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.