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TitleDevelopment of a split-toroid high-temperature superconducting cryogenic current comparator
Publication TypeJournal Article
Year of Publication2001
AuthorsEarly, M.D., Jones K., Staines M.P., and Exley R.R.
JournalIEEE Transactions on Instrumentation and Measurement
Pagination306 - 309
Date Published2001
ISSN00189456 (ISSN)
KeywordsAttenuation, Comparator circuits, Cryogenic current comparators, Cryogenic electronics, Cryogenic equipment, High temperature superconductors, Magnetic shielding, Superconducting shielding, Yttrium barium copper oxides
AbstractCryogenic current comparators (CCCs) based on split toroidal shields show promise for the construction of high-accuracy ratio devices using high-temperature superconductors. To test this approach we have carried out measurements on a low-temperature superconducting prototype built of three layers of toroidal shields. We find that ratio accuracies of about 1 in 107 are achievable for this prototype. After several attempts, we were also able to construct a toroidal two-layer CCC fabricated of YBCO (YBa2Cu3O7) components using split shields. The results from measurements on this device at low temperatures (4 K) indicate that the shielding provided by these layers does not provide sufficient attenuation of the leakage flux. The challenge remains to find a processing technique to produce YBCO in a machinable form with satisfactory magnetic shielding properties.

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