Speaker
Prof.
Sadao Masamune
(Kyoto Institute of Technology)
Description
We have modified the active MHD control system in RELAX in order to compensate for the sideband effect arising from two poloidal gaps of the vacuum vessel. As a result, the discharge duration has reached iron-core-saturation-limited level with stabilization of the resistive wall mode (RWM). The plasma performance has also been improved; the central electron poloidal beta, the ratio of central electron pressure to the edge poloidal magnetic field pressure, has reached ~15% from ~10% with the previous control system, where the electron poloidal beta approximately equals the total electron beta in the RFP. After the modification, self-organization to Quasi-Single Helicity (QSH) state has been observed even in deep-reversal discharges. Magnetic field line tracing with ORBIT code shows that helical flux surfaces recover during the QSH state in the core region, although the region is narrower than that in the conventional shallow-reversal case. The transition to QSH and associated change in magnetic topology may be related with improved axisymmetry of the magnetic boundary which is realized by stabilization of the RWM and the resultant improved RFP plasma performance in deep-reversal regime.
| Country or International Organization | Japan |
|---|---|
| Paper Number | EX/P5-22 |
Primary author
Prof.
Sadao Masamune
(Kyoto Institute of Technology)
Co-authors
Dr
Akio Sanpei
(Kyoto Institute of Technology)
Dr
Daniel Den Hartog
(University of Wisconsin-Madison)
Mr
Dr. Paccagnella
(Consorzio RFX and Consiglio Nazionale delle Ricerche (CNR))
Prof.
Haruhiko Himura
(Kyoto Institute of Technology)
Dr
Karsten McCollam
(University of Wisconsin - Madison)
Mr
Masataka Higuchi
(Kyoto Institute of Technology)
Dr
Naoki Mizuguchi
(National Institute for Fusion Science)
Mr
Ryosuke Tsuboi
(Kyoto Institute of Technology)
Mr
Shun Nakanobo
(Kyoto Institute of Technology)
Dr
Tohru MIZUUCHI
(Institute of Advanced Energy, Kyoto University)
Mr
Tomoyuki Nagano
(Kyoto Institute of Technology)
Dr
Tsuyoshi Akiyama
(National Institute for Fusion Science)
Mr
Yosuke Aoki
(Kyoto Institute of Technology)
