Next Generation HTS SQUID Gradiometer Systems and their Portable Operation in Unshielded Environments

This programme aims to develop fully-portable and more sensitive HTS SQUID systems that will operate in unshielded environr and to greatly increase their potential for use in biomagnetic measurements (in particular adult and foetal magnetocardiogra non-destructive evaluation and geophysics.There are three strands to the programme:1. Improvements to the intrinsic sensitivity by (a) developing a modified version of the SQUID - the Superconducting Qua Interference Filter or SQIF (b) enhancing the coupling efficiency between the SQUID and its field-sensing coils, includin development of multi-layer structures based on NdBaCuO and (c) developing techniques to grow HTS films on larger substrate to make larger gradiometers.2. The development of high-balanced second-order gradiometers for unshielded measurements. These will be formed electron from two first-order gradiometers, with additional noise rejection by 3-axis reference magnetometers and computer-based s processing in the time or frequency domains.3. Improvements to portability through the design, analysis and testing of a prototype system that uses no cryogenic liquid cryocooler, based on a solid nitrogen cooler.