ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2002 |
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| Мова: | Англійська |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
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| Цитувати: | ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry / A.I. Skibenko, O.S. Pavlichenko, E.D. Volkov, I.P. Fomin, V.L. Berezhniy, V.L. Ocheretenko, I.B. Pinos, Yu.Ya. Podoba, N.I. Nazarov, S.A. Tsybenko, A.P. Litvinov // Вопросы атомной науки и техники. — 2002. — № 4. — С. 62-64. — Бібліогр.: 6 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859742961072340992 |
|---|---|
| author | Skibenko, A.I. Pavlichenko, O.S. Volkov, E.D. Fomin, I.P. Berezhniy, V.L. Ocheretenko, V.L. Pinos, I.B. Podoba, Yu.Ya. Nazarov, N.I. Tsybenko, S.A. Litvinov, A.P. |
| author_facet | Skibenko, A.I. Pavlichenko, O.S. Volkov, E.D. Fomin, I.P. Berezhniy, V.L. Ocheretenko, V.L. Pinos, I.B. Podoba, Yu.Ya. Nazarov, N.I. Tsybenko, S.A. Litvinov, A.P. |
| citation_txt | ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry / A.I. Skibenko, O.S. Pavlichenko, E.D. Volkov, I.P. Fomin, V.L. Berezhniy, V.L. Ocheretenko, I.B. Pinos, Yu.Ya. Podoba, N.I. Nazarov, S.A. Tsybenko, A.P. Litvinov // Вопросы атомной науки и техники. — 2002. — № 4. — С. 62-64. — Бібліогр.: 6 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| first_indexed | 2025-12-01T19:28:52Z |
| format | Article |
| fulltext |
ITB FORMATION DINAMICS IN THE URAGAN-3M TORSATRON
INFERRED FROM MICROWAVE REFLECTOMETRY
A.I. Skibenko, O.S. Pavlichenko, E.D. Volkov, I.P. Fomin, V.L. Berezhniy, V.L. Ocheretenko,
I.B. Pinos, Yu.Ya. Podoba, N.I. Nazarov, S.A. Tsybenko, A.P. Litvinov
Institute of Plasma Physics of NSC KhIPT, 61108, Kharkov, Ukraine
PACS: 52.55.Hc; 52.70.Gw
Phenomena of internal transport barrier (ITB)
formation have been observed in tokamaks and
stellarators for different types of configurations
(limiter/divertor) and heating scenarios (OH+ECH, NBI)
[1, 2].
In the Uragan-3M torsatron the ITB formation was
recently observed during plasma production/heating by
RF power absorption [3]. Experiments on RF plasma
production were performed at magnetic field B0 =0.7 T
and for centered magnetic configuration. Frame type
antenna was powered on frequency f~8.8 MHz (P= 200
KW) corresponding to excitation of ion cyclotron waves.
a
Fig.1
a: Magnetic surfaces and magnetic islands chains in the
standard configuration of Uragan-3M torsatron.
b: Setup of microwave diagnostics in the Uragan-3M
torsatron. 1-7 – reflectometer, 8 – interferometer λ=2mm,
9 – Fabri-Perot resonator, 10,11 – RF antennas K1 and
K2.
In these experiments magnetic configuration of l=3
torsatron with open helical divertor Uragan-3M is
characterized by the outward shift (≈ 5cm) of magnetic
axis and existence of magnetic islands chains near the
rational (ι=1/4 and 1/5) surfaces (Fig.1a).
Transition to improved confinement (characterized by
increase of plasma energy measured by saddle-type ψ-
loop, electron (ECE) and ion (NPA) temperature and
electron density (interferometer λ=2mm)) was observed at
comparatively low density ( en =1.1012 cm-3) and above
certain RF power [3].
Fig.2 Plasma density evolution in regimes with ITB
formation.
This work was aimed to study of transition to ITB
dynamics namely plasma density and poloidal rotation
velocity profiles in the vicinity of island chain and density
fluctuations prior and during onset of new plasma state.
This information was obtained from the
multifrequency microwave reflectometry: conventional –
for electron density profile and density fluctuation
(frequency and wave number spectra) measurements and
correlation (radial, poloidal and toroidal) – for plasma
rotation (poloidal and toroidal) velocity studies. U-3M
microwave reflectometry setup and methods were
described earlier [4]. For toroidal plasma rotation
observation we put 2 microwave antennas in other,
toroidally displaced locations. We also used data of single
channel 2 mm interferometer – for line-averaged electron
density measurements and 8 mm Fabri-Perot resonator –
for diverted plasma density measurements (Fig.1b.).
For radial profile studies of rather low density plasma
(ne(0)= 2.1012 cm-3) O-mode 10 GHz and lower X-mode
20÷30 GHz probing were used. At magnetic field of 0.7 T
this allowed to observe X-mode microwave reflection
from plasma layers with electron density in the range
0.1÷3.8 1012 cm-3.
The radial position of reflecting layer rref was
determined from relation:
rref = rc +rs
here rc is the distance of reflecting layer from magnetic
axis defined from relations:
m
cc
a
r
mn
n
−=
+
1
)1(
; )1(
f
f
nn ce
crc −= ;
where
n
nnm c −
= for maximal frequency that was
reflected.
62 Problems of Atomic Science and Technology. 2002. № 4. Series: Plasma Physics (7). P. 62-64
Fig.3. Time behavior of signals of 2 mm interferometer
and reflectometers at different probing frequencies of X-
waves (1- f=26 GHz ne=2.1·1012 cm-3, 2- f=25 GHz
ne=1.65·1012 cm-3, 3- f=23 GHz ne=1·1012 cm-3, 4- f=21
GHz ne=0.36·1012 cm-3).
Value of rs was determined from a reflected wave
phase shift. X-mode reflecting layer position error was
estimated according to [5] and is in the range of 1.3÷0.4
cm for f in the range of 21÷26 GHz.
The onset of transition to ITB was manifested in a
rapid change of reflected X-mode amplitude and phase
(Fig.3) that corresponded to the density profile widening
[6]. A 30% increase of line-averaged plasma density was
observed also (Fig. 2, Fig.3-upper).
Fig.4. Reflecting layer position time evolution (1-
ne=2,1·1012cm-3;2-1,3 ·1012cm-3; 3 -0,6·1012cm-3;4-
0,36·1012cm-3)
Density profile studies showed a slow evolution of
reflected layer radius (Fig.4) corresponding to widening
of density profile with a small decrease of the central
density (Fig.5).
0
1
2
-15 -10 -5 0 5 10
n
e (10 12 cm -3 )
r, cm
2
1
Fig.5. The radial profiles of electron density prior to (1)
and during of (2) ITB period.
The most striking effect of transition was observed in
the radial profile of poloidal rotation velocity (Fig.6).
Fig. 6. Radial profiles of poloidal rotation velocity 1-
prior, 2-during, 3-after period of transition into ITB
regime.
Prior to (1) and after of (3) the transition period an
inner plasma half-radius rotates in the direction
corresponding to the “electron root”; at outer half-radius
direction of rotation corresponds to the “ion root”. During
the transition phase (2) the poloidal rotation velocity at
inner half-radius is larger by a factor of 2 than before and
after transition phase. Large velocity shear was always
observed at ≥ar / 0.8. In contrast to poloidal rotation
the toroidal rotation velocity didn’t show a noticeable
radial shear (Fig.7).
-6
-4
-2
0
2
4
6
8
20 25 30 35 40
1
2
3
t, ms
V
tor
km/s
Fig.7 The time evolution of toroidal rotation of plasma
layers with different density (1-2·1012cm3,2-1,3·1012 cm-3,
3-0,65·1012 cm-3).
Taking into account-measured values of poloidal and
toroidal velocities and poloidal and toroidal magnetic
fields (Bt=0.7T, Bθ~0.15-0.2T) the ratio of the electric
field components connected with plasma rotation is
1.0≈
φθ
θφ
BV
BV
during the ITB.
Fig.8. Spectra of reflectometer signal fluctuations (1-
before transition, 2-during transition, 3 – after transition)
During transition phase spectrum of reflected signals
transformed: in one with strong suppression of the part in
the range of 20-40KHz (Fig. 8).
Spectrum averaged amplitude of density fluctuations
nn~ also slightly decreased (Fig.9).
Fig. 9. Density fluctuation level evolution during the
transition in ITB regime (ne~1012 cm-3, rint~9 cm, rext~5
cm).
Measurements of density ratio in divertor and in trap
confirm the improvement of particles confinement during
the ITB regime (Fig. 10).
Shot number
Fig.10 Ratios of integral plasma density in divertor and
in trap before (left bars) and during (right bars) of ITB.
Analysis of reflectometry data showed that the
phenomenon of ITB formation is marginal: it appears
spontaneously for rather low density and high electron
temperature plasma.
However the strong change of poloidal rotation
velocity profile and fluctuation spectrum allows to think
that plasma transits in another state. The lower plasma
density and larger RF power results in longer period of
this state existence (∆t= 3-7 ms). More data are necessary
for better understanding of this phenomenon. The study of
it will be the topic of future studies.
REFERENCES
1. Hidalgo C., Petrosa M.A., Ernts K. et al, Plasma
Fusion Res. Series, 4 (2001) 167
2. N.B. Marushchenko Optimum Confinement at W7-
AS. Problems of Atomic Science and Technology
2000. #3 plasma physics (5) p8-12.
3. E.D. Volkov, V.L. Berezhniy et al “Formation of ITB
in vicinity of rational surfaces in the Uragan-3M
torsatron” (this conference)
4. A.I. Skibenko, V.L. Ocheretenko et al Ukrainian
Journal. of Phys. v. 46 (2001),443.
5. A.I. Skibenko, O.S. Pavlichenko et al, Plasma
Physics, V.20 #1, 1994, 13
6. A.I. Skibenko, V.L. Berezhniy, V.L. Ocheretenko, et
all, Third Int. Kharkov Symposium “Physics and
engineering of millimeter and submillimeter Waves”
Vol. 2 Kharkov Ukraine September 15-17, 1998.
|
| id | nasplib_isofts_kiev_ua-123456789-80250 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-01T19:28:52Z |
| publishDate | 2002 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Skibenko, A.I. Pavlichenko, O.S. Volkov, E.D. Fomin, I.P. Berezhniy, V.L. Ocheretenko, V.L. Pinos, I.B. Podoba, Yu.Ya. Nazarov, N.I. Tsybenko, S.A. Litvinov, A.P. 2015-04-14T05:12:31Z 2015-04-14T05:12:31Z 2002 ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry / A.I. Skibenko, O.S. Pavlichenko, E.D. Volkov, I.P. Fomin, V.L. Berezhniy, V.L. Ocheretenko, I.B. Pinos, Yu.Ya. Podoba, N.I. Nazarov, S.A. Tsybenko, A.P. Litvinov // Вопросы атомной науки и техники. — 2002. — № 4. — С. 62-64. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 52.55.Hc; 52.70.Gw https://nasplib.isofts.kiev.ua/handle/123456789/80250 en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Magnetic confinement ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry Article published earlier |
| spellingShingle | ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry Skibenko, A.I. Pavlichenko, O.S. Volkov, E.D. Fomin, I.P. Berezhniy, V.L. Ocheretenko, V.L. Pinos, I.B. Podoba, Yu.Ya. Nazarov, N.I. Tsybenko, S.A. Litvinov, A.P. Magnetic confinement |
| title | ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry |
| title_full | ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry |
| title_fullStr | ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry |
| title_full_unstemmed | ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry |
| title_short | ITB formation dinamics in the Uragan-3M torsatron inferred from microwave reflectometry |
| title_sort | itb formation dinamics in the uragan-3m torsatron inferred from microwave reflectometry |
| topic | Magnetic confinement |
| topic_facet | Magnetic confinement |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/80250 |
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