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Direct Determination of Ground-State Transition Widths and Natural Level Widths with the Method of Relative Self Absorption
摘要： The method of relative self absorption is based on the technique of nuclear resonance ?uorescence measurements. It allows for a model-independent determination of ground-state transition widths, natural level widths, and, consequently, of branching ratios to the ground state for individual excitations. Relative self-absorption experiments have been performed on the nuclei 6Li and 140Ce. In order to investigate the total level width for the 0+1 , T = 1 level at 3563 keV in 6Li, a high-precision self-absorption measurement has been performed. In the case of 140Ce, self absorption has been applied for the ?rst time to study decay widths of dipole-excited states in the energy regime of the pygmy dipole resonance.
关键词： 6Li,natural level widths,nuclear resonance fluorescence,ground-state transition widths,140Ce,branching ratios,relative self absorption,pygmy dipole resonance
更新于2025-09-23 15:21:21
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Testing requirements for active interrogation systems
摘要： The role of active-interrogation systems for nuclear security is to detect the presence of special nuclear material inside an object by observing the radiation emitted by that object when it has been exposed to known sources of external radiation. Because of the cost, complexity, and the need to avoid irradiating occupants, active-interrogation systems are intended for cargo applications where shielding can prevent detection by passive radiation detection systems. To ensure that active-interrogation systems for detection of special nuclear material are designed and tested to a consistent level of performance, technical standards are needed for evaluating such systems. This paper addresses the testing standards needed for active-interrogation systems to detect high atomic number materials, fissionable materials, and specific special nuclear materials. Because the use of special nuclear material for a testing standard is not practical, this work focuses on the determination of materials that could be used as surrogates in that they provide a similar response as targets of special nuclear materials. The results of this paper, determined through analytic calculations and radiation transport modeling, are based upon scenarios constructed and applied to specific active-interrogation modalities.
关键词： High-Z,Nuclear resonance fluorescence,Active interrogation,Differential die-away,Photofission
更新于2025-09-19 17:15:36