The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation
The analysis of plasma density oscillations and E×B rotation of U-3M torsatron plasma was performed by UHR correlation reflectometry during the transport barrier formation. The connections between these characteristics and the phenomenon of inner and edge transport barrier formation were determine...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2006
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| Cite this: | The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation / A.I. Skibenko, P.Ya. Burchenko, A.Ye. Kulaga, A.V. Lozin, V.L. Ocheretenko, I.B. Pinos, O.S. Pavlichenko, A.V. Prokopenko, A.S. Slavnyj, M.I. Tarasov, S.A. Tsybenko // Вопросы атомной науки и техники. — 2006. — № 6. — С. 241-243. — Бібліогр.: 6 назв. — рос. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859986815494127616 |
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| author | Burchenko, P.Ya. Kulaga, A.Ye. Lozin, A.V. Ocheretenko, V.L. Pinos, I.B. Pavlichenko, O.S. Prokopenko, A.V. Slavnyj, A.S. Tarasov, M.I. Tsybenko, S.A. Skibenko, A.I. |
| author_facet | Burchenko, P.Ya. Kulaga, A.Ye. Lozin, A.V. Ocheretenko, V.L. Pinos, I.B. Pavlichenko, O.S. Prokopenko, A.V. Slavnyj, A.S. Tarasov, M.I. Tsybenko, S.A. Skibenko, A.I. |
| citation_txt | The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation / A.I. Skibenko, P.Ya. Burchenko, A.Ye. Kulaga, A.V. Lozin, V.L. Ocheretenko, I.B. Pinos, O.S. Pavlichenko, A.V. Prokopenko, A.S. Slavnyj, M.I. Tarasov, S.A. Tsybenko // Вопросы атомной науки и техники. — 2006. — № 6. — С. 241-243. — Бібліогр.: 6 назв. — рос. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | The analysis of plasma density oscillations and E×B rotation of U-3M torsatron plasma was performed by UHR
correlation reflectometry during the transport barrier formation. The connections between these characteristics and the
phenomenon of inner and edge transport barrier formation were determined experimentally at the different values of HF
power and plasma density
|
| first_indexed | 2025-12-07T16:28:59Z |
| format | Article |
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Problems of Atomic Science and Technology. 2006, 6. Series: Plasma Physics (12), p. 241-243 241
THE ANALYSIS OF TURBULENCE AND ROTATION U-3M TORSATRON
PLASMA DURING TRANSPORT BARRIERS FORMATION
.I. Skibenko, P.Ya. Burchenko, A.Ye. Kulaga, A.V. Lozin, V.L. Ocheretenko, I.B. Pinos,
O.S. Pavlichenko, A.V. Prokopenko, A.S. Slavnyj, M.I. Tarasov, S.A. Tsybenko
Institute of Plasma Physics, NSC KIPT, Kharkov, Ukraine
The analysis of plasma density oscillations and E×B rotation of U-3M torsatron plasma was performed by UHR
correlation reflectometry during the transport barrier formation. The connections between these characteristics and the
phenomenon of inner and edge transport barrier formation were determined experimentally at the different values of HF
power and plasma density.
PACS: 52.55.Hc
INTRODUCTION
The possibility of spontaneous transition to mode
characterized by increase of density temperature and
confinement time of plasma in torsatron U-3M was shown
earlier [1]. Such mode is caused by formation of the
internal transport barrier (ITB) at the vicinity of rational
magnetic surfaces with the stochastic character of
magnetic field lines. The existence of the edge transport
barrier (ETB) was proved by Langmuir probe
measurements in the out-of–separatrix area [2] and by
correlation reflectometry in the near-separatrix area. The
occurrence of such barrier was usually linked with the
formation of increased electric field in plasma. The
definition of ITB and ETB formation conditions will help
to determine an optimal regime of plasma confinement in
torsatron. As it was noted in works [3] the reaching of a
high confinement mode is usually accompanied by a large
shear of rotation velocity in crossed E×H fields, by
reduction of fluctuations correlation length with following
them decorrelation. An important role in the transport
processes belong to a different types of oscillations
excited in plasma. Plasma turbulence is usually defined
by a set of different oscillatory processes that could
studied by means of microwave correlation
reflectometry.
In the present work, the results of experimental study
of oscillation processes and E×H rotation character in the
different regime of a high-frequency discharge including
ITB and ETB are considered.
EXPERIMENT
The experiments were carried out on U-3M device,
which is an l = 3, m = 9 torsatron with and opened
divertor (R = 100 cm, a = 13.5 cm). Plasma creation and
heating in U-3M is provided by a high-frequency method
in the range of frequencies f fci (f 8.5…8.8 MHz).
High-frequency power was introduced into plasma using
the antennas placed inside the helical winding near the
last closed magnetic surface.
Experimental measurements were provided at the
intensity of magnetic field B0 = 7.2 kE and introduced
high-frequency power Prf = 150…200 kW when the
average plasma density was n = 1…1.4×1012 cm-3 and
3…4×1012 cm-3. Used scheme of correlation reflectometry
is shown on Fig.1. This method is the most suitable for
obtaining the plasma rotation velocity on U-3M [1,4]. The
application of correlation reflectometry method is suitable
under the certain conditions: the long-wave length
fluctuation dominate in the turbulence spectrum, the ref-
lection occur in cut-off layer, the turbulence correlation
time is smaller then correlation shift caused by rotation,
the oscillation characteristics do not change appreciable at
layer motion between antennas [4]. Taking into account
[5] that reflection takes place in the cut-off layer if the
fluctuation wave number: k 2·kA = 1.26·k0
+2/3·L-1/3,
where k0= 2 and kA, , L are the Aire wave vector,
probing wavelength and the gradient length this inequality
is satisfied for given experimental conditions. Since the
average density in studied regime is n ~ 1012 cm-3, to
obtain a reflection near edge of the confinement area
(n < 1012 cm-3) the probing may be provided by X-waves.
From outer side of the torus the plasma probing was
provided by X-waves f = 18.5…25.5 GHz (electron
cyclotron frequency on the separatrix was fce = 17 GHz
and on the axis of magnetic field fce = 19.2 GHz) in
neighbor cross-sections distanced on l = 50 cm. from
each to other and from the inner side plasma location was
provided by O-wave in same plasma density layer. Such
probing set-up allowed using X-waves location at a single
frequency and near values of magnetic field, near the
density gradient.
The shift of the cross-correlation function is the result
of poloidal and toroidal rotation. Since a period of
toroidal rotation is equal to nine periods of poloidal
rotation, the main contribution in measured CCF period is
made by poloidal rotation. This assumption was proved
by comparing data from toroidally (2, 3) and poloidally
(2, 4) shifted channels Fig.2. Low-frequency oscillations
correspond to layer rotation, high-frequency components
are connected with oscillatory processes. The reflection
radius was inferred from reflectometry.
Oscillations excited in plasma were studied by using
spectral and correlation analysis of the backscattered
microwave signals. To observe the radiation at the area of
electron cyclotron waves a superheterodyne microwave
signal analyzer was used.
EXPERIMENTAL RESULTS AND
DISCUSSION
The density oscillations spectrums were studied over
the analyzing of autocorrelation functions (ACF) for three
reflectometrical channels and its spectrums. Such
spectrums for one of the channel (N 2) are shown on
242
Fig.1. Setup of reflectometry UHF antennae for cross-
section D-D and J-J
Fig.2. Cross-correlation functions of toroidal (2-6) and
poloidal (2-3) distanced channel for time 15-16 ms
Fig.3. Auto-correlation functions of the back-scattered
UHF signals and their spectrums in time intervals
21…22 ms (a, b) and 37…38 ms (c, d)
Fig.3. ACF shows that these oscillations have a stochastic
character with separate maximums, which are shifting
towards a low frequency when higher density regime put
an end. A high-frequency component here corresponds to
high-frequency ACF on Fig.2. The analysis of poloidal
rotation velocity temporal evolution was made at
B0 = 7.2 kE and high-frequency generator anode voltage
7.5 kV and 9 kV with the hydrogen pressure
7.42×10-6 Torr and n 1…4×1012 cm-3. Fig.4 displays
Vpol(t) at rref
(1) = r/a (corresponds to the area of magnetic
islands) and rref
(2) (near the separatrix). The decreasing of
high-frequency power or the average density increasing
leads to reduction of |Vpol| and its maximum shifts to the
end of the high-frequency energy impulse. On Fig.5 one
could observe the dependence: E(t)=Vpol(t)B×10-8 [V/cm],
where Vpol corresponds to displayed on Fig.4 and B is the
vacuum intensity of magnetic field corresponding to layer
with Vpol. By comparison of Vpol(t) and E(t) in the area of
magnetic islands and in the border area one could make a
conclusion about decorrelation of the electric field in ITB
and ETB layers. As the ITB mode terminates the field
intensity reduces at the middle of the radius and increases
on the edge. Spatial and temporal behavior of ITB and
ETB layers may be monitored by observation of the nl
and reflected microwave signals level evolution (Fig.6).
Fig.4. Temporal dependencies of poloidal velocity at HF
generator voltage U=9 kV (a) and U=7.5 kV (b):1,3– near
separatrix; 2, 4 – in vicinity of rational magnetic surfaces
Fig.5. Temporal dependencies of BVE p ⋅= ⋅10 –8 V/cm
for data of mode on Fig.4
The signals of reflectometers exhibited phase
oscillations in the reflected wave before the formation of
ITB and ETB. These oscillations correspond to periodical
shifting of the reflecting layer and damps after the
transport barrier establishment.
ITB occurs at the rational surface vicinity and
occupies a wider segment of confinement area. However
this barrier is more stable in the inner layers
(rref/a = 0.1…0.5). In the outer layers such barrier is
formed later and exists over the smaller time interval.
Before the formation of ETB there was an intensive
ejection of ions in the out-of-separatrix area [3]. Such
ejection results in creation of negative electric potential at
the edge of plasma (Fig.5).
Sometimes before the establishing of the increased
density mode the superthermal radiation of plasma was
registered in the range of electron cyclotron frequency
(fce 17.5 GHz) near the plasma edge (Fig.7).
D-D J-J
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2
t, ms
b
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
a
-0.2
0
0.2
0.4
0.6
0.8
1
a
A, r.u.
0
0.1
0.2
0.3
0.4 A, r.u.
b
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
-0.4 -0.2 0 0.2 0.4
t, ms
c
0
0.1
0.2
0.3
0.4
0.5
0 20 40 60 80 100
f, kHz
d
-15
-10
-5
0
5
10
15
10 15 20 25 30 35 40
t, ms
b
3
4
-40
-30
-20
-10
0
10 V, *10 5 cm/s
a
1
2
-250
-200
-150
-100
-50
0
50
100
a
1
2
E, V/cm
-80
-40
0
40
80
10 15 20 25 30 35 40
t, ms
b3
4
243
Fig.6. Time behavior of integral density nl (a) and the
fragments of back-scattered signals of X-wave from the
outer side at ne=0.4⋅1012 cm-3 (b) and O-wave from the
inner side at ne=1.17⋅1012 cm-3 (c)
The measurements by means of CXH neutral energy
analyzer showed the increase of supra-thermal ion
temperature in this phase of the discharge. These effects
may be connected with the input of RF power at the
plasma periphery.
The peculiarities of the density fluctuation spectra
(Fig. 3) may be connected with the transport barrier
formation: high-frequency oscillations correspond to
short-wave fluctuations during the transport barrier
existence. When the barriers disappear these oscillations
transform into low-frequency long wave ones. Such
confirmation corresponds to conclusion from similar
measurements on T-10 tokamak: coherent oscillations in
the turbulence spectrum correlates with the discharge
transition into a high confinement mode.
Fig.7. Time behavior of integral density nl (a) and the
signal of EC emission, f = 17.5 GHz (b)
REFERENCES
1. E.D. Volkov, V.L. Berezhniy, V. N. Bondarenko et
al. // Czechoslovak Journ. of Physics. 2003, v. 53,
p. 887.
2. V.V. Chechkin, L.I. Grigor`eva, E.L. Sorokovoy et
al. // Plasma Phys. Control. Fusion. 2006, v. 48,
A241-A249.
3. K.H. Burrel // Phys. Plasmas. 1997, v. 4, 5,
p. 1498-1518.
4. E.Z. Gusakov, A.Yu. Popov // 31st EPS Conference
on Plasma Physics, London, 28 June - 2 July 2004.
ECA, p. 181.
5. C. Fanack, I. Boucher, F. Clairet et al. // Plasma
Phys. Control. Fusion. 1996, v. 38, p. 1915.
6. S.V. Soldatov, V.A. Vershkov // Problems of Atomic
Science and Technology. Series "Nuclear Fusion"(4).
2004, p. 32-44.
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30 32 34 36 38
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-100
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100
20 25 30 35 40
t, ms
A, r.u.
c
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20
40
60
80
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0
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300
400
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600
800
1000
1200
0 10 20 30 40 50t, ms
b
|
| id | nasplib_isofts_kiev_ua-123456789-82353 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T16:28:59Z |
| publishDate | 2006 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Burchenko, P.Ya. Kulaga, A.Ye. Lozin, A.V. Ocheretenko, V.L. Pinos, I.B. Pavlichenko, O.S. Prokopenko, A.V. Slavnyj, A.S. Tarasov, M.I. Tsybenko, S.A. Skibenko, A.I. 2015-05-28T19:01:51Z 2015-05-28T19:01:51Z 2006 The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation / A.I. Skibenko, P.Ya. Burchenko, A.Ye. Kulaga, A.V. Lozin, V.L. Ocheretenko, I.B. Pinos, O.S. Pavlichenko, A.V. Prokopenko, A.S. Slavnyj, M.I. Tarasov, S.A. Tsybenko // Вопросы атомной науки и техники. — 2006. — № 6. — С. 241-243. — Бібліогр.: 6 назв. — рос. 1562-6016 PACS: 52.55.Hc https://nasplib.isofts.kiev.ua/handle/123456789/82353 The analysis of plasma density oscillations and E×B rotation of U-3M torsatron plasma was performed by UHR correlation reflectometry during the transport barrier formation. The connections between these characteristics and the phenomenon of inner and edge transport barrier formation were determined experimentally at the different values of HF power and plasma density en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Plasma diagnostics The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation Article published earlier |
| spellingShingle | The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation Burchenko, P.Ya. Kulaga, A.Ye. Lozin, A.V. Ocheretenko, V.L. Pinos, I.B. Pavlichenko, O.S. Prokopenko, A.V. Slavnyj, A.S. Tarasov, M.I. Tsybenko, S.A. Skibenko, A.I. Plasma diagnostics |
| title | The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation |
| title_full | The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation |
| title_fullStr | The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation |
| title_full_unstemmed | The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation |
| title_short | The analysis of turbulence and rotation U-3M torsatron plasma during transport barriers formation |
| title_sort | analysis of turbulence and rotation u-3m torsatron plasma during transport barriers formation |
| topic | Plasma diagnostics |
| topic_facet | Plasma diagnostics |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/82353 |
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