Biomagnetic measurements with HTS SQUID magnetometers in moderate shielded environments

An HTS SQUID magnetometer for biomagnetic measurements was implemented in a moderate noise shielded environment. The intrinsic noises of the SQUID magnetometer shielded with a tri-layer magnetic shielding cylinder were 50 fT/Hz/sup 1/2/ above 10 Hz and 100 fT/Hz/sup 1/2/ at 0.1 Hz. The moderate shielded environments are constructed of mu-metal layers. With the moderate shielding the magnitude of the QRS complex of a rat specimen was found to be around 10 pT and the signal-to-noise ratio was larger than 10. The requirements for improving biomagnetic measurements in the moderate magnetic shielding are discussed.