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
Feb 04, 2016
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
R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 2
Central tungsten density depends on…
R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 3
Central tungsten density depends on…
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
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
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
R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 7
STRAHL
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
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]
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
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
00.1
exp)00.1(
)97.0( pol
pol
drD
v
n
nF
polC
polC
R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 12
Neoclassical transport for He, C, Ne and Ar
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
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
R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 15
Model for Radial Transport of Tungsten during ELM cycle
R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 16
Modeled W profile evolution during ELM cycle
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
R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 18
Study dependence of confinement time of W
R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 19
Confinement time of W depends on ELM frequency and parallel loss time
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
R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 21
ITER: much lower collisional transport due to higher temperature and B-field
R. Dux, JET-E1/2 TF Meeting, Culham, 7.4.2011 - 22
ITER: low W peaking in ETB for relevant ELM frequency range
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
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