A Method of Detrapping Magnetic Flux in a SQUID Sensor Using an Integrated Thin-Film Heater

Kohtaroh GOTOH  Norio FUJIMAKI  Takeshi IMAMURA  Shinya HASUO  Akihiro SHIBATOMI  

IEICE TRANSACTIONS on Electronics   Vol.E74-C   No.7   pp.2029-2035
Publication Date: 1991/07/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Low Temperature Electronics)

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We produced a double-layer thin-film heater to detrap magnetic flux in a SQUID sensor. The heater is integrated on a sensor chip, and consists of a lower resistor layer and an upper superconducting layer to cancel the magnetic field produced by the heater current. The SQUID sensor is cooled below its critical temperature with a temperature gradient to detrap the flux completely. To make the gradient, we had to decrease heater power to zero over an interval exceeding 10-4 second in our experiment, which is almost equal to the sensor chip's thermal time constant. The integrated heater effectively controls the temperature profile and detraps flux in the sensor.