Method of cleaning the first wall and a thermonuclear plasma device having cleaning function

Purpose: To obtain a high cleaning effect with no need of electrode insertion by irradiating atomic hydrogen to the wall of a plasma container, reacting it with substances as plasma impurities to form evaporizing compounds, and discharging them out of the system through a vacuum device. Constitution: When hydrogen gas at about 10-5 torr is introduced to an atomic hydrogen generator and heated to about 1500 - 20000C, hydrogen atoms are formed. They are sent into a torus type plasma container, jetted out from an atomic hydrogen inlet and supplied to the inner surface of a molybdenum liner. The inside is thus cleaned and steam, methane or the like resulted on the surface of the liner are discharged out of the system through a high vacuum device. The cleaning effect for the liner can be monitored by an impurity gas monitor. This can provide a high cleaning effect with not need for the insertion of special electrodes and eliminating re-adsorption of impurities. (Seki, T.)