The ITER Electron Cyclotron Heating (ECH) system consists of transmission lines made up of individual sections of evacuated, aluminum, circularly corrugated waveguides. The high-intensity beam of electromagnetic radiation, necessary for plasma heating, heats the waveguides and other components in the transmission lines causing the lines to expand and contract. To maintain the structural integrity and the required straightness in the transmission lines, expansion units have to be incorporated into the ECH transmission line system.

Calculations of several models of expansion units have been completed to evaluate the effect of the design and materials on the functionality of the expansion unit. Models have been evaluated assuming three different expansion ranges and several different materials.