Experiments in Solenoidal Spectrometers — from Isospin Breaking to Nuclear Fission
Doctoral thesis, 2026
The outcome of two nuclear physics experiments extracting very different physics information is presented. They both employ (d,p) reactions in inverse kinematics, demonstrating the versatility of solenoidal spectrometers.
The first experiment at Argonne National Laboratory, using the HELIOS setup, studied breaking of the isospin symmetry in excited states of 18O and 18F. Relative spectroscopic factors of the populated states are compared to investigate the similarity of isobaric analogue states in the isospin multiplet A = 18. The results show overall good agreement between analogue states and consistency with shell-model predictions for most levels. No statistically significant evidence for enhanced isospin symmetry breaking was observed within the experimental uncertainties.
The second part of the thesis focuses on extending the ISS setup at ISOLDE, CERN, to allow studies of fission of neutron-rich isotopes. To cope with the limited intensity available at radioactive beam facilities, an efficient setup for the detection of fission fragments was designed, installed, and commissioned. The setup performed as expected and enabled a proof-of-principle measurement of the fission of 233U. While the full extraction of physics observables has not yet been performed, the work demonstrates the feasibility of the method and establishes a foundation for future studies of fission in exotic nuclei.
The first experiment at Argonne National Laboratory, using the HELIOS setup, studied breaking of the isospin symmetry in excited states of 18O and 18F. Relative spectroscopic factors of the populated states are compared to investigate the similarity of isobaric analogue states in the isospin multiplet A = 18. The results show overall good agreement between analogue states and consistency with shell-model predictions for most levels. No statistically significant evidence for enhanced isospin symmetry breaking was observed within the experimental uncertainties.
The second part of the thesis focuses on extending the ISS setup at ISOLDE, CERN, to allow studies of fission of neutron-rich isotopes. To cope with the limited intensity available at radioactive beam facilities, an efficient setup for the detection of fission fragments was designed, installed, and commissioned. The setup performed as expected and enabled a proof-of-principle measurement of the fission of 233U. While the full extraction of physics observables has not yet been performed, the work demonstrates the feasibility of the method and establishes a foundation for future studies of fission in exotic nuclei.
Isospin
Isobaric Analogue States
Nuclear Shell Model
Nuclear Physics
ISS
HELIOS
Nuclear Fission
ISOLDE
r-process
CERN
ANL
PJ-salen, Kemigården 1, Chalmers
Opponent: Director de Recherche Araceli Lopez-Martens, CNRS, France.
Author
Anna Kawecka
Subatomic, High Energy and Plasma Physics 1
Atomic nuclei are tiny, complex systems made of protons and neutrons interacting through fundamental forces. Despite decades of research, no single theory fully explains all nuclei. Atomic nuclei occur as simple structures but can also exhibit exotic forms like halos, shaped by many-body interactions and symmetries. To understand them, physicists perform experiments that create and probe excited nuclear states, measuring properties such as energy, spin, and lifetime. These insights help reveal how nuclear forces work, how elements form in the universe, and how nuclear processes can be applied in energy and medicine.
This thesis tackles two key questions. First, it studies isospin symmetry – how similar protons and neutrons behave – and investigates how this symmetry is broken. Second, it explores fission in neutron-rich nuclei, a process crucial for forming heavy elements in astrophysical events. Both topics are examined using the same experimental method: reactions transfering a neutron in inverse kinematics with advanced spectrometers. This approach allows precise probing of nuclear structure, even in unstable nuclei, providing data to test theories and improve our understanding of fundamental nuclear behavior.
This thesis tackles two key questions. First, it studies isospin symmetry – how similar protons and neutrons behave – and investigates how this symmetry is broken. Second, it explores fission in neutron-rich nuclei, a process crucial for forming heavy elements in astrophysical events. Both topics are examined using the same experimental method: reactions transfering a neutron in inverse kinematics with advanced spectrometers. This approach allows precise probing of nuclear structure, even in unstable nuclei, providing data to test theories and improve our understanding of fundamental nuclear behavior.
Creation of heavy elements in neutron-star mergers
Knut and Alice Wallenberg Foundation (2020.0076), 2021-01-01 -- 2025-12-31.
Subject Categories (SSIF 2025)
Other Physics Topics
Subatomic Physics
DOI
10.63959/chalmers.dt/5884
ISBN
978-91-8103-427-1
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5884
Publisher
Chalmers
PJ-salen, Kemigården 1, Chalmers
Opponent: Director de Recherche Araceli Lopez-Martens, CNRS, France.