PLASMA VORTEXES INDUCED BY AN EXTERNAL ROTATING HELICAL MAGNETIC PERTURBATION IN TOKAMAKS

1
PLASMA VORTEXES INDUCED BY AN EXTERNAL ROTATING
HELICAL MAGNETIC PERTURBATION IN TOKAMAKS
I.M. Pankratov, A.Ya. Omelchenko, V.V.
Olshansky     Institute of Plasma Physics,
National Science Center Kharkov Institute of
Physics and Technology Akademicheskaya str., 1,
61108 Kharkov, Ukraine   E-mail
pankratov_at_kipt.kharkov.ua
1. INTRODUCTION 2. MODEL AND BASIC
EQUATIONS 3. RESULTS AND DISCUSSION 4.
CONCLUSIONS
2
1. INTRODUCTION

• The external rotating helical magnetic
  perturbation creates a specific topology of the
  magnetic field for control of the plasma edge in
  tokamaks
• These external helical perturbations are resonant
  on the magnetic surfaces,
• where
• Fusion Engineering and Design, 1997, V. 37,
  (Guest Editor K.H. Finken)M.W. Jakubowski, S.S.
  Abdullaev, K.H. Finken. Nucl. Fusion, 2004,
  V.44, No.6 p.S1-S11.
• On the basis of the two-fluid MHD equations the
  influence of the plasma response on the
  penetration of the DED helical perturbations is
  considered
• in the linear approximation for the cylindrical
  model

3

• Previous results
• For TEXTOR a strong response takes place for
  5 kHz, for 1 kHz the plasma
  response is not so strong. The resonant zone
  0.5 cm.
• The linear model is valid for TEXTOR-DED, if DED
  coils current is less than or the order of 5kA.
• The calculated radial profiles of the magnetic
  perturbation amplitudes are in a good qualitative
  agreement with CSTN-IV and HYBTOK-II
  experimental measurements.
• A very wide resonant zone was found for CSTN-IV.
• It was shown that for the CSTN-IV, HYBTOK-II and
  TEXTOR-DED experiments the resistive effects
  dominate in a broader region than that defined by
  the Alfven resonances.
• Pankratov I.M.. Omelchenko A.Ya., Olshansky V.V.
  Problems of Atomic Science and Technology.
  Series Plasma Physics (8), Kharkov (2002 ),
  No.5, p.3
• Pankratov I.M., Omelchenko A.Ya., Olshansky V.V.,
  Finken K.H., Nucl. Fusion 44 (2004) S37

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2. MODEL AND BASIC EQUATIONS
5
A model of current carrying plasma is used,
linear approximation, perturbations The terms
and are neglected.
where
I.M. Pankratov, A.Ya. Omelchenko, V.V. Olshansky
and K.H. Finken. Nucl. Fusion, 2004, V.44, No.6,
p. S37-S43
6
The main HYBTOK
-
II resonant mode (
m/n
6/1) is investigated,
when the value
is equal to zero,
, on
,
where
,
.

The typical HYBTOK
-
II
parameters are used


plasma current
5 kA,



toroidal magnetic field
0.27

T,



edge electron density
,



electron temperature
25 eV.


The estimate of the resonant zone width
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3. RESULTS AND DISCUSSION
)
Figs. 1-3 (
for
In the figures the values of
,
and
are normalized to the values


,


and

,
respectively.

For estimates we use
1 G.

Plasma fluxes
)
Figs. 4-5 (
for
8
Fig. 1
9
Fig. 2
10
Fig. 3
2-3 km/s
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Fig. 4
12
Fig. 5
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4. CONCLUSIONS
1. The present calculations reproduce not only
the radial profiles of amplitudes (I.M.
Pankratov, A.Ya. Omelchenko, V.V. Olshansky and
K.H. Finken. Nucl. Fusion, 2004, V.44, No.6, p.
S37-S43) but also the phase radial profiles of
externally induced magnetic perturbations in the
HYBTOK-II experiments. 2. The plasma vortexes
with opposite direction of rotation are found per
one poloidal period of the external perturbation.
The cases with two vortexes and the formation of
four vortexes per one poloidal period are
considered. 3. In the cylindrical geometry the
similar modelling of the TEXTOR-DED operation was
also made and the similar plasma vortex motions
were observed.
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4. CONCLUSIONS
4. These vortexes may be responsible for the edge
plasma transport. 5. Note that a strong coupling
between m and m ? 1 poloidal modes through the
plasma motion is possible. 6. The calculations
for both HYBTOK-II and TEXTOR-DED tokamaks show,
that distributions of the perturbed current
density and the plasma vortexes are not symmetric
with respect to resonant surface.