Recent high field Nb3Sn tape solenoids of large radial access

Large radial access in a high field solenoid magnet is important in applications of current interest. Several magnets produced recently provide examples of two types of large radial access split solenoids. The variable gap split magnet provides flexibility in allowing fields above 15 T in a "closed position" without radial access and, in the same magnet, allowing fields above 13 T with radial access sufficient to test large cryostable conductors. The requirement of large solid angle view of the central field region is met with a second type of split magnet incorporating conical windings. The structural support of the windings above large radial ports is a critical design issue. Procedures developed recently for the use of cryogenic strain gauges in magnetic field environments have been adopted to measure support stresses. The strain gauge procedure, measurement results, and comparison with analysis is presented.