Breakout from the hot-CNO cycle via the Ne-18(alpha,p)Na-21 reaction

The present work aims to extend the experiment reported in refs. [1] and [2] concerning the Ne-18(alpha, p)Na-21 reaction, by making a measurement at a lower energy (1.50-3.00 MeV in the centre-of-mass frame of the Ne-18 + alpha system) in an attempt to observe other states in the level structure of Mg-22 below 10.57 MeV. A direct measurement of the energy loss of the Ne-18 beam, as it passed through He gas, was undertaken to reduce one source of uncertainty in the determination of the stellar reaction rate. The experiment was undertaken at the radioactive ion beam facility at Louvain-la-Neuve

Hot CNO breakout: Status of the d(Ne-18,p)Ne-19*(alpha) O-15 reaction

Post-accelerated radioactive ion beams produced at Louvain-la-Neuve, Belgium have been used to investigate the O-15(alpha,gamma)Ne-19 reaction, which is generally considered as the potential breakout reaction from the hot CNO cycle. This reaction may not only lead to the synthesis of proton-rich nuclei via the rp-process, but is also thought to initiate the massive release of energy which can trigger stellar explosions such as novae and Xray bursters. The properties of this reaction have been investigated via a study of the relevant decays of excited states in Ne-19, which were populated using an inverse Ne-18(d,p) reaction. The measurements were aimed at the determination of branching ratios which, combined with knowledge of the total width of the states under investigation, allow for the modelling of the O-15(alpha,gamma)Ne-19 reaction rate. The result for the branching ratio of the E-R=4.600MeV state is found to be in good agreement with an alternative approach. The experiments have been carried out using an especially designed high granularity large solid angle silicon strip detector array consisting of 320 elements to compensate for the high decay background and limited intensity of this radioactive beam environment. The method and experimental set-up will be presented. The decay properties of selected populated resonances will be discussed. An upper limit of 10(-2) for the branching ratio of the astrophysically important state at 4.033MeV was obtained

The 15O(alpha,gamma)19Ne* reaction using a 18Ne radioactive beam

The 15O(α,γ)19Ne reaction is generally considered as a potential breakout reaction from the hot CNO cycle. Under nova conditions, the reaction rate is dominated by a single sub-Coulomb resonance at Ec.m.=504 keV which corresponds to a 19Ne excitation energy of ER=4.033 MeV. Results from a d(18Ne,19Ne)p experiment show that states of astrophysical interest are populated in this reaction. An upper limit for the α-branching ratio of the 4.033 MeV state was identified and branching ratios for other states in 19Ne were found to be in good agreement with stable beam based results