Dynamics of population of gadolinium-156 nuclei energy levels during neutron pumping of isotope-modified gadolinium oxide

摘要

The possibility of transformation of energy of fast and epithermal neutrons to energy of coherent photon radiation at the expense of a neutron pumping of the active medium formed by nucleus with long-living isomerous states is theoretically described. The channel of the nucleus formation in isomeric state as a daughter nucleus resulting from the nuclear reaction of neutron capture by a lighter nucleus is taken into consideration for the first time. The analysis of cross sections dependence of radiative neutron capture by the nuclei of gadolinium isotopes Gd~(155) and Gd~(156) is performed. As a result, it is stated that the speed of Gd~(156) nuclei formation exceeds the speed of their "burnup" in the neutron flux. It is provided by a unique combination of absorbing properties of two isotopes of gadolinium Gd~(155) and Gd~(156) in both thermal and resonance regions of neutron energy. The possibility of excess energy accumulation in the participating medium created by the nuclei of the pair of gadolinium isotopes Gd~(155) and Gd~(156) due to formation and storage of nuclei in isomeric state at radiative neutron capture by the nuclei of the stable isotope with a smaller mass is shown. It is concluded that when the active medium created by gadolinium nuclei is pumped by neutrons with the flux density of the order of 10~(13) cm~(-2)·s~(-1), the condition of levels population inversion can be achieved in a few tens of seconds. The wave length of the radiation generated by the medium is 0.0006 nm.