Long Duration Operational Characteristics of the First Indian 42-GHz, 200-kW Gyrotron

Institute for Plasma Research (IPR) has indigenously developed the magnet system appropriate for a 42.2-GHz 200-kW continuous-wave/long-pulse gyrotron in a multi-institutional collaboration sponsored by the Department of Science & Technology, Government of India. The Gyrotron Magnet System (GMS) consists of a resistive gun magnet coil, superconducting cavity magnet coil, and three resistive collector magnet coils. The experimental validations of performance and stability of the magnet system in long-term operational scenarios has been elaborated in this paper. The Gun Magnet and the Collector magnets are fabricated from OFHC copper strands and oil/air cooled, whereas the cavity magnet is NbTi strand wound and helium bath cooled inside a low loss cryostat. The entire magnet system has been charged to their nominal transport current values and validated for long duration operation both in normal and off-normal scenarios. The desired field homogeneity and optimized positioning of individual magnets have been established from these experiments. The field at various radial positions is established within ±5% along the z-direction. GMS has been further successfully validated toward its performance with respect to the gyrotron beam guiding requirements.