A 100 GHz gyrotron—results and future prospects

High efficiency (~40%) gyrotrons have been built by other workers in the frequency range from 28–70 GHz with output powers of 200 kW or more in pulses of 0 · 1–1 second, and some have operated in CW. In this frequency range, we have developed a single cavity oscillator at 35 GHz. Table 2 includes a summary of results obtained with this tube. Of course, it is required to produce tubes for higher frequencies and higher powers. According to the laws of electron dynamics and electromagnetics in vacuo, simple scaling in frequency requires a scaling in dimensions with invariant voltages, currents, and powers. Most quantities in that case are not invariant, e.g. electric field E ~ƒ, magnetic induction B ~ ƒ, current density J ~ ƒ, power density J ~ƒ2, power density due to electron impact (Pel/S) ~ƒ2,Rf ohmics losses, assuming classical skin effect ~ƒ5/2, and losses in dielectric present complex variation with frequency depending upon their nature. This type of scaling cannot be applied indefinitely to higher frequencies because of the limits of the materials.