A recovery system for helium-3

近年来，我们已经能够用高分辨率的光谱技术来探索微观、分子和宏观、块体世界之间的尺寸制度。超流性是氦-4同位素(自旋为零的玻色子)在低温下的一种特别有趣的整体性质，例如，在粘度消失时表现出来。我们通过用原子尺寸分辨率研究嵌入到原子中的氦原子团簇中的分子，从微观尺度研究了超流性的演化。观察到的氦原子从分子的旋转运动中解耦，现在被认为是微观超流的一种表现，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动性。尚不清楚氦-3的自旋1/2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的解耦确实预示着超流的开始？或者氦-3星系团也会通过形成无自旋库珀对而表现出非经典的行为？到目前为止，这些问题还没有在实验上得到解决，结果将提供对介观尺寸区域中系统迷人的量子特性的洞察。氦-3气体贵得令人望而却步，需要资金建立回收系统，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。其他部件包括一个密封的泵，以避免污染空气和真空部件，如压力表和阀门。

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.