Prompt neutrons in correlation with fission fragments from U235(n,f)

Abstract

Improved knowledge of prompt emission in fission has significant implications for our understanding of the fission process. It is also important for improving nuclear data evaluation, with impact on applications. The correlation between prompt neutrons and fragments emitted in binary neutron induced fission of 235 U has been studied at the GELINA facility. The experiment employs an array of proton recoil scintillators and a position-sensitive twin ionization chamber. This experimental arrangement permits measurement of the correlations between neutron emission, fragment angle, and mass and energy of the fission fragments. In this article, we present results on prompt fission neutron energy and multiplicity correlations with mass and total kinetic energy of the fission fragments. Results from the present measurement shows distinct differences compared to earlier studies of the correlated fission fragment and prompt neutron emission quantities. The differences with respect to earlier investigations are interpreted as improved fission fragment energy resolution in the present measurement. The present result supports several recent model calculations of prompt neutron and fission fragment correlations.

Systematic behaviours of different quantities related to sequential prompt emission in fission

“…Fig.3 shows the centre-of-mass energy spectrum Φ k (ε) of the first three neutrons (plotted with different dashed and dotted lines) successively emitted from the light and heavy fragment (upper and lower part, respectively) calculated according to Eq. (5), as well as the total centre-of-mass energy spectrum (solid red line) which describes very well the experimental data recently measured by Göök et al [5].…”

“…Prompt neutron spectra in the centre-of-mass frame corresponding to the light and heavy fragment group (upper and lower part, respectively): The result of the LA model with sequential emission: Φ k (ε) of the first three emitted neutrons (different dashed and dotted lines) and the total Φ(ε) (red solid line) describing very well the experimental data of Göök et al[5] (symbols).…”

Identifying Inconsistencies in Fission Product Yield Evaluations with Prompt Neutron Emission

“…We also note that our fit of the remaining parameters in CGMF to prompt neutron observables results in good agreement with the experimental data [24,28,30]. The experimentalν(A) is often provided as a function of the primary fragment [24,28,30] (points) and as calculated directly by the CGMF code (red). We use the IFY from CGMF to derive theνT (A) through the average charge conservation (blue), which reproduces the directνT (A) with good agreement.…”

Calculation of the fission observables in the resolved resonance energy region of the 235U(n,f) reaction

“…The recent experiment performed by Göök et al [6][7][8][9] on the GELINA (GEel LINear Accelerator) facility of the JRC-Geel (Belgium) consisted in measuring fission fragments in coincidence with prompt neutrons. For that, a position-sensitive twin ionization chamber was operated to determine kinetic energy and mass of the fission fragments [16].…”

“…2, such * e-mail: olivier.serot@cea.fr fluctuations were experimentally observed not only for the average prompt neutron multiplicity but also for other fission observables (average total kinetic energy of the fission fragments, emission probability of ternary-α particles,...). The recent experiment performed by the JRC-Geel (Belgium) [6][7][8][9] is certainly the most accomplished one. Indeed, for the first time, they were able to measure (for 88 resonances) correlations between fission fragments properties (mass and kinetic energy) and prompt neutron multiplicity.…”