Dynamics of plasma poloidal rotation in the U-3M torsatron
Results of experimental study of plasma rotation dynamics in the U-3M torsatron during transition to the improved
 confinement mode are presented. The rotation velocity is measured using the Doppler reflectometry methods. Представлено результати експериментального вивчення динаміки обертання...
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| Veröffentlicht in: | Вопросы атомной науки и техники |
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| Datum: | 2011 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2011
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| Zitieren: | Dynamics of plasma poloidal rotation in the U-3M torsatron / D.A. Sitnikov, A.I. Skibenko, M.I. Tarasov, I.K. Tarasov, V.K. Pashnev, A.V. Prokopenko // Вопросы атомной науки и техники. — 2011. — № 1. — С. 188-190. — Бібліогр.: 4 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860079921052778496 |
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| author | Sitnikov, D.A. Skibenko, A.I. Tarasov, M.I. Tarasov, I.K. Pashnev, V.K. Prokopenko, A.V. |
| author_facet | Sitnikov, D.A. Skibenko, A.I. Tarasov, M.I. Tarasov, I.K. Pashnev, V.K. Prokopenko, A.V. |
| citation_txt | Dynamics of plasma poloidal rotation in the U-3M torsatron / D.A. Sitnikov, A.I. Skibenko, M.I. Tarasov, I.K. Tarasov, V.K. Pashnev, A.V. Prokopenko // Вопросы атомной науки и техники. — 2011. — № 1. — С. 188-190. — Бібліогр.: 4 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | Results of experimental study of plasma rotation dynamics in the U-3M torsatron during transition to the improved
confinement mode are presented. The rotation velocity is measured using the Doppler reflectometry methods.
Представлено результати експериментального вивчення динаміки обертання плазми в торсатроні У-3М під
час переходу розряду в режим покращеного утримання. Швидкість обертання визначалася методом
допплеровської рефлектометрії.
Представлены результаты экспериментального изучения динамики вращения плазмы в торсатроне У-3М во
время перехода разряда в режим улучшенного удержания. Скорость вращения определялась методом
допплеровской рефлектометрии.
|
| first_indexed | 2025-12-07T17:15:49Z |
| format | Article |
| fulltext |
DYNAMICS OF PLASMA POLOIDAL ROTATION
IN THE U-3M TORSATRON
D.A. Sitnikov, A.I. Skibenko, M.I. Tarasov, I.K. Tarasov, V.K. Pashnev, A.V. Prokopenko
Institute of Plasma Physics, NSC “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
E-mail: itarasov@ipp.kharkov.ua
Results of experimental study of plasma rotation dynamics in the U-3M torsatron during transition to the improved
confinement mode are presented. The rotation velocity is measured using the Doppler reflectometry methods.
PACS: 52.55.Hc.
1. INTRODUCTION
The E×B poloidal rotation of the plasma in tokamaks
and stellarators is accompanied with appearance of
transport barriers that influence on the transport of energy
and particles. By studying the rotation of plasma, we can
understand such key moments as the suppression of
turbulence and the transport barrier formation in the
regime of improved confinement.
One of the main diagnostics in the study of these
processes is the microwave reflectometry. It is used to
determine the position of plasma layer in space, the
restoration of profiles of density and its fluctuations and
also to study the rotation speed of the plasma layers.
Plasma probing by O- and X-waves expands the
possibilities of reflectometry. This is due to the fact that
the refractive index of X-waves depends on the magnetic
field. It is perspective in stellarators where the spatial
distribution of the magnetic field is known.
The experimental study of the plasma rotation can be
carried out not only by the correlational microwave
diagnostic [1]. The using of Doppler reflectometry can also
give a comprehensive information about the plasma rotation
velocity [2]. By changing the angle of entry of the
microwave beam in plasma one can determine the speed of
rotation of plasma in different layers by measuring the shift
of the frequency. Thus, the radial profile of the plasma
rotation velocity can be obtained. To determine the radial
plasma layers where the transport barriers (ITB, ETB) are
localized one should outline the points in the measured
profile where the velocity sign changes [3].
In this work the dynamics of the Doppler frequency
shift and the velocity of poloidal rotation are investigated,
taking into account the specific character of the
asymmetric geometry of the closed magnetic surfaces in
the U-3M torsatron at average density ncp≈ 1012 cm-3.
2. EXPERIMENT
The experiments were carried out on the U-3M device
with the magnetic field strength B
188 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2011. № 1.
Series: Plasma Physics (17), p. 188-190.
B0 = 7.2 kOe, at the
anode voltage of the Cascade-1 RF generator U1= 7.5 kV,
and the hydrogen pressure p = 4·10 Torr.-6 The average
density (by the 2mm interferometer), the local density (by
the 20…25 GHz X-wave reflection), and the Doppler
shift of the 10 GHz frequency recorded by the UHF
analyzer were measured in the experiment. The
disposition of diagnostics is presented in Fig. 1.
The X-waves reflectometry was carried out on the low
field side (external probe). Fig. 2 shows the signals of
sensors – the average density, the phase shift of the
reflectometer, the signal from the microwave analyzer.
Fig. 1. a) 1,2 - X-waves f=20-25GHz,
3 – O-wave f=10GHz;
b) the scheme of the measurement of the frequency shift
using the analyzer and the spectral analysis
The reflection radius was determined from the
calculated dependence:
∫=
refr
xdr
0
2
2
μ
λπ
ϕ , (1)
2
1
2
2
1
2
)1(
)1(
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−−
−−
=
vu
vu
xμ
, (2)
where
f
f
u ce= ,
crn
nv = , ⎥
⎦
⎤
⎢
⎣
⎡
−= p
r
rnrn )(1)(
0
0
,
n
p
pn 1
0
+
= .
Eq. (1) was calculated for p = 1 and p = 2. To find the
reflecting layer position by the phase of X-wave reflection
and the mean density, the methods proposed in [4] were
also used. To identify the rotation speed of the plasma
from the Doppler shift of the backscattered signal
frequency, we used the formula
)(2 refr
c
f
fv
μ
Δ
= . (3)
Thus, for the moment of the observed pulse of frequency
offset, the level and localization of the density (refractive
index) of the reflecting layer are necessary to be known.
For a known radial density distribution, the value of
μ(rref) was determined from
2
1
)(
1)( ⎥
⎦
⎤
⎢
⎣
⎡
−=
cr
ref
ref n
rn
rμ (4)
(at the point of backward Bragg scattering) and rref, which
can be found, considering that
refrefiii rrr μϕμϕ == sinsin 00 , (5)
and taking into account that the point of reflection
1
2
sinsin ==
πϕ i
(where 0ϕ is the angle of incidence at
the plasma boundary).
a
b
c
Fig. 2. Recorded signals:
a) average density; b) the phase shift of the reflectometer;
c) microwave analyzer
The radial density profile in the vertical direction can be
calculated from the density profile measured on the outer
side of the torus and the dependence shown on Fig. 3.
189
Fig. 3. Dependence of the O-wave reflection radius from
the radius of the X-wave reflection
a
b
c
d
Fig. 4. Density of the reflection and the radius of
reflection for the two frequencies of the reflectometer:
a), b) – f=25.1 GHz; c), d) – f = 20.8 GHz
In this calculations the plasma asymmetry along the chord
defining the reflected wave phase and along the Doppler
scattering chord and the constancy of the density at a
given magnetic surface as well are taken into account.
The dependences of density of the reflection and the
radius of reflection for two frequencies on the chord of
scattering are shown in Fig. 4.
In some discharges the frequency shift in the red and
in the blue regions were simultaneously observed (in one
period) (Fig. 5).
190
DISCUSSION
In RF discharges in the U-3M torsatron the transition
to the improved confinement regime in the range
25…40 ms is observed. This mode differs by a slight
increase in the density and a significant slowing down of
the rate of density decrease (see Fig. 2, a).
Fig. 5. Frequency shift in the red and in the blue region
Fig. 6. Change of the amplitude of the scattered signal
during the pulse
The scattered signal with the Doppler frequency shift
appears before the transition to the regime of improved
plasma confinement. The signal intensity increases
smoothly before the time of improved confinement and
gradually decreases afterwards (Fig. 6).
The observation of several peaks with different
frequency shifts is possible as a result of a split of the
probe beam and the occurrence of scattering from
different layers corresponding to different μ and r.
Fig. 7. Velocity of rotation during the pulse
The frequency shift in the red and blue sides may
indicate the presence of a poloidal velocity shear and,
consequently, an electric field shear. Considering that
scattering occurs at ρ ≈ (r / a) ≈ 0.75…0.9, one can speak
of the appearance of an edge transport barrier prior to the
appearance of the regime of improved confinement.
The velocity of rotation decreases sharply after the
end of the improved confinement time (Fig. 7). At the
time before the transition several pulses of scattered
frequency are observed (Fig. 6).
REFERENCES
1. O.S. Pavlichenko, A.I. Skibenko, I.P. Fomin, et al.
Poloidal rotation velocity measurement in toroidal
plasmas via microwave reflectometry // Proceeding of
5th International Workshop on Reflectometry. March 5-
7, 2001, Toki, Japan / NIFS-PROC-49, 2001, p.85.
2. M. Hirsch, E. Holzhauer, et al. // Review of scientific
instruments. 2001, v.72, №1, p.324
3. A.I. Skibenko, V.L. Berezhniy, et al. // Problems of
Atomic Science and Technology. Series “Plasma
Physics” (10). 2005, № 1, p. 200-202.
4. А.V. Prokopenko, А.I. Skibenko, I.B. Pinos.
Determination of the extraordinary wave reflection
layer position in inhomogeneous plasma placed in
radially changing magnetic field//The Journals of
Kharkiv National University. Physical series “Nuclei,
Particles, Fields”. 2008, №794, p.95-99.
Article received 28.10.10.
ДИНАМИКА ПОЛОИДАЛЬНОГО ВРАЩЕНИЯ ПЛАЗМЫ В ТОРСАТРОНЕ У-3М
Д.А. Ситников, А.И. Скибенко, М.И. Тарасов, И.К. Тарасов, В.К. Пашнев, А.В. Прокопенко
Представлены результаты экспериментального изучения динамики вращения плазмы в торсатроне У-3М во
время перехода разряда в режим улучшенного удержания. Скорость вращения определялась методом
допплеровской рефлектометрии.
ДИНАМІКА ПОЛОЇДАЛЬНОГО ОБЕРТАННЯ ПЛАЗМИ В ТОРСАТРОНІ У-3М
Д.А. Сітников, А.I. Скібенко, М.I. Тарасов, I.К. Тарасов, В.К. Пашнєв, O.В. Прокопенко
Представлено результати експериментального вивчення динаміки обертання плазми в торсатроні У-3М під
час переходу розряду в режим покращеного утримання. Швидкість обертання визначалася методом
допплеровської рефлектометрії.
|
| id | nasplib_isofts_kiev_ua-123456789-91073 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T17:15:49Z |
| publishDate | 2011 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Sitnikov, D.A. Skibenko, A.I. Tarasov, M.I. Tarasov, I.K. Pashnev, V.K. Prokopenko, A.V. 2016-01-06T17:18:34Z 2016-01-06T17:18:34Z 2011 Dynamics of plasma poloidal rotation in the U-3M torsatron / D.A. Sitnikov, A.I. Skibenko, M.I. Tarasov, I.K. Tarasov, V.K. Pashnev, A.V. Prokopenko // Вопросы атомной науки и техники. — 2011. — № 1. — С. 188-190. — Бібліогр.: 4 назв. — англ. 1562-6016 PACS: 52.55.Hc. https://nasplib.isofts.kiev.ua/handle/123456789/91073 Results of experimental study of plasma rotation dynamics in the U-3M torsatron during transition to the improved
 confinement mode are presented. The rotation velocity is measured using the Doppler reflectometry methods. Представлено результати експериментального вивчення динаміки обертання плазми в торсатроні У-3М під
 час переходу розряду в режим покращеного утримання. Швидкість обертання визначалася методом
 допплеровської рефлектометрії. Представлены результаты экспериментального изучения динамики вращения плазмы в торсатроне У-3М во
 время перехода разряда в режим улучшенного удержания. Скорость вращения определялась методом
 допплеровской рефлектометрии. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Диагностика плазмы Dynamics of plasma poloidal rotation in the U-3M torsatron Динаміка полоїдального обертання плазми в торсатроні У-3М Динамика полоидального вращения плазмы в торсатроне У-3М Article published earlier |
| spellingShingle | Dynamics of plasma poloidal rotation in the U-3M torsatron Sitnikov, D.A. Skibenko, A.I. Tarasov, M.I. Tarasov, I.K. Pashnev, V.K. Prokopenko, A.V. Диагностика плазмы |
| title | Dynamics of plasma poloidal rotation in the U-3M torsatron |
| title_alt | Динаміка полоїдального обертання плазми в торсатроні У-3М Динамика полоидального вращения плазмы в торсатроне У-3М |
| title_full | Dynamics of plasma poloidal rotation in the U-3M torsatron |
| title_fullStr | Dynamics of plasma poloidal rotation in the U-3M torsatron |
| title_full_unstemmed | Dynamics of plasma poloidal rotation in the U-3M torsatron |
| title_short | Dynamics of plasma poloidal rotation in the U-3M torsatron |
| title_sort | dynamics of plasma poloidal rotation in the u-3m torsatron |
| topic | Диагностика плазмы |
| topic_facet | Диагностика плазмы |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/91073 |
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