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Oikawa, Toshihiro; Polevoi, A. R.*; Mukhovatov, V.*; Sakamoto, Yoshiteru; Kamada, Yutaka; Shimada, Michiya*; Campbell, D. J.*; Chuyanov, V.*; Schunke, B.*; Tanga, A.*; et al.
no journal, ,
In the ITER design review, reducing the NBI energy is proposed for increasing the plasma rotation in terms of suppressing MHD instabilities. NBI capability has been assessed for various design possibilities. In D-T operation, the planned auxiliary heating power makes possible reliable operation well above the H-L transition boundary. In hydrogen operation the beam energy should be limited to 500keV due to the NBI shinethrough. However, reduction of the NBI central heating at high density necessary for the ITER mission is significant at 500keV, confirming the need for higher energy in DT operation. Although the rotation increases by 13% at 750keV relative to 1MeV at constant power, NB current drive decreases by 20%, which would be problematic for the development of steady-state scenarios. Therefore it is concluded that the beam energy should be kept 1MeV in DT operation. The beam energy variation in a pulse enables the plasma beta control for avoiding the stability boundary.
Nakamura, Kazuo*; Matsufuji, Shinji*; Tomoda, Seiji*; Wang, F.*; Mitarai, Osamu*; Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Sato, Konosuke*; Zushi, Hideki*; et al.
no journal, ,
no abstracts in English
Matsumoto, Taro; Tokuda, Shinji
no journal, ,
For the understandings of the tokamak plasma dynamics, the resistive magnetohydrodynamic (MHD) spectrum is investigated in detail by solving the eigenvalue problem of the reduced MHD equations in cylindrical tokamak plasmas, in particular for asymptotically smaller resistivity than the previous works. In the presence of the resistivity, the eigenvalues of linearlized resistive MHD are not necessarily purely real, but have imaginary part. Thus, the eigenvalues are distributed on the negative real axis as continuum spectrum of dumping modes, in the complex plane as discrete spectrum of oscillatory and dumping modes, and on the positive real axis as discrete spectrum of unstable mode. For a wide regime of the resistivity 
from 1
10
to 1.510
, the shape and location of eigenvalue distribution for m/n=1/1 modes which have the same resonant surface at q=1 is almost independent of the resistivity, although the density of the eigenvalues on these curves increases. However, for further small resistivity, it is found that the characteristics of eigenvalue distribution and eigenfunction is changed even for small reduction of resistivity.