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2. Recent HRIBF Research - Measurement of Evaporation Residues at Sub-Barrier Energies
(D. Shapira, Spokesperson)

Experiment RIB121 was approved last year in order to study excitation function for fusion of 134Sn with 64Ni. Since the mass A=166 ions extracted from the ion source (sulfides of Sn and Te) contained approximately equal amounts of 134Sn and 134Te sulfides, it was realized that to obtain the 134Sn + 64Ni data two experiments will have to be run. Evaporation residues from the mixture of both beams were measured together with a count of the number of 132Sn and 134Te particles that hit the target (and also any other contaminants). After that the tune of the source was changed from extracting mass 166 to extracting mass 134, the latter contained more then 96% of 134Te. The evaporation-residue cross section for 134Sn + 64Ni was measured with the same target and energy. Since the ratio of Sn to Te is known in both experiments, the two measurements yielded evaporation-residue cross sections for both 134Sn + 64Ni and 134Te + 64Ni. The system used in these measurements is shown in Fig. 1. Events recorded in the ionization chamber that show the separated evaporation residue data appear in Fig. 2, and Fig. 3 shows the 2-d map of A=134 beam particles delivered in the experiment. A full excitation function for 134Te + 64Ni evaporation residue data is shown in Fig. 4. The runs for 134Sn + 64Ni data were cut short because of a breakdown of the isobar separator magnet and will be continued this summer.

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