Erosion and Re-deposition of Plasma-Facing material in Long Duration Discharges on TRIAM-1M

Properties of erosion and re-deposition of plasma-facing material in TRIAM-1M has been studied. The thickness of the re-deposited layer was estimated using the optical reflectivity on the sapphire window. Oxygen impurities should dominate the erosion and deposition properties of the plasma-facing wall as well as the hydrogen retention　property of the co-deposited layer.