Title: Research activity on the T-10 tokamak
1Research activity on the T-10 tokamak
G. Kirnev on behalf of T-10 team
Nuclear Fusion Institute, RRC Kurchatov
Institute, Moscow 123182, Russia
2Main points. 1. Results obtained in 2005-2006. 2.
Joint experiment at the T-10 tokamak. 3. Future
plans of research activity on T-10.
?-10 R 1.5 m aL 0.3 m BT 2.5 T IP 300
kA tP 1sec ECRH 2.0 MW (0.4 sec. )
3eITB studies
4eITB formation in T-10 during ECR preheating phase
- ECR preheating vs. L-mode
- Te(0) ?
- ? Te ? at the same ?heat (? ?e?) ? eITB is formed
inside of r/a0.4
5q(r) evolution, MHD behavior and ITB dynamics
- eITB appears when slt0, qmingt3
- Internal disruptions lead to ITB shrinkage (at
qmin?3) and even to temporal disappearance (at
qmin2) - eITB deterioration starts when m1 appears in
plasma
?Te ?s/LTe characteristics of eITB strength
-Tresset G. et al, Nucl.Fus. 42(2002)520 ?Te
0.013 T-10 L-mode level
6Mechanisms of eITB Formation
Linear electrostatic flux tube code KINEZERO C.
Bourdelle et al, Nucl. Fus. 42 (2002) 892 has
been used for calculations of drift turbulence
stability
Ion drift direction
- Drift turbulence is stable (or marginally stable)
inside of ITB region during the initial stage of
discharge until qmin2 - Further evolution of plasma parameters leads to
the development of long wavelength turbulence
(mainly ITG mode) - ITG turbulence level at the time instant
corresponding to qmin2 achievement is predicted
to be close to L-mode inherent turbulence level
(!) - ETG mode is predicted to be stable inside of
r/a0.6 in a whole region of investigated
parameters
7Films and dust formation
8Formation of dust and globular structure.
SEM
Globular films and dust are observed at the
limiter cross-section (at high heat load).
10 ?m
100 ?m
Globular film has fractal structure. Diffusion
Limited Aggregation (DLA) model was applied to
describe growth of the film.
?
9Possible mechanisms of dust formation. 1. Dust
agglomeration in plasma. 2. Deposition of carbon
atoms ? Grow of the globular particles (globular
films) ? Separation of the dust particles from
the films. 3. Formation of the quasi-homogeneous
carbon film ? Fragmentation of the film and
formation globular particles with different
scales ? Separation of the dust particles from
the films.
10Nonlinear processes at the edge
11Third order spectrum (Bispectrum).
Cumulant function of the third order
Bispectral density
Bispectrum
Bispectrum (two-dimensional instantaneous
spectrum ?i(?1, ?2)) triad of instantaneous
one-dimensional spectrum at frequencies ?1, ?2 ?
?1 ?2.
Necessary condition of non-zero value of
bispectrum
(1)
Sufficient condition of non-zero value of
bispectrum
(2)
12Fluctuations of floating potential. LCFS.
Ip300kA, Bt 2.4T, ltnegt 5x1013 cm-3
Power spectrum
Mode "20 kHz" is the large-scale mode. It is
poloidally symmetrical with poloidal wave number
k??0 (from phase shift measurements in poloidal
direction). It could be result of cascading
energy transfer from the small-scale broadband
turbulence.
Bispectrum
13Fluctuations of floating potential. LCFS.
Ip300kA, Bt 2.4T, ltnegt 5x1013 cm-3
20kHz
Mode "20 kHz" interacts with continuous spectrum
by dint of three wave mechanism in a frequency
range 20-150 kHz. (f1-f220kHz)
(20,20)
(10,10) (12,8) (17,3)
Mode "20 kHz" splits to a few pairs of components
(above and below 10 kHz). (f1f220kHz)
14Poloidal asymmetry of turbulence in the plasma
core
15HFS antenna array at T-10
- Operation above 13.6 GHz for X-mode and 27.3 GHz
for O-mode
- Possible densities for Xl-mode from 1.4 up to
14.81019 m-3 - For typical discharges T-10 HFS reflectometer
band coincides with ITER required.
16Poloidal asymmetry of turbulence
- Strong asymmetry in density perturbations
amplitude - Low amplitude of quasicoherent oscillations at HFS
17Density fluctuations profile
- Fluctuations amplitude in Ohmic discharges at HFS
is in a factor of 2-3 less then at LFS and do not
increase during ECRH. - Poloidal asymmetry is well correlate with theory
predictions (unfavorable curvature)
18Threshold Effects in Pellet-Plasma Interaction
19Experimental results
- Ablation rates for different sizes of carbon
pellets demonstrate bursts/drops of ablation
near rational magnetic surfaces. - Pellets with the diameter lt 0.3 mm do not
disturb the plasma significantly. - Pellets with a larger size provoke the
reconnections. -
- Pellet ablation in the core plasma zone is
totally governed by the Kadomtsev reconnection
forming delayed ablation curves (dgt0.4 mm). - Width of the reconnection zones is few
centimeters except the Kadomtsev reconnection
zone about 10 cm at q1.
Ablation rate, a.u.
Pellet diameter 0.62 mm 0.58 0.55 0.50 0.47 0.4
5 0.40 0.35 0.30 0.20
-20 -10 0
10 20
Minor radius, cm
B. Kuteev, EPS2006, Roma, Italy, June 19-June 23,
2006
20Experimental results
Plasma center
- Cooling front propagation
- For pellets with the diameter lt 0.3 mm the
cooling front velocity coincides with the pellet
velocity (gVcool/Vpel1) . - Pellets with a larger size provoke reconnections.
At the reconnection zone the jumps of the g-ratio
are observed. -
- The highest g-ratio is observed in the core
plasma zone that is totally governed by the
Kadomtsev reconnection. - The time of the cooling fronts propagation is
shorter or comparable with the reconnection time.
Vpel
B. Kuteev, EPS2006, Roma, Italy, June 19-June 23,
2006
21Joint Experiment on T-10
22Joint Experiment - 25 September 6 October.-
three experimental groups.
Group 1. Core turbulence investigations with
correlation reflectometry.Group 2. Studies of
plasma potential fluctuations and radial electric
field with HIBP diagnostics.Group 3. Edge
turbulence investigations with the electric probe
technique.
Main objects - investigation of HFS turbulence
with respect to total turbulence level,
turbulence types and poioidal rotation.-
comparison of LFS turbulence with HFS one.-
comparison of turbulence rotation at HFS/LFS with
the ExB poloidal drift - comparison of radial
distribution of GAMs, measured with reflectometry
and HIBP.- application of the high-order
statistical analysis to the experimental data,
calculation of the bispectrum of the plasma
fluctuation, revelation of the nonlinear coupling
between fluctuations in time and space,
determination of regions of unstable mode
excitation and turbulent energy dissipation.
23Future plans.
- Investigation of an anomalous plasma transport
mechanisms - Turbulence measurements and identification in
different confinement modes, including ohmically
heated plasmas and regimes with Internal
Transport Barrier - Investigation of LFS/HFS turbulence asymmetry,
theoretical analysis of the peculiarities - Investigation of the plasma transport
peculiarities at high densities - Analysis of MHD effects on heat and particle
transport in different regimes - Investigation of the q(r) profile effects on
transport (role of the magnetic shear, rational q
surfaces) - Analysis of pellet fuelled discharges
- Energy confinement in pellet fuelled discharges
in comparison with gas-puffed discharges - Physics of pellet penetration, role of MHD
reconnections in pellet penetration - Possibility of ITB and H-mode formation in
pellet fuelled discharges - Investigation of periphery plasma behaviour
- -Analysis of peculiarities of SOL transport,
poloidal asymmetry of heat and particle fluxes - -Investigation of the radial electric field
effects on SOL transport and behaviour of high
density structures in different regimes - Investigation of plasma-wall interaction
- Investigation of dust and film generation in
different operational regimes in T-10 tokamak - Peculiarities of dust and film structure
investigation of hydrogen retention - -Experiments with liquid Li evaporator, effect of
Li on recycling