About possible theoretical approach in the linear theory of dielectric TWT and devices containing metamaterials

In this paper we present overview of devices using a dielectric as a slow-wave structure. There are increased focus on consideration of dielectric Cherenkov maser (DCM) and resistive- wall amplifier (RWA). This type of devices may be advance in THz range. The principle of the DCM operation is described by two-dimensional planar model with the indication of main advantages of this device. In particular, there are sufficiently large gain and possibility of great tunability range (by varying the beam voltage). And furthermore, main problems and the possibility of their solving with the use of metamaterials are provided in the article. A dispersion relation for planar DCM is obtained by using small signal theory, which was limited to TM modes. Brief description of easitron is presented, which was the first device using metamaterial. Resistive-wall amplifier is a high-power design with a large bandwidth. One of the main shortcomings of RWA is difficulties of manufacturing. The analysis of this device using the one-dimensional model with resonating input and output elements, in this regard was also highlighted. A dispersion equation and gain factor expression for this case are obtained. Dependence between phase factor (gain factor) and characteristics of the medium are constructed.