Design and optimization of feedback control system for active shielding of HTS RF-SQUID based MCG

A High Tc RF-SQUID Based magnetocardiography system is developed for operating in a passively unshielded environment, in which active shielding is implemented to compensate field noises for the low to midrange frequency range. The main part of the implemented active shield configuration is a feedback control system designed for environmental noise cancelation in particular that of the power lines. This control system includes two layers of inner and outer compensation coils with respect to the liquid Nitrogen Dewar as parts of the designed active shield. The inner coils are surrounding the HTS SQUIDs which are placed in axial gradiometric configuration inside the dewar. The outer coils are surrounding the whole sensor setup by being placed outside the Dewar. All the coils are fed by a designed control system using the proper optimized filtering with respect to the frequency and the needed loop gains based on their characteristics. The considered approach for the optimization of the control system in this work is modeling the system using Ziegler-Nichols method. In this paper, we demonstrate the modeling and designing the optimized feedback control system.