A conductively cooled superconducting Nb3Sn magnet system has been designed
and tested that employs a two-stage 4 K pulse tube cooler. The Nb3Sn coil
has a clear bore of 11 mm and a mass of 2.6 kg, High-T-c current leads are
used to reduce the heat leak to the 4 K stage. After a cooling time of abou
t six hours the 2(nd) stage and the magnet surface attained stationary temp
eratures of 3.4 K, and 4.1 K, respectively. The 1(st) stage cold head was t
hen at 54 K, The magnet coil was repeatedly charged with a current of 120 A
corresponding to a central field of 2.8 T, Stable operation of the energiz
ed system has been demonstrated for 25 hours.