Resistive insert magnet for a 37.3-T hybrid magnet

A resistive insert magnet consisting of Bitter-type coils was fabricated, incorporated into the 400-mm bore of the superconducting outsert, and tested under a backup field of 14.2 T. This hybrid magnet generated a total field of 37.3 T in the center of a 32-mm room-temperature bore. At this magnetic field, the operating current of the resistive insert magnet was 33.25 kA at a voltage of 431 V. This insert magnet is divided into three coaxial coils. The bitter plates of the two inner coils are made of hard-worked Cu-Ag plates, and those of the outermost coil are made of GlidCop AL-25. The thickness of the plates used in the two inner coils was 0.84 mm, and the 0.2% proof stress in the direction parallel to the roll work was about 800 MPa at 375 K. This temperature is designed to be the maximum of the innermost coil at 37.3 T. Elongated cooling channels were punched in a staggered formation in these plates. The flow rate of the cooling water was 0.141 m(3)/s at the maximum field. Regular operation up to 35 T started from June 2000 at the Tsukuba Magnet Laboratory. (C) 2001 Elsevier Science B.V. All rights reserved.