Neuromagnetic SQUID measurements in a helmet-type superconducting magnetic shield of BSCCO

A superconducting quantum interference device (SQUID) magnetometer has successfully detected magnetic fields emitted from a human brain in a helmet-size superconducting magnetic shield of the high-T/sub c/ superconductor Bi-Sr-Ca-Cu-O/sub x /(BSCCO). The sensitivities of the RF-SQUID and the DC-SQUID of quasi-planar Josephson junctions-superconducting weak links are 20 fT/ square root Hz and 4 fT/ square root Hz, respectively. The magnetic shield can reduce a magnetic field to -120 dB or 10/sup -6/ even at as low a frequency as 0.2 Hz. The authors have detected somatosensory evoked magnetic fields stimulating the tibial nerves of the patient by current pulses.<
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