A. Pakou

Natural radioactivity and radon emanation factors in building material used in Epirus (north-western Greece)

The natural radioactivity (228Ac, 226Ra, 40K) in typical building materials of the north-western part of Greece (Epirus), has been measured. The results are discussed in terms of limits to the accepted natural radioactivity levels and are compared with similar values reported in the literature. Radon emanation factors have also been determined via γ-spectroscopy.

The propagation of the Chernobyl 131I impulse through the air-grass-animal-milk pathway in Northwestern Greece

A three-compartment (air- grass-milk) milk contamination model for 131I has been applied to atmospheric, grass and milk data, following the April 1986 nuclear accident at Chernobyl. Samples of ovine and bovine milk collected daily by a large dairy company in Ioannina (northwestern Greece), throughout the month of May 1986 have been employed. The contamination impulse in the area, which provides the input to the model, has been approximated by a first order gamma-variate curve. Transfer rates and decay constants have been extracted by fitting predictions of the model independently to each set of data (air, grass and milk). All model parameters obtained from more than one set of data show remarkable consistency. These parameters are used to calculate the transfer coefficients fm for the transport of radioiodine at equilibrium for sheep and cows.

Reaction mechanisms of the7Li+51V reaction

Reaction mechanisms populating the exit channels of the system7Li+51V were studied at a beam energy of 18 MeV. Final nuclei were detected by their characteristicγ-rays. Theseγ-rays in coincidence with light charged particles were used to identify the reaction channels. Also forward-backward asymmetries of the coincident events gave a measure of the contribution of direct and compound reaction mechanisms.It was found that the dominant mechanism feeding channels with charged particles in the final state is direct transfer of a triton orα particle.

The NUMEN project: NUclear Matrix Elements for Neutrinoless double beta decay

Abstract.The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the fact that the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270MeV give an encouraging indication on the capability of the proposed technique to access relevant quantitative information. The main experimental tools for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy-ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than those manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article.

AstrophysicalS(E) factor of8Li (α,n0)11B and inhomogeneous Big Bang nucleosynthesis

The cross section of the11B(n, α)8Li reaction has been measured atEn=7.6 to 12.6 MeV. The neutron beam was produced via theD(d, n)3He reaction and aBF3 counter (with naturalB isotopic composition) served both as target for the11B nuclides and as detector for the observation of the delayedα-activity of8Li. The data match well with previous results obtained atEn=12.5 to 20.0 MeV. Using the principle of detailed balance the data were converted to the case of the8Li(α, n0)11B reaction. The associated astrophysicalS(E) factor is dominated by a resonance atER=0.58 MeV of widthΓR =200 keV, withS(ER)=8400 MeV b. ThisS (ER) value for the n0 channel alone is already three times higher than the constantS(E) factor assumed previously and, thus, strengthens the significance of inhomogeneous Big Bang nucleosynthesis.

X-ray production by Pt and Os projectiles moving in thick Fe targets withE p =17−30 MeV

X-ray spectra produced by Pt and Os bombardment of Fe targets have been measured in the projectile energy range ofEp=17 to 30 MeV. The thick target yields of the Fe K-shell and Pt and Os M-shells were analyzed within the Landau-Zener model. M-vacancy fractions, their respective lifetimes, and the level-crossing radii for the Pt−Fe and Os−Fe encounters were deduced. The results are discussed with emphasis on the mechanism of transient magnetic fields.

Elastic scattering for the system 6Li+p at near barrier energies with MAGNEX

Elastic scattering measurements have been performed for the {sup 6}Li+p system in inverse kinematics at the energies of 16, 20, 25 and 29 MeV. The heavy ejectile was detected by the large acceptance MAGNEX spectrometer at the Laboratori Nazionali del Sud (LNS) in Catania, in the angular range between ∼2{sup 0} and 12{sup 0} in the laboratory system, giving us the possibility to span almost a full angular range in the center of mass system. Results will be presented and discussed for one of the energies.

Scattering process for the system 7Be + 58Ni at 23.2 MeV beam energy

We measured for the first time the scattering process of 7Be nuclei from a 58Ni target at 23.2 MeV beam energy. The experiment was performed at the Laboratori Nazionali di Legnaro (LNL, Italy), where the 7Be Radioactive Ion Beam was in-flight produced with the facility EXOTIC. Charged reaction products were detected by means of the detector array DINEX, arranged in a cylindrical configuration around the target to ensure a polar angle coverage in the ranges θcm = 40°-80° and 110°-150°. The scattering differential cross section was analyzed within the optical model formalism with the coupled-channel code FRESCO to extract the total reaction cross section. The result was compared with those obtained at lower beam energies in an earlier experiment performed at the University of Notre Dame (USA). At the present stage of our analysis, the two data sets were found to be not fully consistent each other.

Interaction of He8 with Pb208 at near-barrier energies: He4 and He6 production

The authors would like to thank the staff of the GANIL accelerator facility for providing the high-quality 8He beam. This work was supported in part by Grants No. FPA-2010-22131-CO2-01 (FINURA) and No. FPA2013-47327-C2-1-R from the Spanish Ministry of Economy and Competitiveness, UNAM-PAPIIT IA103218 (Mexico); Grant No. N202 033637 from the Ministry of Science and Higher Education of Poland; the National Science Centre of Poland under Contracts No. 2013/08/M/ST2/00257 (LEA-COPIGAL) and No. 2014/14/M/ST2/00738 (COPIN-INFN Collaboration); and Grant No. EUI2009-04163432 (EUROGENESIS) from the European Science Foundation.

Data reduction for experimental measurements within the NUMEN project

Within the NUMEN project, we present experimental issues and data reduction for the Cd(Ne,F)In single charge exchange, Cd(Ne,O)In two-proton transfer and Cd(Ne,F)In one-proton transfer reactions at 15 AMeV incident energy.