Embed Size (px)
DESCRIPTION
A Further Study of JET Impurity Sources Jim Strachan PPPL, Princeton University USA May 2005. Core contamination arises from SOL contamination fuelled by: neutral ionization from the wall (included in EDGE2D), ion escape from the divertor (included in EDGE2D), - PowerPoint PPT Presentation
Citation preview
1
A Further Study of JET Impurity SourcesJim Strachan
PPPL, Princeton UniversityUSA
May 2005
• Core contamination arises from SOL contamination fuelled by: – neutral ionization from the wall (included in EDGE2D), – ion escape from the divertor (included in EDGE2D),– Ion bombardment of walls (simplistically included in EDGE2D),– Three dimensional objects (not included in EDGE2D).
• At PSI, Mike Stamp and I speculated that C3V/C3H provides info about ion escape from the outer divertor
• Answer: - Yes, but carbon ion out-flux is small.• However, learned incrementally more about JET impurity
sources.
2
Method
• Philosophy: use an ensemble of EDGE2D runs to encompass the experimental parameter scans and uncertainties.
• Created an ensemble of EDGE2D runs with variations in ΓD, ΓC, χe=χi, D, DC, YC, EC, PSOL
• Study C3H, C3V, C3I, C3O, DαH, DαV, DαI, DαO from these simulations
• Compare to JET L-Mode and inter-ELM H-Mode plasmas from J. Strachan, et al, NF 43, 922 (2003).
• Some limitations: spatially constant transport coefficients, no pinch velocity, no ELMs.
3
Carbon density profiles from carbon injected at OSP indicate
Carbon leaves the divertor as ions, and low ionizations states
Occur in the lower vessel
4
Poloidal distribution of carbon ionization calculated by EDGE2D
RED = carbonUniformly injected Along wall
Blue = natural sputtering
Green = carbonInjected fromOuter strike point
5
EDGE2D carbon migration pattern
separatrix density (/m3)
0.0x100
5.0x10+18
1.0x10+19
1.5x10+19
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
std case- 2.5 MW
ionized in SOL
total source
lost to wall
total lost
carbon ionizationin SOL
carbon ion flow from outer divertor
carbon lostto wall
carbon flowto inner divertor
separatrix density (/m3)
0.0x100
5.0x10+18
1.0x10+19
1.5x10+19
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
natural sputtering
ionized in SOL
total source
lost to wall
total lost
separatrix density (/m3)
0.0x100
5.0x10+18
1.0x10+19
1.5x10+19
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
uniform wall source
ionized in SOL
total source
lost to wall
total lost
separatrix density (/m3)
0.0x100
5.0x10+18
1.0x10+19
1.5x10+19
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
Outer strike point
ionized in SOL
total source
lost to wall
total lost
½ of carbon goes to inner divertor and ½ to grid edge (wall) independent of source location
Fra
ctio
n o
f ca
rbo
n
6carbon ionization in SOL (/sec)
1018
1019
1020
1021
1022
3.25
107 C
3H
1018
1019
1020
1021
1022
EDGE2D
natural sputtering
uniform wall source
outer strike point source
low density nsep = 2.2 1018 /m3
high C energy = 10 eV
C3H provides a good approximation to the carbon ionization in the SOL
Unity
First result:
7
ion flux out of outer divertor - ion flux to wall (/sec)
-4x10+20
-2x10+20
0x100
2x10+20
4x10+20
-4x10+20
-2x10+20
0x100
2x10+20
4x10+20
difference in C ion flux = -2.36 10 20 ln(7.41 C3H/C3V)difference in C ion flux = -2.36 10 20 ln(7.41 C3H/C3V)
EDGE2D
natural sputtering
uniform wall source
outer strike point source
Unity
Ratio C3H/C3V provides info on C ion out flux from outer divertor
Second Result:
8
JET L-MODE plasmas have CIII signals like a uniform wall source
C3H (photons/str/cm2/s) (PPF units)
1010
1011
1012
1013
1014
C3V
(ph
oton
s/st
r/cm
2 /s)
(PP
F u
nits
)
1011
1012
1013
1014
1015
EDGE2D
natural sputtering
uniform wall source
outer strike point source
1010
1011
1012
1013
1014
1011
1012
1013
1014
1015
JET L-MODE
140 kV NBI
both NBI
80 kV NBI
1010
1011
1012
1013
1014
1011
1012
1013
1014
1015
JET H-Mode
Inter-ELM
unity
Compare to Experiment:
9
1020 1021 1022
Deu
teri
um I
oniz
atio
n ra
te (
/s)
1021
1022
1023
1024
Deuterium Ionization is reasonably represented by the D signal according to EDGE2DDeuterium Ionization is reasonably represented by the D signal according to EDGE2D
EDGE2D - natural sputtering
divertor
wall
FLW (/s) FLX (/s)
S = 24 D
To study SOL C ionization, must first establish D influx = outflux
10
The density rise in EDGE2D seems different than observedIn JET L-Mode. Note, separatrix density is assumed <ne>/3.Exp has more recycling at low density, and less density riseAt high injection, also little correlation with τE.
Note fuelling rate adjusted since EDGE2D only fuels the grid, and not the entire core
0x100
1x10+22
2x10+22
3x10+22
4x10+22
0x100
1x10+19
2x10+19
JET L-MODE
confinement = 0.35 sec, I = 1.85 MA
confinement = 0.5 sec, I = 2.37 MA
Deuteron injection rate (/sec)
0x100
1x10+22
2x10+22
3x10+22
4x10+22
sepa
ratr
ix d
ensi
ty (
/m3 )
0x100
1x10+19
2x10+19
EDGE2D, 2.5 MW
D = 0.5 m2/s
D = 0.25 m2/s
D = 1.5 m2/s
11
separatrix density (/m3)
1018
1019
1020
tota
l D
(p
hoto
ns/s
ec)
1020
1021
1022
1023hax.PDW
JET L-Mode
tauE = 0.35 sec, I = 1.85 MA
tauE = 0.35 sec
tauE = 0.5 sec, i = 2.35 sec
tauE = 0.5 sec
separatrix density (/m3)
1018 1019 1020
tota
l D
(
phot
ons/
sec)
1020
1021
1022
1023e2d-nat.sputt.PDW
P=2.5 MW
D = 0.5 m2/s
D = 0.5 m2/s
D= 0.25 m2/s
D = 1.5 m2/s
FLX
FLW
FLX
FLW
EDGE2D JET L-Mode
Both EDGE2D and JET L-Mode indicate a correlation of SOL And divertor deuterium influx with density, however, JET has higherAt higher density. Both EDGE2D and JET L-Mode have lessRecycling at higher confinement.
12
At low density, EDGE2D predicts the L-Mode recycling, butUnderestimates it at high density, while over-estimating H-Mode
1018
1019
1020
1020
1021
1022
1023
JET L-Mode
tauE = 0.35 sec, I = 1.85 MA
tauE = 0.35 sec
tauE = 0.5 sec, I = 2.35 MA
tauE = 0.5 sec
1018
1019
1020
1020
1021
1022
1023
EDGE2D
0.5 m2/s
0.5 m2/s
<0.5 m2/s
>.5 m2/s
separatrix density (/m3)
=<ne>/3 for L-Mode=<ne>/4 for H-Mode
1018
1019
1020
tota
l D
(
phot
ons/
sec)
1020
1021
1022
1023
JET H-Mode
FLX
FLW
FLX
FLW
13ratio of carbon to deuterium ionization in SOL
0.00 0.01 0.02 0.03 0.04 0.05 0.06
expe
rim
enta
lly
defi
ned
yiel
d
0.00
0.01
0.02
0.03
0.04
0.05
0.06
experimentally defined yield
= 3.25 107 C3H / 24 FLW
experimentally defined yield
= 3.25 107 C3H / 24 FLW
EDGE2D natural sputtering
D=.5, P=2.5
low D
low P
P=4
P=7
high D
Experimentally, the Yield is defined by the ratio of carbon to deuteriumLight. EDGE2D, indicates that this ratio correlates with theCarbon to deuterium ionization rates in the SOL
14
1 %
10%
Yield
deuterium ionization rate in SOL (/s)
1021 1022 1023
carb
on i
oniz
atio
n ra
te i
n S
OL
(/s
)
1019
1020
1021
EDGE2D
physical + Haasz Chemical sputtering
physical sputtering only
1021 1022 1023
1019
1020
1021
JET L-Mode
1021 1022 1023
1019
1020
1021
inter-ELM H-Mode
SOL ionization rates: D rate is similar for EDGE2D, JET L-Mode, and JET Inter-ELM H-Mode, with experiment extending to higher values.C rate is similar for EDGE2D and L-Mode but higher for H-Mode
15
0x100
5x10+18
1x10+19
2x10+19
2x10+19
0.00
0.02
0.04
0.06
0.08
0.10Wall Source
EDGE2D
physical + Haasz chemical sputtering
0.0x100
5.0x10+18
1.0x10+19
1.5x10+19
2.0x10+19
0.00
0.02
0.04
0.06
0.08
0.10
JET H-MODE
inter-ELM
separatrix density (/m3)
0.0x100
5.0x10+18
1.0x10+19
1.5x10+19
2.0x10+19
Yie
ld
0.00
0.02
0.04
0.06
0.08
0.10
JET
L-Mode
Both L-Mode and EDGE2D indicate that the yield decreases asDensity increases, although stronger in L-Mode. Inter-ELMH-Mode has higher Yield values.
16
Discussion• EDGE2D (chemical sputtering = ½ Haasz):
– C3H is an indicator of SOL C ionization– C3H/C3V can indicate C ion escape from outer divertor– Described the C Yield at low density on L-Mode– Recycling correlates with SOL deuterium diffusivity
• JET L-Mode:– Uniform C wall source– Enhanced recycling at high density– Recycling inversely correlates with confinement– C Yield about equals EDGE2D
• JET H-Mode:– C wall source stronger than L-Mode– Recycling lower than EDGE2D– C Yield 2X higher than EDGE2D, indicating another source
