Figure 1

TOF spectrum taken by bombarding enriched ${}^{12}\mathrm{C}$ targets by a NaI(Tl) detector at $E_{\alpha ,\mathrm{lab}.}=2.27$ MeV ($E_{\mathrm{c}.\mathrm{m}.}=1.60$ MeV). The detected events are shown as a function of the time relative to the time ($t=0$ ns) for the events at the target position. The events at the high peak (a) are due to the ${}^{127}\mathrm{I}$($n,n^{\text{'}}\gamma$)${}^{127}\mathrm{I}$ and ${}^{127}\mathrm{I}$($n,\gamma$)${}^{128}\mathrm{I}$ reactions in the NaI(Tl) detector. The events at the low peak (b) are due to the ${}^{27}\mathrm{Al}$($n,n^{\text{'}}\gamma$)${}^{27}\mathrm{Al}$ and Pb$(n,n^{\text{'}}\gamma )$Pb reactions. The events at the narrow peak (c) are obtained by putting the γ-ray energy gate at $8<E_{\gamma }<9$ MeV.Reuse & Permissions

Figure 2

(a) γ-ray spectrum taken by a NaI(Tl) detector by bombarding enriched ${}^{12}\mathrm{C}$ targets at $E_{\alpha ,\mathrm{lab}.}=2.27$ MeV. The sharp peak at 6.8 MeV was due to the thermal neutron capture reaction by ${}^{127}\mathrm{I}$. The spectra in (b) was obtained by gating the high peak (a) of the TOF spectrum in Fig. 1, and the foreground and background spectra in (c) were obtained by gating the narrow peak at $-6<t<2$ ns and at $-40<t<7$ ns, respectively, of the TOF spectrum in Fig. 1. In the spectrum in (b) continuum γ rays up to 4 and 11 MeV are due to the ${}^{127}\mathrm{I}$($n,n^{\text{'}}\gamma$)${}^{127}\mathrm{I}$ and ${}^{127}\mathrm{I}$($n,\gamma$)${}^{128}\mathrm{I}$ reactions, respectively. In the foreground spectrum (solid line) (c) the γ ray from the ${}^{12}\mathrm{C}$($\alpha ,\gamma$)${}^{16}\mathrm{O}$ reaction is clearly observed at 8.8 MeV. We also observed the 3.69-, 3.85-, and 4.45-MeV γ rays from the $(\alpha ,p\gamma )$ and $(\alpha ,n\gamma )$ reactions by ${}^{10}\mathrm{B}$ and ${}^9\mathrm{Be}$, respectively, which were contained in either enriched ${}^{12}\mathrm{C}$ targets and/or a gold backing.Reuse & Permissions

Figure 3

γ-ray spectrum of the ${}^{12}\mathrm{C}$($\alpha ,\gamma$)${}^{16}\mathrm{O}$ reaction measured by a Ge detector. The spectra in (a) and (b) were measured at 40° with respect to the α-beam direction at $E_{\mathrm{c}.\mathrm{m}.}=2.68$ and 2.26 MeV, respectively [7]. The spectra in (c) were measured at six angles at $E_{\mathrm{c}.\mathrm{m}.}=1.78$ MeV [8]. In the spectra in (a) and (b), the primary transitions as well as secondary transitions from the ${}^{12}\mathrm{C}$($\alpha ,\gamma$)${}^{16}\mathrm{O}$ reaction are clearly observed. In addition, the 596-, 692-, 834-, 1039-, and 1215-keV γ rays from the Ge$(n,n^{\text{'}}\gamma )$Ge reaction are observed. In the spectrum in (b), a continuum spectrum up to about 4.7 MeV is considered to be due to the Ge$(n,n^{\text{'}}\gamma )$Ge reaction occurring in a Ge detector. In the spectrum in (c), a wide peak was observed at around 7.1 MeV (channel ∼ 650) in the ${28}^{°}$ spectrum, which is considered to be due to the ${}^{70}\mathrm{Ge}$($n,p$)${}^{70}\mathrm{Ga}$ reaction occurring in a Ge detector.Reuse & Permissions

Figure 4

Calculated spectrum of the neutron-induced reactions by 4-MeV neutrons on Ge occurring within a Ge detector. The 596-, 834-, and 1039-keV γ-ray peaks and continuum γ rays up to 4 MeV are due to the Ge$(n,n^{\text{'}}\gamma )$Ge reaction, and a continuum γ ray up to 9.7 MeV is due to the Ge$(n,\gamma )$Ge reaction. Sharp peaks at about 7.0 and 7.9 MeV are due to α rays from the ${}^{70}\mathrm{Ge}$($n,\alpha$)${}^{67}\mathrm{Zn}$ and ${}^{73}\mathrm{Ge}$($n,\alpha$)${}^{70}\mathrm{Zn}$ reactions to the ground states in ${}^{67}\mathrm{Zn}$ and ${}^{70}\mathrm{Zn}$, respectively. A broad peak at 5.6 MeV is considered to be due to α particles from the ${}^{70}\mathrm{Ge}$($n,\alpha$)${}^{67}\mathrm{Zn}$ reaction to excited states in ${}^{67}\mathrm{Zn}$.Reuse & Permissions

Figure 5

The calculated ratio of the cross section of the ${}^{13}\mathrm{C}$($\alpha ,n$)${}^{16}\mathrm{O}$ [18] (a) and ${}^9\mathrm{Be}$($\alpha ,n$)${}^{12}\mathrm{C}$ [19] (b) reactions to the $E1$ cross section of the ${}^{12}\mathrm{C}$($\alpha ,\gamma$)${}^{16}\mathrm{O}$ reaction [23], $\sigma$(${}^{13}\mathrm{C}$($\alpha ,n$)${}^{16}\mathrm{O}$)$/\sigma$(${}^{12}\mathrm{C}$($\alpha ,\gamma$)${}^{16}\mathrm{O}$) and $\sigma$(${}^9\mathrm{Be}$($\alpha ,n$)${}^{12}\mathrm{C}$)$/\sigma$(${}^{12}\mathrm{C}$($\alpha ,\gamma$)${}^{16}\mathrm{O}$), given as a function of the α-beam energy in the laboratory system, $E_{\alpha ,\mathrm{lab}.}$. The ratios increase significantly at $E_{\alpha ,\mathrm{lab}.}<$ 3 MeV. The ratio for ${}^{13}\mathrm{C}$($\alpha ,n$)${}^{16}\mathrm{O}$ shows a resonance-like structure at $E_{\alpha ,\mathrm{lab}.}\approx$ 1.05, 1.34, and 1.59 MeV, and that for ${}^9\mathrm{Be}$($\alpha ,n$)${}^{12}\mathrm{C}$ increases steeply at $E_{\alpha ,\mathrm{lab}.}<$ 1 MeV.Reuse & Permissions