Upload
michelle-oneil
View
216
Download
0
Tags:
Embed Size (px)
Citation preview
1. Qualifying carbon as PFC
• Erosion (see report S. Brezinsek )
along plasma wetted areas, effect of substrate
• Local C migration
to gaps
• Fuel retention
O GDC
• Cleaning of redeposited C layers
ICRH O-He conditioning plasmas
Report of FZJ activities in EU PWI TF
V.Philipps, S. Brezinsek (for P. Mertens)
EU-PWI-Task Force
Trila
teral Euregio Cluster
TEC
EU-PWI-Task Force
Trila
teral Euregio Cluster
TEC
2. Qualifying high Z plasma facing components (see SEWG presentation by R. Neu)
main aims: Behaviour under high loads up to and beyond melting
database for W spectroscopy (W-sources)
3. Development of in situ laser based thermal desorption spectroscopy to measure fuel retention
Aim: measure in situ fuel retention on PFC shot by shot
4. Modelling of erosion deposition and ITER predictions
1. Local C transport
Local 13C tracer injection through limiters in TEXTOR
Similar experiments in JET, participation on AUG
Textor summary:
low local re-deposition fraction (~ 0.3-4%) and deposition pattern requires assumption of enhanced transport (modelled by higher re-erosion (compared with substrate) of redeposited carbon fragments)
JET 13C injection outer divertor: high redeposition fraction, however uniform 13C distribution after outer divertor injection along strike point , despite localised injection points ( 52), needs similar assumptions
AUG: high redeposition fraction, toroidal pattern under modelling
EU-PWI-Task Force
Trila
teral Euregio Cluster
TEC
A. Kreter, ITPA Toronto
Roof like limiters often used
EU-PWI-Task Force
Trila
teral Euregio Cluster
TEC
C substrate
D CxHy
Physical sputtering
Roth formula
C
Ero marks the redeposited species with a higher probability for re-erosion, only on plasma wetted areas
Picture: Harry Reimer
torroidal direction
erosion - zone
deposition - zone
Carbon
Moly
bdenum
Tungsten
37 mm
19 mm
>1 mm
C
Mo
W
Erosion Deposition
Ero Tridyn ongoing to model material mixing and deposition
EU-PWI-Task Force
Trila
teral Euregio Cluster
TEC
Compare deposition and mixing on C, W, Mo
Test for new ERO Tridyn
Migration to gaps: (see also SEWG G. Counsell)
A series of dedicated experiments under erosion and deposition dominated conditions
Difference between toroidal and poloidal gaps
Effect of shaping
EU-PWI-Task Force
Trila
teral Euregio Cluster
TEC
Exposure of W castellated limiter in the SOL of TEXTOR:
A. Litnovsky for EU TF PWI Meeting, Ljubljana, Nov. 13-14, 2006
20o
Toroidal
directio
nPoloidal
direction
SOL Plasma
Shaped cells
10x10x12(15)mm
Rectangular cells
10x10x15 mm
The shape of a castellation cells can be optimized to reduce impurity and fuel transport into gaps
Motivation
● Experimental details
•● Shaped and rectangular cells
• exposed under the same plasma
• conditions (controlled
• with spectroscopy);
•● Series of repetitive discharges;
•● Each cell mounted separately;
•● Post-exposure analyses with
• SIMS, Dektak, NRA and EPMA
• (FZJ, IPP Garching and RWTH
• Aachen).
Gaps 0.5 mm
The influence of the shape of castellation on fuel accumulation and C deposition in gaps
Photograph after exposure
NB
31
DM
S780
EK
98Deuterium retained in the samples
0
1·1021
2·1021
3·1021
4·1021
TDS1 (limiter tip) 2·1025 D/m2
TDS2 (22mm
outside LCFS) 4·1024 D/m2
Deu
teri
um
ret
ain
ed [
D/m
2]
EK
98
DM
S78
0
NB
31
EK
98
DM
S78
0
NB
31
Thermal desorption measurements
Limiter temperature:
Tbulk: 470 K (1st pulse) – 520 K (last pulse)
Tsurface (close to limiter tip) increases by 100 K during pulse
D/(H+D) 80%
No significant difference of graphite types seen
32 reproducible discharges177 s total duration
spectrometers
Temperature in Laser Spot measured (max+Laser)Trilateral Eureg io Cluster
TEC
Inst itut f ür PlasmaphysikA ssoziat ion EU RA TO M -Fo rschungszentrum Jü l ich
0.0 0.5 1.0 1.5 2.00.0
0.5
1.0
1.5
2.0
2.5
500
1000
1500
2000
2500
3000
Temperature in Spot Centre
La
ser
Po
we
r PLaser /
kW
Time t / ms
Temperature in Laser Spot Centre (Nd:YAG)
reproduceable Laser Pulses
110 100
90
Te
mp
era
ture
T /
°C
120 calculated Temperature for
different Heat Loads [kW/cm2]
Aim: release all fuel without ablation of layer
Parallel to LIBS
Suppression of eddy currents: 8 stacks assembled insulated bulk tungsten lamellae attached to a fishbone–like wedge, which is tied to a cross-like adapter
Design of a W bulk tile for the JET ILW project
Larger engineering effort
6 mm
1.5 – 7 degree
Shaping of all lamellas will be done
Does not affect power handling due to heat diffusion across the lamella
(3D Ansys calculations
EU-PWI-Task Force
Trila
teral Euregio Cluster
TEC
Within the ILW , the individual lamellas will be shaped to proetect of hot spots
Not foreseen in ITER brush design
Issue card for ITER
In total about 8000 W lamellas
HHF cyclic tests: 7 MW/m2, 10 s ~ 140 pulses
No macroscopic damage, but Micro-cracks at the loaded surface
No impact of micro-cracks on the HHF performance
(up to the number of pulses investigated)