A recovery system for helium-3

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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.