Unveiling confinement in pure gauge SU Baker, M; Chelnokov, V; Cosmai, L ...
The European physical journal. C, Particles and fields,
10/2022, Letnik:
82, Številka:
10
Journal Article
Characteristics of spontaneous fission of 250No Svirikhin, A. I.; Andreev, A. V.; Yeremin, A. V. ...
Physics of particles and nuclei letters,
2017/7, Letnik:
14, Številka:
4
Journal Article
Recenzirano
This study describes an experiment on investigating the properties of spontaneous fission of shortlived neutron-deficient nuclei synthesized in the reaction of complete fusion
48
Ca +
204
Pb =
252
...No*. The experiment is performed using the SHELS separator and the beam of multicharged ions at U-400 accelerator (LNR, JINR). Two activities undergoing spontaneous fission, which can be related to the ground and isomeric states of
250
No nucleus, are registered. The half-lives, total kinetic energies of fission fragments, and neutron multiplicities are measured for the short-lived nuclei. The average number of neutrons per fission for the activity with
t
1/2
= 5.1 ± 0.3 μs is = 4.38 ± 0.13 μs, and for nuclei with the half-life
t
1/2
= 36 ± 3 μs it is xxxxx.
We present results of the second experiment on the chemical identification of element 112. Similar to the first test in 2000, we aimed at the production of the spontaneously fissioning
112 nuclei ...with
≈3min. A
(with some Nd) target, 2mg of U/cm
thick, was bombarded with 233-MeV
Ca ions (the energy in the middle of the target layer). The nuclei recoiling from the target were thermalized in flowing helium. The target chamber was connected through a 25m long capillary to detectors of
-particles and fission fragments. All the equipment and detectors were kept at ambient temperature. According to the test experiments, of all the heavy elements produced in the bombardment, only Hg, Rn and At could be transported to the detectors. The first detecting device was similar to that used earlier – an assembly of 8 pairs of PIPS detectors coated with gold. Here one would observe the decay of element 112 atoms if they like Hg adsorbed on gold. The atoms which were not retained and freely passed through the PIPS detectors entered a new, flow-through ionization chamber, 5000 cm
in volume, optimized for detecting fission fragments. The PIPS detectors and the ionization chamber were placed inside a large assembly of
He – filled neutron counters to detect prompt neutrons from the fission events. In 22.5 days, a beam dose of 2.8×10
ions was accumulated. More than 95 of the simultaneously produced
-active
Hg (
=49 s) were found deposited already on the first pair of PIPS detectors; meanwhile, all the PIPSs did not detect any fission event. In the ionization chamber, eight fission events were observed in coincidence with neutron counts while the expected background was insignificant. Hence, the spontaneous fissions of the volatile activity can be conclusively attributed to the decay of element 112 produced in the fusion reaction
Ca+
U, and formerly observed in Dubna physical experiments. Evaluation of the experimental data in terms of the adsorption enthalpies indicates much weaker interaction of element 112 with Au than that of Hg. One can conclude that in the given chemical environment, element 112 behaves like Rn rather than like Hg. The formation cross section of
112 estimated from the data amounts to several pb. The experiments were carried out at the Flerov Laboratory of Nuclear Reactions at JINR in November–December 2001.
The problem of studying the spontaneous fission of nuclei from the exotic region of short-lived neutron-deficient isotopes with
Z
≥ 100 is considered. A combined detecting system is created in the ...focal plane of the VASSILISSA separator. The main part of this system is a neutron detector that allows us to measure the yields of spontaneous fission neutrons from nuclei produced in a total fusion reaction with heavy ion beams in the on-line mode. This procedure is used for the first time to acquire data on the emission of spontaneous fission neutrons from short-lived
244,246
Fm isotopes. Data gathered earlier for
252
No isotopes are refined in the scope of this work.
An experiment on the study of the
246
Fm spontaneous fission was conducted using the SHELS separator. The isotope was synthesized in the complete fusion reaction of
40
Ar beam ions and
208
Pb target ...nuclei. The neutron yields of
246
Fm spontaneous fission (
ν
¯
=
3.79
±
0.30
,
σ
ν
2
=
2.1
) were obtained using the SFiNx detector system. The multiplicity distribution of emitted prompt neutrons was restored using the Tikhonov method of statistical regularisation (
ν
¯
r
=
3.79
±
0.20
,
σ
ν
r
2
=
2.8
). The spontaneous fission branching ratio (
b
SF
=
0.061
±
0.005
) and the half-life (
T
1
/
2
=
1
.
50
-
0.07
+
0.08
s) of the isotope were determined. The experimental data were compared with scission point model predictions. An agreement was observed in the average number of neutrons per spontaneous fission process. However, the forms of the experimental and model prompt neutron multiplicity distributions differ significantly.
Spontaneous Fission of $^{256}$Rf, New Data Svirikhin, A.I.; Yeremin, A.V.; Izosimov, I.N. ...
Physics of particles and nuclei letters,
07/2016, Letnik:
13, Številka:
4
Journal Article
Recenzirano
Spontaneous fission properties of the short-lived neutron-deficient 256Rf nucleus produced in thecomplete fusion reaction with a beam of multiply charged heavy 50Ti ions from the U-400 cyclotron ...(FLNR,JINR) are experimentally investigated. Its half-life and decay branching ratio are measured. The averagenumber of neutrons per spontaneous fission of 256Rf ( = 4.47 ± 0.09) is determined for the first time.
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.
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