Superconducting coil, superconducting device, and liquid epoxy resin composition

A superconducting coil comprising:

• a winding frame;
• a superconducting wire wound around the winding frame and having a first region and a second region facing the first region in a radial direction of the coil;
• and
• a resin layer located between the first region and the second region and including particles, an epoxy resin surrounding the particles, and a region existing between the particles and the epoxy resin, wherein
• an average particle diameter of the particles is equal to or more than 1 μm and equal to or less than 5 μm,
• a volume ratio of the particles in the resin layer is equal to or more than 50% and equal to or less than 66%,
• the region has a nitrogen atom concentration higher than a nitrogen atom concentration of the epoxy resin, and
• the particles are silica particles.

A superconducting coil comprising:

• a winding frame;
• a superconducting wire wound around the winding frame and having a first region and a second region facing the first region in a radial direction of the coil;
• and
• a resin layer located between the first region and the second region and including particles and an epoxy resin surrounding the particles, the particles being surface-treated with a silane coupling agent containing a phenylamino group, wherein
• an average particle diameter of the particles is equal to or more than 1 μm and equal to or less than 5 μm,
• a volume ratio of the particles in the resin layer is equal to or more than 50% and equal to or less than 66%, and
• the particles are silica particles.

A superconducting coil comprising:

• a winding frame;
• a superconducting wire wound around the winding frame and having a first region and a second region facing the first region in a radial direction of the coil;
• and
• a resin layer located between the first region and the second region and including particles and an epoxy resin surrounding the particles, wherein
• an average particle diameter of the particles is equal to or more than 1 μm and equal to or less than 5 μm,
• a volume ratio of the particles in the resin layer is equal to or more than 50% and equal to or less than 66%,
• the resin layer has an absorption peak in a region of 580 nm or more and 630 nm or less in absorption spectrophotometry by ultraviolet-visible spectroscopy, and
• the particles are silica particles.