Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 1 of 12 Centre de Recherches en Physique des Plasmas SOLPS5 modelling of ELMing H-mode on TCV Barbora Gulejová, Richard Pitts, Marco Wischmeier, Roland Behn, Jan Horáček OUTLINE * * * * * * Edge plasma – SOL - terminology Why is understanding of ELM important? SOLPS 5 code package (B2 - EIRENE) Theoretical model of simulation Comparison of experimental data with simulati Strategy for next step: simulation of ELM its
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Barbora Gulejová 1 of 12 Centre de Recherches en Physique des Plasmas SPS Annual Meeting in Lausanne, 14/2/2006 SOLPS5 modelling of ELMing H-mode on TCV.
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Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 1 of 12
Centre de Recherches en Physique des Plasmas
SOLPS5 modelling of ELMing H-mode on TCV
Barbora Gulejová,
Richard Pitts, Marco Wischmeier, Roland Behn, Jan Horáček
OUTLINE
******
Edge plasma – SOL - terminology Why is understanding of ELM important? SOLPS 5 code package (B2 - EIRENE) Theoretical model of simulation Comparison of experimental data with simulation Strategy for next step: simulation of ELM itself
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 2 of 12
•Scrape-off layer (SOL)–Cool plasma on open field lines–SOL width ~1 cm ( B)–Length usually 10’s m (|| B)
Poloidal cross-section
Outer•ITER will be a divertor tokamak
•Divertor–Plasma guided along field
lines to targets remote from core plasma: low T and high n
Inner
Last closedflux surface
LFSHFS
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 3 of 12
Centre de Recherches en Physique des Plasmas
Edge localised mode (ELM)Edge localised mode (ELM)H-mode Edge MHD instabilities Periodic bursts of particles and energy into the SOL
- leaves edge pedestal region in the form of a helical filamentary structure localised in the outboard midplane region of the poloidal cross-section
LFSHFS
divertor targets and main walls erosion first wall power deposition
ELMing H-mode=baseline ITER scenario
Energy stored in ELMs: TCV 200 J JET 200kJ ITER 8-14 MJ => unacceptable =>
W~200J
Dα
Small ELMs on TCV – same phenomena !=> Used to study SOL transport
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 4 of 12
Centre de Recherches en Physique des Plasmas
SScrape-crape-OOff ff LLayer ayer PPlasma lasma SSimulationimulation Suite of codes to simulate transport in edge plasma of tokamaks
B2B2 - solves 2D multi-species fluid equations on a grid given from magnetic equilibrium
EIRENE EIRENE - kinetic transport code for neutrals based on
Monte - Carlo algorithm
SOLPS 5SOLPS 5 – coupled EIRENE + B2.5
Main inputs: magnetic equilibrium Psol = Pheat – Prad
core upstream separatrix density ne
Free parameters: cross-field transport coefficients (D┴, ┴, v┴)
B2 plasma background =>recycling fluxes
EIRENE
Sources and sinks due to neutrals and molecules
measured
systematicallyadjusted
Mesh
72 grid cells poloidallyalong separatrix
24 cells radially
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 5 of 12
Centre de Recherches en Physique des Plasmas
Elming H-mode at TCVElming H-mode at TCV
[kA
]
ne
Ip
Dα
Vl
Wheat[kW
][V
][a
u][1
018
m3 ]
# 26730
Type III ELMs
# 26730ELMs - too rapid (frequency ~ 200 Hz) for comparison on an individual ELM basis => Many similar events are coherently averaged inside the interval with reasonably periodic elms
Pre-ELM phase = steady state
ELM = particles and heat are thrown into SOL ( elevated cross-field transport coefficients)
Post-ELM phase
tpre ~ 2 ms
telm ~ 100 μs
tpost ~ 1 ms
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 6 of 12
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 7 of 12
Centre de Recherches en Physique des Plasmas
Theory – steady state simulationTheory – steady state simulationCross-field transport coefficientsCross-field transport coefficients
nrDeff ).(
nvdr
dnD
))(5( nvdr
dnDT
dr
dTnq
Cross-field radial transport in the main SOL - complex phenomena
Ansatz:( D┴, ┴, v┴) - variationradially – transport barrier (TB)poloidally – no TB in div.legs
outer div.leg
┴
SOL
div.legs
sep
D┴
SOL
div.legs
sep
v┴ SOL
div.legs
sep
main SOL
diffusion (D┴) + convection (v┴)
SOL radial heat fluxheat flux:
SOL radial particle fluxparticle flux:
main SOL
Inner div.leg
x
x
Pure diffusion: v┴=0 everywhere
More appropriate: Convection
simulations with D┴= D┴class in progress
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 8 of 12
Centre de Recherches en Physique des Plasmas
Comparison of experimental data with simulationComparison of experimental data with simulationPurely Purely diffusivediffusive approach approach
1.step: Only radial variation of D┴, ┴
upstream
targets
Excellent agreement !!!Excellent agreement !!!
Code overestimates data
=>
Poloidal variation necessary
=>
Remove transport barrier from divertor legs
=>
=>
outer
Jsat [A.m-2]
LPs
SOLPS
R-Rsep [m]
innerjsat
R-Rsep
LPs
SOLPS
D┴,Χ┴ = constant in div. legs
ne
D┴
TS
RCP
SOLPS
pedestalwall
Te
Χ┴
TSRCP
SOLPS
R-Rsep
R-Rsep
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 9 of 12
Centre de Recherches en Physique des Plasmas
Removing transport barrier from divertor legsRemoving transport barrier from divertor legs
It appears that a description of cross-field transport in divertor as radially constant is more appropriate
D = = const. - same value in both divertor legs !
Outer target – better agreement obtained!
LP
Inner target
R-Rsep [mm]
LP
jsat [A.m-2]
R-Rsep [mm]
jsat [A.m-2]
Transport barrier
0.5
1
2
3
56
Transport barrier
0.5
1
2
3
5
6
outer target
inner target
LP
6 m2.s-1 in div.legs1m2.s-1 in SOL ! NO DRIFTS !
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 10 of 12
Centre de Recherches en Physique des Plasmas
Other issues to considerOther issues to consider
1.) Inner and outer divertor leg assymetry – inner is much shorter2.) Private flux region (PFR) rescaling in div.legs – different processes in PFR region and SOL region of divertor legs3.) Ballooning – (Btot/Bloc )α => poloidal variation
Inner div.leg
outer div.leg
sep
PFR
SOL
**
*Sensitivity study for the steady state Sensitivity study for the steady state simulationssimulations
=>
Very small effect
LP
α =0.5
α =1
outer target
R-Rsep [mm]
No ballooning
LP
Inner target
R-Rsep
α =0.5
α =1
inner target
No ballooning
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 11 of 12
Centre de Recherches en Physique des Plasmas
Next step : Next step : ELMELM
Instantaneous increase of the cross-field transport parameters! Strong poloidal variation - localized on outboard midplane of TCV
Requires time-dependent iteration in code - much bigger problem !
Simulations in progress…
Barbora Gulejová SPS Annual Meeting in Lausanne, 14/2/2006 12 of 12
Centre de Recherches en Physique des Plasmas
*
*
*
*
*
First attempt to simulate Scrape-Off layer in H-mode on TCVwith aim to simulate Type III ELMs
Simulations conducted using coupled fluid-Monte Carlo (B2-EIRENE) SOLPS5 code constrained by upstream profiles of ne and Te and at the targets profiles of jsat
Using exp. data as a guide to systematic adjustments of perpendicular particle and heat transport coefficients
Code experiment agreement ONLY possible if transport coefficients are varied radially AND polloidally
Excellent match obtained for inter-ELM phase good basis for simulation of ELM itself (in progress)