Eddy current disruption: effect on nuclear magnetic resonance coil impedance and power loss

We present a theoretical development and experimental verification of a description of power loss and sample resistance for a lossy sample in a nuclear magnetic resonance radio frequency coil for a sample geometry where the eddy current streamlines are disrupted from their usually assumed circular paths. Specifically treated is the case of a lossy hemisphere. The problem is solved for two orientations; with the induction parallel and perpendicular to the flat surface of the hemisphere. Results of this analysis as well as those for the full sphere as presented by Hoult and Lauterbur are compared with observation for a variety of sample conductivities and orientation.