Fission Neutron Spectra and Nuclear Temperatures

Terrell, J.

doi:10.1103/physrev.113.527

Cited by 247 publications

(60 citation statements)

References 36 publications

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“…PbP, FIFRELIN). Also the sum of the residual temperature and residual energy distributions following the successive neutron emission from all fragments resulting from this modelling are in good agreement with the distributions reported by Terrell [11].…”

Section: Discussionsupporting

confidence: 79%

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Parameterisation of the residual temperature distribution based on the modelling of successive emission of prompt neutrons

Tudora

Hambsch

2018

EPJ Web Conf.

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Abstract.A new deterministic modelling taking into account the successive emission of prompt neutrons from initial fragments of a fragmentation range {A, Z, TKE} constructed as in the Point-by-Point (PbP) treatment is described. The good agreement of different prompt emission quantities obtained from this modelling (e.g. ν(A), ν(TKE), Eγ(A), Eγ(TKE), etc.) with the experimental data and the results of the PbP model and other Monte-Carlo models validates the present modelling of sequential emission. The distributions of different residual quantities, including the residual temperature distributions P(T) of light and heavy fragments allow to obtain a new parameterisation of P(T) which can be used in the PbP model and the Los Alamos model.

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Section: Discussionsupporting

confidence: 79%

“…Both distributions, of the residual temperature and the residual energy, are in good agreement with the results of Terrell [11] (blue lines). The average values of the residual temperature (given in each frame of Fig.…”

Section: T Ke)(< ε > (A Z T Ke) + S N(a Z T Ke))supporting

confidence: 78%

Parameterisation of the residual temperature distribution based on the modelling of successive emission of prompt neutrons

Tudora

Hambsch

2018

EPJ Web Conf.

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“…The main properties of the fission neutrons (their multiplicity and their angular and energy distributions) have been initially measured in the frame of the Manhattan project [1,2] and then remeasured in the 50's [3,4]. These properties are: 1) an almost Maxwellian distribution of the fission neutron energies and 2) an angular distribution with respect to the light fragment direction asymmetricaly peaked at 0 • and 180 • (i.e., ν(0 • )/ν(180 • ) > 1).…”

Section: How Was the Evaporation Hypothesis Bornmentioning

confidence: 99%

Parallel theoretical study of the two components of the prompt fission neutrons: Dynamically released at scission and evaporated from fully accelerated fragments

2017

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Abstract. Prompt fission neutrons (PFN) angular and energy distributions for the reaction 235 U(n th , f ) are calculated as a function of the mass asymmetry of the fission fragments using two extreme assumptions: 1) PFN are released during the neck rupture due to the diabatic coupling between the neutron degree of freedom and the rapidly changing neutron-nucleus potential. These unbound neutrons are faster than the separation of the nascent fragments and most of them leave the fissioning system in few 10 −21 sec. i.e., at the begining of the acceleration phase. Surrounding the fissioning nucleus by a sphere one can calculate the radial component of the neutron current density. Its time integral gives the angular distribution with respect to the fission axis. The average energy of each emitted neutron is also calculated using the unbound part of each neutron wave packet. The distribution of these average energies gives the general trends of the PFN spectrum: the slope, the range and the average value. 2) PFN are evaporated from fully accelerated, fully equilibrated fission fragments. To follow the de-excitation of these fragments via neutron and γ -ray sequential emissions, a Monte Carlo sampling of the initial conditions and a Hauser-Feshbach statistical approach is used. Recording at each step the emission probability, the energy and the angle of each evaporated neutron one can construct the PFN energy and the PFN angular distribution in the laboratory system. The predictions of these two methods are finally compared with recent experimental results obtained for a given fragment mass ratio. How was the evaporation hypothesis bornThe main properties of the fission neutrons (their multiplicity and their angular and energy distributions) have been initially measured in the frame of the Manhattan project [1, 2] and then remeasured in the 50's [3,4]. These properties are: 1) an almost Maxwellian distribution of the fission neutron energies and 2) an angular distribution with respect to the light fragment direction asymmetricaly peaked at 0 • and 180The simplest explanation of these two features was immediately embraced: the fission neutrons are evaporated from moving fission fragments (this was the terminology at that time). The fact that Weisskopf's nuclear evaporation theory [5] existed certainly helped. Strange enough nobody has revendicated this explanation. Nowadays it is reffered as "Los Alamos" or "Madland-Nix" model although this work [6] was published 30 years later. a e-mail: carjan@theory.nipne.roIn the wake of this revelation the neutron spectra were fitted with Maxwellian and Watt distributions and, as a bonus, information about the nuclear temperature of the fission fragments was extracted. The asymmetry of the angular distribution with respect to 90 • could not be simply explained by unequal fragment velocities (v L > v H ). An extra parameter was added and fitted to the experimental curve. As a result it was concluded that the light fragment must emit, on the average, about 30% more neutrons than t...

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“…Table 4. Neutron yields due to 13 C(α,n) 16 Table 5 presents earlier values not updated in a longtime of the neutron yield per 10 6 α-particle in the materials given by the experiments [21,22] and presentday ones by the NEDIS code which assumes secular equilibrium in the decay chains of 238 U and 232 Th. The results of calculation presented in the Table 5 are in satisfactory agreement with the measurements may be used to compare and benchmark new codes to estimate uncertainty of the (α,n) neutron yield calculations for a number of materials that are used and will be used for construction of dark matter detectors [14].…”

Section: Energy Of Neutrons Mevmentioning

confidence: 99%

“…The parameter a (temperature) deals with the neutron multiplicity by the Terrell formula [16] (12) or <E>=1,5a+0,25a 2 b…”

Section: Icrs-13 and Rpsd-2016 7033mentioning

confidence: 99%

Calculation of Neutron Production Rates and Spectra from Compounds of Actinides and Light Elements

Vlaskin¹,

Khomiakov²

2017

EPJ Web Conf.

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Fission Neutron Spectra and Nuclear Temperatures

Cited by 247 publications

References 36 publications

Parameterisation of the residual temperature distribution based on the modelling of successive emission of prompt neutrons

Parameterisation of the residual temperature distribution based on the modelling of successive emission of prompt neutrons

Parallel theoretical study of the two components of the prompt fission neutrons: Dynamically released at scission and evaporated from fully accelerated fragments

Calculation of Neutron Production Rates and Spectra from Compounds of Actinides and Light Elements

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