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Dynamics and Stability of Resistive Wall Mode in the JT-60U High- β Plasmas
| Content Provider | Semantic Scholar |
|---|---|
| Author | Matsunaga, Go Sakamoto, Yoshiteru Aiba, Nobuyuki Shinohara, Kouji Takechi, Manabu Suzuki, Takeuki Fujita, T. Isayama, Akihiko Oyama, Naoyuki Asakura, Nobuyuki Kamada, Yutaka Ozeki, Takahisa Βno-Wall, Βn-Limit |
| Copyright Year | 2008 |
| Abstract | Abstract. The dynamics and stability of the resistive wall mode (RWM) are investigated in the JT-60U high-β plasmas, and the sustainment of highβ plasmas above the ideal no-wall βN-limit (βno-wall N ) has been demonstrated using stabilization by plasma rotation. In order to suppress a RWM that limits the achievableβN in the wall-stabilized highβN region, that is,βN > βno-wall N , the plasma rotation is kept larger than the critical rotation. By this stabilization, we have successfully sustained βN ' 3.0 for ∼ 5 s, which is about 3 times the current diffusion time τR. In this high-βN region, interesting MHD instabilities have been newly observed just before the RWM, that is, energetic particle driven wall mode (EWM) and RWM precursor. These modes play important roles for RWM stability, thus these can reduce the plasma rotation and finally trigger the RWM. These modes are only observed in the wall-stabilized highβN region. The EWM is thought to be destabilized by a resonance with the precession motion of the beam particles and the RWM. While the RWM precursor has very slower growth time, which is about several tens milliseconds. Although the RWM precursor growth time is similar to the tearing mode growth time, internal measurement such as ECE and soft X-ray array show the RWM precursor does not have any island structures at the rational surfaces. The RWM precursor can strongly affect the rotation profile, in particular, the rotational shear around the q = 2 surface. As either the rotation speed or the rotational shear is deceasing by the RWM precursor, finally the RWM is triggered. From the observed results of the EWM and the RWM precursor, it is concluded that the energetic particles and the rotational shear are important to determine the RWM stability. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www-naweb.iaea.org/napc/physics/FEC/FEC2008/papers/ex_5-2.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
