Production of neutron-rich nuclei in fission processes

Administering organization: Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia

Host organization: Dipartimento di Fisica e Astronomia "Galileo Galilei", University of Padova, Via Marzolo 8, 35131 Padova, Italy

Funding: The Unity Through Knowledge Fund

• Project number: UKF Grant Agreement No. 12/19
• Funding: 19 350 kn

Co-funding: University of Padova

• Co-funding (UniPd, in-kind): 20 000 kn

Project duration: 22.05.-03.12.2019.

• Visit duration: 07.10.-25.11.2019.

Summary:

The study of the heavy neutron-rich nuclei is at a forefront of research in nuclear physics ever since the discovery that some well established principles change far from the stability. One of the means to reach neutron-rich nuclei in the laboratory is nuclear fission. A useful tool to produce fissioning nuclei such as radioactive preactinides and actinides are multinucleon transfer reactions. Recent advance in fission studies was the full isotopic identification of fission fragments obtained by employing magnetic spectrometers and transfer-induced fission in inverse kinematics. The aim of this grant is to explore which neutron-rich fission fragments can be produced following the transfer-induced fission with the lead beams, to quantify yields that can be achieved and to define the best experimental conditions. This is especially interesting considering the lack of data for the isotopic identification of fission fragments from the lead region. Unique facility in which these goals can be achieved is University of Padova and LNL-INFN with the PRISMA spectrometer, LaBr₃ array and silicon detectors that can be coupled and used in the kinematic coincidence measurement. During this grant it is foreseen to select a system, establish a collaboration with interested groups, estimate the feasibility of the experiment, write a proposal, simulate the experimental conditions, and/or test the detectors.

Results:

The aim of this grant was fulfilled by showing that the fission with the lead beams can be used to reach neutron-rich nuclei and by calculating yields that are expected for different fission fragments. We successfully performed calculations, simulations and wrote the proposal to study transfer-induced fission and fusion-fission reactions with the doubly-magic ²⁰⁸Pb beam employing the large acceptance magnetic spectrometer for heavy ions PRISMA, the new silicon multi-detectors TRACE and gamma LaBr₃ scintillator detectors. The chosen set-up has unique performance in terms of efficiency and selectivity. The kinematic coincidence measurement with a heavy beam and a lighter target would be the first study of the kind with the PRISMA spectrometer. This is crucial for the full isotopic identification of the fission fragments, in particular to obtain fission yields. The work plan was executed in full.

In the end, the results of the project were presented at the TRACE collaboration meeting by project leader and co-leader on 22th of November. The collaboration showed very beneficial in defining the experimental details. It is worth mentioning that TRACE detectors are new segmented silicon detectors for the study of exotic structure in nuclei, developed as part of the 243 kEuro project CaRipaRo and as a part of the European highly segmented silicon array project GRIT.

Additionally, the project leader was invited by the collaboration to attend the annual GRIT workshop from 9-11 October 2019 and to present current status and selected research activities at Ruđer Bošković Institute accelerator facility, with an emphasis on detector testing capabilities that might be of interest to larger TRACE/GRIT collaboration.