ITPA Avilla January 2008 © Matej Mayer

Surface modifications and blistering of tungsten

exposed in ASDEX Upgrade

M. Mayer, M. Balden, S. Lindig, J. Roth, R. Neu, ASDEX Upgrade team

Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching, Germany

ITPA Avilla January 2008 © Matej Mayer

Blister formation in W, laboratory studies

W. Wang et al., JNM 299 (2001) 124

Surface modifications observed after

bombardment of W by hydrogen

in laboratory studies

Blister formation

Polycrystalline tungsten samples

(Langmuir probes) exposed

in AUG outer divertor

in 2007 for 2620 s

ITPA Avilla January 2008 © Matej Mayer

Langmuir probes from outer divertor

Blister-like structures are observed

ITPA Avilla January 2008 © Matej Mayer

Langmuir probes from outer divertor

Do these structures contain voids?

FIB using 30 keV Ga

ITPA Avilla January 2008 © Matej Mayer

Langmuir probes from outer divertor

Protective carbon coating

for FIB

ITPA Avilla January 2008 © Matej Mayer

Langmuir probes from outer divertor

Blister-like structures filled

with material, no voids

These are no blisters

ITPA Avilla January 2008 © Matej Mayer

Langmuir probes from outer divertor

But:

ITPA Avilla January 2008 © Matej Mayer

Langmuir probes from outer divertor

A few blisters are observed

in this area of the sample

ITPA Avilla January 2008 © Matej Mayer

Summary

• Blister-like structures are observed, but they are solid and do not contain voids No blisters

• A few blisters are observed in some areas of the sample

• Surface modifications of W due to plasma exposure are small