New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator
A new electron cyclotron emission antenna was designed to be installed outside of Uragan-3M vacuum tank. The system will be utilizing different diagnostic port to minimize the length of the output microwave beam. Its design is based on Gaussian beam optics and consists of two plane and two concave m...
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| Cite this: | New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator / R.O. Pavlichenko // Вопросы атомной науки и техники. — 2014. — № 6. — С. 262-265. — Бібліогр.: 5 назв. — англ. |
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Pavlichenko, R.O. 2015-05-22T20:19:07Z 2015-05-22T20:19:07Z 2014 New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator / R.O. Pavlichenko // Вопросы атомной науки и техники. — 2014. — № 6. — С. 262-265. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 52.55.Hc, 52.70.Gw, 52.35.Hr, 52.25.Os, 42.60.Jf, 42.15.Eq. https://nasplib.isofts.kiev.ua/handle/123456789/81967 A new electron cyclotron emission antenna was designed to be installed outside of Uragan-3M vacuum tank. The system will be utilizing different diagnostic port to minimize the length of the output microwave beam. Its design is based on Gaussian beam optics and consists of two plane and two concave mirrors. The concave mirror surfaces are defined using the concept of elliptical surface, where the origin of emission and outside detection antenna coincide with foci of ellipsoid. The new electron cyclotron emission antenna will be installed for a 2015 experiment to measure the electron temperature profile and its fluctuations. This paper reports the general design of the new quasi-optical antenna system. Разрабатывается новая квазиоптическая антенная система для анализа электронно-циклотронного излучения, компоненты которой будут установлены снаружи вакуумной камеры Ураган-3М. Система будет использовать другой диагностический порт, чтобы минимизировать длину выходного СВЧ-луча. Этот дизайн основан на принципах оптики гауссовых пучков и состоит из двух плоских и двух вогнутых зеркал. Вогнутые зеркальные поверхности описываются с помощью геометрии эллиптических поверхностей, при использовании которых положение источника излучения и приемной антенны совпадают с фокусами эллипсоида. Новая антенная система электронно-циклотронного излучения будет установлена для экспериментов по измерению профиля электронной температуры и ее колебаний в 2015 году. В общих чертах представлен дизайн новой квазиоптической антенной системы. Розробляється нова квазіоптична антенна система для аналізу електронно-циклотронного випромінювання, компоненти якої будуть встановлені зовні вакуумної камери Ураган-3М. Система буде використовувати інший діагностичний порт, щоб мінімізувати довжину вихідного НВЧ-променя. Цей дизайн заснований на принципах оптики гаусових пучків і складається з двох плоских і двох увігнутих дзеркал. Увігнуті дзеркальні поверхні описуються за допомогою геометрії еліптичних поверхонь, при використанні яких положення джерела випромінювання і приймальної антени збігаються з фокусами еліпсоїда. Нова антенна система електронно-циклотронного випромінювання буде встановлена для експериментів по вимірюванню профілю електронної температури і її коливань в 2015 році. B загальних рисах представлений дизайн нової квазіоптичної антенної системи. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Диагностика плазмы New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator Новая квазиоптическая система для приема электронного циклотронного излучения на стеллараторе Ураган-3М Нова квазіоптична система для приему електронного циклотронного випромінювання на стелараторі Ураган-3М Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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| title |
New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator |
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New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator Pavlichenko, R.O. Диагностика плазмы |
| title_short |
New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator |
| title_full |
New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator |
| title_fullStr |
New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator |
| title_full_unstemmed |
New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator |
| title_sort |
new quasioptical receiving system for electron cyclotron emission diagnostics in uragan-3m stellarator |
| author |
Pavlichenko, R.O. |
| author_facet |
Pavlichenko, R.O. |
| topic |
Диагностика плазмы |
| topic_facet |
Диагностика плазмы |
| publishDate |
2014 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Новая квазиоптическая система для приема электронного циклотронного излучения на стеллараторе Ураган-3М Нова квазіоптична система для приему електронного циклотронного випромінювання на стелараторі Ураган-3М |
| description |
A new electron cyclotron emission antenna was designed to be installed outside of Uragan-3M vacuum tank. The system will be utilizing different diagnostic port to minimize the length of the output microwave beam. Its design is based on Gaussian beam optics and consists of two plane and two concave mirrors. The concave mirror surfaces are defined using the concept of elliptical surface, where the origin of emission and outside detection antenna coincide with foci of ellipsoid. The new electron cyclotron emission antenna will be installed for a 2015 experiment to measure the electron temperature profile and its fluctuations. This paper reports the general design of the new quasi-optical antenna system.
Разрабатывается новая квазиоптическая антенная система для анализа электронно-циклотронного излучения, компоненты которой будут установлены снаружи вакуумной камеры Ураган-3М. Система будет использовать другой диагностический порт, чтобы минимизировать длину выходного СВЧ-луча. Этот дизайн основан на принципах оптики гауссовых пучков и состоит из двух плоских и двух вогнутых зеркал. Вогнутые зеркальные поверхности описываются с помощью геометрии эллиптических поверхностей, при использовании которых положение источника излучения и приемной антенны совпадают с фокусами эллипсоида. Новая антенная система электронно-циклотронного излучения будет установлена для экспериментов по измерению профиля электронной температуры и ее колебаний в 2015 году. В общих чертах представлен дизайн новой квазиоптической антенной системы.
Розробляється нова квазіоптична антенна система для аналізу електронно-циклотронного випромінювання, компоненти якої будуть встановлені зовні вакуумної камери Ураган-3М. Система буде використовувати інший діагностичний порт, щоб мінімізувати довжину вихідного НВЧ-променя. Цей дизайн заснований на принципах оптики гаусових пучків і складається з двох плоских і двох увігнутих дзеркал. Увігнуті дзеркальні поверхні описуються за допомогою геометрії еліптичних поверхонь, при використанні яких положення джерела випромінювання і приймальної антени збігаються з фокусами еліпсоїда. Нова антенна система електронно-циклотронного випромінювання буде встановлена для експериментів по вимірюванню профілю електронної температури і її коливань в 2015 році. B загальних рисах представлений дизайн нової квазіоптичної антенної системи.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/81967 |
| citation_txt |
New quasioptical receiving system for electron cyclotron emission diagnostics in Uragan-3M stellarator / R.O. Pavlichenko // Вопросы атомной науки и техники. — 2014. — № 6. — С. 262-265. — Бібліогр.: 5 назв. — англ. |
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2025-11-26T20:10:13Z |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2014. №6(94)
262 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2014, №6. Series: Plasma Physics (20), p. 262-265.
NEW QUASIOPTICAL RECEIVING SYSTEM FOR ELECTRON
CYCLOTRON EMISSION DIAGNOSTICS IN URAGAN-3M
STELLARATOR
R.O. Pavlichenko
Institute of Plasma Physics NSC KIPT, Kharkov, Ukraine
A new electron cyclotron emission antenna was designed to be installed outside of Uragan-3M vacuum tank. The
system will be utilizing different diagnostic port to minimize the length of the output microwave beam. Its design is
based on Gaussian beam optics and consists of two plane and two concave mirrors. The concave mirror surfaces are
defined using the concept of elliptical surface, where the origin of emission and outside detection antenna coincide
with foci of ellipsoid. The new electron cyclotron emission antenna will be installed for a 2015 experiment to
measure the electron temperature profile and its fluctuations. This paper reports the general design of the new quasi-
optical antenna system.
PACS: 52.55.Hc, 52.70.Gw, 52.35.Hr, 52.25.Os, 42.60.Jf, 42.15.Eq.
INTRODUCTION
Electron cyclotron emission (ECE) measurement is a
powerful diagnostics for electron temperature profile
measurement of high temperature plasmas confined in
magnetic field. For many years Uragan-3M (U-3M)
stellarator was equipped with conventional single
antenna heterodyne radiometer [1, 2]. The present
antenna and waveguide system utilize mostly X-band
(λ=0.03 m) conventional microwave components to
deliver EC radiation from plasma to the detection
system. This antenna is not optimized for the frequency
range of the second harmonic of ECE (32…40 GHz) for
the central magnetic field 0.7 T of U-3M stellarator. The
direction of the conical horn (with diameter D=0.06 m)
is fixed in the equatorial plane of the plasma and shifted
in the direction of low field side to the distance which
correspond the position of the inner surface of the
helical coils at the radial position . Thus,
its directivity is set to be at near field (NF) zone of the
antenna (Fig. 1), which in the terms of antenna
dimension and radiation wavelength separates with
far field (FF) zone and has to satisfy following
condition: .
1. QO ANTENNA SYSTEMS
1.1. FOCUSING OF THE QO BEAM
During past experiments a relatively little attention
was paid to the ECE antennae and ‘optics’ of viewing
the U-3M plasmas. The EC emission, with a frequency
of more than 30 GHz, is transported according the
quasi-optical (QO) phenomenon. One can see the clear
benefits that will follow such a controlled and well
defined view of receiving QO antenna system. They are:
much better spatial resolution of localization of ECE
radiation origin, possible removal of data ambiguities
caused by reflection from helical coils and other inner
structure of U-3M, and better possibility of definitive
measurements on the polarization state of radiation (O-,
X-wave separation). Following the framework of the
QO antenna system design that was considered in [3-4]
the general layout is presented in the Fig. 2.
For QO system focusing of the beam by an elliptical
mirror (or equivalent lens) can be described as follows.
Fig. 1. Schematic view of conical horn beam for NF
zone and FF zone with Poincaré plot of the U-3M
magnetic fluxes and magnetic field (upper); calculated
corresponding NF and FF antenna patterns
For a paraxial rays approximation mirror acts as a
phase transformer with corresponding phase change
proportional to the square of the distance of the ray
from the axis of propagation where f is
the focal length. Following the formalism of Kogelnik
and Li [5] the phase transforming properties, the thin
ISSN 1562-6016. ВАНТ. 2014. №6(94) 263
lens formula , where R is radii of
the phase front curvature, will be transform into:
Fig. 2. Layout of the proposed QO antenna system for
the U-3M ECE system. Old X-band conical horn
. (1)
The output beam parameters (subscript index 2) could
be presented in terms of input beam. Depending of
which parameter beam waist at the focus ( ) or
corresponding waist distance ( ) have to be easily
evaluated into the following equations:
, (2.a)
. (2.b)
A particularly useful case of the QO beam focusing
is that occurs when the waist of the input beam is
located at a distance equal to the focal length of the
mirror . Then one can see that the
location of the output waist is independent of the
wavelength (frequency) of the radiation, and
the beam waist at the certain
distance expanded wider for the smaller wavelength.
1.2. FOCUSING OF THE BEAM BY MEANS OF
ELLIPTIC SURFACE
The radial spatial resolution of the radiometer is
determined by the frequency resolution of the
instrument. Toroidal and poloidal resolution depends on
corresponding beam radii (perpendicular to radial
direction). Since that the highest resolution has to be at
the plasma centre it is practically the best way to create
QO beam which has minimal waist at the plasma centre.
This could be done by imaging some adjustable aperture
with the help of a lens or of a mirror. However two
effects could complicate the simple geometric optics
picture. First the diffraction spreads the beam by an
angle given approximately by the ratio of the radiation
wavelength to the vacuum window diameter.
It is essential that the output vacuum window
diameter has to be twice wider than the beam waist at
this position. Secondly, refraction by the plasma itself
could spread the beam significantly. It becomes
particularly important when the viewing direction does
not coincide with the direction of density gradient. To
get smaller refraction effect one has to use higher
frequencies, thus, having possibility to measure higher
harmonics.
Fig. 3. Geometry of the elliptic surface with general
notations
Once radiation passes through the window it must be
transported to the detector. This can be distance of many
meters. But before transporting the beam it is essential
to insert a polarizer to obtain the desired mode of
polarization before transporting the beam. The
transportation could be done either by QO waveguides
or by trains of QO lenses. The antenna consists of four
stainless steel mirrors. Three of them are plane mirrors
and one is the concave elliptical mirror. This is done to
optimize the mirrors layout, which is determined by the
spot size of the QO beam at the plasma center and the
beam passed through the vacuum window, matching it
to the size of the horn detection antenna. In order to
select pure X-mode polarized beam, a wire grid
polarizer has to be installed outside vacuum window. To
improve the measured microwave intensity, it is
desirable to enlarge elliptical mirror, which faces the
plasma. To enhance the spatial resolution of the QO
system in comparison to the present conical horn
antenna the plasma spot size must be at least one order
smaller than plasma radius
1.3. DESIGN OF THE ELLIPTIC CONCAVE
MIRROR SURFACE
An offset ellipsoidal reflector acts as ‘virtual’ ideal
thin lens and could be evaluated via the incident and
reflected phase front radii of curvature , . They
could be matched by an equivalent lens focal length ;
and by the angle of incidence . Then the standard
equation of the ellipsoid for the Cartesian coordinates
(Fig. 3) has form:
. (3)
Translating to coordinates and after simple
transformations Eq.3 will have the form:
, (4)
where are the functions of
,
264 ISSN 1562-6016. ВАНТ. 2014. №6(94)
,
For the chosen two radii of ellipse and
the focus is .
It is shown in the Fig. 6 that antenna design is optimized
to path through the limited space between helical coils,
and small vacuum window port. The focusing spot
diameter is about 0.04 m at HWPM (-3dB level). The
output part of the QO beam has diameter of 0.09 m and
went through the vacuum window without truncation.
The diameter of the window is 0.2 m and it larger than
the parameter. Here, is the width at which the
beam intensity is of that at the beam center.
Fig. 4. Schematic view of QO mirrors layout. The
system consists of three mirrors, and one beam splitter.
The layout is determined by the spot size at the plasma
and the beam is passed through the vacuum window,
matching it to the conical type waveguide antennas from
the air side
Fig. 5. Poincaré plot of the elliptic mirror surface of the
main focusing mirror M1
Fig. 6. Calculation of the QO 37 GHz beam pattern (to
simplify beam geometry strait line approach is chosen)
1.4. DICHROIC PLATE
In the microwave frequency range, the dichroic filter
(DF) is a metal plate with many holes. The holes work
as circular waveguides, and thus the DF can be used as a
conventional high-pass filter. Figure 9 shows a
calculation of the cutoff response of a 50 GHz dichroic
filter. This value is chosen to split ECE 2X and ECE 3X
radiation from the plasma. Evaluation of the holes
diameter could be done according the formula of cut-off
frequency in the circular waveguide. Maxwell equation
for the electric field in cylindrical coordinates could be
written as , where is the
direction of wave propagation, can be written as:
Here is wave number. Under the
boundary conditions for the wave
, the solution can be obtained as ,
, where is the zero point of ,
, cut-off frequency is:
, , finally for
practical convenience one can use practical relation:
Fig. 7. Calculated HPF (cut-off frequency set to
50 GHz) for different thickness of the dichroic plate
and
According to this for the cut-off frequency of
50 GHz the diameter of the drilled holes , which
are arranged (Fig. 7) in hexagon manner must be
4.6 mm. This filter rejects signals at frequency lower
than 50 GHz by the level of more than -20 dB. Although
there are may be some sharp undulations in a pass-band
ISSN 1562-6016. ВАНТ. 2014. №6(94) 265
range (higher than 50 GHz) for the real thing the
performance of DF is better than that of a waveguide-
section-high-pass-filter. Finally we decided that the
dichroic filter and the small horn antenna would be
employed as ECE detector frontend. Simultaneously DP
could be act as a good reflector for the lower frequency
range.
CONCLUSIONS
Fusion research requires understanding of transport
of energy and particles in toroidal devices. Microwave
diagnostics (electron cyclotron emission and
reflectometry) are useful to study transport physics
because they are sensitive diagnostics with high time
and spatial resolutions. Electron cyclotron emission
(ECE) is employed to measure radial distribution of
electron temperature ( ) in toroidal confinement
devices. The ECE intensity is proportional to and the
ECE frequency is proportional to magnetic field, which
is different in different radius. In reflectometry, the
reflected frequency depends on electron density ( ),
since higher density plasma reflects microwave with
higher frequency, and phase delay or time delay of the
reflected signal corresponds to the radial position.
To extend the ability of the ECE system to operate
with any other microwave diagnostics (reflectometry or
interferometry) in the same or lower frequency range, a
quasi-optical splitter (dichroic plate) is used. For
frequencies below the cutoff frequency, the dichroic
filter acts as a plane mirror with a very low leakage rate.
The other advantage of large aperture optics for ECE (or
other microwave diagnostics) is to form an image of the
reflecting/emitting layer onto an array of detectors
(instead of single antenna) located at the image plane,
enabling localized sampling of small plasma areas and
to become a microwave imaging diagnostics.
Microwave imaging diagnostics using the above
techniques has a potential to visualize 3D view of
turbulence.
REFERENCES
1. R.O. Pavlichenko et al. Peculiarities of the
radiometric measurements on Uragan-3M torsatron for
RF heated plasma // Problems of Atomic Science and
Technology. Series “Plasma physics” (17). 2011, № 71,
p. 191-193.
2. V.S. Voitsenya et al. Progress in stellarator research
in Kharkov IPP // Physica Scripta. 2014, v. T161,
p. 014009.
3. S. Yamaguchi et al. Microwave imaging
reflectometry in LHD // Review of Scientific
Instruments. 2006, v. 77, p. 10E930.
4. Design and Installation of a New Electron Cyclotron
Emission Diagnostic Antenna in LHD // Plasma and
Fusion Research: Regular Articles. 2011, v. 6,
p. 2402114-1-2402114-4.
5. H. Kogelnik, T. Li. Laser Beams and Resonators //
Applied Optics. 1966, v. 5, № 10, p. 1550-1567.
Article received 28.10.2014
НОВАЯ КВАЗИОПТИЧЕСКАЯ СИСТЕМА ДЛЯ ПРИЕМА ЭЛЕКТРОННОГО ЦИКЛОТРОННОГО
ИЗЛУЧЕНИЯ НА СТЕЛЛАРАТОРЕ УРАГАН-3М
Р.О. Павличенко
Разрабатывается новая квазиоптическая антенная система для анализа электронно-циклотронного
излучения, компоненты которой будут установлены снаружи вакуумной камеры Ураган-3М. Система будет
использовать другой диагностический порт, чтобы минимизировать длину выходного СВЧ-луча. Этот
дизайн основан на принципах оптики гауссовых пучков и состоит из двух плоских и двух вогнутых зеркал.
Вогнутые зеркальные поверхности описываются с помощью геометрии эллиптических поверхностей, при
использовании которых положение источника излучения и приемной антенны совпадают с фокусами
эллипсоида. Новая антенная система электронно-циклотронного излучения будет установлена для
экспериментов по измерению профиля электронной температуры и ее колебаний в 2015 году. В общих
чертах представлен дизайн новой квазиоптической антенной системы.
НОВА КВАЗІОПТИЧНА СИСТЕМА ДЛЯ ПРИЕМУ ЕЛЕКТРОННОГО ЦИКЛОТРОННОГО
ВИПРОМІНЮВАННЯ НА СТЕЛАРАТОРІ УРАГАН-3М
Р.О. Павліченко
Розробляється нова квазіоптична антенна система для аналізу електронно-циклотронного
випромінювання, компоненти якої будуть встановлені зовні вакуумної камери Ураган-3М. Система буде
використовувати інший діагностичний порт, щоб мінімізувати довжину вихідного НВЧ-променя. Цей
дизайн заснований на принципах оптики гаусових пучків і складається з двох плоских і двох увігнутих
дзеркал. Увігнуті дзеркальні поверхні описуються за допомогою геометрії еліптичних поверхонь, при
використанні яких положення джерела випромінювання і приймальної антени збігаються з фокусами
еліпсоїда. Нова антенна система електронно-циклотронного випромінювання буде встановлена для
експериментів по вимірюванню профілю електронної температури і її коливань в 2015 році. B загальних
рисах представлений дизайн нової квазіоптичної антенної системи.
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