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The GALILEO array is a high-efficiency γ -ray spectrometer, resident at the Legnaro National Laboratory (LNL)in Italy, and it is currently used in combination with the Si-ball EUCLIDES for the detection of charged-particles. The combined setup was used in the 6 Li+89Y experiment with incident energies of 22 MeV and 34 MeV to investigate the influence of breakup and transfer of weakly bound projectile on the fusion process. Using the coincidence by the charged particles and γ -rays, the different reaction channels can be clearly identified and the different reaction mechanisms can be clearly studied. It is shown that this facility can be used well to explore the fusion reaction mechanisms induced by weakly bound nuclei.

Accurate knowledge of thermonuclear reaction rates is important in understanding the generation of energy, the luminosity of neutrinos, and the synthesis of elements in stars. Cross-section measurements for quiescent stellar H-burning are mainly hampered by extremely low counting rate and cosmic background. The LUNA Collaboration has shown that, by going underground and by using the typical techniques of low background physics, it is possible to measure nuclear cross-sections down to the energy of the nucleosynthesis inside stars. This paper reports an overview of the experimental techniques adopted in underground nuclear astrophysics through a summary of the main recent results and achievements. The future developments of the LUNA experiment are also given. © 2013 Elsevier B.V. All rights reserved.

A large set of data on long term performance of n-type HPGe detectors used in GASP, EUROBALL and CLARA γ spectrometers, as well as environmental measurements have been collected over two decades. In this paper a detailed statistical analysis of this data is given and detector long term behaviour is provided to the scientific community. We include failure, failure mode, repair frequency, repair outcome and its influence in the energy efficiency and energy resolution. A remarkable result is that the life span distribution is exponential. A detector's failure is a memory-less process, where a previous failure does not influence the upcoming one. Repaired spectrometers result in high reliability with deep implications in the management of large scale high-resolution gamma spectrometry related projects. Findings show that on average, detectors initial counting efficiency is slightly lower (∼2%) than that reported by the manufacturers and the repair process (including annealing) does not affect significantly the energy efficiency, even after a long period of use. Repaired detector energy resolution statistics show that the probability, that a repaired detector will be at least as good as it was originally, is more than 3/4.

The He 3 ( α , γ ) Be 7 process is a key reaction in both Big-Bang nucleosynthesis and p–p chain of Hydrogen Burning in Stars. A new measurement of the He 3 ( α , γ ) Be 7 cross section has been performed at the INFN Gran Sasso underground laboratory by both the activation and the prompt γ detection methods. The present work reports full details of the prompt γ detection experiment, focusing on the determination of the systematic uncertainty. The final data, including activation measurements at LUNA, are compared with the results of the last generation experiments and two different theoretical models are used to obtain the S-factor at solar energies.

High-spin states in the neutron-deficient nuclide I-111 have been populated with the fusion reaction Ni-58 + Ni-58 at a beam energy of 210 MeV, in an experiment performed at the Tandem Accelerator of the Laboratori Nazionali di Legnaro. The gamma spectrometer GASP was used in time coincidence with the ISIS Si-ball and the CAMEL recoil mass spectrometer for the positive identification of the nuclide. Gamma transitions and structure details previously attributed to I-111 by Other authors are only partially confirmed. The obtained level scheme includes new rotational bands and a new low lying structure which suggests the presence of octupole correlations at predicted rotational frequency values.

The study of superdeformation in nuclei around the nucleus 144Gd, which can be considered as doubly-closed at superdeformed shape, provided detailed knowledge about the structure of superdeformed bands in this region. The chain of Gd isotopes showing superdeformation could be extended to 143Gd. Since highly-deformed bands are known in 139,141Gd, it appears that the transition between the regions of superdeformed nuclei with A ≈ 150 and of highly-deformed nuclei with A ≈ 130 is rather sharp and takes place around N = 78 as theoretically predicted. In 144Gd four excited superdeformed bands have been found in addition to the yrast superdeformed band. They form two pairs of signature partner bands of π6 1 π[404]9 2ν7 0 and π6 1 π[411]3 2ν7 0 configurations. In 145Gd for the first time two crossings have been observed in a superdeformed band, which are assigned to the alignment of an i 13 2 proton pair and a subsequent crossing of the i 13 2 [642]5 2 and i 11 2 [651]1 2 neutron orbitals, respectively.

Very proton rich nuclei in the A≈100 region have been investigated using the GASP array coupled with the Recoil Mass Spectrometer (RMS) and the GASP Si-ball. High-spin states of 105Sn and 103In nuclei formed with the reaction 58 Ni + 50 Cr at 210 MeV have been investigated up to ≈ 10 and 7 MeV of excitation energy respectively. We have confirmed the known excited states for both nuclei and extended to higher spin the level scheme. The experimental level schemes are compared with shell model calculations.

Quasi-elastic transfer cross sections have been measured for the systems 32,36 S+ 58,64 Ni at three energies around the Coulomb barrier. Q -value distributions have been extracted for each of the neutron and charged particle transfer channels. The influence of the transfer channels on the sub-barrier fusion cross section is discussed, and the importance of the proton stripping in 32 S + 64 Ni is pointed out.