Tungsten distribution on limiters after WF6 injection in TEXTOR

M. Rubel, D. IvanovaAlfvén Laboratory, Royal Institute of Technology, Association EURATOM – VR,

Stockholm, Sweden

V. Philipps, F. Nachtrod, C. Schulz, E. WesselInstitute of Energy Research (Plasma Physics), Forschungszentrum Jülich,

Association EURATOM – FZJ, Jülich, Germany

O U T L I N E • Tile Analysis

• Estimation of tungsten balance

• Summary and Plans

WF6 injection experiment: Motivation

Local and global W transport

Possibility of W layer deposition during plasma operation

Impact of fluorine on plasma contamination and operation

Fluorine long-term retention in plasma-facing components

Toroidal Limiter

Location of the test limiter

WF6 injection conditions

Toroidal direction

Injection channel

Polished graphite plate

Injection during 7 NBI heated shots through hole in roof-shaped test limiter

Shots without injection in between shots with WF6 injection

Limiter tip 1.5 cm in SOL

3 x 1019 WF6 mol/shot = 2 x 1020 total

15 shots in total, 100 s plasma

Hydrogen flux at injection (D+, r = 47.5) ≈ 4.x 18 /cm²s

Experiment close to shut-down; 250 s of plasma after the experiment.

Analysis

Methods

SEM,

EDX, EPMA

SIMS

NRA

RBS

poloidal7 cm

toro

idal

11 c

m

Local transport

19

Tile number 19 from 3 ALT-II blades:• Blade 5 near the injection point• Blade 1 located ~180o

• Blade 7 located ~90o

Long range transport

Analysis of tiles (RBS)

0,00

0,50

1,00

1,50

2,00

2,50

0 5 10 15

Poloidal direction [cm]

W c

on

ten

t [

E1

5/c

m2

] ALT-II 1/19

ALT-II 5/19

Toroidal limiter tile

Dep

ositi

on z

one

Ero

sion

zon

e

W distribution along the tiles

Messages:

Similar deposition profiles on tiles from different locations.

Somewhat greater content on the tile in the vicinity of the injection point.

Analysis of tiles

ALT-II 5/19 ALT-II 1/19

Deposition zone

Erosion zone

Deposition zone

Erosion zone

Approximate area per plate [cm2]

30 120 30 120

Average areal content [at/cm2]

1.23·1015 0.34·1015 1.17·1015 0.21·1015

Total content per plate [at]3.68·1016 4.10·1016 3.52·1016 2.53·1016

7.78·1016 6.05·1016

Total content for all the plates* [at] 1.55·1019

W balance

Injected 2 x 1020 100 %

Local deposition 0.02 x 1020 1 %

ALT-II 0.16 x 1020 8 %

Fluorine on ALT-II not found (below the detection limit).

Fuel content in flakes from ALT-II:Thermal desorption spectrometry

Concentration ratioD/C ~ 0.08

Microscopy and EDX of ALT-II

Can we detected tungsten deposition?If “yes”, what is the distribution, especially in the erosion zone?

20 m

Accumulation of heavy impurities in pits in the erosion zone.M. Rubel et al. Fusion Eng. Des. 81

NiC

NiCr Fe

Fe

Ni Mo MoClMoNi

Mo Cl Ni

Fe

Cl

Ni

MoCr FeSi

CrOCr

C

1 2 3 4 5 6 7 8 9

keVFull Scale 681 cts Cursor: 0.093 (9 cts)

1

C, Cr, Ni, Fe, Mo, Sibut no W detected

Surface after WF6 puffing experiment

Erosion zone

Microscopy and EDX of ALT-II

Al

B

O

C

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5

keVFull Scale 555 cts Cursor: 0.091 (13 cts)

1

Deposition zone

Summary

Only ~1% of injected tungsten detected around the injection point on the test limiter retracted from TEXTOR after the experiment.

~8% of injected tungsten found on the ALT-II limiter plates:

• tungsten detected mainly in the deposition zone;

• fairly uniform toroidal distribution

No fluorine detected on the ALT-II (concentration below 1016 cm2)

Plan for Future Studies

Further tracing of F in deposits on ALT with nuclear techniques (very difficult).

Chemical analysis of flakes from the deposition zone.

Chemical form of Tungsten around the injection point: XRD method.