Fast-wave Devices came into prominence around sixties, when these devices were invented by Russian Scientists. The most common and popular device among fast-wave devices is Gyrotron, which is being used for various applications including in thermo nuclear reactors. International Thermonuclear Experimental Reactor (ITER) is a major international project, requiring 1.0 MW (CW) class Gyrotrons at 170 GHz. All out efforts are being made around the globe for developing the required Gyrotrons. In India, the activity has started quite late. However, now with the support of DST, New Delhi and CSIR, New Delhi multi-institutional projects have been launched in respect of 42 GHz, 200 kW (long pulse) and 120 GHz, 1.0 MW (long pulse) Gyrotrons, ultimately aiming for 170 GHz, 1.0 MW (CW) Gyrotrons.