Feed cable system for coils in high magnetic fields

Abstract

A toroidal vacuum dewer (22) holds a superconducting magnet assembly (10) which generates a substantially temporally constant magnetic field through a central bore (12). A whole body gradient coil (30) and a whole body RF coil assembly (32) are mounted to a cylindrical member (24) of the dewar. An insertable gradient coil assembly (40) is selectively insertable into and removable from the bore. The insertable gradient coil assembly includes gradient coils for selectively generating magnetic field gradients along three mutually orthogonal axes, e.g. x, y, and z-axes. A flexible cable (42) connects the insertable gradient coil with a series of current amplifiers (44). The current amplifiers selectively generate current pulses which are fed along feed conductors (84) of the coil assembly and which return along return conductors (86) of the cable. The feed and return conductors are configured such that the net feed and the net return current traverse the same effective path in opposite directions. Stated more mathematically, .EPSILON.R.sub.i .times.(I.sub.i .times.B.sub.ext)=0 where R.sub.i is the distance of the i-th conductor from the common path, I.sub.i is the current carried by the i-th conductor, and B.sub.ext is the temporally constant magnetic field generated by the main magnetic field assembly. Because the net feed and return current pulses follow the same path, i.e. are coaxial, the net torque and the net force from the interaction between the current pulses and the temporally constant magnetic field are zero.

Dependencies are inferred from the claim text.