A detailed knowledge of the decay properties of the so called Hoyle state in the $$^{12}$$ C nucleus ( $$E_x=7.654$$ MeV, $$0^+$$ ) is required to calculate the rate at which carbon is forged in typical red-giant stars. This paper reports on a new almost background-free measurement of the radiative decay branching ratio of the Hoyle state using advanced charged particle coincidence techniques. The exploitation, for the first time in a similar experiment, of a bidimensional map of the coincidence efficiency allows to reach an unitary value and, consequently, to strongly reduce sources of systematic uncertainties. The present results suggest a value of the radiative branching ratio of $$\Gamma _{rad}/\Gamma _{tot}=4.4(6)\cdot 10^{-4}$$ . This finding helps to resolve the tension between recent data published in the literature.

The Advanced GAmma Tracking Array (AGATA) has been installed at Laboratori Nazionali di Legnaro (LNL), Italy. In this installation, AGATA will consist, at the beginning, of 13 AGATA triple clusters (ATCs) with an angular coverage of 1π, and progressively the number of ATCs will increase up to a 2π angular coverage. This setup will exploit both stable and radioactive ion beams delivered by the Tandem–PIAVE-ALPI accelerator complex and the SPES facility. The new implementation of AGATA at LNL will be used in two different configurations, firstly one coupled to the PRISMA large-acceptance magnetic spectrometer and lately a second one at Zero Degrees, along the beam line. These two configurations will allow us to cover a broad physics program, using different reaction mechanisms, such as Coulomb excitation, fusion-evaporation, transfer and fission at energies close to the Coulomb barrier. These setups have been designed to be coupled with a large variety of complementary detectors such as charged particle detectors, neutron detectors, heavy-ion detectors, high-energy γ-ray arrays, cryogenic and gasjet targets and the plunger device for lifetime measurements. We present in this paper the conceptual design, characteristics and performance figures of this implementation of AGATA at LNL.

Background: The existence of fusion hindrance in the light heavy-ion systems of astrophysical interest is not well established, so investigating slightly heavier cases may allow a reliable extrapolation towards the lighter ones. The recent observation of a very high hindrance threshold in C-12+ Mg-24 (with a positive Q value for fusion) at sigma(fus) similar or equal to 0.75 mb, misses a valid interpretation within current theoretical models. Purpose: Our aim has been to search evidence for fusion hindrances in the nearby system C-12+ Mg-26 also having Q(fus) greater than or similar to 0, and to obtain information on the underlying physics from a comparison of the two cases and from coupled-channels calculations. Methods: The experiment was performed in inverse kinematics using the Mg-26 beam from the XTU Tandem accelerator of Laboratori Nazionali di Legnaro (LNL). The targets were thin C-12 evaporations isotopically enriched to 99.9%. The fusion-evaporation residues were detected at small angles by a E-Delta E-ToF detector telescope following an electrostatic beam deflector. Results: The fusion excitation function of C-12+ Mg-26 has been measured down to approximate to 5 mu b. The astrophysical S factor shows a maximum at an energy where the cross section is approximate to 0.03 mb, significantly lower than for C-12+ Mg-24. This difference is confirmed by the comparison of the two S factors. coupled channel calculations give a good account of the data, but they overpredict the cross sections below approximate to 0.03 mb. The logarithmic slopes of the two excitation functions are superimposable to a large extent, with visible oscillations, more noticeable for C-12+ Mg-24. Conclusions: The hindrance phenomenon is clearly observed in C-12+ Mg-26. The difference between the corresponding threshold energies for C-12+ Mg-24,Mg-26 might (only qualitatively) be attributed to the alpha-like structure of Mg-24. In the Jiang's phenomenological systematics, the different behaviors of C-12+ (24,2)6Mg make the situation more complex, and call into question the extrapolation procedure toward the lighter systems of astrophysical interest.

We measured multinucleon transfer reactions for the 206Pb + 118Sn system at Elab = 1200 MeV by employing the large solid angle magnetic spectrometer PRISMA. Differential and total cross sections and Q-value distri-butions have been obtained for a variety of neutron and proton pick-up and stripping channels. The Q-value distributions show how the quasielastic and deep inelastic processes depend on the mass and charge of the transfer products. The corresponding cross sections have been compared with calculations performed with the GRAZING code. An overall good agreement is found for most of the few nucleon transfer channels. The underestimation of the data for channels involving a large number of transferred nucleons indicates that more complicated processes populate the given isotopes.

Background: The existence of fusion hindrance in the light heavy-ion systems of astrophysical interest is not well established, so investigating slightly heavier cases may allow a reliable extrapolation towards the lighter ones. The recent observation of a very high hindrance threshold in $^{12}\mathrm{C}+^{24}\mathrm{Mg}$ (with a positive $Q$ value for fusion) at ${\ensuremath{\sigma}}_{\mathrm{fus}}\ensuremath{\simeq}0.75$ mb, misses a valid interpretation within current theoretical models.Purpose: Our aim has been to search evidence for fusion hindrances in the nearby system $^{12}\mathrm{C}+^{26}\mathrm{Mg}$ also having ${Q}_{\mathrm{fus}}>0$, and to obtain information on the underlying physics from a comparison of the two cases and from coupled-channels calculations.Methods: The experiment was performed in inverse kinematics using the $^{26}\mathrm{Mg}$ beam from the XTU Tandem accelerator of Laboratori Nazionali di Legnaro (LNL). The targets were thin $^{12}\mathrm{C}$ evaporations isotopically enriched to $99.9%$. The fusion-evaporation residues were detected at small angles by a $E\ensuremath{-}\mathrm{\ensuremath{\Delta}}E$-ToF detector telescope following an electrostatic beam deflector.Results: The fusion excitation function of $^{12}\mathrm{C}+^{26}\mathrm{Mg}$ has been measured down to $\ensuremath{\approx}5\phantom{\rule{0.16em}{0ex}}\textmu{}\mathrm{b}$. The astrophysical $S$ factor shows a maximum at an energy where the cross section is $\ensuremath{\approx}0.03$ mb, significantly lower than for $^{12}\mathrm{C}+^{24}\mathrm{Mg}$. This difference is confirmed by the comparison of the two $S$ factors. coupled channel calculations give a good account of the data, but they overpredict the cross sections below $\ensuremath{\approx}0.03$ mb. The logarithmic slopes of the two excitation functions are superimposable to a large extent, with visible oscillations, more noticeable for $^{12}\mathrm{C}+^{24}\mathrm{Mg}$.Conclusions: The hindrance phenomenon is clearly observed in $^{12}\mathrm{C}+^{26}\mathrm{Mg}$. The difference between the corresponding threshold energies for $^{12}\mathrm{C}+^{24,26}\mathrm{Mg}$ might (only qualitatively) be attributed to the $\ensuremath{\alpha}$-like structure of $^{24}\mathrm{Mg}$. In the Jiang's phenomenological systematics, the different behaviors of $^{12}\mathrm{C}+^{24,26}\mathrm{Mg}$ make the situation more complex, and call into question the extrapolation procedure toward the lighter systems of astrophysical interest.

We measured multinucleon transfer reactions for the $^{206}\mathrm{Pb}+^{118}\mathrm{Sn}$ system at ${E}_{\mathrm{lab}}=1200$ MeV by employing the large solid angle magnetic spectrometer PRISMA. Differential and total cross sections and $Q$-value distributions have been obtained for a variety of neutron and proton pick-up and stripping channels. The $Q$-value distributions show how the quasielastic and deep inelastic processes depend on the mass and charge of the transfer products. The corresponding cross sections have been compared with calculations performed with the grazing code. An overall good agreement is found for most of the few nucleon transfer channels. The underestimation of the data for channels involving a large number of transferred nucleons indicates that more complicated processes populate the given isotopes.