Passive levitation of small particles in vacuum: Possible applications to vacuum gauging

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Abstract
Most techniques for levitating small objects in a vacuum employ fluctuating electric or magnetic fields, often controlled by feedback from a position-sensing device to obtain the desired stability. We describe an alternative technique, diamagnetic levitation, which is particularly useful where compactness and simplicity are important. Diamagnetic levitation is passive in that steady magnetic fields are used and no position sensing or feedback are required. The theoretical background and prior developments are summarized. Two basic configurations, in which the magnetic fields are either vertical or horizontal, are distinguished. Particles of graphite and bismuth in sizes down to the micron range have been levitated in experimental systems of these types. Observations of particle motion as a result of interactions with the surrounding gas molecules are discussed. Many of the observed effects are pressure dependent. Several types of vacuum gauges based on these principles are suggested.

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