1 Ghz Modulation of a High-Current Electron-Gun

Measurements on a triode electron gun operated with grid modulation at 1 GHz are presented in this article. The gun has a miniaturized cathode-grid spacing of 0.15 mm. The network used for matching the rf source (a solid-state amplifier) to the cathode-grid assembly, is discussed in detail. The bunch length is measured by means of a capacitive pick-up probe and a 20 GHz sampling oscilloscope. Bunches with a duration of 280 ps and a charge of 220 pC have been obtained at 100 W of rf input power. The normalized beam emittance is around 30-pi mm mrad.