Very low frequency oscillations of heat load and recycling flux in steady-state tokamak discharge in TRIAM-1M

Hideki Zushi (1) , Mizuki Sakamoto (1) , Kazuaki Hanada (1) , Yasuo Matsuo (2) , Tatsuru Kuramoto (2) , Tomoya Sugata (2) , Nobuyuki Maezono (2) , Hoshika Hirosi (2) , Atsusi Iyomasa (1) , Keisuke Sasaki (2) , Kazuo Nakamura (1) , Kohnosuke Sato (1) , Hirosi Idei (1) , Shoji Kawasaki (1) , Hisatosi Nakashima (1) , Aki Higasijima (1) , Makoto Hasegawa (1)

1 RIAM - Research Institute for Applied Mechanics [Fukuoka]
2 Interdisciplinary Graduate School of Engineering Sciences

Plasma wall interaction (PWI) driven relaxation oscillations are investigated in the steady state discharge for 5 hours. The oscillation frequency was about 10-3 Hz and each perturbation lasted for ~ 300 s. The heat load, recycling flux and impurity influx were varied from a few % to several tens of % . The largest variation of 70% was seen on the Mo XIII, although the influx of Mo I was only 20%. Although the input rf power is kept constant during the discharge, the coupling between the rf and plasma was increased by ~ 10%. The current drive efficiency is decreased by 24 % in spite of current ramp. The toroidal and poloidal profiles of the recycling flux were also changed. During the last relaxation phase, the plasma was finally terminated. The current reduction (> 4 kA) was not recovered by intense local perturbation of the recycling superposed on the relaxation oscillation.

Mots clés: PWI; tokamak; steady state operation

Domaines: Physique des plasmas [physics.plasm-ph]

Hideki Zushi, Mizuki Sakamoto, Kazuaki Hanada, Yasuo Matsuo, Tatsuru Kuramoto, et al.. Very low frequency oscillations of heat load and recycling flux in steady-state tokamak discharge in TRIAM-1M. 2004. ⟨hal-00001875⟩