Recent Achievements of the ERNA Collaboration

For more than two decades, the ERNA collaboration has investigated nuclear processes of astrophysical interest through the direct measurement of cross sections or the identification of the nucleosynthesis effects. Measurements of cross-section, reported in this publication, of radiative capture reactions have been mainly conducted using the ERNA Recoil Mass Separator, and more recently with an array of charged particle detector telescopes designed for nuclear astrophysics measurements. Some results achieved with ERNA will be reviewed, with a focus on the results most relevant for nucleosynthesis in AGB and advanced burning phases

A New Low-Energy Proton Irradiation Facility to Unveil the Mechanistic Basis of the Proton-Boron Capture Therapy Approach

Protontherapy (PT) is a fast-growing cancer therapy modality thanks to much-improved normal tissue sparing granted by the charged particles' inverted dose-depth profile. Protons, however, exhibit a low biological effectiveness at clinically relevant energies. To enhance PT efficacy and counteract cancer radioresistance, Proton–Boron Capture Therapy (PBCT) was recently proposed. PBCT exploits the highly DNA-damaging α-particles generated by the p + 11B→3α (pB) nuclear reaction, whose cross-section peaks for proton energies of 675 keV. Although a significant enhancement of proton biological effectiveness by PBCT has been demonstrated for high-energy proton beams, validation of the PBCT rationale using monochromatic proton beams having energy close to the reaction cross-section maximum is still lacking. To this end, we implemented a novel setup for radiobiology experiments at a 3-MV tandem accelerator; using a scattering chamber equipped with an Au foil scatterer for beam diffusion on the biological sample, uniformity in energy and fluence with uncertainties of 2% and 5%, respectively, was achieved. Human cancer cells were irradiated at this beamline for the first time with 685-keV protons. The measured enhancement in cancer cell killing due to the 11B carrier BSH was the highest among those thus far observed, thereby corroborating the mechanistic bases of PBCT

Charge state studies of low energy heavy ions passing through hydrogen and helium gas

Studies of the charge state distribution of low energy (< 1.5 MeV/u), low Z (< 13) heavy ions passing through hydrogen and helium gas of varying target pressure have been performed using separate windowless gas target systems at TRIUMF and the University of Naples. Semi-empirical relationships have been deduced to estimate the equilibrium charge state distributions as a function of beam energy. From these distributions, cross-sections for the relevant charge changing reactions have been deduced. (C) 2002 Elsevier Science B.V. All rights reserved

FLUORINE ABUNDANCES IN GALACTIC ASYMPTOTIC GIANT BRANCH STARS

An analysis of the fluorine abundance in Galactic asymptotic giant branch (AGB) carbon stars (24 N-type, 5 SC-type, and 5 J-type) is presented. This study uses the state-of-the-art carbon-rich atmosphere models and improved atomic and molecular line lists in the 2.3 μm region. Significantly lower F abundances are obtained in comparison to previous studies in the literature. This difference is mainly due to molecular blends. In the case of carbon stars of SC-type, differences in the model atmospheres are also relevant. The new F enhancements are now in agreement with the most recent theoretical nucleosynthesis models in low-mass AGB stars, solving the long-standing problem of F in Galactic AGB stars. Nevertheless, some SC-type carbon stars still show larger F abundances than predicted by stellar models. The possibility that these stars are of larger mass is briefly discussed

The Status and Future of Direct Nuclear Reaction Measurements for Stellar Burning

The study of stellar burning began just over 100 years ago. Nonetheless, we do not yet have a detailed picture of the nucleosynthesis within stars and how nucleosynthesis impacts stellar structure and the remnants of stellar evolution. Achieving this understanding will require precise direct measurements of the nuclear reactions involved. This report summarizes the status of direct measurements for stellar burning, focusing on developments of the last couple of decades, and offering a prospectus of near-future developments.Comment: Accepted to Journal of Physics G as a Major Report. Corresponding author: Zach Meisel ([email protected]

Event reconstruction for KM3NeT/ORCA using convolutional neural networks

The KM3NeT research infrastructure is currently under construction at two locations in the Mediterranean Sea. The KM3NeT/ORCA water-Cherenkov neutrino detector off the French coast will instrument several megatons of seawater with photosensors. Its main objective is the determination of the neutrino mass ordering. This work aims at demonstrating the general applicability of deep convolutional neural networks to neutrino telescopes, using simulated datasets for the KM3NeT/ORCA detector as an example. To this end, the networks are employed to achieve reconstruction and classification tasks that constitute an alternative to the analysis pipeline presented for KM3NeT/ORCA in the KM3NeT Letter of Intent. They are used to infer event reconstruction estimates for the energy, the direction, and the interaction point of incident neutrinos. The spatial distribution of Cherenkov light generated by charged particles induced in neutrino interactions is classified as shower- or track-like, and the main background processes associated with the detection of atmospheric neutrinos are recognized. Performance comparisons to machine-learning classification and maximum-likelihood reconstruction algorithms previously developed for KM3NeT/ORCA are provided. It is shown that this application of deep convolutional neural networks to simulated datasets for a large-volume neutrino telescope yields competitive reconstruction results and performance improvements with respect to classical approaches

Event reconstruction for KM3NeT/ORCA using convolutional neural networks

The KM3NeT research infrastructure is currently under construction at two locations in the Mediterranean Sea. The KM3NeT/ORCA water-Cherenkov neutrino de tector off the French coast will instrument several megatons of seawater with photosensors. Its main objective is the determination of the neutrino mass ordering. This work aims at demonstrating the general applicability of deep convolutional neural networks to neutrino telescopes, using simulated datasets for the KM3NeT/ORCA detector as an example. To this end, the networks are employed to achieve reconstruction and classification tasks that constitute an alternative to the analysis pipeline presented for KM3NeT/ORCA in the KM3NeT Letter of Intent. They are used to infer event reconstruction estimates for the energy, the direction, and the interaction point of incident neutrinos. The spatial distribution of Cherenkov light generated by charged particles induced in neutrino interactions is classified as shower-or track-like, and the main background processes associated with the detection of atmospheric neutrinos are recognized. Performance comparisons to machine-learning classification and maximum-likelihood reconstruction algorithms previously developed for KM3NeT/ORCA are provided. It is shown that this application of deep convolutional neural networks to simulated datasets for a large-volume neutrino telescope yields competitive reconstruction results and performance improvements with respect to classical approaches

A new measurement of the E1 amplitude in 12C(α,γ)16O^{12}C(\alpha,\gamma)^{16}O

Die Reaktion $^{12}C(\alpha,\gamma)^{16}O$ bestimmt zusammen mit der $3\alpha^{12}C$ Reaktion das $^{12}C/^{16}O$ Häufigkeitsverhältnis am Ende des Helium Brennens in Sternen. Dieses Verhältnis hat einen starken Einfluß auf die folgende Sternentwicklung und Elementsynthese. Daher ist die Kenntnis des $^{12}C(\alpha,\gamma)^{16}O$ astrophysikalischen S-Faktors $S(E_{0})$ bei der relevanten Energie, $E_{0}=300$ keV, mit einer Genauigkeit von 10% erforderlich. Die E1 Amplitude dieser Reaktion wurde im Energiebereich E=1.3 bis 3.0 MeV gemessen. Ein intensiver $^{12}C$ Strahl wurde auf ein $^{4}He$ Gastarget geschossen und die $\gamma$ Strahlung durch sechs 70% HPGe Detektoren nachgewiesen. Die Zähler waren senkrecht zur Strahlrichtung in einer ringförmigen Geometrie um das Target mit einem Abstand von 17 cm montiert. Die Ergebnisse dieser Messung wurden durch eine auf R-Matrix Rechnungen basierende Monte Carlo-Methode zu $E_{0}$ extrapoliert. Mit der Annahme von konstruktiver Interferenz, erhält man einen Wert von $S_{E1}(E_{0})$=90$\pm$16 keV b.The $^{12}C(\alpha,\gamma)^{16}O$ reaction, together with the $3\alpha^{12}C$ capture, determines the $^{12}C/^{16}O$ abundance ratio at the end of helium burning in stars. This ratio has a strong influence on the subsequent stellar evolution and nucleosynthesis. A knowledge of the astrophysical S-factor of $^{12}C(\alpha,\gamma)^{16}O$ at the relevant energy $E_{0}=300$ with a precision of 10% is required. The E1 amplitude of the ground state transition in $^{12}C(\alpha,\gamma)^{16}O$ was measured in the energy range E=1.3 to 3.0 MeV using an intense $^{12}C$ beam in combination with a $^{4}He$ gas target and an array of six 70% HPGe detectors. The detectors were placed in a ring shaped geometry around the target at a distance of 17 cm on a plane perpendicular to the beam axis. The results of this measurement were extrapolated to $E_{0}$ by means of a novel R-matrix fit based Monte Carlo procedure. With the assumption of constructive interference, one obtains a value $S_{E1}(E_{0})$=90$\pm$16 keV b