Development of high-Tc SQUID magnetometers for on-scalp MEG

This thesis describes the development of high critical temperature superconducting quantum interference device (high-Tc SQUID) magnetometers based on bicrystal grain boundary and nanowire junctions for the potential use in on-scalp magnetoencephalography (MEG), which is a new generation MEG technique with reduced sensor-to-subject standoff distances.MEG is a method of mapping neural dynamics in the human brain by recording the magnetic fields produced by neural currents. Its passive and non-contact nature allows doctors and neuroscientists to safely and effectively carry out clinical diagnoses and scientific research on the human brain. State-of-the-art MEG systems utilize low-Tc SQUID sensors with sensitivities of 1--5 fT/√Hz down to 1 Hz to measure the extremely tiny biomagnetic fields (~100 fT) from the brain. However, low-Tc SQUIDs require liquid helium cooling to reach their operating temperature