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A study about the 12C(18O, 16O)14C two-neutron transfer reaction was performed at the Catania INFN-LNS laboratory at 84 MeV incident energy. The 16O ejectiles produced in the reactions were momentum analyzed and identified by the MAGNEX spectrometer. The Q-value spectrum of 14C shows several known bound and resonant states, in particular states with 2p-4h configuration respect to the 16O core. The integrated cross sections show an enhanced yield for the two-neutron transfer compared to the one-neutron transfer. These results are some experimental evidences that the (18O, 16O) reaction proceeds mainly by the direct transfer of the neutron pair, instead of a second order process.

[1] On two occasions, sudden gravity changes occurred simultaneously at two summit Etna's stations, during local low-magnitude earthquakes. A systematic coupling between earthquakes inducing comparable maximum acceleration and displacement at the observation points and gravity steps is missing, implying (1) the non-instrumental nature of the steps and (2) the need for particular underlying conditions for the triggering mechanism(s) to activate. We review some of the volcanological processes that could induce fast underground mass redistributions, resulting in gravity changes at the surface. These processes involve bubbles and crystals present in the magma and require particular conditions in order to be effective as mass-redistributing processes. The gravity steps could be a geophysical evidence of the dynamical stress transfer between tectonic and magmatic systems at a local scale. Given the implications that these transfers may have on the volcanic activity, routine volcano monitoring should include the observation of fast gravity changes.

[1] During the last few decades, joint investigations of microgravity and surface deformation measurements have played an increasingly important role in studying the internal dynamics of active volcanoes. Deformation and microgravity observations have been accomplished at Mt Etna since the eighties. Past data sets collected during important paroxysmal events can be utilized as case-studies to both (1) test the possibilities of nowadays more powerful inversion tools and improved analytical formulations to model the source-mechanisms of volcano-related deformation and gravity changes and (2) in turn obtain new insights into the functioning of the plumbing system of the volcano. Here we analyze a data set spanning the March 1981 eruption of Mt. Etna. Large horizontal displacements were evidenced on the NE and SW flanks of the volcano through electrooptical distance measurements (EDM) during two 20-month periods, both encompassing the March 1981 eruption. Elevation changes, evidenced through leveling measurements, during a 12-month period spanning the eruption, were in general smaller than horizontal displacements with important amplitudes only close to the eruptive fissure. Gravity measurements, carried out together with leveling measurements, evidenced positive changes, spatially well correlated with elevation changes, but having a larger wavelength. The joint inversion of the multimethod geophysical data is regarded as a multiobjective optimization problem and solved through a Genetic Algorithm technique of the nondominated type. We conclude that a composite intrusive mechanism with two tensile cracks, each associated to a zone where preexisting microfractures were filled with new magma, leaded to the 1981 eruption. The results of the present study highlight the advantages of multiobjective evolutionary algorithms, as a powerful tool to jointly invert multimethod geophysical data, and pose important issues on the subject of volcano-monitoring.

[1] During the December 2005-January 2006 non-eruptive period, the tremor amplitude at Etna markedly increased and negatively correlated with the gravity signal from one of the two summit station, over 2-3 hour periods. No correlation was found with the signal from the other gravity station. We locate the tremor source by inverting the spatial distribution of seismic amplitudes. Relying on the relative position of the two stations, we define a volume within which the gravity source must lie. During the period of marked anti-correlation, the tremor sources intersect this volume in a region located 1 km S-SE of the summit craters and about 2 km beneath the surface. This finding suggests that the anti-correlation marks the activation of a joint source process, possibly related to the arrival of fresh magma and the consequent gas separation. Our study has implications for the early recognition of gas segregation processes at active volcanoes.

Time-dependent gravimetric measurements can detect subsurface processes long before magma flow leads to earthquakes or other eruption precursors. The ability of gravity measurements to detect subsurface mass flow is greatly enhanced if gravity measurements are analyzed and modeled with ground-deformation data. Obtaining the maximum information from microgravity studies requires careful evaluation of the layout of network benchmarks, the gravity environmental signal, and the coupling between gravity changes and crustal deformation.When changes in the system under study are fast (hours to weeks), as in hydrothermal systems and restless volcanoes, continuous gravity observations at selected sites can help to capture many details of the dynamics of the intrusive sources. Despite the instrumental effects, mainly caused by atmospheric temperature, results from monitoring at Mt. Etna volcano show that continuous measurements are a powerful tool for monitoring and studying volcanoes. Several analytical and numerical mathematical models can beused to fit gravity and deformation data. Analytical models offer a closed-form description of the volcanic source. In principle, this allows one to readily infer the relative importance of the source parameters. In active volcanic sites such as Long Valley caldera (California, U.S.A.) and Campi Flegrei (Italy), careful use of analytical models and high-quality data sets has produced good results. However, the simplifications that make analytical models tractable might result in misleading volcanological interpretations, particularly when the real crust surrounding the source is far from the homogeneous/isotropic assumption. Using numerical models allows consideration of more realistic descriptions of the sources and of the crust where they are located (e.g., vertical and lateral mechanical discontinuities, complex source geometries, and topography). Applications at Teide volcano (Tenerife) and Campi Flegrei demonstrate the importance of this more realistic description in gravity calculations.

The interpretation of the potential fleld data is an useful tool that allows for both investigating the subsurface structures and providing a quantitative evaluation of the geophysical process preceding and accompanying period of volcanic unrest. Potential fleld inversion problem are required to combine forward models with appropriate optimization algorithms and automatically flnd the best set of parameters that well matches the available observations. Indeed, investigations on the mathematical equations to be inverted, have revealed that these models are ill-posed and highly non-linear. Numerical methods for modeling potential fleld observations are proposed and applied on real dataset.

The 9Li + 2H reaction has been investigated at 11 AMeV incident energy at the ISAC II facility (TRIUMF). In the present paper we focus on the one-neutron transfer channel, which potentially holds spectroscopic information on the unbound nucleus 10Li. The TUDA setup has been used in order to detect and identify the outgoing 9Li at forward angles and the recoil protons at backward angles. This setup allows to study the 10Li emitted in the crucial region at forward angles in the center of mass.

Spring gravimeters are still the most utilized instruments for microgravity studies because of their relatively low cost and small size, which make them easy to transport and install. Several authors have demonstrated that meteoric parameters, especially atmospheric temperature, affect continuously running spring gravimeters. In this paper, a non-linear compensation paradigm is applied to the signal from a gravimeter, installed at two different sites, with the aim of removing the effect of meteorological perturbations. The adopted strategy prove to be site-independent as the signals from both installation sites is reduced effectively for the effect of ambient temperature changes. Conversely, through a second experiment, it is demonstrated that the mechanism triggering the temperature effect on the gravity signal is site dependent.

Gravity measurements are utilized at active volcanoes to detect mass changes linked to magma transfer processes and thus to recognize forerunners to paroxysmal volcanic events. Continuous gravity measurements are now increasingly performed at sites very close to active craters, where there is the greatest chance to detect meaningful gravity changes. Unfortunately, especially when used against the adverse environmental conditions usually encountered at such places, gravimeters have been proved to be affected by meteorological parameters, mainly by changes in the atmospheric temperature. The pseudo-signal generated by these perturbations is often stronger than the signal generated by actual changes in the gravity field. Thus, the implementation of well-performing algorithms for reducing the gravity signal for the effect of meteorological parameters is vital to obtain sequences useful from the volcano surveillance standpoint. In the present paper, a Neuro-Fuzzy algorithm, which was already proved to accomplish the required task satisfactorily, is tested over a data set from three gravimeters which worked continuously for about 50 days at a site far away from active zones, where changes due to actual fluctuation of the gravity field are expected to be within a few microgal. After accomplishing the reduction of the gravity series, residuals are within about 15 μGal peak-to-peak, thus confirming the capabilities of the Neuro-Fuzzy algorithm under test of performing the required task satisfactorily.

At Mt Etna a gravity network for discrete measurements has been regularly surveyed since 1987. An increase in gravity before the 1989 eruption has been attributed to the accumulation of magma (1.7x109 m 3 ) in an elongate zone, oriented NNW-SSE, between 2.5 and 6 km below sea level. The 1991-1993 eruption was preceded by shallower gravity increases along the dry fracture developed during the 1989 eruption. These increases were modelled in terms of passive dyke intrusion into the fracture. A new strong gravity increase was detected between June and September 1992 and is consistent with the arrival in the same deep accumulation zone of 2.2x10 9 m 3 of new magma, which allowed continued flank effusion until 1993. Localized gravity variations caused by magma level changes inside the upper levels of the central conduits marked the final stage of the 1991-1993 eruption. Between September 1994 and July 1996 mass redistributions within the volcanic edifice were detected and correlated with the ensuing 1995-96 explosive summit activity. Meanwhile, independent measurements detected some 3x10 8 m 3 of magma accumulating 2-3 km below sea level within the usual NNW-SSE trending elongate zone between October 1995 and November 1996. Three continuously running stations have also been installed at Mt Etna since 1997. High-quality data sequences have been acquired even at sites close to the volcano summit craters. Once the effect of external perturbations has been removed, continuous gravity changes acquired at PDN station are within 10 μGal of gravity changes assessed simultaneously by discrete relative observations at a site very close to the continuous station.

[1] In October 2002 a new eruption began at Etna. Lava flows were issued from two different fissure systems on the NE and S flanks of the volcano. A continuous microgravity sequence, acquired at a station on the N slope (2800 m a.s.l.), shows a marked decrease (about 400 μGal in less than one hour) about 4 hours before lava was first emitted from the eruptive fissures along the NE-Rift. This anomaly reversed soon afterward at a high rate. The strong gravity decrease is interpreted as the opening, by external forces, of a shallow fracture system 1 km W of the gravity station. Magma from the central conduit entered the new fracture system passively, and propagated through it towards lower portions of the NE-Rift. Both the arrangement of the new fracture system and the eruptive dynamics are in keeping with the inferred intrusive mechanism.

[1] Discrete gravity data were acquired at Mount Etna over a period lasting more than a year and spanning the July–August 2001 flank eruption. The gravity measurements were made using a Scintrex CG-3M gravimeter along two profiles of Etna's gravity network. The gravity data indicate that during the second half of 2000, a mass increase of 2 × 1010 kg took place about 1.5 km below the summit craters zone. It is thought to be due to a magma accumulation. A comparable mass decrease was detected during a 4-month period encompassing the eruption which is thought to be the result of withdrawal of the same magma. The gravity data also show that a mass decrease of 2.5 × 1011 kg occurred between January and 19 July 2001 (2 days after the start of the eruption), below the southeastern sector of the volcano, within a volume around 2.5 km below sea level. This decrease was followed by a sudden increase that, in 14 days, partially compensated the previous variation. Since many tensional earthquakes took place during the first half of 2001, within the same source volume of the inferred mass decrease, it is reasonable to assume that the variation observed before the eruption reflects the formation of new voids by tectonic tensile stresses below the volcano edifice. Magma was emplaced along the new formed path from a deep storage to higher levels of Etna's plumbing system, setting off the eruption and causing the gravity increase observed soon after its start. Vulcanological, petrological, and ground deformation studies agree with the assumption of a batch of magma coming directly from a deep storage to have supplied most material extruded during the eruption.

The 12 C( 18 O, 16 O) 14 C reaction has been studied at 84 MeV incident energy. The ejectiles have been momentum analysed at forward angles by the MAGNEX magnetic spectrometer. The energy spectra were obtained up to about 20 MeV excitation energy. Calculations based on the removal of two uncorrelated neutrons from the projectile describe a significant part of the continuum observed in the energy spectra. In particular, a resonance of the residual nucleus dominates the region near the two-neutron emission threshold.

Gravity changes in geodynamically active areas are usually monitored by using discrete measurements. The temporal resolution, which is only as good as the repeat rate of the observations (usually ranging between one month and one year), is the main drawback of such measurements. To achieve a better temporal resolution and thus improve the possibilities of the investigation task, continuous gravity measurements have to be performed. However, temperature and pressure fluctuations seriously affect the output of continuously running spring gravity meters. In this paper, a methodology allowing the signal from a recording gravity meter to be compensated for the effect of temperature and pressure is discussed. To model how the meter output depends on the interfering signals, both polynomial (LMS) and nonlinear (neuro-fuzzy) forms of three different model structures have been tested. The results obtained through the nonlinear algorithm are satisfactory and could constitute the background for the implementation of a real-time correction system using a fuzzy micro-controller chip.

Recently, a rainbow pattern in the elastic scattering of 16O + 27Al at Elab. = 100 MeV was reported. In the present paper, we show that the predicted change of slope of the cross section, as a function of angle, is mostly due to the far-side component of the scattering, which is affected by the inelastic couplings. The experimental data is consistent with the calculations up to the inflection point, where the effect of the couplings is significant. New experimental data, in very good agreement with the theoretical expectations around the Coulomb rainbow angle, are also presented.

A study of the 14C and 15C states was pursued at the Catania INFN-LNS laboratory by the 12C(18O,16O)14C and 13C(18O,16O)15C reactions at 84 MeV incident energy. The 16O ejectiles were detected at forward angles by the MAGNEX magnetic spectrometer. Exploiting the large momentum acceptance (20%) and solid angle (50 msr) of the spectrometer, energy spectra were obtained with a relevant yield up to 20 MeV excitation energy. The application of the powerful trajectory reconstruction technique did allow to get energy spectra and angular distributions with resolution of about 160 keV and 0.3°. In the energy spectra several known low lying states of 14C and 15C have been observed and some unknown resonant structures at about 10.5 and 13.6 MeV in 15C and 16 MeV in 14C appear.

The possibility to use a mini-phoswich detector to identify ions in the region of Z ∼ 10 is explored in the framework of the NUMEN project. The NUMEN program, aimed at the investigation of the nuclear matrix elements connected to the neutrinoless double beta decay by means of double charge exchange nuclear reactions, foresees very high fluencies, which prevent the use of standard silicon as stop detectors. The need of reasonable radiation hardness, together with a total energy resolution around 2% and a high granularity, makes scintillators possible candidates. Promising results are obtained using an array of plastic + inorganic phoswich scintillators readout by means of Silicon Photo Multipliers.

High precision elastic and inelastic angular distributions have been measured for the 16 O + 27 Al system at a beam energy of 100 MeV. The data analysis confirms a rainbow formation as already predicted by parameter-free Coupled Channel calculations. It also helps to reveal the crucial role of inelastic couplings in the rainbow formation for heavier systems even at energies far above the Coulomb barrier. This feature, well known in atomic/molecular scattering, is experimentally studied for the first time in Nuclear Physics.

Quasi-elastic scattering data were obtained for the radioactive nucleus 8Li on a 90Zr target at the near-barrier energy of 18.5MeV over the angular range $ \theta_{lab}=15^{\circ}$ to 80°. They were analyzed within the coupled channels and coupled reaction channels frameworks pointing to a strong coupling effect for single neutron stripping, in contrast to 6, 7 Li + 90 Zr elastic scattering at similar energies, a non-trivial result linked to detailed differences in the structure of these Li isotopes.

We present results of repeated absolute gravity and GPS measurements, carried out at Mt. Etna volcano between 2009 and 2018. Absolute gravity measurements are rarely performed along arrays of stations on active volcanoes and, through our unprecedented dataset, we highlight the possibilities of this method to track underground mass changes over long time-scales. Analysis of the residual absolute gravity data and ground deformation reveals a cycle of gravity increase and uplift during 2009 to 2011, followed by gravity decrease and subsidence during 2011 to 2014. Data inversion points to a common mass and pressure source, lying beneath the summit area of the volcano, at depth of ~ 5 km b.s.l. The bulk volume change inferred by the inversion of the deformation data can account for only a small portion of the mass change needed to explain the correspondent gravity variations. We propose that the observed relationship between gravity and vertical deformation was mostly due to the compressibility of the magma in the inferred reservoir, which, in turn, was enhanced by the presence of exsolved gas. Overall, the gravity and deformation data we present reveal a cycle of magma recharge (2009–2011) and discharge (2011–2014) to/from the inferred storage zone. During the recharge phase only degassing occurred from the summit craters of Mt. Etna. During the following phase of discharge, the magma lost from the reservoir at ~ 5 km b.s.l. fed the exceptional phase of volcanic activity during 2011–2014, when tens of lava fountaining episodes took place.

This work analyzes temporal variations of seismic velocities at Mt. Etna from August 2018 to February 2019. During this time period, a strong flank eruption accompanied by intense seismicity and ground deformation took place along a fracture that opened on 24 December 2018 at the base of the New South-East summit crater. Furthermore, two moderate earthquakes—the 6 October 2018 ML 4.7 and 26 December 2018 ML 4.8—associated with the volcanic activity were recorded. In this study, we computed cross-correlation functions (CCFs) between windows of seismic ambient noise to identify seismic velocity variations within the volcano edifice. We calculated daily CCFs at 16 stations for 120 interstation pairs using the vertical component in the 1.0–1.5 Hz frequency band. We observe that dv/v starts to decrease rapidly from the beginning of October 2018 and reaches approximately −0.45% in the pre-eruption period. The spatio-temporal distribution of seismic velocities shows that the reduction of dv/v mostly occurs in the vicinity of the summit and close to the flank area and is interpreted to be affected by magmatic intrusion at 0–3 km depth. To infer the source mechanism of this eruption, we compared these observations with volcano-tectonic earthquakes, volcanic tremor, volcanic degassing, gravity, and ground deformation data. Our study suggests that a relationship between magma intrusion and associated crack opening is responsible for the decrease of dv/v.

The knowledge of the nuclear matrix elements (NME) entering in the expression of the half-life of the neutrinoless double beta decay is fundamental for neutrino physics. Information on the nuclear matrix elements can be obtained by measuring the absolute cross section of double charge exchange nuclear reactions. The two processes present some similarities, the initial and final-state wave functions are the same and the transition operators are similar. The experimental measurements of double charge exchange reactions induced by heavy ions present a number of challenging aspects, since such reactions are characterized by very low cross sections. Such difficulties are discussed for the measurement of the 116Cd(20Ne,20O)116Sn reaction at 15 AMeV.

Neutrinoless double beta decay of nuclei, if observed, would have important implications on fundamental physics. In particular it would give access to the effective neutrino mass. In order to extract such information from 0νββ decay half-life measurements, the knowledge of the Nuclear Matrix Elements (NME) is of utmost importance. In this context the NUMEN and the NURE projects aim to extract information on the NME by measuring cross sections of Double Charge Exchange reactions in selected systems which are expected to spontaneously decay via 0νββ. In this work an overview of the experimental challenges that NUMEN is facing in order to perform the experiments with accelerated beams and the research and development activity for the planned upgrade of the INFN-LNS facilities is reported.

This is deliverable 2.5 – MEMS device prototype – of the H2020 FET-Open project NEWTON-g (GA No 801221). The work described here was carried out in the framework of WP2(Development of the gravity imager).D2.5 presents the status of the MEMS gravimeter developed in the framework of NEWTON-g.

This is deliverable 2.4 – Quantum device prototype – of the H2020 FET-Open project NEWTON-g (GA No 801221). The work described here was carried out in the framework of WP2(Development of the gravity imager).D2.4 presents the characteristicsof the field version of the quantum gravimeter (AQG-B) developed in the framework of NEWTON-g.

The gravity imager, which will be developed under NEWTON-g and field-tested at Mt. Etna volcano, is composed by an array of microelectromechanical system (MEMS) pixels and an absolute quantum gravimeter (AQG). The main aim of the present document is to define the final configuration of the gravity imager, taking into account the environmental constraints and the gravimetric signature of volcanic processes highlighted in Deliverable 4.1, especially in terms of magnitude, timescale, detection zone and probability of occurrence of these processes.