抄録
A new 39 channel SQUID magnetometer system with 3D second-order gradiometer has been developed for research use in order to measure the biomagnetic fields. This is the total hardware system consisting of 39 SQUID sensors with detecting coils, readout electronics, two liquid helium dewars for MEG and MCG, a gantry, and a magnetically shielded room.
The noise characteristics of frequency domain of three components were measured. The power spectra of the noise field normal component are about 15fT/√Hz at 10Hz and under 10fT/√Hz at white noise. The power spectrums of the noise field tangential component are about 12fT/√HZ at 10Hz and under 10fT/√Hz at white noise. An alpha rhythm occurring from a subject's head was recorded with the amplitude of about 500fT at about 10Hz. We could measure the mixed AEF and SEF overlapping in time using this system. From these results, the system has a sufficient ability to measure weak magnetic fields from the brain.
