MEASUREMENT OF HIGH-ENERGY NEUTRON SPECTRA WITH A BONNER SPHERE EXTENSION SYSTEM
MEASUREMENT OF HIGH-ENERGY NEUTRON SPECTRA WITH A BONNER SPHERE EXTENSION SYSTEM
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DOI：
10.13182/nt09-a9204
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发表时间：
2009-11-01
影响因子：
1.5
通讯作者：
Salehpour, Mohammad
中科院分区：
文献类型：
--
作者：
Howell, Rebecca M.;Burgett, Eric;Salehpour, Mohammad
在20 MeV以上，邦纳球谱仪（BSS）的标准球在形状和灵敏度方面都具有类似的响应。标准集的响应也表现出强烈的灵敏度下降超过20兆电子伏。在目前的工作中，蒙特卡罗N粒子扩展（MCNPX）代码被用来研究不同的设计修改，以增加高能量中子响应的BSS。成本效益的系统扩展了现有的，商业上可用的BSS系统的设计，通过添加铜，钨，铅的同心壳。这些壳与现有球体以各种组合使用。该设计被称为邦纳球扩展（BSE），结合了被动和主动探测技术，包括激活箔和标准（LiI）-Li-6（Eu）闪烁体。MCNPX中的详细模型用于创建从热到1000 MeV的精细群中子响应。在洛斯阿拉莫斯中子科学中心使用BSE进行测量，并使用MXD-FC 33代码和计算的BSE响应矩阵展开数据。所得到的光谱表明，BSE系统提供了改进的测量中的中子谱的能量区域高于20 MeV的标准邦纳球系统相比。BSE系统将系统的灵敏度扩展到能量的十倍以上，同时保持几乎各向同性的角响应。
Above 20 MeV the standard spheres of a Bonner sphere spectrometer (BSS) have similar responses, both in shape and sensitivity. The responses of the standard set also exhibit strongly diminishing sensitivities above 20 MeV. In the current work the Monte Carlo N-Particle eXtended (MCNPX) code was used to investigate different design modifications to increase the high-energy neutron response of a BSS. The cost-effective system expands upon the design of an existing, commercially available BSS system by adding concentric shells of copper, tungsten, and lead. These shells are used in various combinations with the existing spheres. The design, referred to as the Bonner sphere extension (BSE), incorporates both passive and active detection techniques including activation foils and the standard (LiI)-Li-6(Eu) scintillator. Detailed models in MCNPX were used to create fine-group neutron responses from thermal to 1000 MeV. Measurements were performed with the BSE at Los Alamos Neutron Science Center, and the data were unfolded using the MXD-FC33 code and the calculated BSE response matrix. The resulting spectrum demonstrated the BSE system provided improvement in the measurement of the neutron spectra in the energy regions above 20 MeV when compared to the standard Bonner sphere system. The BSE system extends the sensitivity of the system to more than ten decades in energy while maintaining a nearly isotropic angular response.