1. Qualifying carbon as PFC Erosion (see report S. Brezinsek ) along plasma wetted areas, effect of substrate Local C migration to gaps Fuel retention.

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)