A SPLIT MAGNET SYSTEM FOR QUASI-OPTICAL GYROTRON

A split superconducting magnet system has been built for use in a 175 GHz quasi-optical gyrotron for generation of high frequency power. The quasi-optical gyrotron, an alternative to the more conventional micro wave cavity gyrotron, may have advantages or even be necessary to achi eve the performance objectives for future plasma heating applications. The design resolved such important problems as ohmic heating of the c ross bore shields, mirror separation, and the magnetic mirror effect. The superconducting magnet consists of four Nb Ti coils. The cross bor e inner diameter is 56 mm. The cavity wall inclination is 10 degrees t o the horizontal axis. The main bore diameter is 143 mm. During the fi rst test, the magnet produced a 6.2 T field in the cavity with uniform ity better than 1%. The split design accommodates the resonator withou t interference with the resonator mode and unacceptable ohmic heating. Three current leads allow different currents to be introduced in the winding halves thus tilting the central magnetic field. The magnet has retractable current leads. The vacuum space of the cryostat is good t o st least similar to 10(-8) Torr and is free of oils and other hydroc arbons.