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XVth International Conference on Electromagnetic Isotope Separators and Techniques related to their Applications (EMIS2007), Deauville : France (2007)
Influence of decay in the target on measurement of ion-source efficiency and release times
G. Lhersonneau1, 2
SPIRAL2 Collaboration(s)

The PLOG collaboration investigates the properties of high-density UC targets for producing beams of neutron-rich nuclei obtained as fission products in the frame of SPIRAL2, SPES and EURISOL. The tests carried out at the IRIS on-line mass separator at PNPI-Gatchina, Russia, aim at the future development of massive targets of circa 1 kg to be irradiated by neutrons of intermediate energy. The present status of this work shall be presented in other contributions of our collaboration. Here we present a formalism for the experimental determination of target efficiency and release times. Since fission generates a wide (Z, A) distribution of products, decay in the target of nuclei more exotic than the one investigated is an extra production channel. This feeding, not in phase with the accelerator beam, contributes with a different time structure. A model has been designed that explicitly takes into account the channels where beta decay occurs during diffusion either in the grains or during effusion between them. We also discuss the measurement of release efficiency for nuclei having isomer(s). A fraction of the isomers, populated via fission and occasionally via beta decay, remains in the target. It adds to the cross-section for formation of the ground state through the isomeric transition. This fraction depends on the respective values of radioactive lifetime and release time. Release efficiency and release curves must be treated in a consistent frame to obtain meaningful data.
1 :  LNL - Laboratori Nazionali di Legnaro
2 :  GANIL - Grand Accélérateur National d'Ions Lourds
Physique/Physique/Physique des accélérateurs