Recent developments in the ISTTOK heavy ion beam diagnostic
The heavy ion beam diagnostic (HIBD) presents a powerful tool for investigations of hot plasmas in thermonuclear devices with magnetic confinement. When injected into the plasma, the primary probing beam of singly charged positive ions is ionized to a doubly charged state by impact with the plasma e...
Збережено в:
| Дата: | 2016 |
|---|---|
| Автори: | , , , |
| Формат: | Стаття |
| Мова: | English |
| Опубліковано: |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2016
|
| Назва видання: | Вопросы атомной науки и техники |
| Теми: | |
| Онлайн доступ: | http://dspace.nbuv.gov.ua/handle/123456789/115467 |
| 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: | Recent developments in the ISTTOK heavy ion beam diagnostic / I.S. Nedzelskiy, A. Malaquias, R.B. Henriques, R. Sharma // Вопросы атомной науки и техники. — 2016. — № 6. — С. 297-301. — Бібліогр.: 9 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
irk-123456789-115467 |
|---|---|
| record_format |
dspace |
| spelling |
irk-123456789-1154672017-04-06T03:02:38Z Recent developments in the ISTTOK heavy ion beam diagnostic Nedzelskiy, I.S. Malaquias, A. Henriques, R.B. Sharma, R. Plasma diagnostics The heavy ion beam diagnostic (HIBD) presents a powerful tool for investigations of hot plasmas in thermonuclear devices with magnetic confinement. When injected into the plasma, the primary probing beam of singly charged positive ions is ionized to a doubly charged state by impact with the plasma electrons and separated from the primaries due to the confining magnetic field of the plasma device. The resulting secondary ions are collected outside the plasma. The plasma parameters that can be measured by the HIBD are: the plasma electron density and temperature, and the electric and magnetic potentials. On the small tokamak ISTTOK (R = 0.46 m, a = 0.085 m, B = 0.5 T, Ip = 4…6 kA, = 5 × 10¹⁸ m ⁻³ , Te = 120 eV), the HIBD is based on a 20 keV Xe⁺ (or Cs⁺ ) beam injector and a multiple cell array detector (MCAD) collecting a fan of secondary Xe²⁺ (or Cs²⁺) ions emerging from the plasma along the primary beam trajectory. This paper describes the recent developments and improvements in the ISTTOK HIBD secondary beam detection. The capabilities of new detection system are illustrated by recent results of ISTTOK plasma MHD activity and electrode biasing studies. The on going developments of the multichannel multi-slit 90o cylindrical energy analyzer for the plasma potential and its fluctuations measurements and a novel approach of the HIBD use in real-time vertical plasma position control are also considered. Диагностика пучком тяжёлых ионов (ДПТИ) является мощным инструментом в исследованиях горячей плазмы в термоядерных установках с магнитным удержанием. Инжектируемый в плазму первичный пучок однозарядных положительных ионов ионизируется в двухзарядное состояние в столкновениях с электронами плазмы. В магнитном поле плазменной установки результирующие вторичные ионы отделяются от первичного пучка и детектируются вне плазмы. Измеряемые ДПТИ параметры плазмы включают плотность, температуру электронов, электрический и магнитный потенциалы. На малом токамаке ISTTOK (R = 0,46 м, а = 0,085 м, В = 0,5 Тл, Ip = 4…6 кА, = 5 × 10¹⁸ м ⁻³, Te = 120 эВ) ДПТИ состоит из 20 кэВ инжектора Xe ⁺ (или Cs⁺) пучка и мультиколлекторного детектора (МКД) вторичных Хе²⁺ (или Cs²⁺ионов, выходящих из плазмы вдоль траектории первичного пучка. Описываются изменения и улучшения детекторной системы ДПТИ на токамаке ISTTOK. Возможности новой детекторной системы иллюстрируются недавними результатами исследований МГД-активности и поляризации плазмы. Рассматриваются также разработка многоканального мультищелевого 90o цилиндрического анализатора энергии для измерений потенциала плазмы и его флуктуаций и новый подход использования ДПТИ для контроля вертикального положения плазмы в режиме реального времени. Діагностика пучком важких іонів (ДПВІ) є потужним інструментом у дослідженнях гарячої плазми в термоядерних установках з магнітним утриманням. Iнжектований в плазму первинний пучок однозарядних позитивних іонів іонізується в двозарядний стан у зіткненнях з електронами плазми. У магнітному полі плазмової установки результуючі вторинні іони відокремлюються від первинного пучка і фіксуються поза плазми. Вимірювані ДПВІ параметри плазми включають щільність, температуру електронів, електричний і магнітний потенціали. На малому токамацi ISTTOK (R = 0,46 м, а = 0,085 м, В = 0,5 Тл, Ip = 4…6 кА, = 5×10¹⁸ м ⁻³, Te = 120 еВ) ДПВІ складається з 20 кеВ інжектора Xe+ (або Cs+ ) пучка і мультиколекторного детектора (МКД) вторинних Хе²⁺ (або Cs²⁺) іонів, які виходять з плазми уздовж траєкторії первинного пучка. Описуються зміни і поліпшення детекторной системи ДПВІ на токамацi ISTTOK. Можливості нової детекторної системи ілюструються недавніми результатами досліджень МГД-активності і поляризації плазми. Розглядаються також розробка багатоканального мультищілинного 90o циліндричного аналізатора енергії для вимірювань потенціалу плазми та його флуктуацій і новий підхід використання ДПВІ для контролю вертикального положення плазми в режимі реального часу 2016 Article Recent developments in the ISTTOK heavy ion beam diagnostic / I.S. Nedzelskiy, A. Malaquias, R.B. Henriques, R. Sharma // Вопросы атомной науки и техники. — 2016. — № 6. — С. 297-301. — Бібліогр.: 9 назв. — англ. 1562-6016 PACS: 52.55.Fa, 52.70.-m http://dspace.nbuv.gov.ua/handle/123456789/115467 en Вопросы атомной науки и техники 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 Nedzelskiy, I.S. Malaquias, A. Henriques, R.B. Sharma, R. Recent developments in the ISTTOK heavy ion beam diagnostic Вопросы атомной науки и техники |
| description |
The heavy ion beam diagnostic (HIBD) presents a powerful tool for investigations of hot plasmas in thermonuclear devices with magnetic confinement. When injected into the plasma, the primary probing beam of singly charged positive ions is ionized to a doubly charged state by impact with the plasma electrons and separated from the primaries due to the confining magnetic field of the plasma device. The resulting secondary ions are collected outside the plasma. The plasma parameters that can be measured by the HIBD are: the plasma electron density and temperature, and the electric and magnetic potentials. On the small tokamak ISTTOK (R = 0.46 m, a = 0.085 m, B = 0.5 T, Ip = 4…6 kA, = 5 × 10¹⁸ m ⁻³ , Te = 120 eV), the HIBD is based on a 20 keV Xe⁺ (or Cs⁺ ) beam injector and a multiple cell array detector (MCAD) collecting a fan of secondary Xe²⁺ (or Cs²⁺) ions emerging from the plasma along the primary beam trajectory. This paper describes the recent developments and improvements in the ISTTOK HIBD secondary beam detection. The capabilities of new detection system are illustrated by recent results of ISTTOK plasma MHD activity and electrode biasing studies. The on going developments of the multichannel multi-slit 90o cylindrical energy analyzer for the plasma potential and its fluctuations measurements and a novel approach of the HIBD use in real-time vertical plasma position control are also considered. |
| format |
Article |
| author |
Nedzelskiy, I.S. Malaquias, A. Henriques, R.B. Sharma, R. |
| author_facet |
Nedzelskiy, I.S. Malaquias, A. Henriques, R.B. Sharma, R. |
| author_sort |
Nedzelskiy, I.S. |
| title |
Recent developments in the ISTTOK heavy ion beam diagnostic |
| title_short |
Recent developments in the ISTTOK heavy ion beam diagnostic |
| title_full |
Recent developments in the ISTTOK heavy ion beam diagnostic |
| title_fullStr |
Recent developments in the ISTTOK heavy ion beam diagnostic |
| title_full_unstemmed |
Recent developments in the ISTTOK heavy ion beam diagnostic |
| title_sort |
recent developments in the isttok heavy ion beam diagnostic |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2016 |
| topic_facet |
Plasma diagnostics |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/115467 |
| citation_txt |
Recent developments in the ISTTOK heavy ion beam diagnostic / I.S. Nedzelskiy, A. Malaquias, R.B. Henriques, R. Sharma // Вопросы атомной науки и техники. — 2016. — № 6. — С. 297-301. — Бібліогр.: 9 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT nedzelskiyis recentdevelopmentsintheisttokheavyionbeamdiagnostic AT malaquiasa recentdevelopmentsintheisttokheavyionbeamdiagnostic AT henriquesrb recentdevelopmentsintheisttokheavyionbeamdiagnostic AT sharmar recentdevelopmentsintheisttokheavyionbeamdiagnostic |
| first_indexed |
2025-07-08T08:49:36Z |
| last_indexed |
2025-07-08T08:49:36Z |
| _version_ |
1837068010746019840 |
| fulltext |
ISSN 1562-6016. ВАНТ. 2016. №6(106)
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2016, № 6. Series: Plasma Physics (22), p. 297-301. 297
RECENT DEVELOPMENTS IN THE ISTTOK HEAVY ION BEAM
DIAGNOSTIC
I.S. Nedzelskiy, A. Malaquias, R.B. Henriques, R. Sharma
Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa,
Lisboa, Portugal
E-mail: igorz@ipfn.ist.utl.pt
The heavy ion beam diagnostic (HIBD) presents a powerful tool for investigations of hot plasmas in
thermonuclear devices with magnetic confinement. When injected into the plasma, the primary probing beam of
singly charged positive ions is ionized to a doubly charged state by impact with the plasma electrons and separated
from the primaries due to the confining magnetic field of the plasma device. The resulting secondary ions are
collected outside the plasma. The plasma parameters that can be measured by the HIBD are: the plasma electron
density and temperature, and the electric and magnetic potentials. On the small tokamak ISTTOK (R = 0.46 m,
a = 0.085 m, B = 0.5 T, Ip = 4…6 kA, <ne> = 5 × 10
18
m
−3
, Te = 120 eV), the HIBD is based on a 20 keV Xe
+
(or
Cs
+
) beam injector and a multiple cell array detector (MCAD) collecting a fan of secondary Xe
2+
(or Cs
2+
) ions
emerging from the plasma along the primary beam trajectory. This paper describes the recent developments and
improvements in the ISTTOK HIBD secondary beam detection. The capabilities of new detection system are
illustrated by recent results of ISTTOK plasma MHD activity and electrode biasing studies. The on going
developments of the multichannel multi-slit 90
o
cylindrical energy analyzer for the plasma potential and its
fluctuations measurements and a novel approach of the HIBD use in real-time vertical plasma position control are
also considered.
PACS: 52.55.Fa, 52.70.-m
INTRODUCTION
The heavy ion beam diagnostic (HIBD) has been a
subject of study in fusion plasma diagnostics for about
fifty years since the pioneering work of the HIBD
inventors F. Jobes and R. Hickok on the ST tokamak
[1]. The HIBP principle is rather simple and explained
by Fig. 1.
Fig. 1. HIBD principle
A beam of single charged ions (primary ions) is injected
into the plasma across the confined magnetic field. The
ions of double charge state (secondary ions) are created
in collisions with plasma electrons and, after separation
from the primary beam due to magnetic field, are
collected outside the plasma. For a fixed single point
detector the position of ionization point (sample
volume) can be effectively moved with changing of
beam injection angle and/or energy. Alternatively, the
fan of secondary ions emerging from primary beam
along the fixed trajectory crossing the plasma can be
collected by a multiple cell detector. In such detection
scheme a number of sample volumes are recorded
simultaneously which is essential in investigation of the
plasma parameters fluctuations.
The intensity of the secondary beam relates to the
plasma parameters as:
Is = 2IpFplFs1eff(Te)lsvne(rsv),
where Ip is the intensity of the primary beam, Fpl and Fs1
are the primary and secondary beam exponential
attenuation factors, eff(Te) is the effective ionization
cross-section (function of the plasma electron
temperature), lsv is the sample volume dimension, and
ne(rsv) is the average over the sample volume plasma
electron density. This relation is the basis for the plasma
electron density and temperature measurements. On the
other hand, the energy of the secondary ion at the
ionization point is changed exactly as the local plasma
potential value, thus allowing for the measurements of
that important plasma parameter. Also, the HIBP
capability to retrieve plasma current profile from the
measurements of secondary beam shift due to the
plasma current magnetic field should be mentioned.
Fig. 2. Schematic of HIBD on the tokamak ISTTOK
298 ISSN 1562-6016. ВАНТ. 2016. №6(106)
The HIBD on the small tokamak ISTTOK (R = 0.46 m, a
= 0.085 m, B = 0.5 T, Ip = 4-6 kA, <ne> = 5 × 10
18
m
−3
,
Te = 120 eV) is based on the 20 keV Xe
+
(or Cs
+
) beam
injector (operating with plasma ion source [2]) and a
multiple cell array detector (MCAD) collecting a fan of
secondary Xe
2+
(or Cs
2+
) ions emerging from the plasma
along the primary beam trajectory as sketched in Fig. 2.
The MCAD (the picture also shown in Fig. 2) basically
presents a flat matrix of a number of collector cells [3].
With such very simple MCAD, the profiles of plasma
electron density and temperature were measured in early
experiments with HIBD on the ISTTOK [4]. Also, the
plasma current profile evolution was obtained from the
measurements of toroidal shifts of the secondary ions
[5].
1. RECENT DEVELOPMENTS AND
ILLUSTRATIVE RESULTS
When studying the turbulent characteristic of the
plasma, a high gain, wide bandwidth and low noise
detectors and amplifiers are required. Recent
developments and improvements of the ISTTOK HIBD
secondary beam detection allow for the increase of the
detector signal-to-noise ratio and amplifiers bandwidth,
thus improving the overall performance of the HIBD
operation and quality of the obtained data.
1.1. MCAD AND ELECTRONICS
Measurements with MCAD are efficient in a close to
the plasma arrangement of the detector, operating
therefore in strong radiation environment (mainly UV),
that can result in spurious background signal from the
cells due to electron emission effect.
To achieve an effective shielding from emitted
electrons, in the new MCAD design the cells are not
flat, but consist of two similar geometry /L-like shaped
copper plates combined together as shown in Fig. 3.
Fig. 3. Sketch and picture of new MCAD
In such configuration, the cell presents an effectively
Faraday cup-like structure 10 mm of deepness. 12 cells
are individually attached in a column stack fixed on
insulator plate and then painted by colloidal graphite to
reduce the electron emission yield. The stack is shielded
by a copper plate baffle arrangement with opening face
(1260 mm) to the plasma. In this new version of the
MCAD the bottom L-plates of the cells are opened for
the secondary ions and plasma radiation. Contrary, the
top -plates of the cells are almost completely shielded
from the secondary ions and can be biased to suppress
the secondary electrons and photo-electrons created on
the bottom plates. Fig. 4 illustrates the efficiency of the
modified MCAD on an example of the square-wave
chopped secondary ions signal obtained on one MCAD
cell in two plasma shots without and with cell biasing at
-3 V.
Fig. 4. Signal from one cell without and with biasing
Complete suppression of the plasma background signal
is achieved.
The HIBD signal conditioning system has been
improved with elaborated small size and low cost
transimpedance two stages amplifiers with gain of
210
7
V∕A, 0.5 nA, rms of noise and 400 kHz
bandwidth. The whole amplification system consists of
up to 50 amplifier modules connected side by side in
several layers, Fig. 5,a. One side is connected directly to
the tokamak diagnostic port flange with two D25
connectors. The amplification system is powered by
batteries and shielded with Mu-metal box to reduce the
electromagnetic induced noise, Fig. 5,b. Signals,
coming from the amplifiers, are digitized at 2 MHz
sampling rate and stored by the ISTTOK data
acquisition system.
Fig. 5. Pictures of amplification system
The improved detection system results in 3 time
increase of the signal-to-noise ratio.
1.2. STUDY OF MHD ACTIVITY [7]
The results presented in this subsection have been
obtained in the ISTTOK discharges with BT = 0.45 T, Ip
= 6 kA, and <ne> = 4 × 10
18
m
−3
, characterized by
repetitive bursts of MHD activity and density drops. It
should be noted that the core electron temperature in the
ISTTOK is not high, ~120 eV, meaning that the HIBD
signal amplitude and profile is not only determined by
the plasma electron density value and profile, but also
by the value and profile of the electron temperature (via
1,2(Te)). Therefore, for ISTTOK plasmas it is more
correct to speak about measurements of the ne1,2(Te)
product profile, which may be considered as a proxy of
the plasma pressure.
Fig. 6 shows the combined view of the ne1,2(Te)
profile, the signals from the Mirnov coil, and the line
integrated density during the MHD event. The Mirnov
coil signal indicates a violent and unstable growing
a b
ISSN 1562-6016. ВАНТ. 2016. №6(106) 299
before the crash. The ne1,2(Te) profile starts to
fluctuate mainly in the plasma core with growing
amplitude up to 30 % of the absolute value, correlating
with the MHD fluctuations. After the crash (from
113.08 ms) the MHD activity and fluctuations in the
ne1,2(Te) profile are significantly reduced and the
plasma remains in a “quiescent” state during some
time.
Fig. 6. ne1,2(Te) profile, Mirnov coil signal, and the line
integrated density during the MHD event
Fig. 7 presents a detail view of ne1,2(Te) radial profile
during the MHD event (112.8…113.2 ms) indicating
the transition from a peaked to flat profile. However,
the integrated value of ne1,2(Te) remains the same
(<2% of variation) before and after the crash, while the
line integrated density signal drops on 40% (as
measured by interferometer). The observed property
can be due to above mentioned combined response of
the ne1,2(Te) product on variations in ne and Te.
Fig. 7. ne1,2(Te) radial profile during MHD event
As the effective detector line of ISTTOK HIBD
intersects plasma almost by strait line crossing the
plasma axis (see Fig. 1), it presents an interest to search
and identify a tearing mode (TM) structure by the phase
reversal of the respective fluctuations between two
neighboring cells.
Such a signature have been observed in the ISTTOK
discharge with slow ramp-up plasma current (4…7 kA
in 18 ms) as shown in Fig. 8 for filtered HIBD signals at
the dominant MHD frequency (50…70 kHz) of m=4
mode.
Fig. 8. Signals from MCAD cells
A clear phase reversal between two successive cells
(marked by dashed lines) is observed, indicating the
rational flux surface location at r ∼ ± 2 cm.
1.3. ELECTRODE BIASING EXPERIMENTS
Edge plasma biasing experiments have been
performed on many tokamaks demonstrating a clear
correlation between the E×B flow shear velocity and
turbulence control [8]. In ISTTOK, the plasma
fluctuations can be measured in the whole minor radius
using the HIBD (core and inner edge) and LPs (edge)
diagnostics together, that present a special interest as the
link between plasma core and edge can be studied.
Typically, to maximize the improvement in
confinement, a movable graphite electrode is located
2…2.5 cm inside the last closed flux surface and biased
at +80 V. Improved confinement regimes in ISTTOK
are characterized by an averaged plasma density <ne>
increase, Hα radiation decrease, edge turbulent transport
decrease as shown in Fig. 9.
Fig. 9. <ne>, Hα, EB current, ETT during biasing
Fig. 10 presents the neσeff(Te) and ion saturation current
Isat profiles during normal and improved confinement
phases. During EB, the neσeff(Te) profile is peaked,
while Isat flattened.
Fig. 10. neσeff(Te) and Isat profiles during biasing
The evolution of the turbulent transport and the
neσeff(Te) profile during a full EB cycle is shown in
Fig. 11. Just after EB transitions (solid vertical lines) the
transport is modified within the turbulence characteristic
time of ~10 μs. The neσeff(Te) profile major changes,
indicated by the dashed lines in Fig. 11, only happen
after ~150 μs, corresponding to the particle confinement
time. It is also observed that the neσeff(Te) profile reaches
its maximum about 1ms after the EB is applied.
Fig. 11. Turbulent transport and the neσeff(Te) profile
during EB
300 ISSN 1562-6016. ВАНТ. 2016. №6(106)
During non EB, HIBD peripheral signals are usually
dominated by MHD activity fluctuations (confirmed by
Mirnov coils signal). When EB is applied, the MHD
activity strongly decreases on both peripheral HIBD
channels and Mirnov coils as illustrated in Fig. 12. It is
also observed an increase of fluctuations in the central
HIBD channels the nature of which is a matter for future
research.
Fig. 12. Spectrogram of MCAD and one MC signals
during EB
2. ON GOING DEVELOPMENTS
2.1. 90
o
CYLINDRICAL ENERGY ANALYZER
In order to extend the capabilities of MCAD to
measure the plasma potential and its fluctuations in the
E/E < 10
-3
range, a multiple-channel multi-slit 90
o
cylindrical energy analyzer (CEA) has been proposed,
Fig. 13. The main advantage of the considered 90
o
CEA
is compactness to suit the geometric constraints of
experimental conditions on ISTTOK.
The SIMION code has been applied to minimize the
angular aberration and to increase the energy resolution
beyond the ideal, implementing an approach to take
advantage of the strong lensing properties of fringing
fields [9] and deceleration inside CEA.
Fig. 13. 90
o
cylindrical energy analyzer
The best results have been obtained for the initially
inclined (in = -5
o
) double charged (q = 2) beam
entering the CEA entrance slit slightly below the
centerline R0 (lshift = -2 mm), decelerated from 20 keV to
4 keV passing through the lens formed by fringing field
between entrance slit (Ven = 0 kV) and CEA plates (Vp =
8.4 kV, Vn = 7.6 kV) and collected on exit electrode
kept at Vex = 8 kV. Fig. 14 illustrates visually the energy
dispersion (E0 = 19.7, 20, 20.3 keV, in = -5
o
, Fig. 14,a),
focusing (in = -7
o
, -5
o
, -3
o
, E0 = 20 keV, Fig. 14, b) and
the magnification (wb0 = 2.5 mm, Fig. 14,c) properties
of the considered 90
o
CEA and Gaussian beam.
Fig. 14. SIMION results for 90
o
CEA
Fig. 15. Resolution property of 90
o
CEA
Finally, Fig. 15 presents a visual representation of two
Gaussian beams wb0 =1.5 mm of width and = ±0.5
o
of divergence differed in energy on 20 V (20 keV top
and 20.02 keV bottom). From the figure, the results of
numerical simulations of real 90
o
CEA predicts the
energy resolution of E/E = 3×10
-4
, that is in the range
of plasma potential fluctuations. Also, sufficient
decrease of the angular aberration in the range of
= ± 2
o
is demonstrated. Recalculated to the energy,
the residual angle aberration is equivalent to E/E =
8.5×10
-5
of energy change for = ± 0.5
o
of expected
misalignment and beam divergence ranges.
2.2. REAL-TIME VERTICAL PLASMA POSITION
CONTROL
Successful operation of the tokamak relies on the
real-time control of plasma position. Such control
consists on the measurement, data processing and
actuation within an appropriate time window. In the
ISTTOK the plasma position is controlled by magnetic
fields generated on external coils. The current flowing
into the coils is real-time controlled using the ISTTOK
control system having a control cycle of 100 μs during
which it reads all the plasma position-related
diagnostics (Mirnov coils, Langmuir probes) connected
to the Advanced Telecommunications Computing
Architecture (ATCA) digitizers and sends the control
reference to the ISTTOK actuators. The HIBD measures
locally and simultaneously the neσeff (Te) product at 12
sample volumes vertically distributed along the plasma
region of -0.06 m < r < 0.06 m. Since the plasma
equilibrium is related with the plasma pressure and the
neσeff (Te) product may be considered as a proxy for the
plasma pressure, it is expected that the neσeff (Te) will
give more accurate measurements for the plasma
position than the currently used diagnostics. A high
signal-to-noise ratio of the vertical plasma position
measurement is achieved by high, 150 kHz, frequency
modulation (chopping) of the primary beam to
discriminate the beam signal from the background
noise. Providing one profile per chopping period it is
a b
ISSN 1562-6016. ВАНТ. 2016. №6(106) 301
possible to obtain up to 15 neσeff(Te) profiles in one real-
time cycle of 100 s. This work is in the initial stage.
SUMMARY AND FUTURE PLANS
The new MCAD of ISTTOK HIBD is characterized
by complete suppression of the plasma background. The
improved signal conditioning electronics has high gain,
210
7
V∕A, low noise <0.5 nA, and high, up to 400 kHz,
bandwidth. These improvements allow for detailed
study of the plasma MHD activity and the electrode
biasing regimes. Except continuation of the work in
these areas, the investigations of plasma turbulence and
geodesic acoustic mode (GAM) activity are considered
in the nearest plans. The implementation of the
multichannel multi-slit 90
o
cylindrical energy analyzer
will increase the ISTTOK HIBD performance to
measure the plasma potential and its fluctuations. It is
important that in simultaneous use of HIBD and LPs,
the fluctuations can be measured across the whole
plasma cross-section. Also, the work of HIBD use in
real-time vertical plasma position control will be
continued.
ACKNOWLEDGEMENTS
IPFN activities received financial support from
”Fundação para a Ciência e Tecnologia” through project
UID/FIS/50010/2013.
REFERENCES
1. F.C. Jobes, R. L. Hickok // Nucl. Fusion. 1970, v. 10,
p. 195.
2. J.A.C. Cabral et al. // Plasma Source Sci. Technol.
1994, v. 3, p. 1.
3. J.A.C. Cabral, A. Malaquias, A. Praxedes, W. Van
Toledo, C.A.F. Varandas // IEEE Transactions on
Plasma Science. 1994, v. 22(4), p. 350.
4. A. Malaquias, I.S. Nedzelskii, C.A.F. Varandas,
J.A.C. Cabral // Review of Scientific Instruments. 1999,
v. 70(1), p. J947.
5. A. Malaquias, J.A.C. Cabral, C.A.F. Varandas, and
R. Canário // Fusion Engineering and Design. 1997,
v. 34-35, p. 671.
6. R.B. Henriques, I.S. Nedzelskiy, A. Malaquias,
H. Fernandes // Rev. Sci. Instrum. 2012, v. 83,
p. 10D705.
7. R.B. Henriques, A. Malaquias, I.S. Nedzelskiy,
C. Silva, R. Coelho, H. Figueiredo, H. Fernandes // Rev.
Sci. Instrum. 2014, v. 85, p. 11D848.
8. G. Van Oost et al. // Plasma Phys. Control. Fusion
2003, v. 45, p. 621.
9. E.P. Benis, T.J.M. Zouros // Nucl. Instrum. and Meth.
in Phys. Res. Sec. A. 2000, v. 440(2), p. 462.
Article received 19.09.2016
СОВРЕМЕННОЕ СОСТОЯНИЕ ДИАГНОСТИКИ ПЛАЗМЫ ПУЧКА ТЯЖËЛЫХ ИОНОВ
НА ТОКАМАКЕ ISTTOK
И.С. Недзельский, А. Малакиаш, Р.Б. Энрикеш, Р. Шарма
Диагностика пучком тяжёлых ионов (ДПТИ) является мощным инструментом в исследованиях горячей
плазмы в термоядерных установках с магнитным удержанием. Инжектируемый в плазму первичный пучок
однозарядных положительных ионов ионизируется в двухзарядное состояние в столкновениях с
электронами плазмы. В магнитном поле плазменной установки результирующие вторичные ионы
отделяются от первичного пучка и детектируются вне плазмы. Измеряемые ДПТИ параметры плазмы
включают плотность, температуру электронов, электрический и магнитный потенциалы. На малом токамаке
ISTTOK (R = 0,46 м, а = 0,085 м, В = 0,5 Тл, Ip = 4…6 кА, <nе> = 5 × 10
18
м
-3
, Te = 120 эВ) ДПТИ состоит из
20 кэВ инжектора Xe
+
(или Cs
+
) пучка и мультиколлекторного детектора (МКД) вторичных Хе
2+
(или Cs
2 +
)
ионов, выходящих из плазмы вдоль траектории первичного пучка. Описываются изменения и улучшения
детекторной системы ДПТИ на токамаке ISTTOK. Возможности новой детекторной системы
иллюстрируются недавними результатами исследований МГД-активности и поляризации плазмы.
Рассматриваются также разработка многоканального мультищелевого 90
o
цилиндрического анализатора
энергии для измерений потенциала плазмы и его флуктуаций и новый подход использования ДПТИ для
контроля вертикального положения плазмы в режиме реального времени.
СУЧАСНИЙ СТАН ДІАГНОСТИКИ ПЛАЗМИ ПУЧКА ВАЖКИХ ІОНІВ НА ТОКАМАЦI ISTTOK
І.С. Недзельський, А. Малакіаш, Р.Б. Енрікеш, Р. Шарма
Діагностика пучком важких іонів (ДПВІ) є потужним інструментом у дослідженнях гарячої плазми в
термоядерних установках з магнітним утриманням. Iнжектований в плазму первинний пучок однозарядних
позитивних іонів іонізується в двозарядний стан у зіткненнях з електронами плазми. У магнітному полі
плазмової установки результуючі вторинні іони відокремлюються від первинного пучка і фіксуються поза
плазми. Вимірювані ДПВІ параметри плазми включають щільність, температуру електронів, електричний і
магнітний потенціали. На малому токамацi ISTTOK (R = 0,46 м, а = 0,085 м, В = 0,5 Тл, Ip = 4…6 кА, <nе> =
5×10
18
м
-3
, Te = 120 еВ) ДПВІ складається з 20 кеВ інжектора Xe
+
(або Cs
+
) пучка і мультиколекторного
детектора (МКД) вторинних Хе
2+
(або Cs
2+
) іонів, які виходять з плазми уздовж траєкторії первинного пучка.
Описуються зміни і поліпшення детекторной системи ДПВІ на токамацi ISTTOK. Можливості нової
детекторної системи ілюструються недавніми результатами досліджень МГД-активності і поляризації
плазми. Розглядаються також розробка багатоканального мультищілинного 90
o
циліндричного аналізатора
енергії для вимірювань потенціалу плазми та його флуктуацій і новий підхід використання ДПВІ для
контролю вертикального положення плазми в режимі реального часу.
|