Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect
Observations of enhanced Doppler frequency shift effect of the highly localized microwave backscattering in the upper hybrid resonance are reported. The experiment is performed at FT-2 tokamak, where a steerable focusing antenna set, allowing off equatorial plane plasma extraordinary wave probing fr...
Збережено в:
| Дата: | 2005 |
|---|---|
| Автори: | , , , , , , , , , , , , , , , |
| Формат: | Стаття |
| Мова: | English |
| Опубліковано: |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2005
|
| Назва видання: | Вопросы атомной науки и техники |
| Теми: | |
| Онлайн доступ: | https://nasplib.isofts.kiev.ua/handle/123456789/79157 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect / A. Altukhov, V.V. Bulanin, V.V. Dyachenko, L.A. Esipov, M.V. Gorokhov, A.D. Gurchenko, E.Z. Gusakov, M.A. Irzak, M.Yu. Kantor, D.V. Kouprienko, S.I. Lashkul, A.V. Petrov, A.N. Saveliev, A.Yu. Stepanov, S.V. Shatalin, E.O. Vekshina // Вопросы атомной науки и техники. — 2005. — № 1. — С. 195-199. — Бібліогр.: 5 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
nasplib_isofts_kiev_ua-123456789-79157 |
|---|---|
| record_format |
dspace |
| spelling |
nasplib_isofts_kiev_ua-123456789-791572025-02-23T17:24:37Z Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect Діагностика обертання плазми на токамаці ФТ-2 на основі посиленого ефекту доплера при розсіюванні назад у верхньому гібридному резонансі Диагностика вращения плазмы на токамаке ФТ-2 на основе усиленного эффекта доплера при рассеянии назад в верхнем гибридном резонансе Altukhov, A. Bulanin, V.V. Dyachenko, V.V. Esipov, L.A. Gorokhov, M.V. Gurchenko, A.D. Gusakov, E.Z. Irzak, M.A. Kantor, M.Yu. Kouprienko, D.V. Lashkul, S.I. Petrov, A.V. Saveliev, A.N. Stepanov, A.Yu. Shatalin, S.V. Vekshina, E.O. Plasma diagnostics Observations of enhanced Doppler frequency shift effect of the highly localized microwave backscattering in the upper hybrid resonance are reported. The experiment is performed at FT-2 tokamak, where a steerable focusing antenna set, allowing off equatorial plane plasma extraordinary wave probing from high magnetic field side, was installed. A separate line less than 1.5 MHz wide and shifted by up to 2 MHz is routinely observed in the backscattering spectrum under condition of accessible upper hybrid resonance. The enhanced frequency shift is explained by the growth of poloidal wave number of the probing wave in the resonance. Development of a new scheme for local diagnostics of fluctuations poloidal rotation based on this effect is started. У статті описуються спостереження посиленого ефекту Доплера в спектрі сигналу розсіяного назад у верхньому гібридному резонансі зондувальної хвилі. Експеримент виконаний на токамаці ФТ-2, на якому недавно були встановлені рухливі антени, що дозволяють здійснювати зондування плазми електромагнітними хвилями в незвичайній поляризації з боку сильного магнітного поля. За умови доступного верхнього гібридного резонансу в спектрі розсіювання спостерігалася лінія шириною менш 1.5 МГц, зрушена до 2 МГц. Ефект пояснений ростом полоідального хвильового числа зондувальної хвилі в резонансі. Почато розвиток нової схеми локальної діагностики обертання плазмових флуктуацій, заснованої на цьому ефекті. В статье описываются наблюдения усиленного эффекта Доплера в спектре сигнала рассеянного назад в верхнем гибридном резонансе зондирующей волны. Эксперимент выполнен на токамаке ФТ-2, на котором недавно были установлены подвижные антенны, позволяющие осуществлять зондирование плазмы электромагнитными волнами в необыкновенной поляризации со стороны сильного магнитного поля. При условии доступного верхнего гибридного резонанса в спектре рассеяния наблюдалась линия шириной менее 1.5 МГц, сдвинутая до 2 МГц. Эффект объяснён ростом полоидального волнового числа зондирующей волны в резонансе. Начато развитие новой схемы локальной диагностики вращения плазменных флуктуаций, основанной на этом эффекте. Supports of INTAS grants YSF2002-104, INTAS 01-2056, NWO-RFBR grant 047.016.015, RFBR grants 02-02-17591, 04-02-16534, 02-02-17589, 02-02-17684, HIII-2159.2003.2 are acknowledged. 2005 Article Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect / A. Altukhov, V.V. Bulanin, V.V. Dyachenko, L.A. Esipov, M.V. Gorokhov, A.D. Gurchenko, E.Z. Gusakov, M.A. Irzak, M.Yu. Kantor, D.V. Kouprienko, S.I. Lashkul, A.V. Petrov, A.N. Saveliev, A.Yu. Stepanov, S.V. Shatalin, E.O. Vekshina // Вопросы атомной науки и техники. — 2005. — № 1. — С. 195-199. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 52.55.Hc. https://nasplib.isofts.kiev.ua/handle/123456789/79157 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| topic |
Plasma diagnostics Plasma diagnostics |
| spellingShingle |
Plasma diagnostics Plasma diagnostics Altukhov, A. Bulanin, V.V. Dyachenko, V.V. Esipov, L.A. Gorokhov, M.V. Gurchenko, A.D. Gusakov, E.Z. Irzak, M.A. Kantor, M.Yu. Kouprienko, D.V. Lashkul, S.I. Petrov, A.V. Saveliev, A.N. Stepanov, A.Yu. Shatalin, S.V. Vekshina, E.O. Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect Вопросы атомной науки и техники |
| description |
Observations of enhanced Doppler frequency shift effect of the highly localized microwave backscattering in the upper hybrid resonance are reported. The experiment is performed at FT-2 tokamak, where a steerable focusing antenna set, allowing off equatorial plane plasma extraordinary wave probing from high magnetic field side, was installed. A separate line less than 1.5 MHz wide and shifted by up to 2 MHz is routinely observed in the backscattering spectrum under condition of accessible upper hybrid resonance. The enhanced frequency shift is explained by the growth of poloidal wave number of the probing wave in the resonance. Development of a new scheme for local diagnostics of fluctuations poloidal rotation based on this effect is started. |
| format |
Article |
| author |
Altukhov, A. Bulanin, V.V. Dyachenko, V.V. Esipov, L.A. Gorokhov, M.V. Gurchenko, A.D. Gusakov, E.Z. Irzak, M.A. Kantor, M.Yu. Kouprienko, D.V. Lashkul, S.I. Petrov, A.V. Saveliev, A.N. Stepanov, A.Yu. Shatalin, S.V. Vekshina, E.O. |
| author_facet |
Altukhov, A. Bulanin, V.V. Dyachenko, V.V. Esipov, L.A. Gorokhov, M.V. Gurchenko, A.D. Gusakov, E.Z. Irzak, M.A. Kantor, M.Yu. Kouprienko, D.V. Lashkul, S.I. Petrov, A.V. Saveliev, A.N. Stepanov, A.Yu. Shatalin, S.V. Vekshina, E.O. |
| author_sort |
Altukhov, A. |
| title |
Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect |
| title_short |
Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect |
| title_full |
Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect |
| title_fullStr |
Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect |
| title_full_unstemmed |
Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect |
| title_sort |
plasma rotation diagnostics at the ft-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2005 |
| topic_facet |
Plasma diagnostics |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/79157 |
| citation_txt |
Plasma rotation diagnostics at the FT-2 tokamak based on the upper hybrid resonance backscattering enhanced doppler effect / A. Altukhov, V.V. Bulanin, V.V. Dyachenko, L.A. Esipov, M.V. Gorokhov, A.D. Gurchenko, E.Z. Gusakov, M.A. Irzak, M.Yu. Kantor, D.V. Kouprienko, S.I. Lashkul, A.V. Petrov, A.N. Saveliev, A.Yu. Stepanov, S.V. Shatalin, E.O. Vekshina // Вопросы атомной науки и техники. — 2005. — № 1. — С. 195-199. — Бібліогр.: 5 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT altukhova plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT bulaninvv plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT dyachenkovv plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT esipovla plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT gorokhovmv plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT gurchenkoad plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT gusakovez plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT irzakma plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT kantormyu plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT kouprienkodv plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT lashkulsi plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT petrovav plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT savelievan plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT stepanovayu plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT shatalinsv plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT vekshinaeo plasmarotationdiagnosticsattheft2tokamakbasedontheupperhybridresonancebackscatteringenhanceddopplereffect AT altukhova díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT bulaninvv díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT dyachenkovv díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT esipovla díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT gorokhovmv díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT gurchenkoad díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT gusakovez díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT irzakma díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT kantormyu díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT kouprienkodv díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT lashkulsi díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT petrovav díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT savelievan díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT stepanovayu díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT shatalinsv díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT vekshinaeo díagnostikaobertannâplazminatokamacíft2naosnovíposilenogoefektudopleraprirozsíûvannínazaduverhnʹomugíbridnomurezonansí AT altukhova diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT bulaninvv diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT dyachenkovv diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT esipovla diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT gorokhovmv diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT gurchenkoad diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT gusakovez diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT irzakma diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT kantormyu diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT kouprienkodv diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT lashkulsi diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT petrovav diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT savelievan diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT stepanovayu diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT shatalinsv diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse AT vekshinaeo diagnostikavraŝeniâplazmynatokamakeft2naosnoveusilennogoéffektadopleraprirasseâniinazadvverhnemgibridnomrezonanse |
| first_indexed |
2025-11-24T03:45:26Z |
| last_indexed |
2025-11-24T03:45:26Z |
| _version_ |
1849641849260605440 |
| fulltext |
PLASMA DIAGNOSTICS
PLASMA ROTATION DIAGNOSTICS AT THE FT-2 TOKAMAK BASED
ON THE UPPER HYBRID RESONANCE BACKSCATTERING
ENHANCED DOPPLER EFFECT
A.B. Altukhov, V.V. Bulanin*, V.V. Dyachenko, L.A. Esipov, M.V. Gorokhov*,
A.D. Gurchenko, E.Z. Gusakov, M.A. Irzak, M.Yu. Kantor, D.V. Kouprienko, S.I. Lashkul,
A.V. Petrov*, A.N. Saveliev, A.Yu. Stepanov, S.V. Shatalin*, E.O. Vekshina*
Ioffe Institute, Politekhnicheskaya 26, 194021 St.Petersburg, Russia;
*SPbSPU, Politekhnicheskaya 29, 195251 St.Petersburg, Russia
Observations of enhanced Doppler frequency shift effect of the highly localized microwave backscattering in the upper
hybrid resonance are reported. The experiment is performed at FT-2 tokamak, where a steerable focusing antenna set,
allowing off equatorial plane plasma extraordinary wave probing from high magnetic field side, was installed. A
separate line less than 1.5 MHz wide and shifted by up to 2 MHz is routinely observed in the backscattering spectrum
under condition of accessible upper hybrid resonance. The enhanced frequency shift is explained by the growth of
poloidal wave number of the probing wave in the resonance. Development of a new scheme for local diagnostics of
fluctuations poloidal rotation based on this effect is started.
PACS: 52.55.Hc.
1. INTRODUCTION
Inhomogeneous plasma rotation, according to the
present day understanding, can play a substantial role in
energy confinement in toroidal plasmas, suppressing drift
micro turbulence and thus reducing anomalous heat and
particle fluxes. The Doppler frequency shift of Back
Scattering (BS) signal at oblique microwave plasma
probing is often used for diagnosing of poloidal plasma
velocity in magnetic fusion devices. The typical value of
frequency shift of BS microwave of several hundred kHz
in the “Doppler reflectometry” diagnostics based upon
this effect is usually substantially smaller than its
broadening, which complicates interpretation and reduce
the accuracy of measurements. Recently a possibility of a
drastic increase of the Doppler frequency shift of
microwave BS signal in toroidal devices, based on the
Upper Hybrid Resonance (UHR) BS was demonstrated
experimentally [1].The microwave BS experiment was
performed at FT-2 tokamak with a new steerable focusing
45 48 51 54 57 60 63
-7
0
7
0 dB
E
B
W-3 dB
r
θ
UHR
mssteerable focusing
double antennae
y
a
= ±2 cm
-1.5 dB
limiter
y
(c
m
)
R (cm)
q c o n v
k i
q θ
Fig.1. Poloidal FT-2 tokamak cross section with antennae set.
ik
r
– incident wave vector, convqr and qθ
r
– fluctuation wave
vector at BS efficiency maximum and it’s poloidal projection,
circles – central ray of the probing beam, triangles and
squares – probing beam at 1.5 dB and 3 dB power
suppression levels, ms – magnetic surface(dashed curve)
double antennae set, allowing off equatorial plane plasma
X-mode probing from high magnetic field side.
The spatial distribution of the focused probing beam,
computed using the beam tracing code [2], is shown in
Fig. 1. The maximal vertical displacement of antennae
center is ya = ±2 cm, whereas the diameter of the wave
beam at the position of UHR, where the probing
frequency satisfies condition f i
2= f ce
2 R f pe
2 r ,
as computed by the code, was close to the values
measured in vacuum (1.5 – 1.7 cm, depending on the
probing frequency in the range 52 – 69 GHz). According
to theoretical predictions [1, 3] and beam tracing
60.0 60.5 61.0 61.5
0
10
20
30
EBW
-1.5 dB
-1.5 dB
k θ
(
cm
-1
)
R (cm)
0 dB
10 20 30 40 50 60
0
1
2
3
4
5 0 dB
F BS
(a
rb
.u
n.
)
q
θ
= 2k
θ
(cm-1)
Fig.2. (a) Poloidal probing wave number near UHR,
(b) BS efficiency for central probing ray
Problems of Atomic Science and Technology. 2005. № 1. Series: Plasma Physics (10). P. 195-199 195
a
b
computation shown in Fig. 2a, the probing poloidal wave
number grows rapidly in the vicinity of the UHR linear
conversion point, where the BS cross section FBS(qθ)
possesses sharp maximum, as demonstrated in Fig. 2b.
This projection, which can be much larger than the
poloidal component of wave vector at the antenna, can
lead to substantial enhancement of the Doppler frequency
shift of the microwave BS by fluctuations moving with
poloidal plasma flow. The frequency shift corresponding
to fluctuation radial wave number q is given by
2
0 2 2
2
2 ( )
R ce
D
pe ce
UHR
q e e ff k V
R f f
θ
θ θ
й щ
к ъ= +
к ъ+Сл ы
r r
r , (1)
where Vθ is the fluctuation poloidal velocity; kθ0 gives
the probing extraordinary mode poloidal wave number
out of the UHR zone, eθ and e R are unit vectors in
poloidal and major radius directions; R gives the major
radius in the UHR. In agreement with theoretical
predictions a separate line less than 1.5 MHz wide and
shifted by up to 2 MHz, was reliably observable in the BS
spectrum under condition of accessible UHR [1].
6 8 6 6 6 4 6 2 6 0 5 8 5 6 5 4 5 2
- 0 . 5
0 . 0
0 . 5
1 . 0
1 . 5
f D
(M
H
z)
f i ( G H z )
6 0 6 1 6 2 6 3
- 1
0
1
2
3
4
V r e f l
V
U H
V θ
(k
m
/s
)
R ( c m )
V n e o
Fig.3. (a) Doppler frequency shift versus incident
frequency ( ya = +15 mm).(b) Poloidal velocity profiles
for Ip = 35 kA. Circles – UHR BS, stars – O-mode
Doppler reflectometry, dashed curve - neoclassical
dependens
2. ROTATION IN OHMIC REGIME
In this paper, the recently observed giant Doppler
frequency shift effect of the highly localized microwave
BS in the Upper Hybrid Resonance (UHR) [1] is applied
to FT-2 tokamak plasma rotation diagnostics in ohmic and
LH heating regimes. The obtained profiles of plasma
poloidal velocity are benchmarked against the Doppler
reflectometry data. The experiment is performed at
research FT-2 tokamak (R = 55 cm, a ≈ 8 cm, BT ≈ (1.7 ÷
2.2) T, Ip ≈ (19 ÷ 37) kA, ne(0) ≈ (0.5 ÷ 5)×1019 m-3, Te(0)
≈ 500 eV), where the RF power up to 120 kW at
frequency 918 MHz is launched into the plasma by a two-
waveguide grill.
Very different poloidal rotation profiles are measured in
ohmic discharges for plasma current values of 19 kA and
35 kA. The dependence of BS frequency shift on the
probing frequency in the high current case is shown in
Fig. 3a. The important feature of this dependence is
complicated behavior resulting in minimum at fi = 60.3
GHz and very steep variation at fi = 57.3 GHz. The
corresponding poloidal rotation profile, determined using
(1) under supposition that the BS spectrum maximum
corresponds to the maximum of BS efficiency, situated at
qconv≡2 2πf i /c c /V Te , is given in Fig. 3b by
circles. As it is seen, the poloidal plasma velocity
increases towards LCFS, where it possesses discontinuity
in agreement with expectations of neoclassical theory (the
corresponding estimation is shown in Fig. 3b by dashed
curve). The corresponding velocity values determined
using the UHR BS technique fit well those obtained by
the O-mode Doppler reflectometry, which are shown by
stars in Fig. 3b. Out of the LCFS the rotation velocity
changes sign, which indicate the dominant role of electron
losses to the limiter along the magnetic field lines.
In the lower current regime no poloidal rotation
discontinuity at the LCFS was observed. As it is shown in
Fig. 4, at current less than 30 kA the rotation velocity
decreases continuously towards the LCFS, where it
changes sign, which is not consistent with the neoclassical
6 0 6 1 6 2 6 3
- 1
0
1
2
3
4
V
r e f l
V
U H
V θ
(
km
/s)
R ( c m )
Fig.4. Poloidal velocity profiles for Ip < 30 kA
circles – UHR BS, stars – O-mode Doppler reflectometry
theory expectations and indicates important role of
anomalous electron losses mechanism in formation of
plasma potential in this region. It should be stressed that
in this regime as well the poloidal rotation velocity
obtained by Doppler reflectometry and UHR BS
diagnostics are in nice agreement. It should be underlined
that in spite of the fact both microwave BS techniques
196
provide information on fluctuation rotation, the wave
length of those fluctuations differs by two orders of
magnitude. It is very unlikely that the phase velocities for
such a different fluctuations coincide, which gives an
argument in favor of plasma rotation origin of the
frequency shift measured by both diagnostics. It is
important to note that the calculated electron diamagnetic
drift velocity all over the measurement region exceeds the
experimental values of poloidal rotation velocity by a
factor of 3 – 5. This result provides additional
confirmation to our assumption that the Doppler
frequency shift is rather associated with the plasma flow
than with fluctuation phase velocity, which is quite
natural because the fluctuations producing BS in the UHR
possess radial wave number much higher than the
poloidal one and thus are not similar to the drift wave
eigen-modes.
3. PLASMA ROTATION SUPPRESSION AT
LH HEATING
In the present paper a specific regime of LH heating at
densities 2⋅1013 < ne(0) <3⋅1013 cm-3 , at which the LHCD
and electron heating terminates and wave – ion
interaction and ion heating starts, was investigated. The
wave forms of the discharge are shown in Fig.5. As it
0
2
15202530354045
0
3
ne(0)
(1019 m-3)
t (ms)
0
1
2
B
T
(T)
0
2
4
IH
U
P
(V)
CD
0
10
20
IP (kA) RF
CD
CX
1 keV
(arb.un.)
IH
Fig.5. Discharge wave forms
is seen there, just at the onset of RF pulse at t=30 ms an
evident decrease is observable in the loop voltage signal
indicating the LHCD effect. This effect is accompanied
by the plasma density growth, leading to the LHCD
termination at t=31 ms. Soon after that, at t=32 ms, the
steep increase of fast ion population at energy in 1 keV
range is observed in the discharge by the charge exchange
diagnostic, indicating transition to the LH Ion Heating
(LHIH) regime. Under these conditions excitation of
small scale component of plasma turbulence was
observed at FT-2 tokamak by CO2 and UHR scattering
diagnostics [4, 5]. Here we study the reasons and
consequences of this effect.
The temporal evolution of the UHR BS spectrum at probing
frequency fi=62 GHz during the RF pulse is shown in Fig.6.
As it seen at 30 ms <t<31 ms, the BS spectrum remains
similar to that observed in ohmic heating. The fast reduction of
the Doppler frequency shift and the spectrum narrowing starts
simultaneously with the fast neutral flux growth. This
evolution of the BS spectrum is accompanied by steep
increase of its amplitude. The relaxation of the BS spectrum to
that, observed in the ohmic discharge, starts just after the RF
power switch off. The poloidal velocity profiles, determined
from the Doppler frequency shift of the UHR BS spectra are
shown in Fig.7 for three typical moments.
26 28 30 32 34 36 38
-3
-2
-1
0
1
2
3
t , ms
f s -
f i ,
M
H
z
0.10
0.14
0.20
0.28
0.39
0.55
0.77
1.1
1.5
2.1
3.0
RF
Fig.6. UHR BS spectrum evolution (62 GHz)
5 6 7 8
0 . 0
0 . 5
1 . 0
1 . 5
2 . 0
2 . 5
3 4 m s
3 1 . 5 m s
V θ
(k
m
/s
)
x ( c m )
2 7 m s
Fig.7. Fluctuation poloidal velocity profiles (UHR BS)
Before the RF pulse the velocity profile is typical for
measured by this technique in the low current regime. The
velocity monotonically decreases when approaching the
plasma edge and change sign in the vicinity of LCFS
(dashed curve in Fig.7). At the LHCD phase the velocity
increases slightly, however its shear remains unchanged
during the first millisecond after RF power onset (light
curve in Fig.7). The dramatic variation of the velocity
profile is observed only after transition to the LHIH regime
at t> 32 ms. As the result, at t= 34 ms poloidal velocity is
substantially reduced and its profile in the edge region
become flat (solid curve in Fig.7). In 2 ms after RF power
switch off the rotation profile relaxes to the initial state. It
is important to note that the flattening of the rotation profile
and related decrease of the poloidal velocity shear results in
strong growth of the BS signal, proportional to the level of
small scale density fluctuations, as it is shown by
dependences of BS signal on the UHR position, plotted by
filled and empty points in Fig.8 for the LHCD and LH ion
heating phase of RF pulse correspondingly. Similar
observations were made also by the Doppler reflectometry
technique. Suppression of poloidal rotation was measured
by this diagnostic during the RF pulse, which resulted in
decrease of the velocity shear at the plasma edge, by the
end of the RF pulse.
197
5 6 7 8
1
10
100
LHCD
LHIH
A S
(a
.u
.)
x (cm)
Fig.8. UHR BS spectrum amplitude profile
27 28 29 30 31 32 33 34 35 36 37
0
10
20
30
40
50
60
Refl 34.5GHz (5.3-6.4)cm
UHR BS 62.5GHz (4.3-5.5)cm
UHR BS 57.5GHz (5.3-6.6)cm
P s
(a
rb
.u
n.
)
t (ms)
CX
UP
Fig.9. Scattered power evolution
It should be mentioned that the velocity value, as well as
the profile form, measured by this two microwave
diagnostics do not coincide, which is probably explained
by contribution of wave numbers smaller than those
corresponding to the BS cross section maximum. The
level of the Doppler reflectometry signal at the plasma
edge also experienced substantial growth at the transition
from the LHCD regime to the LHIH, as it is shown in
Fig.9 for Doppler reflectometry probing frequency 34.5
GHz. This growth is only partly associated with the outer
shift of the cut off layer and indicates the growth of long
scale component of tokamak micro turbulence. The
dependence of the UHR BS signal at probing frequency
62.5 GHz (dash) and 57.5 GHz (dash dot) is shown in
Fig.9 for comparison. The drastic increase of the
turbulence level initiated by the rotation shear suppression
is accompanied by substantial cooling of the electron
component at the plasma periphery, which occurs at the
background of growing density (see Fig.10).
The typical feature of the plasma rotation at the very edge
(out of the LCFS), observed by the UHR BS technique at
RF power onset was quick change of velocity direction.
This effect, well pronounced in all regimes of interaction
and at different grill antenna phasing is illustrated by
Fig.11 in which the temporal variation of the BS spectrum
is shown. The possible explanation robust effect taking
place in the vicinity of the LH grill, which is situated in
the UHR BS diagnostics poloidal cross section, is based
on the improvement of electron confinement along
magnetic field due to their trapping in ponderomotive
potential
2 2
2 16
pe z
RF
RF
f E
f
Φ
π
=
%
produced by two LH wave resonance cones, shown in
Fig.12. ( zE% here is the toroidal component of RF field).
-8 -6 -4 -2 0 2 4 6 8
0
100
200
300
400 Te (eV)
x (cm)
0.0
0.5
1.0
1.5
2.0
2.5
31.5ms
34ms
ne (1013 cm-3)
Fig.10. Electron density and temperature profiles
26 28 30 32 34 36 38
-2
-1
0
1
2
t , ms
f s -
f i ,
M
H
z
0.50
0.77
1.2
1.9
2.9
4.5
6.9
11
17
26
40
RF
Fig.11. UHR BS spectrum evolution (53 GHz)
-15 -10 -5 0 5 10 15
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Φ
RF
/
n eT e
z (cm)
x = 7.6 cm {0,π/2}; x = 7.2 cm {0,π/2}
x = 7.6 cm {0,π}; x = 7.2 cm {0,π}
Fig.12. The ponderomotive potential in the LH grill vicinity
198
4. CONCLUSIONS
Based upon the robust Enhanced Doppler effect
observed in the off equatorial plane microwave UHR BS
experiment at FT-2 tokamak a new scheme for precise
diagnostics of plasma fluctuations poloidal rotation in
tokamaks and stellarators possessing high spatial and
temporal resolution has been developed. The new
diagnostic is successfully benchmarked against the
Doppler reflectometry technique data and than applied to
study of plasma rotation and turbulence behavior in
ohmic and RF heated plasma. Two types of poloidal
rotation profiles are observed at FT-2 tokamak in ohmic
regime at plasma currents 20 kA and 35 kA. Suppression
of fluctuation poloidal rotation and growth of their
amplitude is observed at transition from LHCD to ion
heating.
Supports of INTAS grants YSF2002-104, INTAS 01-
2056, NWO-RFBR grant 047.016.015, RFBR grants 02-
02-17591, 04-02-16534, 02-02-17589, 02-02-17684,
HIII-2159.2003.2 are acknowledged.
REFERENCES
1. A.B. Altukhov, A.D. Gurchenko, E.Z. Gusakov et al.
Observation of Enhanced Doppler Effect in the Upper
Hybrid Resonance Backscattering Experiment at the FT-2
Tokamak//Proc. Of the 30-th EPS Conf. on Control.
Fusion and Plasma Phys., St.Petersburg, 7-11 July, 2003/
ECA 27A, 2003, P-4.170pd.
2. A.N. Saveliev, A.D. Piliya. The Method of Virtual
Beams for Microwave Radiation in Toroidal
Plasmas//Proc.of the 30-th EPS Conf. on Control. Fusion
and Plasma Phys., St.Petersburg, 7-11 July, 2003/ ECA
27A, 2003, P-2.20.
3. D.G. Bulyiginskiy, A.D.Gurchenko, E.Z.Gusakov et al.
RADAR upper hybrid resonance scattering diagnostics of
small-scale fluctuations and waves in tokamak plasmas//
Phys. Plasmas (8). 2001, p.2224.
4. V.N. Budnikov et al. Microturbulence behaviour study
during LH heating in FT-2 tokamak by CO2-
laserscattering//Proc.of the 23-th EPS Conf. on Controll.
Fusion and Plasma Phys., Kiev, 24-28 June,1996/ ECA
20C, 1996, P.855.
5. V.N. Budnikov et al. Study of Plasma Turbulence by
Microwave Backscattering Technique in Lower-Hybrid
Heating Experiments on the FT-2 Tokamak// Plasma
Phys. Rep. (24). 1998, p. 233.
ДИАГНОСТИКА ВРАЩЕНИЯ ПЛАЗМЫ НА ТОКАМАКЕ ФТ-2 НА ОСНОВЕ УСИЛЕННОГО
ЭФФЕКТА ДОПЛЕРА ПРИ РАССЕЯНИИ НАЗАД В ВЕРХНЕМ ГИБРИДНОМ РЕЗОНАНСЕ
A.Б. Алтухов, В.В. Буланин, В.В. Дьяченко, Л.А. Есипов, М.В. Горохов,
А.Д. Гурченко, Е.З. Гусаков, М.А. Иржак, М.Ю. Кантор, Д.В. Куприенко, С.И. Лашкул,
А.В. Петров, А.Н. Савельев, А.Ю. Степанов, С.В. Шаталин, Е.О. Векшина
В статье описываются наблюдения усиленного эффекта Доплера в спектре сигнала рассеянного назад в верхнем
гибридном резонансе зондирующей волны. Эксперимент выполнен на токамаке ФТ-2, на котором недавно были
установлены подвижные антенны, позволяющие осуществлять зондирование плазмы электромагнитными
волнами в необыкновенной поляризации со стороны сильного магнитного поля. При условии доступного
верхнего гибридного резонанса в спектре рассеяния наблюдалась линия шириной менее 1.5 МГц, сдвинутая до
2 МГц. Эффект объяснён ростом полоидального волнового числа зондирующей волны в резонансе. Начато
развитие новой схемы локальной диагностики вращения плазменных флуктуаций, основанной на этом эффекте.
ДІАГНОСТИКА ОБЕРТАННЯ ПЛАЗМИ НА ТОКАМАЦІ ФТ-2 НА ОСНОВІ ПОСИЛЕНОГО ЕФЕКТУ
ДОПЛЕРА ПРИ РОЗСІЮВАННІ НАЗАД У ВЕРХНЬОМУ ГІБРИДНОМУ РЕЗОНАНСІ
A.Б. Алтухов, В.В. Буланін, В.В. Дьяченко, Л.А. Єсипов, М.В. Горохов,
А.Д. Гурченко, Є.З. Гусаков, М.А. Іржак, М.Ю. Кантор, Д.В. Куприєнко, С.І. Лашкул,
О.В. Петров, А.Н. Савєльев, А.Ю. Степанов, С.В. Шаталін, Є.О. Векшина
У статті описуються спостереження посиленого ефекту Доплера в спектрі сигналу розсіяного назад у
верхньому гібридному резонансі зондувальної хвилі. Експеримент виконаний на токамаці ФТ-2, на якому
недавно були встановлені рухливі антени, що дозволяють здійснювати зондування плазми електромагнітними
хвилями в незвичайній поляризації з боку сильного магнітного поля. За умови доступного верхнього гібридного
резонансу в спектрі розсіювання спостерігалася лінія шириною менш 1.5 МГц, зрушена до 2 МГц. Ефект
пояснений ростом полоідального хвильового числа зондувальної хвилі в резонансі. Почато розвиток нової
схеми локальної діагностики обертання плазмових флуктуацій, заснованої на цьому ефекті.
199
|