Ultra-sensitive SQUID instrumentation for MEG and NCI by ULF MRI

• Main Author: Körber, Rainer
• Format: Journal Article
• Language: English
• Published: 22.03.2019
• Subjects: Physics - Instrumentation and Detectors; Physics - Superconductivity
• DOI: 10.48550/arxiv.1903.09401

In: Eskola H., V\"ais\"anen O., Viik J., Hyttinen J. (eds) EMBEC & NBC 2017. EMBEC 2017, NBC 2017. IFMBE Proceedings, vol 65. Springer, Singapore The requirements for the construction of ultra-sensitive SQUID instrumentation as used in biomagnetism are presented. Typically, SQUIDs are inductively coupled to pick-up coils and for this arrangement one can improve the noise performance by increasing the sensing coil area. To achieve optimum sensitivity one has to consider the signal-to-noise ratio (SNR), which is an intricate interplay between source characteristics and noise origin. It turns out that separate pick-up coil designs are needed for various noise characteristics even for an identical source. Hence, a hybrid system with differently sized pick-up coils presents the best option for multipurpose applications. A single channel system with close to SQUID intrinsic noise level is also described. This is possible by utilizing a special dewar design and thereby enabling a further increase in SNR. Such a system might be used for current density imaging and neuronal current imaging by ultra-low-field magnetic resonance where it also must be able to be field-tolerant to up to 100-200 mT.