Simulation of Thermal Characteristics for Helical Slow-Wave Circuit of TWT

A simulated model has been established to calculate the temperature of helical slow-wave circuits accurately. The Finite Element Method software ANSYS was used to analyze the thermal distortion of the helical slow-wave circuit of TWT. The thermal analysis results show the thermal stress makes helical tape concave at the positions contacting with rods and convex at the part between the two rods, and the expansion of the helical tape width and thickness are very small and could be ignored. The effect of thermal strain in helical slow-wave circuit on TWT cold-test characteristics was analyzed in detail. The quasi-periodic boundary conditions in the computer code MAFIA was employed to determine the effect on dispersion and on-axis interaction impedance of helical slow-wave circuit. With the helix temperature getting higher, the phase velocity decreases obviously and the interaction impedance varieties slightly.