A recovery system for helium-3

近年来，我们已经能够探索之间的微观，分子和宏观，散装世界的高分辨率光谱技术的尺寸制度。超流性是氦-4同位素（自旋零玻色子）在低温下的一种特别有趣的整体性质，并且表现为例如消失的粘度。我们通过原子尺度分辨研究了氦原子团簇中的分子，从微观尺度研究了超流的演化。观察到的氦原子与分子旋转运动的解耦现在被认为是微观超流性的表现，并且发生在只有10个氦原子的团簇大小中。我们建议将这些研究扩展到氦-3同位素（自旋1/2费米子），它在比氦-4低得多的温度下表现出超流性。目前还不清楚氦-3的自旋½将如何影响实验结果。氦-3是否会与分子的旋转运动保持耦合，从而提供“最终证据”，证明氦-4的解耦确实表明超流性的开始？或者氦-3团簇也会通过形成无自旋的库珀对而表现出非经典的行为？这些问题到目前为止还没有得到解决的实验结果将提供洞察迷人的量子性能的系统中的介观尺寸制度。氦-3气体非常昂贵，需要资金来建立一个回收系统，使我们能够在光谱仪中回收氦-3。回收系统的核心是一个氦压缩机，它使我们能够达到拟议实验所需的超过150个大气压的高压。其他组件包括一个密封的泵，以避免空气和真空组件，如仪表和阀门污染。

In recent years, we have been able to explore the size regime between the microscopic, molecular and the macroscopic, bulk worlds with high resolution spectroscopic techniques. Superfluidity is a particularly interesting bulk property of the helium-4 isotope (spin zero Boson) at low temperatures and manifests itself, for example, in vanishing viscosity. We have studied the evolution of superfluidity from the microscopic scale by investigating molecules embedded in successively larger helium clusters with atom by atom size resolution. The observed decoupling of helium atoms from the rotational motion of the molecule is now accepted to be a manifestation of microscopic superfluidity and occurs in cluster sizes with as few as ten helium atoms. We are proposing to extend these studies to the helium-3 isotope (spin ½ Fermion) which exhibits superfluidity at a much lower temperature than helium-4. It is unclear how the spin ½ of helium-3 will affect the outcome of the experiments. Will the helium-3 stay coupled to the rotational motion of the molecule, and thus provide the 'final proof' that the decoupling in helium-4 indicates indeed the onset of superfluidity? Or will the helium-3 clusters also behave non-classically through the formation of spinless Cooper pairs? These questions have thus far not been addresses experimentally and the results will provide insight into the fascinating quantum properties of systems in the mesoscopic size regime. Helium-3 gas is prohibitively expensive and funds are requested for a recovery system that allows us to recycle the helium-3 in our spectrometer. The heart of the recovery system is a helium compressor that allows us to reach the high pressures of over 150 atm needed for the proposed experiments. Other components include a hermetically sealed pump to avoid contamination with air and vacuum components such as gauges and valves.