A method study on modeling and analysis of RF interference shielding materials for SQUID-TEM system

The superconducting quantum interference device (SQUID) significantly enhances the detection depth and resolution of transient electromagnetic (TEM) systems. However, in unshielded and complex field environments, SQUID sensors are highly susceptible to radio frequency (RF) interference, which can result in flux-lock loss and measurement failure. The idea of using shielding for a SQUID is a well known fact for many years. However, the selection and parameters of the shielding materials have not been investigated in detail. We first introduce the Schelkunoff's electromagnetic shielding theory to analyze the relationship between radiation sources and reflection loss. Then, the forward modeling method for calculating the magnetic field generated by a magnetic dipole is then presented, followed by an analysis of the relationship between magnetic field amplitude and frequency variations. A multi-interference source shielding model was established using COMSOL Multiphysics. By varying the direction and position of the radiation sources, the effectiveness of the shielding structure was verified. This article proposes a modeling and analysis method for shielding materials against RF interference based on SQUID-TEM system to ensure its proper operation in complex field environments.