1 - Nuclear Sciences and Applications - IAEA

442 KIYAMA et al.
1.0
ne/ne
0.5
ne/ne
10
7
5
3
2
1
0.7
0.5
0.3
0.2
_
( b ) quiet
• / ; • /
*
. 'A
••£..*
*
/
qj,3 q- -2
i . ,i , , ,
d \
-.1 -
°"
\ noisy
«'tf
30 50 70 100 200
[p (VA)
tie
0.5
-3 0 *3 *6 *9 ,, „
i rlrm. /Ishell
centre
ricmi /tube wall
limiter
FIG. 4. Global energy confinement time rE of noisy plasmas with relaxation oscillations and of quiet
plasmas as functions of density (a) at Ip ~ 120-130 kA and (b) plasma current at n, ~ 10 20 m' 3 ;
(c) profiles of densities and density fluctuations of noisy and quiet low q plasmas.
intermittently. The density profiles and the intensity of their fluctuations are shown
in Fig. 4(c). In the low q plasma, the density fluctuation level at the periphery is
lower in the flat profile than in the peaked. In these noisy plasmas, rE decreases
with decreasing density in the low density region (n,, < 10 20 m" 3 ) and also
decreases with decreasing qf, as is shown in Figs 4(a) and (b). The deterioration of
the confinement seems to be caused by the deviation from and the relaxation to the
specific q profile, accompanied by the relaxation oscillations.
A correlation analysis of horizontal multi-chord soft X-ray signals indicates the
appearance of kink-like modes of low m and n numbers in the low q region. The perturbed
poloidal field distribution on the wall surface also has a coherent structure,
corresponding to the intermittent density fluctuation.
Low level high frequency fluctuations are observed in n