Confocally shielded elliptical RF resonators: application to in-vivo nuclear magnetic resonance

This work describes a useful property of confocal elliptic cylinders, whereby the outer conducting cylindrical shield is used to confine the magnetic field produced by a surface current distribution on the inner cylinder. In order to produce a uniform transverse field within the inner cylinder it is sufficient to use the same current distribution that would give a uniform field in the absence of a shield. This property can be applied to the production of uniform circularly-polarised magnetic fields, such as those used in in-vivo NMR.