Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2002 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
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| Цитувати: | Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron / V.L. Berezhniy, A.I. Skibenko, I.P. Fomin, I.B. Pinos, V.L. Ocheretenko, O.S. Pavlichenko, Yu.Ya. Podoba, V.D. Kotsubanov, I.K. Nikol’skiy, N.I. Nazarov, S.A. Tsybenko, E.D. Volkov, V.V. Chechkin, A.S. Slavniy, A.P. Litvinov, A.Ye. Kulaga, K.Yamazaki, J. Miyazawa, V.S. Voitsenya, I.K. Tarasov // Вопросы атомной науки и техники. — 2002. — № 5. — С. 24-26. — Бібліогр.: 3 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859517633900052480 |
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| author | Berezhniy, V.L. Skibenko, A.I. Fomin, I.P. Pinos, I.B. Ocheretenko, V.L. Pavlichenko, O.S. Podoba, Yu.Ya. Kotsubanov, V.D. Nikol’skiy, I.K. Nazarov, N.I. Tsybenko, S.A. Volkov, E.D. Chechkin, V.V. Slavniy, A.S. Litvinov, A.P. Kulaga, A.Ye. Yamazaki, K. Miyazawa, J. Voitsenya, V.S. Tarasov, I.K. |
| author_facet | Berezhniy, V.L. Skibenko, A.I. Fomin, I.P. Pinos, I.B. Ocheretenko, V.L. Pavlichenko, O.S. Podoba, Yu.Ya. Kotsubanov, V.D. Nikol’skiy, I.K. Nazarov, N.I. Tsybenko, S.A. Volkov, E.D. Chechkin, V.V. Slavniy, A.S. Litvinov, A.P. Kulaga, A.Ye. Yamazaki, K. Miyazawa, J. Voitsenya, V.S. Tarasov, I.K. |
| citation_txt | Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron / V.L. Berezhniy, A.I. Skibenko, I.P. Fomin, I.B. Pinos, V.L. Ocheretenko, O.S. Pavlichenko, Yu.Ya. Podoba, V.D. Kotsubanov, I.K. Nikol’skiy, N.I. Nazarov, S.A. Tsybenko, E.D. Volkov, V.V. Chechkin, A.S. Slavniy, A.P. Litvinov, A.Ye. Kulaga, K.Yamazaki, J. Miyazawa, V.S. Voitsenya, I.K. Tarasov // Вопросы атомной науки и техники. — 2002. — № 5. — С. 24-26. — Бібліогр.: 3 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| first_indexed | 2025-11-25T20:47:28Z |
| format | Article |
| fulltext |
EVOLUTION OF PLASMA DENSITY, ITS FLUCTUATIONS
AND E×B ROTATION AFTER CARBON INJECTION
IN THE URAGAN-3M TORSATRON
V.L. Berezhniy, A.I. Skibenko, I.P. Fomin, I.B. Pinos, V.L. Ocheretenko, O.S. Pavlichenko,
Yu.Ya. Podoba, V.D. Kotsubanov, I.K. Nikol’skiy, N.I. Nazarov, S.A. Tsybenko, E.D. Volkov,
V.V. Chechkin, A.S. Slavniy, A.P. Litvinov, A.Ye. Kulaga, K.Yamazaki*, J. Miyazawa*,
V.S. Voitsenya, I.K. Tarasov
Institute of Plasma Physics, NSC KhIPT, Kharkov 61108, Ukraine
* National Institute for Fusion Studies, Toki, Japan
PACS: 52.55.Hc
1. INTRODUCTION
Carbon impurity diffusion in the Uragan-3M (U-3M)
torsatron with open helical divertor (l=3, m=9, R0=1 m, a
≅0.12 m) has been studied previously [1]. In these
experiments carbon atoms were injected in RF produced
plasma by laser ablation of solid carbon target put inside
of vacuum chamber. Injected atom number could be
changed in the range 1016 -6.1017 atoms by changing laser
pulse energy. It was observed that plasma time response
on carbon injection depended strongly on injected atoms
amount (Fig.1): with evolution time corresponding to
impurity diffusion (∆t≈5 ms) – at low carbon amount (a)
and one corresponding to plasma diffusion (∆t≈20 ms) –
at larger carbon amount (b). Impurity diffusion was
studied at low injected carbon amount. Plasma response
on impurity injection depended also on plasma density.
Fig.1 Plasma parameter behavior during carbon
injection at 312108)0( −⋅= cmne [a) - FL=3 J/cm-2,
b) FL = 15 J/cm-2].
Studies of dependence of ionized carbon impurity
lines on carbon atom influx showed nonlinear dependence
of ratio CV/CII lines intensity on CII intensity that was
interpreted as result of change of screening efficiency of
divertor layer plasma due to it radiative cooling. In this
report we present results of studies of plasma density
evolution at injected carbon amount corresponding to case
b) of Fig.1 (FL = 10÷15 J/cm-2) at different values of
plasma density.
2. EXPERIMENT
Hydrogen plasma in the U-3M torsatron was
produced and heated by RF power absorption at ω≈ωci at
constant gas flow-in. Frame type antenna [2] was used for
RF power (up to 200 KW) excitation of antenna.
In these experiments most data were obtained by
using 4-channel microwave homodyne reflectometer
(Fig.2) with plasma probing by both O- and X- modes [3].
Line-integrated density < lne > was measured by 2-mm
interferometer, electron temperature – by ECE and ion
temperature – by NPA.
Fig.2. Reflectometer antenna setup at "U-3М":
1- outboard antenna (Х-mode), 2- inboard antenna (O-
mode), 3- outboard antenna (O-mode), 4- vertical antenna
(O-mode), 5- carbon target in other poloidal crossection).
Typical behavior of plasma density in discharges
with high electron density is shown on Fig.3 a. Injection
of ≈1% of carbon atoms resulted in rather strong and
nontrivial change of density behavior (Fig.3 b): the fast
(≈0.5 ms) drop down of ne by ≈ 15%, fast (≈1 ms)
increase it up to almost the same value and second
decrease of ne with establishing of a new quasistationary
state.
24 Problems of Atomic Science and Technology. 2002. № 5. Series: Plasma Physics (8). P. 24-26
Fig.3. Time behavior of line-integrated plasma density in
U-3M ( a – without, b- with C injection).
Analysis of reflected signals (Fig.4), corresponding
reflection from different plasma radiuses showed some
outward movement of outside plasma layer (ncr=1.7∙1012 cm-3)
during this fast drop-down and up phase (Figs.3b, 6a).
Fig.4 Reflected wave amplitude before and during
injection : (1)- outboard probing (Ncr=1,7.1012 cm-3), 2)
and 3) inboard and outboard probing (Ncr=4.1012 cm-3)
Simultaneous 4 line-of-views probing of plasma by
O-mode with the same frequency allowed studying the
spectral properties and correlation between fluctuations in
different poloidal locations. Some conclusions from these
studies:
1) impurity injection results in change of spectrum of
fluctuations – with increase its part below ≈ 20 KHz
and decrease the part above 20 KHz (Fig.5);
Fig.5. Density fluctuation spectra (1- prior to , 2 –
during injection).
2) during this fast change phase radial correlation length
is changing too (Fig.6b);
3) poloidal rotation velocity of studied plasma layers
decreased and changed direction (Fig.6c).
Fig.6. Time behavior of plasma parameters with
carbon injection at 38 ms (a- line-integrated plasma
density, b- correlation length betwin two radial plasma
layers, c- velocity of poloidal rotation
If the hydrogen pressure was decreasing, the density
build up was slower and resulting density was lower. An
example of such discharges is shown in Fig.7-1. At this
specific base pressure (≈ 5.10-6 tor) electron line-averaged
density reaches value of 12105,2 ⋅ cm-3 at the moment of
RF turn off but then increase up 12104 ⋅ cm-3 and then
slowly decays. This is behavior similar to one shown on
Fig.1. Injection of 2.1016 C atoms triggered faster density
build resulted in a higher density (Fig.7-2).
Fig.7. Time behavior of line-integrated plasma density in
U-3M ( 1 – without, 2- with C injection).
25
3. DISCUSSION
To understand observed phenomena during impurity
injection in U-3M torsatron, one must take into account 2
distinct peculiarities of experiment: 1) strong dependence
of RF power deposition profile on electron density [2] and
2) existence of scrape-off plasma layer (SOL) at confined
plasma border. Plasma density behavior in discharge is
result of concurrent processes - gas ionization and particle
diffusion. In simplest form for averaged electron density
analysis one can use an equation
dne/dt= Γ – ne/τn, (1)
where Γ is source term describing ionization of hydrogen
atoms going into plasma and second term is describing
electron diffusion characterized by particle confinement
time τn.
For cylindrical geometry
Γ=
a
vn aa2
where na and va – density and velocity of H atoms at
plasma border a. In magnetic configuration of torsatron
with divertor the atom flux on confined plasma border a
is partly absorbed by SOL. The value of this flux can be
described as
)()( bAa Γ⋅=Γ
where )(aΓ - hydrogen flux at plasma boundary, )(bΓ -
the one at the SOL boundary b, A=
)
)()(
exp(
a
a
b
eei
v
dxxnTS ∫⋅
−
- attenuation factor of SOL
( )( ei TS - hydrogen ionization rate coefficient).
Carbon atom injection can result in increase of
electron density in divertor layer ( ∫
a
b
e dxxn )( ), in
decrease of )( ei TS due to radiation cooling thus giving
decrease and increase of atom density at plasma border.
Fast change of poloidal rotation may reflect change of
diffusion process thus influencing the second term (τn) in
eq.1. This change may be a result of RF power deposition
profile due to change of electron density profile at plasma
edge during impurity injection.
These considerations are used here to show that the
full picture of electron density perturbation influence on
particle balance in torsatron with divertor and RF power
deposition is very complicated and needs more thorough
studies. This is the topic of our further studies.
This work was carried out in collaboration with NIFS
(Japan) under the program LIME.
REFERENCES
[1] Ja.F. Volkov, G.V. Zelenin, V.D. Kotsubanov, I.K.
Nikol’skiy, O.S. Pavlichenko. Impurity transport studies
for U-3 torsatron via laser ablation of solid target. Proc.
of the 5th Intern. Symposium on Laser-Aided Plasma
Diagnostic (Bad-Honnef), 1991, p.210.
[2] E.D. Volkov, I.Yu. Adamov, A.V. Arsen’ev et al.
Confinement of RF heated plasma in the Uragan-3M
torsatron. Proc. of 14 IAEA Conference (Wurzburg),v. 2
(1993) p.679.
[3] A.I. Skibenko, V.L. Berezhniy, E.D. Volkov et al.
Radial profiles of plasma density and poloidal rotation
velocity measured by microwave reflectometry for
different regimes of RF plasma production in "Uragan-
3M" torsatron. Problems of Atomic Science and
Technology, Series “Plasma Physics” #6 (2000) p.47.
26
IN THE URAGAN-3M TORSATRON
Institute of Plasma Physics, NSC KhIPT, Kharkov 61108, Ukraine
References
|
| id | nasplib_isofts_kiev_ua-123456789-77869 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-25T20:47:28Z |
| publishDate | 2002 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Berezhniy, V.L. Skibenko, A.I. Fomin, I.P. Pinos, I.B. Ocheretenko, V.L. Pavlichenko, O.S. Podoba, Yu.Ya. Kotsubanov, V.D. Nikol’skiy, I.K. Nazarov, N.I. Tsybenko, S.A. Volkov, E.D. Chechkin, V.V. Slavniy, A.S. Litvinov, A.P. Kulaga, A.Ye. Yamazaki, K. Miyazawa, J. Voitsenya, V.S. Tarasov, I.K. 2015-03-08T19:22:40Z 2015-03-08T19:22:40Z 2002 Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron / V.L. Berezhniy, A.I. Skibenko, I.P. Fomin, I.B. Pinos, V.L. Ocheretenko, O.S. Pavlichenko, Yu.Ya. Podoba, V.D. Kotsubanov, I.K. Nikol’skiy, N.I. Nazarov, S.A. Tsybenko, E.D. Volkov, V.V. Chechkin, A.S. Slavniy, A.P. Litvinov, A.Ye. Kulaga, K.Yamazaki, J. Miyazawa, V.S. Voitsenya, I.K. Tarasov // Вопросы атомной науки и техники. — 2002. — № 5. — С. 24-26. — Бібліогр.: 3 назв. — англ. 1562-6016 PACS: 52.55.Hc https://nasplib.isofts.kiev.ua/handle/123456789/77869 This work was carried out in collaboration with NIFS(Japan) under the program LIME. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Magnetic confinement Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron Article published earlier |
| spellingShingle | Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron Berezhniy, V.L. Skibenko, A.I. Fomin, I.P. Pinos, I.B. Ocheretenko, V.L. Pavlichenko, O.S. Podoba, Yu.Ya. Kotsubanov, V.D. Nikol’skiy, I.K. Nazarov, N.I. Tsybenko, S.A. Volkov, E.D. Chechkin, V.V. Slavniy, A.S. Litvinov, A.P. Kulaga, A.Ye. Yamazaki, K. Miyazawa, J. Voitsenya, V.S. Tarasov, I.K. Magnetic confinement |
| title | Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron |
| title_full | Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron |
| title_fullStr | Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron |
| title_full_unstemmed | Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron |
| title_short | Evolution of plasma density, its fluctuations and E×B rotation after carbon injection in the Uragan-3M torsatron |
| title_sort | evolution of plasma density, its fluctuations and e×b rotation after carbon injection in the uragan-3m torsatron |
| topic | Magnetic confinement |
| topic_facet | Magnetic confinement |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/77869 |
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