Cyclotron autoresonance masers— recent experiments and prospects

The cyclotron autoresonance maser (CARM) is considered as a possible source of millimetre and submillimetre coherent radiation with large average power. At present the most acute problems of CARM creation are the formation of a curvilinear relativistic electron beam with a small spread of velocities and mode discrimination. Two kinds of electron-optical systems can be used: a magnetron-injection gun (gyrotron type) and a quasi-Pierce gun with undulator (kicker). Undesirable gyrotron modes in CARM can be suppressed by choosing a proper operating regime. The main schemes of electron-optical and electrodynamic systems were verified in preliminary experiments with CARM. In short pulse operation a power of 30-50 MW was obtained at wavelengths of 4-4 mm and 6 mm with an efficiency 8-10%. Calculations show that CARM with average power 1-10MW at 1-2 mm is realizable.