Simulation of Slowwave Spiral Structures Based on Analytical Model

The authors of the article consider decelerating structures made of homogeneous material, which have a periodic structure in space. Such systems are used to concentrate the energy of high-frequency electromagnetic waves in order to increase the sensitivity of devices designed for their registration, increase the efficiency of the interaction of a beam of free electrons with a slowed electromagnetic field, for the manufacture of structural elements in waveguide devices, and for generators of monochromatic radiation in the terahertz and optical ranges (effect Vavilov-Cherenkov radiation). The parameters of the wave process are studied on the basis of an exact analytical solution based on the cylindrical Bessel and Hankel functions for a decelerating system with axial symmetry in the form of a spiral. To obtain numerical solutions, the optimization problem of the system of nonlinear equations of a complex variable is solved. The conducted studies establish the relationship between the transverse and longitudinal wave numbers and the attenuation coefficient of the electromagnetic wave. A detailed analysis of the solutions of the equation showed that, in addition to the classical solution that determines the surface wave, other solutions are possible for which the concentration of the electromagnetic field inside the structure is higher.