Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies
Studies of plasma edge Ha emission fluctuations firstly proposed for CHS heliotron/torsatron have been performed for RF produced/heated plasma in “Uragan-3M” torsatron. Approach is based on a realistic assumption that Ha emission fluctuations from plasma edge (ne≥10¹⁷m⁻³, Te≥10eV) defined mostly by...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
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| Цитувати: | Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies / V.G. Konovalov, K. Matsuoka, O.S. Pavlichenko, A.N. Shapoval, A.I. Skibenko, C. Suzuki // Вопросы атомной науки и техники. — 2002. — № 4. — С. 199-201. — Бібліогр.: 4 назв. — англ. |
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Konovalov, V.G. Matsuoka, K. Pavlichenko, O.S. Shapoval, A.N. Skibenko, A.I. Suzuki, C. 2015-04-14T17:28:14Z 2015-04-14T17:28:14Z 2002 Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies / V.G. Konovalov, K. Matsuoka, O.S. Pavlichenko, A.N. Shapoval, A.I. Skibenko, C. Suzuki // Вопросы атомной науки и техники. — 2002. — № 4. — С. 199-201. — Бібліогр.: 4 назв. — англ. 1562-6016 PACS: 52.70.-m; 52.55.Hc https://nasplib.isofts.kiev.ua/handle/123456789/80305 Studies of plasma edge Ha emission fluctuations firstly proposed for CHS heliotron/torsatron have been performed for RF produced/heated plasma in “Uragan-3M” torsatron. Approach is based on a realistic assumption that Ha emission fluctuations from plasma edge (ne≥10¹⁷m⁻³, Te≥10eV) defined mostly by electron density fluctuations. Having two Ha observation channels getting emission from plasma edge in 2 different poloidal locations of plasma one can study correlation of electron density fluctuations between these locations. Analysis of data included calculation of spectra of signals, their coherency and cross correlation between 2 signals for time windows 1 ms. Bands of rather high (>0.5) coherency were observed over the whole range (f<100 KHz) of frequencies. Calculation of cross correlation of digitally filtered (∆f=4 KHz) signals showed that time delay of low frequency part of signals coincides with time delay of no filtered signals and is decreasing with frequency increase. Conclusion of these observations is: time delay of low frequency part of signals reflects plasma poloidal rotation, time delay in the rest part of spectra reflects a dispersion properties of poloidally propagating density fluctuations. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Plasma diagnostics Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| title |
Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies |
| spellingShingle |
Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies Konovalov, V.G. Matsuoka, K. Pavlichenko, O.S. Shapoval, A.N. Skibenko, A.I. Suzuki, C. Plasma diagnostics |
| title_short |
Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies |
| title_full |
Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies |
| title_fullStr |
Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies |
| title_full_unstemmed |
Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies |
| title_sort |
observation of plasma poloidal rotation in “uragan-3m” torsatron from edge hα fluctuation correlation studies |
| author |
Konovalov, V.G. Matsuoka, K. Pavlichenko, O.S. Shapoval, A.N. Skibenko, A.I. Suzuki, C. |
| author_facet |
Konovalov, V.G. Matsuoka, K. Pavlichenko, O.S. Shapoval, A.N. Skibenko, A.I. Suzuki, C. |
| topic |
Plasma diagnostics |
| topic_facet |
Plasma diagnostics |
| publishDate |
2002 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| description |
Studies of plasma edge Ha emission fluctuations firstly proposed for CHS heliotron/torsatron have been performed for RF produced/heated plasma in “Uragan-3M” torsatron. Approach is based on a realistic assumption that Ha emission fluctuations from plasma edge (ne≥10¹⁷m⁻³, Te≥10eV) defined mostly by electron density fluctuations. Having two Ha observation channels getting emission from plasma edge in 2 different poloidal locations of plasma one can study correlation of electron density fluctuations between these locations. Analysis of data included calculation of spectra of signals, their coherency and cross correlation between 2 signals for time windows 1 ms. Bands of rather high (>0.5) coherency were observed over the whole range (f<100 KHz) of frequencies. Calculation of cross correlation of digitally filtered (∆f=4 KHz) signals showed that time delay of low frequency part of signals coincides with time delay of no filtered signals and is decreasing with frequency increase. Conclusion of these observations is: time delay of low frequency part of signals reflects plasma poloidal rotation, time delay in the rest part of spectra reflects a dispersion properties of poloidally propagating density fluctuations.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/80305 |
| citation_txt |
Observation of plasma poloidal rotation in “Uragan-3M” torsatron from edge Hα fluctuation correlation studies / V.G. Konovalov, K. Matsuoka, O.S. Pavlichenko, A.N. Shapoval, A.I. Skibenko, C. Suzuki // Вопросы атомной науки и техники. — 2002. — № 4. — С. 199-201. — Бібліогр.: 4 назв. — англ. |
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2025-11-25T21:12:26Z |
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| fulltext |
OBSERVATION OF PLASMA POLOIDAL ROTATION
IN “URAGAN-3M” TORSATRON
FROM EDGE Hα FLUCTUATION CORRELATION STUDIES
V.G.Konovalov1, K.Matsuoka2, O.S.Pavlichenko1, A.N.Shapoval1, A.I.Skibenko1, C.Suzuki2
1Institute of Plasma Physics, NSC KhIPT, Kharkov, Ukraine
2 National Institute for Fusion Studies, Toki, Japan
Studies of plasma edge Hα emission fluctuations firstly proposed for CHS heliotron/torsatron have been performed
for RF produced/heated plasma in “Uragan-3M” torsatron. Approach is based on a realistic assumption that Hα emission
fluctuations from plasma edge (ne≥1017m-3, Te≥10eV) defined mostly by electron density fluctuations. Having two Hα
observation channels getting emission from plasma edge in 2 different poloidal locations of plasma one can study
correlation of electron density fluctuations between these locations. Analysis of data included calculation of spectra of
signals, their coherency and cross correlation between 2 signals for time windows 1 ms. Bands of rather high (>0.5)
coherency were observed over the whole range (f<100 KHz) of frequencies. Calculation of cross correlation of digitally
filtered (∆f=4 KHz) signals showed that time delay of low frequency part of signals coincides with time delay of no
filtered signals and is decreasing with frequency increase. Conclusion of these observations is: time delay of low
frequency part of signals reflects plasma poloidal rotation, time delay in the rest part of spectra reflects a dispersion
properties of poloidally propagating density fluctuations.
PACS: 52.70.-m; 52.55.Hc
INTRODUCTION
Poloidal plasma rotation induced by ExB drift is
one of most popular topics of toroidal magnetic plasma
confinement experiments. Most direct way of poloidal
rotation observation is a measurement of Doppler shift of
spectral lines of impurity ions emitted at corresponding
direction [1]. The spatial resolution of measurements is
provided by using atom beams (diagnostic or heating
ones) crossing a plasma column. In this case the velocity
of charge exchanged impurity ions is being measured and
gives information about poloidal rotation of these ions.
This velocity is not necessarily coincide with velocity of
main (hydrogen) plasma ions.
Recently microwave reflectometry became
popular for poloidal plasma rotation observation [2,3].
Microwave reflectometry poloidal rotation methods are
based on observation on microwaves reflected by plasma
cut-off layers perturbed by plasma fluctuations. Such
layers act like as diffraction grating that is moving across
the observation line and producing of reflected
microwave modulation. Information about this movement
can be inferred from observation of Doppler shifted
spectrum of reflected microwaves at oblique reflection [2]
or from crosscorelation of microwares reflected from two
different poloidal locations [3]. In this approach the
observed frequency shift or time delay are results of
propagation of electron density perturbations and reflects
both fluctuation poloidal propagation and plasma column
rotation (if it exists).
In this work we tried to observe the propagation
of electron density perturbations at plasma edge from
observation Hα plasma emission. This approach is based
on a fact that the Hα line intensity in a plasma with the
electron temperature ≥ 5-10 eV depends on hydrogen
atom and electron density only. In fluctuating plasma Hα
light fluctuations are result of electron density
fluctuations mostly thus giving a possibility to study ne
fluctuations.
EXPERIMENT
Experiments were performed during RF plasma
production/heating on torsatron “Uragan-3M” (U-3M)
[4]. Fig.1 shows a crossection of l=3 helical winding (3-
rd pole is not shown) and magnetic surfaces for standard
U-3M magnetic field configuration. Hα light emission was
observed through a window by means of simple 2 channel
lens+ Hα filter + photomultiplier (PMT) system. Each
system could scan the whole plasma crossection. Signals
from PMT were digitized (sampling rate up to 1.5 M 12b
words/s), stored and analyzed.
Fig.1 Schematic view of experiment (1.2- observation
lines).
Typical Hα signal for experiment (B=0,7 T, PRF ≤ 200
KW) is shown on Fig.2 together with signal of 2 mm
interferometer. Shot-to-shot scanning of observation line
(for both channels) (Fig.3) allowed choosing positions of
channels for observation of light from opposite lobes of
magnetic surfaces.
Analysis of fluctuations included calculation of
power spectrum of Hα signals, cross-correlation C12(τ) and
coherence function C12(ω) of 1024 data points cut out of
signals (sampling rate – 1 Mw/s).
Problems of Atomic Science and Technology. 2002. № 4. Series: Plasma Physics (7). P. 199-201 199
Fig.2 Typical signals of Hα and 2 mm interferometer
(sampling rate- 200 Kw/s)
Fig.3 Contour plot of side-on observation of
Hα emission.
0 0 . 0 1 0 . 0 2 0 . 0 3 0 . 0 4 0 . 0 5 0 . 0 6 0 . 0 7 0 . 0 8
- 1 0 0
0
1 0 0
2 0 0
3 0 0
4 0 0
S h o t # 3 6 1 1
t , c
0 0 . 0 1 0 . 0 2 0 . 0 3 0 . 0 4 0 . 0 5 0 . 0 6 0 . 0 7 0 . 0 8
0
1 0 0
2 0 0
3 0 0
4 0 0
t , c
C h a n n e l 1
C h a n n e l 2
Fig.4 Hα signals for both channels (sampling rate – 1
Mw/s).
Fig.5 Spectra of signals of both channels.
Typical spectra of Hα light fluctuations are
shown (in log scale) on Fig.5. These spectra are
characterized by slow decrement in frequency domain and
do not depend on time during 20-50 ms. Cross-correlation
between signals for the same time window is shown on
Fig.6.
Fig.6 Cross-correlation between signals.
The most striking feature of cross-correlation between Hα
signals from different poloidal locations – maximum at
zero lag time. This means that other then poloidal
propagation manifests itself in observed fluctuations
(possibly ballooning mode). Poloidal propagation of
density perturbations can be responsible for other maxima
of C12(τ).
To get more information about poloidal
propagation of perturbations we used another approach –
filtering of rather narrow frequency bands (δf=2-3 KHz)
of signal and calculation of time lag between these
filtered signals. At this approach we used the numerical
double filtering procedure that eliminates the phase delay
produced by signal filtering. Typical cross-correlation for
filtered signals is shown on Fig.7.
Fig.7 Cross-correlation for non-filtered (a) and filtered
(f=15 KHz) signals.
Fig.8 Power spectrum, coherency function and time lag
spectrum of Hα light fluctuations for t=20ms
Results of calculations of time lag for filtered signals
depending on filter frequency )(12 fτ together with
power spectrum and coherency function are shown on
Fig.8.
200
Analysis of data for different shots and time
intervals for given shot allowed us to distinguish 3
frequency bands: 1) low frequency (12-25 KHz) band
with almost constant delay time (δτ=-120 mks); 2)
intermediate frequency (25-50 KHz) band with changing
delay time and 3) high frequency (52-60 KHz) band with
small delay time (δτ=20 mks). As for as the delay time in
the band 1) roughly coincide with one of maximums in
cross-correlation for unfiltered signal, we suggest that
poloidal plasma rotation is responsible for this delay time.
In its turn small delay time in band 3) might reflect
existence of zero lag time maximum in cross-correlation
for unfiltered signal and thus corresponds to ballooning
mode of perturbations. We also suggested that band 2)
with changing delay time reflects an existence of
perturbations propagating in poloidal direction. Data for
delay time in this band were used for calculation of
velocity of propagation v and “dispersion relation” for
this frequency band
vk ⋅=ω
Fig.9 illustrates results of these calculations (points). For
poloidal modes one can suggest that
a
mk = (1)
where m – mode number (1,2,..) and a – plasma layer
radius (a ≈ 12 cm). Horizontal lines on Fig.9 shows k-
values calculated from eq. (1). One can notice that mode
frequencies (intersections points of dotted line and
horizontal bars) roughly coincide with spectrum and
coherence function maximums in band 2).
Fig.9 KKθθ spectrum for f=27-45 KHz. spectrum for f=27-45 KHz.
CONCLUSION
Studies of properties of fluctuations of Hα light
emitted from edge plasma in U-3M torsatron showed
rather complicated picture that did not allow
distinguishing effects of possible poloidal plasma rotation
from data of cross-correlation analysis. We introduced a
new function – time lag spectrum )(12 fτ and calculated
it by using digital filtering of Hα signals. This function
appeared to give information about different modes of
perturbations - poloidally propagating and ballooning
modes and poloidal plasma rotation. Such approach can
be used for fluctuations observed by any diagnostic if it
has a good spatial and time resolution and has at least 2
space separated observation channels.
Poloidal rotation velocity value inferred from
time delay of low-frequency part of Hα fluctuation
spectrum ( 3≈polv km/s) well agreed with data
obtained for U-3M torsatron via poloidal correlation
microwave reflectometry [4].
The main disadvantage of Hα light usage – the
lack of good spatial distribution – can be overcame by
BES (by using diagnostic or heating neutral beam).
Similar setup for Hα observation is under
preparation for the CHS Heliotron/torsatron now.
REFERENCES
[1] G.R.McKee, M.Murakami et al, Plasma Physics, 7
(2000) 1870
[2] V.V. Bulanin, S.V. Lebedev et al, Plasma Physics
Reports, 26 (2000) 823
[3] A.I. Skibenko, V.L. Ocheretenko et al Ukrainian
Journ. of Phys., 46 (2001),443.
[4] A.I. Skibenko, O.S. Pavlichenko et al, ITB formation
dynamics in the U-3M torsatron inferred from microwave
reflectometry, Internat. Conference and School on Plasma
Physics and Controlled Fusion (Alushta) (2002), book of
abstracts, p. 52.
201
Introduction
Experiment
Conclusion
References
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