Performance of a 3D Magnetic Inverse for Fault Localization
Performance of a 3D Magnetic Inverse for Fault Localization
Monday, November 17, 2025: 10:40 AM
3 (Pasadena Convention Center)
Summary:
We describe results from a new magnetic inverse routine which processes images of the z-component of magnetic field from multi-layer current paths to obtain the path that the current follows in 3D. To evaluate performance, we processed hundreds of simulated images with 1-3 layers and 1-10 segments for which the true values of the path parameters were accurately known. Each image included random noise of 0.1 nT per pixel (typical of the MAGMA SQUID imaging system). A range of typical path and image parameters were used, including sample-sensor separations z between 0.02 mm and 1 mm, segment lengths from 0.05 mm to 2 mm, and current between 0.1 mA and 2 mA, yielding images with S/N between about 106 and 2x1012. We find that the vertical and lateral resolution are comparable, proportional to the depth z of the current path, and inversely proportional to the total signal-to-noise ratio (S/N) of the image. For S/N>108, the vertical and lateral resolution was typically better than z/1000. Since audio frequency magnetic fields can penetrate unhindered through opaque insulating or thin conducting layers, this implies sub-micron vertical and lateral localization of circuit paths is achievable at depths z < 1 mm.
We describe results from a new magnetic inverse routine which processes images of the z-component of magnetic field from multi-layer current paths to obtain the path that the current follows in 3D. To evaluate performance, we processed hundreds of simulated images with 1-3 layers and 1-10 segments for which the true values of the path parameters were accurately known. Each image included random noise of 0.1 nT per pixel (typical of the MAGMA SQUID imaging system). A range of typical path and image parameters were used, including sample-sensor separations z between 0.02 mm and 1 mm, segment lengths from 0.05 mm to 2 mm, and current between 0.1 mA and 2 mA, yielding images with S/N between about 106 and 2x1012. We find that the vertical and lateral resolution are comparable, proportional to the depth z of the current path, and inversely proportional to the total signal-to-noise ratio (S/N) of the image. For S/N>108, the vertical and lateral resolution was typically better than z/1000. Since audio frequency magnetic fields can penetrate unhindered through opaque insulating or thin conducting layers, this implies sub-micron vertical and lateral localization of circuit paths is achievable at depths z < 1 mm.