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 precession 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.
With the aid of the Geant4 Monte Carlo simulation package a new detection system has been designed for the focal plane of the recoil separator VASSILISSA situated at the Flerov Laboratory of Nuclear ...Reactions, JINR, Dubna.
GABRIELA (
Gamma
Alpha
Beta
Recoil
Investigations with the
ELectromagnetic
Analyser VASSILISSA) has been optimised to detect the arrival of reaction products and their subsequent radioactive decays involving the emission of
α
- and
β
-particles, fission fragments,
γ
- and X-rays and conversion electrons. The new detector system is described and the results of the first commissioning experiments are presented.
Correlation studies of the H 5 spectrum Golovkov, M. S.; Grigorenko, L. V.; Fomichev, A. S. ...
Physical review. C, Nuclear physics,
12/2005, Letnik:
72, Številka:
6
Journal Article
The measured yield of evaporation residues in reactions with massive nuclei have been well reproduced by using the partial fusion and quasifission cross sections obtained in the dinuclear-system ...model. The influence of the orientation angles of the projectile- and target-nucleus symmetry axes relative to the beam direction on the production of the evaporation residues is investigated for the
48
Ca +
154
Sm reaction as a function of the beam energy. At the low beam energies only the orientation angles close to
αP
= 30° (projectile) and
αP
= 0°–15° (target) can contribute to the formation of evaporation residues. At large beam energies (about
E
c.m.
= 140–180 MeV) the collisions at all values of orientation angles
αP
and
α
T
of reactants can contribute to the evaporation residue cross section which ranges between 10–100 mb, while at
E
c.m.
> 185 MeV the evaporation residue cross section ranges between 0.1–1 mb because the fission barrier for the compound nucleus decreases by increasing its excitation energy and angular momentum.
An experiment has been performed at IPHC Strasbourg, aimed at the detailed investigation of angular correlations in the neutron emission from spontaneous fission of 252Cf. Fission fragments were ...measured by the angle-sensitive double ionization chamber CODIS while neutrons were detected by a set of 60 DEMON scintillator counters. The main aim of the experiment is the observation of the correlation between the fragment spins and neutron emission anisotropy. Preliminary results, based on the Monte-Carlo simulations, as well as the preliminary analysis of the experimental data are shown.
Ar+Ni collisions at 77 MeV/u were studied in the experiment E286 performed at GANIL. An important advantage of this experiment was an application of the neutron detector DEMON for registration of ...both neutral and charged particles. This feature allows to compare characteristics of neutrons and protons detected by the same detector and gives a possibility to determine the influence of the Coulomb field on the proton emission. Estimation of a charge of the emitting source was performed by comparing energy spectra of neutrons and protons detected under identical experimental conditions. The experimental results were compared with the prediction of the SIMON model.
The time scales for nuclear fission have been explored using both pre- and postfission neutrons and GDR gamma rays. Four systems were investigated: 133-MeV /sup 16/O+/sup 176/Yb and /sup 208/Pb and ...104-MeV /sup 4/He+/sup 188/Os and /sup 209/Bi. Fission fragments were measured in coincidence with PPACs. The neutrons were detected using eight detectors from the DEMON array, while gamma rays were measured using the US BaF/sub 2/ array. The pre- and postfission gamma rays were determined using moving source fits parallel and perpendicular to the fission fragment emission directions. The time scales for fission for the neutrons were determined using the neutron clock technique. The gamma-ray data were fitted using a statistical model calculation based on the code CASCADE. The results of the fits from both data types were used to extract nuclear friction coefficients, gamma , and fission time scales. The gamma values ranged from 7 to 20, while the fission times were (31-105)*10/sup -21/s.
Isomeric states in $^{253}$No Lopez-Martens, A.; Hauschild, K.; Dorvaux, O. ...
The European physical journal. A, Hadrons and nuclei,
06/2007, Letnik:
32
Journal Article
Recenzirano
Odprti dostop
Isomeric states in 253No have been investigated by conversion-electron and gamma-ray spectroscopy with the GABRIELA detection system. The 31 micro second isomer reported more than 30 years ago is ...found to decay to the ground state of 253No by the emission of a 167 keV M2 transition. The spin and parity of this low-lying isomeric state are established to be 5/2+. The presence of another longer-lived isomeric state is also discussed.
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