Study of gams and related turbulent particle flux with hibp in the T-10 tokamak
The new findings in the behavior of geodesic acoustic modes (GAMs) and turbulent particle flux dynamics on the T-10 tokamak are presented. For the first time in T-10 the broadband oscillations (<250 kHz) of electric potential and density in Ohmic and ECRH regimes (Bt = 1.6…2.4 T, Ipl = 0.15…0.3 M...
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irk-123456789-1221742020-11-18T10:25:07Z Study of gams and related turbulent particle flux with hibp in the T-10 tokamak Eliseev, L.G. Lysenko, S.E. Melnikov, A.V. Krupnik, L.I. Kozachek, A.S. Zenin, V.N. Диагностика плазмы The new findings in the behavior of geodesic acoustic modes (GAMs) and turbulent particle flux dynamics on the T-10 tokamak are presented. For the first time in T-10 the broadband oscillations (<250 kHz) of electric potential and density in Ohmic and ECRH regimes (Bt = 1.6…2.4 T, Ipl = 0.15…0.3 MA, n‾e = (0.6…5)×10¹⁹ m⁻³) were measured by Heavy Ion Beam Probe (HIBP) in the core plasmas. At the periphery, at r/a > 0.8, the dominated GAM peak with frequency ~ 14 kHz and noticeable peak of quasi-coherent oscillations in the frequency band 40…100 kHz were observed. The multichannel HIBP measurements were performed to measure poloidal electric field Epol and to retrieve the electrostatic turbulent radial particle flux driven by E×B drift. The preliminary experiment shows that in contrast to the power spectral density of plasma potentials, GAM peak was almost invisible in the Epol power spectrum and on the frequency resolved turbulent particle flux. These results are consistent with the general concept of GAM as a high-frequency branch of zonal flows, having symmetric poloidal structure of potential perturbation, which were supported by earlier observation of poloidal mode number m=0 in T-10. Представлены новые результаты исследований геодезических акустических мод (ГАМ) и турбулентного потока частиц на токамаке T-10. Впервые на Т-10 в разрядах с омическим и ЭЦР-нагревом (Bt = 1,6…2,4 Tл, Ipl = 0,15…0,3 MA, n‾e = (0.6…5)×10¹⁹ m⁻³) в горячей зоне плазмы с помощью зондирования пучком тяжёлых ионов (ЗПТИ) измерены широкополосные колебания электрического потенциала и плотности с частотами до 250 кГц. На периферии, r/a > 0,8, наблюдался преобладающий пик ГАМ с частотой ~ 14 кГц и заметный пик квазикогерентных колебаний с частотами 40…100 кГц. Многоканальные ЗПТИ измерения позволили оценить полоидальное электрическое поле Epol и найти радиальный электростатический турбулентный поток частиц, возбуждаемый E×B дрейфом. Предварительные эксперименты показали, что ГАМ пик виден на спектре колебаний потенциала, но практически не виден на спектре Epolи на частотно разрешённом потоке частиц. Эти результаты согласуются с общей теоретической концепцией, что ГАМ – это высокочастотная ветвь зональных потоков с симметричной полоидальной структурой возмущений потенциала, а также с прежними наблюдениями полоидального модового числа m = 0. Представлено нові результати досліджень геодезичних акустичних мод (ГАМ) і турбулентного потоку часток на токамаці T-10. Вперше на Т-10 в розрядах з омічним і ЕЦР-нагрівом (Bt = 1,6…2,4 Tл, Ipl = 0,15...0,3 MA, n‾e = (0.6…5)×10¹⁹ m⁻³) у гарячій зоні плазми за допомогою зондування пучком важких іонів (ЗПВІ) виміряні широкосмугові коливання електричного потенціалу та щільності з частотами до 250 кГц. На периферії, r/a > 0,8, спостерігався переважаючий пік ГАМ з частотою ~ 14 кГц і помітний пік квазікогерентних коливань з частотами 40…100 кГц. Багатоканальні ЗПВІ виміри дозволили оцінити полоїдальне електричне поле Epol і знайти радіальний електростатичний турбулентний потік часток, збуджуваний E×B дрейфом. Попередні експерименти показали, що ГАМ пік видно на спектрі коливань потенціалу, але практично не видно на спектрі Epol і на частотно дозволеному потоці часток. Ці результати узгоджуються із загальною теоретичною концепцією, що ГАМ - це високочастотна гілка зональних потоків з симетричною полоїдальною структурою обурень потенціалу, а також з колишніми спостереженнями полоїдального модового числа m = 0. 2017 Article Study of gams and related turbulent particle flux with hibp in the T-10 tokamak / L.G. Eliseev, S.E. Lysenko, A.V. Melnikov, L.I. Krupnik, A.S. Kozachek, V.N. Zenin // Вопросы атомной науки и техники. — 2017. — № 1. — С. 241-243. — Бібліогр.: 9 назв. — англ. 1562-6016 PACS: 52.35.Ra, 52.55.Fa, 52.70.Nc http://dspace.nbuv.gov.ua/handle/123456789/122174 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Диагностика плазмы Диагностика плазмы |
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Диагностика плазмы Диагностика плазмы Eliseev, L.G. Lysenko, S.E. Melnikov, A.V. Krupnik, L.I. Kozachek, A.S. Zenin, V.N. Study of gams and related turbulent particle flux with hibp in the T-10 tokamak Вопросы атомной науки и техники |
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The new findings in the behavior of geodesic acoustic modes (GAMs) and turbulent particle flux dynamics on the T-10 tokamak are presented. For the first time in T-10 the broadband oscillations (<250 kHz) of electric potential and density in Ohmic and ECRH regimes (Bt = 1.6…2.4 T, Ipl = 0.15…0.3 MA, n‾e = (0.6…5)×10¹⁹ m⁻³) were measured by Heavy Ion Beam Probe (HIBP) in the core plasmas. At the periphery, at r/a > 0.8, the dominated GAM peak with frequency ~ 14 kHz and noticeable peak of quasi-coherent oscillations in the frequency band 40…100 kHz were observed. The multichannel HIBP measurements were performed to measure poloidal electric field Epol and to retrieve the electrostatic turbulent radial particle flux driven by E×B drift. The preliminary experiment shows that in contrast to the power spectral density of plasma potentials, GAM peak was almost invisible in the Epol power spectrum and on the frequency resolved turbulent particle flux. These results are consistent with the general concept of GAM as a high-frequency branch of zonal flows, having symmetric poloidal structure of potential perturbation, which were supported by earlier observation of poloidal mode number m=0 in T-10. |
| format |
Article |
| author |
Eliseev, L.G. Lysenko, S.E. Melnikov, A.V. Krupnik, L.I. Kozachek, A.S. Zenin, V.N. |
| author_facet |
Eliseev, L.G. Lysenko, S.E. Melnikov, A.V. Krupnik, L.I. Kozachek, A.S. Zenin, V.N. |
| author_sort |
Eliseev, L.G. |
| title |
Study of gams and related turbulent particle flux with hibp in the T-10 tokamak |
| title_short |
Study of gams and related turbulent particle flux with hibp in the T-10 tokamak |
| title_full |
Study of gams and related turbulent particle flux with hibp in the T-10 tokamak |
| title_fullStr |
Study of gams and related turbulent particle flux with hibp in the T-10 tokamak |
| title_full_unstemmed |
Study of gams and related turbulent particle flux with hibp in the T-10 tokamak |
| title_sort |
study of gams and related turbulent particle flux with hibp in the t-10 tokamak |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2017 |
| topic_facet |
Диагностика плазмы |
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http://dspace.nbuv.gov.ua/handle/123456789/122174 |
| citation_txt |
Study of gams and related turbulent particle flux with hibp in the T-10 tokamak / L.G. Eliseev, S.E. Lysenko, A.V. Melnikov, L.I. Krupnik, A.S. Kozachek, V.N. Zenin // Вопросы атомной науки и техники. — 2017. — № 1. — С. 241-243. — Бібліогр.: 9 назв. — англ. |
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Вопросы атомной науки и техники |
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ISSN 1562-6016. ВАНТ. 2017. №1(107)
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2017, № 1. Series: Plasma Physics (23), p. 241-243. 241
STUDY OF GAMS AND RELATED TURBULENT PARTICLE FLUX
WITH HIBP IN THE T-10 TOKAMAK
L.G. Eliseev
1
, S.E. Lysenko
1
, A.V. Melnikov
1,2
, L.I. Krupnik
3
, A.S. Kozachek
3
, V.N. Zenin
1
,
and HIBP team
1,3
1
NRC ''Kurchatov Institute'', Moscow, Russia;
2
National Research Nuclear University MEPhI, Moscow, Russia;
3
Institute of Plasma Physics of the NSC KIPT, Kharkov, Ukraine
E-mail: reonid@yahoo.com
The new findings in the behavior of geodesic acoustic modes (GAMs) and turbulent particle flux dynamics on
the T-10 tokamak are presented. For the first time in T-10 the broadband oscillations (<250 kHz) of electric
potential and density in Ohmic and ECRH regimes (Bt = 1.6…2.4 T, Ipl = 0.15…0.3 MA, ne = (0.6…5) 10
19
m
-3
)
were measured by Heavy Ion Beam Probe (HIBP) in the core plasmas. At the periphery, at r/a > 0.8, the dominated
GAM peak with frequency ~ 14 kHz and noticeable peak of quasi-coherent oscillations in the frequency band
40…100 kHz were observed. The multichannel HIBP measurements were performed to measure poloidal electric
field Epol and to retrieve the electrostatic turbulent radial particle flux driven by E B drift. The preliminary
experiment shows that in contrast to the power spectral density of plasma potentials, GAM peak was almost
invisible in the Epol power spectrum and on the frequency resolved turbulent particle flux. These results are consistent
with the general concept of GAM as a high-frequency branch of zonal flows, having symmetric poloidal structure of
potential perturbation, which were supported by earlier observation of poloidal mode number m=0 in T-10.
PACS: 52.35.Ra, 52.55.Fa, 52.70.Nc
INTRODUCTION
Geodesic acoustic modes (GAMs) are the high-
frequency branch of zonal flows in toroidal fusion
devices. GAMs are actively studied in tokamaks and
stellarators as one of possible mechanisms of the plasma
turbulence self-regulation by the oscillating radial
electric field [1]. GAMs should transform the radial
turbulent oscillations, which transfer the energy of
plasma turbulence, into the torsional plasma
oscillations, which do not transmit the energy radially.
The linear theory predicts that the poloidal mode
number for GAM potential oscillations is m=0 [2]. Due
to this poloidal symmetry, a poloidal component of
electric field Epol is expected to be zero for GAMs.
Therefore, the radial turbulent particle flux should also
be zero at the GAM frequency. However, this
theoretical expectation was not yet validated
experimentally in the core plasma. The presented report
contains the preliminary results of such validation.
1. EXPERIMENTAL SETUP
The GAM oscillations are systematically studied at
the circular T-10 tokamak (R = 1.5 m, a = 0.3 m,
Bt = 1.5…2.5 T, Ipl = 0.15…0.3 MA) using heavy ion
beam probing (HIBP) [3, 4]. HIBP is a direct diagnostic
for studying the electric potential and its oscillations.
GAMs are typically observed very clearly as a
pronounced monochromatic peak in the frequency
power spectra of potential. This diagnostic has an
important ability to for study plasma potential
oscillations and, specifically, the GAM characteristics in
the core region, which is inaccessible for Langmuir
probes, which typically used to investigate potential
oscillations and the GAM at the edge [5]. Basic
principles of HIBP measurements of plasma parameters
in T-10 were described in [6]. We use the ions Tl
+
with
energy Eb up to 280 keV. Varying the beam energy and
entrance angle into the plasma, we can spatially scan the
sample volume (SV) and form the detector grid: the
observation area in plasma. For the registration of the
secondary beam It we used the energy analyzer with five
entrance slits Fig. 1 in [7]. The each slit provides the
spatial resolution < 1-2 cm, and the temporal resolution
<5 s in the radial range 6 < r < 30 cm for Bt < 2.1 T.
This analyzer allows us to carry out simultaneous
measurements in few (up to 5) neighbor SV. The
magnetic flux surfaces in poloidal cross-section of T-10
are circular. The adjustment procedure can be
performed to get the location of SVs as close as possible
to desired magnetic flux surfaces that allows us to
estimate the local poloidal electric field
Epol = ( i- j)/ x, (1)
where x ~ 1 cm, i, j = 1...5, i j. This limits the
poloidal wave vector, k < 3 cm
-1
. The radial E B drift
velocity is
Vr = Epol/Bt. (2)
The turbulent particle flux is defined as
E B(t) = e rn V = 1/Bt ( )en t polE (t). (3)
To analyze the frequency structure of the flux, we
use the flux spectral function [8]:
( , ) 2 / Re( ( , ))E B t n Epolf t B S f t , (4)
where Re( ( , ))n EpolS f t is a real part of the complex
Fourier power cross-spectral density (CSD) for plasma
density and Epol.
To measure E B(t), the density fluctuations
en
should be obtained simultaneously at the same position
as
polE
~ that is provided by combined potential and beam
current measurements with HIBP. For the analysis of
the flux dynamics in arbitrary units, or for frequency
mailto:vitalyzenin@mail.ru
242 ISSN 1562-6016. ВАНТ. 2017. №1(107)
spectra analysis, the relative data for density oscillations
( ) ( ) /e t tn t I t I is sufficient. In the low-density case,
for estimation of the absolute value of E B(t),
en may
be replaced by ( )tI t . In the higher-density case, one
should take into account the attenuation effect by the
expression:
e/e t tn I I n , where oscillatory component
/t tI I is measured by HIBP, and normalization factor ne
is provided by other diagnostics like interferometry.
This way allows us to extract E B for the first time in
the core plasma of T-10.
2. EXPERIMENTAL RESULTS
Fig. 1 shows the amplitude of GAM activity (over
extended frequency domain covering GAM and
satellite) obtained from difference of potentials between
neighboring poloidally shifted sample volumes as
function of radial difference between them. Figure
shows that for r<1 cm (the beam diameter) the radial
component Er may be omitted, and the GAM amplitude
is invisible on the noise background. When r
increases, the role of Er becomes more important, and
the measured GAM amplitude grows.
Fig. 2 shows the time evolution of power spectral
density (PSD) for potential oscillations measured at the
central slit 3 (a); and PSD for difference of potentials
oscillations between the central and edge slits 1 - 3,
i.e. the electric field (b). The time evolution of the
frequency resolved flux spectral function calculated as
cross-spectral density (CSD) for difference of potentials
1 and 3 and density oscillations (eq. 4) is shown in (c).
We see that GAM is clearly pronounced on the potential
spectrum, but is not seen on E and so in the flux spectra.
Fig. 3,a shows the time evolution of spectral
function of turbulent particle flux (4). The quasi-
coherent (QC) modes are dominated on the spectrum.
The total turbulent particle flux driven by QC modes is
shown in Fig. 3,b. It is determined as follows:
2
1
( ) 2 / Re( ( , )) ,
f
QC t n Epol
f
t B S f t df (5)
where f1=100 kHz, f2=175 kHz for the considered case.
Fig. 1. Dependence of potential difference vs the
distance between the sample volumes for GAM+satellite
frequency domain
Fig. 2. Time evolution of: power spectral density (PSD)
of potential oscillations measured by the central slit 3
(a); PSD for difference of potentials on central and
edge slits ( 1- 3) (b); the frequency resolved flux
spectral function (c)
t (ms)
Fig. 3. Time evolution of: spectral function of turbulent
particle flux (a); turbulent particle flux driven by
quasicoherent (QC) modes (b)
The time-frequency domain for QC mode is shown
in Fig. 3,a as a black rectangle. Figure shows that QC
mode generates pronounced outward particle flux,
contrary to GAM, which does not generate neither
outward nor inward flux for the examined experimental
conditions.
QC
0.0 0.5 1.0 1.5 2.0 2.5
0
10
20
30
A
(
G
A
M
+
s
a
te
ll
it
e
)
(V
)
r (cm)
noise level
a
b
c
a
b
ISSN 1562-6016. ВАНТ. 2017. №1(107) 243
CONCLUSIONS
The multichannel energy analyzer makes the heavy
ion beam probing an effective tool to study polE up to
250 kHz. In combination with simultaneously measured
density perturbation HIBP allows us to retrieve the
electrostatic radial turbulent particle fluх driven by E B
drift. The preliminary data shows that GAM-driven
polE oscillations happen to be below experimental
accuracy, and could be considered as negligibly small
for the regimes under study. Thus, one can conclude
that in the GAM frequency range, the turbulent E B
particle flux is not observed. This experimental
observation agrees with theoretical predictions [2] and
with the previous results that GAMs in T-10 have the
poloidal mode number m = 0 [7]. Note that the similar
absence of the turbulent E B particle fluх for
electrostatic modes was observed in the TJ-II stellarator
[9].
ACKNOWLEDGEMENTS
The research was performed by financial support of
Russian Science Foundation, project 14-22-00193.
REFERENCES
1. A. Fujisawa. A review of zonal flow experiments//
Nucl. Fusion. 2009, v. 49, p. 013001.
2. P.H. Diamond et al. Zonal flows in plasma – a review
// Plasma Phys. Control. Fusion. 2005, v. 47, p. R35.
3. A.V. Melnikov et al. Investigation of geodesic
acoustic modes oscillations in the T-10 tokamak //
Plasma Phys. Control. Fusion. 2006, v. 48, p. S87.
4. A.V. Melnikov et al. Investigation of the plasma
potential oscillations in the range of geodesic acoustic
mode frequencies by heavy ion beam probing in
tokamaks // Czech. J. Phys. 2005, v. 55, p. 349.
5. W. Chen et al. Observation of energetic-particle-
induced GAM and nonlinear interactions between
EGAM, BAEs and tearing modes on the HL-2A
tokamak // Nucl. Fusion. 2013, v. 53, p. 113010.
6. A.V. Melnikov et al. Electric potential dynamics in
OH and ECRH plasmas in the T-10 tokamak // Nucl.
Fusion. 2013, v. 53, p. 093019.
7. V.N. Zenin et al. Study of poloidal structure of
geodesic acoustic modes in the T-10 tokamak with
heavy ion beam probing // Probl. of Atom. Sci. and
Techn. Ser. ”Plasma Phys”. 2014, (20), № 6, p. 269.
8. E.J. Powers. Spectral techniques for experimental
investigation of plasma diffusion due to polychromatic
effects // Nucl. Fusion. 1974, v. 14, p. 749.
9. A.V. Melnikov et al. A quasi-coherent electrostatic
mode in ECRH plasmas on TJ-II // Plasma Fusion
Research. 2011, v. 6, p. 2402030.
Article received 30.09.2016
ИССЛЕДОВАНИЕ ГАМ И ТУРБУЛЕНТНОГО ПОТОКА С ПОМОЩЬЮ ПУЧКА ТЯЖËЛЫХ
ИОНОВ В ТОКАМАКЕ Т-10
Л.Г. Елисеев, С.E. Лысенко, A.В. Мельников, Л.И. Kрупник, А.C. Козачeк, В.Н. Зенин и команда ЗПТИ
Представлены новые результаты исследований геодезических акустических мод (ГАМ) и турбулентного
потока частиц на токамаке T-10. Впервые на Т-10 в разрядах с омическим и ЭЦР-нагревом (Bt = 1,6…2,4 Tл,
Ipl = 0,15…0,3 MA, ne = (0,6…5) 10
19
м
-3
) в горячей зоне плазмы с помощью зондирования пучком тяжёлых
ионов (ЗПТИ) измерены широкополосные колебания электрического потенциала и плотности с частотами
до 250 кГц. На периферии, r/a > 0,8, наблюдался преобладающий пик ГАМ с частотой ~ 14 кГц и заметный
пик квазикогерентных колебаний с частотами 40…100 кГц. Многоканальные ЗПТИ измерения позволили
оценить полоидальное электрическое поле Epol и найти радиальный электростатический турбулентный поток
частиц, возбуждаемый E B дрейфом. Предварительные эксперименты показали, что ГАМ пик виден на
спектре колебаний потенциала, но практически не виден на спектре Epol и на частотно разрешённом потоке
частиц. Эти результаты согласуются с общей теоретической концепцией, что ГАМ – это высокочастотная
ветвь зональных потоков с симметричной полоидальной структурой возмущений потенциала, а также с
прежними наблюдениями полоидального модового числа m = 0.
ДОСЛІДЖЕННЯ ГАМ ТА ТУРБУЛЕНТНОГО ПОТОКА ЗА ДОПОМОГОЮ ПУЧКА ВАЖКИХ
ІОНІВ У ТОКАМАЦІ Т-10
Л.Г. Єлісєєв, С.Є. Лисенко, О.В. Mельнiков, Л.І. Kрупнік, О.С. Козачок, В.Н. Зенiн і команда ЗПВІ
Представлено нові результати досліджень геодезичних акустичних мод (ГАМ) і турбулентного потоку
часток на токамаці T-10. Вперше на Т-10 в розрядах з омічним і ЕЦР-нагрівом (Bt = 1,6…2,4 Tл,
Ipl = 0,15...0,3 MA, ne = (0,6…5) 10
19
м
-3
) у гарячій зоні плазми за допомогою зондування пучком важких
іонів (ЗПВІ) виміряні широкосмугові коливання електричного потенціалу та щільності з частотами до
250 кГц. На периферії, r/a > 0,8, спостерігався переважаючий пік ГАМ з частотою ~ 14 кГц і помітний пік
квазікогерентних коливань з частотами 40…100 кГц. Багатоканальні ЗПВІ виміри дозволили оцінити
полоїдальне електричне поле Epol і знайти радіальний електростатичний турбулентний потік часток,
збуджуваний E B дрейфом. Попередні експерименти показали, що ГАМ пік видно на спектрі коливань
потенціалу, але практично не видно на спектрі Epol і на частотно дозволеному потоці часток. Ці результати
узгоджуються із загальною теоретичною концепцією, що ГАМ це високочастотна гілка зональних потоків
з симетричною полоїдальною структурою обурень потенціалу, а також з колишніми спостереженнями
полоїдального модового числа m = 0.
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