A new type of passive magnetic shielding for superconducting quantum interferometers

High-efficiency magnetic shielding is very important for the reliability and stability of ultrahigh precision superconducting quantum interferometers. In practice, high permeability bulky multilayered magnetic shielding, or small lightweight shield buckets with differential plane gradient meters are generally used to realize ultrahigh sensitivity signal measurements. In this paper, a new type of high performance magnetic shielding device is proposed, which is realized by combining real-time dynamic magnetic compensation with high-temperature superconducting coils. The effect of the hybrid magnetic shield has been evaluated using numerical simulation and experimental measurements of the axial and transverse magnetic fields; the shielding factor was found to be as high as 80 dB. This new type of active magnetic shield with a high-temperature superconducting ring improves not only the axial but also the transverse shielding effect.