Date: June 2000
After the first observation of doubly-magic 48Ni on the LISE3 separator of GANIL in September 1999 and the observation relatively high counting rates for 49Ni (100 events), 45Fe (50 events) and 42Cr (300 events), a new experiment was performed to study these nuclei. In the present experiment the experimental setup was optimised for spectroscopic studies. The experimental setup comprised a silicon detector telescope including a double-sided silicon strip detector with x and y strips in which the nuclei of interest were implanted. This detector enabled us to correlate implantation and decay events in the same pixels. This setup was surrounded by four germanium detectors including one clover detector. The setup is shown on the photo below.
Une cible de production en carbone a été utilisée en place et lieu de la cible de nickel choisie dans A carbon production target was used instead of the nickel target used in the previous experiment. Predictions with the EPAX code and different results on other accelerators made us believe that the production rates might be higher with the carbon target. Test measurements performed during the setting up of the 1999 experiment with a carbon target at the entrance of the LISE3 beam line enforced this belief.
In fact, the target effect finally observed was extremely important with an order of magnitude lower production rate for the most exotic species and made us return to the nickel target in order to recover the relative and absolute production rates from the previous experiments in 1999.
The 58Ni beam intensity (75 MeV/nucleon) delivered by the accelerator was several mirco-amperes. (up to 4.5 A at maximum). The figures presented below are results from online analyses. The isotopes produced are clearly identified and separated on the two-dimensional spectrum of energy loss as a function of the time-of-flight through the separator. The energy loss was measured by the silicon detectors of the telescope, whereas the time-of-flight is determined between the silicon detectors and the micro-channel plate detector in the first LISE focal plane on the one hand and the same silicon detectors and the radio-frequency of the cyclotrons on the other hand.
The decay spectra below are rather preliminary results again from online analyses. More refined values will be obtained during the offline analysis.
In the same section :