Determination of the ${}^{209}\mathrm{Bi}(n,\gamma ){}^{210g}\mathrm{Bi}$ cross section using the NICE detector

The capture cross section of ${}^{209}\mathrm{Bi}(n,\gamma ){}^{210g}\mathrm{Bi}$ was measured at different astrophysically relevant 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 $\left({\sigma }_g\right)$ was determined using the activation technique and by measuring the ${}^{210}\mathrm{Po}$ activity. The newly developed and tested NICE detector setup was used to measure the $\alpha$ activity of the ${}^{210}\mathrm{Po}$. 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.

Figure 1

$s$ process near the termination point.

Figure 2

(a) Schematic design represents the NICE detector components and the expected neutron beam direction. The dimensions of the scintillator foil are $26\times 7{\mathrm{cm}}^2$ and the PMTs have a diameter of 6.0 cm. (b) The NICE detector and the PMTs supporting structure.

Figure 3

(a) Pulse height distribution of ${}^{241}\mathrm{Am}$ source obtained via PMT1 and PMT2. The different peak position is due to the different total gain. (b) Pulse height distribution after applying time-coincidence condition.

Figure 4

The folded simulated $\gamma$ spectrum compared to the calibrated experimental spectrum. (a) ${}^{137}\mathrm{Cs}$, (b) ${}^{54}\mathrm{Mn}$, and (c) ${}^{133}\mathrm{Ba}$. The energy is given in terms of keV electron equivalent.

Figure 5

The $\alpha$ peak obtained using the NICE detector for the activated bismuth samples, both spectra obtained on day 77 after the activation and for 24 h. (a) Activation without Cd filter, (b) activation with Cd filter.

Figure 6

Schematic design represent the sample, gold foils, and the Li-glass detector arrangement in front of the neutron beam (not to scale).

Figure 7

The peak obtained using the NICE detector ($C_{\alpha }$ and background) for the activated Bi sample in comparison to the ambient background spectrum. The measurement started 55 days after the end of the activation for one day.

Figure 8

The total number of counts behavior over time. Each point presents one measurement of 6 hours and is placed at the middle of each measurement. The error bars represent the statistical uncertainty of each measurement.