A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculatio...A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculation and validation of the response matrix, are presented. The PFNS for ^235U in the energy range 1–12 MeV, induced by thermal neutrons, was obtained. The measured spectrum in the low-energy region was in good agreement with previous work and the ENDF/B-VII library, except for minor differences. In the high-energy region, however, the relative height of the measured spectrum was greater, and an analysis of the experiment indicated uncertainties of 13% at 10 MeV and 24% at 12 MeV. Experimental results showed that the recoil proton method could be used to measure prompt fission neutron spectra. Some directions for future work are included.展开更多
The photoionization cross section of the ground state 2s22p 2Po1/2 and the first excited state 2s22p2po1/2 of C II ions are systematically calculated using the fully relativistic R-matrix code DARC. The detailed reson...The photoionization cross section of the ground state 2s22p 2Po1/2 and the first excited state 2s22p2po1/2 of C II ions are systematically calculated using the fully relativistic R-matrix code DARC. The detailed resonances are presented and identified for the photon energy ranging from threshold （24.38 eV） up to 41.5 eV where the L-shell （2p, 2s） photoionization process is dominant. In the calculations, the relativistic effect and electronic correlation effect are well considered. It is found that the relativistic effect is very important for the light atomic system CII, which accounts for experimentally observed fine structure resonance peaks. A careful comparison is made between the present results and the experimental values, and also other theoretical data available in the literature, showing that good agreement is obtained for the resonance peaks.展开更多
The partial and total photorecombination cross sections of the ground-state C V ion in the KLL and KLM resonant energy regions were calculated in detail by using the Dirac atomic R-matrix code based on a fully relativ...The partial and total photorecombination cross sections of the ground-state C V ion in the KLL and KLM resonant energy regions were calculated in detail by using the Dirac atomic R-matrix code based on a fully relativistic R-matrix method. Meanwhile, the principal resonant lines in each photorecombination channel have been classified according to the calculated transition energies and probabilities from the KLL and KLM resonant states to the 1s2nl（n = 2, 3 and l = s, p, d）final states. The validity of these calculations is assessed by comparison with previously published experimental and theoretical data. The good agreement between the present calculated results and those obtained using different approaches confirms the accuracy of the present results. In addition, it is found that the damping effect can be neglected for the KLL resonant, but not for the KLM resonant.展开更多
基金supported by the National Natural Science Foundation of China(No.11775196)the Chinese Special Project for ITER(No.2015GB108006)
文摘A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculation and validation of the response matrix, are presented. The PFNS for ^235U in the energy range 1–12 MeV, induced by thermal neutrons, was obtained. The measured spectrum in the low-energy region was in good agreement with previous work and the ENDF/B-VII library, except for minor differences. In the high-energy region, however, the relative height of the measured spectrum was greater, and an analysis of the experiment indicated uncertainties of 13% at 10 MeV and 24% at 12 MeV. Experimental results showed that the recoil proton method could be used to measure prompt fission neutron spectra. Some directions for future work are included.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0402300)the National Natural Science Foundation of China(Grant Nos.U1530142,11474032,and 11774344)the Young Teachers Scientific Research Ability Promotion Plan of Northwest Normal University(Grant No.NWNU-LKQN-15-3)
文摘The photoionization cross section of the ground state 2s22p 2Po1/2 and the first excited state 2s22p2po1/2 of C II ions are systematically calculated using the fully relativistic R-matrix code DARC. The detailed resonances are presented and identified for the photon energy ranging from threshold （24.38 eV） up to 41.5 eV where the L-shell （2p, 2s） photoionization process is dominant. In the calculations, the relativistic effect and electronic correlation effect are well considered. It is found that the relativistic effect is very important for the light atomic system CII, which accounts for experimentally observed fine structure resonance peaks. A careful comparison is made between the present results and the experimental values, and also other theoretical data available in the literature, showing that good agreement is obtained for the resonance peaks.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11274254,U1332206,and U1331122)the International Scientific and Technological Cooperative Project of Gansu Province,China(Grant No.1104WCGA186)
文摘The partial and total photorecombination cross sections of the ground-state C V ion in the KLL and KLM resonant energy regions were calculated in detail by using the Dirac atomic R-matrix code based on a fully relativistic R-matrix method. Meanwhile, the principal resonant lines in each photorecombination channel have been classified according to the calculated transition energies and probabilities from the KLL and KLM resonant states to the 1s2nl（n = 2, 3 and l = s, p, d）final states. The validity of these calculations is assessed by comparison with previously published experimental and theoretical data. The good agreement between the present calculated results and those obtained using different approaches confirms the accuracy of the present results. In addition, it is found that the damping effect can be neglected for the KLL resonant, but not for the KLM resonant.
