Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron
Curentless plasma in Uragan-3M (U-3M) is produced and heated by absorption of RF power in the region of Alfven waves (AW) [1]. The process of plasma heating was explained in [2] as a result of Cherenkov absorption of energy of the fast (EM) and slow (kinetic Alfven) waves by electrons and turbul...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2006 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2006
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| Цитувати: | Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron / A.I. Skibenko, O.S. Pavlichenko, V.L. Berezhnyj, P.Ya. Burchenko, A.E. Kulaga, V.L. Ocheretenko, I.B. Pinos, A.V. Prokopenko, A.S. Slavnyj, I.K. Tarasov, O.Yu. Volkova // Вопросы атомной науки и техники. — 2006. — № 6. — С. 65-67. — Бібліогр.: 7 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859730587612348416 |
|---|---|
| author | Skibenko, A.I. Pavlichenko, O.S. Berezhnyj, V.L. Burchenko, P.Ya. Kulaga, A.E. Ocheretenko, V.L. Pinos, I.B. Prokopenko, A.V. Slavnyj, A.S. Tarasov, I.K. Volkova, O.Yu. |
| author_facet | Skibenko, A.I. Pavlichenko, O.S. Berezhnyj, V.L. Burchenko, P.Ya. Kulaga, A.E. Ocheretenko, V.L. Pinos, I.B. Prokopenko, A.V. Slavnyj, A.S. Tarasov, I.K. Volkova, O.Yu. |
| citation_txt | Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron / A.I. Skibenko, O.S. Pavlichenko, V.L. Berezhnyj, P.Ya. Burchenko, A.E. Kulaga, V.L. Ocheretenko, I.B. Pinos, A.V. Prokopenko, A.S. Slavnyj, I.K. Tarasov, O.Yu. Volkova // Вопросы атомной науки и техники. — 2006. — № 6. — С. 65-67. — Бібліогр.: 7 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | Curentless plasma in Uragan-3M (U-3M) is produced and heated by absorption of RF power in the region of Alfven
waves (AW) [1]. The process of plasma heating was explained in [2] as a result of Cherenkov absorption of energy of
the fast (EM) and slow (kinetic Alfven) waves by electrons and turbulent ion heating due to excitation of short wave ion
Bernstein waves (IBW). In this report we present results of studies of plasma density fluctuations showing existence of
a narrow bands near the frequencies of ω ≈ nωci (n = 1, 2, 3).
|
| first_indexed | 2025-12-01T13:51:06Z |
| format | Article |
| fulltext |
Problems of Atomic Science and Technology. 2006, 6. Series: Plasma Physics (12), p. 65-67 65
EXCITATION OF PLASMA FLUCTUATIONS NEAR ION
GIROFREQUENCIES DURING RF PLASMA HEATING
IN URAGAN-3M TORSATRON
A.I. Skibenko, O.S. Pavlichenko, V.L. Berezhnyj, P.Ya. Burchenko, A.E. Kulaga,
V.L. Ocheretenko, I.B. Pinos, A.V. Prokopenko, A.S. Slavnyj, I.K. Tarasov, O.Yu. Volkova
Institute of Plasma Physics, NSC “Kharkov Institute of Physics and Technology”,
61108, Akademicheskaya Str. 1, Kharkov, Ukraine
Curentless plasma in Uragan-3M (U-3M) is produced and heated by absorption of RF power in the region of Alfven
waves (AW) [1]. The process of plasma heating was explained in [2] as a result of Cherenkov absorption of energy of
the fast (EM) and slow (kinetic Alfven) waves by electrons and turbulent ion heating due to excitation of short wave ion
Bernstein waves (IBW). In this report we present results of studies of plasma density fluctuations showing existence of
a narrow bands near the frequencies of n ci (n = 1, 2, 3).
PACS: 52.55.Hc
1. INTRODUCTION
In U-3M torsatron curentless plasma is produced and
heated by absorption of power from Alfven
( 8.07.0 ciωω ⋅÷≈ ) waves excited in plasma by RF
antennae. Two different frame type antennas allowing gas
breakdown, plasma build-up and heating has been used in
recent years. Both electron and ion heating for
experiment condition were observed (PRF 200 kW,
Te(0) 500 eV, Ti 350 eV, ne(0) 2⋅1018 m-3).
The qualitative explanation of both electron and ion
heating of plasma by AW RF power absorption in U-3m
has been given in paper [2]. In this work the excitation
of both the fast (electromagnetic) and slow (kinetic
Alfven) waves and the effects of their mutual
conversion have been studied numerically. The
linear mechanisms of the electron Cherenkov and ion
cyclotron absorption have been taken into account.
The ion cyclotron absorption of RF power was
negligible.
The calculations have shown the amplitudes of
excited waves to be high enough so the relative
velocity of electrons and ions ie vvu
rr
−= becomes
comparable with the ion thermal velocity
iTV . In this
case the short wavelength ion Bernstein waves can be
excited )3~/~( uVk
ii TLρ with the frequencies
cink ωω ≈)( and growth rates
iTci Vu /~ ωγ ,
iLρ is the
ion Larmor radius [3].
At the nonlinear stage the saturation of these
instabilities occurs due to the nonlinear broadening
of cyclotron resonance because of the random walk
of ions in the field of unstable IBW’s at the level
4)/(~/
iTe VunTw , (Te > Ti). The scattering of ions on
turbulent fluctuations increases their "transverse"
temperature [4].
This work was devoted to search of manifestation of
ion Bernstein waves predicted in [2] with cink ωω ≈)(
and 3~
iLkρ . Such waves with n = 1,2,3 and 31−≈
iLkρ
manifested as plasma density fluctuations have been
observed by backscattering of microwaves.
2. EXPERIMENT
Experiments were performed on U-3M device. U-3M
device is a l= 3, m = 9 torsatron with open helical divertor
[1,5]. Main parameters of plasma are R = 1 m, a = 0.13 m,
rotational transform /2 (a) = 0.4. In this experiment
magnetic field was B0 = (0.65…0.72)T. Plasma in U-3M
is produced by absorption of RF power (f = 8…8,8 MHz,
PRF 200 KW) from 2 antennas put inside of helical
winding near the last closed magnetic surface. Frame type
antennas are used to excite RF waves in plasma.
Typical parameters were measured during RF
impulse: central chord averaged electron density by 2 mm
interferometer, radial density profile by UHF
reflectometry (n(r) = (0.3…3)⋅1012 cm-3), radial electron
temperature profile by ECE (Te(r) = 40…600 eV),
perpendicular ion energy distribution was determined by
CX neutral mass-energy analyser and cosists of two
temperature groups Ti1 ≈ 50 eV and Ti2 = 250÷400 eV.
Backscattering of microwaves was observed in one
crossection (D-D) of device where 3 horn antennas were
installed (Fig.1) [6]. Antenna 1 was used for X-wave
outward (F = 19…21 GHz) and antenna 3 – for O-wave
inward (F = 10…12 GHz) probing and backscattered
microwave observation. For experiment condition
( 318
max 104)( −⋅≤ mrne ) used microwaves allowed to
observe reflection from almost all outer and inner plasma
radius. The superheterodyne receiver with saw-tooth
Fig.1. Schematic view of RF and microwave antennas
location on U-3M torsatron
modulation of frequency ( 600 ÷=∆F MHz, modulation
frequency – 250 Hz) was used for direct observation of
spectrum of backscattered microwave signals. Typical
trace fragments of spectroanalyser output are shown on
a b
D-D
66
Fig.2 (outward probing at X-wave) and on Fig.3 (inward
O-wave probing). On figures frequency marks
(∆f = 10 MHz), probing frequency and IBW maxima are
labeled by circles, squares and arrows respectively.
Fig.2. Signals of spectroanalyser; expanded traces –
during RF pulse (upper) and after RF pulse (lower).
Frequency marks ( f = 10 MHz) are labeled by circles
Two clear maxima with the frequency difference of ~
9 MHz are observed at outward probing (F = 19 GHz).
At inward O-wave probing (F = 11.5 GHz) 3 maxima
with smaller amplitude has been observed (Fig.3).
Fig.3
Comparison of measured frequencies of observed
maxima in spectra with ion cyclotron frequency at cut-off
layer was produced as follows. A cut-off layer position
for a probing frequency was calculated from phase shift
measurements (Fig.4).
106
107
108
109
110
111
8
8.4
8.8
9.2
9.6
10
10 20 30 40 50 60
R
cu
t-o
ff ,
cm f, M
H
z
t, ms
Fig.4
Time behavior of first maximum of spectra for a
discharge where cut-off layer position was measured is
shown on Fig.4.
A predicted value of ion cyclotron frequency was
obtained from data of vacuum magnetic field calculation
(Fig.5).
The calculated value for ion cyclotron frequency for
cut-off layer position Rcut-off = 107 cm is fci 9.8 MHz and
is near to value of frequency of first maximum shown on
Fig.4. Similar calculations for other shots showed that
frequency of observed maxima divided by harmonic
number coincide with calculated values of ion cyclotron
(IC) frequency within of 10-15% (Fig.5).
Time behavior of IC harmonic amplitudes is shown
for outward and inward parts of plasma column (Fig.6-7).
They observed during whole plasma discharge duration
but their time behavior was different.
8
9
10
11
12
13
85 90 95 100 105 110 115 120
F C
I ,
M
H
z
R, cm
Fig.5. The ion cyclotron frequency along torsatron radius
solid line was calculated from B(R), the points are result
of back-scattered UHF signal analysis
Fig. 6
Fig.7
But these data were obtained for one regime of device
operation and thus are preliminary.
Besides of spectrum of observed fluctuations we
estimated the “radial” component of fluctuation wave
vector fk
r
value. The simplest estimate of fk
r
comes
from
fincidref kkk
rr
+= ,
67
where refk
r
and incidk
r
are k vectors of reflected and
incident microwaves. For microwave backscattering the
fluctuation wave vector modulus is
incidf kk 2= .
More accurate estimate of fk
r
given in [7] is
incidfincid kkLk ⋅<<⋅⋅ − 226.1 3/13/2 , (1)
where
n
nL
∇
= , n – plasma density. At the experiment
conditions (n0max = 4⋅1018 m-3) a range of kincid was
3.5…6 cm-1 and 2…4 cm-1 for outward and inward
probing correspondingly. Thus the range of fk
r
coming
from (1) is 3 cm-1 < fk
r
< 12 cm-1 and range of
iLfk ρ is
0.5 <
iLfk ρ < 3 (for Ti = 250 eV). It is necessary to notice
that upper limit for observed fk
r
was determined by
plasma density/cut-off probing frequency range in
experiment.
It is worth to notice that we did not observe
fluctuations with frequencies related to excited RF waves
in spite of we observed the difference frequency of RF
oscillators in the case when 2 RF antennas were powered
[6]. RF waves were excited by antennas with much lower
wave numbers (k 0.2 cm-1) and could not manifest at
microwave backscattering.
3. CONCLUSIONS
All experimental data on studies of high frequency
plasma density fluctuations for U-3M device confirmed
theory predictions of possible excitation of short
wavelength ion Bernstein waves with the frequencies
n ci and 3~
iLkρ . This conclusion is important for
understanding of physics of ion heating at excitation of
Alfven waves in U-3M plasma.
Theory predicts [4] that at the nonlinear stage the
saturation of IBW occur due to the nonlinear broadening
of cyclotron resonance because of the random walk of
ions in the field of unstable IBW. The scattering of ions
on turbulent fluctuations increases their "transverse"
temperature. Experimental observation of IBW gives a
tool for study of predicted link between IBW amplitude
and ion temperature as well.
The ion cyclotron harmonics observation by
microwave backscattering has diagnostic implications for
U-3M. Measurement of ion cyclotron harmonic frequency
Fci for different values of probing frequency (cut-off
frequency Fcut-off ) allows to map Fci over Fcut-off and get a
radial profile of electron density. We will use this
approach in future experiments.
REFERENCES
1. V.V. Bakaev, V.V. Bronnikov, V.S. Voitsenya et al.//
VIII Intern. Conf. on Controlled Fusion Research.
London, 1984, v.2, p. 397.
2. N.T. Besedin, S.V. Kasilov, I.M. Pankratov,
A.I. Pyatak and K.N. Stepanov // X Intern.
Workshop on stellarators. Garhing, 1993, collection
of papers, p. 277.
3. A.B. Kitsenko, V.I. Panchenko, K.N. Stepanov // Zh.
Techn. Fiz.. 1973, v. 43, p. 1437 (in Russian).
4. V.S. Michailenko, K.N. Stepanov: Preprint KFTI 83-
29, Kharkov, 1983; Zh. Exp. Teor. Phyz. 1984, v. 87,
p. 161 (in Russian).
5. E.D. Volkov, V.L. Berezhnyj et al. // Czechoslovak
Journ. of Physics. 2003, v. 53, p. 887.
6. O.S. Pavlichenko, A.I. Skibenko, E.D. Volkov,
V.L. Berezhnyj et al. // Problems of Atomic Science
and Technology. Series "Plasma Physics"(11). 2005,
2, p. 17-19.
7. C.Fanack, I.Boucher, F.Clairet et al. // Plasma Phys.
Control Fusion. 1996, v. 38, p. 1915.
-3M
. , . , . , . , A. . , . , . ,
. , . , . , .
-3M
[1]. [2]
) ( )
.
, n ci (n = 1, 2, 3).
-3M
. , . , . , . , A. . , . , . ,
. , . , . , .
-3M
[1]. [2]
) ( )
.
, n ci (n = 1, 2, 3).
|
| id | nasplib_isofts_kiev_ua-123456789-81783 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-01T13:51:06Z |
| publishDate | 2006 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Skibenko, A.I. Pavlichenko, O.S. Berezhnyj, V.L. Burchenko, P.Ya. Kulaga, A.E. Ocheretenko, V.L. Pinos, I.B. Prokopenko, A.V. Slavnyj, A.S. Tarasov, I.K. Volkova, O.Yu. 2015-05-20T16:01:45Z 2015-05-20T16:01:45Z 2006 Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron / A.I. Skibenko, O.S. Pavlichenko, V.L. Berezhnyj, P.Ya. Burchenko, A.E. Kulaga, V.L. Ocheretenko, I.B. Pinos, A.V. Prokopenko, A.S. Slavnyj, I.K. Tarasov, O.Yu. Volkova // Вопросы атомной науки и техники. — 2006. — № 6. — С. 65-67. — Бібліогр.: 7 назв. — англ. 1562-6016 PACS: 52.55.Hc https://nasplib.isofts.kiev.ua/handle/123456789/81783 Curentless plasma in Uragan-3M (U-3M) is produced and heated by absorption of RF power in the region of Alfven waves (AW) [1]. The process of plasma heating was explained in [2] as a result of Cherenkov absorption of energy of the fast (EM) and slow (kinetic Alfven) waves by electrons and turbulent ion heating due to excitation of short wave ion Bernstein waves (IBW). In this report we present results of studies of plasma density fluctuations showing existence of a narrow bands near the frequencies of ω ≈ nωci (n = 1, 2, 3). en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Magnetic confinement Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron Article published earlier |
| spellingShingle | Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron Skibenko, A.I. Pavlichenko, O.S. Berezhnyj, V.L. Burchenko, P.Ya. Kulaga, A.E. Ocheretenko, V.L. Pinos, I.B. Prokopenko, A.V. Slavnyj, A.S. Tarasov, I.K. Volkova, O.Yu. Magnetic confinement |
| title | Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron |
| title_full | Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron |
| title_fullStr | Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron |
| title_full_unstemmed | Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron |
| title_short | Excitation of plasma fluctuations near ion girofrequencies during RF plasma heating in Uragan-3M torsatron |
| title_sort | excitation of plasma fluctuations near ion girofrequencies during rf plasma heating in uragan-3m torsatron |
| topic | Magnetic confinement |
| topic_facet | Magnetic confinement |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/81783 |
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