Construction and tests of an injection electron gun for a 6.7 GHz monotron

We describe the construction and emission tests of an electron gun used to accelerate and inject a hollow electron beam into a cylindrical cavity to produce high-power microwaves at 6.7 GHz, a frequency suitable for communications, medical and industrial applications. In addition to the monotron components, a hard-tube pulser with three tetrodes in parallel is also discussed, able to generate negative high voltages up to 30 kV/20A from a positive DC charging power supply without using a floating switch.