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 microwave cavity gyrotron, may have advantages or even be necessary to achieve the performance objectives for future plasma heating applications. The design resolved such important problems as ohmic heating of the cross bore shields, mirror separation, and the magnetic mirror effect. The superconducting magnet consists of four NbTi coils. The cross bore inner diameter is 56 mm. The cavity wall inclination is 10/spl deg/ to the horizontal axis. The main bore diameter is 143 mm. During the first test, the magnet produced a 6.2 T field in the cavity with uniformity better than 1%. The split design accommodates the resonator without 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 to at least /spl sim/10/sup -8/ Torr and is free of oils and other hydrocarbons.<>