Balkova 18.10.2017

1. Ion Induced Millimeter-Size Structures Growth
on Tungsten Surface

2.  Understanding of plasma-material
interactions (PMI)
 Preliminary modeling
 Accumulation of experimental data
 Erosion of the PFCs, fuel inventories
and material migration
Motivation
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3. Motivation
 High fluxes of particles (1021-1024 m-2s-1 and
above) and heat (up to 20 MW·m-2)
 The experimental data and ability of its
acquisition are limited for the high-flux range
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4. Experimental facilities: tokamaks
Typical topics:
• material migration
• influence of eroded material on plasma parameters
• re-deposition
• stability of PFCs under long-term irradiation
ASDEX
Upgrade
JET
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5. Experimental facility
The discharge gapCROSS-SECTION
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6. 6
Ballistic and magnetic ion beam focusing in action

7. 7
O. Girka, I. Bizyukov, K. Sereda, A. Bizyukov, M.
Gutkin, V. Sleptsov.
Compact steady-state and high-flux FALCON
ion source for tests of plasma-facing materials
// Review of Scientific Instruments, 83, 083501
(2012)
Ballistic and magnetic ion beam focusing

8. Ion energy distribution function
 The energy distribution of H ions
has been measured with accuracy
of 30 eV
 Cut-off of the low-energy part is
explained by strong magnetic field,
which bends the slow ions toward
the cathodes
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9. 9
FALCON ion source application for plasma-surface interaction modeling

10. Samples description
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 polished Plansee tungsten
samples
 purity 99.99% wt.
 sample size 15×12×0.75 mm3
 grain size 5-20 μm
 texture [100]
 residual stresses -220 MPa
 lattice parameter 3,1645 Å

11. Experimental conditions
The presence of impurities will influence the PWI processes by
both physical and chemical interactions. Tungsten, beryllium,
helium and divertor cooling species (argon, neon, or nitrogen)
will be present as impurities in the ITER plasma.1
1Ch. Linsmeier, B. Unterberg, J.W. Coenen, R.P. Doerner, H. Greuner, A. Kreter, J. Linke and H. Maier. Material testing facilities and
programs for plasma-facing component testing. Nucl. Fusion 57 (2017) 092012 (34pp). https://doi.org/10.1088/1741-4326/aa4feb
Irradiation parameters:
• Ar ion flux 2-3×1022 m-2s-1;
• heat flux 3 MW m-2 ;
• average ion energy 2 keV;
• sample temperature 1200 K.
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12. SEM images of W surface after 500 C Argon ions irradiation
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500 C

13. SEM images of W surface after 1000 C Argon ions irradiation
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1000 C

14. SEM images of W surface after 1000 C Argon ions irradiation
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1000 C

15. SEM images of W surface after 1000 C Argon ions irradiation
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1000 C

16. Conclusions
 Polished Plansee tungsten sample was irradiated with Ar ion flux
 Surface structures of millimeter-scale have been found on tungsten
surface
 Structures begin to growth after preliminary half-fluence (≈500
Coulomb) exposure and reach typical size of hundreds of micrometers in
longitudinal direction and height 0.1-0.2 mm (after exposure to
≈1000 Coulomb)
 This effect needs further investigations
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