A Digital SQUID Controller for Unshielded Biomagnetic Measurements
A biomagnetometer capable of achieving low noise Performance without magnetic shielding would be attractive in a wide range of clinical and research applications. Magnetically shielded enclosures add significant initial cost to biomagnetometer systems and preclude their portability. The primary obstacle to unshielded operation is the immense dynamic range between the ambient magnetic noise and the SQUID noise floor. Ambient magnetic field noise found in a typical urban environment can be over eight Orders of magnitude greater than the sensitivity of a modern thin film low-Tc superconducting (LTS) dc-SQUID magnetometer . Gradiometric magnetic sensors and linear combinations of magnetic sensors, including references may be used to separate the low-amplitude biomagnetic signals from the much larger environmental magnetic noise , . The accurate reproduction of fields by these sensors is a prerequisite to the effectiveness of linear noise reduction methods.
KeywordsDigital Signal Processor Slew Rate Flux Quantum Feedback Current Flux Error
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