Abstract
An Auger Electron Spectrometer (AES) was employed to determine the secondary electron yield of various wall materials. The yield is related to the surface composition which is modified by surface treatments including baking, argon ion etching, exposure to the air, etc. We applied these results to decrease the yield of inner wall of the JT-60 RF waveguides, and showed that the yield monitoring is an effective way for estimating the degree of surface cleaning of the wall materials.