dB/dt Camera for Gradient Eddy Current Mapping Outside the Magnet

Motivation: Commercial dynamic field camera measures gradient eddy current fields in the magnet, where magnet eddy current can confound gradient coil's internal eddy current fields. Goal(s): To develop a field monitoring device, called dB/dt camera, to map short-time-constant eddy current fields on a standalone gradient coil. Approach: A circular array of 22 untuned pickup coils was placed inside two different gradient coils outside the magnet and the step response functions were measured and compared. Results: Eddy current fields with time constant ~100 μs were measured consistent with prior imaging results. The amplitudes correlated with the thickness of the conductors of the gradient coils. Impact: The proposed method enables time-resolved gradient eddy current field mapping without the magnet or power electronics. The method can help isolate eddy current sources in the gradient coil or RF subsystem.