Experimental investigation of a broadband dielectric-loaded gyro-TWT amplifier

The bandwidth of a gyrotron travelling wave amplifier has been broadened by incorporating a dielectric-loaded interaction waveguide to reduce the circuit's dispersion. This proof-of-principle experiment was designed for the X-band frequency range and operates in the fundamental mode of a rectangular waveguide loaded with dielectric Macor. The amplifier is zero-drive stable and demonstrates a peak output power of 55 kW, 11% efficiency, 27 dB saturated gain with an unprecedented untapered gyro-TWT constant-drive bandwidth of 11% and a saturated bandwidth of 14%. Its performance can be further enhanced by reducing the beam's axial velocity spread as shown by previous simulation studies.