Analysis of samples exposed to Pilot–PSI

PlasmaP. Paris, A. Hakola, K. Bystrov, G. De Temmerman, M. Aints, I. Jõgi, M. Kiisk, J. Kozlova, M. Laan, J. Likonen, and A. Lissovski

Euratom-TEKES Annual Fusion Seminar; Tartu; 29-30 May 2012

Outline1. Problems of single-shot LIBS2. H&D detection3. Linear plasma machine Pilot-PSI and testing methods4. Results5. Conclusions

Laser induced beakdown spectroscopy (LIBS) – a tool for in situ monitoring of plasma-first wall interaction

The elemental depth profiles are found measuring LIBS spectra as a function of laser shot number.

Two main drawbacks of single-shot LIBS1. General: usually applied ensemble-averaged LIBS methods are not

applicable 2. Specific: because of a long recovering distance and low

concentration of some important species the role of noise is big

Development of ITER relevant techniques for deposited layer removal and tritium inventory diagnostics EFDA-CSU; Forschungszentrum Jülich, EURATOM-FZJ; VTT, Euratom-Tekes; DIARC-Inc.; University of Tartu, Euratom-Tekes; ENEA, EURATOM-ENEA; DIFFER, EURATOM-FOM; Alfvén Laboratory, EURATOM-VR; Institute of Plasma Physics and Laser microfusion, EURATOM-IPPLM

Samples Diarc Inc: 3 mm D-doped DLC coatings on W substrate

Pilot-PSI (DIFFER):

Ion energy and intensity of plasma fluxes are the same as in ITER

Pilot-PSI, experimental conditionsThe plasma fluence on targets was (2-3.5)1020 m-2s-1. Electron temperature Te = (0.5–1.1) eV; field B = 0.4 T, temperature Tsurf < 7000C DLC coating was exposed to hydrogen plasma during 80-120 s while in case of W/Al coating hydrogen – neon plasma was used and the exposure time was 500-550 s.

DIARC Inc.:Samples with ITER-relevant materialsW, DLC (carbon), Al (proxy of Be)

3 mm4 mm

Post mortem analysisSingle-shot LIBS (NdYAG laser: l=1064 nm) spectra as a function of the laser shot number were recorded from about 10 different spots corresponding to differently modified areas . Elemental depth profiles were also obtained by SIMS. Changes at the surface were also studied using SEM, X-ray microanalysis and X-ray diffraction techniques.

Photo of DLC sample after 100 s exposer

Deposition area:C 91%W 8%

1 mm

Unexposed area:C 99.5 %

5 mm

SEM

Exposed area:C 18 %W 82%

G

r

N = G(1-r)

XRD analysis Laser cratersDLC

DLC, SIMS

W/Al

12

3

1 2 3W 85% 81% 88% 88%

Mo 8%Al 0.6% W 75% 79% 89% 88%Mo 9%

W 60% 78% 88% 88%Mo 10%

Al 1% 1%

40 mm

CRACKING

SEM

Conclusion

Applying earlier elaborated data processing procedures, a good qualitative matching between LIBS and SIMS profiles was achieved.

The study showed that LIBS diagnostics gives reliable information about the plasma induced erosion/deposition processes and it could be used for in situ monitoring of fusion reactor walls.

Near-term steps

1. Modification of the optical set-up for reliable spectral resolving of hydrogen and deuterium lines

2. Obtaining experience with Be-containing samples (VTT, Romania)

3. Start of in situ measurements at DIFFER

Thank you for your attention!