1 EFFECTS OF CARBON REDEPOSITION ON TUNGSTEN UNDER HIGH-FLUX, LOW ENERGY Ar ION IRRADITAION AT ELEVATED TEMPERATURE Lithuanian Energy Institute, Lithuania Vytautas Magnus University, Lithuania Poitiers University, France Prof. habil. dr. L. Pranevičius 2006-11-15
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1 EFFECTS OF CARBON REDEPOSITION ON TUNGSTEN UNDER HIGH-FLUX, LOW ENERGY Ar ION IRRADITAION AT ELEVATED TEMPERATURE Lithuanian Energy Institute, Lithuania.
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EFFECTS OF CARBON REDEPOSITION ON TUNGSTEN UNDER HIGH-FLUX, LOW ENERGY Ar ION IRRADITAION
AT ELEVATED TEMPERATURE
Lithuanian Energy Institute, LithuaniaVytautas Magnus University, Lithuania
Poitiers University, France
Prof. habil. dr. L. Pranevičius
2006-11-15
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Outline of the presentationOutline of the presentation
1. Introduction,
2. Sources of carbon redeposition,
3. Simulation of dynamic mixing,
4. Experimental results,
5. Discussions,
6. Conclusions.
1
3
IntroductionIntroduction
Issue: MATERIAL TRANSPORT AND EROSION /DEPOSITION FOR FUSION PROGRAMME
The rate of erosion of the divertor targets and building up of deposited films may ultimately limit the choice of divertor materials and the
operational space for ITER
4
IntroductionIntroduction
1
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0600
800
1000
1200
1400
1600
1800
Time, s
Co
pp
er
Su
rfa
ce
Te
mp
era
ture
, K W
Be
Tm
Cu
on 5 mm Cu Substrate
5 mm W or Be Coating or
60 MJ/m2
300 ms
20 mm Carbon Tiles
VDE
C
Li
Cu Substrate
W/Be/C Coatings or Tiles
Interface
LIST OF PROCESSES
Sketch of divertor
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IntroductionIntroduction
The present work is an attempt to explain:– the mixing mechanism of C contaminant on W
substrate under high-flux, low-energy ion irradiation;
– the experimentally observable anomalous deep C transport into W under prolonged irradiation at elevated temperature.
The aim:– to deepen the understanding about the behavior
of C contaminant on W .
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MD simulations for WC targetMD simulations for WC target
Helsinki University, 2005
T=300 K
20 eV H+ 200 eV H+20 eV H+ WC
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Lithuanian energy institute Materials Research and Testing Laboratory
SEM surface views of W film after irradiation SEM surface views of W film after irradiation during redeposition when sputtering prevailsduring redeposition when sputtering prevails
0,5 m 0,5 m
2 m 1 m
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W surface roughness after irradiation during redeposition
After irradiation during carbon redeposition
Roughness: Ra=2.9 nm Ra=13.5 nm Ra=38.3
Not-irradiated
5 µm
Va > Vs
29 µm
Vs > Va
29 µm
VI International Conference ION 2006 , Kazimierz DolnyKazimierz Dolny,, Poland, 26-29 June 2006Poland, 26-29 June 2006
AFM surface topography to the C transport AFM surface topography to the C transport into the W film mechanisminto the W film mechanism
VI International Conference ION 2006 , Kazimierz DolnyKazimierz Dolny,, Poland, 26-29 June 2006Poland, 26-29 June 2006
28 µm 1.5 µm
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Boundary region
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XRD patterns of W film on the graphite XRD patterns of W film on the graphite substratesubstrate
W2C
VaVs
Diffraction angle, 2 Diffraction angle, 2
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XRD patterns of W film on the graphite XRD patterns of W film on the graphite substratesubstrate
Diffraction angle, 2
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Mechanical erosion by pin-on disc techniqueMechanical erosion by pin-on disc technique
As-deposited W film W film after C redeposition under irradiation
20
0
- 20
-400 400
400
800
800
1200
1200
0
x , m
z,
m
y, m
2
0
-2
-4 0 40 80 120
0 40
80
1
2020
0
- 20
-400 400
400
800
800
1200
1200
0
x , m
z,
m
y, m
0 40 80 120
2
0
-2
-4
0 40
80
1
20
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DiscussionsDiscussions
The main deduced results:
– the dynamic mixing results in the formation of an layer (modeling);
– the efficient C transport from the surface into W film takes place during the weight decrease regime when W surface is only partially covered by C atoms (experiment);
– the C transport efficiency sharply decreases when continuous amorphous C film is formed on the W surface (experiment).
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DiscussionsDiscussions
The deduced results may be explained if to assume:
– during high-flux, low-energy ion irradiation the surface chemical potential of W increases and difference of potentials between activated surface and grain boundaries acts as the driving force for C adatoms transporting them into the bulk of W film;
– as continuous amorphous C layer is formed on the W surface the transport of C adatoms from the surface is blocked;
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ConclusionsConclusions
VI International Conference ION 2006 , Kazimierz DolnyKazimierz Dolny,, Poland, 26-29 June 2006Poland, 26-29 June 2006
The redeposition and surface relocation effects
forms: (i) steady state mixed layer on the surface in the
regime of surface erosion, (ii) formation of continuous
film in the regime when redeposition prevails, and (iii)
mixed layer with thickness increasing in time as
where
tDef )()2/1( 20 asef VVhD
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ConclusionsConclusions
- The surface roughness increases when
sputtering yield of surface contaminants is low in
comparison with matrix material;
- The efficient carbon transport from the surface into the W film was observed in the regime when sputtering prevails redeposition.
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The model application to the published The model application to the published experimental resultsexperimental results
Calculated (grey lines) and experimental depth profiles of carbon for target temperatures from 653 K to 1050 K. Beam fluence is 3×1024 m-2.
Y. Ueda, Y. Tanabe, etc., J. Nucl. Mater, 2004,
W by 1.0 ke V of 0.1 % C+ and H3+ beam, flux - 31020 m-2∙s-1,
fluence – 1022 -1024 m-2, T=653 -1050 K
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The model application to the published The model application to the published experimental resultsexperimental results
Calculated and experimental depth profiles of Ti in natural U
P=10E-2 Pa
Irradiation time -5 min
Ion energy – 2.7 keV
Flux – 1.3×1020 m-2s-1
βU = 0.83, βTi = 0.89
V.I. Safonov, I. G. Marchenko, etc., surf. Coat. Technol., 2003, V by 2.7 keV Ti+, flux - 31020 m-2∙s-1,