Description du sujet de thèse

Title: Measurement of the beta decay properties of nuclei of interest for the nucleosynthesis of 44Ti with the new (NA)2STARS detector with high efficiency and very good resolution

The SEN team performs measurements of beta decay properties of neutron-rich nuclei of interest for nuclear
structure, nuclear astrophysics and neutrino and reactor physics. In 2024, the team and its international
collaborators (France, Spain, UK, Turkey, Czech Republic) obtained funding for the design, development and
construction of the (NA)2STARS detector, a second-generation Total Absorption Spectrometer (TAS). This
detector will combine the excellent efficiency of first-generation TAS detectors with very good resolution and
rapid response, and will be used to explore the properties of exotic nuclei of interest for nuclear astrophysics, for
nuclear structure and for reactor neutrino physics.
In its initial version (in 2026), it will include 13 crystals of LaBr3 in addition to the existing TAS (Rocinante or
DTAS) detectors. The geometric layout of this detector is currently being designed for the first experiment to be
carried out at GANIL on the LISE beamline in early 2026. The detector should be built in 2025, at the same time
as the analysis and simulation tools are put in place. The first area that the group wishes to study during for this
first experiment is the nucleosynthesis of 44Ti, formed during supernova explosions and whose observations are
important for understanding their mechanism. However, little is known about some of the reactions that lead to the
production or destruction of 44Ti. The aim of the new experiment is to reduce the uncertainties associated with the
nucleosynthesis of this important astrophysical nucleus.
The range of work that the PhD student will be able to carry out is very broad, as he/she will be able to follow the
project in its entirety. This could include preparatory design/simulation, setting up test benches in the laboratory,
preparing data processing and analysis codes, taking part in setting up the experiment on site, taking data and then
analysis. Depending on the PhD student's affinities and the time available, a comparison with theoretical
predictions could be carried out.
With the proposed thesis, the PhD student is therefore likely to acquire skills ranging from instrumentation to
phenomenology with, most probably, a major component in data analysis, providing a very complete research profile.

Contexte de travail

Subatech is a joint research unit of CNRS/Nucléaires et Particules, Nantes U university and IMT Atlantique. Within this subatomic physics laboratory, research is carried out on a range of fundamental and applied topics in three main areas: nuclear and energy, nuclear and health, and the high-energy universe. The SEN team's expertise in total absorption gamma-ray spectroscopy contributes to both the High Energy Universe and Nuclear & Energy research areas. The team carries out experiments in international collaboration with facilities such as the University of Jyvaskyla in Finland, ISOLDE at CERN and GANIL in France, as will be the case for the proposed thesis.

The candidate must :
- hold a Master of Science (MSc) in physics, preferably subatomic, or equivalent university studies with 300 ECTS at the time of application
- have good skills in analysis methods widely used in experimental physics, such as C++ programming, the CERN/ROOT software package, detector simulation with Monte-Carlo codes (mainly Geant4).
- The candidate must :
- demonstrate strong motivation, curiosity and autonomy.
- Fluency in English is a must.
- be able to write scientific reports and present results orally
- Be able to work both independently and collaboratively in an international team environment.

Contraintes et risques

The constraints and risks will be :
- travel abroad 1 or 2 times a year to take part in other nuclear physics experiments, as well as workshops, conferences and experimental analysis meetings.
- Risk of exposure to ionizing radiation (under laboratory supervision in compliance with legislation),
- Handling during experimental set-up.