The rate of destruction of 18F via the 18F + p reactions is of importance
in both novae and X-ray burster explosive scenarios. The rate
of the competing destructive reactions, 18F(p,γ)19Ne and 18F(p,α)15O,
depend upon the level structure of the compound nucleus 19Ne.
The first experiment in this thesis examines the level structure of
19Ne about the 18F + p threshold via elastic 15O(α,α)15O scattering.
The experiment was performed at the CRC Louvain-la-Neuve. A
radioactive 15O beam bombarded a thick 4He gaseous target with
elastically scattered alpha particles detected using segmented silicon
detectors.
An R-matrix approach was used to analyse the data and extract the
resonance parameters Er and Ѓα. Particular emphasis was placed on
extracting information regarding the possible 3/2+ doublet, the parameters
of which, to date, have been inferred from the mirror nucleus
19F. The nominal values for the doublet taken from the mirror are
Er = 8 and 38 keV, with Ѓα = 0.27 and 1.3 keV respectively. Following
this new analysis it has been found that the doublet straddles
the threshold at Er = -22 and 3 keV, with Ѓα = 0.15 and 3.3 keV
respectively. S-factor calculations and interference effects were also
examined.
The 18Ne(α,p)21Na reactions is believed to be a key process in X-ray
bursters. It is thought to be a possible HCNO-breakout reaction;
the mechanism responsible for producing energy to drive the X-ray
burster.
To date the reaction has been studied both directly and indirectly.
The results from each previous experiment show su cient discrepancies
to warrant a re-examination of the reaction rate. As such, the second experiment presented in this thesis revolves around a new
direct measurement of 18Ne(α,p). The experiment was undertaken
at the CRC Louvain-la-Neuve, where, a radioactive 18Ne beam impinged
upon a thin gaseous 4He target. The beam energy was chosen
to provide data points in common with previous experiments at Er
= 1.7 and 2.5 MeV. Reaction protons were detected via a segmented
silicon detector telescope system.
The total cross section calculated at Er = 2.5 MeV is 1.22 0.151
mb. An upper limit for the cross-section of 0.0208 mb was evaluated
at Er = 1.7 Me