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Title: Measurement of the ¹⁸Ne(α,p)²¹Na reaction rate, and its implications for Nuclear Astrophysics
Author: Bradfield-Smith, William
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1999
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Experimental work has been carried out at Louvain-la-Neuve to study the reactions 13N(α,p)16O and 18Ne(α,p)21Na in inverse kinematics with a gaseous helium target. The experimental method devised was tested using the reaction 13N(α,p)16O, as the cross section was calculable from data on 16O(p,α)13N[1,2,3,4], the inverse reaction. This test experiment showed that the experimental error obtainable in the deduction of the cross section resonance strength's was 30%, making the technique of practical use in the investigation of (α,p) reactions of interest to Nuclear Astrophysics. The reaction 18Ne(α,p)21Na, which is important as a break-out mechanism from the hot CNO cycle into the rp-process during explosive hydrogen burning, has been investigated, and values for the cross sections resonance strengths have been extracted from the experimental data. A stellar reaction rate, based only upon the observed resonances, has been calculated and compared with theoretical predictions[5]. A good agreement was obtained at and above a temperature of 2.5 109K, whilst at lower temperatures the experimentally reaction rate obtained fell rapidly below the calculated value. This discrepancy was due to the fact that the theoretical calculation of the stellar reaction rate used resonances at energies below 2.5 MeV, not observed experimentally. At low temperature the reaction flux through these resonances dominates the stellar reaction rate. The experimental stellar reaction rate, though only a lower limit, has been applied to a one mass zone X-ray burst model[6]. This network calculation has shown that break-out via 18Ne(α,p)21Na is sufficient to trigger the burst for a type I X-ray burster, and allow mass to flow from the CNO region to the mass 100 region via the rp-process.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available