The research electromagnets at the National MagLab, whether made with copper-silver bitter plates or with superconductors, are coils that are a few feet long and hollow in the middle. That empty space is called the bore, and that’s where the magnetic field generated by the electricity running through the coil is the strongest. That is also where scientists put their experiments to discover information revealed by those strong fields. In the magnetic resonance imaging (MRI) machines used in hospitals, those bores are relatively wide: After all, a person needs to fit in there! In the research magnets used at the National MagLab, however, bores are typically far narrower — ranging from 10 to 105 mm (about 0.4 inches to 4 inches). When you make the bore wider, you sacrifice magnetic field strength, and scientists value strong fields over space. Because space is so tight, the experiments have to be very small, especially since most of that area is taken up by a probe, the fancy stick used to insert a sample into the magnet bore and collect measurements.
Science advisor: Jack Toth