Title :
Multi-loop relaxation oscillation SQUID magnetometers with large flux-to-voltage transfer functions
Author :
Kawai, Jun ; Uehara, Gen ; Higuchi, Masanori ; Ogata, Hisanao ; Kado, Hisashi
Author_Institution :
Appl. Electron. Lab., Kanazawa Inst. of Technol., Ishikawa, Japan
fDate :
3/1/2001 12:00:00 AM
Abstract :
A multi-loop Relaxation Oscillation SQUID (ROS) with direct voltage readout is fabricated and characterized. We designed and fabricated four-loop ROSs with the size of 5 mm ×5 mm. A maximum voltage modulation of 100 μV and a flux-to-voltage transfer function of more than 10 mV/Φ0 were obtained. With a direct voltage readout flux locked loop (FLL), a magnetic field resolution of 4 to 10 fT/√Hz was obtained in the frequency range from 0.3 Hz up to the white region. Using this magnetometer, we demonstrated the measurement of a brain response
Keywords :
SQUID magnetometers; biomedical measurement; magnetoencephalography; readout electronics; relaxation oscillators; transfer functions; 0.3 Hz to 1 kHz; MEG system; Nb-Al-AlO-Nb; brain response measurement; direct voltage readout; direct voltage readout flux locked loop; flux-to-voltage transfer function; hysteretic dc SQUID; magnetic field resolution; maximum voltage modulation; multi-loop relaxation oscillation SQUID magnetometers; Frequency locked loops; Interference; Magnetic field measurement; Magnetic flux; Magnetic sensors; Niobium; SQUID magnetometers; Spatial resolution; Transfer functions; Voltage;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
