Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron
The results of local measurements of RF discharge plasma parameters (plasma density and its fluctuations, electron temperature and energy of superthermal electrons, plasma poloidal rotation velocity) in the Uragam-3M torsatron are presented. The obtained data are analyzed taking into account the pec...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2000 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Цитувати: | Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron / E.D. Volkov, I.Yu. Adamov, V.L. Berezhnyj, A.E. Kulaga, N.I. Nazarov, V.L. Ocheretenko, I.B. Pinos, T.E. Shcherbinina, A.I. Skibenko, A.S. Slavnyj, I.K. Tarasov, I.P. Fomin // Вопросы атомной науки и техники. — 2000. — № 6. — С. 21-23. — Бібліогр.: 3 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860069933875986432 |
|---|---|
| author | Volkov, E.D. Adamov, I.Yu. Berezhnyj, V.L. Kulaga, A.E. Nazarov, N.I. Ocheretenko, V.L. Pinos, I.B. Shcherbinina, T.E. Skibenko, A.I. Slavnyj, A.S. Tarasov, I.K. Fomin, I.P. |
| author_facet | Volkov, E.D. Adamov, I.Yu. Berezhnyj, V.L. Kulaga, A.E. Nazarov, N.I. Ocheretenko, V.L. Pinos, I.B. Shcherbinina, T.E. Skibenko, A.I. Slavnyj, A.S. Tarasov, I.K. Fomin, I.P. |
| citation_txt | Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron / E.D. Volkov, I.Yu. Adamov, V.L. Berezhnyj, A.E. Kulaga, N.I. Nazarov, V.L. Ocheretenko, I.B. Pinos, T.E. Shcherbinina, A.I. Skibenko, A.S. Slavnyj, I.K. Tarasov, I.P. Fomin // Вопросы атомной науки и техники. — 2000. — № 6. — С. 21-23. — Бібліогр.: 3 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | The results of local measurements of RF discharge plasma parameters (plasma density and its fluctuations, electron temperature and energy of superthermal electrons, plasma poloidal rotation velocity) in the Uragam-3M torsatron are presented. The obtained data are analyzed taking into account the peculiarities of the Uragan-3M magnetic configuration and scenario of RF plasma production and heating. Some suppositions about mechanisms of a radial electric field generation are discussed with the calculation of a magnetic configuration island structure.
|
| first_indexed | 2025-12-07T17:10:13Z |
| format | Article |
| fulltext |
UDC 533.9
Problems of Atomic Science and Technology. 2000. № 6. Series: Plasma Physics (6). p. 21-23 21
RADIAL DISTRIBUTIONS OF RF DISCHARGE PLASMA PARAMETERS
AND RADIAL ELECTRIC FIELD IN THE URAGAN-3M TORSATRON
E.D.Volkov, I.Yu.Adamov, V.L.Berezhnyj, A.E.Kulaga, N.I.Nazarov, V.L.Ocheretenko,
I.B.Pinos, T.E.Shcherbinina*, A.I.Skibenko, A.S.Slavnyj, I.K.Tarasov, I.P.Fomin
Institute of Plasma Physics, National Science Center “Kharkov Institute of Physics and
Technology”, Kharkov 61108, Ukraine
*National Technical University “Kharkov Polytechnic Institute”, Kharkov 61108, Ukraine
The results of local measurements of RF discharge plasma parameters (plasma density and its fluctuations,
electron temperature and energy of superthermal electrons, plasma poloidal rotation velocity) in the Uragam-3M
torsatron are presented. The obtained data are analyzed taking into account the peculiarities of the Uragan-3M
magnetic configuration and scenario of RF plasma production and heating. Some suppositions about mechanisms
of a radial electric field generation are discussed with the calculation of a magnetic configuration island structure.
1. Introduction
It has been demonstrated in a variety of toroidal
devices that Er x B velocity shear is a key mechanism
which can explain the reduction of plasma turbulence
and the formation of transport barriers leading to
improvement of plasma confinement. In accordance
with the theory radial electric field can be determined
from the equation:
θθ BVBVP
eZn
E oi
ii
r //
1 +−∇= ,
where ni is the ion density, Pi is the ion pressure, Zie
and e are the charges of the ion and electron, Vθ and V//
are the poloidal and toroidal rotation velocities, and Bθ
and Bo are the poloidal and toroidal magnetic fields.
It is necessary to note that plasma rotation velocities
can be conditioned by a power deposition profile in the
plasma column, the ion-electron flux difference in the
vicinity of rational magnetic surfaces and presence of
fast particles generated in the process of plasma heating.
In connection with this the study of profile effects has
the very important meaning for the explanation of radial
electric field generation. The case of the presence of
island chains of low order resonant surfaces in a
magnetic configuration with small shear with sufficient
heating power in the region of their localization is most
interesting for the study in accordance with the point of
view which the theory develops now.
2. Experimental arrangement
Experiments were carried out on the Uragan-3M
torsatron with open helical divertor (l=3, m=9,
Ro=100cm, apl=12,6 cm) at the magnetic field strength
Bo=0,72 T.
The measurements made by the triode and
luminescent techniques have shown that there is the
possibility to realize the magnetic configuration with
two chains of islands, which are located in the region of
small shear [1]. Such a configuration takes place at the
ratio of vertical magnetic field to longitudinal one
B⊥ /Bo~1,25%. The outside shift of the magnetic axis
from the geometrical axis of helical coils is equal to
5,5cm in this case (Fig.1).
Fig. 1. The magnetic island structure of the Uragan-
3M torsatron at B⊥ /Bo~1,25%
The frame type antenna was used for RF plasma
production and heating to provide a sufficient heating
power in the region of island chains localization.
Numerical simulations has shown that the waves with
long wavelength excited by this antenna are absorbed at
the external part of a plasma column, r /a >0,5, where
island chains are located (Fig.2).
Fig.2. The power deposition profile for the frame
type antenna
22
Radial distributions of plasma density and its
fluctuations (multichord interferometry and
reflectometry), electron temperature (ECE diagnostics
and laser scattering) and plasma poloidal rotation
velocity (poloidal correlation reflectometry) have been
measured. The energy spectra of charge exchange
neutrals were measured in tangential and perpendicular
directions to the toroidal plane by neutral particle
analysers. Some data were obtained by means of probe
and electrotechnical measurements.
3. Experimental results
The experiments were carried out in the range of
plasma densities 2.1012<ne<5.1012 cm-3 to provide the
power deposition profile shown in Fig. 2.
The spectrum of electron cyclotron emission in the
frequency range from the first to the second harmonic
was measured by three heterodine radiometers with
spectral resolution ∇ω /2ωce~0,038% and threshold
sensitivity ~0,5 eV. The spectrum of emission (Fig.3) at
ω=2ωce is clouse to
Fig.3.The spectrum of ECE
the thermal one, but it has peculiarities in the long-
wavelength region ω/ωce<1,85 and in the short-
wavelength region in the vicinity of frequencies ω ≈2,02
ωce and ω≈2,1ωce. The maximum of the emission is
observed at B/Bo =0,96 that is on the axis of the
magnetic configuration. It is easy to see that the
deviations of the measured spectrum from thermal one
in the short-wavelength part correspond to local maxima
of electron temperature in magnetic islands (Fig.4).
The peculiarity of the spectrum in the long-wavelength
region ω/ωce~1,85 corresponds to the localization of fast
electrons with energy about of 1,2 keV on the plasma
edge [2].
Numerical simulation has shown that the power
deposition profile provided by frame type antenna shifts
to the plasma periphery with the density rise.
The energy spectra of charge exchange neutral
measured in tangential and perpendicular directions to
the toroidal plane show a two temperature ion
distribution (Ti1≈300 eV, Ti2 ≈800 eV). Doppler
broadening of the CV line (227,1 nm) indicates that
these impurity ions are in equilibrium with the lower
temperature part of the hydrogen ion distribution
Ti (CV)≈Ti1 during almost the whole RF pulse duration
[3].
-20.00 -10.00 0.00 10.00 20.00
0.00
100.00
200.00
300.00
400.00
r,cm
Te,eV
Fig. 4. The radial distribution of the electron
temperature
Measurements with changing the entrance slit width of
the longitudinal and perpendicular charge exchange
analysers indicate that high energy ion generation
takes place at the plasma edge and the region of their
localization moves outside with the density rise too. It is
necessary to note that these peculiarities of Te(r) and the
presence of fast electrons and ions were observed during
all quasistationary stage of the RF discharge and
disappeared through ~150 µs after RF pulse was
switched off.
It was interesting to study an asymmetry of
plasma density profile and its fluctuations relative to
magnetic axis determined by magnetic field
configuration and the method of plasma production and
heating. The microwave interferomtry (λ=2-8 mm) and
reflectometry (λ=8-17 mm) were used for the density
profile reconstruction. The density fluctuation level was
estimated from reflected signal phase fluctuations
measured by cross-detection technique. Radial profiles
of wave numbers, coherency and correlation length
were measured by dual-polarization radial correlation
reflectometry, and at last, the poloidal rotation velocity
of plasma was measured by means of poloidal
correlation reflectometry.
Analysis of obtained data allowed to make the
following conclusions:
-Spectra of density fluctuations observed at O-mode
reflection at adjacent (∇ r≤4 cm) plasma layers are
similar and have a rather high coherency (γ1, 2≈0,4-0,6).
-The estimates of plasma density fluctuation level
showed that these fluctuations are stronger at the outer
part of plasma column (Fig.5).
-The tendency of increase of radial wave numbers kr
of fluctuations with radius increase was observed
(Fig.5). It is interesting to note that observed maxima of
kr are located in the region of magnetic islands.
23
-10.00 -5.00 0.00 5.00 10.00
0.00
1.00
2.00
3.00
kr,cm-1 δn/n*10
r,cm
−δn/n
−kr
Fig.5.Radial distributions of radial wave numbers,
kr, and the plasma density fluctuation level,
n
nδ
-The high velocity shear is observed in the region of
localization of island chains (Fig.6).
-10.00 -5.00 0.00 5.00 10.00 15.00
-8.00
-4.00
0.00
4.00
8.00 v ,10
-5cm s-1
r,cm
υ
Fig. 6. The radial distribution of the poloidal
rotation velocity
-The sharp decrease of the radial electric field value
was observed in the layer between the chains of
magnetic islands (Fig.7).
4. Conclusion
The case of the presence of island chains of low
order resonant surfaces (t=1/4) in a magnetic
configuration with small shear with sufficient heating
power in the region of their localization was realized in
the presented experiment.
-15.00 -10.00 -5.00 0.00 5.00 10.00
-160.00
-120.00
-80.00
-40.00
0.00
40.00 Er,V/cm
r,cm
Fig. 7. The radial distribution of Er
Some pecuiarities in radial distributions of plasma
parameters were observed in this case in the region of
rational magnetic surfaces (high poloidal rotation
velocity shear, high radial electric field shear, increase
of kr, peculiarities on distribution Te(r)). It is reasonable
to suppose that all these peculiarities are connected with
stochastization of magnetic field lines near the island
chains and the increase of electron thermoconductivity
in these regions. All these effects can have very
important role in the formation of an interior transport
barrier.
Acknowledgements
This work was supported by Ukrainian Ministry
of Science and Education grant and LIME grant.
References
[1] G.G.Lesnyakov, E.D.Volkov, A.V.Georgievskij et
al. Study of the magnetic configuration of an l=3
torsatron by the triode and the luminescent rod methods.
Nuclear Fusion, 1992, v.32, N 12, pp.2157-2176.
[2] E.D.Volkov, A.V.Arsen’ev, I.Yu.Adamov et al.
Radial distribution of electron temperature in RF
discharge plasma in torsatron magnetic configuration
with island structure. Proc. of 23 rd EPS Conf.on
Control. Fusion and Plasma Phys. 1996, v. 20 C, part
II, pp.547-550.
[3] E.D.Volkov, I.Yu.Adamov , A.V.Arsen’ev et al.
Confinement of RF heated plasma in the Uragan-3M
torsatron. Plasma Phys. and Control. Nucl. Fusion Res.
IAEA, Vienna , 1993, v. 2, pp. 679-688.
Acknowledgements
References
|
| id | nasplib_isofts_kiev_ua-123456789-78501 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T17:10:13Z |
| publishDate | 2000 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Volkov, E.D. Adamov, I.Yu. Berezhnyj, V.L. Kulaga, A.E. Nazarov, N.I. Ocheretenko, V.L. Pinos, I.B. Shcherbinina, T.E. Skibenko, A.I. Slavnyj, A.S. Tarasov, I.K. Fomin, I.P. 2015-03-18T16:31:50Z 2015-03-18T16:31:50Z 2000 Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron / E.D. Volkov, I.Yu. Adamov, V.L. Berezhnyj, A.E. Kulaga, N.I. Nazarov, V.L. Ocheretenko, I.B. Pinos, T.E. Shcherbinina, A.I. Skibenko, A.S. Slavnyj, I.K. Tarasov, I.P. Fomin // Вопросы атомной науки и техники. — 2000. — № 6. — С. 21-23. — Бібліогр.: 3 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/78501 533.9 The results of local measurements of RF discharge plasma parameters (plasma density and its fluctuations, electron temperature and energy of superthermal electrons, plasma poloidal rotation velocity) in the Uragam-3M torsatron are presented. The obtained data are analyzed taking into account the peculiarities of the Uragan-3M magnetic configuration and scenario of RF plasma production and heating. Some suppositions about mechanisms of a radial electric field generation are discussed with the calculation of a magnetic configuration island structure. This work was supported by Ukrainian Ministry of Science and Education grant and LIME grant. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Magnetic confinement Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron Article published earlier |
| spellingShingle | Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron Volkov, E.D. Adamov, I.Yu. Berezhnyj, V.L. Kulaga, A.E. Nazarov, N.I. Ocheretenko, V.L. Pinos, I.B. Shcherbinina, T.E. Skibenko, A.I. Slavnyj, A.S. Tarasov, I.K. Fomin, I.P. Magnetic confinement |
| title | Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron |
| title_full | Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron |
| title_fullStr | Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron |
| title_full_unstemmed | Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron |
| title_short | Radial distributions of RF discharge plasma parameters and radial electric field in the Uragan-3M torsatron |
| title_sort | radial distributions of rf discharge plasma parameters and radial electric field in the uragan-3m torsatron |
| topic | Magnetic confinement |
| topic_facet | Magnetic confinement |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/78501 |
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