A Study of an Absolute Determination of the Magnetic Flux Quantum Using a Superconducting Levitation System

Shiota, F.; Hara, Kei; Hirata, T.

doi:10.1143/jjap.22.1439

Cited by 21 publications

(9 citation statements)

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“…The basic idea of the levitation method is that the electrical energy E el fed to the coil is converted to the energy of the magnetic field E mag and compared with the mechanical (gravitational potential) energy of the levitating object E pot [2,[15][16][17][18]:…”

Section: The Superconducting Magnetic Levitation Methodsmentioning

confidence: 99%

“…The first term on the right side of equation ( 5) is the magnetic field energy change E mag and the second term is the potential energy change E pot . The term on the left side is the electrical energy E el fed to the superconducting coil [16]. The advantages of a levitation instrument are compact size, lack of mechanical friction and ideal environment for cryogenic standards of electrical units.…”

Section: The Superconducting Magnetic Levitation Methodsmentioning

confidence: 99%

“…A simplified schematic diagram of a superconducting levitation system [17] is shown in figure 1. Technical details have been described elsewhere [15][16][17][18]. The applied constant current i in the coil is defined from the measurement of the voltage U c across a known resistance R ref with a digital voltmeter (DVM).…”

Section: The Superconducting Magnetic Levitation Methodsmentioning

confidence: 99%

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Mass determination with the magnetic levitation method—proposal for a new design of electromechanical system

Kajastie¹,

Riski²,

Satrapinski³

2009

Metrologia

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The method for realization of the kilogram using 'superconducting magnetic levitation' was re-evaluated at MIKES. The realization of the kilogram based on the traditional levitation method is limited by the imperfections of the superconducting materials and the indefinable dependence between supplied electrical energy and the gravitational potential energy of the superconducting mass. This indefiniteness is proportional to the applied magnetic field and is caused by increasing losses and trapped magnetic fluxes. A new design of an electromechanical system for the levitation method is proposed. In the proposed system the required magnetic field and the corresponding force are reduced, as the mass of the body (hanging from a mass comparator) is compensated by the reference weight on the mass comparator. The direction of the magnetic force can be upward (levitation force, when the body is over the coil) or downward (repulsive force, when the body is under the coil). The initial force to move the body from the coil is not needed and magnetic field sensitivity is increased, providing linearization of displacement versus applied current. This new construction allows a lower magnetic induction, reduces energy losses compared with previous designs of electromechanical system and reduces the corresponding systematic error.

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Section: The Superconducting Magnetic Levitation Methodsmentioning

confidence: 99%

Section: The Superconducting Magnetic Levitation Methodsmentioning

confidence: 99%

Section: The Superconducting Magnetic Levitation Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Mass determination with the magnetic levitation method—proposal for a new design of electromechanical system

Kajastie¹,

Riski²,

Satrapinski³

2009

Metrologia

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“…The going-up and going-down data are measured successively more than ten times and each series of data is numbered with a serial number Sr: even Sr for going up and odd Sr for going down. Further details of the system and the procedure for the measurement have been given elsewhere [4].…”

Section: Apparatusmentioning

confidence: 99%

A study of a superconducting magnetic levitation system for an absolute determination of the magnetic flux quantum

Shiota¹,

Hara

1987

IEEE Trans. Instrum. Meas.

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A study of the equilibrium positions of a superconducting magnetic levitation system which substitutes an electromagnetic energy for a mechanical energy is in progress for the absolute determination of the magnetic flux quantum «1>0' The study on a preliminary system at ppm-level resolution has been done and the reproducibility of the trajectory turned out to be of the order of 10 ppm. The problems of the present system and ideas for the next system at the sub-ppm level are discussed.(2) corner cube reflector Laser Interferometerwhere k is the flux-to-current conversion factor and n; is the order of the SQUID.The vertical position z, of the center of gravity of M is measured by a laser interferometer. Sets of data (ie' z.) as a function of cI> describe the equilibrium trajectory of the system. It is assumed that there exists a unique equilibrium trajectory as long as the attitude of M is stable and the Meissner effect of the system holds.The total energy U of the system is the sum of the magnetic energy of the system and the gravitational potential energy of M. The difference in U between two points (epf, i el , Zel) and (cI>h, i eh , Zeh) arises from the energy supplied by the current driver I d during the flux-up from cI>l to 4>h. This energy injected under a quasi-static flux-up condition can be obtained by the integration of i e over cI>I to cI>h on the equilibrium trajectory, sõ 4>h i e dcI> = ! (cI>h i eh -cI>li el) + mg (Zeh -Zel) (3) 4>[ where g is the gravitational acceleration.Introducing the expressions for cI> and i e in terms of 4>0 Fig. 1. Superconducting magnetic levitation system.The body M is levitated by the force due to the Meissner effect when cI> is large enough. When cI> is kept constant (is = 0), M reaches the equilibrium position which depends on cI>.The system in equilibrium will now be dealt with, and quantities in equilibrium are indicated with the suffix "e." The coil current i, is measured by a SQUID ammeter (CSQ) which is calibrated with a Josephson voltage reference and a calibrated resistor aswhere N is the number of cI>0 linking C. II. THEORYA superconducting magnetic levitation system is composed of a superconducting floating body M with mass m, a superconducting coil C, and the Josephson junction J irradiated with a microwave frequency 1as shown in Fig. 1. The flux cI> linking C increases when the bias current is of J is set on the first Shapiro step ( V] = 1cI>0) by the drive current i d controlled by the SQUID ammeter (VSQ) so that the EMF of C corresponds to 1cI>0.This process may be called flux-up, and cI> is obtained by the integration oflover the flux-up period T as

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“…is the schematic drawing of the superconducting magnetic levitation experiment at the NRLM [1,2]. A superconducting coil is driven by a current source .so that the voltages at the coil terminals is the same as that at a Josephson junction biased at a constant voltage step.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the energy loss in superconductors used in the superconducting magnetic levitation experiment

Miki¹,

Shiota²,

Fujii³

Conference on Precision Electromagnetic Measurements. Conference Digest. CPEM 2000 (Cat. No.00CH37031)

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A Study of an Absolute Determination of the Magnetic Flux Quantum Using a Superconducting Levitation System

Cited by 21 publications

References 1 publication

Mass determination with the magnetic levitation method—proposal for a new design of electromechanical system

Mass determination with the magnetic levitation method—proposal for a new design of electromechanical system

A study of a superconducting magnetic levitation system for an absolute determination of the magnetic flux quantum

Evaluation of the energy loss in superconductors used in the superconducting magnetic levitation experiment

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