High-frequency electromagnetic modes in a dielectric-ring loaded beam tunnel

A numerical code (PERIODIC-HYBRID) is developed for the calculation of the dispersion relation, the electromagnetic field components, and the quality factor of a dielectrically loaded, periodically corrugated gyrotron beam tunnel. The Floquet theorem is used to express the fields in the vacuum region, and an eigenfunction expansion is employed in each dielectric indentation. The boundary conditions imposed at the interface lead to a linear system of equations, which is appropriately truncated for the numerical implementation. The code has been benchmarked, and the results have been interpreted as the product of coupling between cavity and waveguide modes.