by Kitahara, R, Hirota, K, Ieki, S, Ino, T, Iwashita, Y, Kitaguchi, M, Koga, J, Mishima, K, Morishita, A, Nagakura, N, Oide, H, Otono, H, Seki, Y, Sekiba, D, Shima, T, Shimizu, H M, Sumi, N, Sumino, H, Taketani, K, Tomita, T, Yamada, T, Yamashita, S, Yokohashi, M and Yoshioka, T
Abstract:
In a neutron lifetime measurement at the Japan Proton Accelerator Complex, the neutron lifetime is calculated from the neutron decay rate and the incident neutron flux. The flux is obtained by counting the protons emitted from the neutron absorption reaction of ${}^{3}{\rm He}$ gas, which is diluted in a mixture of working gas in a detector. Hence, it is crucial to determine the amount of ${}^{3}{\rm He}$ in the mixture. In order to improve the accuracy of the number density of the ${}^{3}{\rm He}$ nuclei, we have suggested using the ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ reaction as a reference because this reaction involves similar kinetic energy to the $^3$He(n,p)$^3$H reaction and a smaller reaction cross section to introduce reasonable large partial pressure. The uncertainty of the recommended value of the cross section, however, is not satisfied with our requirement. In this paper we report the most accurate experimental value of the cross section of the $^{14}$N(n,p)$^{14}$C reaction at a neutron velocity of 2200 m s$^{-1}$, measured relative to the $^3$He(n,p)$^3$H reaction. The result was 1.868 $\pm$ 0.003 (stat.) $\pm$ 0.006 (sys.) b. Additionally, the cross section of the $^{17}$O(n,$\alpha$)$^{14}$C reaction at the neutron velocity is also redetermined as 249 $\pm$ 6 mb.
Reference:
Kitahara, R, Hirota, K, Ieki, S, Ino, T, Iwashita, Y, Kitaguchi, M, Koga, J, Mishima, K, Morishita, A, Nagakura, N, Oide, H, Otono, H, Seki, Y, Sekiba, D, Shima, T, Shimizu, H M, Sumi, N, Sumino, H, Taketani, K, Tomita, T, Yamada, T, Yamashita, S, Yokohashi, M and Yoshioka, T, "Improved accuracy in the determination of the thermal cross section of ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ for neutron lifetime measurement", Progress of Theoretical and Experimental Physics, vol. 2019, no. 9, 2019.
Bibtex Entry:
@article{Kitahara2019,
abstract = {In a neutron lifetime measurement at the Japan Proton Accelerator Complex, the neutron lifetime is calculated from the neutron decay rate and the incident neutron flux. The flux is obtained by counting the protons emitted from the neutron absorption reaction of ${}^{3}{\rm He}$ gas, which is diluted in a mixture of working gas in a detector. Hence, it is crucial to determine the amount of ${}^{3}{\rm He}$ in the mixture. In order to improve the accuracy of the number density of the ${}^{3}{\rm He}$ nuclei, we have suggested using the ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ reaction as a reference because this reaction involves similar kinetic energy to the $^3$He(n,p)$^3$H reaction and a smaller reaction cross section to introduce reasonable large partial pressure. The uncertainty of the recommended value of the cross section, however, is not satisfied with our requirement. In this paper we report the most accurate experimental value of the cross section of the $^{14}$N(n,p)$^{14}$C reaction at a neutron velocity of 2200 m s$^{-1}$, measured relative to the $^3$He(n,p)$^3$H reaction. The result was 1.868 $\pm$ 0.003 (stat.) $\pm$ 0.006 (sys.) b. Additionally, the cross section of the $^{17}$O(n,$\alpha$)$^{14}$C reaction at the neutron velocity is also redetermined as 249 $\pm$ 6 mb.},
author = {Kitahara, R and Hirota, K and Ieki, S and Ino, T and Iwashita, Y and Kitaguchi, M and Koga, J and Mishima, K and Morishita, A and Nagakura, N and Oide, H and Otono, H and Seki, Y and Sekiba, D and Shima, T and Shimizu, H M and Sumi, N and Sumino, H and Taketani, K and Tomita, T and Yamada, T and Yamashita, S and Yokohashi, M and Yoshioka, T},
doi = {10.1093/ptep/ptz096},
issn = {2050-3911},
journal = {Progress of Theoretical and Experimental Physics},
month = {sep},
number = {9},
title = {{Improved accuracy in the determination of the thermal cross section of ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ for neutron lifetime measurement}},
url = {https://academic.oup.com/ptep/article/doi/10.1093/ptep/ptz096/5570163},
volume = {2019},
year = {2019}
}