21-29 July 2022
US/Pacific timezone

(WITHDRAWN) $^{16}$O(n,$\alpha_0$)$^{13}$C Cross Section Normalization based on a new Time-of-Flight measurement using a Frisch Grid Ionisation Chamber.

Not scheduled
Folsom ()



Sebastian Urlass


The $^{16}$O(n,$\alpha$)$^{13}$C reaction plays an important role in nuclear technology [1,2]. Oxygen is a major component of the fuel and in the water coolant of nuclear power reactors. This reaction influences criticality through the removal of neutrons and produces helium in the fuel which may lead to swelling.
A new reaction cross section measurement was carried out at the time-of-flight facility GELINA using a Frisch-gridded ionization chamber. Between the reaction threshold (2.355 MeV) and a neutron energy of 9 MeV, $^{16}$O(n,$\alpha_0$)$^{13}$C events on the CO$_2$ admixture in the counting gas could be well identified. The $^{16}$O(n,$\alpha_0$)$^{13}$C cross section was determined relative to the neutron-induced fission cross section standard of $^{235}$U using the H19 fission chamber of PTB and has been compared to recent evaluations. Special care was taken to quantify all sources of systematic uncertainties based on measurements. The integral over the data from 4.0 to 5.3 MeV allows the normalization of evaluated $^{16}$O(n,$\alpha_0$)$^{13}$C reaction cross sections and data in the literature to about 6 % uncertainty.
The new cross section normalization is compared with results deduced from thin target measurements of the inverse reaction $^{13}$C($\alpha$,n)$^{16}$O from [3,4] and from measured thick target yields. An alternative normalization for the evaluated cross sections and data in the literature, based on the $^{13}$C($\alpha$,n$_0$)$^{16}$O thick target yield data of West and Sherwood [5] is also presented and has an uncertainty of 8 %. The data by West and Sherwood, used for this normalization are supported by two additional mutually consistent independent thick-target yield measurements. The two sets of normalization factors agree within 3 %.

[1] OECD NEA High Priority Request List. https://www.oecd-nea.org/jcms/c_12806
[2] M. T. Pigni and S. Croft. Phys. Rev. C 102, 014618 (2020).
[3] J. K. Bair and F. X. Haas. Phys. Rev. C 7, 1356 (1973)
[4] S. Harissopulos et al. Phys. Rev. C 72, 062801 (2005).
[5] D. West and A.C. Sherwood. Annals of Nuclear Energy 9, 551-577 (1982).

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