Universität zu Köln

Yaneva, Aleksandrina ORCID: 0000-0001-7335-7148 (2024). Spectroscopy of excited states in 94Pd and development of tools for Slowed Down Beams at FAIR. PhD thesis, Universität zu Köln.

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Abstract

This doctoral thesis presents results from the first experiment of the DESPEC campaign performed at GSI Helmholtzzentrum für Schwerionenforschung (Darmstadt, Germany) as part of FAIR Phase-0. The goal of the experiment was precise measurement of electromagnetic transition rates in the Tz = +1 94Pd nucleus, in particular the lifetimes of the yrast Iπ = 8+ and 6+ states below the Iπ = 14+, T1/2 = 499(13) ns isomer. The nuclei of interest were produced by the fragmentation of 124Xe primary beam impinging on a 4 g/cm2 9Be target, after being accelerated to 982 MeV/u in the UNILAC and the SIS18 synchrotron. The reaction products were separated and identified on an event-by-event basis in the FRS and then transported to the final focal plane, where the DESPEC setup was located. There the fragments were implanted in the AIDA active stopper. Subsequent γ-rays following the decay of populated isomeric states in the nuclei of interest were detected by the GALILEO and FATIMA detector arrays. The half-live of the 8+ state in 94Pd was measured by employing the Generalized Centroid Difference method, which uses the fast-timing methodology. In addition, a limit for the half-live of the 6+ state in 94Pd was obtained. The experimental electromagnetic transition rates B(E2) were determined using the measured lifetimes and the values were compared to shell-model calculations, employing different interactions and model spaces. This thesis also reports on an experiment aimed at testing detector prototypes for future HISPEC-10 slowed-down beam campaigns at FAIR. With the goal of observing Coulomb excitations of even-even stable nuclei, a 64Ni (or similar) beam was requested impinging on a 197Au target. However, only a 208Pb primary beam was available and the experiment was finally performed using this beam. As the 208Pb primary beam at 250 MeV/u reaches the experimental cave, it interacts with a thick βPlastic detector, the signal from which was used as the trigger for all other detector systems. A mechanical structure holding degraders with different thicknesses was used to slow down the beam. For ion tracking and time-of-flight measurement three MCP detectors were used. After interacting with the 197Au target, located downstream of the MCPs, the beam was stopped in a ΔE-E telescope, used for tracking and identification. For detecting γ-rays two three-fold DEGAS HPGe clusters were used, pointed towards the target. The data from this experiment is still being analyzed, but some findings are reported in this work.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Yaneva, Aleksandrina apy@abv.bg orcid.org/0000-0001-7335-7148 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-737339
Date:	2024
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute for Nuclear Physics
Subjects:	Physics
Uncontrolled Keywords:	Keywords Language gamma spectroscopy, Fast timing, Shell Model, proton-neutron interaction, Isovector vs. Isocalar pairing, Slowed Down Beams English
Date of oral exam:	17 September 2024
Referee:	Name Academic Title Jolie, Jan Prof. Dr. Reiter, Peter Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/73733