Gyrotron experiments employing a field emission array cathode

Summary form only given, as follows. The design and operation of a field emission array (FEA) cathode for a millimetre wave gyrotron are presented. The FEA chip employed achieved 10 mA reproducibly while operating in the environment of a gyrotron, namely in a vacuum of 1/spl times/10/sup -8/ mbar at voltages of up to 40 kV. New methods are presented of mounting such FEA chips involving the shielding of the micron devices from voltages of up to 40 kV, as experienced in a microwave device. The design parameters of the FEA gun were similar to those of a magnetron injection gun with cathode radius 12.5 mm and slope angle 4/spl deg/. An electron beam current of up to 100 mA was achievable from the FEA gyrotron cathode. An electrically isolated, fibre-optic, 10-channel control unit was developed to allow individual control of each chip. Electron beam powers of /spl sim/1 kW were measured from the FEA cathode. To obtain oscillation, cavity inserts were employed in the electron beam-microwave interaction region to increase the cavity quality factor. Results are presented which verify the gyrotron interaction from the novel FEA cathode.