CUED Publications database

A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors.

Egan, R and Philippe, M and Wera, L and Fagnard, JF and Vanderheyden, B and Dennis, A and Shi, Y and Cardwell, DA and Vanderbemden, P (2015) A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors. Rev Sci Instrum, 86. 025107-.

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Abstract

We report the design and construction of a flux extraction device to measure the DC magnetic moment of large samples (i.e., several cm(3)) at cryogenic temperature. The signal is constructed by integrating the electromotive force generated by two coils wound in series-opposition that move around the sample. We show that an octupole expansion of the magnetic vector potential can be used conveniently to treat near-field effects for this geometrical configuration. The resulting expansion is tested for the case of a large, permanently magnetized, type-II superconducting sample. The dimensions of the sensing coils are determined in such a way that the measurement is influenced by the dipole magnetic moment of the sample and not by moments of higher order, within user-determined upper bounds. The device, which is able to measure magnetic moments in excess of 1 A m(2) (1000 emu), is validated by (i) a direct calibration experiment using a small coil driven by a known current and (ii) by comparison with the results of numerical calculations obtained previously using a flux measurement technique. The sensitivity of the device is demonstrated by the measurement of flux-creep relaxation of the magnetization in a large bulk superconductor sample at liquid nitrogen temperature (77 K).

Item Type: Article
Subjects: UNSPECIFIED
Divisions: Div C > Materials Engineering
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 18:57
Last Modified: 18 Nov 2017 22:08
DOI: