.
Neutron angular distributions in spontaneous fission of
252
Cf are investigated. The CORA experiment, performed at IPHC Strasbourg, aims at elucidating neutron emission mechanisms in the fission ...process. The experimental setup is composed of the angle-sensitive twin ionisation chamber CODIS for the detection of fission fragments and the DEMON neutron detector assembly. The development of a simulation toolkit based on GEANT4 and MENATE_R is described, adapted as a strategy to investigate the influence of experimental conditions on the observed properties of neutrons emitted. Besides the kinematic neutron anisotropy in the laboratory system due to neutron evaporation from moving fragments, two additional effects are discussed which may have an influence on the angular distributions of neutrons: scission neutrons and dynamic neutron emission anisotropy in the CM system of fragments due to the spin carried by fragments. A new analysis method is presented to disentangle the dynamic anisotropy from the other effects in an independent way. For the dynamic anisotropy only an upper limit could be found. Results for the angular correlation
(
n
,
n
)
between two evaporated neutrons and the correlation
(
n
,
LF
)
between an evaporated neutron and the Light Fragment direction of flight are reported.
Experimental neutron distributions have been investigated in the spontaneous fission of
252
Cf at IPHC in Strasbourg. The CORA experiment associating the CODIS twin ionisation chamber and the neutron ...multi-detector DEMON aimed to solve an long-standing problem in fission: the possible emission of scission neutrons and/or the presence of a dynamical anisotropy in the neutron evaporation by the moving fission fragments. A new method allowing to establish the dynamical anisotropy in an independent way is presented. The results obtained from a comparison with simulations based on GEANT4 are shown.
.
The current status of fission dynamics studies in heavy-ion collisions around the Coulomb barrier is illustrated with the
34
S +
186
W reaction. The fission-fragment mass and total kinetic energy ...were measured at the ALTO facility at IPN Orsay, France, with a dedicated set-up using the (
v
,
E
) approach. The measurement reveals the presence of an asymmetric fission component on top of a predominantly symmetric distribution. The asymmetric structure, pointed out for the first time, is discussed along with results of previous experiments studying the same reaction. While these analyses suggested the contribution from either quasi-fission or pre-equilibrium fission, we offer an alternative interpretation, in terms of shell-driven compound-nucleus fission. The present measurement demonstrates the critical influence of resolution when addressing puzzling cases, situated at the crossroads of the various channels opened in a heavy-ion collision. Current status in the field clearly calls for innovative measurements involving manifold correlations and new observables. The outcome of the attempt done in this work in this direction, based on the coincident measurement of prompt
-rays is reported, and encouraging perspectives are discussed.
Detection of neutron clusters Marqués, F. M.; Labiche, M.; Orr, N. A. ...
Physical review. C, Nuclear physics,
04/2002, Letnik:
65, Številka:
4
Journal Article
Bimodal fission of Hs Itkis, I M; Itkis, M G; Knyazheva, G N ...
Journal of physics. Conference series,
01/2014, Letnik:
515, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Mass and energy distributions of fission fragments obtained in the reactions 22Ne + 249Cf, 26Mg + 248Cm, and 22Ne + 238U have been measured. A special attention will be paid on the properties of ...mass-energy distribution of fission fragments obtained in the reaction 26Mg + 248Cm at an excitation energy of 35 MeV. At this energy shell effects should become more effective in fission, the TKE distribution of symmetric fragments obtained in the reaction 26Mg + 248Cm differs strongly from a Gaussian shape. Besides a low-energy component, a high-energy component, not foreseen in the LDM, arises. This is attributed to the fact that both fission fragments are close to the spherical neutron shell N 82. It means that for the compound nucleus 274Hs*, formed in the reaction 26Mg + 248Cm, the phenomenon of bimodal fission was observed for the first time. For the compound nucleus 260No* formed in the reaction 22Ne + 238U at the initial excitation energy of 41 MeV the bimodal fission as well as superasymmetric fission were observed.
Neutron-rich isotopes of heavy nuclei are until now poorly studied. In this work we investigate neutron-rich osmium isotopes produced in multi-nucleon transfer reactions. The reaction 136Xe+208Pb at ...energy near Coulomb barrier is used for production of osmium isotopes. The CORSAR-V setup is used to record the characteristics of osmium isotopes. The separation of the reaction products is based on their respective volatility. Experimental results are presented and discussed.
The low-lying level structure of the unbound system
16B has been investigated via single-proton removal from a 35 MeV/nucleon
17C beam. The coincident detection of the beam velocity
15B fragment and ...neutron allowed the relative energy of the in-flight decay of
16B to be reconstructed. The resulting spectrum exhibited a narrow peak some 85 keV above threshold. It is argued that this feature most probably corresponds to a very narrow (
Γ
≪
100
keV
) resonance with a dominant
π
(
p
3
/
2
)
−1
⊗
ν
(
d
5
/
2
3
)
J
=
3
/
2
+
+
π
(
p
3
/
2
)
−1
⊗
ν
(
d
5
/
2
2
,
s
1
/
2
)
J
=
3
/
2
+
configuration which decays by
d-wave neutron emission.
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