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The underlying physics triggering core collapse supernovae is not fully understood but observations of material ejected during such events helps to solve this puzzle. In particular, several satellite based γ-ray observations of the isotope 44Ti have been reported recently. Conveniently, the amount of this isotope in stellar ejecta is thought to depend critically on the explosion mechanism. The most influential reaction to the amount of 44Ti in supernovae is Ti44(α,p)V47. Here we report on a direct study of this reaction conducted at the REX-ISOLDE facility, CERN. The experiment was performed with a 44Ti beam at Elab = 2.16MeV/u, corresponding to an energy distribution, for reacting α-particles, centred on Ecm = 4.15 with a 1σ width of 0.23 MeV. This is, for the first time, well within the Gamow window for core collapse supernovae. The material from which the 44Ti beam was extracted originates from highly irradiated components of the SINQ spallation neutron source of the Paul Scherrer Institute. No yield above background was observed, enabling an upper limit for the rate of this reaction to be determined. This result is below expectation, suggesting that the Ti44(α,p)V47 reaction proceeds more slowly than previously thought. Implications for astrophysical events, and remnant age, are discussed. © 2014 The Authors.

The DRAGON facility for the study of radiative capture reactions has an extended gas target, surrounded by an array of BGO detectors. The distribution of detected gamma rays amongst the segmented array permits an estimate of the reaction position and consequently of the resonance energy. We report a study of the technique, using the 24 Mg(p, γ ) 25 Al reaction. Energy determination to better than 0.5% has been demonstrated.

Preliminary studies in preparation for an absolute cross-section measurement of the radiative capture reaction 3 He( α , γ ) 7 Be with the DRAGON recoil separator have demonstrated beam suppression > 10 14 at the 90% confidence level. A measurement of this cross section by observation of 7 Be recoils at the focal plane of the separator should be virtually background free.