21-29 July 2022
US/Pacific timezone

Measurement of the $^{235}$U(n,f) cross section relative to the $^{10}$B(n,α) reaction with Micromegas detectors at the CERN n_TOF facility: first results

26 Jul 2022, 11:51
Folsom ()



Veatriki Michalopoulou the n_TOF Collaboration


Neutron induced reaction cross section measurements are often performed relative to a neutron cross-section standard. Thus, the accuracy of the neutron standards determines the accuracy of the neutron cross section measurements. The $^{235}$U(n,f) cross section is widely used as reference reaction, while it is considered as standard at 0.0253 eV (thermal energy), between 7.8 and 11 eV and from 0.15 to 200 MeV [1].

Moreover, it is a very important reaction for neutronic calculations of nuclear reactors and has been the subject of many experimental and theoretical works. Nevertheless, certain issues with the cross section of this reaction have been pointed out, especially in the energy region below 100 keV (e.g. [2] - [4] etc).

For this reason, high accuracy and high resolution cross section data for the $^{235}$U(n,f) reaction are needed to improve the accuracy of this reaction cross section and to extend the energy range of the Resolved Resonances Region above 2.5 keV.
In this context, the $^{235}$U(n,f) reaction cross has been measured relative to the standard $^{10}$B(n,α) cross section within the n_TOF collaboration, with an independent experimental setup from the previous measurement of Amaducci et al. [4] in n_TOF. The measurement was carried out in experimental area EAR-1 of the n_TOF facility at CERN, with the aim to cover the widest energy range possible. The high purity targets were produced at JRC-Geel in Belgium, while the experimental setup was based on Micromegas detectors.
The preliminary results from this work will be presented and discussed.

[1] A.D.Carlson et al., Nucl. Data Sheets 148 (2018) 143
[2] M. Barbagallo et al., Eur. Phys. J. A 49 (2013) 156
[3] M. Jandel et al., Phys. Rev. Lett. 109 (2012) 202506
[4] S. Amaducci et al., Eur. Phys. J. A 55 (2019) 120

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