We have developed high-critical-temperature radio-frequency Super conducting QUantum Interference Devices (SQUIDs) with step-edge grain-boundary Josephson junctions and large flux focusers. These planar devices were fabricated from epitaxial YBa2Cu3O7 films and operated in the magnetometer and first-order gradiometer configurations while immersed in liquid nitrogen. At the temperature of 77K, we have attained a magnetic field resolution for the magnetometer better than 200 fT/Hz1/2 down to less than 1 Hz, i.e., over the low signal frequency range important for medical diagnostics. The results to date show a high promise for biomagnetic diagnostics. For the first time, we recorded the evoked responses from human brains using a high-temperature magnetometer and a first-order electronic gradiometer channel simultaneously. These results were obtained in a magnetically shielded room. An improvement in the magnetic field resolution by another order of magnitude is possible and probable.
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We are grateful to Prof. Dr. med. M. Hoke, Director of the Institute for Experimental Audiology for his support and the encouragement offered to us. We also thank Dr. J. Schubert and W. Zander, KFA-ISI, who fabricated the YBCO films by pulsed laser deposition. Work at KFA was supported, in part, by the German Minister of Research and Technology (BMFT), the Consortium on "First Applications of HTS in Microelectronics".
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Zhang, Y., Tavrin, Y., Mück, M. et al. Magnetoencephalography using high temperature rf SQUIDs. Brain Topogr 5, 379–382 (1993). https://doi.org/10.1007/BF01128694
- High-temperature superconductor
- Auditory evoked fields