Development of high-Tc SQUID gradiometer systems for mobile applications

Practical applications of high-Tc SQUID devices such as Magnetic Anomaly Detection (MAD) and Non-Destructive Evaluation (NDE) require the SQUID system to operate unshielded with minimal passive shielding and with a good deal of mobility. Environmental magnetic noise and motion-induced noise, particularly due to the Earth's magnetic field are highly problematical and often prohibit successful operation. They can not only obscure the signal of interest, but also adversely affect the intrinsic noise level of the device (particularly at low-frequencies) sometimes to the point where it becomes unusable. For instance our high-Tc SQUID-based gradiometers have demonstrated ability to perform high resolution NDE scans where the device is moved along a straight line. However reliably tilting or rotating these devices in the Earth's field poses major difficulties - existing devices tend to be unstable due to for instance the effects of motion of trapped flux lines.EThOS - Electronic Theses Online ServiceGBUnited Kingdo