PASOTRON high-energy microwave source

The authors describe the operation and performance of a high-energy microwave source called the PASOTRON (plasma-assisted, slow-wave oscillator). The PASOTRON is a unique combination of a novel electron gun, and plasma-filled slow-wave structure which creates a source capable of generating 100- mu s-long RF pulses maintained at power levels of a few megawatts without the use of any magnetic focusing fields. A Hughes hollow-cathode-plasma electron gun is used to produce long, high-power beam pulses from which energy is efficiently extracted and converted into electromagnetic radiation. The authors present results which show that RF output power is in the 1-to-5 MW range, for RF pulse lengths up to 120 mu s from a PASOTRON tube designed to operate in the C-band frequency range. The integrated RF energy per pulse is up to 500 J, and the electron-beam to microwave-radiation power-conversion efficiency is approximately 20%. Instantaneous bandwidth measurements confirm that, for the long RF pulse duration, the PASOTRON's oscillation center frequency is maintained in a narrow line <3 MHz.<>