modeling hydrocarbon generation / transport in fusion ... · codes in use for...
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Modeling hydrocarbon generation / transportIn fusion experiments
John HoganFusion Energy Division
Oak Ridge National Laboratory
First Meeting Co-ordinated Research Program
” 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)
0
0.1
0.2
0.3
0.4
0.5
0.6
50 52 54 56 58 60
Divertor Spectroscopy Sub-Divertor - PenningCH-CD Spectroscopy
Hydr
ogen
Con
cent
ratio
n
Time (s)
48280
H wall loading first 5 shotsOf D-->H changeover
H concentration as deduced from the CH-CD Molecular Band
Relation between chemical erosion processes and H/D/T retentionJET deuterium - hydrogen change-over experiment
D Hillis, J Hogan et al J Nucl Mater 2001
Interior view of Tore Supra
Tore Supra
Full toroidal limiter CIEL
Θ poloidal direction
ϕ
θ
φ toroidal direction
machine axis
Coupled core/ SOL/PFC code system
CASTEM-TOKAFLU-IMPFLU BBQ
ITC-SANCO-MIST
Self- sputtering iteration
Deuterium sputtering stage
BBQ
MIST/ITC
ne(ρ)Te(ρ)
λΤe
ΓD+
Superstructureleading edgeneutralizer
physicalchemicalRES
ΓCin(Zi)
=> ΓCout(Zi) Core C efflux: D+ - sputtered
BBQ
MIST/ITC => ΓCout(Zi) Core C efflux: self - sputtered C
=> Core C influx Sum over processes and geometries
0.9 0.95 1.0 1.03 1.06 radius (ρ/a)
LCFS
0
1.2
0.6
V VIVII
IVIII
Mid SOL heating< NC >
10 18 m-3
< NC >BBQ carbon densityaveraged over θ, φ
8.8
0
4.4
0 0.5 1.0 ρ ( r/a)
2.3
0
1.15
0
1.5
0.75
1 9 iteration
< NC > (1016 m-3)NC (1016 m-3)
1.05
0
0.525
0 0.5 1.0 ρ ( r/a)
.
NC (1018 m-3)
System evolution forlocalized heating ininner, mid- and far-SOL
for:
- TRIM self-sputter (TOP)
- enhanced self-sputter (BOTTOM)
Tore Supra heat, particle flux deposition is stronglyinfluenced by magnetic field ripple (~7%)
R Mitteau et al J Nucl Mater 2001.
34909 34930Modelled C emission(TOKAFLU / BBQ)
Physical sputtering source
Te,b=35 eV, ne,b=0.67 1019 m-3Pinj-Prad=0.7 MW
Measured CII radiation(E Dufour, C Lowry et al, EPS 2005)
Model validation requires attention to impurity generationfrom non-ideal features, e.g., intra-tile gaps
Tore Supra example
φ(°)0 20
Toroidal angle
R(m)
2.25
2.5
Majorradius
φ(°)0 20
Toroidal angle
Sources of BBQ CD4 Rate Data [W. Langer, A. Erhardt, PPPL Technical Report]
# Reaction Product Comment1 e- + CD4 CD4
+ + 2 e- M2 CD3
+ + D + 2 e- M3 CD3 + D + e- M4 e- + CD4
+ CD3 + D+ + e- NM: = 1/4 R15 CD3
+ + D + e- NM: = 3/4 R16 CD3 + D Tot. R6+R7
M for E < 1 eV,Ex (E > 1 eV) = 1/4 Rexp
7 CD2 + 2 D As for R6,R7 = 3/4 Rexp
8 e- + CD3 CD3+ + 2 e- CD3 M
Ex (E<15 eV)
9 CD2+ + D + 2 e- From CD3 (M)
10 CD2 + D + e- NM, = 3/4 R3
11 e- + CD3+ CD2 + D+ + e- NM, = 1/3 R10
M = Measured, NM = Not Measured, Ex = Extrapolated, A = Assumed
Sources of the BBQ CD4 Rate Data [W. Langer, A. Erhardt]
12 CD2+ + D + e- NM, = 2/3 R10
13 CD2 + D Total M for E < 1 eV, Ex (E>1 eV)neglect other channels
14 e- + CD2 CD2+ + 2 e- From CD2 M(E<200eV)
and CD4 for E> 200eV)15 CD+ + D + 2 e- M (CD2)16 CD + D + e- NM, = 1/2 R317 e- + CD2
+ CD + D+ + e NM, = 1/2 R1618 CD+ + D + e- NM = 1/2 R1619 CD + D Total M (E < 1 eV)
Ex (E>1eV) neglect other channels20 e- + CD CD+ + 2 e- NM, adopted CD4 data21 C+ + D + 2 e- NM total R21+R22
A=1/2 R9; R21=1/2 total22 C + D+ + 2 e- NM, total R21+R22
A= 1/2 R9; R22=1/2 total23 C + D + e- NM = 1/4 R324 e- + CD+ C + D+ + e- NM = 1/2 R2325 C+ + D + e- NM = 1/2 R23M = Measured, NM = Not Measured, Ex = Extrapolated, A = Assumed
PISCES - A (UCLA) experiments: A. Pospieszczyk, FZ-Juelich
Reflex arc linear mirror plasma
Spectroscopic arrangementOptical multi channel analyzer
Code - experiment comparisonBBQ - Monte Carlo multi-species simulation ( Erhardt-Langer database)OMA ( A. Pospieszczyk, FZ-Juelich)
Nozzlelocation
Downstream distance(cm)
0 2 4 6
Rel. density
1.0
0.5
0
PISCES-A 13417
BBQ
CH2 axial density CH axial density
Rel. density
1.0
0.5
0
Nozzlelocation
Downstream distance(cm)
0 2 4 6
PISCES-A 13417
BBQ
Optical Multi-channel Analyzer(A. Pospieszczyk FZ-Juelich)
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.
- 3-D, time-dependent finite-elements thermal analysis code
- developed by CEA-DEMT
Modifications (CSPUTTER) include:
- 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
C6+(ρ) vs time, solpsoutboard mid-plane
Separatrix
Normalized Radius = 0.81 0.90 0.94 0.96 0.99 Shot = 119434
~ separatrix
�0.01 �0.005 0 0.005 0.01Time Relative to ELM (s)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
Impurity DensityC6
+ de
nsity
C6+ density CER
C6+ density solps
HFS separatrix
core
LFS separatrix
C6+
dens
ity
�0.005 0 0.005Time Relative to ELM (s)
CIII 4650.1 evolutionsolps 'standard' model
Roth et al 'annealing' model
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.