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Fission fragment mass distributions were measured in the heavy-ion induced fission using 238U target nucleus. The mass distributions changed drastically with incident energy. The results are explained by a change of the ratio between fusion and qasifission with nuclear orientation. A calculation based on a fluctuation dissipation model reproduced the mass distributions and their incident energy dependence. Fusion probability was determined in the analysis. Evaporation residue cross sections were calculated with a statistical model in the reactions of 30Si+238U and 34S+238U using the obtained fusion probability in the entrance channel. The results agree with the measured cross sections of 263,264Sg and 267,268Hs, produced by 30Si+238U and 34S+238U, respectively. It is also suggested that the sub-barrier energies can be used for heavy element synthesis.

International audience; Various types of reactions and identification techniques were applied in the investigation of formation cross sections and decay properties of transuranium elements. The fusion--evaporation reactions with heavy targets, recoil--separation techniques and identification of nuclei by the parent--daughter generic coincidences with the known daughter‐nuclei after implantation into position--sensitive detectors were the most successful tools for production and identification of the heaviest elements known presently. This technique may be further improved and presently it may be very promising for the identification of new elements, search for new isotopes and measurement of new decay data for the known nuclei. At the Flerov Laboratory of Nuclear Reactions (JINR, Dubna), investigations of the complete fusion reactions leading to the synthesis of heavy and superheavy nuclei with the use of heavy ion beams from a powerful U400 cyclotron have been an important part of the experimental program. It is planned to upgrade U400 cyclotron of the FLNR, to deliver beams with higher intensities and smooth variation of energies. New experimental set up, the velocity filter, is now developing for synthesis and studies of the decay properties of heavy nuclei. At the focal plane of the separator GABRIELA set up (α,β,γ detectors array) will be installed. © 2010 American Institute of Physics

The production of 283112 in 48Ca induced nuclear reactions was investigated using physical and chemical separation techniques. In the reaction 48Ca on 238U, four events were registered at the SHIP velocity filter. The mean atomic mass of the evaporation residues (EVR)

An overview of present experimental investigation of superheavy elements is given. The data are compared with theoretical descriptions. Results are reported from an experiment to confirm production of element 112 isotopes in irradiation of 238UF4 with 48Ca. One spontaneous fission event was measured, which agrees with three events of previously measured data which had been assigned to the decay of 283112. However, more experimental work is needed in order to obtain an independent and unambiguous confirmation of previous results.

We report on the status of target development for the heavy-element program at GSI, namely for the SHIP experiment. We present some recent results in enhancing the durability of the targets irradiated with the more and more intense heavy-ion beams. The enhancement of the beam intensity is necessary in order to keep beam times at reasonable length despite cross sections in the picobam region. We synthesised new compound targets on 208Pb-basis with significantly higher melting temperatures and built up a target monitoring system. To investigate the high-current targets and develop an active cooling system we built up a test bench for offline experiments.

The isotopes 257,255Rf, 257,256Db, 253,252Lr have been produced in bombardments of 207,208Pb and 209Bi target nuclei with 50Ti and identified by their α-decay. New or improved decay data could be obtained. Analysis of the fine structure of the α-decay pattern of 257Rf allowed the construction of a first tentative level scheme for the daughter nucleus 253No and also the identification of a low lying high spin isomeric state, while from α-γ- coincidence measurements for 255Rf a first tentative level scheme of the daughter nucleus 251No was derived. For 257Db we found that two nuclear levels decay by α-emission and populate also different levels in the daughter nucleus 253Lr. The levels are produced by the reaction process. In bombardments of 209Bi with 50Ti at ECN*=26.4 MeV and 30.8 MeV the previously unknown isotopes 256Db and 252Lr were identified.