Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas
Traditionally, three transport regions have been considered in the TJ-II stellarator: the plasma core, where heat deposition physics seems to dominate transport and therefore the radial electric field; a confinement or bulk plasma region where collisional and, very likely, turbulent fluxes coopera...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2006
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| Cite this: | Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas / D. López-Bruna, A. Alonso, E. Blanco, I. Calvo, F. Castejón, T. Estrada, J. Herranz, C. Hidalgo, L. Krupnik, A. Melnikov, B. van Milligen, M. A. Pedrosa, V. I. Vargas // Вопросы атомной науки и техники. — 2006. — № 6. — С. 24-28. — Бібліогр.: 17 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859901066587406336 |
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| author | López-Bruna, D. Alonso, A. Blanco, E. Calvo, I. Castejón, F. Estrada, T. Herranz, J. Hidalgo, C. Krupnik, L. Melnikov, A. van Milligen, B. Pedrosa, M. A. Vargas, V. I. |
| author_facet | López-Bruna, D. Alonso, A. Blanco, E. Calvo, I. Castejón, F. Estrada, T. Herranz, J. Hidalgo, C. Krupnik, L. Melnikov, A. van Milligen, B. Pedrosa, M. A. Vargas, V. I. |
| citation_txt | Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas / D. López-Bruna, A. Alonso, E. Blanco, I. Calvo, F. Castejón, T. Estrada, J. Herranz, C. Hidalgo, L. Krupnik, A. Melnikov, B. van Milligen, M. A. Pedrosa, V. I. Vargas // Вопросы атомной науки и техники. — 2006. — № 6. — С. 24-28. — Бібліогр.: 17 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | Traditionally, three transport regions have been considered in the TJ-II stellarator: the plasma core, where heat
deposition physics seems to dominate transport and therefore the radial electric field; a confinement or bulk plasma
region where collisional and, very likely, turbulent fluxes cooperate interlinked by radial electric fields and plasma
rotation; and a third region near the edge where plasma-wall interaction and magnetic topology add new phenomena.
This latter region, however, may still preserve the transport properties of the bulk region. We present our latest
experimental results on edge fluctuations based on probe data and fast camera image analysis, as well as HIBP plasma
potential and heat diffusion profiles in the bulk plasma, all of them tuned under a same experimental knob: the plasma
density, which is indication of a close intertwinement of transport, turbulence and electric fields in stellarator plasmas.
Обычно в стеллараторе TJ II рассматривается перенос в трех областях: в горячей зоне, где перенос и, следовательно, радиальное электрическое поле определяются, по-видимому, механизмом вклада мощности нагрева; в зоне удержания или основной зоне плазмы, где столкновительные и турбулентные потоки связаны с радиальным электрическим полем и вращением плазмы; и в третьей периферической области, где взаимодействие плазмы со стенкой и магнитная топология добавляют новые явления в физику переноса. Однако эта последняя область еще может сохранять транспортные свойства основной области. В работе представлены последние экспериментальные данные по исследованию флуктуаций на периферии с помощью зондов и быстрой видеокамеры, а также измерения потенциала плазмы путем зондирования пучком тяжелых ионов (НIВР), и профили коэффициента теплопроводности в основной зоне. Всс эти данные регулируются одним и тем же экспериментальным параметром - плотностью плазмы. Этот факт указывает на тесную взаимосвязь переноса, турбулентности и электрических полей в плазме стелларатора.
Звичайно в стелараторі TJ II розглядається перенос у трьох областях: у гарячій зоні, де перенос і, отже, радіальне електричне поле визначаються, очевидно, механізмом внеску потужності нагріву; в зоні утримання або основній зоні плазми, де зіткненні і турбулентні потоки пов'язані з радіальним електричним полем і обертанням плазми; і в третій, периферійній області, де взаємодія плазми зі стінкою і магнітна топологія додають нові явища у фізику переносу. Проте ця остання область ще може зберігати транспортні властивості основної області. Представлено останні експериментальні дані по дослідженню флуктуацій на периферії за допомогою зондів і швидкої відеокамери, а також вимірювання потенціалу плазми шляхом зондування пучком важких іонів (НIВР), і профілі коефіцієнта теплопровідності в основній зоні. Усі ці дані регулюються тим самим експериментальним параметром - густиною плазми. Цей факт указує на тісний взаємозв'язок переносу, турбулентності й електричних полів у плазмі стеларатора.
|
| first_indexed | 2025-12-07T15:57:13Z |
| format | Article |
| fulltext |
24 Problems of Atomic Science and Technology. 2006, 6. Series: Plasma Physics (12), p. 24-28
EXPERIMENTAL INTERTWINEMENT OF RADIAL ELECTRIC FIELDS,
FLUCTUATIONS AND TRANSPORT WITH DENSITY IN TJ-II PLASMAS
D. López-Bruna, A. Alonso, E. Blanco, I. Calvo, F. Castejón, T. Estrada, J. Herranz, C. Hidalgo,
L. Krupnik1, A. Melnikov2, B. van Milligen, M. A. Pedrosa, V. I. Vargas and the TJ-II Team
Laboratorio Nacional de Fusión, Asociación EURATOM-CIEMAT, Madrid, Spain;
1Institute of Plasma Physics, NSC “KIPT”, Kharkov, Ukraine;
2Institute of Nuclear Fusion, RRC “Kurchatov Institute”, Moscow, Russia
Traditionally, three transport regions have been considered in the TJ-II stellarator: the plasma core, where heat
deposition physics seems to dominate transport and therefore the radial electric field; a confinement or bulk plasma
region where collisional and, very likely, turbulent fluxes cooperate interlinked by radial electric fields and plasma
rotation; and a third region near the edge where plasma-wall interaction and magnetic topology add new phenomena.
This latter region, however, may still preserve the transport properties of the bulk region. We present our latest
experimental results on edge fluctuations based on probe data and fast camera image analysis, as well as HIBP plasma
potential and heat diffusion profiles in the bulk plasma, all of them tuned under a same experimental knob: the plasma
density, which is indication of a close intertwinement of transport, turbulence and electric fields in stellarator plasmas.
PACS: 52.25.Fi, 52.25.Gj, 52.55.Dy, 52.55.Hc, 52.70.Ds, 52.70.Gw
1. INTRODUCTION
Already in 1990, with a first generation of medium-
sized stellarators operative, low collisionality plasmas
obtained with Electron Cyclotron Heating (ECH) showed
that the plasma core region could be reasonably well
described by collisional transport, but most of the bulk
plasma presented an anomalously high electron heat
transport [1,2]. The present gyro-Bohm stellarator scaling
of the energy confinement time [3] is compatible with
diffusive processes based on microscopic transport. In
addition, global scalings with heating power, as it happens
with tokamaks, support the notion of transport dominated
by mechanisms fed non-linearly on thermodynamic
gradients, of which turbulent transport is a paradigm.
Since sheared ExB flows (DC or fluctuating) are expected
to affect turbulent transport, it is worth looking for any
systematic relationship between flows, turbulence and
transport.
In TJ-II experiments up to date, plasma potential and
heat transport vary with density in a systematic manner.
Here we summarize the experimental relationships found
between poloidal flows, plasma potential, fluctuations and
heat transport as one experimental controller, the plasma
line density (<ne>), is varied.
2. EXPERIMENTAL RESULTS
The Heavy Ion Beam Probe (HIBP) diagnostic
installed in the TJ-II is able to resolve a flattening of the
plasma potential profile, ϕ(ρ), in the presence of a low
order rational value of the rotational transform. This
situation of close to null or small Er = -∇ϕ(ρ) in an
extended radial region can be found also without the
presence of major magnetic resonances. A transition of
ϕ(ρ) evolving from positive to negative as the density is
increased is known in stellarator devices (see e.g. [4]). In
the case of the TJ-II, it has been seen on a shot to shot
basis (stationary plasmas) and dynamically. In Fig. 1 we
see ϕ(ρ) varying as the density grows during an
ECH+NBI discharge. Near the edge (positive ρ), the slope
of the plasma potential profile reverses sign when the
average density reaches some 0.8·1019 m-3. There is little
change in ϕ(ρ) for line average densities above some
2·1019 m-3. The smooth change from everywhere positive
to everywhere negative plasma potential is known to be a
systematic feature not dependent on configuration as far
as it has been checked.
Fig.1. HIBP profiles decaying during the growth of the
plasma density in a discharge with ECH+NBI heating.
When <ne> 1.4·1019 m-3 the plasma is sustained by NBI
alone
The higher densities of Fig. 1 are obtained in the pure
NBI phase of the discharge (densities above ECH cutoff,
<ne> ·1.2·1019 m-3), when the density profiles change
from hollow to peaked. More HIBP data for different
density scans show that the region -∇ϕ(ρ) 0 moves
inwards in a rather smooth way as the density increases.
The shear layer caused by the corresponding structure of
the ExB drift moves inwards and seems to widen. Here
we define shear layer as the radial region where Er
reverses sign, although in most of the experimental data
shown in this work, it extends (within resolution) to a
considerable part of the plasma.
25
Fig. 2. Mean frequency of the reflectometer spectra vs.
cut-off radius in discharges with increasing densities
Normally, the regions of flat ϕ are bounded by
regions with high poloidal velocity. Therefore, it makes
sense speaking of boundary shear layers not only in the
plasma edge but also in the confinement zone. The
existence of a shear layer in the bulk plasma of the TJ-II
has been confirmed by means of microwave reflectometry
[5] (MWR). In Fig. 2 we plot the mean frequency of the
spectra obtained in four ECH discharges with different
line averaged densities. The diagnostic can give with
good spatial accuracy the radial position of the inner shear
layer, here detected as the location where the mean
frequency changes sign as a consequence of the reversal
in the rotation of the detected fluctuations. Since the
diamagnetic drift here is quite smaller than the ExB drift,
the data from the reflectometer should be compatible with
the electric fields deduced from HIBP data. Aside from
the spatial uncertainty of the HIBP, the qualitative result
is confirmed: a shear layer moves towards the center as
the plasma density increases. For densities above the ECH
regime, the radial electric field is negative and
monotonous in essentially all of the plasma and a shear
layer can only exist in the plasma edge.
HIBP data show that the regions of approximately null
Er and their corresponding inner shear layer can be
followed in every radial region of the plasma as density is
augmented. A link between flows and transport is a
natural expectation already from the basic formulation of
transport in a cylindrical column. However, despite
notable difficulties in quantifying fluctuation levels,
MWR in the TJ-II indicates that there is significant
turbulence in the entire radial range of Fig. 2. Therefore,
it is natural to suspect that the link between electric fields
or plasma flows and turbulence responds to the same
mechanisms than further out in radius, where electric
probes can be used.
The edge region can be explored with detail by means
of different kinds of electric probe. TJ-II plasmas (as well
as other confinement machines) are characterized by flat
ϕ profiles from the plasma border out. Thus, the plasma
edge can develop naturally a shear layer as soon as there
is a change of plasma potential near (inside) the edge.
We recall from experiments in the Advanced Toroidal
Facility [6] that a change in poloidal rotation as seen in
the phase velocity of fluctuations at the plasma periphery
(ρ ~ 0.9) correlates with the onset of a shear layer with
altered fluctuation levels. More recent data from the TJ-II
evidence a threshold line density, near 0.6·1019 m-3 in
typical ECH plasmas in standard configuration, that
marks the start of a systematic link between density
fluctuation levels, plasma potential and poloidal rotation
[7]. Fig. 3 shows (left panels) the profiles of probe ion
saturation current, proportional to plasma density in the
corresponding experimental conditions, for different
values of <ne> obtained in different discharges. At low
line densities the gradient in the ion saturation current
remains roughly the same. After reaching
<ne> 0.6·1019 m-3, a larger gradient develops and, at the
same time, the floating potential measured by the same
probe drops to negative values (bottom panel). As a
consequence, an edge shear layer develops.
It is interesting to follow the formation of the edge
shear layer on the evolution of time-traces in a fixed
radial position: Also in Fig. 3 (right panels) we plot with
dots the rms value of the fluctuating ExB radial velocity
estimated from the tip separation on the probe, as a
function of <ne> for a large set of discharges. The bottom
panel shows the corresponding values of the phase
velocity of the fluctuations. The relationship between
fluctuations, poloidal phase velocity and density is robust:
when <ne> is changed in one discharge by modulation of
the gas puffing waveform, we obtain the data shown with
thin lines in the right panels of Fig. 3. At the threshold
density we see a change in the phase velocity that
correlates with increasing fluctuations. However, once the
new (negative) value of such velocity reaches its
maximum magnitude, the fluctuations stop growing and
tend to diminish instead. Here we assume that the line
density can be associated in this region to the local
density scale length, which is really considered as a more
relevant parameter. The threshold <ne> is marked in the
right panels of Fig. 3 with vertical bands.
Fig. 3. Left: edge profiles of ion saturation current
(top) and floating potential (bottom). Right: rms value of
the fluctuating poloidal electric field (top) and phase
velocity of the fluctuations (bottom) for a set of stationary
discharges (dots) and for a single discharge with evolving
density (lines). Probe radial position: ρ 0.9
The results of Fig. 3 suggest that when there is enough
available free energy the plasma-flow system self-
regulates: near (below) the threshold density, the level of
fluctuations and the magnitude of flow rotation increase
in parallel until the shear flow is established at the edge;
then the fluctuations decrease while edge gradients and
plasma density increase. The critical nature of this
26
phenomenon is suggested by observations at the density
threshold, when fast transients (tens of µs) can be
obtained in the phase velocity measured with the probes
[8], as shown in Fig. 4. There we see a case in which the
threshold is reached from below: the time-trace of the
floating potential in ρ 0.9 stays positive on average but
it explores intermittently the negative values.
Fig.4. Detail of the transients observed when sheared
flows are being developed at the critical density
The data shown above are obtained from fluctuating
electric signals in the plasma edge region. The phase
velocity of the fluctuations is intuitively associated to the
movement of elongated turbulent structures convected by
the mean poloidal flow. Recent results, coming both from
the NSTX spheromak and the TJ-II Heliac indicate
similar behaviour of turbulent structures, which we shall
refer to as “blobs”, in the plasma edge region [9]. The
data have been obtained with recordings of fast cameras
that are able to resolve typical time-scales of electrostatic
turbulence. After processing, it has been found convenient
to define such geometrical parameters as scale size,
orientation and aspect ratio of the blobs. All three
parameters get affected during the L-H transition in the
NSTX: the net orientation and aspect ratio of the blobs
population increase in H mode with respect to the L
mode, while the overall population decreases.
Interestingly, the same qualitative results, albeit less
pronounced, are seen in the TJ-II but taking as
“transition” process the formation of a shear layer
commented above. Therefore, these recordings confirm
what has been said on the existence of a shear layer that
develops after the threshold density is reached, and add
the information that there are statistically significant
morphological changes in the visualized structures.
A detailed quantification of the above and some other
aspects of the images recorded by the high speed cameras
still require further study. What can be cast out of any
doubt in the TJ-II is that the blobs reverse rotation at the
density threshold. Let us recall that, below such density,
Er as obtained from the HIBP diagnostic is everywhere
positive. Above the density threshold an edge shear layer
shows up and the inner one moves inwards as the density
keeps on rising (Fig. 1). The bi-dimensional structures
detected by the cameras reverse their poloidal movement
at that density, in close agreement with the behaviour of
the phase velocities obtained with electric probes: Fig. 5
shows six consecutive frames of a recording where such
reversal of the detected poloidal rotation occurs.
Following the frames from top to bottom and from left to
right, we see (marked with small squares) one of these
blobs moving counterclockwise (left) and then clockwise
(right) at the density threshold. The fast transients
(~10 µs) detected by the Langmuir probes (like those
shown in Fig. 4) share the density threshold with the
reversal found with high speed imaging.
Fig.5. Evolution of the poloidal movement of blobs when
the threshold density is reached in a discharge with
density ramp-up
3. DISCUSSION AND CONCLUSIONS
For low densities or typical ECH plasmas of the TJ-II,
the region of normalized radii ρ < 0.3 is dominated by the
electron dynamics, e. g. ECH-driven pump-out. Recalling
Fig. 1, we see that the core values of ϕ in that case are
what one would expect from a simple radial momentum
balance with frozen ions and electrostatically “stopped”
electrons: the ∇(neTe)/(ene) contribution yields a core Er
like the one found in the experiments. These values of Er
are expected also from neoclassical calculations for the
TJ-II [9]. Fig. 6 shows ϕ obtained after integrating the
quantity Edia = -∇(neTe)/(ene) (with ϕ = 0 at the edge),
which can be compared with HIBP data in Fig. 1. Since
the core density gradient is very small in ECH plasmas,
ϕ Te/e. The close relationship found between central
electron temperature and plasma potential in low density
plasmas is compatible with the results from ECH
modulation experiments, where the modulation of ECRH
power causes a small (~10%) change in beam ion current
(say plasma density), but a much more marked change
(~50%) in ϕ in most of the core region, ρ < 0.6 [11].
Furthermore, the time-scales associated with the fast
transients of ϕ in these modulation experiments, are
compatible with time-scales of the electric field dynamics
according to the equations for radial and poloidal electron
momentum balance,
θθθ
θ
ν Γ−Γ−=Γ
∇−Γ+−=Γ
r
r
B
m
e
p
m
B
m
eE
m
en
&
&
1
27
and Poisson's reE Γ= )/( ε& . Here we simply consider
that an initial (and local) condition of non-equilibrium
electron radial flow Γr must alter the radial electric field
and, consequently, the balances. The plasma response
should come through Er-dependent transport coefficients.
These equations yield a characteristic time-scale of order
1/νθ, much faster than typical transport time scales but
slower than plasma oscillations.
In addition, let us remember that plasma rotation
measurements taken since the earliest TJ-II campaigns
(ECH plasmas) [12] indicated positive Er near the core,
with a strong increase in Er in cases of high Te(0). The
electric field here is obtained under the assumption that
all the plasma rotation is due to the ExB drift, a fair
assumption for the ions. Lower temperature (higher
density) plasmas in the same campaigns yield smaller Er
that decrease more gently as Te decreases. Further studies
showed a qualitative behaviour of the estimated plasma
rotation in fair agreement with neoclassical calculations
of the radial electric field [13].
Fig. 6. The electrostatic potential obtained integrating the
diamagnetic contribution to Er for TJ-II ECH plasmas
looks alike for different densities. There is agreement with
HIBP measurements only for the lowest densities
In the bulk plasma region of ECH discharges, heat
diffusion has been quantified from Te measurements and
an estimate of the heat deposition zone [13]. Fig. 7 is a
surface plot of χ(ρ) as a function of <ne>. The values
have been obtained from a large set of ECH discharges of
the TJ-II with stationary conditions and using a typical
diffusive description of transport. The heat source is
assumed to be Gaussian-shaped and centered, and
experimental profiles of density and temperature are
obtained from Thomson Scattering data. Discharges have
been grouped and averaged by small density ranges. It
was checked that including total radiation does not alter
significantly the results. The data in Fig. 7 are presented
only for the region 0.2 ρ 0.8 because outside this
range the statistical errors are too large. A fit of the data
for the variation of local χ(ρ) with line-density only
yields significant dependencies in the density gradient
region, 0.5 ρ 0.8, where we can appreciate that the
thermal diffusivity decreases as the line-density increases.
Generally speaking, the calculations of collisional
diffusivities and Er in the density gradient region of ECH
plasmas of the TJ-II are reliable within the hypothesis of
the calculations [10]. Qualitatively, the electric field
should be found in the so called ion root in this radial
region with larger magnitude the larger the density.
Except for the very low densities of Fig. 1, this is the case
according to the experiments. χ is expected to decrease
with <ne> in this region because of the smaller ambipolar
particle fluxes that correspond to the ion root. On the
other hand, the thermal diffusion expected from these
calculations appears to be too small with respect to the
experimental values of Fig. 7, something in agreement to
well established results from several other machines
(CHS, L-2, W7-AS...). Therefore, the TJ-II seems to be
no exception to the importance of, presumably, turbulent
ambipolar fluxes.
Fig. 7. Density scan of χ profiles in TJ-II ECRH plasmas.
The contours indicate iso-diffusivities with values
according to the vertical palette
Turning to HIBP data, we can roughly relate the inner shear
layer or, perhaps, the extension of the flatter ϕ region with
the extension of the furrow in χ(ρ) of Fig. 7. From MWR we
know that there is turbulence in this region, but it is unknown
to what extent turbulent transport can explain the changes in
diffusion there. What can be said in view of Figs. 7 and 2 is
that the shear layer is compatible with better heat
confinement, at least in the density gradient region of TJ-II
ECH discharges (<ne> 1019 m-3). Let us also recall that
improved confinement achieved in the TJ-II with polarized
limiters affects density but not electron temperature [14],
which is the behaviour found in the density scan: what Fig. 7
shows is consequence of the density profiles developing
larger gradients (ρ 0.5) and also larger absolute values
while the electron temperatures stay roughly the same, i. e.,
the thermal transport must be decreasing as represented by
the interpretative thermal diffusivity of Fig. 7. According to
this, the heat diffusion also follows closely any changes in Er
with a reasonable chance that not only the establishment of
an ion root, but also a flow regulated turbulence, is tailoring
the transport. An important question for which we still do not
have data is whether the flatter ϕ regions can be related with
null or small Er or, rather, with fluctuating fields of null time-
average (for the time resolution of the diagnostics) but able
to moderate transport, as is expected from zonal flow
dynamics.
Although the bulk region is further in than the zone
explored with fast cameras and electric probes, we may
assume that the relation between flows and turbulence
remains the same in the entire density gradient region, which
really extends up to the very edge (see e. g. Fig. 3). We have
seen that there is a spontaneous generation of shear flow
right at the edge, which in turn moderates turbulence levels
and, assuming steady sources, particle (and heat) transport.
General considerations about the effect of shear flows on
turbulence levels and transport [15] lead to the notion that
turbulence and macroscopic flows must be considered
28
together, especially when the physical conditions are close to
developing structural changes in the turbulence levels, as is
the case in the vicinity (in parameter space) of L-H
transitions [16]. The results found in the edge of the TJ-II
seem to confirm this notion. Furthermore, the similarity
between results in the TJ-II (where no L-H transition has
been achieved) and measurements in other machines in
conditions of actual L-H transition, suggests that the
underlying physics is the same. There are, however, two
important aspects to consider in a general description such
transitions [17]. First, a threshold in some relevant parameter
must mark the beginning of the transition mechanism. Once
reached the threshold value, the system heads rapidly to the
new confinement regime. And, second, after the transition
the threshold condition (which in many theories is a critical
gradient) for the back transition changes implying hysteresis
in the system. With this in mind, the fact that there is no such
hysteresis (neither L-H transition) in the TJ-II, but the link
between shear flow and turbulence can be observed as in
other machines that do undergo L-H transition, may be an
indication that the plasma conditions in the TJ-II (perhaps the
strong plasma-wall interaction) can make apparent the
seeding mechanism for the transition but there is not enough
power to force the, so to speak, hard transition. By seeding
mechanism we mean a trigger for the amplification of shear-
flow due to Reynolds stress momentum redistribution.
Further shearing should make the Reynolds stress drive for
poloidal momentum decrease due to decreasing turbulence
levels and perhaps turbulent anisotropy. A hard transition
can be maintained by steep gradients that allow for ExB
shear flows through the diamagnetic contribution to the
radial electric field. In this frame, TJ-II experiments are
exploring the pre-transition dynamics. Further studies and
experiments are aimed at clarifying these aspects, extending
them if possible to the bulk plasma region.
REFERENCES
1. H. Renner et al.// Plasma Phys. Contr. Nucl. Fusion Res.
IAEA, Vienna, 1992, v. 2, p. 473.
2. M. Murakami et al.// Plasma Phys. Controll. Nucl. Fusion
Res. IAEA, Vienna, 1992, v. 2, p. 455.
3. H.Yamada et al.// Nuclear Fusion. 2005, v. 45(12),
p. 1684-1693.
4. A. Fujisawa et al.// Phys. Rev. Lett. 1997, v. 79, p. 1054.
5. T. Estrada, E. Blanco, L. Cupido, M. E. Manso, J. Sánchez//
Nucl. Fusion. 2006, v. 46, p. S792-S798.
6. C. Hidalgo et al.// Proc. 17th European Conf. on Contr.
Fusion and Plasma Physics, Amsterdam. ECA 1990, v. 14B,
part 111, p. 1353-1356.
7. M. A. Pedrosa et al.// Plasma Phys. Control. Fusion. 2005,
v. 47, p. 777.
8. M. A. Pedrosa et al.// 33rd EPS Conference on Plasma
Physics and Controlled Fusion, Rome, Italy, 2006.
9. A. Alonso et al.// 33rd EPS Conference on Plasma Physics
and Controlled Fusion, Rome, Italy, 2006.
10. V. Tribaldos // Phys. Plasmas. 2001, v. 8(4), p.1229-1239.
11. L. Krupnik et al.// 33rd EPS Conf. on Plasma Physics and
Contr. Fusion, Rome, Italy, 2006.
12. B. Zurro et al.// 26th EPS Conf. on Contr. Fusion and
Plasma Physics. ECA. 1999, v. 23J, p. 357 - 360.
13. V. I. Vargas et al.// 33rd EPS Conf. on Plasma Physics
and Controlled Fusion, Rome, Italy, 2006.
14. C. Hidalgo et al.// Plasma Phys. Control. Fusion. 2004,
v. 46, p. 287-297.
15. P. W. Terry // Rev. Mod. Phys. 2000, v. 72(1), p.109-165.
16. B. A. Carreras et al// Plasma Phys. Controll. Nucl. Fusion
Res. IAEA, Vienna, 1992, v. 2, p. 97.
17. J. W. Connor, H. R. Wilson // Plasma Phys. Control.
Fusion. 2000, v. 42, p. R1-R74.
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| id | nasplib_isofts_kiev_ua-123456789-81771 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T15:57:13Z |
| publishDate | 2006 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | López-Bruna, D. Alonso, A. Blanco, E. Calvo, I. Castejón, F. Estrada, T. Herranz, J. Hidalgo, C. Krupnik, L. Melnikov, A. van Milligen, B. Pedrosa, M. A. Vargas, V. I. 2015-05-20T15:10:43Z 2015-05-20T15:10:43Z 2006 Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas / D. López-Bruna, A. Alonso, E. Blanco, I. Calvo, F. Castejón, T. Estrada, J. Herranz, C. Hidalgo, L. Krupnik, A. Melnikov, B. van Milligen, M. A. Pedrosa, V. I. Vargas // Вопросы атомной науки и техники. — 2006. — № 6. — С. 24-28. — Бібліогр.: 17 назв. — англ. 1562-6016 PACS: 52.25.Fi, 52.25.Gj, 52.55.Dy, 52.55.Hc, 52.70.Ds, 52.70.Gw https://nasplib.isofts.kiev.ua/handle/123456789/81771 Traditionally, three transport regions have been considered in the TJ-II stellarator: the plasma core, where heat deposition physics seems to dominate transport and therefore the radial electric field; a confinement or bulk plasma region where collisional and, very likely, turbulent fluxes cooperate interlinked by radial electric fields and plasma rotation; and a third region near the edge where plasma-wall interaction and magnetic topology add new phenomena. This latter region, however, may still preserve the transport properties of the bulk region. We present our latest experimental results on edge fluctuations based on probe data and fast camera image analysis, as well as HIBP plasma potential and heat diffusion profiles in the bulk plasma, all of them tuned under a same experimental knob: the plasma density, which is indication of a close intertwinement of transport, turbulence and electric fields in stellarator plasmas. Обычно в стеллараторе TJ II рассматривается перенос в трех областях: в горячей зоне, где перенос и, следовательно, радиальное электрическое поле определяются, по-видимому, механизмом вклада мощности нагрева; в зоне удержания или основной зоне плазмы, где столкновительные и турбулентные потоки связаны с радиальным электрическим полем и вращением плазмы; и в третьей периферической области, где взаимодействие плазмы со стенкой и магнитная топология добавляют новые явления в физику переноса. Однако эта последняя область еще может сохранять транспортные свойства основной области. В работе представлены последние экспериментальные данные по исследованию флуктуаций на периферии с помощью зондов и быстрой видеокамеры, а также измерения потенциала плазмы путем зондирования пучком тяжелых ионов (НIВР), и профили коэффициента теплопроводности в основной зоне. Всс эти данные регулируются одним и тем же экспериментальным параметром - плотностью плазмы. Этот факт указывает на тесную взаимосвязь переноса, турбулентности и электрических полей в плазме стелларатора. Звичайно в стелараторі TJ II розглядається перенос у трьох областях: у гарячій зоні, де перенос і, отже, радіальне електричне поле визначаються, очевидно, механізмом внеску потужності нагріву; в зоні утримання або основній зоні плазми, де зіткненні і турбулентні потоки пов'язані з радіальним електричним полем і обертанням плазми; і в третій, периферійній області, де взаємодія плазми зі стінкою і магнітна топологія додають нові явища у фізику переносу. Проте ця остання область ще може зберігати транспортні властивості основної області. Представлено останні експериментальні дані по дослідженню флуктуацій на периферії за допомогою зондів і швидкої відеокамери, а також вимірювання потенціалу плазми шляхом зондування пучком важких іонів (НIВР), і профілі коефіцієнта теплопровідності в основній зоні. Усі ці дані регулюються тим самим експериментальним параметром - густиною плазми. Цей факт указує на тісний взаємозв'язок переносу, турбулентності й електричних полів у плазмі стеларатора. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Magnetic confinement Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas Экспериментальное исследование взаимосвязи радиальных электрических полей, флуктуаций и переноса с плотностью в стеллараторе TJ II Експериментальні дослідження взаємозв’язку радіальних електричних полів, флуктуацій і переносу плазми у стелараторі TJ II Article published earlier |
| spellingShingle | Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas López-Bruna, D. Alonso, A. Blanco, E. Calvo, I. Castejón, F. Estrada, T. Herranz, J. Hidalgo, C. Krupnik, L. Melnikov, A. van Milligen, B. Pedrosa, M. A. Vargas, V. I. Magnetic confinement |
| title | Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas |
| title_alt | Экспериментальное исследование взаимосвязи радиальных электрических полей, флуктуаций и переноса с плотностью в стеллараторе TJ II Експериментальні дослідження взаємозв’язку радіальних електричних полів, флуктуацій і переносу плазми у стелараторі TJ II |
| title_full | Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas |
| title_fullStr | Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas |
| title_full_unstemmed | Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas |
| title_short | Experimental intertwinement of radial electric fields, fluctuations and transport with density in TJ-II plasmas |
| title_sort | experimental intertwinement of radial electric fields, fluctuations and transport with density in tj-ii plasmas |
| topic | Magnetic confinement |
| topic_facet | Magnetic confinement |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/81771 |
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