Date post: | 03-Jan-2016 |
Category: |
Documents |
Upload: | virginia-boyer |
View: | 32 times |
Download: | 1 times |
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 1 /26
Experimental investigation of Experimental investigation of
Nicolas FedorczakNicolas Fedorczak
Thesis supervisor : A. Pocheau (IRPHE)Thesis supervisor : A. Pocheau (IRPHE)
turbulent transportturbulent transport
at the edge of tokamak plasmasat the edge of tokamak plasmas
CEA supervisor : P. Monier-GarbetCEA supervisor : P. Monier-Garbet J.P. Gunn J.P. Gunn
Ph. GhendrihPh. Ghendrih
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 2 /26
Magnetic confinement & transportMagnetic confinement & transportMagnetic confinement of ~10keV plasma
Tokamak :
Z
BTBP
r
flux surfacesfield-lines
// direction : free motion direction : constrained by B
!! gradients (no thermo-dynamical equilibrium) + curvature transport
nT
r
transport
wall
- energy losses to the walls
- pressure gradient in core plasma
critical issue for reactor operation
critical issue for reactor efficiency
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 3 /26
Edge transport : turbulence & asymmetryEdge transport : turbulence & asymmetryCurrent tokamaks :JET, DIII-D, ASDEX, Tore Supra, NSTX, TCV, Alcator C-mod …
• demonstrated the high level of turbulence
ExB convection2B
BEv
Picture from fast imaging on Tore Supra :
E = -
Tore Supra
LFSHFS
E = -
Tore Supra
LFSHFS
Experimental evidences : interchange
P + B
free energy source drive instability
HFS : stable / LFS : unstable
• demonstrated transport asymmetriesTore Supra, C-mod
J.P. Gunn JNM2006B. LaBombard NF2004
Garcia & Pitts NF2007
BB
PP
BB
PP
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 4 /26
Edge plasma influenced by plasma/wall interactionEdge plasma influenced by plasma/wall interaction
Boundary of confined plasma : open field lines region = Scrape-Off Layer
Core plasma
SOL
closed field lines
open field lines
LCFS
particle / energy flux
plasma facing component
delimited by the Last Closed Flux Surface
Plasma facing components (PFC) :
- perfect sink of particle
- regulate charges & currents
- spatial symmetry breaking
rLCFS SOL
q//
determine the SOL plasma equilibrium
(balance between // and fluxes)
Heat load footprint, matter migration (flows)+ boundary conditions for core rotation
flows
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 5 /26
Open issues related to ITER projectOpen issues related to ITER project
ITER : next step toward fusion reactor
- High performances discharges
- steady-state + fusion reactions
Critical issues related to edge plasma Critical issues related to edge plasma
No robust model to predict:No robust model to predict:
- Heat load on first wall
Physics of blobs, ELM’s & transport barriers
nTcore pedestal SOL
rLCFS
- Pedestal gradient
(shear flow & boundary conditions)
shear-flow flow boundary
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 6 /26
Build a consistent picture of particle transport at the edge Build a consistent picture of particle transport at the edge
Axis of my research on Tore Supra Tokamak
radial extent radial extent Electrostatic turbulenceElectrostatic turbulence
Parallel flowsParallel flows
?
Difficult to address from current experiments :C-mod, DIII-D, ASDEX, JET
Multi-diagnostic investigation of edge turbulent transport
Mach probe // flows and density profiles
Rake probes electrostatic fluctuations
Fast imaging &
reflectometers
fluctuation dynamics&
asymmetries
Constrain models :
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 7 /26
I. How do we diagnose the plasma phenomena I. How do we diagnose the plasma phenomena
1. Langmuir probes
2. Fast visible imaging
II. The model drawn from experiments on Tore Supra II. The model drawn from experiments on Tore Supra
1. Consistency local / global measurements
III. Implications & conclusion
Experimental investigation of turbulent Experimental investigation of turbulent transport at the edge of tokamak transport at the edge of tokamak
plasmas plasmas
2. 3D properties of edge particle transport : revisiting filaments
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 8 /26
Reciprocating Langmuir probes 2 hydraulic systems installed at the plasma top full radial profile collection
Illustration of data collection along the
probe path
200 ms
!! experience strong heat flux ~MW.m-2
probe path
Confined region
I
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 9 /26
Improving Mach measurements• plasma collection by a biased electrode
local plasma parameters : ne, Te, plasma
Mach configuration : // flow velocity
undisturbed plasma
B
V//!! time averaged data !!
I
3-5 mm
Tunnel collector
plate collectorBoron nitride
B
small collector
effective collection
area
B
Tunnel collector small cylindrical collector
? large effect on flow velocity measurementsYet, tunnel probes used only on Tore Supra…
Gunn, Dejarnac
(poloidal rake probe)
calibration with effective collection area sensitive to collector geometry
Mach collectors of the rake probe
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 10 /26
Implementing rake probes for fluctuations
ISAT amplifiers16 channels
Pre filter(250kHz)
14 bits ADC2X16 channels
probes
vessel
CPU controllers
TS control room
DTURB diagnosticDTURB diagnostic
~30 m
Mode selectionVfl amplifiers
16 channels
DC power supplies
1 MHz acquisition rate + ~mm spatial 1 MHz acquisition rate + ~mm spatial samplingsampling
ExB convection potential potential && density density
In charge of the final design, maintenance & use of a new diagnostic
DTURB & the rake probes
mode selectionmode selection
anti-aliasing anti-aliasing dynamical sampling : SNR dynamical sampling : SNR
Collaboration with Gent University (G. Van Oost)Collaboration with Gent University (G. Van Oost)
Requirements for SOL plasma fluctuations:
Improved control & electronics for a flexible & sensitive acquisition
I
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 11 /26
Issue on the interpretation of fluctuations
Turbulent flux : EnB
vn rturbr
~~1~~
en~plV
~plV~
rake probe
plpl VV
E 21
~~~
Discrete measurement :
Effect of electric field under-sampling ? (Never mentioned in the literature)
I
Tokam 2D
V
V
ne
r
Error calculated on turbulence simulation
0
0.2
0.4
0.6
0.8
1
0 0.5 1 1.5
synthetic
non negligible errordepends on potential eddy size
Some experimental data are not exploitable for rturb !!
experiment
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 12 /26
Fast imaging of edge transport phenomena Use visible plasma emission to picture the density fluctuations
Rich qualitative understanding: geometrical + dynamical
ICRH pellet
pellet SMBI
SMBI
SMBI
Tore Supra top view
Camera view Virtual view
Collaboration with Nancy university + IRPHE
turbatomicrelax turb
ionisationmfp &local plasma electrons local plasma electrons
excite neutralsexcite neutrals &
wide opening angle
up to 50 kHz (effective exp turb )
I
SMBISMBI SMBISMBI
High field side
Low field side
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 13 /26
Qualitative information
Movies resolve the main turbulence dynamics extraction ?
reconstruction?
Tangential projection of ~2D turbulence
Tomographic reconstruction
Collaboration LPMIA F. Brochard / G.Bonhomme + LMD R. Nguyen / M. Farge
cmturberr 1~~
ILFS gas injection recorded @ 50kHz
V ~ 850 m.s-1
V ~ -400 m.s-1
Vr ~ 500 m.s-1
Equatorial midplane
LCFS Velocity extraction @ midplane
(reduced projection artifact)Qualitative
agreement with reflectometers
Collaboration LPP L. Vermare
camera
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 14 /26
Transport model: diagnostics capabilities
Tunnel Mach probe // flows
global particle balance+
spatial asymmetries
Fast visible imaging spatial properties
transport mechanisms
+spatial asymmetries
3D transport description from experimental evidences
Poloïdal rake probe local ExB turbulence
transport mechanisms +local amplitude //
probes
rturb
fast imaging
II
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 15 /26
Vfl
Vfl
ne
E
EnB
vn rturbr
~~1~~
n~ E~
& fluctuate in phase & fluctuate in phase
probeprobe
SOLSOL
LCFSLCFS
BBT T IIPP
Electrostatic fluctuations : interchange-like
Radial convection of density burstsRadial convection of density bursts
“bursty” transportDevynck, Boedo, Zweben
II
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 16 /26
Electrostatic fluctuations : associated transport Intermittent convection of density bursts :
qualitative agreement with fast imaging
ordering consistent with density profiles but not quantitatively
1-ms30
rV
1-ms 300
rV
Vrblobs > 300 m.s-1 ( 1% cS )
Averaged effect : Vrplasma ~ 30 m.s-1 ( 0.1% cS )
V ~ 850 m.s-1
V ~ -400 m.s-1
Vr ~ 500 m.s-1
Equatorial midplane
LCFS
Consistency local vs. global measurements asymmetries ?
signature of filament convection?
II
rr vnn
V ~~1
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 17 /26
// flow drivers in TS SOL : radial particle flux
cm 5.4
exp
r
re
arn
What mechanisms forWhat mechanisms for
• // velocity// velocity
• density profiledensity profile
??
ionr
rr SB
Envn )( ////
“ PS flows”probe data
limiter recycling MC simulation
~15%
EIRENE Y. Marandet
~10%
Particle flux balance :
// flow radial flux?
main driver M//
ne
II
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 18 /26
// flow velocity & radial flux asymmetry
)( //// rrvn Particle flux balance
LIM
ITE
R
LIM
ITE
R
LCFS LCFSrr
// flows// flowsMagnetic field lineMagnetic field line
confined plasmaconfined plasma
Conservation law (pressure) 0 22//// Scnvn
// flows balance the particle source asymmetry
Boundary conditions @ limiters 12// M (Bohm)
quantify the global particle balance (r into the SOL)
SOL plasma
partial resolution of asymmetries
II
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 19 /26
LFSLFS
probeprobe
HFSHFS rLFSr
HFS
• r() highly enhanced @ LFS
? consistency with local ExB flux ?
spatial mapping
flows balance: quantify LFS / HFS asymmetryconservation laws applied to local // flow conservation laws applied to local // flow profiles profiles
cm 5.4
exp
r
re
arn
M// profile @ top
0 0.02 0.04 0.06 0.08 0.1
0.2
0.40.4
0.6
0.8
1
r – a (m)
M//
near sonic @ top !!
<r>LFS
<r>HFS
> 20
II
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 20 /26
r centered @ outboard midplane in a narrow poloidal section (50°)
reference
r
private
r
S
dl
dlf
// //
// //
Field line tailoring : resolve spatial asymmetryUse movable limiters to tailor the flux distribution along field lines
quantify // flows response in term of radial flux distribution
IIL
IMIT
ER
LIM
ITE
R
LFSHFS
probe r
LIM
ITE
R
LIM
ITE
R
LFSHFS
probe
2nd limiter
private region
r// //
LIM
ITE
R
LIM
ITE
R
LFSHFS
probe r
LIM
ITE
R
LIM
ITE
R
LFSHFS
probe
2nd limiter
private region
r// //
r
l//
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 21 /26
TS44789r – a = 2.5 cmlad = 2.6 1019 m-2
TS44789r – a = 2.5 cmlad = 4.5 1019 m-2
TS44635r – a = 1 cmlad = 5 1019 m-2
43° 47° 52°r ExB
r ExB r ExB
Local / global consistency - Mach probe spatial flux distribution (global) - Rake probe ExB flux amplitude (local)
Illustration for 3 different plasma scenarios :
Fairly good agreement between both independent measurements
ExB flux highly asymmetric (?)
global
local
global
local
global
local
II
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 22 /26
Fast imaging: evidence of asymmetry
HFS injectionexp ~ 20 µs
LFS injectionexp ~ 20 µs
HFS LFS
Gas injection performed on HFS and LFS increase the visible emission
pictured at 50kHz
Plasma filaments are observed on LFS to propagate outward
They are not observed on the HFS
conciliate previous assumptions
II
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 23 /26
Interpretation of multi-diagnostic investigation
Particle transport in SOL : Particle transport in SOL :
- ExB convection of plasma “filaments”
51//// L usual flute mode paradigm //// L
- consistent with interchange instability mechanisms (localization + extent)
- highly asymmetric around the plasma :
- centered @ outboard midplane
- finite // extent
- drive near-sonic // flows around the confined plasma
Necessity to consider a 3D model of filament dynamics
Vr ~ 1% cS
V// ~ 100% cS
Vr ~ 1% cS
V// ~ 100% cS
II
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 24 /26
SteadySteady--statestate picturepicture snapshotsnapshot MagneticMagnetic reconstructionreconstruction
LCFSLCFS
Picture of filaments in the core !
• Other experiment : stationary fully detached plasmas (3-4 sec.)Other experiment : stationary fully detached plasmas (3-4 sec.)
+ local conditions ( + local conditions ( * , * , P P ) similar to SOL) similar to SOL
--> emissive ring in the confined region (r/a ~0.5 )--> emissive ring in the confined region (r/a ~0.5 )
Again,Again, (largest)(largest) field alignedfield aligned structures only on thestructures only on the Low Field SideLow Field Side
filaments filaments k k//// > 0 + open / closed field lines > 0 + open / closed field lines
II
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 25 /26
Implications of the results
Database of strong evidences about edge plasma phenomena(flows, decay length, fluctuations)
Case base for new code benchmarking (MISTRAL project)
Coupling of turbulence & edge flows with core rotation shear layers
Revisiting the theoretical description & models of edge transport
flute modes = 2D full 3D (ESPOIR project)
3D description obtained on Tore Supra applicable to divertor machinescoherent with other evidencesconciliate apparent incoherenciesL-mode : LIMITER DIVERTOR
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 26 /26
Summary Experimental investigation of edge transport :
About diagnostics : - interpretation of experimental data
improving probe geometry for // flow measurements improving probe geometry for // flow measurements
- multi-diagnostic consistency
critical issues on the spatial sampling of fluctuationscritical issues on the spatial sampling of fluctuations
projection artifacts with visible imagingprojection artifacts with visible imaging
local & global measurementslocal & global measurements
About transport model :
- mechanisms driving the // flows radial flux
- conservation laws help from simulation (SOLEDGE2D)
About experiments : + a posteriori checking
- Experimental proposals dedicated to specific issues
- Check the consistency of results with a variety of experiments
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 27 /26
Ionization source in the SOL
50-50 0R (cm)
-60
-40
-20
0
20
40
60
Z (c
m)
0
0.5
1
1.5
2
(1022)
50-50 0R (cm)
-60
-40
-20
0
20
40
60
Z (c
m)
0
0.5
1
1.5
2
(1022)
• Monte-Carlo simulation of recycling on main limiter : EIRENE simulation
• 3D domain ( toroidal symmetry)
• Initial input (experiment) : ion fluxes @ limiter plates (from Mach probe) ne + Te + Ti profiles (SOL + confined region)
• Complete database for Deuterium atomic reactions
• Self-consistent matter balance
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 28 /26
*//// )( vnvnvn E
rrFlux balance :
)( nv E
Transversal drifts in SOL flux balance
Simplified flux balance :
rrS
raS Bc
EqMcn
////
|M//| ~ 1
- large aspect ratio-Er independent of
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 29 /26
Pressure conservation
//2
//22 vvvn cn vn rrS////
radial transfer of // momentum
Spatial mapping of r
spatial mapping of & //vrv
Computable Reynolds stress
P/P < 15 %
! But only linear term !
Validation with simulationSOLEDGE2D G. Ciraoloa & H. Bufferand
(only viscosity)
P/P < 10 %
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 30 /26
Flow reversal experiment
M||
BT
IP
M||
BT
IP
probe
M//r
LFSHFS
l//
LFSHFS
probe
M//
r
l//
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 31 /26
3D filaments : revisiting momentum transfer
Vr ~ 1% cS
V// ~ 100% cS
Vr ~ 1% cS
V// ~ 100% cS
LIM
ITE
R
vr
r
l//
FIRST WALLFIRST WALL
LIM
ITE
R
LFSHFS
v//
ttrtr vvvv //// Issue in understanding SOL flow effect on core rotation
transfer of v//
1-ms30
rV
1-ms 300
rV
rv
• // dynamic of a single “filament”
// front expansion ? Scv //
coupling with local ExB fluctuations along the field line ?
computable from previous results
average on flux surface : NO RESIDUAL TRANSFER
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 32 /26
SOL flow and core rotation M||
BT
IP
co-Ip
M||
BT
IP
ct-Ip
co-IP
ct-IP
flow reversal in SOL plasma for similar core plasma
change in core velocity fields
V V
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 33 /26
More experimental implications for Tore Supra
1. Heat load asymmetry on the main limiter Y. Corre & al.
2. Plasma environment of wave launchers (LH) M. Preynas, A. Ekedahl coupling efficiency (gradients in front of antennae) suprathermal electron generation V. Fuchs, J. Gunn, A. Ekedahl
3. More physics about fuelling by gas injection or pellets
4. Precise flow pattern in SOL plasma Carbon migration & deposition
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 34 /26
List of contributionsFirst author publications :
N. Fedorczak, J.P. gunn, Ph. Ghendrih, P. Monier-Garbert, A. PocheauFlow generation and intermittent transport in the scrape-off layer of the tore Supra tokamakFlow generation and intermittent transport in the scrape-off layer of the tore Supra tokamakJournal of Nuclear Materials 390–391 (2009) 368–371Journal of Nuclear Materials 390–391 (2009) 368–371
N. Fedorczak, J.P. gunn, Ph. Ghendrih, G. Ciraoloa, H. Bufferand, L. Isoardi, P. Tamain, P. Monier-Garbet,Experimental investigation on the poloidal extent of the turbulent radial flux in tokamak Experimental investigation on the poloidal extent of the turbulent radial flux in tokamak scrape-off layerscrape-off layerJournal of Nuclear Materials (2010)Journal of Nuclear Materials (2010)
Oral contribution to international conferences :
Ballooned like transport in the SOL of Tore Supra tokamak : evidences and propertiesBallooned like transport in the SOL of Tore Supra tokamak : evidences and propertiesTransport Task Force meeting (TTF2009) San Diego Transport Task Force meeting (TTF2009) San Diego
Poloidal mapping of turbulent transport in SOL plasmasPoloidal mapping of turbulent transport in SOL plasmasPlasma Surface Interaction meeting (PSI2010) San Diego Plasma Surface Interaction meeting (PSI2010) San Diego
A first comparison between probes, fast imaging, and Doppler backscattering synchronous A first comparison between probes, fast imaging, and Doppler backscattering synchronous measurements of edge turbulence in Tore Suprameasurements of edge turbulence in Tore SupraEuropean Plasma Society (EPS2009) Sofia European Plasma Society (EPS2009) Sofia (F. Brochard & N. Fedorczak) (F. Brochard & N. Fedorczak)
Nicolas Fedorczak PhD defence 24/09/2010Nicolas Fedorczak PhD defence 24/09/2010 35 /26
Many thanks toTore Supra pilots
Physicists
Technical support :
F. Saint-Laurent, P. Hertout, D. douai, Ph. Moreau F. Saint-Laurent, P. Hertout, D. douai, Ph. Moreau
Jamie Gunn, P. Hennequin, L. Vermare, P. Monier-Garbet, P. Devynck, F. Jamie Gunn, P. Hennequin, L. Vermare, P. Monier-Garbet, P. Devynck, F. ClairetClairetC. Reux, D. Villegas, M. Kocan, X. Garbet, Ph. Ghendrih, Y. Sarazin, P. C. Reux, D. Villegas, M. Kocan, X. Garbet, Ph. Ghendrih, Y. Sarazin, P. Tamain Tamain
J.Y. Pascal, B. Vincent, F. Leroux, T. Alarcon, N. Seguin, V. J.Y. Pascal, B. Vincent, F. Leroux, T. Alarcon, N. Seguin, V. NegrierNegrier
friendsMatthieu, Sara, Sebastien, Vincent, Yannick, Matthieu, Clement,Matthieu, Sara, Sebastien, Vincent, Yannick, Matthieu, Clement,
Sophie, Daniel, Gaëlle, Etienne, Cédric, Victor, Gwen, Ronan, Rémi, Matthieu,Sophie, Daniel, Gaëlle, Etienne, Cédric, Victor, Gwen, Ronan, Rémi, Matthieu, Mélanie, François, Joao, Tom, Magwa, Sparrow,Mélanie, François, Joao, Tom, Magwa, Sparrow,
Mélissa, Mai, Caro, Clemence, Dimitri,Mélissa, Mai, Caro, Clemence, Dimitri, Vanessa, Julien, Lana, Alexis, Uron, Suk-ho, TimoVanessa, Julien, Lana, Alexis, Uron, Suk-ho, Timo
G. Ciraolo, L. Isoardi H. Buferand, E. Serre, G. Ciraolo, L. Isoardi H. Buferand, E. Serre, G. Bonhomme, F. Brochard, M. Farge, R. Nguyen, A. Pocheau, G. G. Bonhomme, F. Brochard, M. Farge, R. Nguyen, A. Pocheau, G.
SearbySearby
collaborators
and my family