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Register a new userDetermination of the $^{209}$Bi(n,$gamma$)$^{210g}$Bi cross section using the NICE-Detector
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The capture cross section of $^{209}$Bi(n,$gamma$)$^{210g}$Bi was measured at different astrophysically energies including thermal capture cross section (25 meV), resonance integral, and the Maxwellian averaged cross section at a thermal energy of $kT$ = 30 keV. The partial capture cross section ($sigma_g$) was determined using the activation technique and by measuring the $^{210}$Po activity. The newly developed and tested NICE detector setup was used to measure the $alpha$-activity of the $^{210}$Po. Using this setup the thermal and resonance integral cross sections were determined to be $16.2;pm;0.97$~mb and $89.81;pm;8.0$~mb, respectively. And the Maxwellian average cross section was measured to be $2.01;pm;0.38$~mb.
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The cross section of the $^{23}$Na($n, gamma$)$^{24}$Na reaction has been measured via the activation method at the Karlsruhe 3.7 MV Van de Graaff accelerator. NaCl samples were exposed to quasistellar neutron spectra at $kT=5.1$ and 25 keV produced via the $^{18}$O($p, n$)$^{18}$F and $^{7}$Li($p, n$)$^{7}$Be reactions, respectively. The derived capture cross sections $langlesigmarangle_{rm kT=5 keV}=9.1pm0.3$ mb and $langlesigmarangle_{rm kT=25 keV}=2.03 pm 0.05$ mb are significantly lower than reported in literature. These results were used to substantially revise the radiative width of the first $^{23}$Na resonance and to establish an improved set of Maxwellian average cross sections. The implications of the lower capture cross section for current models of $s$-process nucleosynthesis are discussed.
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In a neutron lifetime measurement at the Japan Proton Accelerator Complex, the neutron lifetime is calculated by the neutron decay rate and the incident neutron flux. The flux is obtained due to 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 suggested to use the ${}^{14}{rm N}({rm n},{rm p}){}^{14}{rm C}$ reaction as a reference because this reaction involves similar kinetic energy as the ${}^{3}{rm He}({rm n},{rm p}){}^{3}{rm H}$ 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 ${}^{14}{rm N}({rm n},{rm p}){}^{14}{rm C}$ reaction at a neutron velocity of 2200 m/s, measured relative to the ${}^{3}{rm He}({rm n},{rm p}){}^{3}{rm H}$ reaction. The result was 1.868 $pm$ 0.003 (stat.) $pm$ 0.006 (sys.) b. Additionally, the cross section of the ${}^{17}{rm O}({rm n},{rm alpha}){}^{14}{rm C}$ reaction at the neutron velocity is also redetermined as 249 $pm$ 6 mb.
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