Measuring Procedure to Realize the Ampere by the Superconducting Mass Levitation Method

Abstract

A new way to realize the ampere by the method of superconducting mass levitation is proposed. The approach promises to simplify the measurement procedure because it substitutes the "mechanical" joule realization by measurements in the levitation mode of the periods of small vertical oscillations of the mass. One has to measure the period value, with constant current flowing in the levitating coil, and again with the mass in the same position but with the coil short-circuited to maintain the magnetic flux constant.

A proposed superconducting magnetic levitation system intended to monitor stability of the unit of mass

“…In Figure 7 the frequencies of small oscillations of the levitated body are shown as a function of the body position. As may be seen, the lower part of the displacement interval is the range most appropriate to apply the method of small oscillations [8] because of the relatively large difference between the modes.…”

“…By adding a compensation coil that acts in opposition to the main coil, a fairly wide segment of isochronic oscillations in two modes of levitation can be provided. Applying a similar planar force element in the form of a magnetic bearing enables one not only to restrain displacements and turns of the levitated body along all unwanted coordinates, but also makes it possible to separate the frequencies of self-oscillation in the transverse directions far from that in the vertical and thereby include the frequencies of small vertical oscillations in the main group measurands required by the method [8,10].…”

“…In the general case, this function is non-linear as are its successive derivatives. While the equilibrium at the point is stable, our system is akin to a mechanical pendulum since the oscillation period is independent of the mass, and depends on and length in exactly the same way as a pendulum [8]. Treating the system as a classical oscillator we use the -dependent representations of (1) in their Taylor series expansions near .…”

“…In this case, the main subject for attention is the range of vertical displacement of the levitated body relative to the lateral dimensions of the element. Another is an interval of isochronic oscillations within the displacement range with a view to applying the method of small oscillations [8]. The second element is a sort of magnetic bearing or guide with appropriate transverse rigidity.…”

A preliminary study of a torsion balance based on a spherical superconducting suspension

“…The other crucial feature of any suspension is its stability both for vertical and for transverse motion. The restoring force due to magnetic forces depends on whether the coil-float system is in a constant-current or constant-flux mode [19]. In the constant-current mode the stiffness, K zi , becomes…”