A complete and detailed analysis of alpha spectra from the 222Rn and 220Rn progenies was performed by newly developed software. The software identifies the alpha peaks, performs appropriate fits and ...calculates the net area and its uncertainty, considering the entire background. The deconvolution of the overlapped peaks of 218Po and 212Bi allows us also to evaluate their minimum detectable area. The efficiency of the electrostatic detection method was recalculated and new useful considerations on the collected alpha emitters were made.
•A complete software for analysis of RaMonA alpha spectra is presented.•The alpha peak shape is appropriately fitted.•The deconvolution of the overlapped peaks is resolved.•Radon and Thoron progenies spectrometry after electrostatic collection.•The efficiencies of the Radon and Thoron alpha progenies were studied.
The interest in the measurement of thoron (220Rn) activity concentration in air has recently increased, with the attention for the development of standards useful for the calibration of measuring ...instruments. Due to its short half-life (55.8 s), consolidated techniques for the realization and the use of controlled atmospheres of radon (222Rn) are not effective in the case of thoron. New adequate methodology are required. A method for the measurement of the thoron reference activity based on the direct detection of the alpha particles produced by the decay of 220Rn, from natural samples containing 232Th, is here proposed. The possibility of observing an acceptable spectrum is entrusted to the realization of measurement chambers small enough to reduce as much as possible the energy loss of the alpha particles before they reach the Silicon detector. Such a chamber was realized and used with a known thoron atmosphere in a controlled environment. The experimental results are compared with those obtained from the simulation with the Monte Carlo method: (i) the alpha spectra coming directly from thoron atoms exhibit similar shape with a linear trend plus an exponential trend on the left side of the 220Rn peak, depending from the distance between source and detector; (ii) the corresponding 220Rn detection efficiency values are compatible considering the uncertainties. An investigation was conducted to study the shape of the 220Rn spectra vs the different volume of chambers, through Monte Carlo simulations. The results show: (i) the linear part of the spectra shape goes to reduce with the increasing of the height of the chamber; (ii) the 220Rn detection efficiency decreases with the increasing of the height of the chamber.
•Small chamber for collection of α-particles produced by 220Rn atoms.•Measured detection efficiency agrees to Monte Carlo simulation within uncertainty.•Measured alpha spectrum shows similar shape of the simulated one.•Second chamber is designed, with double-sided Si detector, to increase the counts.•Detection efficiency decreases with increasing of the height of the chamber.
Flowing plasma jets are increasingly investigated and used for surface treatments, including biological matter, and as soft ionization sources for mass spectrometry. They have the characteristic ...capability to transport energy from the plasma excitation region to the flowing afterglow, and therefore to a distant application surface, in a controlled manner. The ability to transport and deposit energy into a specimen is related to the actual energy transport mechanism. In case of a flowing helium plasma, the energy in the flowing afterglow may be carried by metastable helium atoms and long-lived helium dimer ions. In this work a systematic investigation of the optical and spectroscopic characteristics of a supersonic flowing helium plasma in vacuum and its afterglow as function of the helium gas density is presented. The experimental data are compared with numerical modeling of the plasma excitation and helium dimer ion formation supported by a Computational Fluid Dynamic simulation of the helium jet. The results indicate that the plasma afterglow is effectively due to helium dimer ions recombination via a three-body reaction.
The reaction Be(p7,γ)8B plays an important role in the Sun, where it determines the high energy component of the solar neutrino spectrum. The importance of this reaction triggered several experiments ...over the last decades. A combined analysis of their results produces an overall consistent picture for the energy dependence of the cross section, while an inflation of the quoted uncertainties is needed to accommodate the observed discrepancy in the absolute scale of the different data sets. The origin of this discrepancy needs to be understood for a reliable estimate of the astrophysical rate of Be(p7,γ)8B and its uncertainty. In addition, there is a question about possible common systematic effects, considering that all measurements performed so far share the same experimental approach, i.e. an intense proton beam impinging on a Be7 radioactive target. A direct measurement using a radioactive Be7 ion beam on a pure hydrogen gas target has been since long envisioned as a way to improve the situation. First attempts showed the feasibility of an experiment based on the use of a recoil mass separator to collect reaction products with high efficiency, but failed to reach a useful statistical significance because of the low beam intensity. Here we present the results obtained using the intense Be7 beam available at the Tandem Accelerator Laboratory at CIRCE, University of Campania, Italy coupled to the recoil mass separator ERNA in the energy range Ecm=367 to 812 keV. Our results are compatible only with a part of previous measurements, in particular those indicating a low value of the astrophysical S-factor at zero energy S17, thus exacerbating the discrepancy between existing measurements. The analysis of our data together with the results of previous data provides an estimate S17(0)=20.0±0.8 eV⋅b, where systematic uncertainties are inflated to obtain a statistically compatible data set.
The assessment of the radiological impact of decommissioning activities at a nuclear power plant requires a detailed analysis of the distribution of radionuclides in the environment surrounding it. ...The present work concerns data of three campaigns carried out during the last twenty years in the plain of the Garigliano river surrounding the Garigliano Nuclear Power Plant (GNPP), which is located in Southern Italy and shut down in 1979. Moreover, some data from surveys held in the eighties, across the Chernobyl accident, have been taken in account. The results for the soil samples, in particular for 137Cs and 236U specific activity, were analyzed for their extension in space and in time. Some of the problems related to the classical analysis of environmental radiological data (non-normal distribution of the values, small number of sample points, multiple comparison and presence of values lesser than the minimum detectable activity) have been overcome with the use of Bayesian methods.
The scope of the paper is threefold: (1) to introduce the data of the last campaign held in the Garigliano plain; (2) to insert these data in a larger spatio-temporal frame; (3) to show how the Bayesian approach can be applied to radiological environmental surveys, stressing out its advantages over other approaches, using the data of the campaigns.
The results show that radionuclides specific activity in soil is dominated by the natural sources with the contribution of the atmospheric fallout. A detailed study was performed on the 137Cs data to evaluate both their statistical distribution and the trend over the space and the time. It results that (i) no new contribution there was in the last decades, (ii) specific activity values of the area surrounding the GNPP are consistent with those obtained in other farther areas, (iii) the effective depletion half-life factor for 137Cs is much lower than the half-life of the radionuclide.
•The Bayesian approach in the study of environment has some clear-cut benefits.•Specific activity in soil is dominated by the atmospheric fallout.•Effective half-life factor for 137Cs is much lower than that of the radionuclide.
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A new detection array called GASTLY (GAs-Silicon Two-Layer sYstem) has been designed to detect and identify low-energy light particles emitted in nuclear reactions of astrophysical interest. ...Devoted to the measurement of nanobarn cross-sections, the system is optimised for large solid angle coverage and for low-energy detection thresholds. The array consists of eight modules, each comprising an ionisation chamber and a large area silicon strip detector. Its modularity and versatility allow for use in a variety of experiments. Here we report on the performance of the array as obtained during its commissioning phase with standard
α
-particle sources and during in-beam tests with an intense
12
C beam. Typical energy resolutions
Δ
E
(
FWHM
)
/
E
of about 3% and 2% were obtained for the ionisation chambers and the silicon detectors, respectively. The status of the development of individual strip readout, based on ASIC technology, is also presented.
The assessment of the radiological impact of decommissioning activities at a Nuclear Power Plant requires a detailed mapping of the distribution of radionuclides both in the environment surrounding ...the NPP and in its structural material. The detection of long-lived actinide isotopes and possibly the identification of their origin is particularly interesting and valuable if ultrasensitive measurement of the relative abundance of U isotopes is performed via Accelerator Mass Spectrometry (AMS). In this paper we present an investigation carried out on the structural materials of the Garigliano NPP aiming to determine the abundance of 235,236,238U in the various compartments of the plant buildings under decommissioning. Since the expected values both for isotopic ratios and total U concentrations range over different orders of magnitude, we have developed a novel methodology for the measurement of 234,235U/238U isotopic ratios in low U concentration samples. This allowed a systematic investigation of the distribution of all U isotopes in concrete and metal matrices of the NPP. The behavior of 235,236U/238U isotopic ratios in the different compartments of the NPP is discussed. The correlation of these ratios with 60Co and 137Cs specific activities is also studied to show a different behavior for concrete and metal samples. These data represent a very valuable information to direct the decommissioning procedures under course.
The observation of oxygen isotopes in giant stars sheds light on mixing processes operating in their interiors. Due to the very strong correlation between nuclear burning and mixing processes it is ...very important to reduce the uncertainty on the cross sections of the nuclear reactions that are involved. In this paper we focus our attention on the reaction O18(p,γ)19F. While the O18(p,α)15N channel is thought to be dominant, the (p,γ) channel can still be an important component in stellar burning in giants, depending on the low energy cross section. So far only extrapolations from higher-energy measurements exist and recent estimates vary by orders of magnitude. These large uncertainties call for an experimental reinvestigation of this reaction. We present a direct measurement of the O18(p,γ)19F cross section using a high-efficiency 4π BGO summing detector at the Laboratory for Underground Nuclear Astrophysics (LUNA). The reaction cross section has been directly determined for the first time from 140 keV down to 85 keV and the different cross section components have been obtained individually. The previously highly uncertain strength of the 90 keV resonance was found to be 0.53 ± 0.07 neV, three orders of magnitude lower than an indirect estimate based on nuclear properties of the resonant state and a factor of 20 lower than a recently established upper limit, excluding the possibility that the 90 keV resonance can contribute significantly to the stellar reaction rate.
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