Search

Nuclei in the neutron-rich region beyond 132Sn have been produced recently by various experiments using fission. Using isomer and β-decay studies nuclear structure data has been collected on the orbital evolution and collectivity in the region with both the increase of proton and neutron numbers. Examples on particular questions related to the g.s. of the A=136 odd-odd 136Sb nucleus and its heavier neighbours are given in the scope of expectations by shell-model theory. [ABSTRACT FROM AUTHOR]

Radiative capture reactions on rare targets and prompt spectroscopy of neutron-rich nuclei produced in the neutron-capture induced-fission of 235U and 241Pu have been performed at the Institut Laue-Langevin (ILL). The highefficiency germanium (Ge) EXOGAM array has been used, complemented with Ge detectors from GASP and the ILL. LaBr3 detectors from the FATIMA collaboration have also been coupled to EXOGAM to measure lifetimes of lowlying excited states. The measured characteristics indicate very good performances of the overall setup. Some recent results will be discussed. [ABSTRACT FROM AUTHOR]

The mixing ratio of the main 320-keV, M1 + E2 ground-state γ transition in 210Bi has been more precisely quantified, allowing a significant reduction in the uncertainty of measurements of the neutroncapture cross section to the ground state of 210Bi from 25% to 0.9%. Accurate values for neutron-capture cross sections to both the ground and long-lived 9- isomeric state at 271 keV in 210Bi are of particular importance as Pb-Bi finds increased usage in Accelerator Driven Systems. [ABSTRACT FROM AUTHOR]

A large array of Ge detectors installed at ILL, around a 235U target irradiated with cold neutrons, (EXILL) allowed measurement of prompt gamma-ray cascades occurring in fission fragments with an unambiguous determination of fragments. Here we present preliminary results of a systematic comparison between experimental γ -ray intensities and those obtained from the Monte-Carlo simulation code FIFRELIN, which is dedicated to the de-excitation of fission fragments. Major γ -ray intensities in the 142Ba and 92Kr fission products, extracted from EXILL data, were compared to FIFRELIN, as well as to reported values (when available) obtained with EUROGAM2 in the spontaneous fission of 248Cm. The evolution of γ -ray intensities in 92Kr versus the complementary partner in fission (i.e. versus the total number of evaporated neutrons by the fission pair) was then extracted and compared to FIFRELIN. [ABSTRACT FROM AUTHOR]

The combination of the intense cold neutron beam available at the PF1b beam position of the Institute Laue-Langevin (ILL) in Grenoble, together with the high detection efficiency of a large array of high purity Ge detectors (HPGe) has offered a unique opportunity for a set of experiments devoted to nuclear spectroscopy on stable isotopes as well as on exotic nuclei produced in the fission process of uranium and plutonium samples. The emitted γ-rays from neutron capture on stable targets as well as from the decay of fission fragments have been acquired in a trigger-less mode to preserve a maximum of information for further off-line treatment. A dedicated fully digital acquisition system using a combination of a 14-bit 100 MS/s digitisers with a PowerPC-based VME single board computer has been developed to ensure data collection and real-time processing capabilities. The present article will describe the experimental setup as well as the specific electronic configuration used during the EXILL campaign of measurements with particular emphasis on the technical achievements as well as on the preliminary results obtained in the various experiments. [ABSTRACT FROM PUBLISHER]

Positron-electron pair creation near the threshold energy is extremely difficult to investigate by both experiments and theory. First test experiments were performed at the ILL to determine the cross sections for positron-electron pair creation near threshold using prompt γ-rays from different targets after neutron capture and conventional radioactive sources. Pair creation was studied in a Ge detector, which simultaneously acted as sample and detector. First results are presented which show a significant deviation from theoretical values near threshold. [ABSTRACT FROM AUTHOR]