Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak
This work is dedicated to simultaneous measurements of plasma potential oscillations at GAM frequencies in different locations on the T-10 tokamak and studying their correlation properties. Recent experiments with Heavy Ion Beam Probing and Langmuir probes have shown high coherency between signals...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2018
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| Цитувати: | Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak / V.N. Zenin, M.A. Drabinskij, L.G. Eliseev, S.A. Grashin, P.O. Khabanov, N.K. Kharchev, L.I. Krupnik, A.V. Melnikov // Вопросы атомной науки и техники. — 2018. — № 6. — С. 321-323. — Бібліогр.: 5 назв. — англ. |
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irk-123456789-1490762019-02-20T01:28:24Z Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak Zenin, V.N. Drabinskij, M.A. Eliseev, L.G. Grashin, S.A. Khabanov, P.O. Kharchev, N.K. Krupnik, L.I. Melnikov, A.V. Диагностика плазмы This work is dedicated to simultaneous measurements of plasma potential oscillations at GAM frequencies in different locations on the T-10 tokamak and studying their correlation properties. Recent experiments with Heavy Ion Beam Probing and Langmuir probes have shown high coherency between signals of two diagnostics (up to 0.8) despite a large distance between the observation points: half of torus in toroidal and about π in poloidal direction, up to 12 cm in radial direction. The phase shift between potentials measured with two diagnostics has been obtained in two plasma scenarios. It was found the most likely that potential oscillations at the GAM frequency propagate outward, but influence of 2π phase shift cannot be excluded. Робота присвячена одночасному дослідженню коливань потенціалу плазми на частотах ГАМ у різних областях токамака Т-10 та вивчення їх кореляційних властивостей. Недавні експерименти з використанням зондування плазми пучком важких іонів і ленгмюрівських зондів показують високий рівень когерентності між сигналами двох діагностик (до 0.8), не дивлячись на велику відстань між областями спостереження : половина тора у тороїдальному напрямку і близько π у полоїдальному, до 12 см – у радіальному. Фазовий зсув між коливаннями потенціалу, який вимірюється двома діагностиками, був отриманий у двох плазмових режимах. Найбільш ймовірно, що коливання потенціалу на частотах ГАМ поширюються назовні, хоча при цьому не можна виключати вплив "перескоку" фази на 2π. Работа посвящена одновременному исследованию колебаний потенциала плазмы на частотах ГАМ в различных областях токамака Т-10 и изучению их корреляционных свойств. Недавние эксперименты с использованием зондирования плазмы пучком тяжёлых ионов и ленгмюровских зондов показывают высокий уровень когерентности между сигналами двух диагностик (вплоть до 0.8), несмотря на большое расстояние между областями наблюдения: половина тора в тороидальном направлении и около π в полоидальном, до 12 см – в радиальном. Фазовый сдвиг между колебаниями потенциала, измеренный двумя диагностиками, был получен в двух плазменных режимах. Наиболее вероятно, что колебания потенциала на частотах ГАМ распространяются наружу, хотя при этом нельзя исключать влияние “перескока” фазы на 2π. 2018 Article Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak / V.N. Zenin, M.A. Drabinskij, L.G. Eliseev, S.A. Grashin, P.O. Khabanov, N.K. Kharchev, L.I. Krupnik, A.V. Melnikov // Вопросы атомной науки и техники. — 2018. — № 6. — С. 321-323. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 52.55.Fa, 52.35.Fp, 52.70.-m http://dspace.nbuv.gov.ua/handle/123456789/149076 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| language |
English |
| topic |
Диагностика плазмы Диагностика плазмы |
| spellingShingle |
Диагностика плазмы Диагностика плазмы Zenin, V.N. Drabinskij, M.A. Eliseev, L.G. Grashin, S.A. Khabanov, P.O. Kharchev, N.K. Krupnik, L.I. Melnikov, A.V. Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak Вопросы атомной науки и техники |
| description |
This work is dedicated to simultaneous measurements of plasma potential oscillations at GAM frequencies in
different locations on the T-10 tokamak and studying their correlation properties. Recent experiments with Heavy
Ion Beam Probing and Langmuir probes have shown high coherency between signals of two diagnostics (up to 0.8)
despite a large distance between the observation points: half of torus in toroidal and about π in poloidal direction, up
to 12 cm in radial direction. The phase shift between potentials measured with two diagnostics has been obtained in
two plasma scenarios. It was found the most likely that potential oscillations at the GAM frequency propagate
outward, but influence of 2π phase shift cannot be excluded. |
| format |
Article |
| author |
Zenin, V.N. Drabinskij, M.A. Eliseev, L.G. Grashin, S.A. Khabanov, P.O. Kharchev, N.K. Krupnik, L.I. Melnikov, A.V. |
| author_facet |
Zenin, V.N. Drabinskij, M.A. Eliseev, L.G. Grashin, S.A. Khabanov, P.O. Kharchev, N.K. Krupnik, L.I. Melnikov, A.V. |
| author_sort |
Zenin, V.N. |
| title |
Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak |
| title_short |
Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak |
| title_full |
Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak |
| title_fullStr |
Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak |
| title_full_unstemmed |
Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak |
| title_sort |
plasma potential correlations between heavy ion beam probe and langmuir probe on the т-10 tokamak |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2018 |
| topic_facet |
Диагностика плазмы |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/149076 |
| citation_txt |
Plasma potential correlations between heavy ion beam probe and langmuir probe on the Т-10 tokamak / V.N. Zenin, M.A. Drabinskij, L.G. Eliseev, S.A. Grashin, P.O. Khabanov, N.K. Kharchev, L.I. Krupnik, A.V. Melnikov // Вопросы атомной науки и техники. — 2018. — № 6. — С. 321-323. — Бібліогр.: 5 назв. — англ. |
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Вопросы атомной науки и техники |
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ISSN 1562-6016. ВАНТ. 2018. №6(118)
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2018, № 6. Series: Plasma Physics (118), p. 321-323. 321
PLASMA POTENTIAL CORRELATIONS BETWEEN HEAVY ION BEAM
PROBE AND LANGMUIR PROBE ON THE T-10 TOKAMAK
V.N. Zenin1, M.A. Drabinskij1, L.G. Eliseev1, S.A. Grashin1, P.O. Khabanov1, N.K. Kharchev1,
L.I. Krupnik2, A.V. Melnikov1,3
1NRC Kurchatov Institute, Moscow, Russia;
2National Science Center “Kharkov Institute of Physics and Technology“,
Institute of Plasma Physics, Kharkiv, Ukraine;
3National Research Nuclear University MEPhI, Moscow, Russia
This work is dedicated to simultaneous measurements of plasma potential oscillations at GAM frequencies in
different locations on the T-10 tokamak and studying their correlation properties. Recent experiments with Heavy
Ion Beam Probing and Langmuir probes have shown high coherency between signals of two diagnostics (up to 0.8)
despite a large distance between the observation points: half of torus in toroidal and about π in poloidal direction, up
to 12 cm in radial direction. The phase shift between potentials measured with two diagnostics has been obtained in
two plasma scenarios. It was found the most likely that potential oscillations at the GAM frequency propagate
outward, but influence of 2π phase shift cannot be excluded.
PACS: 52.55.Fa, 52.35.Fp, 52.70.-m
INTRODUCTION
In the recent years there has been significant interest
to Geodesic Acoustic Modes (GAMs). GAMs, being the
high-frequency counterpart of zonal flows, can be
generated by turbulence and regulate the turbulence in
return. It has been shown theoretically that GAMs
manifest themselves as oscillations of plasma electric
potential with m = n = 0 (and can weakly be seen on
density with m = 1, n = 0) [1, 2]. Present paper shows
the evidence of the long-range radial coherence for
GAM.
1. EXPERIMENTAL SETUP
GAMs have been studied with two diagnostics:
Langmuir probes (LP) [3] and Heavy Ion Beam Probing
(HIBP) [4, 5], a unique method for direct measurement
of the electric potential in the hot plasma core.
Diagnostics are separated by half of torus of the T-10
tokamak (R = 1.5 m, a = 0.3 m, B < 2.5 T). The top
view of T-10 tokamak is shown at Fig. 1. GAMs have
been studied in two plasma scenarios, presented in
Figs. 2 and 3, scenario 1 with B = 2.42 T, Ipl = 220 kA
and scenario 2 (B = 2.2 T, various currents Ipl = 230,
260, 280 kA).
Fig. 1. The top view of the T-10 tokamak
2. EXPERIMENTAL RESULTS
It was found that coherency between signals of two
diagnostics is up to 0.8. The value of coherency
decreases with increasing in radial distance between
HIBP sample volume and probes position at both
scenarios. The phase shift between electric potential
oscillation measured by HIBP and Langmuir probes has
also been measured. Spectrograms of potential
oscillations measured by HIBP, Langmuir probe,
coherence between oscillations of potential and phase
shift between them are shown in Fig. 4 and 5 for two
shots from different scenarios. We assume that phase
shift in toroidal and poloidal directions is equal to zero
because m = n = 0 for GAM. So we can relate it to
radial propagation of GAM. Radial distribution of
coherency and phase shift for scenario 1 are shown at
Fig. 6 (considered part of HIBP radial scan marked as
horizontal bar). If we assume that GAM is a propagating
wave we should expect phase shift Θ = Θ(ΔrHIBP/LP) is
monotonous function of the distance between
observation points.
Fig. 2. Time evolution of plasma parameters in
scenario 1
Fig. 3. Time evolution of plasma parameters
in scenario 2
322 ISSN 1562-6016. ВАНТ. 2018. №6(118)
This is true for Θ from scenario 1. So, under this
assumtion we can calculate its phase velocity by using
v = λυ = 2πΔrυ/Θ, where λ – wavelength; υ – GAM
frequency; Δr – radial distance between two observation
points; Θ – measured phase shift. Potential oscillations
at the GAM frequencies propagate outward at scenario 1
(negative Θ in case “inner point is a first argument”),
the magnitudes of phase velocity are also shown at
Fig. 6 (they change from ~ 2 km/s (Δr ≈ 2 cm) to ~
8.5 km/s (Δr ≈ 12 cm)).
Fig. 4. Spectrograms for scenario 1 (shot #71003)
Fig. 5. Spectrograms for scenario 2 (shot #72816)
Fig. 6. Radial distributions of maximum values of
coherence (averaged) and phase shifts Θ for scenario 1
The phase analysis for scenario 2 appears to be more
sophisticated. The histograms of phase shifts for two
typical shots are shown at Fig. 7. Note, that maximums
of distribution are near ±π. These data should be
analyzed in the link with the data from other shots.
Radial distribution of coherency and phase shift
(marked as black dots) for scenario 2 are shown at
Fig. 8. Note, that for scenario 2 experimental
Θ(ΔrHIBP/LP) are not monotonous. Furthermore, some of
them have positive values, others have negative values.
So, one should take into account an ambiguity of the Θ
determination with ±k·2π, where k is an integer number.
One may add an additional phase shift k·2π for various
k and obtain shifted data (marked as red and blue dots at
Fig. 8 for k=±1). The most likely monotonous functions
Θ = Θ(Δr) highlighted by ellipse at Fig. 8, has k=+1,
but other cases cannot be excluded.
Fig. 7. Examples of histograms of phase shifts with
peaks near ±π (shots from scenario 2)
Fig. 8. Radial distributions of maximum values of
coherence (averaged) and phase shifts Θ shifted by k·2π
for scenario 2
3. DISCUSSION
One should consider an ambiguity of the Θ
determination with ±k·2π for scenario 1 also. The cases
k=±1, 2 are shown at Fig. 9. The raw data (k=0) marked
by black dots remain the most likely case.
Fig. 9. Radial distributions of phase shifts
shifted by k·2π for scenario 1
Finally, the direction of the plasma potential
propagation in scenario 2 is still an open question. It
could be an inward propagation, and a possible reason
can be the difference in wall condition or ne evolution.
ISSN 1562-6016. ВАНТ. 2018. №6(118) 323
СONCLUSIONS
Potential oscillations at the frequencies of the GAM
have been studied with HIBP and Langmuir probes (LP)
in two scenarios with close plasma parameters. The
correlation between potentials by HIBP and LP is high
(up to 0.8) in spite of large distance between two
observation points (half of torus in toroidal and about π
in poloidal direction, up to 12 cm in radial direction). In
both scenarios the value of coherency decreases with
increasing in radial distance between HIBP sample
volume and probe positions. In the most likely case
potential oscillations at the GAM frequencies propagate
outward at scenario 1. The magnitude of phase velocity
changes from ~ 2 km/s (Δr ≈ 2 cm) to ~ 8.5 km/s
(Δr ≈ 12 cm) at scenario 1. There is an ambiguity in
experimental data at scenario 2.
ACKNOWLEDGEMENTS
The work of Kurchatov team was funded by Russian
Science Foundation (project 14-22-00193).
A.V. Melnikov was partly supported by the
Competitiveness Program of NRNU MEPhI.
REFERENCES
1. P.H. Diamond et al. Zonal flows in plasma – a review
// Plasma Phys. Control. Fusion. 2005, v. 47, № 5,
p. R35-R161.
2. A. Fujisawa et al. Experimental progress on zonal
flow physics in toroidal plasmas // Nucl. Fusion. 2007,
v. 47, № 10, p. S718-S726.
3. R.I. Solomatin, S.A. Grashin. Investigations of the
peripheral plasma by Langmuir probes on the T-10
tokamak // Probl. of At. Sci. and Technol. Ser.
“Thermonucl. Fusion“. 2017, v. 40, № 2, p. 43.
4. A.V. Melnikov et al. HIBP diagnostics on T-10 //
Rev. Sci. Instrum. 1995, v. 66, № 1, p. 317.
5. A.V. Melnikov et al. Heavy ion beam probing –
diagnostics to study potential and turbulence in toroidal
plasmas // Nucl. Fusion. 2017, v. 57, № 7, p. 072004.
Article received 15.10.2018
КОРРЕЛЯЦИИ ЭЛЕКТРИЧЕСКОГО ПОТЕНЦИАЛА НА ЧАСТОТЕ ГАМ МЕЖДУ ПЕРИФЕРИЕЙ
И ГОРЯЧЕЙ ЗОНОЙ ПЛАЗМЫ НА ТОКАМАКЕ Т-10
В.Н. Зенин, М.А. Драбинский, Л.Г. Елисеев, С.А. Грашин, Ф.О. Хабанов, Н.К. Харчев, Л.И. Крупник,
А.В. Мельников
Работа посвящена одновременному исследованию колебаний потенциала плазмы на частотах ГАМ в
различных областях токамака Т-10 и изучению их корреляционных свойств. Недавние эксперименты с
использованием зондирования плазмы пучком тяжёлых ионов и ленгмюровских зондов показывают
высокий уровень когерентности между сигналами двух диагностик (вплоть до 0.8), несмотря на большое
расстояние между областями наблюдения: половина тора в тороидальном направлении и около π в
полоидальном, до 12 см – в радиальном. Фазовый сдвиг между колебаниями потенциала, измеренный двумя
диагностиками, был получен в двух плазменных режимах. Наиболее вероятно, что колебания потенциала на
частотах ГАМ распространяются наружу, хотя при этом нельзя исключать влияние “перескока” фазы на 2π.
КОРЕЛЯЦІЇ ЕЛЕКТРИЧНОГО ПОТЕНЦІАЛУ НА ЧАСТОТІ ГАМ МІЖ ПЕРИФЕРІЄЮ
І ГАРЯЧОЮ ЗОНОЮ ПЛАЗМИ НА ТОКАМАЦІ Т-10
В.М. Зенін, М.О. Драбінський, Л.Г. Єлісєєв, С.А. Грашiн, Ф.O. Хабанов, М.К. Харчев, Л.І. Kрупнік,
О.В. Mельников
Робота присвячена одночасному дослідженню коливань потенціалу плазми на частотах ГАМ у різних
областях токамака Т-10 та вивчення їх кореляційних властивостей. Недавні експерименти з використанням
зондування плазми пучком важких іонів і ленгмюрівських зондів показують високий рівень когерентності
між сигналами двох діагностик (до 0.8), не дивлячись на велику відстань між областями спостереження :
половина тора у тороїдальному напрямку і близько π у полоїдальному, до 12 см – у радіальному. Фазовий
зсув між коливаннями потенціалу, який вимірюється двома діагностиками, був отриманий у двох плазмових
режимах. Найбільш ймовірно, що коливання потенціалу на частотах ГАМ поширюються назовні, хоча при
цьому не можна виключати вплив "перескоку" фази на 2π.
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