1. Analysis of samples exposed to Pilot–PSI Plasma
P. Paris, A. Hakola, K. Bystrov, G. De Temmerman, M. Aints, I. Jõgi, M. Kiisk, J. Kozlova,
M. Laan, J. Likonen, and A. Lissovski
Outline
Problems of single-shot LIBS
H&D detection
Linear plasma machine Pilot-PSI and testing methods
Results
Conclusions
I’ll speak about the study of erosion of the plasma-exposed ITER-relevantmaterials. The main goal of our studies is the developing of of the laser induced plasma spectroscopy as a diagnostic method.
Euratom-TEKES Annual Fusion Seminar; Tartu; May 2012

2. 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 LIBS
General: usually applied ensemble-averaged LIBS methods are not applicable
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

3. Samples Diarc Inc: 3 mm D-doped DLC coatings on W substrate
Siin ei ole korrektne vt faili results of testing

4. Pilot-PSI (DIFFER): DIARC Inc.:
Ion energy and intensity of plasma fluxes are the same as in ITER
DIARC Inc.:
Samples with ITER-relevant materials
W, DLC (carbon), Al (proxy of Be)
3 mm
4 mm
Pilot-PSI, experimental conditions
The 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 s while in case of
W/Al coating hydrogen – neon plasma was used and the exposure time was s.
Post mortem analysis
Single-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.

5. SEM Unexposed area: Deposition area: Exposed area: C 99.5 % C 91% W 8%G r
N = G(1-r)
Unexposed area:
C 99.5 %
5 mm
SEM
Photo of DLC sample after 100 s exposer
Exposed area:
C 18 %
W 82%
Deposition area:
C 91%
W 8%
1 mm

6. XRD analysis
Laser craters
DLC

7. DLC, SIMS

8. W/Al SEM 1 2 3 CRACKING 40 mm W 85% 81% 88% 88% Mo 8% Al 0.6% W 75%
1 2 3
W 85%
81% 88% 88%
Mo 8%
Al %
W 75%
79% 89% 88%
Mo 9%
W 60%
78% 88% 88%
Mo 10%
Al 1% %
40 mm
CRACKING
SEM

9. Thank you for your attention!
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
Modification of the optical set-up for reliable spectral resolving of hydrogen and deuterium lines
Obtaining experience with Be-containing samples (VTT, Romania)
3. Start of in situ measurements at DIFFER
Thank you for your attention!