2012 Volume 7 Pages 1205154
High power and high efficiency operation of 77 GHz gyrotrons was achieved by the stepwise raising of the anode voltage. In particular, a stable MOU output power of 1.8 MW was obtained for 1 s. The effect of beam-charge neutralization on the oscillation characteristics was examined. The intended beam acceleration voltage was not initially reached due to the space-charge effect but was achieved over time through the charge neutralization process. By applying the stepped anode voltage, the gyrotron operational parameters were able to be optimized for the sufficiently accelerated electron beam, leading to the improvement of the output power and the electric efficiency.