time-dependent modelling of elming h-mode at tcv with solps
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Barbora Gulejová 1 of 2EPS 2007 material 20/6/2007
Time-dependent modelling of ELMing H-mode at TCV with
SOLPS
Barbora Gulejová, Richard Pitts, Xavier Bonnin, David Coster, Roland Behn, Jan Horáček, Janos Marki
OUTLINE
* SOLPS code package* ELM simulation – theory* Simulation of the ELM* Comparison of SOLPS with experiment
Barbora Gulejová 2 of 2EPS 2007 material 20/6/2007
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 3 of 2EPS 2007 material 20/6/2007
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 500 J JET 200kJ ITER 8-14 MJ => unacceptable =>
Small ELMs on TCV – same phenomena !=> Used to study SOL transport
W~600J
Dα
Barbora Gulejová 4 of 2EPS 2007 material 20/6/2007
Type III Elming H-mode at TCVType III Elming H-mode at TCV[k
A]
ne
Ip
Dα
Vl
Wheat[kW
][V
][a
u][1
018
m3 ]
# 26730
Type III ELMs
# 26730
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
Ip = 430 kA, ne = 6 x 1019 m-3 , felm = 230 Hz
ELMs - 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
Barbora Gulejová 5 of 2EPS 2007 material 20/6/2007
upstream targets
Jsat [A.m-2]LP, averageSOLPS
outerinner
Te [eV]
ne [m-3]
Perp.heat flux [MW.m-2]
LP, averageSOLPS
outer
inner
IR
r-rsep r-rsep
r-rsep
v [m.s-1]
D [m2.s-1]Χ [m2.s-1]
same solps result!
Vperp=0
Ansatz
D┴,Χ┴ = radially constant in divertor legs
D┴= 3 m2.s-1 in div.legs1m2.s-1 in SOLΧ┴= 5 m2.s-1 in div.legs6 m2.s-1 in SOL
NO DRIFTS here But simulations
with DRIFTs show early promise of
expected effects
**
Simulation of pre-ELM = steady state of H-mode presented at PSI 17, Hefei,China and published in JNM May 2006
Very good overall
match Good basis for time-dependentELM simulation
<=>Pre-ELM must be
time-dependent too!+
equal time-steps for kinetic and fluid
parts of code ~ 10-6s
**
Barbora Gulejová 6 of 2EPS 2007 material 20/6/2007
Simulation of ELM Simulation of ELM
Ddr
dnT
dr
dTn
At
E
ELMELM
ELM ..2
5..
..2
* Instantaneous increase of the cross-field transport parameters D┴, ┴, v┴!
1.) for ELM time – from experiment coh.averaged ELM = tELM = 10-4s2.) at poloidal location -> expelled from area AELM at LFS
From the cross-field radial transport can be estimated the combination of transport parameters corresponding to the given expelled energy WELM, tELM and AELM
D┴
Many different approaches possible =>changes in D┴, ┴ only or in v┴ too …
time
W~600J
Dα
AELM= 1.5m2
W = 600 J
Conv.[eV.m-2.s-1]
Diff.[eV.m-2.s-1]
┴
D ┴
*
LFSHFS
Barbora Gulejová 7 of 2EPS 2007 material 20/6/2007
Tools to simulate ELM in SOLPS
outer div.leg
main SOL
main SOLInner div.leg
Several options in SOLPS transport inputfiles :
* Multiplying of the transport coefficients in the specified poloidal region
* In 3 different radial regions (core, pedestal, SOL) by different multipliers
Added new options: * Poloidal variation of the multiplicator
* Step function
* Gaussian function
* Choosing completely different shape of
radial profile for chosen poloidal region
pedestal wallcore
No TB
preelm
ELM
x M
ELM
Barbora Gulejová 8 of 2EPS 2007 material 20/6/2007
Simulation of ELM Experimental data to constrain the code: * Energy expelled by the ELM through
separatrix (DML) ~ 600 J* Time of ELM-rise (D coavelm) ~ 100 μs
* Jsat at the targets * Heat flux at outer target (IR soon)
* Upstream ne,Te (TS) -> just orientation
Barbora Gulejová 9 of 2EPS 2007 material 20/6/2007
Simulation of ELM - resultsUpstream profiles
ne [m-3] ne [m-3]
Te [eV] Te [eV]
r-rsep
r-rsep
D,Chi (ELM): Same shape as preELM => TB, Just multiplied D x 100, Chi x 8
D,Chi (ELM): smaller TB+ Gaussian function poloidally
D, Chi increased only locally !
Barbora Gulejová 10 of 2EPS 2007 material 20/6/2007
Comparison with TS – R.Behn
TS measurements (R.Behn) =>* Drop in pedestal width and height appears only for ne
SOLPS * bigger pedestal collaps * higher ne and Te in SOL
But the right tendency – pedestal collapse
D┴
ne
R-Rsep
R-Rsep
time
time
Time evolution of D┴ and ne
tELM=100 µs
ne
Te [eV]
+ different ELMing H-mode shots !
TB
TBno TB
no TB
Barbora Gulejová 11 of 2EPS 2007 material 20/6/2007
Simulation of ELM - resultsTarget profiles D,Chi (ELM): smaller TB
+ Gaussian function poloidally
“removal” of TB => higher values at the targets
LP coav data
SOLPS
SOLPSinner
outer
targets targets
inner
innerouterouter
D,Chi (ELM): Same shape as preELM => TB, Just multiplied D x 100, Chi x 8
27
1622
30
35
40
Jsat [A.m-2]
Jsat [A.m-2]
preELMELM
preELMELM
preELMELM
Jsat [A.m-2]
Te [eV]
ne [m-3]
Jsat [A.m-2]
Te [eV]
ne [m-3]
Barbora Gulejová 12 of 2EPS 2007 material 20/6/2007
Simulation of ELM - results Target profiles – Heat fluxes
D,Chi (ELM) :Same shape as preELM => TB, just multiplied D x 100, Chi x 8
D,Chi (ELM): smaller TB + Gaussian function poloidally
outer outer
inner inner
Time-dep. heat flux estimated from LP measurements at outer target
R.Pitts, Nuc.Fusion 2003
Like Jsat, Te, and ne, heat flux is higher for the case with smaller TB
IR data available soon (J. Marki)
2016
9
Barbora Gulejová 13 of 2EPS 2007 material 20/6/2007
ELM-Time evolution of jsat at targets
Inner
outer target
Dα
Jsat [A.m-2]
SOLPS
SOLPS
LP 5
LP 20
post-ELM
ELM
pre-ELM
pre-ELMELMpost-ELM
R.Pitts, Nuc.Fusion 2003
Barbora Gulejová 14 of 2EPS 2007 material 20/6/2007
ELM-Time-dependent solution at targets ELM
Jsat [A.m-2]
Te [eV]
Ti [eV]
ne [m-3]
targetsinner outer
time [s]
midplane separatrixTB during ELM TB during ELM
Jsat [A.m-2]
Te [eV]
Ti [eV]
ne [m-3]
Density is fixed at midplane separatrix => can’t change too much at the targets either => Jsat can increase mostly through Te,Ti => Necessary to increase D more then Chi in order to act on increase of ne
time [s] time [s]
Barbora Gulejová 15 of 2EPS 2007 material 20/6/2007
ELM-time-evolution of jsat at targetstargets
innerouter
time [s] time [s]
Jsat [A.m-2] Jsat [A.m-2]
ELM rise time
SOLPSSOLPS
LP 20LP 5Compared with LP close to strike point => Not exactly the sameposition
Barbora Gulejová 16 of 2EPS 2007 material 20/6/2007
Timedependence of target Te,Ti
Timedependence of simulated Te,Ti (D.Tskhakaya) for 120kJ ELM at JET (sheat heat coeff assumed 8)
R.Pittts, IAEA,2006
outerinner
Te [eV]Te [eV]
Ti [eV]Ti [eV]
SOLPS
Te is rising quicker then Ti
Propagation down to the target from upstream pedestal
Barbora Gulejová 17 of 2EPS 2007 material 20/6/2007
Timedependence of target Te,Ti
Ions are arriving to target later then electrons (~16 μs) In reality should be more, but :1.) probably more collisional 2.) SOLPS – equipartition of energy between ions and electrons
=>
reasonable shift of Te,Ti peaks
outerinner
Te [eV]
Ti [eV]
SOLPSELM ‘end’ ELM ‘end’
peak
peak
R.Pittts, IAEA,2006
Barbora Gulejová 18 of 2EPS 2007 material 20/6/2007
Thank you for attention
Barbora Gulejová 19 of 2EPS 2007 material 20/6/2007
But not at strike point!!
Probably more collisional
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