ESR imaging of irradiated teflon tube using a highly linear field gradient by straight wires inserted in a cavity

ESR-CT imaging of irradiated teflon tube is described using a newly developed gradient coil generating a large and highly linear field gradient. The achieved magnitude of gradient is 4 T/m using low temperature nitrogen gas cooling and continuous current. The gradient coil, which is inserted into a cavity, consists of 16 equi-spaced parallel copper wires adhered on a 5mm diameter quartz tube perpendicular to a static magnetic field. The gradient can be two dimensionally rotated in a plane perpendicular to the cylinder axis by controlling the current of each wire independently. The error of the field gradient is less than 1% at the central 3.5 mm region in diameter. (author)