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Trapped Fields >1 T in a Bulk Superconducting Ring by Pulsed Field Magnetization

Accepted version
Peer-reviewed

Type

Article

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Abstract

One potential application of magnetized RE-Ba-Cu-O (where RE = rare earth or Y) bulk superconductors is as a high-field alternative to conventional permanent magnets in desktop NMR and MRI systems. Pulsed field magnetization (PFM) is one of the most promising practical methods of magnetizing such bulks. However, the trapped fields obtained by PFM are much lower than those obtained using quasi-static methods like field-cooling magnetization (FCM) due to heating during PFM. Furthermore, bulk superconducting rings have proved more difficult to magnetize via PFM than discs. The reported trapped fields in single bulk superconducting rings magnetized by PFM are less than 0.35 T at the centre of the bore due to thermomagnetic instabilities. In this work, systematic PFM measurements on a bulk Gd-Ba-Cu-O ring were carried out and a trapped field of 1.3 T at 55 K was achieved using a multi-pulse, stepwise cooling (MPSC) method. In the MPSC method, a sequence of pulsed fields is used to magnetize the ring bulk. The pulsed field is increased in small increments and the sample temperature is decreased sequentially. Consequently, as some field is already trapped after the first pulse, the motion of the flux for subsequent pulses will be reduced, leading to less heat generated in the bulk sample. This greatly improves the thermomagnetic stability of the PFM process, enabling larger trapped fields.

Description

Keywords

Superconducting magnets, Magnetic flux, Magnetic resonance imaging, Magnetic field measurement, Heating systems, High-temperature superconductors, Magnetization, Bulk superconductors, bulk superconducting rings, high-temperature superconductivity, multi-pulse stepwise cooling, pulsed field magnetization, trapped field magnets, waveform control

Journal Title

IEEE Transactions on Applied Superconductivity

Conference Name

Journal ISSN

1051-8223
1558-2515

Volume Title

Publisher

Institute of Electrical and Electronics Engineers (IEEE)
Sponsorship
Engineering and Physical Sciences Research Council (EP/P020313/1)
EPSRC (EP/T014679/1)
EPSRC (EP/P020313/1; EP/T014679/1)
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