Superconducting magnetic shield for MEG coupled with permalloy PC

Irisawa, Daiichi; Imai, Kiyokazu; Shintomi, K.; Yahara, A.; Matsubara, Hironori

doi:10.1002/eej.23195

Cited by 3 publications

(2 citation statements)

References 6 publications

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“…The latter ones, which exploit the intrinsic property of the SC materials, can be assembled using SC bulks [10][11][12] and/or SC coated conductors/tapes [13][14][15][16][17]. Furthermore, promising improvements of the shielding ability have been achieved by superimposing SC and ferromagnetic (FM) materials [18][19][20][21][22][23][24], including the possibility to cloak static (DC) and alternating (AC) magnetic fields in suitably shaped SC/FM heterostructures [25][26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Modelling and Performance Analysis of MgB2 and Hybrid Magnetic Shields

et al. 2022

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Superconductors are strategic materials for the fabrication of magnetic shields, and within this class, MgB2 has been proven to be a very promising option. However, a successful approach to produce devices with high shielding ability also requires the availability of suitable simulation tools guiding the optimization process. In this paper, we report on a 3D numerical model based on a vector potential (A)-formulation, exploited to investigate the properties of superconducting (SC) shielding structures with cylindrical symmetry and an aspect ratio of height to diameter approaching one. To this aim, we first explored the viability of this model by solving a benchmark problem and comparing the computation outputs with those obtained with the most used approach based on the H-formulation. This comparison evidenced the full agreement of the computation outcomes as well as the much better performance of the model based on the A-formulation in terms of computation time. Relying on this result, the latter model was exploited to predict the shielding properties of open and single capped MgB2 tubes with and without the superimposition of a ferromagnetic (FM) shield. This investigation highlighted that the addition of the FM shell is very efficient in increasing the shielding factors of the SC screen when the applied magnetic field is tilted with respect to the shield axis. This effect is already significant at low tilt angles and allows compensating the strong decrease in the shielding ability that affects the short tubular SC screens when the external field is applied out of their axis.

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Section: Introductionmentioning

confidence: 99%

Modelling and Performance Analysis of MgB2 and Hybrid Magnetic Shields

et al. 2022

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“…Therefore, the attenuation coefficients of the longitudinal and transverse fields do not exceed 1000 and several tens, correspondingly [5]. Superconducting shields have no equal in unique experiments on obtaining the ultimate magnetic vacuum [4], but in practical applications [6] it is advisable to combine them [7] with shields made of ferromagnetic materials that concentrate the magnetic field in their volume. Coaxially located ferromagnetic and superconducting screens not only have a higher magnetic field attenuation coefficient than taken alone, but also significantly reduce the spatial field variations.…”

Section: Introductionmentioning

confidence: 99%

Cooled ferromagnetic shield as a part hybrid system for isolation of a flux qubit from electromagnetic environment

Turutanov,

Lyakhno,

Boichenko

et al. 2021

The Journal of v. N. Karazin Kharkiv National University, Series "Physics"

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Currently, circuits for quantum informatics, communications and measuring equipment containing superconducting flux qubits in a planar design are being created by quantum engineering techniques. To function, such structures must be cooled in a refrigerator down to about 10 mK. The flux qubits have linear size of superconducting circuit of some tens of micrometers and are very sensitive to external magnetic fields and their variations. The qubit built in the gradiometer-like design has reduced sensitivity to external uniform magnetic fields, but remains quite sensitive to their variations. To protect the qubit from unwanted external magnetic fields, which include the Earth's field, man-made fields, and residual magnetic fields of the cryostat parts, it is necessary to create efficient magnetic shields. Earlier, we proposed a scheme for a single-photon microwave counter, in which a planar flux qubit in a gradiometer version serves as the receiving element. To let it function properly, a 3-layer hybrid magnetic shield composed of two superconducting and one ferromagnetic cylinders, has been designed for installation in a dilution refrigerator at 10 mK temperature. The effectiveness of such a shield depends on the correct design of all three shells. This paper presents the results of calculation and magnetic measurements of a cylindrical ferromagnetic screen made of low-temperature permalloy Cryoperm 10 in dc and low-frequency alternating magnetic fields. Cryoperm 10 keeps high magnetic permeability at liquid helium temperatures and below. It is shown that this shield is able of reducing the absolute value of the magnetic field and its variations by 55-70 dB. Together with superconducting lead magnetic shields, this design will reduce the absolute value of the field by 70 dB, and the field variation by 200 dB, which will provide the necessary conditions for the operation of a single-photon counter based on a flux qubit.

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