Heat flux and plasma flow in the far scrape-off layer of the inboard poloidal field null configuration in QUEST

Journal Article · Sat Aug 15 00:00:00 EDT 2015 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4928878· OSTI ID:22490062

Onchi, T.; Zushi, H.; Hanada, K.; Idei, H.; Hasegawa, M.; Nakamura, K.; Fujisawa, A.; Nagashima, Y.; Matsuoka, K.; Kuzmin, A.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Watanabe, O. ^[1]; Mishra, K.; Mahira, Y.; Tashima, S.; Banerjee, S. ^[2]; Nagaoka, K. ^[3]

---

1. RIAM, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan)
2. IGSES, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan)
3. National Institute of Fusion Science, Toki 509-5292 (Japan)

Heat flux and plasma flow in the scrape-off layer (SOL) are examined for the inboard poloidal field null (IPN) configuration of the spherical tokamak QUEST. In the plasma current (I{sub p}) ramp-up phase, high heat flux (>1 MW/m{sup 2}) and supersonic flow (Mach number M > 1) are found to be present simultaneously in the far-SOL. The heat flux is generated by energetic electrons excursed from the last closed flux surface. Supersonic flows in the poloidal and toroidal directions are correlated with each other. In the quasi-steady state, sawtooth-like oscillation of I{sub p} at 20 Hz is observed. Heat flux and subsonic plasma flow in the far-SOL are modified corresponding to the I{sub p}-oscillation. The heat flow caused by motion of energetic electrons and the bulk-particle transport to the far-SOL is enhanced during the low-I{sub p} phase. Modification of plasma flow in the far SOL occurs earlier than the I{sub p} crash. The M–I{sub p} curve has a limit-cycle characteristic with sawtooth-like oscillation. Such a core–SOL relationship indicates that the far-SOL flow plays an important role in sustaining the oscillation of I{sub p} in the IPN configuration.

• OSTI ID: 22490062
• Journal Information: Physics of Plasmas, Vol. 22, Issue 8; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ELECTRIC CURRENTS
HEAT FLUX
LIMIT CYCLE
MACH NUMBER
MAGNETIC SURFACES
NEUTRAL-PARTICLE TRANSPORT
PLASMA
PLASMA INSTABILITY
PLASMA SCRAPE-OFF LAYER
SAWTOOTH OSCILLATIONS
SPHERICAL CONFIGURATION
STEADY-STATE CONDITIONS
SUPERSONIC FLOW
TAIL ELECTRONS
TOKAMAK DEVICES