We have used tuned receiver coils coupled to a dc SQUID preamplifier in a small scale magnetic resonance imaging (MRI) system operating at 425 kHz (B0 = 0.01 T). The coil and SQUID are cooled to 4.2 K in a modified biomagnetic cryostat. The modifications provide transparency to rf signals originating outside the cryostat while maintaining an acceptably low liquid helium boiloff rate. By applying negative feedback we have damped low loss, high Q-factor SQUID input circuits to achieve a useful imaging bandwidth of over 2 kHz.
ASJC Scopus subject areas
- Electrical and Electronic Engineering
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Physics and Astronomy (miscellaneous)