A high-power, traveling wave tube amplifier

High-power X-band traveling-wave tube amplifiers (TWTs) have been fabricated and tested. The tubes have gains ranging from 13 to 35 dB at 8.76 GHz and output powers ranging from 3 to 100 MW. The amplifiers are driven by the interaction of a slow space-charge wave, propagating on an electron beam, with an electromagnetic wave supported by the structure. The electron beam, which is produced from a magnetic-field-immersed field-emission cathode, has an energy of 850 keV, a current in the 1-kA range, and a pulse duration of 100 ns. The amplifiers are designed to operate as narrow-band devices in the TM₀₁ mode. A report is presented on the amplifier characteristics, and their performance is compared with calculated performance using conventional TWT theory. The scaling of the gain and bandwidth with the beam current are approximately as expected from theory, but the absolute magnitude of the gain is somewhat greater than expected