Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron
Under conditions of spontaneous change of plasma confinement state having been observed recently in the U-3M torsatron with a natural helical divertor, it is shown that at the initial phase of this change all the components of the diverted plasma flow (DPF) decrease, while thermal (TI) and suprather...
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| Cite this: | Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron / V.V. Chechkin, E.L. Sorokovoy, L.I. Grigor’eva, A.S. Slavnyj, Ye.L. Sorokovoy, E.D. Volkov, N.I. Nazarov, P.Ya. Burchenko, S.A. Tsybenko, A.V. Lozin, A.Ye. Kulaga, A.P. Litvinov, Yu.K. Mironov, V.S. Romanov, S. Masuzaki, K. Yamazaki // Вопросы атомной науки и техники. — 2005. — № 2. — С. 3-7. — Бібліогр.: 7 назв. — англ. |
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Chechkin, V.V. Sorokovoy, E.L. Grigor’eva, L.I. Slavnyj, A.S. Sorokovoy, Ye.L. Volkov, E.D. Nazarov, N.I. Burchenko, P.Ya. Tsybenko, S.A. Lozin, A.V. Kulaga, A.Ye. Litvinov, A.P. Mironov, Yu.K. Romanov, V.S. Masuzaki, S. Yamazaki, K. 2015-03-31T07:39:41Z 2015-03-31T07:39:41Z 2005 Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron / V.V. Chechkin, E.L. Sorokovoy, L.I. Grigor’eva, A.S. Slavnyj, Ye.L. Sorokovoy, E.D. Volkov, N.I. Nazarov, P.Ya. Burchenko, S.A. Tsybenko, A.V. Lozin, A.Ye. Kulaga, A.P. Litvinov, Yu.K. Mironov, V.S. Romanov, S. Masuzaki, K. Yamazaki // Вопросы атомной науки и техники. — 2005. — № 2. — С. 3-7. — Бібліогр.: 7 назв. — англ. 1562-6016 PACS: 52.55.Dy; 52.55.He; 52.55.Rk https://nasplib.isofts.kiev.ua/handle/123456789/79308 Under conditions of spontaneous change of plasma confinement state having been observed recently in the U-3M torsatron with a natural helical divertor, it is shown that at the initial phase of this change all the components of the diverted plasma flow (DPF) decrease, while thermal (TI) and suprathermal (STI) ion content in the bulk plasma increases and the TI+STI fraction in the DPF is reduced on the ion В×∇В drift side, thus indicating an improvement of ion confinement. The initial phase is ended by a DPF rise on the ion В×∇В drift side, a TI+STI content decay in the bulk plasma and a rise of TI+STI outflow into the DPF, these being indications of an ion confinement deterioration. However, a simultaneous DPF reduction on the electron В×∇В drift side and a rise of electron density and ECE indicate an improvement of electron confinement. В умовах виявленої раніше спонтанної зміни режиму утримання в торсатроні У-3М з природним гвинтовим дивертором показано, що на початковій стадії цієї зміни зменшуються всі складові плазмового диверторного потоку (ПДП), в той час, як зростає кількість теплових (ТІ) та надтеплових (НТІ) іонів в основній плазмі, засвідчуючи про покращення їх утримання. Початкова стадія завершується зростанням ПДП на боці іонного дрейфу В×∇В, зменшенням кількості ТІ та НТІ в основній плазмі та підвищеним виходом їх до ПДП, що є ознакою погіршення утримання іонів. Але одночасне зменшення ПДП на боці електронного дрейфу В×∇В і зростання електронної густини та електронного циклотронного випромінювання вказують на покращення утримання електронів. В условиях обнаруженного ранее спонтанного изменения режима удержания в торсатроне У-3М с естественным винтовым дивертором показано, что на начальной стадии этого изменения уменьшаются все составляющие плазменного диверторного потока (ПДП) и растёт содержание тепловых (ТИ) и сверхтепловых (СТИ) ионов в основной плазме, свидетельствуя об улучшении их удержания. Начальная стадия завершается возрастанием ПДП на стороне ионного дрейфа В×∇В, уменьшением содержания ТИ и СТИ в основной плазме и повышенным их уходом в ПДП, что говорит об ухудшении удержания ионов. Однако, при этом уменьшается ПДП на стороне электронного дрейфа В×∇В и растут плотность электронов и электронное циклотронное излучение, что указывает на улучшение удержания электронов. This work was carried out in collaboration with National Institute for Fusion Science (Toki, Japan) after the LIME Program. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Magnetic confinement Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron Поведінка диверторного потоку та втрат частинок при спонтанній зміні стану утримання плазми в торсатроні “УРАГАН-3М” Поведение диверторного потока и потерь частиц при спонтанном изменении состояния удержания плазмы в торсатроне «УРАГАН-3М» Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron |
| spellingShingle |
Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron Chechkin, V.V. Sorokovoy, E.L. Grigor’eva, L.I. Slavnyj, A.S. Sorokovoy, Ye.L. Volkov, E.D. Nazarov, N.I. Burchenko, P.Ya. Tsybenko, S.A. Lozin, A.V. Kulaga, A.Ye. Litvinov, A.P. Mironov, Yu.K. Romanov, V.S. Masuzaki, S. Yamazaki, K. Magnetic confinement |
| title_short |
Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron |
| title_full |
Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron |
| title_fullStr |
Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron |
| title_full_unstemmed |
Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron |
| title_sort |
divertor flow and particle loss behaviors in spontaneous change of confinement state in the uragan-3m torsatron |
| author |
Chechkin, V.V. Sorokovoy, E.L. Grigor’eva, L.I. Slavnyj, A.S. Sorokovoy, Ye.L. Volkov, E.D. Nazarov, N.I. Burchenko, P.Ya. Tsybenko, S.A. Lozin, A.V. Kulaga, A.Ye. Litvinov, A.P. Mironov, Yu.K. Romanov, V.S. Masuzaki, S. Yamazaki, K. |
| author_facet |
Chechkin, V.V. Sorokovoy, E.L. Grigor’eva, L.I. Slavnyj, A.S. Sorokovoy, Ye.L. Volkov, E.D. Nazarov, N.I. Burchenko, P.Ya. Tsybenko, S.A. Lozin, A.V. Kulaga, A.Ye. Litvinov, A.P. Mironov, Yu.K. Romanov, V.S. Masuzaki, S. Yamazaki, K. |
| topic |
Magnetic confinement |
| topic_facet |
Magnetic confinement |
| publishDate |
2005 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Поведінка диверторного потоку та втрат частинок при спонтанній зміні стану утримання плазми в торсатроні “УРАГАН-3М” Поведение диверторного потока и потерь частиц при спонтанном изменении состояния удержания плазмы в торсатроне «УРАГАН-3М» |
| description |
Under conditions of spontaneous change of plasma confinement state having been observed recently in the U-3M torsatron with a natural helical divertor, it is shown that at the initial phase of this change all the components of the diverted plasma flow (DPF) decrease, while thermal (TI) and suprathermal (STI) ion content in the bulk plasma increases and the TI+STI fraction in the DPF is reduced on the ion В×∇В drift side, thus indicating an improvement of ion confinement. The initial phase is ended by a DPF rise on the ion В×∇В drift side, a TI+STI content decay in the bulk plasma and a rise of TI+STI outflow into the DPF, these being indications of an ion confinement deterioration. However, a simultaneous DPF reduction on the electron В×∇В drift side and a rise of electron density and ECE indicate an improvement of electron confinement.
В умовах виявленої раніше спонтанної зміни режиму утримання в торсатроні У-3М з природним гвинтовим дивертором показано, що на початковій стадії цієї зміни зменшуються всі складові плазмового диверторного потоку (ПДП), в той час, як зростає кількість теплових (ТІ) та надтеплових (НТІ) іонів в основній плазмі, засвідчуючи про покращення їх утримання. Початкова стадія завершується зростанням ПДП на боці іонного дрейфу В×∇В, зменшенням кількості ТІ та НТІ в основній плазмі та підвищеним виходом їх до ПДП, що є ознакою погіршення утримання іонів. Але одночасне зменшення ПДП на боці електронного дрейфу В×∇В і зростання електронної густини та електронного циклотронного випромінювання вказують на покращення утримання електронів.
В условиях обнаруженного ранее спонтанного изменения режима удержания в торсатроне У-3М с естественным винтовым дивертором показано, что на начальной стадии этого изменения уменьшаются все составляющие плазменного диверторного потока (ПДП) и растёт содержание тепловых (ТИ) и сверхтепловых (СТИ) ионов в основной плазме, свидетельствуя об улучшении их удержания. Начальная стадия завершается возрастанием ПДП на стороне ионного дрейфа В×∇В, уменьшением содержания ТИ и СТИ в основной плазме и повышенным их уходом в ПДП, что говорит об ухудшении удержания ионов. Однако, при этом уменьшается ПДП на стороне электронного дрейфа В×∇В и растут плотность электронов и электронное циклотронное излучение, что указывает на улучшение удержания электронов.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/79308 |
| citation_txt |
Divertor flow and particle loss behaviors in spontaneous change of confinement state in the URAGAN-3M torsatron / V.V. Chechkin, E.L. Sorokovoy, L.I. Grigor’eva, A.S. Slavnyj, Ye.L. Sorokovoy, E.D. Volkov, N.I. Nazarov, P.Ya. Burchenko, S.A. Tsybenko, A.V. Lozin, A.Ye. Kulaga, A.P. Litvinov, Yu.K. Mironov, V.S. Romanov, S. Masuzaki, K. Yamazaki // Вопросы атомной науки и техники. — 2005. — № 2. — С. 3-7. — Бібліогр.: 7 назв. — англ. |
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MAGNETIC CONFINEMENT
DIVERTOR FLOW AND PARTICLE LOSS BEHAVIORS IN
SPONTANEOUS CHANGE OF CONFINEMENT STATE
IN THE URAGAN-3M TORSATRON
V.V. Chechkin, E.L. Sorokovoy, L.I. Grigor’eva, A.S. Slavnyj, Ye.L. Sorokovoy,
E.D. Volkov, N.I. Nazarov, P.Ya. Burchenko, S.A. Tsybenko, A.V. Lozin, A.Ye. Kulaga,
A.P. Litvinov, Yu.K. Mironov, V.S. Romanov, S. Masuzaki∗, K. Yamazaki∗
Institute of Plasma Physics, NSC KIPT, Kharkov, Ukraine;
∗National Institute for Fusion Science, Toki, Gifu 509-5292, Japan
Under conditions of spontaneous change of plasma confinement state having been observed recently in the U-3M
torsatron with a natural helical divertor, it is shown that at the initial phase of this change all the components of the
diverted plasma flow (DPF) decrease, while thermal (TI) and suprathermal (STI) ion content in the bulk plasma
increases and the TI+STI fraction in the DPF is reduced on the ion В×∇В drift side, thus indicating an improvement of
ion confinement. The initial phase is ended by a DPF rise on the ion В×∇В drift side, a TI+STI content decay in the
bulk plasma and a rise of TI+STI outflow into the DPF, these being indications of an ion confinement deterioration.
However, a simultaneous DPF reduction on the electron В×∇В drift side and a rise of electron density and ECE indicate
an improvement of electron confinement.
PACS: 52.55.Dy; 52.55.He; 52.55.Rk
1. INTRODUCTION
In the l = 3 Uragan-3M (U-3M) torsatron with a
natural helical divertor and a plasma produced and heated
by RF fields, spontaneous changes of electron
temperature and density, stored energy and other plasma
parameters occur, provided the heating power is high
enough [1,2]. Similar to tokamaks with an auxiliary
heating and some stellarator-type devices with NBI and
ECH [3], these effects are associated with transition to an
improved confinement state (hereafter, “transition”). In
U-3M the transition has been shown to occur due to
formation of an internal transport barrier near the τ =1/4
rational magnetic surface [2]. With this, a layer with signs
of an edge transport barrier has also been shown to form
near the plasma boundary [4].
It is natural to expect that the change of confinement
mode should affect diverted plasma characteristics. The
diverted plasma flow (DPF) in U-3M is distinct by a
vertical asymmetry of its distribution [5,6], where a
predominant part of the ambipolar plasma flow outflows
on the ion toroidal B×∇B drift side and ions predominate
in the corresponding non-ambipolar flow. These effects
have been related to the asymmetry of angular
distribution of direct (non-diffusive) ion loss with the
main contribution from suprathermal ions (STI) [5].
The main objective of this work is to find out the effect of
the change of confinement state in U-3M on the DPF
magnitude and the ion loss. The data having been
obtained allow one to estimate, at least qualitatively, the
ion loss contribution to the DPF magnitude and find out
the dynamics of ion confinement during the transition.
2. EXPERIMENTAL CONDITIONS
In the U-3M torsatron (l = 3, m = 9, Ro = 1m, a ≈
0.1m, ι ( a )/2π ≈ 0.3) the whole magnetic system is
enclosed into a large 5 m diameter vacuum chamber, so
that an open natural helical divertor is realized in this
device. The toroidal magnetic field, Bφ = 0.7 T, is
produced by the helical coils only, the ion toroidal drift B
×∇B is directed upward. A “currentless” plasma is
produced and heated by RF fields (ω ≈ ωсi). The RF
power deposited in the plasma is ~200 kW in the 30-50ms
pulse. The working gas (hydrogen) is admitted
continuously into the vacuum chamber at the pressure of
~10-5 Torr.
The electron temperature in the bulk plasma estimated
by intensity of 2nd harmonic ECE attains Te(0) ~ 500 eV.
The perpendicular ion energy distribution as determined
by a CX neutral mass-energy analyzer consists of two
temperature groups, Ti1 ~ 50 eV and Ti2 ~ 250-400 eV. As
previously [5,6], to detect the DPF (by the ion saturation
current, Is, and/or by the current to a grounded probe, Ip),
arrays of 1.25×0.8 cm2 plane Langmuir probes (“divertor
probe”, DP) are used. The probes are arranged poloidally
in the spacings between the helical coils beyond the X-
point (r = 27 cm) in two symmetric poloidal cross-
sections of the U-3M torus, φ = 00 (cross-section A-A,
Fig. 1(a)) and φ = 200 (D-D, Fig. 1(b)). The gap between
adjacent probes is 1 mm. The character of the energy
distribution of charge particles escaping to the divertor
region can be determined with the help of an array of 13
three-electrode retarding potential analyzers (“divertor
electrostatic analyzer“, DEA). The array is mounted
beyond the X-point in the top spacing of an A-A cross-
section nearest to that, where the DPs are installed
(Fig.1(a)).
3. POLOIDAL CROSS-SECTION А-А
A predominant fraction of the DPF in the cross-section
A-A (Fig. 1(a)) outflows to the top spacing (i.e., with the
ion В×∇В drift), along the divertor channel passing closer
to the major torus axis (“inner leg”, the Is maximum falls
at the DP N = 4). In Fig. 2 the time evolution is shown of
the line-averaged electron density, ne , (a) and some
other diverted and bulk plasma parameters of interest.
Problems of Atomic Science and Technology. Series: Plasma Physics (11). 2005. № 2. P. 3-7 3
a b
Fig. 1.
Disposition of
divertor probe
arrays and
retarding
potential
analyzers in
the poloidal
cross-sections
A-A (a) and
D-D (b),
showing the
helical coils I, II, III and the edge structure of magnetic field lines. The probes and analyzers in the top spacing of A-A
are numbered as N = 1-17 and 1-13, respectively; the probe numberings in the top and outboard spacings of D-D are
N = 1-9 and N = 1-23, respectively
Fig. 2. Time evolution of (a) line-averaged electron
density, ne , (b) ion saturation current Is to DP N = 4 in
the top spacing, (c) same to DP N = 1, (d) ion current to
the analyzer No. 5 at the retarding voltage U = 300 V, (e)
CX neutral flux,Γn, with the energy 1575 eV, (f) 2nd
harmonic ECE. Starting density ne1 ≈ 0.6×1018 m-3. The
vertical dashed line indicates the end of the initial phase
In the shot presented the transition starts at t ≈ 21 ms,
when the decaying density attains ne1 ≈ 0.6×1018 m-3
(“starting density”) and then retains around this level for
approximately 10 ms. At the beginning of this time
interval (“initial phase of transition”) a reduction to some
minimum value is observed of the DPF (as current Is to
the DP N = 4, Fig. 2(b); the current Is to DP N = 1 is also
shown in Fig. 2(c)) and the integral ion current Ii to a
DEA at the retarding voltage U = 300 V, i.e., including
thermal ions (TI, group Ti2) and STI (Fig. 2(d)). At the
same time, the flux of CX neutrals with the selected
energy 1575 eV, Γn, increases (Fig. 2(e)), thus indicating
a rise of STI content in the confinement volume.
Qualitatively similar to Fig. 2(b), the maximum values of
other DPF components in all the spacings of the A-A and
D-D cross-sections change at the initial phase. The time
behavior of Γn is kept qualitatively the same in the ~300-
2000 eV energy interval that includes both TI (group Ti2)
and STI. Accordingly, the ion temperature Ti2 increases
from 250 eV to ~400 eV at the initial phase (Fig. 3). At
the same time, the CX neutral flux with the selected
energy < 300 eV and the temperature Ti1 ≈ 50 eV do not
change substantially during the transition.
Fig. 3. Time evolution of ion temperatures Ti1 and Ti2 . In
the case in point, the Is minimum to the DP N = 4 occurs
at t ≈ 19 ms
It follows from Ii(U)/Ii(0) plots (Fig. 4) that the energy
distributions of the DPF ions do not differ strongly before
the transition (◊) and at the initial phase (□). With this,
only ~ 10% of the outflowing ions have the energy >
400eV comparable with the average energy of the group
Ti2 ions.
Thus, the DPF decrease on the ion B×∇B drift side
combined with the current Ii decrease in the divertor
region and the increase of the TI (group Ti2) and STI
content and of the ion temperature Ti2 at the initial phase
confirm an improvement of plasma confinement at least
4
0
100
200
300
400
500
0 10 20 30 40 50 60
Ti1
Ti2
time (ms)
io
n
te
m
pe
ra
tu
re
(
eV
)
for the account of ions (including STI) at this phase of
transition.
The time behavior of Is, Γn and Ii at the initial phase, its
duration being not more than several ms, is essentially
non-stationary. The Is decay is replaced by its rise,
beginning with t ≈ 25 ms (Fig. 2(b)). With the Is rise, a
step-like Ii rise (Fig. 2(d)) and a Γn decay (Fig. 2(e))
correlate, thus indicating a rise of both TI and STI loss
from the confinement volume. Also, the temperature Ti2
decreases (Fig. 3).
It follows from Fig. 4 that the fraction of > 400 eV
ions in the PDF attains ~ 40% at the end of the initial
phase (). Thus, the decrease of TI and STI content in
the confinement volume at the end of initial phase is
consistent with the rise of more energetic fraction in the
DPF. This means that the increase of DPF at the end of
initial phase at least partially is caused by a rise of TI and
STI loss.
Fig. 4. Ii(0)-normalized ion current Ii to the collector of
the analyzer No. 5 as a function of retarding voltage U:
, before the initial phase (t = 21 ms); , in the
minimum of Is at the initial phase (t = 25 ms); , after
the end of initial phase (t = 26 ms). ne1 ≈ 0.6×1018 m-3
An attention should be paid to the similarity in the
signal form between the current Is to the DP N = 1 in the
top spacing A-A (Fig. 2(c)) and the current Ii in Fig. 2(d).
This may indicate that the flows of escaping TI and STI
cross the boundary of the confinement region in the
process of their В×∇В drift, not following the
corresponding divertor magnetic channel.
The data similar to those shown in Figs 1,2 but taken
at a higher starting density, ne1 ≈ 1.3×1018 m-3, are
presented in Figs 5,6, respectively. Here, in contrast to the
lower ne1 case, the ion current to the DEA collector, Ii,
undergoes a step-like fall at the end of the initial phase
(Fig. 5(d)), and the ion energy distribution in Fig. 7 ()
stays nearly the same as before the transition (◊) and at the
initial phase (□). With this, the fraction of the > 400 eV ions
amounts only ~ 10% like before the transition and at the
initial phase in the lower density case (cf. Fig. 4). The
absence of consistency during the transition between the
time behaviors of the flux Γn with the selected particle
energy < 300 eV and the temperature Ti1, on the one hand
(unaffectedness of Γn and Ti1), and the current Ii of ions
with a relatively low energy (< 400 eV) in the PDF, on
the other hand (a step-like fall at the end of the initial
phase) makes one to suppose that such ions occur in the
DPF mainly outside the confinement region rather than
diffuse from it.
Fig. 5. Same as in Fig. 2 at the starting density ne1 ≈ 1.3
×1018 m-3. The Fig. 2(c) analogue is omitted
Thus, comparing Figs 5,6 with Figs 2,3, respectively,
we may suppose that the confinement improves around
the cross-section A-A as the density increases. At the
same time, it follows from Fig. 5(e) that the TI and STI
content in the confinement volume decreases similar to
the lower ne1 case (cf. Fig. 2(e)). Hence, we have to
suppose that the main TI and STI loss with a subsequent
outflow of these particles to the divertor region happens
in the sections of the helical magnetic field period
adjacent to the poloidal cross-section D-D. Since there are
no DEAs in the cross-section D-D, this supposition can be
verified only indirectly, e.g., by comparing the forms of Is
signals in D-D with those in A-A for the lower density
case, where an energetic ion outflow to the divertor has
been observed (Fig. 4).
Fig. 6. Same as in Fig. 4 for ne1 ≈ 1.3×1018 m-3
5
4. POLOIDAL CROSS-SECTION D-D
0
5
10
15
20
10 20 30 40 50 60 70
0
5
10
10 20 30 40 50 60 70
0
5
10
15
20
25
30
35
10 20 30 40 50 60 70
=7
time, ms
(a)
(b)
(d)
I
(m
A
)
(m
A
)
=16
=1
I
(m
A
)
s
s
I s
N
N
N
0
1
2
3
4
10 20 30 40 50 60 70
_ e
(c)
D-D
OUTBOARD
OUTBOARD
TOP
D-D
D-D
(over midplane)
(under midplane)
Fig. 7. Time behavior of (a) line-averaged electron
density, ne , (b) ion saturation current Is to DP N = 1 in
the top spacing, (c) same to DP N = 7 in the outboard
spacing, (d) same to DP N = 16 in the outboard
spacing.The vertical dashed line indicates the end of
initial phase. ne1 ≈ 1.3×1018 m-3
Top spacing. Due to peculiarity of the edge magnetic
structure, only a single, inner magnetic channel is
distinctly formed beyond the X-point (Fig. 1(b)). A
predominant fraction of the DPF is concentrated in the top
spacing (Is maximum at the DP N = 1,2). The signal of Is
to the DP N = 1 at ne1 ≈ 1.3×1018 m-3 (Fig. 7(b)) is
similar by its form to the signal Is to the DP N = 1 and to
the TI and STI current Ii to the DEA collector in the top
spacing of A-A at ne1 ≈ 0.6×1018 m-3 (Figs 2(c) and 2(d),
respectively). On the basis of such a similarity, we may
hypothesize that the step-like DPF rise at the end of the
initial phase seen in Fig. 7(b) results from a TI and STI
loss rise around the cross-section D-D.
Outboard spacing. Two symmetric magnetic channels
emerge from the X-point to this spacing (Fig. 1(b)). In the
ne1 ≈ 1.3×1018 m-3 case, similar to the top spacing of D-
D, the time evolution of the current Is maximum over the
midplane (DP N = 7) at the initial phase is ended by a
step-like Is increase (Fig. 7(c)), thus pointing to a possible
TI and STI loss rise.
It is known [7] that the non-ambipolar DPF under the
midplane (N = 16-21) is characterized by a large and
broad peak of negative current Ip [7], its absolute value
exceeding the currents Is and Ip in other divertor legs of
both A-A and D-D cross-sections. This indicates a major
fraction of lost electrons to fall into the divertor region
just on the outboard torus side near the midplane. In
contrast to the DPF in the top spacing (Fig. 7(b)) and in
the outboard spacing over the midplane (Fig. 7(c)), the
flow under the midplane undergoes a step-like drop in
both Is (Fig. 7(d) and Ip at the end of initial phase.
Accounting for the mentioned above, this indicates a
possible electron loss decrease and, consequently, an
improvement of electron confinement. In particular, such
a conclusion is consistent with an ne and ECE rise at the
end of the initial phase (Figs 2(a), 5(a), 7(a) and 2(f), 5(f),
respectively).
5. SUMMARY
1. According to the measurements having been carried
out in two symmetric poloidal cross-sections of the U-3M
torus, A-A and D-D, with a spontaneous change of the
confinement mode, a short-time decrease of all the DPF
components occurs, thus indicating a reduction of particle
loss at this phase (“initial phase of transition”).
2. At the initial phase the TI (group Ti2) and STI
content increases in the confinement volume, while at
ne1 < 1018 m-3 the fraction of such ions decreases in the
PDF on the ion toroidal B∇B drift side. This is an
evidence of an ion confinement improvement at this
phase. The low energy ions (group Ti1) do not respond to
the change of the confinement mode.
3. The rise of all the DPF components at the end of the
initial phase evidences a plasma loss increase. This
increase correlates with a decay of TI (group Ti2) and STI
content in the confinement volume. With this, an abrupt
increase of the fraction of such ions in the PDF on the ion
toroidal B∇B drift side is observed in A-A at ne1 < 1018
m-3. For the case considered this means that the plasma
loss rise at the end of the initial phase at least partially
results from a deterioration of the TI and STI
confinement.
4. In the higher starting density case, ne1 > 1018 m-3, a
rise of the energetic ion fraction in the PDF is not
observed in A-A at the end of the initial phase. However,
comparing the PDF time behavior in D-D on the ion B
∇B drift side with that in A-A at ne1 < 1018 m-3, we may
suppose that the observed decrease of the TI and STI
content at the end of the initial phase results from an
escape of these ions in the vicinity of the D-D cross-
section.
5. In the outboard spacing of the D-D cross-section on
the electron B×∇B drift side, where a considerable part of
lost electrons supposedly outflows, a step-like drop of
DPF is observed at the end of the initial phase. Combined
with an observation of an ne and ECE increase, we may
suppose an improvement of electron confinement at the
end of initial phase of transition.
6
This work was carried out in collaboration with National
Institute for Fusion Science (Toki, Japan) after the LIME
Program.
REFERENCES
1. E.D. Volkov et al.// Proc. 14th Int. Conf. on Plasma
Physics and Controlled Nuclear Fusion Research
Wurzburg, 1992 / IAEA: Vienna, v. 2, 1993, p. 679.
2. E.D. Volkov et al.//Problems of Atomic Science and
Technology. Series: “Plasma Physics”. 2003, N 1, p. 3.
3. K.H. Burrell//Phys. Plasmas, (4). 1997, p. 1499.
4. E.L. Sorokovoy et al. Characteristics of edge plasma
electrostatic turbulence in spontaneous change of
confinement mode in the Uragan-3M torsatron//
Problems of Atomic Science and Technology. Series
“Plasma Physics”, (10). 2005, N 1, p.21-23
5. V.V. Chechkin et al.//Nucl. Fusion, (42). 2002, p. 192.
6. V.V. Chechkin et al.//Nucl. Fusion,(43). 2003, p. 1175.
7. V.V. Chechkin et al.//J. Plasma Fusion Res. SERIES,
Proc. ITC-12, 2001, Toki, Japan), (5). 2002, p. 404.
ПОВЕДЕНИЕ ДИВЕРТОРНОГО ПОТОКА И ПОТЕРЬ ЧАСТИЦ
ПРИ СПОНТАННОМ ИЗМЕНЕНИИ СОСТОЯНИЯ УДЕРЖАНИЯ ПЛАЗМЫ
В ТОРСАТРОНЕ «УРАГАН-3М»
В.В. Чечкин, Э.Л. Сороковой, Л.И. Григорьева, А.С. Славный, Е.Л. Сороковой,
Е.Д. Волков, Н.И. Назаров, П.Я. Бурченко, С.А. Цыбенко, А.В. Лозин, А.Е. Кулага,
А.П. Литвинов, Ю.К. Миронов, В.С. Романов, С. Масузаки, К. Ямазаки
В условиях обнаруженного ранее спонтанного изменения режима удержания в торсатроне У-3М с
естественным винтовым дивертором показано, что на начальной стадии этого изменения уменьшаются все
составляющие плазменного диверторного потока (ПДП) и растёт содержание тепловых (ТИ) и сверхтепловых
(СТИ) ионов в основной плазме, свидетельствуя об улучшении их удержания. Начальная стадия завершается
возрастанием ПДП на стороне ионного дрейфа В×∇В, уменьшением содержания ТИ и СТИ в основной плазме
и повышенным их уходом в ПДП, что говорит об ухудшении удержания ионов. Однако, при этом уменьшается
ПДП на стороне электронного дрейфа В×∇В и растут плотность электронов и электронное циклотронное
излучение, что указывает на улучшение удержания электронов.
ПОВЕДІНКА ДИВЕРТОРНОГО ПОТОКУ ТА ВТРАТ ЧАСТИНОК
ПРИ СПОНТАННІЙ ЗМІНІ СТАНУ УТРИМАННЯ ПЛАЗМИ
В ТОРСАТРОНІ “УРАГАН-3М”
В.В. Чечкін, Е.Л. Сороковий, Л.І. Григор’єва, О.С. Славний, Є.Л. Сороковий,
Є.Д. Волков, М.І. Назаров, П.Я. Бурченко, С.А. Цибенко, А.В. Лозин, А.Є. Кулага,
А.П. Литвинов, Ю.К. Миронов, В.С. Романов, С. Масузакі, К. Ямазакі
В умовах виявленої раніше спонтанної зміни режиму утримання в торсатроні У-3М з природним гвинтовим
дивертором показано, що на початковій стадії цієї зміни зменшуються всі складові плазмового диверторного
потоку (ПДП), в той час, як зростає кількість теплових (ТІ) та надтеплових (НТІ) іонів в основній плазмі,
засвідчуючи про покращення їх утримання. Початкова стадія завершується зростанням ПДП на боці іонного
дрейфу В×∇В, зменшенням кількості ТІ та НТІ в основній плазмі та підвищеним виходом їх до ПДП, що є
ознакою погіршення утримання іонів. Але одночасне зменшення ПДП на боці електронного дрейфу В×∇В і
зростання електронної густини та електронного циклотронного випромінювання вказують на покращення
утримання електронів.
7
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