Investigation of Superfluid Helium 3

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9418665 Packard The Principal Investigators will study two questions related to superfluid helium 3, a phase which exists below 2 x 10-3 K. The first area of research involves understanding the nature of helium 3 when it is in the form of films whose thickness is less than the superfluid coherence length. The Principals Investigators will determine if these films will exhibit superfluidity when deposited on helium 4 covered substrates. The initial thrust of the program is to develop tools to study surface waves on the film, so called third sound. These waves will be used as a probe of the films properties. The second area of activity will develop helium 3 dc Josephson junctions. These weak link structures should exhibit a nonlinear current pressure characteristic. These devices may permit the detection of macroscopic quantum interference analogous to the effects seen in dc superconducting quantum interference devices. % % % The rare isotope helium 3 forms a superfluid state at temperatures below 0.002 K. The Principal Investigators will determine if very thin films of this materials will continue to exhibit superfluid properties as the thickness of the sample is made progressively smaller. To answer this question we will develop techniques capable of detecting surface thickness waves. These acoustical techniques will provide insight into the properties of thin films. The properties of the superfluid when it flows through very small apertures will also be studied. It is believed that the fluid passing through submicron apertures will exhibit peculiar behavior which may lead to the development of very sensitive superfluid gyroscopes. ***