Speaker
Kazuo Nakamura
(Nuclear Fusion Dynamics)
Description
In the present RF-driven (ECCD) steady-state plasma on QUEST (Bt = 0.25 T, R = 0.68 m, a = 0.40 m), plasma current seems to flow in the open magnetic surface outside of the closed magnetic surface in the low-field region according to plasma current fitting (PCF) method. The current in the open magnetic surface seems due to orbit-driven current by high-energy particles in RF-driven plasma. So based on the analysis of current density profile based on the orbit-driven current, plasma equilibrium is to be calculated.
High energy particles guiding center orbits are calculated as a contour plot of conserved variable in Hamiltonian formulation and particles initial position with different levels of energy and pitch angles, that satisfy resonance condition, are considered. From collisionless approximation, distribution function is assumed uniform on the particle orbit. Trapped particles, which do not interact with the first wall, contribute to the distribution function (precession current). Then the profile of orbit-driven current is estimated by multiplying the particle density on the resonance surface and the velocity on the orbits. Negative current near the magnetic axis is shown and hollow current profile is expected even if pressure driven current is considered.
Considering the hollow current profile shifted toward the low-field region, the equilibrium is fitted within nested magnetic surfaces by J-EFIT coded by MATLAB. Though the plasma boundary shape reflects the plasma current density profile, the tendency of the equilibrium shape fitted by the J-EFIT did not coincide with the orbit-driven current profile. The collision effect on the current profile may be important. But the extension to the current profile without assuming nested contours is introduced into the J-EFIT code and the appropriate plasma shape of free boundary with the hollow current profile may be fitted to the measured magnetic data.
Co-authors
Aki Higashijima
(Advanced Fusion Research Center, RIAM, Kasuga, Japan)
Akihide Fujisawa
(Advanced Fusion Research Center, RIAM, Kasuga, Japan)
Atsushi Fukuyama
(Kyoto University, Kyoto, Japan)
Hideki Zushi
(Advanced Fusion Research Center, RIAM, Kasuga, Japan)
Hiroshi Idei
(Advanced Fusion Research Center, RIAM, Kasuga, Japan)
Hisatoshi Nakashima
(Advanced Fusion Research Center, RIAM, Kasuga, Japan)
Kazuaki Hanada
(Advanced Fusion Research Center, RIAM, Kasuga, Japan)
Kazuo Nakamura
(Nuclear Fusion Dynamics, RIAM, Kyushu University, Kasuga, Japan)
Kazutoshi Tokunaga
(Nuclear Fusion Dynamics, RIAM, Kyushu University, Kasuga, Japan)
Kenichi Kurihara
(Japan Atomic Energy Agency, Naka, Japan)
Kuniaki Araki
(Nuclear Fusion Dynamics, RIAM, Kyushu University, Kasuga, Japan)
Makoto Hasegawa
(Nuclear Fusion Dynamics, RIAM, Kyushu University, Kasuga, Japan)
Manabu Takechi
(Japan Atomic Energy Agency, Naka, Japan)
Md Mahbub Alam
(AEES, IGSES, Kyushu University, Kasuga, Japan)
Michiharu Sueoka
(Japan Atomic Energy Agency, Naka, Japan)
Osamu Mitarai
(Kumamoto Liberal Arts Education Center, Tokai University, Kumamoto, Japan)
Shoji Kawasaki
(Advanced Fusion Research Center, RIAM, Kasuga, Japan)
Takahiro Nagata
(Advanced Fusion Research Center, RIAM, Kasuga, Japan)
Yanzheng Jiang
(Department of Engineering Physics, Tsinghua University, Beijing, China)
Yoichi Kawamata
(Japan Atomic Energy Agency, Naka, Japan)
Yoshihiko Nagashima
(Advanced Fusion Research Center, RIAM, Kasuga, Japan)
