Measurement of 1323 and 1487 keV resonances in 15N({\alpha}, {\gamma})19F with the recoil separator ERNA

The origin of fluorine is a widely debated issue. Nevertheless, the ^{15}N({\alpha},{\gamma})^{19}F reaction is a common feature among the various production channels so far proposed. Its reaction rate at relevant temperatures is determined by a number of narrow resonances together with the DC component and the tails of the two broad resonances at E_{c.m.} = 1323 and 1487 keV. Measurement through the direct detection of the 19F recoil ions with the European Recoil separator for Nuclear Astrophysics (ERNA) were performed. The reaction was initiated by a 15N beam impinging onto a 4He windowless gas target. The observed yield of the resonances at Ec.m. = 1323 and 1487 keV is used to determine their widths in the {\alpha} and {\gamma} channels. We show that a direct measurement of the cross section of the ^{15}N({\alpha},{\gamma})^{19}F reaction can be successfully obtained with the Recoil Separator ERNA, and the widths {\Gamma}_{\gamma} and {\Gamma}_{\alpha} of the two broad resonances have been determined. While a fair agreement is found with earlier determination of the widths of the 1487 keV resonance, a significant difference is found for the 1323 keV resonance {\Gamma}_{\alpha} . The revision of the widths of the two more relevant broad resonances in the 15N({\alpha},{\gamma})19F reaction presented in this work is the first step toward a more firm determination of the reaction rate. At present, the residual uncertainty at the temperatures of the ^{19}F stellar nucleosynthesis is dominated by the uncertainties affecting the Direct Capture component and the 364 keV narrow resonance, both so far investigated only through indirect experiments.Comment: 8 pages, 11 figures. Accepted for publication in PR

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

RaMonA system for radon and thoron measurement

RaMonA is a homemade system for the measurements in air of the specific activity of 222Rn (radon) and 220Rn (thoron) based on the electrostatic collection of the alpha emissions of the ionized descendants of the two radioisotopes. The use of a semiconductor detector and of an appropriate signal processing apparatus allows to obtain alpha spectra with excellent energy resolution. The system has been used for many years for the continuous monitoring of the gas indoors, outdoors and in soil air. For several purposes, different geometries of the measurement chamber are realized and suitably calibrated, even in mixed atmospheres of 222Rn and 220Rn. In this paper, the different measurement systems and their potentialities are presented and the collection efficiencies of the different polonium isotopes are compared

Isotopic techniques for environmental monitoring and nuclear waste management at CIRCE

CIRCE (Center for Isotopic Research on Environmental and Cultural heritage) was founded in 2005 as a research center dedicated to the application of isotopic methodologies in environmental and cultural heritage research. Later the spectrum of activities expanded and CIRCE became part of the laboratory hub of the Department of Mathematics and Physics, University of Campania L. Vanvitelli (formerly Second University of Naples), Caserta, Italy. In this context, an environmental monitoring program of the areas surrounding the Garigliano nuclear power plant (NPP) and of the building materials of the NPP was developed. The activities were carried out by involving undergraduate and doctoral students and taking care of communication with local administrations. In this framework, a survey among high school students was conducted to provide an insight into the public’s perception of risk connected to NPP. Alongside environmental radioactivity monitoring and material characterization techniques available at CIRCE are discussed. The activities presented here could find interesting applications in the framework of the Italian National Repository for Radioactive Waste and the annexed Technopark

Energy calibration and stability of the 3 MV accelerator at CIRCE for applications in Nuclear Astrophysics

A 3 MV NEC 9SDH-2 Pelletron accelerator is installed at the Center for Isotopic Research on Cultural and Environmental Heritage of Dipartimento di Matematica e Fisica, Università degli Studi della Campania “Luigi Vanvitelli”, Caserta (CIRCE-DMF). The accelerator serves several beam lines devoted to both applied and fundamental research. While generally a precise and accurate knowledge of the energy of the charged particle beams is of interest for all applications, the measurement of charged particle nuclear reactions of astrophysical energies is particularly demanding because of the strong energy dependence of the cross section below the Coulomb barrier and the very long duration of the measurements. We describe here the energy calibration of the accelerator installed at CIRCE-DMF and a measurement of the short term stability. A routine to improve the long term stability and remove the observed dependence of the terminal voltage on the injected current was successfully tested. Finally, possible improvements are 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]