Long baseline thin film SQUID gradiometers

Author

Stolz, R. ; Zakosarenko, V.M. ; Fritzsch, L. ; Oukhanski, N. ; Meyer, H.-G.

Author_Institution

Dept. of Cryoelectron., Inst. for Phys. High Technol., Jena, Germany

Volume

11

Issue

1

fYear

2001

fDate

3/1/2001 12:00:00 AM

Firstpage

1257

Lastpage

1260

Abstract

We have developed a highly sensitive SQUID gradiometer for unshielded operation in the Earth´s magnetic field. It is implemented in an all-refractory Nb-AlO_x-Nb technology, and consists of gradiometer pick-up loops with an inductance of about 250 nH coupled to the SQUID by a flux transformer. The SQUID is designed as a highly balanced second order gradiometer consisting of four pairs of washers. It has an inductance of about 300 pH. The gradiometer chip has a size of 6 cm ×2 cm. The baseline of the gradiometer is 4 cm and the effective volume is about 300 mm³. We measured a white noise level of below 10 μΦ₀/Hz^½, corresponding to a gradient field resolution smaller than 40 fT/m·Hz^½. The total flux noise in the frequency band from 0.01 Hz to 10 Hz is below 150 μΦ_g. The balance of the gradiometer was determined by moving the gradiometer in the Earth´s magnetic field. Due to the high balance we can operate the gradiometer in field experiments

Keywords

SQUID magnetometers; biomedical measurement; magnetocardiography; superconducting device noise; superconductor-insulator-superconductor devices; white noise; 0.01 to 10 Hz; 4 cm; Earth magnetic field; Nb-AlO-Nb; all-refractory Nb-AlO_x-Nb technology; field experiments; flux transformer; gradient field resolution; gradiometer pick-up loops; highly balanced second order gradiometer; highly sensitive SQUID gradiometer; inductance; long baseline thin film SQUID gradiometers; portable human heart monitor; total flux noise; unshielded operation; washer pairs; white noise level; Earth; Inductance; Magnetic field measurement; Magnetic fields; Magnetic noise; Noise measurement; SQUIDs; Semiconductor device measurement; Transistors; White noise;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.919578

Filename

919578