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Neutron conversion and cascaded cooling in paramagnetic systems for a high-flux source of very cold neutrons

机译：中子转换和级联冷却在顺磁系统中，用于非常冷中子的高通量源

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A new neutron-cooling mechanism is proposed with potential benefits for novel intense sources of very cold neutrons with wavelengths > 2 nm, and for enhancing the production of ultracold neutrons. It employs inelastic magnetic scattering in weakly absorbing, cold paramagnetic systems. Kinetic energy is removed from the neutron stepwise in constant decrements determined by the Zeeman energy of paramagnetic atoms or ions in an external magnetic field, or by zero-field level splittings in magnetic molecules. The stationary neutron transport equation is analyzed for an infinite, homogeneous medium with Maxwellian neutron sources, using inelastic scattering cross sections derived in an appendix. Nonmagnetic inelastic scattering processes are neglected. The solution therefore still underestimates very cold neutron densities that should be achievable in a real medium. Molecular oxygen with its triplet ground state appears particularly promising, notably as a host in fully deuterated O-2-clathrate hydrate. Other possibilities are dry O-2-He-4 van der Waals clusters and O-2 intercalated in fcc-C-60. For conversion of cold to ultracold neutrons, where an incident neutron imparts only a single energy quantum to the medium, the paramagnetic scattering in the clathrate system is found to be stronger, by more than an order of magnitude, than the single-phonon emission in superfluid helium, when evaluated for an incident neutron spectrum with the optimum temperature for the respective medium. Moreover, the multistep paramagnetic cooling cascade leads to further strong enhancements of very cold neutron densities, e.g., by a factor 14 (57) for an initial neutron temperature of 30 K (100 K), for the moderator held at about 1.3 K. Due to a favorable Bragg cutoff of the O-2 clathrate, the cascade-cooling can take effect in a moderator with linear extensions smaller than a meter.
机译：提出了一种新的中子冷却机构，具有具有波长> 2nm的新型冷中子的新型强态源的潜在益处，以及增强超容器中子的生产。它采用无弹性磁力散射在弱吸收，冷的顺磁系统中。通过磁性磁场中的顺磁原子或离子的塞曼能量，或通过磁性分子中的零场水平分离来逐步地从中子逐步从中子中移除动能。分析固定中子传输方程的无限均匀介质，其具有Maxwellian中子源，使用源中衍生在附录中的非弹性散射横截面。忽略了非磁性非弹性散射过程。因此，解决方案仍然低估了应该在真实培养基中实现的非常冷的中子密度。具有三重态地位状态的分子氧似乎特别有希望，特别是作为完全氘代O-2-2-Clathrate水合物中的宿主。其他可能性是干燥的O-2-HE-4 van der WALS簇和O-2在FCC-C-60中插入。为了转换冷到超级空中中子，其中入射中子仅赋予介质的单个能量量子，发现克拉乳酸盐系统中的顺磁散射更强，比单声道排放量更强，比单位发射更大超流氦，当具有相应培养基的最佳温度的入射中子谱评估时。此外，多步骤顺磁性冷却级组导致非常冷的中子密度的进一步强大增强，例如，通过30k（100k）的初始中子温度的因子14（57），所述主持人在约1.3k处保持的主持人对于O-2 Clathrate的良好布拉格截止，级联冷却可以在主持人中生效，线性延伸器小于仪表。

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