Direct measurement of broad spectral electromagnetic wave energy generated by an intense relativstic electron beam

A direct determination is made of the total power radiated in a single pulse, F P (ω) dω, by an intense relativistic electron beam cyclotron maser configuration as a function of applied magnetic field. The existence of other possible instabilities over a broad spectral range notwithstanding, the total output is dominated by the maser instability occurring at the relativistic cyclotron resonance magnetic field. The results for two different anode-cathode spacings, corresponding qualitatively to cold and warm beam conditions, are presented and compared. A possible explanation accounting for the existence of high power noise radiation at low magnetic fields for the warm beam case is discussed.