DC-SQUID magnetometer system for detecting vector value of magnetic field

Nakanishi, Masakazu; Kasai, Nahoko; Kado, H.; Koyanagi, M.

doi:10.1109/20.92496

Cited by 5 publications

(1 citation statement)

References 10 publications

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“…The influence of homogeneous fields can be reduced by three to four orders of magnitude in this manner. The remaining level of noise fields can be further reduced by electronic compensation using reference channels [2]. This kind of electronic gradiometry together with selective filtering will permit us to obtain the entire field resolution.…”

Section: Introductionmentioning

confidence: 99%

A niobium planar SQUID gradiometer operating in an unshielded environment

Bär¹,

Daalmans²,

Uhl³

et al. 1996

Supercond. Sci. Technol.

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We present an integrated thin-film gradiometric SQUID sensor in Nb-Al/Al 2 O 3 -Nb technology. The dc-SQUID converter is designed as a parallel inductance double-washer SQUID. It is inductively coupled to a planar parallel inductance gradiometer antenna with 15 mm baseline by two series input coils with eight turns each. The field gradient sensitivity is 0.5 nT cm −1 −1 0 . The intrinsic field gradient resolution down to 1 Hz is 5 fT cm −1 Hz −1/2 , measured in a shielded environment.The sensor can be operated reliably without any magnetic shielding. Under these conditions the transfer function dV /d is decreased by about a factor of three, resulting in a field gradient resolution of 15 fT cm −1 Hz −1 in the white noise region.Coherent noise sources produced by a power line and railway were suppressed by means of electronic subtraction using a reference channel and selective filtering. The resolution of the system is demonstrated by MCG measurements without any shielding.

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Section: Introductionmentioning

confidence: 99%

A niobium planar SQUID gradiometer operating in an unshielded environment

Bär¹,

Daalmans²,

Uhl³

et al. 1996

Supercond. Sci. Technol.

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Noise characteristics of NbN nanobridge dc SQUIDs fabricated by field emission technique

Nagaoka

Irie

Hamasaki

et al. 1991

Electron Comm Jpn Pt II

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NbN nanobridge dc SQUIDs were fabricated by the field evaporation method and their noise characteristics were evaluated. The fabricated device has a magnetic flux‐voltage conversion efficiency Φ of about 2.5 mV/Φ0 and hence the device has a higher gain than that of the tunneling‐type device with a resistive shunt. The energy resolution is as small as 40 h. When the fabricated SQUID was installed in an FLL circuit and the dynamic range was measured, it is found that an output is proportional to the input for the input magnetic flux of ±32Φ0 without removing the lock. The magnetic flux resolution of the FLL circuit used is 9 × 10−10 Φ02/Hz in the white noise region (at 3 kHz). In the low‐frequency region less than 100 Hz, the 1/f noise described by 5.8 × 10−8 (1/f)Φ02/Hz was observed. This value of the magnetic flux resolution is large by one order of magnitude than that inherent to the device and the noise of the electronics is predominant.

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