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Plasma and Fusion Research

Volume 9, 3402093 (2014)

Regular Articles

Analytical Solution of High βp Equilibria with Natural Inboard Poloidal Null Configuration Obtained in the Spherical Tokamak QUEST
Kishore MISHRA1), Hideki ZUSHI2), Hiroshi IDEI2), Saya TASHIMA1), Santanu BANERJEE1), Makoto HASEGAWA2), Kazuaki HANADA2), Kazuo NAKAMURA2), Akihide FUJISAWA2), Yoshihiko NAGASHIMA2), Keisuke MATSUOKA2), Arseny KUZMIN2), Takumi ONCHI2) and QUEST Team
1)
IGSES, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
2)
RIAM, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
(Received 10 December 2013 / Accepted 22 April 2014 / Published 4 July 2014)

Abstract

High βp (εβp ∼ 1) equilibria obtained in a ECW heated Ohmic plasma is investigated using a simple analytic solution of Grad-Shafranov equation. The formation of a natural inboard poloidal null associated with high βp is explained consistently by high diamagnetism and negative triangularity. As βp is increased, the poloidal null point penetrates further into the vacuum vessel, which is qualitatively explained by the analytic model. Transition from inboard (high field side) limiter bound to the natural divertor configuration is associated with a reduction of the edge safety factor without appreciable enhancement of MHD activities. Such a scenario is also addressed successfully with the model.

Keywords

tokamak plasma equilibrium, Grad-Shafranov equation, high beta plasma, natural divertor

DOI: 10.1585/pfr.9.3402093

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This paper may be cited as follows:

Kishore MISHRA, Hideki ZUSHI, Hiroshi IDEI, Saya TASHIMA, Santanu BANERJEE, Makoto HASEGAWA, Kazuaki HANADA, Kazuo NAKAMURA, Akihide FUJISAWA, Yoshihiko NAGASHIMA, Keisuke MATSUOKA, Arseny KUZMIN, Takumi ONCHI and QUEST Team, Plasma Fusion Res. 9, 3402093 (2014).