An electronic second-order gradiometer for biomagnetic applications in clinical shielded rooms
作者： D. Drung , H. Koch
DOI: 10.1109/77.233526
关键词: Sensitivity (electronics) 、 Shielded cable 、 SQUID 、 Electronic circuit 、 Nuclear magnetic resonance 、 Magnetometer 、 Gradiometer 、 Biasing 、 Square root 、 Optics 、 Physics
摘要: A modular 55-channel magnetometer for biomagnetic studies in clinical shielded rooms is described. Seventy-six superconducting quantum interference device (SQUID) magnetometers three levels are used to electronically form first-order or second-order gradiometer configurations. The completely integrated on 7.2-mm*7.2-mm chips. Additional positive feedback increase the gradient of V- Phi (voltage-flux) characteristics dV/d approximately=1 mV/ /sub 0/, and a novel scheme called bias current reduces sensitivity theta / I/sub b/ approximately=0.02 0// mu A. This allows one couple SQUIDs directly simplified electronics without helium-temperature impedance-matching circuits flux modulation techniques. noise level typically 1.4 fT/ square root Hz at 1 kHz 3.2 Hz, measured inside Pb/Cryopern shield. seven-channel prototype module has been tested successfully room. typical 2.2 THz 7 2 achieved. >
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