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We report on a new cross-section measurement for the ³He(ɑ,λ)7Be reaction at three medium energies of £cm between 1 and 3 MeV. The interest stems from the significant role played by the reaction in calculating an accurate solar neutrino flux and the primordial 7Li abundance. The energy dependence of the astrophysical S34 factor observed in the present work, especially above 1 MeV, highlights the need to constrain theories in order to obtain a precise extrapolated value for S34(0). In this context, a comparison with the recent theoretical work in a fully microscopic fermionic molecular dynamics approach and a few other representative calculations emphasize the need for further experimental as well as theoretical work to resolve the existing conflicts. [ABSTRACT FROM AUTHOR]

A multihit capacity setup was used to study the decay of the dripline nucleus 31Ar, produced at the ISOLDE facility at CERN. A spectroscopic analysis of the &3946;-delayed three-proton decay of 31Ar is presented for the first time together with a quantitative analysis of the β-delayed 2py decay. A new method for determination of the spin of low-lying levels in the fip daughter 30S using proton-proton angular correlations is presented and used to determine that the spin of the 5.2-MeV level is most likely 3+ with 4+ also possible. The half-life of 31Ar is found to be 15.1(3) ms. An improved analysis of the Fermi fi strength including the β3p-decay mode gives a total measured branching ratio of 3.60(44)%, which is lower than the theoretical value found to be 4.24(43)%. Finally, a previously unidentified γ transition from the isobaric analog state in the decay of 33Ar has been found. [ABSTRACT FROM AUTHOR]

Abstract: We have observed -delayed proton emission from the neutron-rich nucleus 11Be by analyzing a sample collected at the ISOLDE facility at CERN with accelerator mass spectrometry (AMS). With a branching ratio of the strength of this decay mode, as measured by the -value, is unexpectedly high. The result is discussed within a simple single-particle model and could be interpreted as a quasi-free decay of the 11Be halo neutron into a single-proton state. [Copyright &y& Elsevier]

Highlights: [•] A nanometric mesoporous CaO powder was developed and studied in terms of sintering. [•] For the first time a nanostructured target material was operated at ISOLDE. [•] Unlike past CaO targets, stable yields over time of n-deficient argon were delivered. [•] Higher (exotic) Ar yields were obtained at lower temperatures and proton intensities. [Copyright &y& Elsevier]

Resonances just above the proton threshold in 30S affect the 29P(p, y)30S reaction under astrophysical conditions. The (p,γ)-reaction rate is currently determined indirectly and depends on the properties of the relevant resonances. We present here a method for finding the ratio between the proton and γ partial widths of resonances in 30S. The widths are determined from the β2p- and β py-decay of 31Ar, which is produced at the ISOLDE radioactive ion beam facility at the European research organization CERN. Experimental limits on the ratio between the proton and γ partial widths for astrophysical relevant levels in 30S have been found for the first time. A level at 4689.2(24) keV is identified in the γ spectrum, and an upper limit on the Γp/Γγ ratio of 0.26 (95% C.L.) is found. In the two-proton spectrum two levels at 5227(3) keV and 5847(4) keV are identified. These levels were previously seen to γ decay and upper limits on the Γγ/Γp ratio of 0.5 and 9, respectively, (95% C.L.) are found, where the latter differs from previous calculations. [ABSTRACT FROM AUTHOR]

Abstract: A novel Phoswich design based on new generation scintillator crystals is presented. The detector composed from a combination of a (Ce) with a (Ce) crystal in one cylinder coupled to a photo multiplier tube has been tested both for incident gamma rays in the range of 0.3–6MeV, as well as for high energy protons in the range 120–180MeV. The Phoswich assembly has not significantly deteriorated the energy resolution, which for 662KeV gamma rays gives a resolution of 4.5%, while for high energy protons (=180MeV) an energy resolution of 1% was obtained. It is shown that the signals from the two crystals can be separated in an event by event based mode. Using direct digitizing of the detector pulse an off-line pulse-shape analysis was performed built either on a total to tail or total to pulse height method in order to fully identify the incoming radiation. Our aim with this R&D is to in the future build a detector which is able to detect with good efficiency and resolution over a wide energy range; 0.1–30MeV gamma rays and 20–400MeV protons. Monte Carlo simulations made in order to design the next prototype are presented. [Copyright &y& Elsevier]

A measurement of the final state distribution of the 8B ß decay, obtained by implanting a 8B beam in a double-sided silicon strip detector, is reported here. The present spectrum is consistent with a recent independent precise measurement performed by our collaboration at the IGISOL facility, Jyväskylä [O. S. Kirsebom et al., Phys. Rev. C 83, 065802 (2011)]. It shows discrepancies with previously measured spectra, leading to differences in the derived neutrino spectrum. Thanks to a low detection threshold, the neutrino spectrum is for the first time directly extracted from the measured final state distribution, thus avoiding the uncertainties related to the extrapolation of matrix fits. Combined with the IGISOL data, this leads to an improvement of the overall errors and the extension of the neutrino spectrum at high energy. The new unperturbed neutrino spectrum represents a benchmark for future measurements of the solar neutrino flux as a function of energy. [ABSTRACT FROM AUTHOR]

In stellar helium burning, 16O represents the endpoint of the helium-burning sequence due to the low rate of 16O(α,γ)20Ne. We present a new direct measurement of the total capture reaction rate of 16O(α,γ)20Ne at Ec.m.=2.26 MeV employing the DRAGON recoil separator. For the first time, the total S factor and its contributing direct capture transitions could be determined in one experiment. [ABSTRACT FROM AUTHOR]

Abstract: Preliminary studies in preparation for an absolute cross-section measurement of the radiative capture reaction 3He()7Be with the DRAGON recoil separator have demonstrated beam suppression at the 90% confidence level. A measurement of this cross section by observation of 7Be recoils at the focal plane of the separator should be virtually background free. [Copyright &y& Elsevier]

A measurement of the final state distribution of the (8)B β decay, obtained by implanting a (8)B beam in a double-sided silicon strip detector, is reported here. The present spectrum is consistent with a recent independent precise measurement performed by our collaboration at the IGISOL facility, Jyväskylä [O. S. Kirsebom et al., Phys. Rev. C 83, 065802 (2011)]. It shows discrepancies with previously measured spectra, leading to differences in the derived neutrino spectrum. Thanks to a low detection threshold, the neutrino spectrum is for the first time directly extracted from the measured final state distribution, thus avoiding the uncertainties related to the extrapolation of R-matrix fits. Combined with the IGISOL data, this leads to an improvement of the overall errors and the extension of the neutrino spectrum at high energy. The new unperturbed neutrino spectrum represents a benchmark for future measurements of the solar neutrino flux as a function of energy.