Modeling hydrocarbon generation / transport In fusion experiments John Hogan Fusion Energy Division Oak Ridge National Laboratory First Meeting Co-ordinated Research Program ” Atomic and Molecular Data for Plasma Modelling ” IAEA Vienna International Centre September 26-28, 2005
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Modeling hydrocarbon generation / transport In fusion ... · Codes in use for erosion/deposition/retention (D Coster, J Hogan PSIF Workshop Summary Nucl Fus 2005) TR - trace impurity
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” Atomic and Molecular Data for Plasma Modelling ”IAEA
Vienna International CentreSeptember 26-28, 2005
ITER tritium retention issues G. Federici, ITER GWS PSIF Workshop*
(to be published, Physica Scripta)
ITER predictions still uncertain due to – chemical erosion yields at high temperature and fluxes – effects of type I ELMs (ablation)– effects of gaps– effects of mixed materials– lack of code validation in detached plasma.
• T issues will be heavily scrutinised by licensing authorities.
• Scale-up of removal rate required is 104.• Potential options for T removal techniques for ITER.
1) Remove whole co-deposit by:
• oxidation (maybe aided by RF)• ablation with pulsed energy (laser or flashlamp).
2) Release T by breaking C:T chemical bond:• Isotope exchange • Heating to high temperatures e.g. by laser, or ...
* “New directions for computer simulations and experiments in plasma–surface interactions for fusion”: Report on the Workshop (Oak Ridge National Laboratory, 21–23 March 2005) J.T. Hogan, P.S. Krstic and F.W. Meyer Nucl Fus 49 (2005) 1202
Fusion applications of hydrocarbon rate data
Erosion / re-deposition / tritium retention
(DIII-D, Tore Supra, JET examples)
- long discharges -> hydrocarbon films
- chemical erosion and T inventory
Use of presently available data
PISCES linear reflex arc (Erhardt-Langer)
throat of Tore Supra neutralizer
(compare E-L and Janev - Reiter)
DIII-D gaps
ELMs
a. 2/3D Kinetic codes
Code WBC ERO BBQ DIVIMP DORIS MCI EDDY
Geometry 3D 2/3D 3D 2D 3D 2D 3D
Model TR TR TR TR TR TR TR
Dynamics GO GO GC GO GC GO GC
b. 2D fluid codes
Code SOLPS EDGE2D UEDGE
Geometry 2D 2D 2D
Model SC SC SC
Dynamics FL FL FL
Codes in use for erosion/deposition/retention (D Coster, J Hogan PSIF Workshop Summary Nucl Fus 2005)
TR - trace impurity in fixed backgroundSC - self-consistent background and impurity solution
GO - gyro orbit following (classical diffusion)GC - guiding center fluid (anomalous transport)FL - fluid + kinetic corrections
CD / CH Molecular Band is analyzed todetermine the H/D concentration in the divertor(G. Duxbury - Univ Strathclyde)
Schematic diagram of experiment onTore Supra Midplane Limiter (Phase II)
E Gauthier, A Cambe J Hogan et alJ Nucl Mater 2003
Model comparison using partial pressure- sensitivity to sputtering model
CD emission
CD4 partial pressure
510 670 830 Tsurf(K)
LHCD: High Tsurf
PCD4∝ PD20.70
(N. Hosogane)
PCD4∝ϕD0.73
JT-60U
Increased productionof CD4 with flux
Deuteron impact charge exchange data [Alman, Ruzic]D+ + CnDm --> D + CnD4+
Reaction Product Rate Known (10-9 cm3/s) (total)
CD4D+ + CD4 D + CD4
+ 1.880 4.150D2 + CD3
+ 1.880D+ + CD3 D + CD3
+ 1.800D2 + CD2
+ 1.800D+ + CD2 D + CD2
+ 1.700D2 + CD+ 1.700
D+ + CD D + CD+ 3.236C2D2D+ + C2D2 D + C2D2
+ 2.250 6.300 D2 + C2D+ 2.250
D+ + C2D D + C2D+ 4.358
C2D2 C2D2+ C2D+ C2+
Heavy hydrocarbon production: dominant species frombreak-up of C2D2.BBQ calculation using Alman-Ruzic database
Janev-Reiter database rates have been implemented in BBQ. A comparison, with the same background plasma conditions, for the Tore Supra pump limiter case, shows significant differences in comparison with the Erhardt-Langer rates
CH+ CH+ CH+
CH4 CH4 CH4
ne,LP= 2 1018 m-3
Te,LP= 20 eV Te,LP= 10 eV Te,LP= 5 eV
Janev-Reiter profiles
TeLP = 20 eV
ne,LP = 2 1018 m-3
E - L
J - R
CH+ density
Axial distance (m)0.04 0.08 0.12 0.16 0.20 0.24
TeLP = 10 eV
TeLP = 5 eV
CH+ density
Axial distance (m)0.04 0.08 0.12 0.16 0.20 0.24
E - L
J - R
Axial distance (m)0.04 0.08 0.12 0.16 0.20 0.24
CH+ density
E - L
J - R
CH+ CH+ CH+
CH4 CH4 CH4
ne,LP= 6 1018 m-3
Te,LP= 20 eV Te,LP= 10 eV Te,LP= 5 eV
Janev-Reiter profiles
TeLP = 20 eV
ne,LP = 6 1018 m-3
E - L
J - R
CH+ density
Axial distance (m)0.04 0.08 0.12 0.16 0.20 0.24
TeLP = 10 eV
TeLP = 5 eV
CH+ density
Axial distance (m)0.04 0.08 0.12 0.16 0.20 0.24
E - L
J - R
Axial distance (m)0.04 0.08 0.12 0.16 0.20 0.24
CH+ density
E - L
J - R
Given D+ flux (or Cn+for self-sputter) to surface and surfacetemperature, calculate impuritytype, rate and velocitydistribution .
Mechanisms: - physical sputtering, - chemical sputtering (thermal, athermal) - RES
Impurity generationmodels
0.09
0.045
0.0250 875 1500 Tsurf (K)
Te (eV)103050
70 90
9070
50
30Te (eV)
Chemical
RES
Yield[C / ion ]
Surface-temperature dependence of chemical and RES yields forTe=10 -> 90 eV.
- self-consistent heat flux (includes SEE, thermionic emission)
- local impurity redeposition generation due to Tsurf-dependent mechanisms as well as physical sputtering
- ablation cooling (Vieder model)
RDP-2000RDP-1999
0.4 0.6 0.8 1.0 1.2 1.4 Time (s)
3
8
0
0
Carbon concentration (%)Edge
Core
Filterscope(schematic)
0001
0203
0411
13
12
DIII-D intrinsicimpuritiesbefore/after new tileinstallation
Some evidence ofT-dependentprocesses
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 Time (s)
NBI
Maximum Tsurfon heated surface
T sur
f(K)
2.5 mm
1 m
m
Ychem @ t ~ 4swhen Tmax = 1010K
Ychemmin = 1. 10-2
Ychemmax = 0.14
C flu
x(1
018
parts
/cm
2 /s)
0 1 2 3 4 5 Time (s)
0.4
0.8
1.2
1.6
0 NBI
C flu
x(1
018
parts
/cm
2 /s)
0.6
1.0
1.6
2.0
00 1 2 3 4 5 Time (s)
NBI
RES
Chemical
NBI
CASTEM-2000 simulation of time-dependent carbon generationfrom simulated DIII-D localized source
edge / pedestal only,low-field side only
Semi-empirical model for ELM transport enhancement
Green: ELM-affected region in the model
Red: C neutrals and ionsYellow: D neutrals ion ions
1
2
34
ELM event
time
radius
1
2
3
separatrix
Transport time dependence(schematic)1. Pre-ELM (barrier)2. Strong enhancement (100 µsec) ELM3. Loss of barrier, 2 x pre-ELM value4. reducing to pre-ELM value as barrier is re-established
Intra-ELM transport radial dependence(schematic)1. barrier2. enhancement toward SOL3. SOL radial transport
Inner leg pre-ELM detached during attached re-detaching after recovery of detachment
DIII-D experimental:fast (CID) camera
CIII evolution:M Groth et al,J Nucl Mater 2003
Modeling
solps 5.0 / Eirene99
IPP-Garching/Greifswald, FZ-Juelich
Solps simulation of
CIII emission
seen by 240par
(lower divertor)camera
W Meyer,
M Fenstermacher,
M Groth
LLNL
ELM heat flux mitigation byInjection of extrinsic impurities
10 100 1000
0.1
1
10
chem
ical
spu
tterin
g yi
eld
(per
ion)
energy (eV)
N+2
Ar+
Ne+
He+
H+2 = 2 H+
Flux ratio H/ion = 400
Chemical sputtering of carbon materials due to combined bombardment by ions and atomic hydrogen W Jacob, C. Hopf, M. Schlüter, T. Schwarz-SelingerMax-Planck-Institut für Plasmaphysik Garching
CONCLUSIONS
Intrinsic (carbon) impurity sources play a key role in ITER, both as regards erosion and fortritium retention
The ITER problem (addressed also by JET) requires a decision about the first wallmaterial - carbon or an alternative
Development of validated models for C generation, deposition and retention requiresexperimental comparison: this typically introduces multiple uncertainties; e.g., sputteringyield models vs hydrocarbon break-up rates
ITER relevant experimental scenarios involve fast timescale ELM events, for whichspectroscopy is an key tool
The importance of hydrocarbon generation processes has been seen in manyexperiments, and thus a quantitative, evaluated, integrated model for break-up processesin the plasma is needed.