Experimental and evaluated photoneutron cross sections for ${}^{197}\mathrm{Au}$

There is a serious well-known problem of noticeable disagreements between the partial photoneutron cross sections obtained in various experiments. Such data were mainly determined using quasimonoenergetic annihilation photon beams and the method of neutron multiplicity sorting at Lawrence Livermore National Laboratory (USA) and Centre d’Etudes Nucleaires of Saclay (France). The analysis of experimental cross sections employing new objective physical data reliability criteria has shown that many of those are not reliable. The IAEA Coordinated Research Project (CRP) on photonuclear data evaluation was approved. The experimental and previously evaluated cross sections of the partial photoneutron reactions $(\gamma ,1n)$ and $(\gamma ,2n)$ on ${}^{197}\mathrm{Au}$ were analyzed using the new data reliability criteria. The data evaluated using the new experimental-theoretical method noticeably differ from both experimental data and data previously evaluated using nuclear modeling codes gnash, gunf, alice-f, and others. These discrepancies needed to be resolved.

Figure 1

(a) $F_1^{\exp }$ and (b) $F_2^{\exp }$ data obtained for ${}^{197}\mathrm{Au}$ using experimental data of Livermore ([19]: triangles) and Saclay ([20]: squares) in comparison with results of $F_{1,2}^{\mathrm{theor}}$ calculated in the model ([25, 26]: lines).

Figure 2

(a) ${}^{197}\mathrm{Au}\left(\gamma ,1n\right)$ reaction, (b)${}^{197}\mathrm{Au}(\gamma ,2n)$ reaction. Comparison of experimental (Livermore [19]: triangles; Saclay [20]: squares) and evaluated ([14]: circles; [13]: dotted line) data.

Figure 3

(a) Differences (4) among the newly evaluated [14] and the experimental reaction cross sections obtained at Livermore [19]; (b) analogous differences (4) for data obtained at Saclay [20] [($\gamma ,1n$): squares; ($\gamma ,2n$): triangles].

Figure 4

Comparison of experimental data ([19]: triangles; [20]: squares; [22]: dot-dash line; [28]: solid line; [29]: dotted line; [31]: crosses; [32]: open circles) with evaluated cross section ([14]: circles) for the ${}^{197}\mathrm{Au}\left(\gamma ,1n\right)$ reaction.

Figure 5

Comparison of experimental data ([19]: triangles; [20]: squares; [28]: solid line) with evaluated cross section ([14]: circles) for the ${}^{197}\mathrm{Au}\left(\gamma ,2n\right)$ reaction.