Operation of a 20-T superconducting magnet with a large bore

In March 1993, the highest magnetic field of 21.1 T was generated in a 50 mm diameter clear bore. It was accomplished by using a 20 T superconducting magnet with a large bore developed at the National Research Institute for Metals. In order to obtain higher fields over larger spaces, three Wind & React coils having identical winding parameters were fabricated as the innermost coils. By removing a stainless steel bobbin from the second coil, improvement of training behavior as well as enlargement of a clear bore diameter could be achieved. A bobbin was also removed from the third coil. It was wound with a newly developed conductor and recorded the field of 21.1 T.