On the question of fine structure in νp and EK for 233U and 235U

doi:10.1016/0375-9474(76)90358-4

Nuclear Physics A

Volume 265, Issue 2, 19 July 1976, Pages 337-348

https://doi.org/10.1016/0375-9474(76)90358-4 Get rights and content

Abstract

The question of fine structure in the variation of the average number of prompt neutrons, $ν_{p}$ , emitted per fission with energy in the neutron fission of ²³³U and ²³⁵U has been examined. Consistent structure has been found in measurements of both $ν_{p} and E_{K}$ (the average total fission fragment kinetic energy) for ²³³U. Channel analysis of the neutron fission cross section of ²³³U allows the structure to be calculated quantitatively provided the collective energy at the second hump in the fission barrier is weakly coupled to the nuclear degrees of freedom at scission. A similar calculation for neutron fission of ²³⁵U supports the case for the absence of fine structure in $ν_{p} and E_{K}$ for this nucleus.

References (30)

Yu.A. Blyumkina et al.
Nucl. Phys.
(1964)
J.W. Meadows et al.
J. Nucl. Energ.
(1967)
P.P. D'yachenko et al.
Phys. Lett.
(1970)
J.W. Boldeman et al.
J. Nucl. Energ.
(1970)
N.N. Ajitanand et al.
Nucl. Phys.
(1970)
R.L. Walsh et al.
J. Nucl. Energ.
(1971)
D.S. Mather et al.
Nucl. Phys.
(1965)
J.C. Hopkins et al.
Nucl. Phys.
(1963)
G.N. Smirenkin et al.
J. Nucl. Energ.
(1959)
B.B. Back et al.
Nucl. Phys.
(1971)

F. Manero et al.

Atom. Energy Rev.

(1972)

M. Soleilhac et al.

P.P. D'yachenko et al.

Sov. J. Nucl. Phys.

(1972)

P.P. D'yachenko et al.

Sov. J. Nucl. Phys.

(1969)

M.V. Savin et al.

Cited by (12)

Photofission and photoneutron measurements on 241Am between 5 and 10 MeV
1992, Nuclear Physics, Section A
Measurements are presented of the photofission and photoneutron cross sections of ²⁴¹Am and of the mean number $v$ of neutrons per fission between 5 and 10 MeV. The measurements were carried out using a bremsstrahlung beam generated by the Harwell electron linear accelerator HELIOS and a 1.5 g metallic ²⁴¹Am target. Neutron multiplicity distributions were recorded using a high-efficiency neutron detector. Yield measurements made in steps of 50 keV show possible evidence for a resonance at 6.1 MeV in the photofission cross section, but the statistical significance is not high.
Spin dependence of ḡn<inf>p</inf> and E ̄<inf>K</inf> for 239Pu(n, f) in the resonance region: The discrepancy between results above and below 1 eV
1986, Nuclear Physics, Section A
Étude de la dissipation d'énergie dans la fission de 234u à l'aide de la réaction 233U(d, pf)
1982, Nuclear Physics, Section A
The energy balance in the fission of ²³⁴U has been investigated on the basis of experimental results from the ²³³U(d, pf) reaction. Taking into account the neutron evaporation we have deduced the total kinetic energy and excitation energy distributions of the primary fragments as functions of the excitation energy of the fissioning nucleus. The neutron evaporation temperatures have been adjusted so as to reproduce the average value and width of the measured kinetic energy distributions for each fragmentation. Excitation energy distributions of the fragments have been deduced. The data are discussed in the framework of the liquid-drop model with shell corrections. Evidence for energy dissipation in the fission of ²³⁴U, involving drastic changes in the scission configuration, is shown for some fragmentation modes.
Fission fragment energy-velocity correlation measurements for the 233U(d, p⨍)-reaction
1979, Nuclear Instruments and Methods
A new experimental method is proposed to determine, as a function of excitation energy of the fissioning nucleus, the mass and energy distributions of the fragments for both pre- and post-neutron emission. From these distributions also the average number of neutrons emitted by the fission fragments as a function of initial fragment masses can be derived. The method is based on the measurement of both fragment kinetic energies and velocities in charged-particle induced fission through reactions such as (d, p⨍) where the emitted charged particle is used as starting time for the fragment velocity determination. The major interest lies in the precision of about 0.5 amu in the pre-neutron mass determination. Details of the experimental arragement and the method of data analysis are given. Typical experimental results obtained from the ²³³U(d, p⨍) reaction are shown and compared with previously reported results.
Fission fragment angular distributions for neutron fission of 232Th and their interpretation with a triple-humped fission barrier
1977, Nuclear Physics, Section A
The fission fragment angular distributions have been measured for the neutron fission of ²³²Th at a number of energies near the neutron threshold. An exhaustive search has been made for a set of transition states and barrier parameters that would simultaneously fit the angular distributions and reproduce quantitatively the structure seen in the neutron fission cross section. No satisfactory fit to both types of data could be obtained with a double-humped fission barrier. However, use of a triple-humped fission barrier does provide a reasonable fit to all the experimental data.
The \ ̄gn<inf>p</inf> values for neutron fission of 232Th near threshold
1977, Nuclear Physics, Section A
The average number of prompt neutrons emitted per fission, $ν_{p}$ , for ²³²Th(n, f) has been measured between 1.35 and 2.1 MeV. No large maximum in $ν_{p}$ at about 1.4 MeV was seen. The behaviour of $ν_{p}$ and of $E_{K}$ fs, the average total fragment kinetic energy, have been calculated using both a double-humped and triple-humped fission potential barrier. Significant disagreement with existing $E_{K}$ data for ²³²Th(n, f) is apparent.

View all citing articles on Scopus

View full text

Article preview

Nuclear Physics A

Abstract

References (30)

Nucl. Phys.

J. Nucl. Energ.

Phys. Lett.

J. Nucl. Energ.

Nucl. Phys.

J. Nucl. Energ.

Nucl. Phys.

Nucl. Phys.

J. Nucl. Energ.

Nucl. Phys.

Atom. Energy Rev.

Sov. J. Nucl. Phys.

Sov. J. Nucl. Phys.

Cited by (12)

Photofission and photoneutron measurements on <sup>241</sup>Am between 5 and 10 MeV

Spin dependence of ḡn<inf>p</inf> and E ̄<inf>K</inf> for <sup>239</sup>Pu(n, f) in the resonance region: The discrepancy between results above and below 1 eV

Étude de la dissipation d'énergie dans la fission de <sup>234</sup>u à l'aide de la réaction <sup>233</sup>U(d, pf)

Fission fragment energy-velocity correlation measurements for the 233U(d, p⨍)-reaction

Fission fragment angular distributions for neutron fission of <sup>232</sup>Th and their interpretation with a triple-humped fission barrier

The \ ̄gn<inf>p</inf> values for neutron fission of <sup>232</sup>Th near threshold