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Production of RIBs: From Fusion to Fragmentation

Oleg B. Tarasov (National Superconducting Cyclotron Laboratory, Michigan State University, USA)

11h00 GANIL seminar room (105)

a coffee will be served 15mn before


The systematic measurement of fission fragment yields under different initial conditions provides a valuable benchmark for fission models which aim to understand this complex decay channel and to predict reaction product yields. Inverse kinematics yields measured by a high-resolution spectrometer is shown to be a powerful tool to identify and determine the isotopic yields of fission fragments. In the studies to be described, fragments were produced in the collision of a 238U beam at 24 MeV/u on 9Be and 12C targets at GANIL using the LISE3 fragment-separator, and at 80 MeV/u on a 12C target at NSCL/MSU using the S800 spectrograph. The reverse separator technique developed in the LISE++ package and coupled with the S800 configuration has been used to study fission mechanism properties. Using the LISE++ technique allows fragment vectors measured at the final plane of a spectrometer to be tracked backward through the spectrometer in order to reconstruct their trajectories and to deduce the reaction place and momentum vector at the target. Univocal PID of fragments close to a 238U primary beam has been obtained using the S800 beam-line.

Increased beam intensities at NSCL, RIKEN, and new facilities like FRIB in the future, coupled with advances in experimental techniques, such as the use of a two-stage separator, will allow observation of many new nuclei along the neutron drip-line. In a recent experiment production cross sections for a large number of neutron-rich nuclei produced from the fragmentation of 48Ca (140 and 345 MeV/u), 76Ge (130 MeV/u), 82Se (139 MeV/u), and 70Zn (345 MeV/u), beams were measured in RIKEN and NSCL. These experiments identified more than 30 new isotopes of the elements 11 ≤ Z ≤ 26. Systematic trends observed in the production cross sections changes in the nuclear mass surface, that can be explained with a shell model that predicts a subshell closure at N=34 around Z=20. Specific details to be presented:

Results from the recent experiment at RIKEN using a 70Zn beam aimed at the search for new isotopes in the 60Ca region.

Secondary reactions in the production target may be significant contributors. Results from different experiments on secondary reactions will be presented.

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