Development of the 19 T high field magnet system

A high field magnet system, up to 19 tesla at 1.8K, with magnet bore of 75mm was developed. The magnet consists of [Nb.sub.3]Sn solenoids (3 sections) and NbTi solenoids (2 sections). A Liquid helium vessel is divided into two parts (4.2K upper part and 1.8K lower part) by a fiberglass reinforced plastics separator. The central field is 17 tesla at 4.2K with normal liquid helium and 19 tesla at 1.8K with pressurized superfluid helium. This magnet can be operated in persistent mode and the field stability at that time is less than 10ppm/hour. The field homogeneity is better than 0.1% at 50 mm sphere volume. The stored energy is about 3MJ. A small refrigerator was installed on the top flange of the cryostat to reduce the evaporation rate of liquid helium and to maintain the superconducting magnet at low temperature while pausing. This system is used for the measurement of critical current and other physical properties of superconducting wire and other materials such as high Tc superconductors.