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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 10 4 , 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
Dou et al. (Sun,) studied this question.