Millimeter wave generation in a plasma-filled slow wave device

A plasma-filled slow wave device, e.g., a backward wave oscillator (BWO), offers high efficiency for the generation of TM waves around 10 GHz, by a relativistic electron beam. A large-amplitude TM mode can parametrically drive a millimeter wave unstable by coupling it to a negative energy beam space charge mode. The frequency of radiation is maximum when it propagates in the TM01 mode. In the Raman regime of operation the growth rate of instability scales directly as one-fourth power of beam density and inversely as 21/4 power of relativistic gamma factor. The nonlocal effects reduce the growth rate.