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Description
Cylindrical waveguides with a two-layer metal-dielectric wall are widely used in experimental work on splitting beams of charged particles and in designing slow-wave devices. The manufacture of a sufficiently long section of a two-layer (usually copper-dielectric) waveguide is associated with significant technical and financial difficulties. Meanwhile, as shown in the article, many of the characteristic properties of a two-layer waveguide used in the above-mentioned works are possessed by a single-layer dielectric waveguide. In order to demonstrate this, explicit expressions are derived for the longitudinal and transverse impedances for the limiting values of the conductivities of the outer metal wall of the waveguide: infinitely large conductivity (perfectly conducting outer wall) and zero conductivity (single-layer dielectric waveguide with a vacuum outer environment). It is shown that in the case of longitudinal impedance, the formulas for the mentioned limiting cases completely coincide, and in the case of transverse impedance, the coincidence takes place for high frequencies, which is especially important when considering radiation in the terahertz frequency range. Using specific graphical examples, the proximity of the impedance characteristics of copper-dielectric and single-layer dielectric waveguides is shown. In some, quite important cases, the characteristics of the latter qualitatively exceed the indicators of the copper-dielectric waveguide. The main result of the article is the justification of the functional interchangeability of copper-dielectric and single-layer dielectric waveguides in implementing a wide range of accelerator physics problems.
