paulo Research Foundation (FAPESP), Research Award No. CEPID 2013/07296-2. Author S. Schmidt is grateful to the Coordination for the Improvement of Higher Education Personnel (Capes) for her doctoral scholarship. This work was also supported by Spanish MALTA-Consolider Ingenio 2010 Program (Project CSD2007-00045). The authors are also grateful to Prof. Juan Andrés for his collaboration in the preparation of this article
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
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.
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 âMeasurement of natural radioactivity and
mapping of the radioisotope abundances of Tuscany
Regionâ, 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
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.
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
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 Îł-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 Îł-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 Îł
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
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