Full 3-D ALEGRA simulations were used to understand the shielding effects of copper tubes in direct comparison to copper cups with the magnetic field applied along the axis of the shapes and at 30? from the axis. Copper tubes with a diameter of 50 mm, a length of 80 mm, and wall thickness of 1 mm were investigated to determine the time the tube shielded an axial 0.25 T field applied as a step function. A variety of locations within the tube and near the tube were analyzed. The field was then applied at an angle of 30? from the axis to investigate shielding effectiveness. One end of the tube was then capped, making a cup shape, and identical simulations were repeated. While this produced nontrivial changes at the edges, the shielding effectiveness at the center of the shape was not significantly affected by either the applied field angle (up to the 30° investigated) or the capping of one end of the tube. Shielding effects and focusing of the field due to induced currents in the copper can create a considerable impact on field sensors and the detection of moving conductive particles.
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