Design and fabrication of a 500 KV MIG gun for a 30 MW gyroklystron

A 500 kV magnetron injection electron gun, to be used in gyroklystron experiments, has been designed and constructed. This device represents a major milestone in gyrotron gun design, both in terms of its physical size and its operating voltage. The gun is designed for beam currents up to 200 A and operates at control anode voltages of 140 to 150 kV. The gun will be operated at pulse widths of 1 to 2 µS and repetition rates up to 10 pps. Computer simulations of the electrode geometry indicate that a perpendicular to parallel velocity ratio of 1.5 can be achieved over a wide range of beam parameters with axial velocity spreads of less than 10 %. Computer calculations predict electric fields of less than 100 kV/cm on the electrodes. Fabrication and processing of the gun required special techniques and procedures because of the physical size and high voltage requirements of the gun. At the present time the gun is ready for initial high voltage tests.