Fission yield measurement using multi-nucleon transfer reactions*

The multi-nucleon transfer (MNT) reaction, where a few nucleons are given from a beam nucleus to a target nucleus, is very useful way to populate a multitude of nuclides in a wide excitation energy range. We have developed a detector system at the JAEA tandem accelerator facility to measure fission observables such as fission-fragment mass distributions (FFMD), prompt fission neutron multiplicities and so on for compound nuclei produced in the MNT reaction using actinide targets. The system consists of a silicon DE-E telescope and multi-wire proportional counters for detection of ejectiles and fission fragments, respectively. An array of liquid scintillators is placed around the target for neutron detection. By identifying the ejectile, the initial compound nucleus is also identified.

 At high excitation energies, fission of nuclides produced via neutron emission from the initial compound nucleus also contribute to FFMD. In the present study, effects of the multi-chance fission on FFMDs were successfully separated by a combination of a systematic data set obtained from experiments using ¹⁸O beams and actinide targets and a dynamical fission calculation based on the fluctuation-dissipation model. In the workshop, results of the prompt-fission neutron measurement will also be presented.