ITER Microwave Waveguide Inspection System

Abstract

This project was commissioned to develop a nondestructive inspection system that locates defects in the interior corrugated wall of cylindrical waveguides manufactured for the ITER Electron Cyclotron Heating (ECH) system. The waveguide is designed to carry 170 GHz microwave energy at a power level of about 2 MW. The waveguides incorporate interior corrugations to lower the HE11 mode attenuation to below that of the TE11 mode in smoothwalled circular waveguides of comparable size. The HE11 is the preferred propagation mode. Manufacturing processes for long sections of the corrugated waveguide require significant attention to detail to minimize defects and deleterious variations in the interior dimensions especially as related to the corrugations. The inspection system will be applied in a pass/fail procedure after the waveguide is finished. It is possible that inspections can be performed prior to final finishing steps. It is also possible by localizing the defects that some repairs can be made. The inspection may also reveal the kind of defect and, therefore, the cause of the defect. This report describes inspection requirements, system description, use of the system, and some measurement results.