CYCLOTRON-RESONANCE MASER EXPERIMENT IN A NONDISPERSIVE WAVE-GUIDE

A cyclotron-resonance maser (CRM) oscillator experiment in which a spi raling electron beam interacts with a transverse electromagnetic wave in a nondispersive waveguide is presented, The experiment employs a lo w-energy (<5 keV) low-current (<1 A) electron beam in a two-wire (Lech er type) waveguide, The microwave output frequency is tuned in this ex periment by the axial magnetic field in the range 3.5-6.0 GHz, A secon d harmonic emission is observed similar to 7 GHz. CRM theory shows tha t in a free-space TEM-mode interaction, the gain might be canceled due to the equal and opposite effects of the axial (Weibel) and the azimu thal bunching mechanisms, This balance is violated in the large transv erse velocity regime (V-perpendicular to much greater than V-z) in whi ch our experiment operates, The tunability measurements of the CRM osc illator experiment in the nondispersive waveguide are discussed in vie w of the CRM theory.