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The neutrons for science (NFS) facility is a component of SPIRAL-2, the new superconducting linear accelerator built at GANIL in Caen (France). The proton and deuteron beams delivered by the accelerator will allow producing intense neutron fields in the 100 keV-40 MeV energy range. Continuous and quasi-mono-kinetic energy spectra, respectively, will be available at NFS, produced by the interaction of a deuteron beam on a thick Be converter and by the 7Li(p,n) reaction on thin converter. The pulsed neutron beam, with a flux up to two orders of magnitude higher than those of other existing time-of-flight facilities, will open new opportunities of experiments in fundamental research as well as in nuclear data measurements. In addition to the neutron beam, irradiation stations for neutron-, proton- and deuteron-induced reactions will be available for cross-sections measurements and for the irradiation of electronic devices or biological cells. NFS, whose first experiment is foreseen in 2018, will be a very powerful tool for physics, fundamental research as well as applications like the transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors.

Relatively high counting rates were registered in a proton inelastic scattering experiment on 16 O and 28 Si using HPGe detectors which was performed at the Tandem facility of IFIN-HH, Bucharest. In consequence, dead time corrections were needed in order to determine the absolute γ -production cross sections. Considering that the real counting rate follows a Poisson distribution, the dead time correction procedure is reformulated in statistical terms. The arriving time interval between the incoming events ( Δ t ) obeys an exponential distribution with a single parameter - the average of the associated Poisson distribution. We use this mathematical connection to calculate and implement the dead time corrections for the counting rates of the mentioned experiment. Also, exploiting an idea introduced by Pommé et al. , we describe a consistent method for calculating the dead time correction which completely eludes the complicated problem of measuring the dead time of a given detection system. Several comparisons are made between the corrections implemented through this method and by using standard (phenomenological) dead time models and we show how these results were used for correcting our experimental cross sections. [ABSTRACT FROM AUTHOR]

The two-proton radioactivity of Fe was studied experimentally with a time projection chamber. The aim of the experiment was the reconstruction of the proton tracks in three dimensions. Energy and angular correlations have been determined and the data are compared with theoretical models, in particular with a three-body model. Moreover, the decay of Cr was studied and β-delayed one-, two- and three-proton emission could be established. The correlations observed for β-delayed two-proton emission favour a sequential emission. Finally, β-delayed two-proton emission was observed for the first time for Ni. [ABSTRACT FROM AUTHOR]

The unbound nucleus 18Na, the intermediate nucleus in the two-proton radioactivity of 19Mg, is studied through the resonant elastic scattering 17Ne(p,17Ne)p. The spectroscopic information obtained in this experiment is discussed and put in perspective with previous measurements and the structure of the mirror nucleus 18N. [ABSTRACT FROM AUTHOR]

New results on two-proton radioactivity, predicted 50 years ago and observed for the first time in 2002, are presented. These results have been obtained with a time projection chamber at the LISE3 facility of GANIL. After 45Fe, the direct observation of the two protons for 54Zn is only the second such case from a long lived ground-state two-proton emitter. The new results are discussed and future perspectives highlighted. [ABSTRACT FROM AUTHOR]

The shell structure of the nucleus implies the existence of magic numbers. Since several years many indications have been accumulated, theoretically as well as through experiments at various laboratories around the world, that if one moves away from stability, the location of the magic numbers shifts as an inescapable consequence of the evolving nature of the nuclear force itself. In this respect, it is the balance between the tensor and spin-orbit components that seems particularly instrumental. Illustrative examples from recent experiments at Ganil, at the neutron-rich and proton-rich side of the nuclear chart for N or Z equal 20 or 28, will be presented here. [ABSTRACT FROM AUTHOR]

Proton-rich isotopes of zinc and germanium, 57Zn and 61Ge, have been produced by fragmentation of a 70Ge beam at the LISE3 facility of GANIL. Their main decay characteristics have been studied after implantation in a double-sided silicon strip detector. In addition, the production cross-sections of proton-rich isotopes in the copper-to-germanium region have been determined. These cross-sections are much lower than predicted by the EPAX formula. These findings question to some extent the production rates expected for present and future fragmentation facilities. [ABSTRACT FROM AUTHOR]

In an experiment performed at the LISE3 facility of GANIL, the isotope 54Zn and its decay via two-proton emission were observed for the first time. In addition, preliminary results indicate that three implantation events of 48Ni were observed. One of the associated decay events is compatible with a two-proton emission. New data on the decay of 45Fe and its two-proton branch were recorded at the same time. The results for 54Zn are compared to theory. [ABSTRACT FROM AUTHOR]

The excitation function for the elastic-scattering reaction p(18Ne, p)18Ne was measured with the first radioactive beam from the SPIRAL facility at the GANIL laboratory and with a solid cryogenic hydrogen target. Several broad resonances have been observed, corresponding to new excited states in the unbound nucleus19Na. In addition, two-proton emission events have been identified and are discussed. [ABSTRACT FROM AUTHOR]

The n_TOF facility at CERN is a source of neutrons produced by spallation of 20 GeV/c protons onto a lead target. The outstanding characteristics of this source (very high intensity, 200 m flight path, wide spectral function) make it an extremely useful tool for studying neutron induced reactions. The neutrons in the energy region from 1 to 10 MeV are particularly interesting for producing nuclei with large neutron excess by fission. The onset of an asymmetric fission mode at these energies seems to considerably enhance the yield of neutron rich species. Therefore, a method could emerge for producing neutron rich rare earth nuclei in a region up to now inaccessible. [Copyright &y& Elsevier]

The strength functions of the π f 5 / 2 , π p 3 / 2 and π f 7 / 2 orbitals in neutron-rich 71 Cu were obtained in a 72 Zn(d, 3 He) 71 Cu proton pick-up reaction in inverse kinematics using a radioactive beam of 72 Zn at 38 MeV/u. A dedicated set-up was developed to overcome the experimental challenges posed by the low cross section of the reaction and the low energy of the outgoing 3 He particles. The excitation-energy spectrum was reconstructed and spectroscopic factors were obtained after analysis of the angular distributions with the finite-range Distorted-Wave Born Approximation (DWBA). The results show that unlike for the π f 5 / 2 orbital and contrary to earlier interpretation, the π f 7 / 2 single-particle strength distribution is not appreciably affected by the addition of neutrons beyond N = 40 . [ABSTRACT FROM AUTHOR]

Excited states have been studied in 28Na using the β-decay of implanted 28Ne ions at the Grand Accelerateur National d'lons Lourds/LISE as well as the in-beam γ-ray spectroscopy at the National Superconducting Cyclotron Laboratory/S800 facility. New states of positive (Jπ = 3+,4+) and negative (Jπ = l--5-) parity are proposed. The former arise from the coupling between 0d5/2 protons and 0d3/2 neutrons, while the latter are attributable to couplings of 0d5/2 protons with 1 p3/2 or 0f1/2 neutrons. While the relative energies between the Jπ = l+-4+ states are well reproduced with the USDA interaction in the N = 17 isotones, a progressive shift in the ground-state binding energy (by about 500 keV) is observed between 26F and 30Al. This points to a possible change in the proton-neutron 0d5/2-0d3/2 effective interaction when moving from stability to the drip line. The presence of Jπ = 1--4- negative-parity states around 1.5 MeV as well as of a candidate for a Jπ = 5- state around 2.5 MeV give further support to the collapse of the N = 20 gap and to the inversion between the neutron 0f7/2 and 1p3/2 levels below Z = 12. These features are discussed in the framework of shell-model and energy-density-functional calculations, leading to predicted negative-parity states in the low-energy spectra of the 26F and 25O nuclei. [ABSTRACT FROM AUTHOR]

The two protons emitted in the decay of 54Zn have been individually observed for the first time in a time projection chamber. The total decay energy and the half-life measured in this work agree with the results obtained in a previous experiment. Angular and energy correlations between the two protons are determined and compared to theoretical distributions of a three-body model. Within the shell model framework, the relative decay probabilities show a strong contribution of the p2 configuration for the two- proton emission. After 45Fe, the present result on 54Zn constitutes only the second case of a direct observation of the ground state two-proton decay of a long-lived isotope. [ABSTRACT FROM AUTHOR]

Abstract: In a series of experiments at the SISSI/LISE3 facility of GANIL conducted between 1999 and 2004, we have collected decay information for proton-rich nuclei between 36Ca and 56Zn. The data allowed us to study the decay properties of 26 nuclei. The main experimental information obtained for all nuclei is their β-decay half-life and their total β-delayed proton emission branching ratio. For many nuclei, individual proton groups and γ rays were identified and allowed us to establish first partial decay schemes for some of the nuclei studied. In addition, mass-excess values have been determined for some of the nuclei by means of the isobaric multiplet mass equation. For 50Ni, the decay via β-delayed two-proton emission could be tentatively identified. The decay of 49Ni allowed for the first time to identify the first state in 48Fe. The experimental data are confronted to model predictions for the half-life and the mass-excess values. [Copyright &y& Elsevier]

Proton reaction cross-section measurements on various stable and neutron-rich nuclei (4,6He, 7–9Li, 9–11Be, 21–24F, 22–26Ne, 25–29Na and 29–32Mg) were performed via the attenuation method at intermediate energies (∼35–75AMeV) and using a cryogenic hydrogen target. The results are discussed in the framework of different approaches of the nucleon–nucleus potential. [Copyright &y& Elsevier]