Ultra low noise all niobium DC-SQUIDs

Author

Daalmans, G.M. ; Bar, L. ; Bommel, F.R. ; Kress, R. ; Uhl, D.

Author_Institution

Siemens Res. Lab., Erlangen, West Germany

Volume

27

Issue

2

fYear

1991

fDate

3/1/1991 12:00:00 AM

Firstpage

2997

Lastpage

3000

Abstract

The noise and signal properties of SQUIDs with amorphous silicon barriers and Al₂O₃ barriers are studied. The barrier material is found to be of great importance for the value of the 1/f noise component. The best results were obtained for SQUIDs with Al₂O₃ barriers and a 1/f noise level at 1 Hz of about 1×10^-6Φ/√Hz was found. After integration of coupling coils onto the SQUIDs, a signal limitation and a dramatic increase of the noise were found. Implementation of a damping circuitry over the coupling coil results in optimized signals (Δ V(Φ₀/2)≃I_cR) and a white noise level comparable to the white noise level without a coupling coil. The 1/f noise component for SQUIDs with a damped coupling coil is higher than for 1/f noise component of SQUIDs without a coupling coil. For SQUIDs with Al₂O₃ barriers, the 1/f noise level keeps below 3×10^-6Φ₀/√Hz at 1 Hz. For SQUIDs with an amorphous silicon barrier the 1/f noise component changes per cooling cycle in an irregular way. The stability for thermal cycling and room-temperature storage is very good for all the devices

Keywords

SQUIDs; alumina; aluminium; amorphous semiconductors; electron device noise; elemental semiconductors; niobium; silicon; 1/f noise component; 1/f noise level; Nb-Al-Al₂O₃-Nb; Nb-Si-Nb; barrier material; coupling coil; coupling coils; damping circuitry; room-temperature storage; signal limitation; signal properties; thermal cycling; white noise level; Acoustical engineering; Amorphous silicon; Circuit noise; Coils; Coupling circuits; Damping; Niobium; Noise level; SQUIDs; White noise;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.133841

Filename

133841