Search

Very neutron-rich nuclei near the A = 195 r-process waiting point were produced as projectile fragments from a 208 Pb primary beam at GSI, Darmstadt, by cold fragmentation. After in-flight separation, the fragments were implanted in an active catcher, and time correlations to the subsequent beta-decay were established. Due to the periodic operation cycles of the synchrotron, providing the primary beam, the background shows a complex time structure, which prevents applying well established analytical methods to extract the half-life information. A new mathematical analysis method has been developed, which is based on a Monte Carlo code, simulating the time sequence of implantation and beta detection according to the experimental conditions, leaving the beta lifetimes and the beta detection efficiency as free parameters. In addition, both the analysis of the experimental data and the simulation were performed in time-reversed sequence. The ratio of forward/backward time spectra contains the information of the "true" fragment-beta correlations. Half-lives were obtained from two-dimensional fits of the measured and simulated ratios of time correlations in forward- and backward-time direction by the least-squares method, being the lifetime and the beta-detection efficiency the two fitting parameters. Half-lives of 8 heavy neutron-rich nuclei approaching the r-process waiting point A = 195 have been determined.

The SPALADIN experiment using the inverse-kinematics technique where the heavy-ion beam is sent onto a liquid-hydrogen target has been carried out at GSI (Darmstadt, Germany) in order to study the spallation of 56 Fe. On an event-by-event basis, spallation residues, light-charged fragments and neutrons have been detected in coincidence. The set-up is based on a large aperture magnet (ALADiN) equipped with a time-projection chamber (TPC), a hodoscope and a high-efficiency neutron detector. The combination of the inverse kinematics and of the acceptance of the set-up focuses the measurement on the low centre-of-mass energy fragments of the reaction essentially originating from the de-excitation of the prefragment formed at the end of the intranuclear cascade. Data taken at 1GeV per nucleon have been analysed. Preliminary results on coincidence observables are shown and compared to theoretical calculations. We emphasize on the identification of different types of multi-fragment final states which correspond to different decay channels and allow to probe different decay mechanisms.