SEWG Meeting HIGH-Z, Ljubljana, October 2009

I. Tungsten distribution on limiters after WF6 injection in TEXTOR

II. SEM and EDX of Melted Tungsten Rods

SEWG Meeting HIGH-Z, Ljubljana, October 2009

I. 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, G. Sergienko, 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

• Further studies

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:

Injection plate0.02 x 1020 1 %

Local deposition:

Back plate (integrated)0.134 x 1020 7 %

ALT-II (integrated) 0.16 x 1020 8 %

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

Microscopy and EDX of ALT-II

Can we detect 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.

~15 % 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 ???

SEWG Meeting HIGH-Z, Ljubljana, October 2009

II. SEM and EDX of Melted Tungsten Rods

M. Rubel1, E. Fortuna2, D. Ivanova1, V. Philipps3, G. Sergienko3, E. Wessel3

1Alfvén Laboratory, Association EURATOM – VR, Stockholm, Sweden

2Faculty of Materials Science and Engineering, Warsaw University of Technology, Association EURATOM – IPPLM, Warsaw, Poland

3Institute of Energy Research (Plasma Physics), Association EURATOM – FZJ, Jülich, Germany

Background • Tungsten rods were used for a Langmuir probe at TEXTOR for ICWC

• The probe was not removed and after ICWC and then exposed to regular pulses.

Surface topography

Rod with melted tip

A droplet of molten W

was deposited on the adjacent rod

Rod with a droplet

Surface topography and composition

O

Al

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 385 cts Cursor: 0.103 (0 cts)

1

WC W

W

W

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 424 cts Cursor: 0.103 (8 cts)

3

Re-solidified tungstenInclusions of alumina from the rod isolation

C – 3.8 wt.%, 6.1 at.%

O – 51.9 wt.%, 62.4

at.%

Al – 44.3 wt.%, 31.5

at.%

Summary

Pronouced effects of melting are observed on the rods.

No signs of blister formation in areas distant to the plasma (2-5 cm).

The lack of blisters / bubbles on the rods agrees with all other

observations of solid tungsten (plates and test limiters) exposed in

TEXTOR (activity started in 1993).

One may consider an experiment with exposure of tungsten rods in the

SOL using a transfer system of the collector probe.

Surface topography