Abstract: The invention is directed to electromagnets for producing a high uniformity magnetic field or shielding a magnetic field by the use of passive compensation coils in the form of rings of superconductive material positioned perpendicularly adjacent to the electromagnet windings. Current induced into the rings of superconducting magnetic material establishing magnetic fields perpendicular to the electromagnetic magnetic field, thereby, depending on this size and quantity of the rings a highly uniform magnetic field or the cancelling of the magnetic field from the electromagnet adjacent to the surface of the rings remote from the electromagnet field occurs. High temeprature superconducting material can be used for the rings which lead to high temperature operation.