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In her dissertation M.Sc. Marjut Hukkanen commissioned the PIPERADE double Penning trap at University of Bordeaux and measured several new atomic masses of neutron-rich refractory isotopes using the JYLFTRAP double Penning trap at the Accelerator Laboratory of Ģ��ֱ��.

The atom consists of a nucleus which electrons orbit around. The nucleus is formed from nucleons, namely protons and neutrons, and its mass is less than the total mass of its nucleons. This is due to binding energy making a nucleus lighter than its constituents. The binding energy can be determined from masses and it is a useful quantity to study the structure of nuclei: it can give for example an indication of shape change of the nucleus. The masses of atomic nuclei are also used as a key input for the modelling of the astrophysical rapid neutron capture process (r process), which produces half of the elements heavier than iron in our universe.

The mass of a nucleus can be measured to the highest precision using a device called a Penning trap, which combines a strong magnetic field and an electric field to confine the studied ion. The PhD thesis of M.Sc. Marjut Hukkanen utilized such devices and consists of two parts: first the commissioning of a new Penning trap called PIPERADE for the new and upcoming DESIR facility of the GANIL Accelerator Laboratory is reported and finally high-precision mass measurements performed with the JYFLTRAP double Penning trap at the Accelerator Laboratory of Ģ��ֱ�� are discussed.

In her studies with the JYFLTRAP double Penning trap 15 ground-state masses and 8 isomeric state masses of neutron-rich refractory nuclei were measured. From those 8 were measured for the very first time. The novel Phase-Imagining Ion-Cyclotron-Resonance technique was utilized for the first time to separate the ground and isomeric states in neutron-rich rhodium and ruthenium isotopes. The experimentally measured masses were compared to Hartree-Fock-Bogoliubov global mass models BSkG1 and BSkG2, which predict the shape of the nuclei in this region to be triaxial. Additionally, neutron capture reaction rates for the r process were studied.

The thesis was performed in joint supervision between the Ģ��ֱ��, Finland and University of Bordeaux, France, in a so called “cotutelle” PhD program.

“I had an amazing opportunity to pursue my doctorate in cotutelle between the Ģ��ֱ�� and University of Bordeaux, allowing me to learn from a wide range of experts at two different facilities. However, the unfortunate timing of doing a PhD during the global pandemic made the program challenging”, says Hukkanen.

Marjut Hukkanen obtained her Master of Science degree at the Ģ��ֱ�� and has worked as doctoral researcher at the Ģ��ֱ��, Finland and the University of Bordeaux, France since late 2018.

M.Sc. Marjut Hukkanen defends her doctoral dissertation “Penning-trap mass spectrometry: commissioning of PIPERADE and measurements of neutron-rich A = 100-120 nuclei at JYFLTRAP” 21st of July 2023 at 12 o’clock at the Department of Physics, lecture hall FYS1 (Ylistönrinne, Survontie 9). Opponent is Professor Michael Block (Johannes Gutenberg University Mainz, Germany) and the custos is Professor Anu Kankainen (Ģ��ֱ��). The event is held in English.

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