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Background:The origin of fluorine is a widely debated issue. Nevertheless, the 15 N(α, γ) 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.Method: Measurement through the direct detection of the 19 F recoil ions with the European Recoil separator for Nuclear Astrophysics (ERNA) were performed. The reaction was initiated by a 15 N beam impinging onto a 4 He windowless gas target. The observed yield of the resonances at E c.m. = 1323 and 1487 keV is used to determine their widths in the α and γ channels. Results:We show that a direct measurement of the cross section of the 15 N(α, γ) 19 F reaction can be successfully obtained with the Recoil Separator ERNA, and the widths Γ γ and Γ α 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 Γ α . Conclusions:The revision of the widths of the two more relevant broad resonances in the 15 N(α, γ) 19 F 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.

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Carbon fusion reactions $$^{12}$$ 12 C($$^{12}$$ 12 C,p)$$^{23}$$ 23 Na and $$^{12}$$ 12 C($$^{12}$$ 12 C,$$\alpha $$ α )$$^{20}$$ 20 Ne play a key role in the evolution of massive stars and in explosive scenarios such as type-Ia supernovae and super-bursts in binary stars. A direct determination of their cross sections is extremely challenging and discrepancies exist between different data sets in the literature. Here we report the results of a direct measurement performed at the CIRCE Tandem Accelerator Laboratory in Caserta (Italy), using $$\varDelta E-E$$ Δ E - E detectors for unambiguous charge identification. Cross sections were measured in the energy range $$E_{\mathrm{c.m.}} =2.51{-}4.36$$ E c . m . = 2.51 - 4.36  MeV with energy steps between 10 and 25 keV in the centre of mass. To our knowledge these represent the finest energy steps to date. Results are presented in the form of partial and summed astrophysical $${\tilde{S}}$$ S ~ -factors for individual proton- and $$\alpha $$ α -particle channels. Branching ratios of individual proton- and $$\alpha $$ α -particle groups were found to vary significantly with energy. Angular distributions, albeit limited to three angles, were also found to be non-isotropic, which could be a potential explanation for the discrepancies observed among different data sets. Further efforts are ongoing to extend measurements to lower energies.

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Particle identification techniques are fundamental tools in nuclear physics experiments. Discriminating particles or nuclei produced in nuclear interactions allows to better understand the underlying physics mechanisms. The energy interval of these reactions is very broad, from sub-eV up to TeV. For this reason, many different identification approaches have been developed, often combining two or more observables. This paper reviews several of these techniques with emphasis on the expertise gained within the current nuclear physics scientific program of the Italian Istituto Nazionale di Fisica Nucleare (INFN).

Abstract. The12 C( 12 C, p) 23 Na and 12 C( 12 C, α) 20 Ne fusion reactions are among the most important in stellar evolution since they determine the destiny of massive (M 8-10 M ) stars. However, experimental low-energy investigations of such reactions are significantly hampered by ubiquitous natural hydrogen and deuterium contaminants in the carbon targets. The associated beam-induced background completely masks the reaction products of interest thus preventing cross-section measurements at the relevant energies of astrophysical interest, E cm < 2 MeV. In this work, we report about an investigation aimed at assessing possible deuterium reductions on both natural graphite and Highly Ordered Pyrolytic Graphite targets as a function of target temperature. Our results indicate that reductions up to about 80% can be attained on both targets in the temperature range investigated, T 200-1200 • C. A further reduction by a factor of 2.5 in absolute deuterium content is observed when the scattering chamber is surrounded by a dry nitrogen atmosphere so as to minimise light-particles uptake within the chamber rest gas (and thus on target) through air leaks. The results from this study will inform the choice of optimal experimental conditions and procedures for improved measurements of the 12 C + 12 C reactions cross-sections at the low energies of astrophysical interest.