Analysis of residual gas by high-resolution mass spectrometry during helium glow discharge cleaning in JT-60U

Hayashi, Takao; Kaminaga, Atsushi; Arai, Takashi; Sato, Masayasu

The residual gas analysis has been conducted by high-resolution mass spectrometry which can discriminate between D and He gas species during helium glow discharge cleaning (He-GDC) in JT-60U in order to investigate the effect of He-GDC. The residual gas analyzer was able to distinguish between D and He peaks during He-GDC. Since the He-GDC started, the partial pressure of D gas increases with time and reached its highest pressure (3.8 10 Pa), which is about ten times larger than that before the He-GDC (3.5 10 Pa). The total amount of D, which was released during the He-GDC (7 hours), was evaluated as 4 Pa m. The pressure of D (5.7 10 Pa) about 7 hours after the He-GDC (7 hours) is significantly lower than before the He-GDC, which indicates the He-GDC is effective to remove the deuterium from plasma facing components.