Topological charge-sharing background reduction for the Silicon Drift Detectors used by the VIP experiment at LNGS.

Large area Silicon Drift Detectors are employed in high sensitivity tests of the Pauli Exclusion Principle by the VIP-2 Collaboration. The experiment is operated in the extremely low cosmic background environment of the Gran Sasso underground National Laboratory of INFN. In this work an off-line analysis method is proposed which provides an additional background reduction, as well as a better calibration procedure. The study concerns in particular the charge sharing between nearby cells, and is applied to the data set collected during the 2018 VIP-2 campaign. The cross-talk effect inside the detectors array is described and an effective topological method to reject the background induced by charge sharing is outlined.

A Novel Approach to Parameter Determination of the Continuous Spontaneous Localization Collapse Model.

Models of dynamical wave function collapse consistently describe the breakdown of the quantum superposition with the growing mass of the system by introducing non-linear and stochastic modifications to the standard Schrödinger dynamics. Among them, Continuous Spontaneous Localization (CSL) was extensively investigated both theoretically and experimentally. Measurable consequences of the collapse phenomenon depend on different combinations of the phenomenological parameters of the model-the strength λ and the correlation length rC-and have led, so far, to the exclusion of regions of the admissible (λ-rC) parameters space. We developed a novel approach to disentangle the λ and rC probability density functions, which discloses a more profound statistical insight.

Monte Carlo simulation of background components in low level Germanium spectrometry.

This proceeding presents the decomposition of the background spectra of the four screening detectors GeMPI 1 - 4 at the Gran Sasso Underground Laboratory (LNGS) using Monte Carlo simulations in the Geant4-based framework MaGe. A detailed understanding of the composition of the background spectra was achieved, allowing for the proposal of two new shield designs for future GeMPI-like detectors and enabling a reduction of the integrated background count rate to 15 counts/d/kg in the interval [40, 2700] keV.

Low-background gamma spectrometry and neutron diffraction in the study of stony meteorites.

Non-destructive characterisation of meteorites is here performed on a stony meteorite. The identification of the sample is performed by low-background γ-ray spectrometry in order to determine the presence of certain cosmogenic radionuclides, whereas a mineralogical phase quantitative analysis is carried out by Time-of-Flight Neutron Diffraction (ToF-ND) on the sample as-it-is. The protocol is then validated by applying micro-Raman Spectroscopy (µRS) and Energy Dispersive X-ray Spectroscopy (EDS). This paper is focused on γ-ray spectrometry, proving the meteoric origin of the sample, and it also presents some preliminary results of ToF-ND.

Cosmogenic radionuclides in the Cavezzo meteorite: Gamma-ray measurement and detection efficiency simulations.

The Cavezzo meteorite was recovered on January 4th, 2020, just three days after the fall observed over Northern Italy by the all-sky cameras of the Italian PRISMA fireball network. Two specimens, weighing 3.1 g (F1) and 52.2 g (F2), were collected in the predicted strewn-field and the meteorite has been classified as an L5 anomalous chondrite. The gamma-activity of the F2 sample was measured at the Monte dei Cappuccini underground Research Station (Torino, Italy) with a large-volume HPGe-NaI(Tl) spectrometer. Thanks to the high efficiency, selectivity, and low background of the spectrometer, we were able to detect fifteen cosmogenic radioisotopes. The presence of nuclides with half-lives down to a few days (47Ca, 52Mn, and 48V) undoubtedly confirmed the recent fall of the sample. The very low activity of 44Ti and 60Co was revealed with a particular coincidence between the HPGe and NaI(Tl) detectors. To obtain the detection efficiency, we have simulated the response of the detector with the GEANT4 toolkit, once the spectrometer's dead layer thickness was estimated using standards of known activity. Moreover, the simulation of the Dhajala meteorite (H3/4 chondrite) measurement allowed us to verify that the self-absorption of the sample is correctly taken into account and validate our simulations. In this contribution, we focus on the coincidence optimization techniques and the detection efficiency computation.

Strongest Atomic Physics Bounds on Noncommutative Quantum Gravity Models.

Investigations of possible violations of the Pauli exclusion principle represent critical tests of the microscopic space-time structure and properties. Space-time noncommutativity provides a class of universality for several quantum gravity models. In this context the VIP-2 lead experiment sets the strongest bounds, searching for the Pauli exclusion principle violating atomic transitions in lead, excluding the θ-Poincaré noncommutative quantum gravity models far above the Planck scale for nonvanishing θ_{µν} electriclike components, and up to 6.9×10^{-2} Planck scales if θ_{0i}=0.

At the crossroad of the search for spontaneous radiation and the Orch OR consciousness theory.

In this paper we perform a critical analysis of the Orch OR consciousness theory at the crossroad with the newest experimental results coming from the search for spontaneous radiation predicted by the simplest version of gravity-related dynamical collapse models. We conclude that Orch OR theory, when based on the simplest version of gravity-related dynamical collapse, is highly implausible in all the cases analyzed. We discuss the implications of our findings, the limitations, and future plans toward the development of more realistic gravity-related collapse models.

The impact and recovery of asteroid 2018 LA.

The June 2, 2018, impact of asteroid 2018 LA over Botswana is only the second asteroid detected in space prior to impacting over land. Here, we report on the successful recovery of meteorites. Additional astrometric data refine the approach orbit and define the spin period and shape of the asteroid. Video observations of the fireball constrain the asteroid's position in its orbit and were used to triangulate the location of the fireball's main flare over the Central Kalahari Game Reserve. 23 meteorites were recovered. A consortium study of eight of these classifies Motopi Pan as a HED polymict breccia derived from howardite, cumulate and basaltic eucrite, and diogenite lithologies. Before impact, 2018 LA was a solid rock of ~156 cm diameter with high bulk density ~2.85 g/cm3, a relatively low albedo pv ~ 0.25, no significant opposition effect on the asteroid brightness, and an impact kinetic energy of ~0.2 kt. The orbit of 2018 LA is consistent with an origin at Vesta (or its Vestoids) and delivery into an Earth-impacting orbit via the v6 resonance. The impact that ejected 2018 LA in an orbit towards Earth occurred 22.8 ± 3.8 Ma ago. Zircons record a concordant U-Pb age of 4563 ± 11 Ma and a consistent 207Pb/206Pb age of 4563 ± 6 Ma. A much younger Pb-Pb phosphate resetting age of 4234 ± 41 Ma was found. From this impact chronology, we discuss what is the possible source crater of Motopi Pan and the age of Vesta's Veneneia impact basin.

VIP-2 -High-Sensitivity Tests on the Pauli Exclusion Principle for Electrons.

The VIP collaboration is performing high sensitivity tests of the Pauli Exclusion Principle for electrons in the extremely low cosmic background environment of the underground Gran Sasso National Laboratory INFN (Italy). In particular, the VIP-2 Open Systems experiment was conceived to put strong constraints on those Pauli Exclusion Principle violation models which respect the so-called Messiah-Greenberg superselection rule. The experimental technique consists of introducing a direct current in a copper conductor, and searching for the X-rays emission coming from a forbidden atomic transition from the L shell to the K shell of copper when the K shell is already occupied by two electrons. The analysis of the first three months of collected data (in 2018) is presented. The obtained result represents the best bound on the Pauli Exclusion Principle violation probability which fulfills the Messiah-Greenberg rule.

Characterization of vanadium of biological origin for possible applications in physics experiments.

For the first time, vanadium of biological origin, extracted from centrifugal fraction of vanadium-storing blood cells of the Ascidia sydneiensis samea species, was characterized as regards its isotopic composition and content of natural radioactive elements potassium (K), thorium (Th) and uranium (U). The natural abundance of vanadium isotopes has been confirmed with high accuracy, thus excluding a possible selectivity within bio-chemical reactions of vanadium concentration in blood cells from seawater. A large potassium concentration (up to 5500 × 10-6 g g-1) was found in the blood cell samples. The concentration of thorium was determined to be about 30 × 10-9 g g-1, while the uranium concentration was about 150 × 10-9 g g-1. Hence, a highly efficient two-stage purification approach with a total vanadium recovery of better than 70% was developed and applied. The final concentrations of K < 100 × 10-6 g g-1 and of U/Th < 0.5 × 10-9 g g-1 in the purified vanadium-containing samples were achieved. Vanadium extracted from centrifugal fraction of vanadium-storing blood cells after two-stage purification approach could be utilized in various applications, where a high chemical purity compound is required. However, to be used as a source of radiopure vanadium in ultra-low-background experiment aimed to search for 50V beta decay, it should be further purified by Electron Beam Melting against residual potassium.

On the Importance of Electron Diffusion in a Bulk-Matter Test of the Pauli Exclusion Principle.

The VIolation of Pauli (VIP) experiment (and its upgraded version, VIP-2) uses the Ramberg and Snow (RS) method (Phys. Lett. B 1990, 238, 438) to search for violations of the Pauli exclusion principle in the Gran Sasso underground laboratory. The RS method consists of feeding a copper conductor with a high direct current, so that the large number of newly-injected conduction electrons can interact with the copper atoms and possibly cascade electromagnetically to an already occupied atomic ground state if their wavefunction has the wrong symmetry with respect to the atomic electrons, emitting characteristic X-rays as they do so. In their original data analysis, RS considered a very simple path for each electron, which is sure to return a bound, albeit a very weak one, because it ignores the meandering random walks of the electrons as they move from the entrance to the exit of the copper sample. These complex walks bring the electrons close to many more atoms than in the RS calculation. Here, we consider the full description of these walks and show that this leads to a nontrivial and nonlinear X-ray emission rate. Finally, we obtain an improved bound, which sets much tighter constraints on the violation of the Pauli exclusion principle for electrons.

Coordinated underground measurements of gamma-ray emitting radionuclides for plasma physics research.

Forty-eight samples made of CaF2, LiF and YVO4 were placed inside the KSTAR Tokamak and irradiated by neutrons and charged particles from eight plasma pulses. The aim was to provide information for plasma diagnostics. Due to the short pulse durations, the activities induced in the samples were low and therefore measurements were performed in five low-background underground laboratories. Details of the underground measurements, together with data on the quality control amongst the radiometric laboratories, are presented.

Ground gamma-ray survey of the Solforata gas discharge area, Alban Hills-Italy: a comparison between field and laboratory measurements.

Measurements of environmental radioactivity by HPGe gamma-spectrometry were carried out with the aim of investigating the distribution of natural radionuclides in a volcanic area and to compare two different methodologies - an in situ gamma-survey of the area and high accuracy laboratory measurements of soil samples. Results demonstrate good performance of the in situ technique, also confirmed by a correlation analysis between the results obtained by the two methodologies. A volcanic gas discharge area was chosen as the test site for the presence of natural long-lived radionuclides such as (40)K and (238)U, (235)U and (232)Th, and their decay chain members. Clear evidence of (222)Rn degassing in the area was confirmed by (226)Ra values measured by the in situ technique. Higher (40)K values measured by the in situ technique may be attributed to the presence of vegetation in the study area.

Radar-enabled recovery of the Sutter's Mill meteorite, a carbonaceous chondrite regolith breccia.

Doppler weather radar imaging enabled the rapid recovery of the Sutter's Mill meteorite after a rare 4-kiloton of TNT-equivalent asteroid impact over the foothills of the Sierra Nevada in northern California. The recovered meteorites survived a record high-speed entry of 28.6 kilometers per second from an orbit close to that of Jupiter-family comets (Tisserand's parameter = 2.8 ± 0.3). Sutter's Mill is a regolith breccia composed of CM (Mighei)-type carbonaceous chondrite and highly reduced xenolithic materials. It exhibits considerable diversity of mineralogy, petrography, and isotope and organic chemistry, resulting from a complex formation history of the parent body surface. That diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to C-class asteroids are interpreted.

Measurements of (60)Co in massive steel samples exposed to the Hiroshima atomic bomb explosion.

To study discrepancies in retrospective Hiroshima dosimetry, the specific activity of (60)Co in 16 steel samples from Hiroshima was measured using gamma-ray spectrometry in underground laboratories. There is general agreement between these new activity measurements and the specific activities derived from previously calculated dose values on the one hand and former measurements of samples gathered at distances less than 1,000 m from the center of the explosion (< 1,000 m slant range) on the other. It was found that activities at long range (> 1,300 m slant range) were mainly cosmogenically induced. Furthermore, at long range, these results are in disagreement with older measurements whose specific activity values were 10 to 100 times higher than predicted by computer model calculations in DS86 and DS02. As a consequence, the previously reported discrepancy is not confirmed.

Uranium groundwater anomalies and L'Aquila earthquake, 6th April 2009 (Italy).

Monitoring of chemical and physical groundwater parameters has been carried out worldwide in seismogenic areas with the aim to test possible correlations between their spatial and temporal variations and strain processes. Uranium (U) groundwater anomalies were observed during the preparation phases of the recent L'Aquila earthquake of 6th April 2009 in the cataclastic rocks near the overthrust fault crossing the deep underground Gran Sasso National Laboratory. The results suggest that U may be used as a potential strain indicator of geodynamic processes occurring before the seismic swarm and the main earthquake shock. Moreover, this justifies the different radon patterns before and after the main shock: the radon releases during and after the earthquake are much than more during the preparatory period because the process does not include only the microfracturing induced by stress-strain activation, but also radon increases accompanying groundwater U anomalies.

Ultra-low background measurements of decayed aerosol filters.

Aerosol samples collected on filter media were analyzed using HPGe detectors employing varying background-reduction techniques in order to experimentally evaluate the opportunity to apply ultra-low background measurement methods to samples collected, for instance, by the Comprehensive Test Ban Treaty International Monitoring System (IMS). In this way, realistic estimates of the impact of low-background methodology on the sensitivity obtained in systems such as the IMS were assessed. The current detectability requirement of stations in the IMS is 30 µBq/m3 of air for 140Ba, which would imply ~106 fissions per daily sample. Importantly, this is for a fresh aerosol filter. One week of decay reduces the intrinsic background from radon daughters in the sample allowing much higher sensitivity measurement of relevant isotopes, including 131I. An experiment was conducted in which decayed filter samples were measured at a variety of underground locations using Ultra-Low Background (ULB) gamma spectroscopy technology. The impacts of the decay and ULB are discussed.

In-vessel activation monitors in JET: progress in modeling.

Activation studies were performed in JET with new in-vessel activation monitors. Though primarily dedicated to R&D in the challenging issue of lost diagnostics for ITER, which is being addressed at JET with several techniques, these monitors provide for both neutron and charged particle fluences. A set of samples with different orientation with respect to the magnetic field is transported inside the torus by means of a manipulator arm (in contrast with the conventional JET activation system with pneumatic transport system). In this case, radionuclides with longer half-life were selected and ultralow background gamma-ray measurements were needed. The irradiation was closer to the plasma and this potentially reduces the neutron scattering problem. This approach could also be of interest for ITER, where the calibration methods have yet to be developed. The MCNP neutron transport model for JET was modified to include the activation probe and so provide calculations to help assess the new data. The neutron induced activity on the samples are well reproduced by the calculations.