Background: The phenomenon of fusion hindrance may have important consequences on the nuclear processes occurring in astrophysical scenarios, if it is a general behaviour of heavy-ion fusion at extreme sub-barrier energies, including reactions involving lighter systems, e.g. reactions in the carbon and oxygen burning stages of heavy stars. The hindrance is generally identified by the observation of a maximum of the S factor vs. energy. Whether there is an S-factor maximum at very low energies for systems with a positive fusion Q-value is an experimentally challenging question.Purpose: Our aim has been to search for evidence of fusion hindrance in 12 C + 24 Mg which is a medium-light system with positive Q-value for fusion, besides the heavier cases where hindrance is recognised to be a general phenomenon. 12 C + 24 Mg is very close to the 16 O + 16 O and 12 C + 12 C systems that are important for the late evolution of heavy stars. Methods:The experiment has been performed in inverse kinematics using the 24 Mg beam from the XTU Tandem accelerator of LNL in the energy range 26-52 MeV with an intensity of 4-8 pnA. The targets were 12 C evaporations 50 µg/cm 2 thick, isotopically enriched to 99.9%. The fusion-evaporation residues were detected at small angles by a E-∆E-ToF detector telescope following an electrostatic beam deflector.Results: Previous measurements of fusion cross section for 12 C + 24 Mg were limited to above-barrier energies. In the present experiment the excitation function has been extended down to ≃15µb and it appears that the S factor develops a clear maximum vs. energy, indicating the presence of hindrance. This is the first convincing evidence of an S factor maximum in a medium-light system with a positive fusion Q-value. These results have been fitted following a recently suggested method, and a detailed analysis within the coupled-channels model that has been performed using a Woods-Saxon potential and including the ground state rotational band of 24 Mg. The CC calculations give a good account of the data near and above the barrier but overpredict the cross sections at very low energies. Conclusions:The hindrance phenomenon is clearly observed in 12 C + 24 Mg, and its energy threshold is in reasonable agreement with the systematics observed for several medium-light systems. The fusion cross sections at the hindrance threshold show that the highest value (σs=1.6mb) is indeed found for this system. Therefore it may even be possible to extend the measurements further down in energy to better establish the position of the S-factor maximum.

The Selective Production of Exotic Species project is under construction at Laboratori Nazionali di Legnaro-INFN. The aim of the collaboration is to produce highly pure Radioactive Ion Beams (RIBs) from fission fragments of a uranium carbide (UC x) target activated by a cyclotron proton beam. In order to select a specific atomic species, the main tool to be applied is the resonant laser ionization technique. We have just completed the installation of a dedicated all solid state laser system whose elements are tunable to transitions of all the elements/isotopes of interest for the project. The new laser system is based on three Titanium:sapphire laser sources, independently pumped by three Nd:YLF pump lasers, and it can be coupled to two high harmonic generation (second harmonic generation, third harmonic generation, and fourth harmonic generation) setups. The power, wavelength, and position of the laser beams are continuously monitored and stabilized by using automated active systems to improve the beam production stability of RIBs. This paper presents the main features of the laser system and examples of application of a laser ion source, including a first demonstration of photoionization of stable silver, one of the most requested elements for RIB application.

The study of the atomic spectrum via resonant laser excitation provides access to underlying effects caused by the nuclear structure, which is of special interest in short-lived radioisotopes produced at Isotope Separator On-Line (ISOL) facilities. Current implementations of resonant laser ionization techniques often limit the extraction of the nuclear observables due to the low spectral resolution of the pulsed laser systems deployed. Several high-resolution spectroscopy techniques demand spectral widths in the order of hundreds of MHz and below. A proven solution to reduce this linewidth is the pulsed amplification of a narrow-band continuous wave (cw) laser. This work presents the demonstration of a pulsed dye amplifier seeded by a commercially available cw Optical Parametric Oscillator (OPO). The performance of this system was compared with competing setups using a cw dye laser seed source as well as a frequency mixing technique using a combination of an injection-locked titanium:sapphire (Ti:Sa) and a Nd:YVO4 laser. Spectral bandwidths of the systems were measured using a high finesse Fabry-Perot Interferometer, resulting in comparable optical linewidths between 140 to 156 MHz at a wavelength of 328 nm for the different laser setups. Suitability for on-line experiments was validated by performing high-resolution spectroscopy of radioactive silver isotopes in the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at the Isotope Separator On-Line Device (ISOLDE), at the European Organization for Nuclear Research (CERN). The quality of the hyperfine spectra was similar for the dye and the OPO seed and the deduced hyperfine splitting was in good agreement with literature, while the frequency mixing technique exhibited less precise results attributed to the frequency instabilities and mode-hops of the single-mode Nd:YVO4 laser.

Radionuclides of interest in nuclear medicine are generally produced in cyclotrons or nuclear reactors, with associated issues such as highly enriched target costs and undesired contaminants. The ISOLPHARM project (ISOL technique for radioPHARMaceuticals) explores the feasibility of producing extremely high specific activity βemitting radionuclides as radiopharmaceutical precursors. This technique is expected to produce radiopharmaceuticals very hardly obtained in standard production facilities. Radioactive isotopes will be obtained from nuclear reactions induced by accelerating 40 MeV protons in a cyclotron to collide on a UCx target. By means of: high working temperatures and high vacuum conditions, the migration of the radioactive elements towards an ion source, a potential difference up to 40 kV, and a mass separation device, an isobaric beam of desired radionuclides will be produced and implanted on a deposition target. The availability of innovative isotopes can potentially open a new generation of radiopharmaceuticals, based on nuclides never studied so far. Among these, a very promising isotope could be Ag-111, a βemitter with a half-life (7.45 d), an average βenergy of 360 keV, a tissue penetration of around 1 mm, and a low percentage of γ-emission. The proof of principle studies on Ag-111 production and radiolabeling are currently under investigation in the ISOLPHARM_EIRA project, where both its production and possible application as a radiopharmaceutical precursor will be evaluated in its computational/physics, radiochemistry, and radiobiology tasks. Currently, innovative macromolecules meeting the specific requirements for the chelation and targeted delivery of Ag-111 are being developed, which will be further tested in vitro on 2D and 3D models, as well as in vivo for their pharmacokinetics and therapeutic potential onto xenograft models.