Validation Of An Accurate Three Dimensional Helical Slow Wave Circuit Model

Validation of an Accurate Three-Dimensional Helical Slow-Wave Circuit Model

Validation of an Accurate Three-Dimensional Helical Slow-Wave Circuit Model

The helical slow-wave circuit embodies a helical coil of rectangular tape supported in a metal barrel by dielectric support rods. Although the helix slow-wave circuit remains the mainstay of the traveling-wave tube (TWT) industry because of its exceptionally wide bandwidth, a full helical circuit, without significant dimensional approximations, has not been successfully modeled until now. Numerous attempts have been made to analyze the helical slow-wave circuit so that the performance could be accurately predicted without actually building it, but because of its complex geometry, many geometrical approximations became necessary rendering the previous models inaccurate. In the course of this research it has been demonstrated that using the simulation code, MAFIA, the helical structure can be modeled with actual tape width and thickness, dielectric support rod geometry and materials. To demonstrate the accuracy of the MAFIA model, the cold-test parameters including dispersion, on-axis interaction impedance and attenuation have been calculated for several helical TWT slow-wave circuits with a variety of support rod geometries including rectangular and T-shaped rods, as well as various support rod materials including isotropic, anisotropic and partially metal coated dielectrics. Compared with experimentally measured results, the agreement is excellent. With the accuracy of the MAFIA helical model validated, the code was used to investigate several conventional geometric approximations in an attempt to obtain the most computationally efficient model. Several simplifications were made to a standard model including replacing the helical tape with filaments, and replacing rectangular support rods with shapes conforming to the cylindrical coordinate system with effective permittivity. The approximate models are compared with the standard model in terms of cold-test characteristics and computational time. The model was also used to determine the sensitivity of various circuit...

Proceedings of the National Conference on Emerging Trends in Vacuum Electronic Devices and Applications

This book presents peer reviewed articles from the Conference on Vacuum Electronic Devices Applications (VEDA2024) held at Pilani in India. Like its previous editions, it focusses on new ideas and the latest developments in research and industry on topics like technologies for vacuum electron devices (VEDs) or Systems and Subsystems employing VEDs, RF, HPM, and THz Components, Devices & Systems, RF, MW & mm-wave, Antennas and EM Simulations, Materials, power systems and components for VEDs, High emission density cathodes for VEDs, Applications of VEDs, Future trends & competing technologies. It brings together scientists, industrialists, academicians, and research scholars to exchange ideas and present latest developments in the field.