A cyclotron as a powerful tool for mass measurements of exotic nuclei

An original method using the second cyclotron of GANIL as a high resolution mass spectrometer was recently developed to measure the masses of exotic nuclei, This direct time of flight technique has been successfully used with A = 100 isobars in the vicinity of Sn-100, produced via the fusion-evaporation reaction Cr-50 + Ni-58 at 255 MeV. The secondary ions were simultaneously accelerated and detected inside the cyclotron close to the extraction radius, using a silicon detector telescope mounted on a radially movable probe. The cyclotron was first tuned, using this detection system, with the Cr-50(11+) primary beam degraded to the same velocity as the A = 100 secondary ions, This very critical and quire tricky preliminary tuning procedure, as well as the mass determination procedure, which are common to ail the experiments using this method, are presented and discussed.