The <sup>18</sup>Ne(a,p)<sup>21</sup>Na 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 <i>A</i>~100. This particular reaction has been studied using a <sup>18</sup>Ne 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 <sup>18</sup>Ne+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 <sup>18</sup>Ne 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 <sup>18</sup>Ne 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, <sup>22</sup>Mg. 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.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:651842 |
| Date | January 2001 |
| Creators | Groombridge, Darren |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/10930 |
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