Results of the experiments aimed at the study of fission and quasi-fission processes in the reactions
12C+
204Pb,
48Ca+
144,154Sm,
168Er,
208Pb,
244Pu,
248Cm;
58Fe+
208Pb,
244Pu,
248Cm, and
64Ni+
...186W,
242Pu are presented in the work. The choice of the above-mentioned reactions was inspired by recent experiments on the production of the isotopes
283112,
289114 and
283116 at Dubna 1,2 using the same reactions. The
58Fe and
64Ni projectiles were chosen since the corresponding projectile-target combinations lead to the synthesis of even heavier elements. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR, Russia), the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL, Italy) and the Accelerator of the Laboratory of University of Jyvaskyla (JYFL, Finland) using the time-of-flight spectrometer of fission fragments CORSET3 and the neutron multi-detector DEMON4,5. The role of shell effects and the influence of the entrance channel on the mechanism of the compound nucleus fusion-fission and the competitive process of quasi-fission are discussed.
Dedicated ionization chamber (IC) was built and installed to measure the energy loss of very heavy nuclei at
2.7
MeV/
u
produced in fusion reactions in inverse kinematics (beam of
208
Pb
). After ...going through the IC, products of reactions on
12
C
,
18
O
targets are implanted in a Si detector. Their identification through their α-decay chain is ambiguous when their half-life is short. After calibration with Pb and Th nuclei, the IC signal allowed us to resolve these ambiguities. In the search for rare super-heavy nuclei produced in fusion reactions in inverse or symmetric kinematics, such a chamber will provide direct information on the nuclear charge of each implanted nucleus.
The low-lying level structure of the unbound system $^{16}$B has been investigated via single-proton removal from a 35 MeV/nucleon $^{17}$C beam. The coincident detection of the beam velocity ...$^{15}$B fragment and neutron allowed the relative energy of the in-flight decay of $^{16}$B to be reconstructed. The resulting spectrum exhibited a narrow peak some 85 keV above threshold. It is argued that this feature corresponds to a very narrow (GAMMA ≪100 keV) resonance, or an unresolved multiplet, with a dominant PI(p3/2)$^{−1=$ ⊗ V(d$^{3}$$_{5/2}$)J=3/2+ PI(p3/2)$^{−1}$ ⊗ V (d$^{2}$$_{5/2, s1/2}$)J=3/2+ configuration which decays by d-wave neutron emission.
Nuclear dissipation in capture reactions is investigated using backtracing. Combining the analysis procedure with dynamical models, the difficult and long-standing problem of competition and mixing ...of quasi-fission and fusion-fission is solved for the first time. At low excitation energy a new protocol able to handle low statistics data gives access to the prescission neutron multiplicity in two different systems 48Ca + 208Pb, Pu. The results are in agreement with a domination of fusion-fission in the case of 256No and an equal mixing of quasi-fission and fusion-fission in the case of Z = 114. The nature of the relevant dissipation is determined as one-body dissipation.
Experiments performed at Lab. Nat. SATURNE on neutron produced by spallation from proton beams in the range 0.8 - 1.6 GeV are presented. Experimental data compared with codes show a significant ...improvement of the recent intra-nuclear cascade (J. Cugnon). This is also true in the same way for the neutron production from thick targets. However the model underestimates the energetic neutrons produced in the backward direction and other quantities as residual nuclei cross sections are not accurately predicted.
PDF
