Analysis and measurement of shielding performance in large-scale HTS magnetic shields under ultralow magnetic fields

To satisfy the stringent magnetic cleanliness requirements in quantum sensing, biomedical imaging, and precision metrology, this study investigates the shielding performance of large-scale high-temperature superconducting (HTS) structures under ultra-low magnetic field conditions. A theoretical model based on the London equations coupled with magnetic vector potential is developed to simulate the Meissner-state response of U-shaped HTS configurations, and the effects of key geometric parameters—aspect ratio and wall thickness—on shielding behavior are systematically analyzed. An experimental platform, incorporating a cryogenic fluxgate sensor, is constructed to evaluate shielding performance at 77 K. Measurements show that both radial and axial shielding factors exceed 10⁴, with spatial decay trends closely matching those predicted by simulation. The measured results are sufficient for achieving a magnetically clean, ultra-low field environment. This combined simulation-experiment approach not only offers practical insights for optimizing HTS magnetic shielding structures, but also provides a promising pathway toward constructing magnetically clean environments for ultra-low field precision measurement applications.