Transcript Document

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
o
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:
•
•
2)
oxidation (maybe aided by RF)
ablation with pulsed energy (laser or flashlamp).
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
o
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
o
Codes in use for erosion/deposition/retention
(D Coster, J Hogan PSIF Workshop Summary Nucl Fus 2005)
a. 2/3D Kinet ic codes
Code
WBC
ERO
BBQ DIVIMP DORIS
Geomet ry
3D
2/3D 3D
MCI EDDY
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
SOLP S
EDGE2D
UEDGE
2D
2D
Geomet ry
2D
Model
SC
SC
SC
Dynamics
FL
FL
FL
TR - trace impurity
in fixed background
SC - self-consistent background
and impurity solution
o
GO - gyro orbit following
(classical diffusion)
GC - guiding center fluid
(anomalous transport)
FL - fluid + kinetic corrections
CODES
BBQ
Scrape-off layer Monte Carlo impurity
transport (3-D, velocity space)
Collision model
Background parameters assumed (n e, l n , T e, l T )
+
[ local D flux amplification, sheath
]
electrostatic (es) field, E
SOL
M Z dV Z /dt = -F friction -F es
+ random // and ^ diffusion
F
= -M (V
-V ) / t ; F
friction
Z SOL Z
s
es = Ze E SOL
F // = Random // diffusion, D // =(8E Z /3pM i) t//
F = Random ^ anomalous diffusion ( D )
^
^
dE Z /dt = (kT -E Z )/t +W
+W
i
T
friction
es
Birth gyro-collisions with surface
B2-Eirene
Axisymmetric divertor simulation
Time / space (2D) -dependent
Divertor plasma fluid (B2), neutrals (Eirene)
Developed by
B. Braams (Emory Univ.)
R. Schneider, D. Coster
(MP - IPP, Garching, Greifswald)
D. Reiter (FZ-Juelich)
o
CASTEM / TOKAFLU
(R Mitteau et al J Nucl Mater 1999)
Plasma-facing component
thermal analysis (3-D FEM, time)
IMPFLU
Physics package:
- self-consistent heat flux (from n e, T e, )
(includes SEE, thermionic)
- local impurity redeposition heat source
- test sputtering models
- effects of deposited films
Hydrocarbon molecular processes
Erhardt-Langer CH 4 database
Alman-Ruzic
Janev-Reiter
Relation between chemical erosion processes and H/D/T retention
JET deuterium - hydrogen change-over experiment
D Hillis, J Hogan et al J Nucl Mater 2001
H wall loading
first 5 shots
Of D-->H changeover
CD / CH Molecular Band is analyzed to
determine the H/D concentration in the divertor
(G. Duxbury - Univ Strathclyde)
1.0
Divertor Spectroscopy
Sub-Divertor-Penning
CH-CD Spectroscopy
0.8
Hydrogen Concentration
48282
H concentration as deduced from
the CH-CD Molecular Band
0.6
48280
Hydrogen Concentration
0.5
48283
48281
0.6
48280
0.4
0.2
0.4
0.0
40
0.3
0.2
0
50
60
80
100
120
140
Accumulated Time (s)
Divertor Spectroscopy
Sub-Divertor - Penning
CH-CD Spectroscopy
0.1
o
48292
48284
52
54
Time (s)
56
58
60
275
160
180
Tore Supra
Interior view of Tore Supra
machine axis
Qpoloidal direction


f toroidal direction
Full toroidal limiter CIEL
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Coupled core/ SOL/PFC code system
CASTEM-TOKAFLU-IMPFLU
BBQ
ITC-SANCO-MIST
Deuterium sputtering stage
D+
Te()
ne()
e
BBQ
Cin ( Zi)
=> Core C influx
Sum over processes and geometries
physical
chemical
RES
MIST/ITC
Superstructure
leading edge
neutralizer
=>  C out (Z i) Core C efflux: D + - sputtered
Self- sputtering iteration
BBQ
MIST/ITC
o
=>  C out (Z i) Core C efflux: self - sputtered C
o
< NC >
BBQ carbon density
averaged over f
LCFS
< NC >
10 18 m-3
1.2
Mid SOL heating
III
IV
0.6
V
VI
VII
0
0.9
o
0.95
1.0
radius (/a)
1.03
1.06
NC (1016 m-3)
< NC > (1016 m-3)
8.8
2.3
4.4
System evolution for
localized heating in
inner, mid- and far-SOL
1.15
0
0
0.5
( r/a)
1.0
for:
0
- TRIM self-sputter
(TOP)
1.5
NC (1018 m-3)
1.05
- enhanced self-sputter
(BOTTOM)
.
0.75
0.525
0
0
1
0
o
0.5
( r/a)
1.0
9
iteration
Tore Supra heat, particle flux deposition is strongly
influenced by magnetic field ripple (~7%)
R Mitteau et al J Nucl Mater 2001.
o
o
Model validation requires attention to impurity generation
from non-ideal features, e.g., intra-tile gaps
Tore Supra example
Major
radius
2.5
R(m)
2.25
0
f
20
Toroidal angle
Modelled C emission
(TOKAFLU / BBQ)
34909
Physical sputtering source
o
T e,b =35 eV, n e,b =0.67 10 19 m-3
Pinj -Prad=0.7 MW
0
f
Toroidal angle
Measured
CII radiation
34930
(E Dufour, C Lowry
et al, EPS 2005)
20
Sources of BBQ CD4 Rate Data [W. Langer, A. Erhardt, PPPL Technical Report]
#
1
2
3
4
5
6
Reaction
e- + CD4
e- + CD4+
7
Product
CD4+ + 2 eCD3+ + D + 2 eCD3 + D + eCD3 + D+ + eCD3+ + D + eCD3 + D
CD2 + 2 D
e- + CD3
8
9
10
e- + CD3+
11
CD3+ + 2 e-
Comment
M
M
M
NM: = 1/4 R1
NM: = 3/4 R1
Tot. R6+R7
M for E < 1 eV,
Ex (E > 1 eV)
= 1/4 Rexp
As for R6,
R7 = 3/4 Rexp
CD3 M
Ex (E<15 eV)
CD2+ + D + 2 eCD2 + D + e-
From CD3 (M)
NM, = 3/4 R3
CD2 + D+ + e-
NM, = 1/3 R10
M = Measured, NM = Not Measured, Ex = Extrapolated, A = Assumed
o
Sources of the BBQ CD4 Rate Data [W. Langer, A. Erhardt]
12
13
CD2+ + D + eCD2 + D
NM, = 2/3 R10
Total M for E < 1 eV,
Ex (E>1 eV)
neglect other channels
14
e- + CD2
CD2+ + 2 eFrom CD2 M(E<200eV)
and CD4 for E> 200eV)
15
CD+ + D + 2 eM (CD2)
16
CD + D + eNM, = 1/2 R3
+
+
17
e + CD2
CD + D + e
NM, = 1/2 R16
+
18
CD + D + e
NM = 1/2 R16
19
CD + D
Total M (E < 1 eV)
Ex (E>1eV) neglect other channels
20
e- + CD
CD+ + 2 e- NM, adopted CD4 data
21
C + + D + 2 eNM total R21+R22
A=1/2 R9; R21=1/2 total
22
C + D+ + 2 eNM, total R21+R22
A= 1/2 R9; R22=1/2 total
23
C + D + eNM = 1/4 R3
+
+
24
e + CD
C +D +e
NM = 1/2 R23
+
25
C + D + eNM = 1/2 R23
M = Measured, NM = Not Measured, Ex = Extrapolated, A = Assumed
o
PISCES - A (UCLA) experiments:
A. Pospieszczyk, FZ-Juelich
Spectroscopic arrangement
Optical multi channel analyzer
Reflex arc linear mirror plasma
o
Code - experiment comparison
BBQ - Monte Carlo multi-species simulation ( Erhardt-Langer database)
OMA ( A. Pospieszczyk, FZ-Juelich)
CH axial density
CH2 axial density
1.0
1.0
PISCES-A 13417
PISCES-A 13417
BBQ
Rel. density
Rel. density
0.5
0.5
BBQ
0
0
0
Nozzle
location
o
Optical Multi-channel Analyzer
(A. Pospieszczyk FZ-Juelich)
0
2
4
6
Downstream distance
(cm)
Nozzle
location
2
4
6
Downstream distance
(cm)
Schematic diagram of experiment on
Tore Supra Midplane Limiter (Phase II)
o
E Gauthier, A Cambe J Hogan et al
J Nucl Mater 2003
o
Model comparison using partial pressure
- sensitivity to sputtering model
LHCD: High Tsurf
CD4 partial pressure
CD emission
510
670
Tsurf(K)
Increased production
of CD4 with flux
P CD4D0.73
PCD4 PD2 0.70
o
JT-60U (N. Hosogane)
830
Deuteron impact charge exchange data [Alman, Ruzic]
D+ + CnDm -->
D + CnD4+
Reaction
Product
Rate
Known
-9
3
(10 cm /s)
(total)
CD4
D+ + CD4
D + CD4+
1.880
4.150
D2 + CD3+
1.880
D+ + CD3
D + CD3+
1.800
+
D2 + CD2
1.800
+
+
D + CD2
D + CD2
1.700
D2 + CD+
1.700
D+ + CD
D + CD+
3.236
C2D2
D+ + C2D2
D + C2D2+
2.250
6.300
+
D2 + C2D
2.250
D+ + C2D
D + C2D+
4.358
o
Heavy hydrocarbon production: dominant species from
break-up of C2D2.
BBQ calculation using Alman-Ruzic database
C2 D2
o
C2 D2 +
C2 D+
C2 +
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
Janev-Reiter profiles
CH+
CH+
CH+
ne,LP= 2 1018 m-3
CH4
o
Te,LP= 20 eV
CH4
CH4
Te,LP= 10 eV
Te,LP= 5 eV
o
ne,LP = 2 10 18 m-3
CH+ density
E- L
J-R
Te LP = 20 eV
0.04
0.08
0.12
0.16
0.20
0.24
Axial distance (m)
CH+ density
E- L
Te LP = 10 eV
J-R
0.04
0.08
CH+ density
0.12
0.16
Axial distance (m)
0.20
0.24
E- L
J-R
o
0.04
0.08
Te LP = 5 eV
0.12
0.16
0.20
Axial distance (m)
0.24
Janev-Reiter profiles
CH+
CH+
CH+
ne,LP= 6 1018 m-3
CH4
o
Te,LP= 20 eV
CH4
CH4
Te,LP= 10 eV
Te,LP= 5 eV
CH+ density
ne,LP = 6 10 18 m-3
E- L
J-R
Te LP = 20 eV
0.04
0.08
0.12
0.16
Axial distance (m)
0.20
0.24
CH+ density
E- L
J-R
0.04
0.08
CH+ density
0.12
0.16
Te LP = 10 eV
0.20
0.24
Axial distance (m)
E- L
J-R
Te LP = 5 eV
0.04
o
0.08
0.12
0.16
Axial distance (m)
0.20
0.24
01
00 02
DIII-D intrinsic
impurities
before/after new tile
installation
Some evidence of
T-dependent
8
processes
11
03
04
12
Filterscope
(schematic)
13
Carbon concentration (%)
Edge
RDP-1999
RDP-2000
0
3 Core
0
0.4
o
0.6
0.8
1.0
Time (s)
1.2
1.4
CASTEM-2000 simulation of time-dependent carbon generation
from simulated DIII-D localized source
Maximum T surf
on heated surf ace
1200
C flux
(1018 parts/cm2/s)
1.6
1400
1.2
800
600
1 mm
Tsurf (K)
1000
400
2.5 mm
0.8
Chemical
0.4
200
NBI
0
0
1
2
3
Time (s)
NBI
0
4
5
0
1
2
3
Time (s)
4
5
NBI
2.0
C flux
(1018 parts/cm2/s)
RES
1.6
1.0
Y
@ t ~ 4s
chem
when T
= 1010K
max
0.6
NBI
0
0
o
min
Y
= 1. 10 -2
chem
1
2
3
Time (s)
4
5
max
Y
= 0.14
chem
o
Semi-empirical model for
ELM transport enhancement
Green: ELM-affected region
in the model
2
Red: C neutrals and ions
Yellow: D neutrals ion ions
ELM event
3
1
Transport time dependence
(schematic)
1. Pre-ELM (barrier)
2. Strong enhancement (100 sec) ELM
3. Loss of barrier, 2 x pre-ELM value
4. reducing to pre-ELM value as barrier
is re-established
4
time
3
Intra-ELM transport radial dependence
(schematic)
1. barrier
2. enhancement toward SOL
3. SOL radial transport
2
edge / pedestal only,
low-field side only
1
separatrix
radius
o
C6+ density solps
core
C6+ density
C6+() vs time, solps
outboard mid-plane
Separatrix
HFS s e paratrix
LFS s e par atr ix
0.005
0
Time Relative to ELM (s)
C6+ density CER
Nor maliz ed Radius = 0.81
0.90 0.94 0.96 0.99
Shot = 119434
0.12
Im purity Density
C6+ density
0.10
0.08
0.06
0.04
0.02
~ separatrix
0.00
0
Time Relativ e to ELM (s)
o
0.005
0.01
DIII-D experimental:
fast (CID) camera
Modeling
solps 5.0 / Eirene99
IPP-Garching/Greifswald,
FZ-Juelich
CIII 4650.1 evolution
solps 'standard' model
Roth et al
'annealing' model
Inner leg
pre-ELM detached
during attached
re-detaching
after
recovery of
detachment
CIII evolution:
M Groth et al,
J Nucl Mater 2003
o
Solps simulation of
CIII emission
seen by 240par
(lower divertor)
camera
W Meyer,
M Fenstermacher,
M Groth
LLNL
o
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
ELM heat flux mitigation by
Injection of extrinsic impurities
o
Chemical sputtering of carbon materials due to combined bombardment
by ions and atomic hydrogen W Jacob, C. Hopf, M. Schlüter, T. Schwarz-Selinger
Max-Planck-Institut für Plasmaphysik Garching
chemical sputtering yield (per ion)
10
N+2
1
He+
H+2 = 2 H+
0.1
o
Ar+
Ne+
10
Flux ratio H/ion = 400
100
energy (eV)
1000
CONCLUSIONS
Intrinsic (carbon) impurity sources play a key role in ITER, both as regards erosion and for
tritium retention
The ITER problem (addressed also by JET) requires a decision about the first wall
material - carbon or an alternative
Development of validated models for C generation, deposition and retention requires
experimental comparison: this typically introduces multiple uncertainties; e.g., sputtering
yield models vs hydrocarbon break-up rates
ITER relevant experimental scenarios involve fast timescale ELM events, for which
spectroscopy is an key tool
The importance of hydrocarbon generation processes has been seen in many
experiments, and thus a quantitative, evaluated, integrated model for break-up processes
in the plasma is needed.
o