Decay Spectroscopy

Nuclear decay experiments are highly sensitive and can provide spectroscopic information on highly exotic nuclei with projectile fragmentation/fission production yields as low as a few particles per day. Such experiments are currently being performed as part of the RISING collaboration at GSI (Regan, Coordinator), the precursor of the DESPEC/HISPEC collaboration. The UK has had the leading role in both the instrumentation and physics development of the RISING project. The mechanical support structure of the RISING array and the development and commissioning of the RISING ‘active stopper’ implantation, decay detector are both UK-led. UK physicists have run a number of highly successful  and isomer-decay experiments at GSI to study exotic, proton-drip-line nuclei and also with large neutron-excess. More than half of the decay experiments accepted by the GSI Programme Advisory Panel for RISING have had UK spokespersons or co-spokespersons (Regan, Podolyák, Bruce, Gelletly, Wadsworth and Woods).

The latest conceptual picture of the intended LaBr3(Ce) fast-timing array.

DESPEC focuses on measurements of radioactive decays from the most exotic nuclei in terms of N/Z ratio. These will be implanted in the position-sensitive silicon-detector array, AIDA, situated at the final focus of the Super-FRS. Measurements of radioactive decays following +, , , proton, neutron and internal conversion emission in coincidence with discrete-line gamma-ray emissions will provide the first information on excited nuclear states in a wide range of isotopes at unprecedented N/Z ratios. Measurements of -decay half-lives, Q-values, decay heat, and neutron-emission probabilities of exotic neutron-rich nuclei are of major relevance to the rapid-neutron capture process (r process) path and are the major physics focus of this work package. The DESPEC detection system is modular, optimising setups for each individual experiment. In the current project, UK effort is focussed on the construction of the fast timing gamma-ray array using LaBr3(Ce) scintillation detectors (see picture).

The tasks for this work package include the design, trial assembly in the UK, and in-situ commissioning at FAIR of these instruments.

Leader: Prof. P. H. Regan – University of Surrey

Institutions: Brighton, Manchester, Surrey, UWS, Daresbury