Some recent progresses on electron cyclotron maser research

Abstract

Over a span of five decades, the electron cyclotron maser (ECM) has undergone a remarkably successful evolution from basic research to a poweiful millimeter, sub-millimeter, and THz wave generator called the gyrotron, while continuously being enriched by major advances. Below we discuss the ECM principle and its significance, followed by an overview of recent progresses made in two specific areas: THz gyrotron oscillators and millimeter-wave gyro-TWT ampltfiers. Topics �f the talk will include selected examples of device performances, ongoing/potential applications, and relevant physics issues.Each class of vacuum electronic devices is distinguishable by its characteristic bunching mechanism to convert an electron current from DC to AC. The ECM interaction [1][2][3][4] features a simple relativistic bunching mechanism. As shown in Fig. 1, in an applied DC magnetic field (Ba) andin the presence of a perpendicular RF electric field, the relativistic cyclotron frequency (Qc) decreases (increases) for energy-gaining (losing) electrons, which results in electron bunching along the cyclotron orbit. The ECM interaction takes place in a smooth fast-wave structure, as well as allowing the resonant excitation of a very high order mode (Fig. 2). It can thus generate output powers orders of magnitude greater than previously achievable. gain energy, eB � Q c = � azimuthal / bunching .