Neuromagnetic SQUID measurements in a helmet-type superconducting magnetic shield of BSCCO

Ohta, Hiroshi; Koike, Atsushi; Hoshino, Kazutomo; Kotaka, H.; Sudoh, E.; Kato, Kenichi; Takahara, Hidefusa; Uchikawa, Y.; Shinada, K.; Takahata, M.; Yamada, Yasuharu; Matsui, Toshiaki

doi:10.1109/77.233577

Cited by 21 publications

(6 citation statements)

References 13 publications

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“…Several high sensitive scientific devices, e.g. superconducting quantum interference devices [1,2], dc current transformers [3], or cryogenic current comparators [4], need to be protected against the magnetic field environment and therefore must be shielded. Superconducting materials are certainly the best candidates to build passive magnetic shields at low frequency.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Shielding Above 1 T at 20 K With Bulk, Large Grain YBCO Tubes Made by Buffer-Aided Top Seeded Melt Growth

Wera

Fagnard

Kumar

et al. 2017

IEEE Trans. Appl. Supercond.

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YBCO tubes of ~ 10 mm diameter closed at one extremity were engineered by a Buffer-Aided Top Seeded Melt Growth fabrication process (BA-TSMG). These tubes can act as efficient "dc" magnetic shields and are observed to reduce axial flux densities of 1.5 T by a factor of 100 at 20 K. Such performances are comparable in magnitude to the record threshold inductions reported for bulk MgB2 and Bi-2212 materials at lower temperatures. Magnetic shielding measurements for open and closed tubes at 77 K also show that the presence of the cap improves substantially the shielding performance at the closed extremity since it reduces the penetration through the open end. This fabrication technique is extremely promising for shielding "dc" stray fields generated by HTS magnets operated in a temperature range obtained by cryocoolers, liquid hydrogen (20 K) or liquid neon (27 K).

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Section: Introductionmentioning

confidence: 99%

Magnetic Shielding Above 1 T at 20 K With Bulk, Large Grain YBCO Tubes Made by Buffer-Aided Top Seeded Melt Growth

Wera

Fagnard

Kumar

et al. 2017

IEEE Trans. Appl. Supercond.

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“…Today high temperature superconductors (HTS) give the possibility to safely work at intermediate temperatures (20-30 K) in reasonably high fields (2-3 T), but the manufacturing costs of the oxide windings are too high to be extensively used as active shields. HTS passive shields are currently being studied [7] and a quite large HTS passive shield has been manufactured with the bismuth based oxide superconductor (BSCCO) working at 77 K [8]. Nevertheless at this temperature this material cannot be used to shield high fields (larger than 2 T) and, furthermore, it does not have enough mechanical strength to be subjected to the corresponding electromagnetic stresses of high fields.…”

Section: Introductionmentioning

confidence: 99%

Magnetic shielding capability of MgB₂cylinders

Rabbers¹,

Oomen²,

Bassani³

et al. 2010

Supercond. Sci. Technol.

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The shielding of a DC magnetic field has been demonstrated to be complete at 4.2 K, at least up to 2 T, inside the 18 mm bore of a thick MgB 2 bulk cylinder, 70 mm tall. No hysteresis has been detected along the cycle of the field application and removal, and no flux jumps have been detected either. The MgB 2 cylinder was manufactured by the Reactive Mg Liquid Infiltration process, an 'in situ' technology able to give very dense MgB 2 manufacts. According to the previously measured J c (B, T ) characteristics of a MgB 2 bulk superconductor of the same origin and quality, a critical current density of about 30 kA cm −2 can be assumed at the fields of 2-3 T and at the temperature of 4.2 K of the reported shielding experiment. Accordingly, we estimate that the thickness of the MgB 2 cylinder filled by the shielding currents is about 5.75 mm, lower than the present cylinder thickness of 8.77 mm.

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“…We have wanted to have a less expensive and more effective shield room since then. When we confirmed that a YBCO vessel can reduce an external magnetic field by −100 dB or a factor of 10 −5 , we proposed the application of superconducting magnetic shields to a neuromagnetic SQUID [1,2].…”

Section: Introductionmentioning

confidence: 66%

A 64-channel whole-head SQUID system in a superconducting magnetic shield

Ohta

Matsui

Aono

et al. 1999

Supercond. Sci. Technol.

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A superconducting magnetic shield of high-Tc superconductor Bi(Pb)-Sr-Ca-Cu-Ox has been constructed whose diameter is 65 cm and length is 160 cm. We have successfully observed magnetic fields from somatosensory-evoked human brains in the superconducting magnetic shield by stimulating the median nerves of patients by current pulses. We made a 64-channel whole-head SQUID magnetometer of superconductor/normal metal/superconductor (SNS) junctions which do not show low-frequency telegraph noise. The sensitivities of the dc SQUID mesoscopic SNS junctions are around 5 fT Hz-1/2 even in rather unfavourable surroundings. The magnetic shield can reduce a magnetic field by around -80 dB or a factor of 10-4 even at as low a frequency as 0.05 Hz. Therefore SQUIDs of SNS junctions and a superconducting magnetic shield are a good combination.

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Neuromagnetic SQUID measurements in a helmet-type superconducting magnetic shield of BSCCO

Cited by 21 publications

References 13 publications

Magnetic Shielding Above 1 T at 20 K With Bulk, Large Grain YBCO Tubes Made by Buffer-Aided Top Seeded Melt Growth

Magnetic Shielding Above 1 T at 20 K With Bulk, Large Grain YBCO Tubes Made by Buffer-Aided Top Seeded Melt Growth

Magnetic shielding capability of MgB₂cylinders

A 64-channel whole-head SQUID system in a superconducting magnetic shield

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Neuromagnetic SQUID measurements in a helmet-type superconducting magnetic shield of BSCCO

Cited by 21 publications

References 13 publications

Magnetic Shielding Above 1 T at 20 K With Bulk, Large Grain YBCO Tubes Made by Buffer-Aided Top Seeded Melt Growth

Magnetic Shielding Above 1 T at 20 K With Bulk, Large Grain YBCO Tubes Made by Buffer-Aided Top Seeded Melt Growth

Magnetic shielding capability of MgB2cylinders

A 64-channel whole-head SQUID system in a superconducting magnetic shield

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Magnetic shielding capability of MgB₂cylinders