Tapered interaction gyro-TWA experiments

A series of low power tapered interaction gyrotron traveling-wave amplifier experiments at K
a
band (26.5-40 GHz) have been performed with a linearly tapered wall rectangular waveguide operating in the fundamental TE
10
^□
mode and a profiled magnetic field. An adjustable solenoid system was used to allow local trimming and a wide variety of magnetic field profiles. An instantaneous wideband gain of ~ 28 percent was achieved with the magnetic field adjusted to approximately grazing synchronism along the circuit. A profile in which the magnetic field was adjusted significantly above grazing, produced gain over a frequency span of ~ 15% introduces the possibility of a wideband amplifier configuration in which only the magnetic field is tapered.