STUDY OF WAVE-GUIDE RESONATORS FOR FEL OPERATING AT SUBMILLIMETER WAVELENGTHS

Theoretical investigations of waveguides for FEL operating at submilli meter wavelengths were made. Several types of overmoded waveguides, i. e. rectangular, circular, parallel curved plates waveguide and metal-d ielectric waveguide, were studied in order to achieve the best gain/lo ss ratio in FEL operation. Gain calculations were made in the low gain regime. Waveguide ohmic losses were calculated taking into account th e anomalous skin effect and the influence of surface roughness. Numeri cal calculations made for the parameters of the Israeli tandem electro static FEL show that a parallel curved plates waveguide and a metal-di electric waveguide provide good gain/loss ratios up to frequencies of the order of 1000 GHz (while conventional rectangular and circular wav eguides do not).