A study of the construction of the correlation matrix of <sup>241</sup>Pu(nth,f) isobaric fission yields

Julien-Laferrière, S.; Chebboubi, A.; Kessedjian, G.; Sérot, O.

doi:10.1051/epjn/2018036

Cited by 6 publications

(5 citation statements)

References 17 publications

(18 reference statements)

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“…Also, a χ 2 test is performed with a confidence level of 99.7% (corresponding to 3σ ). If the test is not satisfactory, additional independent uncertainty is added to the diagonal elements of the covariance matrix C [34] until the test is satisfied. This additional uncertainty can be seen as the dispersion of the measurements and highlights the limits of this process.…”

Section: Towards a New Measurement Methodologymentioning

confidence: 99%

Measurements of $$^{233}$$U$$(\text {n}_{\text {th}},\text {f})$$ fission product mass yields with the LOHENGRIN recoil mass spectrometer

et al. 2021

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Numerous measurements of fission product yields were performed since the discovery of the nuclear fission process. However, more precise and reliable fission product yields are requested. Lack of covariance matrices make difficult to use it for specific application purposes such as the propagation uncertainty of decay heat. In this work, we propose to measure independently the fission product mass yields for the whole heavy peak (including the symmetric mass region) for the 233 U(n th , f) reaction. Both average values and experimental covariance is provided. The fission product mass yields are measured with the LOHEN-GRIN recoil mass spectrometer of the ILL using an ionization chamber located at the focal plane. A new procedure of data taking has been developed in order to minimize the biases. Concretely several ionic charges and kinetic energy distributions have been measured for each mass. Particular attention has been considered in the monitoring of the target time evolution. Additional corrections were necessary in the symmetry mass region due to contaminants coming from the LOHENGRIN recoil mass spectrometer. A complex Monte Carlo analysis has been developed in order to better propagate all the uncertainties. The fission product mass yields of the 233 U(n th , f) and its associated covariance matrix has been produced. An overall good agreement has been observed with ENDF/B-VIII.0 in contrast with the JEFF-3.3 evaluation. A precision around 2% for the heavy peak has been measured. The experimental covariance matrix was also computed. In the symmetry mass region, two components were observed in the kinetic energy distribution. One of this component was considered as an artifact and was ruled-out.

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Section: Towards a New Measurement Methodologymentioning

confidence: 99%

Measurements of $$^{233}$$U$$(\text {n}_{\text {th}},\text {f})$$ fission product mass yields with the LOHENGRIN recoil mass spectrometer

et al. 2021

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“…A new measurement method and consequent analysis path have been developed and are detailed in Ref. [2][3][4]. Among the special features of this method are the self-normalisation of our data.…”

Section: U(n Th F) Independent Mass Yieldsmentioning

confidence: 99%

New measurement of the ²³⁵U(n_th,f) fission yields and development of a Time of Flight line at the LOHENGRIN spectrometer

et al. 2023

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The study of nuclear fission yields has a major impact on the characterization and understanding of the fission process and is mandatory for reactor applications. In the framework of a collaboration between the CEA, the LPSC and the ILL, a program of actinide fission yield measurements has been ongoing for several years at the LOHENGRIN spectrometer. However, the measurement of very low fission yields in the symmetry region and the heavy wing of the distributions is difficult to achieve due to the strong contamination by other masses with much higher yields and requires the development of a new experimental setup. This paper will first present the results of a new absolute measurement of the 235U(nth,f) mass yields using an ionization chamber placed at the exit of the spectrometer. Although very well documented in the literature, these yields show uncertainties lying from 3% to 10% with large discrepancies between libraries and a lack of correlation matrices. New experimental data obtained at the LOHENGRIN spectrometer will be detailed, along with the measurement method and the production of the experimental covariance matrix. The second part will show the development of a Time of Flight (ToF) line in order to improve the background rejection in the mass yield measurements. In the symmetry region, the precision of the measurement is limited by the background estimation due to the charge exchanges with the residual gas of the separator. We plan to analyze the events using a triple coincidence (∆E x E) x ToF, whereas today only (∆E x E) selection is available. The new ToF line is built using Si3N4 foils and secondary electron detectors (SED) for the start and stop detectors. We will present the choices made for the SED technology along with the progress achieved on the ToF line characterization.

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“…The χ 2 test is used to verify whether a 90% level of confidence is achieved. If not, progressively, uncertainty is added [15] and the N d is recalculated to achieve the test criteria. Thus, a final mean value of the N d along with its uncertainty is obtained.…”

Section: The Analysismentioning

confidence: 99%

Investigation of fission product isomeric ratios and angular momenta of ¹³²Sn populated in the ²⁴¹Pu(n_th,f) reaction

et al. 2021

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During an experimental campaign performed at the LOHENGRIN recoil spectrometer of the Institut Laue-Langevin (ILL), a kinetic energy dependence of 132Sn fission product isomeric ratio (IR) has been measured by inducing thermal fission of 241Pu. The IRs are deduced using gamma ray spectrometry in coincidence with the ionisation chamber. To interpret these data, we use the FIFRELIN Monte-Carlo code to simulate the de-excitation of the fission fragments. Combining the IRs with the FIFRELIN calculations, the angular momentum distribution with kinetic energy of the doubly magic nucleus of 132Sn was deduced. This will be compared with the angular momentum distribution obtained for the reaction 235U(nth,f) for 132Sn.

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A study of the construction of the correlation matrix of ²⁴¹Pu(nth,f) isobaric fission yields

Cited by 6 publications

References 17 publications

Measurements of $$^{233}$$U$$(\text {n}_{\text {th}},\text {f})$$ fission product mass yields with the LOHENGRIN recoil mass spectrometer

Measurements of $$^{233}$$U$$(\text {n}_{\text {th}},\text {f})$$ fission product mass yields with the LOHENGRIN recoil mass spectrometer

New measurement of the ²³⁵U(n_th,f) fission yields and development of a Time of Flight line at the LOHENGRIN spectrometer

Investigation of fission product isomeric ratios and angular momenta of ¹³²Sn populated in the ²⁴¹Pu(n_th,f) reaction

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A study of the construction of the correlation matrix of 241Pu(nth,f) isobaric fission yields

Cited by 6 publications

References 17 publications

Measurements of $$^{233}$$U$$(\text {n}_{\text {th}},\text {f})$$ fission product mass yields with the LOHENGRIN recoil mass spectrometer

Measurements of $$^{233}$$U$$(\text {n}_{\text {th}},\text {f})$$ fission product mass yields with the LOHENGRIN recoil mass spectrometer

New measurement of the 235U(nth,f) fission yields and development of a Time of Flight line at the LOHENGRIN spectrometer

Investigation of fission product isomeric ratios and angular momenta of 132Sn populated in the 241Pu(nth,f) reaction

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A study of the construction of the correlation matrix of ²⁴¹Pu(nth,f) isobaric fission yields

New measurement of the ²³⁵U(n_th,f) fission yields and development of a Time of Flight line at the LOHENGRIN spectrometer

Investigation of fission product isomeric ratios and angular momenta of ¹³²Sn populated in the ²⁴¹Pu(n_th,f) reaction