Electromagnetic oscillations at the edge of the Uragan-3M plasma
In the Uragan-3M torsatron the plasma is ICRF heated with the use of antennas of different types. The objective of this work is to study the electromagnetic wave propagation outside the plasma confinement volume and the effect of these waves on confined plasma behavior during RF-heating.
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2013
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| Цитувати: | Electromagnetic oscillations at the edge of the Uragan-3M plasma / V.K. Pashnev, I.K. Tarasov, M.I. Tarasov, D.A. Sitnikov, S.A. Tsybenko, I.B. Pinos, K.N. Stepanov, V.V. Olshansky, O.M. Shvets, E.L. Sorokovoy, A.A. Petrushenya, A.V. Lozin, A.P. Pugovkin, Yu.K. Mironov, A.N. Shapoval // Вопросы атомной науки и техники. — 2013. — № 1. — С. 45-47. — Бібліогр.: 3 назв. — англ. |
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irk-123456789-1092452016-11-22T03:03:38Z Electromagnetic oscillations at the edge of the Uragan-3M plasma Pashnev, V.K. Tarasov, I.K. Tarasov, M.I. Sitnikov, D.A. Tsybenko, S.A. Pinos, I.B. Stepanov, K.N. Olshansky, V.V. Shvets, O.M. Sorokovoy, E.L. Petrushenya, A.A. Lozin, A.V. Pugovkin, A.P. Mironov, Yu.K. Shapoval, A.N. Магнитное удержание In the Uragan-3M torsatron the plasma is ICRF heated with the use of antennas of different types. The objective of this work is to study the electromagnetic wave propagation outside the plasma confinement volume and the effect of these waves on confined plasma behavior during RF-heating. В торсатроне Ураган-3М плазма нагревается ВЧ-волнами вблизи ионно-циклотронного резонанса антеннами различных типов. Целью настоящей работы является изучение распространения электромагнитных волн вне объема удержания и влияния этих волн на параметры плазмы в течение разряда. У торсатроні Ураган-3М плазма нагрівається ВЧ-хвилями поблизу іонного-циклотронного резонансу антенами різних типів. Метою цієї роботи є вивчення поширення електромагнітних хвиль поза обсягу утримання і впливу цих хвиль на параметри плазми протягом розряду. 2013 2013 Article Electromagnetic oscillations at the edge of the Uragan-3M plasma / V.K. Pashnev, I.K. Tarasov, M.I. Tarasov, D.A. Sitnikov, S.A. Tsybenko, I.B. Pinos, K.N. Stepanov, V.V. Olshansky, O.M. Shvets, E.L. Sorokovoy, A.A. Petrushenya, A.V. Lozin, A.P. Pugovkin, Yu.K. Mironov, A.N. Shapoval // Вопросы атомной науки и техники. — 2013. — № 1. — С. 45-47. — Бібліогр.: 3 назв. — англ. 1562-6016 PACS: 52.55.Dy, 52.55.Hc http://dspace.nbuv.gov.ua/handle/123456789/109245 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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English |
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Магнитное удержание Магнитное удержание |
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Магнитное удержание Магнитное удержание Pashnev, V.K. Tarasov, I.K. Tarasov, M.I. Sitnikov, D.A. Tsybenko, S.A. Pinos, I.B. Stepanov, K.N. Olshansky, V.V. Shvets, O.M. Sorokovoy, E.L. Petrushenya, A.A. Lozin, A.V. Pugovkin, A.P. Mironov, Yu.K. Shapoval, A.N. Electromagnetic oscillations at the edge of the Uragan-3M plasma Вопросы атомной науки и техники |
| description |
In the Uragan-3M torsatron the plasma is ICRF heated with the use of antennas of different types. The objective of this work is to study the electromagnetic wave propagation outside the plasma confinement volume and the effect of these waves on confined plasma behavior during RF-heating. |
| format |
Article |
| author |
Pashnev, V.K. Tarasov, I.K. Tarasov, M.I. Sitnikov, D.A. Tsybenko, S.A. Pinos, I.B. Stepanov, K.N. Olshansky, V.V. Shvets, O.M. Sorokovoy, E.L. Petrushenya, A.A. Lozin, A.V. Pugovkin, A.P. Mironov, Yu.K. Shapoval, A.N. |
| author_facet |
Pashnev, V.K. Tarasov, I.K. Tarasov, M.I. Sitnikov, D.A. Tsybenko, S.A. Pinos, I.B. Stepanov, K.N. Olshansky, V.V. Shvets, O.M. Sorokovoy, E.L. Petrushenya, A.A. Lozin, A.V. Pugovkin, A.P. Mironov, Yu.K. Shapoval, A.N. |
| author_sort |
Pashnev, V.K. |
| title |
Electromagnetic oscillations at the edge of the Uragan-3M plasma |
| title_short |
Electromagnetic oscillations at the edge of the Uragan-3M plasma |
| title_full |
Electromagnetic oscillations at the edge of the Uragan-3M plasma |
| title_fullStr |
Electromagnetic oscillations at the edge of the Uragan-3M plasma |
| title_full_unstemmed |
Electromagnetic oscillations at the edge of the Uragan-3M plasma |
| title_sort |
electromagnetic oscillations at the edge of the uragan-3m plasma |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2013 |
| topic_facet |
Магнитное удержание |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/109245 |
| citation_txt |
Electromagnetic oscillations at the edge of the Uragan-3M plasma / V.K. Pashnev, I.K. Tarasov, M.I. Tarasov, D.A. Sitnikov, S.A. Tsybenko, I.B. Pinos, K.N. Stepanov, V.V. Olshansky, O.M. Shvets, E.L. Sorokovoy, A.A. Petrushenya, A.V. Lozin, A.P. Pugovkin, Yu.K. Mironov, A.N. Shapoval // Вопросы атомной науки и техники. — 2013. — № 1. — С. 45-47. — Бібліогр.: 3 назв. — англ. |
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Вопросы атомной науки и техники |
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ISSN 1562-6016. ВАНТ. 2013. №1(83) 45
ELECTROMAGNETIC OSCILLATIONS AT THE EDGE OF THE
URAGAN-3M PLASMA
V.K. Pashnev, I.K. Tarasov, M.I. Tarasov, D.A. Sitnikov, S.A. Tsybenko, I.B. Pinos,
K.N. Stepanov, V.V. Olshansky, O.M. Shvets, E.L. Sorokovoy, A.A. Petrushenya, A.V. Lozin,
A.P. Pugovkin, Yu.K. Mironov, A.N. Shapoval
Institute of Plasma Physics NSC “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
In the Uragan-3M torsatron the plasma is ICRF heated with the use of antennas of different types. The objective of this
work is to study the electromagnetic wave propagation outside the plasma confinement volume and the effect of these
waves on confined plasma behavior during RF-heating.
PACS: 52.55.Dy, 52.55.Hc
INTRODUCTION
In our experiments we used the so-called “frame” and
“three-half-turn” unshielded antennas [1]. With this heating
technique, it was believed for a long time that almost all
the power irradiated by antenna was absorbed by the
plasma in the confinement volume and there are no
electromagnetic waves between the helical coils and the
plasma. Also, it was believed that non-propagating
electromagnetic oscillations are generated within the
antenna area. Later on, it was shown [2, 3] that the RF
power absorbed in the confined plasma is only a small part
of that irradiated by the antenna. The problem is where the
rest of the power is absorbed and what its effect is on
plasma behavior in the confinement volume. Basing on the
experimental data obtained here, it is suggested that
electromagnetic waves propagate outside the confinement
volume too. These waves ionize and heat the plasma with
the density of ne ≈ 109…1011 cm-3, which screens the
fuelling gas entering the confinement volume. The term
“RF plasma screening” was also proposed [3].
EXPERIMENTAL CONDITIONS
AND RESULTS
To study electromagnetic waves that propagate away
from the antennae outside the region of plasma
confinement away during the RF heating (Fig. 1), two
magnetic probe arrays are used located in the spacing
between the helical winding and the confinement region.
Probes close to the confinement volume are located 2 cm
distant from it, the distance between the arrays being
l = 3 cm. Each array consists of 3 coils oriented on 3
orthogonal components of the magnetic field. Since the
radiation pattern of probes is not acute, there is an evident
coupling between the probes of one array. The A1 antenna
current is recorded using a special loop. The bandwidth of
the magnetic probes with the recording section attains
80 MHz, and that of the loops measuring the antenna
current exceed 140 MHz. The fundamental frequency
where the plasma heating is observed is near 9 MHz and
differs for various antennas. The analysis of the signals
picked up by the probes is carried out using the correlation
analysis.
The effect of RF waves propagating outside the
confinement volume on plasma behavior in the
confinement volume is studied using a 2 mm
interferometer to determine the average density, a
sensor of soft X-Ray radiation and optical systems
recording radiation from the plasma in the visible range.
In this operational mode of RF generator plasma
does not have an effect on current in the antenna and the
oscillation spectrum shown in Fig. 2 corresponds to the
fundamental frequency of the RF generator. The
spectrum of the antenna current is rather wide (about 6
MHz half-width). There are also higher frequencies, up
to 80 MHz. The phase shift φ between the antenna
current and probe is 0 or π over the whole frequency
range studied.
As is shown in Figs. 3 and 4 where the plasma is RF
heated at the average density ne ≤ 2x1012 cm-3 in the
confinement volume, using the frame antenna, the
frequency spectrum of the antenna current changes
significantly.
Fig. 1. Helical windings of the Uragan-3M torsatron.
The poloidal cross-section where the magnetic probes
(MP) are placed is indicated by the dashed line. The
sectors where the frame and three-half-turn antennae
are installed are labeled as A1 and A2, respectively.
MC - loop recording current in the antenna A1
Fig. 2. Oscillation spectrum of the frame antenna
current without plasma
46 ISSN 1562-6016. ВАНТ. 2013. №1(83)
Time behavior of the current in the antenna and signals
from two probes similarly oriented in the radial
direction 3 cm separated from each other is presented in
Fig. 3. The results of processing of these signals are
shown in Fig. 4.
Fig. 3. Signals from the radially oriented magnetic
probes 1 and 2 and antenna current 4 with plasma
heating using the frame antenna
Fig. 3 shows time behavior of signals from different
groups of probes (traces 1 and 2) and current in antenna
(trace 4). It is clear that the probe signals are of one order
by amplitude. Their spectra of oscillations are given in the
Fig. 4 where frequencies up to f ≈ 100 MHz are observed.
However, oscillations in the f ≤ 25 MHz region dominate
in their amplitude. The low-frequency parts of the spectra
taken from the probes (f ≤ 20 MHz) differ significantly. In
one of the probe harmonics with f ≈ 10 MHz dominate,
while the frequencies f = 10 and 20 MHz dominate in
another probe. This spectrum is similar to that of the
antenna current. The phase shift between the oscillations
from different probes indicates the presence of the radial
phase velocity for waves propagating in the space between
the confinement volume and helical winding.
Fig. 4. Results of processing of signals shown in φ1,2
and φ1,4, phase shifts at different frequencies for probes
1…2 and 1…4;C1,2 and C1,4, coherence spectra; S1, S2,
S4, auto-spectra of signals from probes 1, 2 and 4,
respectively
The phase velocities of these waves πϕ 2flVph =
have different direction for different frequencies of the
spectrum, their values increase with frequency and lie in
the range of Vph=2·106 … 4·107 cm/s. A typical feature of
this heating regime is an increase of oscillations with
frequencies f = 15 and 20 MHz, so that the amplitude of
these oscillations is comparable to the amplitude on the
main frequency f ≈ 9 MHz. So, there are conditions for
oscillations at f ≈ 20 MHz with ciωω ≈ 1.6, to propagate
in the plasma. The role of these oscillations on plasma
heating has not been cleared yet.
In the plasma heating regimes where the frame and tree-
half turn antennae heat the plasma simultaneously, the
amplitudes of the high frequency oscillations (up to
80 MHz) undergo a significant increase (Figs. 5, 6) and
become comparable to those at the fundamental frequency
f ≈ 10 MHz. A typical feature of this heating regime is the
absence of correlation between the groups of probes on the
frequency of f ≈ 20 MHz. The phase velocities of wave
propagation in this regime are similar to those in the
previous case.
Fig. 5. Signals from poloidally oriented magnetic
probes 1 and 2 placed in different probe arrays and
frame antenna current 4 with plasma heating using
frame and three-half-turn antennae simultaneously. S1,
S2, S4, auto-spectra of signals from probes 1, 2 and 4,
respectively
Fig. 6. Results of processing of signals shown in φ1,2
and φ1,4, phase shifts at different frequencies for probes
1…2 and 1…4;C1,2 and C1,4, coherence spectra; S1, S2,
S4, auto-spectra of signals from probes 1, 2 and 4,
respectively
ISSN 1562-6016. ВАНТ. 2013. №1(83) 47
Absorption of powerful electromagnetic oscillations in a
thin plasma layer outside the confinement volume should
result in heating of this plasma despite a small time of
particle confinement here. However, it is the low
confinement time that causes a significant increase of
plasma bombarding the metal environment and increase of
impurity release. Besides, the plasma outside the
confinement volume could ionize the neutral gas, thereby
limiting its influx into this volume.
In order to verify these assumptions, a special
experiment was carried out. At a certain moment of
discharge the RF power irradiated by the antenna was
suddenly raised, and corresponding changes in plasma
parameters in the confinement volume were recorded
(Fig. 7).
Fig. 7. Effects of RF heating power W increase on
plasma density ne in the confinement volume, the
intensity of soft X ray UXRay, carbon ICIII and chromium
ICrIII lines
CONCLUSIONS
Using magnetic probes located outside the
confinement volume, it is shown that electromagnetic
waves relating to the RF plasma heating propagate in
this space. The frequency spectrum of these waves
depends on heating features and its high frequency part
could be related to the development of plasma
instabilities. Estimations show that the RF power spent
for generation of these waves could exceed 100 kW.
The interaction of RF waves outside the confinement
volume with the low-density plasma strongly affects
plasma behavior in the confinement volume. The
following effects were observed:
- screening of the hydrogen influx to the confinement
volume (RF screening);
- impurity influx rise from metallic components
facing the plasma, and from the antennas, first of
all.
REFERENCES
1. V.E. Moiseenko, V.L. Berezhnyj, V.N. Bondarenko,
et al. RF plasma production and heating below ion-
cyclotron frequencies in Uragan torsatrons // Nucl.
Fusion. 2011, v. 51, p. 083036.
2. V.L. Berezhnyj, V.S. Voitsenya, M.P. Vasil'ev, et al.
// Fizika plazmy. 1990, v. 15, p. 523-536 (in Russian).
3. V.K. Pashnev, P.Ya. Burchenko, A.V. Lozin, et al.
Energy confinement in the torsatron Uragan-3M during
the RF-heating mode // Problems of Atomic Science and
Technology. Series “Plasma Physics” (14). 2008, № 6,
p. 28-30.
Article received 01.11.12
ЭЛЕКТРОМАГНИТНЫЕ КОЛЕБАНИЯ В ПЕРИФЕРИЙНОЙ ПЛАЗМЕ УРАГАН-3M
В.К. Пашнев, И.К. Тарасов, М.И. Тарасов, Д.А. Ситников, С.А. Цыбенко, И.Б. Пинос, К.Н. Степанов,
В.В. Ольшанский, О.М. Швец, Э.Л. Сороковой, А.А. Петрушеня, А.В. Лозин, А.П. Пуговкин,
Ю.К. Миронов, А.Н. Шаповал
В торсатроне Ураган-3М плазма нагревается ВЧ-волнами вблизи ионно-циклотронного резонанса
антеннами различных типов. Целью настоящей работы является изучение распространения
электромагнитных волн вне объема удержания и влияния этих волн на параметры плазмы в течение разряда.
ЕЛЕКТРОМАГНІТНІ КОЛИВАННЯ В ПЕРИФЕРІЙНІЙ ПЛАЗМІ УРАГАН-3M
В.К. Пашнєв, І.К. Тарасов, М.І. Тарасов, Д.А. Сiтников, С.А. Цибенко, І.Б. Пінос, К.М. Степанов,
В.В. Ольшанський, О.М. Швець, Е.Л. Сороковий, А.А. Петрушеня, O.В. Лозін, А.П. Пуговкiн,
Ю.К. Міронов, А.М. Шаповал
У торсатроні Ураган-3М плазма нагрівається ВЧ-хвилями поблизу іонного-циклотронного резонансу
антенами різних типів. Метою цієї роботи є вивчення поширення електромагнітних хвиль поза обсягу
утримання і впливу цих хвиль на параметри плазми протягом розряду.
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