General information
Organisation
The French Alternative Energies and Atomic Energy Commission (CEA) is a key player in research, development and innovation in four main areas :
• defence and security,
• nuclear energy (fission and fusion),
• technological research for industry,
• fundamental research in the physical sciences and life sciences.
Drawing on its widely acknowledged expertise, and thanks to its 16000 technicians, engineers, researchers and staff, the CEA actively participates in collaborative projects with a large number of academic and industrial partners.
The CEA is established in ten centers spread throughout France
Reference
SL-DRF-24-0289
Direction
DRF
Thesis topic details
Category
Corpuscular physics and outer space
Thesis topics
INVESTIGATION OF THE NUCLEAR TWO-PHOTON DECAY IN SWIFT FULLY STRIPPED HEAVY IONS
Contract
Thèse
Job description
The nuclear two-photon, or double-gamma decay is a rare decay mode in atomic nuclei whereby a nucleus in an excited state emits two gamma rays simultaneously. Even-even nuclei with a first excited 0+ state are favorable cases to search for a double-gamma decay branch, since the emission of a single gamma ray is strictly forbidden for 0+ ? 0+ transitions by angular momentum conservation. The double-gamma decay still remains a very small decay branch (<1E-4) competing with the dominant (first-order) decay modes of atomic internal-conversion electrons (ICE) or internal positron-electron (e+-e-) pair creation (IPC). Therefore we will make use of a new technique to search for the double-gamma decay in bare (fully-stripped) ions, which are available at the GSI facility in Darmstadt, Germany. The basic idea of our experiment is to produce, select and store exotic nuclei in their excited 0+ state in the GSI storage ring (ESR). For neutral atoms the excited 0+ state is a rather short-lived isomeric state with a lifetime of the order of a few tens to hundreds of nanoseconds. At relativistic energies available at GSI, however, all ions are fully stripped of their atomic electrons and decay by ICE emission is hence not possible. If the state of interest is located below the pair creation threshold the IPC process is not possible either. Consequently, bare nuclei are trapped in a long-lived isomeric state, which can only decay by double-gamma emission to the ground state. The decay of the isomers would be identified by so-called time-resolved Schottky Mass Spectroscopy. This method allows to distinguish the isomer and the ground state state by their (very slightly) different revolution time in the ESR, and to observe the disappearance of the isomer peak in the mass spectrum with a characteristic decay time. After a first successful experiment establishing the double-gamma decay in 72Ge a new experiment has been accepted by the GSI Programme Committee and its realization is planned for 2024.
University / doctoral school
PHENIICS (PHENIICS)
Thesis topic location
Site
Saclay
Requester
Position start date
01/10/2024
Person to be contacted by the applicant
KORTEN Wolfram w.korten@cea.fr
CEA
DRF/IRFU/DPhN/LENA
Drf/IRFU/DPhN
Bat 703 - Orme des Merisiers
91191 Gif/Yvette cedex
+33169084272
Tutor / Responsible thesis director
KORTEN Wolfram w.korten@cea.fr
CEA
DRF/IRFU/DPhN/LENA
Drf/IRFU/DPhN
Bat 703 - Orme des Merisiers
91191 Gif/Yvette cedex
+33169084272
En savoir plus
https://www.researchgate.net/profile/Wolfram_Korten
http://irfu.cea.fr/dphn/Phocea/Vie_des_labos/Ast/ast_sstheme.php?id_ast=293
https://www.gsi.de/en/work/research/appamml/atomic_physics/experimental_facilities/esr.htm