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Title: Breakout from the hot-CNO cycle via the ¹⁸Ne(α,p)²¹Na reaction
Author: Groombridge, Darren
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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The 18Ne(a,p)21Na reaction is of great importance to Nuclear Astrophysics as it provides a route to breakout from the hot-CNO cycle, possibly leading to the formation of the elements up to A~100. This particular reaction has been studied using a 18Ne beam, available at Louvain-la-Neuve, together with a helium gas target system previously developed for the investigation of (a,p) reactions with a radioactive beam. This study covered an energy region from ~1.7-2.9 MeV in the centre of mass frame o the 18Ne+a system. A change in the detector geometry resulted in an increase in the detection efficiency and significantly reduced the proton background that hindered the previous measurement. A direct measurement of the energy loss of the 18Ne beam, as it passed through He gas, was undertaken to reduce a major source of uncertainty in the determination of the stellar reaction rate. This showed a linear relationship, between beam energy and distance traversed within the gas, over an energy scan of ~8-16 MeV and gave an energy loss of (1.55 ±0.01) MeV/cm and (15.96 ± 0.02) MeV for the energy of the 18Ne beam upon entry into the gas. This information was used, together with kinematic information from the protons, to provide information on the level structure in the compound nucleus, 22Mg. Ten states have been identified within an energy region of ~10-11 MeV and are in good agreement with information that is currently known. These resonances were used to calculate an enhanced stellar reaction rate which shows reasonable agreement with theoretical predictions [44] at and above a temperature of 1.5 GK.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available