Impurity transport analysis & preparation of W injection experiments on KSTAR
Impurity Transport in the Edge Transport Barrier of ASDEX Upgrade H-Mode Discharges
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Transcript of Impurity Transport in the Edge Transport Barrier of ASDEX Upgrade H-Mode Discharges
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Impurity Transport in the Edge Transport Barrier of ASDEX Upgrade
H-Mode Discharges
R. Dux, T. Pütterich, M.A. Janzer, R.M. McDermott and the ASDEX Upgrade Team
MPI für Plasmaphysik, EURATOM Assoziation, Garching bei München
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 2
Central tungsten density depends on…
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 3
Central tungsten density depends on…
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 4
W- and C-density pedestal vs. ELM frequ.
Scan in D-puff rate changes ELM frequency
Lower ELM frequency leads to more nW inside pedestal
nC increases less strong with ΔtELM than nW
Need to know inter-ELM transport in ETB to understand effect of ELMs
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 5
Overview
Measurements of the impurity transport in the ETBusing CXRS measurements – Z-dependent
Consequences for transport of W- 1D Transport/Erosion Model for W- results for AUGD and ITER
Summary
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 6
Toroidal edge CXRS system at AUGD
• spatial resolution: 3 mm
• temporal resolution 1.9 ms
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 7
STRAHL
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 8
Scheme of Transport Evaluation
1D-Transport Model
STRAHL
Electron profiles,Geometry, Atomic Data
Fitting procedure
input
Measured impurity profiles
compare
Vary
A1,A2
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 9
Inputs for Modeling the Impurity Transport
Electron profiles and Edge-CXRS during type-I ELMy H-mode
Profiles are adjusted by a two-point model for power balance (i.e. Te =85eV at separatrix)
Analysis in inter-ELM phase
Time [s]
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 10
Model finds good match for impurity profiles
Profiles are well described, except 1ms after ELM (filaments, ELM-model) Pedestal in C6+ is mainly due to pedestal in total C density Separation of v and D possible due to:
(1) modulation by ELM and (2) position of gradient
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 11
Fitted values of v, D and v/D agree with neoclassical transport
D and v are separated, but with relative large uncertainties
v/D is determined well by the gradients and the pedestal height, i.e. pedestal peaking factor
(In equilibrium, w/o sources)
Neoclassical transport (NEOART) is matched for v/D, (NEOART is equivalent to NCLASS)
Neocl. approximation valid for impurities; mostly PS, negligible banana, plateau contribution
97.0
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)97.0( pol
pol
drD
v
n
nF
polC
polC
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 12
Neoclassical transport for He, C, Ne and Ar
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 13
Neoclassical transport for He, C, Ne and Ar
Impurity scan gives stronger inward convection for higher charge
Implications: every impurity has a different gradient
W has even higher Z in ETB higher * and collisional diffusion coefficient stronger peaking
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 14
Overview
Measurements of the impurity transport in the ETBusing CXRS measurements – Z-dependent
Consequences for transport of W- 1D Transport/Erosion Model for W- results for AUGD and ITER
Summary
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 15
Model for Radial Transport of Tungsten during ELM cycle
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 16
Modeled W profile evolution during ELM cycle
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 17
Increase of prompt redeposition during ELM:
immediate return to surface during first gyration
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 18
Study dependence of confinement time of W
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 19
Confinement time of W depends on ELM frequency and parallel loss time
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 20
Code results for three AUG H-mode plasmas with f_ELM=50,100 and
200Hz
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 21
ITER: much lower collisional transport due to higher temperature and B-field
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 22
ITER: low W peaking in ETB for relevant ELM frequency range
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 23
Summary
For type-I ELMy H-mode, inter-ELM impurity transport at the barrier is neoclassicalAbsolute values of v and D agreeNeoclassical Z-scaling is observed strong inward pinch
A multi-impurity transport/erosion code was developed combining the transport in the edge barrier and wall erosion including effects of ELMsAUG: consistent description of including all experimental dataimpurity peaking in ETB of ITER very weak for relevant ELM
frequencies
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R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 24
Outboard limiters most important source
R-sweep modulates outboard W-source
Large divertor source does not play a role
cW reacts strongly to the limiter source
R. Dux et. al., I-6 , PSI 2008, JNM 390-391, 858