Three-dimensional particle-in-cell simulations of a millimeter-wave reflex klystron activated by secondary electrons

We report a reflex klystron in which an embedded planar cold cathode is used to generate a secondary electron beam. By using secondary electron cathode with a high secondary electron yield, the number of secondary electrons can be sufficiently increased and adjusted to activate the reflex klystron. In our three-dimensional particle-in-cell simulations, oscillation of the device was demonstrated at 100 GHz when using a secondary electron cathode with a maximum yield of 20 while a primary electron beam with a current density less than 5 A/cm2 was irradiated to create secondary electrons. The current density of the primary electron beam is achievable with typical field emission cathodes if they are equipped with an electron beam focusing lens, and a maximum yield of 20 can be obtained if magnesium oxide is used for the secondary electron emission.