超冷中子在聚乙烯和钒中的上散射和吸收测量
Measurements of ultracold neutron upscattering and absorption in polyethylene and vanadium
摘要：
作为超冷中子（UCN）的有效“替代物”的元素的中子截面的研究对于核和粒子物理、宇宙学和重力学中的许多精确实验至关重要。在这种情况下，“吸收”包括中子的俘获和向上散射到UCN能区以上的能量。现有的数据，特别是氢的数据，彼此之间或与理论都不一致。在这份报告中，我们描述了在洛斯阿拉莫斯国家实验室UCN设施的UCN上散射截面的钒和氢在CH $_2$使用同时测量这些元素的辐射捕获截面的测量。我们测量了CH $_2$中氢的$σ_{up}=1972\pm130$ b，这低于理论预期，以及钒的$σ_{up} < 25\pm9$ b，与固体中热激发的中子加热的预期一致。
英文摘要：
The study of neutron cross sections for elements used as efficient ``absorbers'' of ultracold neutrons (UCN) is crucial for many precision experiments in nuclear and particle physics, cosmology and gravity. In this context, ``absorption'' includes both the capture and upscattering of neutrons to the energies above the UCN energy region. The available data, especially for hydrogen, do not agree between themselves or with the theory. In this report we describe measurements performed at the Los Alamos National Laboratory UCN facility of the UCN upscattering cross sections for vanadium and for hydrogen in CH$_2$ using simultaneous measurements of the radiative capture cross sections for these elements. We measured $σ_{up}=1972\pm130$ b for hydrogen in CH$_2$, which is below theoretical expectations, and $σ_{up} < 25\pm9$ b for vanadium, in agreement with the expectation for the neutron heating by thermal excitations in solids.
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