Design Approach of Inverse Magnetron Injection Gun for 240 GHz Gyrotron for Plasma Fusion

Gyrotron is a high power microwave source widely used for electron cyclotron resonance heating (ECRH) and plasma stabilization through the localized current drive (CD) in the magnetically confined plasma. The magnetron injection gun is the most decisive part of any gyrotron as the RF power and efficiency of the device directly depend on the quality of gyrating electron beam. An inverse magnetron injection gun (IMIG) is designed for 240 GHz, 1MW gyrotron operated at TE46,17 mode and presented here. Selection of the inverse magnetron injection gun refers the possibility to insert the large emitter ring (for large beam current and beam radius) without increasing the bore radius of the magnet while this is not possible with conventional MIG (Magnetron Injection Gun), which further reduces the overall cost of the device. The electron beam parameters and various electrical and geometrical parameters are optimized as per the requirements at the interaction cavity. 2.5 D electron beam optics code EGUN is used to simulate the electrode geometry.