Design and Optimization of Superconducting Magnet System for 42.0-GHz Gyrotron

In the framework of the Department of Science and Technology (DST), Government of India, a 42.2-GHz 200-kW continuous-wave/long-pulse gyrotron is envisaged to be indigenously developed. This gyrotron shall employ superconducting magnets at the interaction region and warm coils for the gun and collector region. The Institute for Plasma Research is responsible for the overall design and fabrication of the magnet system along with the required housing cryostat and auxiliary support system. The design of the appropriate magnet system is currently under progress in accordance with gyrotron physics and engineering considerations. This requires a highly homogeneous spatial field profile as well as a very steep gradient as per the compression and velocity ratios between the emission and resonator regions. These aspects demand a very precise winding of the magnets as well as the collinearity of the magnetic axis with that of the beam axis. Several technological aspects, such as accurately designing and positioning of the magnet system in space, to optimize the required field profile have been taken up in the run up to realize a highly homogeneous and stable magnet system. Different design criteria for the theoretical optimization of magnet parameters and their spatial arrangement such that the required axial magnetic field profile can be achieved have been taken up. In addition, finite-element analysis (FEA) of the optimized magnet parameter is done, and the magnetic field profile is compared with the theory. The detailed design of the guiding magnet system, the optimization of coil parameters, and the FEA simulation for the validation of the optimized parameters are presented in this paper.