Role and Impact of the Eddy Current Shield in the LNCMI-G Hybrid Magnet

In the new 43-T LNCMI hybrid magnet, a good conducting shield is inserted between the resistive insert magnet and the superconducting outsert magnet. Its goal is to decrease the ac losses induced in the superconducting conductor during a fault of the insert, disruption of the resistive coils (i.e., fast discharge) by smoothing the flux variations, and avoidance of a quench of the superconducting coil. The induced currents within the shield are very large due to the presence of copper material, which is the drawback of a good screening effect. Such currents result in large Lorentz forces, particularly during the most severe fault scenario of the resistive insert with the burnout of half of the Bitter coils. Finally, the detection system must be specially designed to handle the effects of the shield on the induced voltages.