ISBN 9783843937740

978-3-8439-3774-0, Reihe Physik

Simon Glynn Pickstone
Upgrading the particle spectrometer SONIC and (p,p'γ) coincidence measurements on Mo-92, Mo-94, and Ni-60

157 Seiten, Dissertation Universität Köln (2018), Softcover, A5

Zusammenfassung / Abstract

SONIC@HORUS is a combined particle- and γ-detector array at the Institut für Kernphysik, Universität zu Köln. Its upgrade is described in this thesis and its power to study high-energy dipole excitations using the particle-γ technique is demonstrated.

To achieve a higher particle detection efficiency and improve the general setup, a complete redesign of the SONIC array was indicated and culminated in the third version of SONIC. The characteristics of each version are summarised and benefits of the final version are presented.

The treatment of the raw data is presented, which was tailored to the existing HORUS array and the data acquisition. Introducing the Doppler-shift correction—even at rather low beam energies of 10 MeV to 15 MeV—greatly improves the γ-ray energy resolution. To get a more reliable full-energy peak efficiency, an experimental determination of the high-energy efficiency up to 7 MeV is presented. Explaining the particle-γ method in detail shows its great power to analyse the excitation and decay behaviour of nuclei, especially if other reaction and decay channels are dominating.

For all the nuclei presented in this thesis (Mo-92, Mo-94, and Ni-60), this is shown by a comprehensive comparison to the decay behaviour of well-known low-lying levels. At higher energies, the excitation patterns deduced from the (p,p’γ) measurements are compared to existing (γ,γ’) data. Furthermore, the particle-γ coincidence technique allows to deduce a high number of γ-decay branching ratios to the first three excited states in all three nuclei. Comparisons to theoretical calculations and previous measurements are drawn where available.

Concluding, the results are discussed and systematic studies are suggested, contributing to the understanding of the underlying structure of dipole strength in atomic nuclei.