1 deuterium retention in tungsten exposed to carbon-seeded deuterium plasma * igor i. arkhipov,...
TRANSCRIPT
1
DEUTERIUM RETENTION IN TUNGSTEN EXPOSED TO CARBON-SEEDED DEUTERIUM PLASMA *
Igor I. Arkhipov, Vladimir Kh. Alimov, Dmitrii A. KomarovRion A. Causey*, Robert D. Kolasinski*
A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, RAS, Moscow, Russia
*Sandia National Laboratories, Livermore, USA
Outline
1. Introduction
2. Experimental
3. Results & Discussion
4. Conclusions
*This work was supported by the United States Department of Energy under Contract 512244 with Sandia National Laboratories
2
Irradiation conditions
Pdiv, Pa Flux, D/m2s Ei, eV* C, at.% Tsur, K
ITER divertor [1] 4 ~1×1023-24 ≤100 ? 520 & 850
JET [2] ≤20 4 380-520
PISCES-B [3] ~1×1022 100 0.5; 1; 1.4 350-1200
Ion source [4] ~4×10-5 ~6×1019 500 1 300, 500
Magnetron [5] 1 ~1×1021 400 ≤1 390-1000
Introduction
[1] G.Federici et al., J. Nucl. Mater. 313-316 (2003) 11-22[2] J.P. Coad, et.al., J. Nucl. Mater. 313-316 (2003) 419-423[3] F.C. Sze et.al., J. Nucl. Mater. 266-269 (1999) 1212-1218[4] M.Poon, et al., J. Nucl. Mater. 337-339 (2005) 629-633[5] This work
3
Irradiation conditions
Pdiv, Pa Flux, D/m2s Ei, eV* C, at.% Tsur, K
ITER divertor [1] 4 ~1×1023-24 ≤100 ? 520 & 850
JET [2] ≤20 4 380-520
PISCES-B [3] ~1×1022 100 0.5; 1; 1.4 350-1200
Ion source [4] ~4×10-5 ~6×1019 500 1 300, 500
Magnetron [5] 1 ~1×1021 400 ≤1 390-1000
Introduction
[1] G.Federici et al., J. Nucl. Mater. 313-316 (2003) 11-22[2] J.P. Coad, et.al., J. Nucl. Mater. 313-316 (2003) 419-423[3] F.C. Sze et.al., J. Nucl. Mater. 266-269 (1999) 1212-1218[4] M. Poon, et al., J. Nucl. Mater. 337-339 (2005) 629-633[5] This work
4
Distribution of erosion/deposition areas in the JET divertor (1999-2001)*
*P.Coad, et al., J. Nucl. Mater. 313-316 (2003) 419
Introduction Material migration in divertor tokamaks
5
Sputtering yields curves for fusion relevant materials for irradiation by deuterium*(Physical sputtering yields for some ion mass are plotted in the case of W)
*G.F. Matthews, J. Nucl. Mater. 337-339 (2005) 1-9
Introduction
100
Erosion of carbon by deuterium
6
Scheme of erosion/re-deposition processes within the divertor*
*G.F. Matthews, J. Nucl. Mater. 337-339 (2005) 1-9
IntroductionMaterial migration in divertor tokamaks
7
Ion impact energy at the outer divertor target for a completely detached N2 seeded shorts in JET. The effect of ELMs of different sizes is shown*
Introduction
*G.F. Matthews, J. Nucl. Mater. 337-339 (2005) 1-9
Erosion of tungsten by tritium
8
D retention in C seeded D-plasma exposed W Experimental results
Dominant factors: 1. substrate temperature 2. whether carbon is deposited on the W surface
There is a carbon-impurity concentration of beginning of C-deposition:• 0.75% at 850 K• 1% at 750 K
Uncontaminated surface: 1. Blisters, bubbles and/or pits are formed 2. D retention decreases with temperature increase
C-contaminated surface: 1. a-C:D film or/and W2C layer are formed
2. D retention in C-contaminated W larger than in uncontaminated one• The most of deuterium are residing in the carbon films• Thin a-C:D film or W2C layer can significantly decrease D-retention in W
Introduction
9
D retention in C seeded D-plasma exposed W Experimental results
Dominant factors: 1. substrate temperature 2. whether carbon is deposited on the W surface
There is a carbon-impurity concentration of beginning of C-deposition:• 0.75% at 850 K• 1% at 750 K
Uncontaminated surface: 1. Blisters, bubbles and/or pits are formed 2. D retention decreases with temperature increase
C-contaminated surface: 1. a-C:D film or/and W2C layer are formed
2. D retention in C-contaminated W larger than in uncontaminated one• The most of deuterium are residing in the carbon films• Thin a-C:D film or W2C layer can significantly decrease D-retention in W
Introduction
10
D retention in C seeded D-plasma exposed W Experimental results
Dominant factors: 1. substrate temperature 2. whether carbon is deposited on the W surface
There is a carbon-impurity concentration of beginning of C-deposition:• 0.75% at 850 K• 1% at 750 K
Uncontaminated surface: 1. Blisters, bubbles and/or pits are formed 2. D retention decreases with temperature increase
C-contaminated surface: 1. a-C:D film or/and W2C layer are formed
2. D retention in C-contaminated W larger than in uncontaminated one• The most of deuterium are residing in the carbon films• Thin a-C:D film or W2C layer can significantly decrease D-retention in W
Introduction
11
D retention in C seeded D-plasma exposed W Experimental results
Dominant factors: 1. substrate temperature 2. whether carbon is deposited on the W surface
There is a carbon-impurity concentration of beginning of C-deposition:• 0.75% at 850 K• 1% at 750 K
Uncontaminated surface: 1. Blisters, bubbles and/or pits are formed 2. D retention decreases with temperature increase
C-contaminated surface: 1. a-C:D film or/and W2C layer are formed
2. D retention in C-contaminated W larger than in uncontaminated one• The most of deuterium are residing in the carbon films• Thin a-C:D film or W2C layer can significantly decrease D-retention in W
Introduction
12
Sputtering yields curves for fusion relevant materials for irradiation by deuterium*(Physical sputtering yields for some ion mass are plotted in the case of W)
*G.F. Matthews, J. Nucl. Mater. 337-339 (2005) 1-9
Introduction
100
Erosion of tungsten by carbon
13
W erosion as function of Te and C impurity concentration*
*K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310
Introduction Erosion of tungsten by carbon
14
In this work:
Partially contaminated surface in C-seeded D-plasma
Introduction
15
Top view of magnetron cathode surfaceExperimental
Ta mask
(6×8×0.5 mm3)
16
Irradiation conditions
Pdiv, Pa Flux, D/m2s Ei, eV* C, at.% Tsur, K
ITER divertor [1] 4 ~1×1023-24 ≤100 ? 520 & 850
JET [2] ≤20 4 380-520
PISCES-B [3] ~1×1022 100 0.5; 1; 1.4 350-1200
Ion source [4] ~4×10-5 ~6×1019 500 1 300, 500
Magnetron [5] 1 ~1×1021 400 ≤4 363-773
[1] G.Federici et al., J. Nucl. Mater. 313-316 (2003) 11-22[2] J.P. Coad, et.al., J. Nucl. Mater. 313-316 (2003) 419-423[3] F.C. Sze et.al., J. Nucl. Mater. 266-269 (1999) 1212-1218[4] M.Poon, et al., J. Nucl. Mater. 337-339 (2005) 629-633[5] This work
Experimental
17
Irradiation conditions
Pdiv, Pa Flux, D/m2s Ei*, eV At.% C Tsurface, K
ITER [1] 4 ~1×1023-24 ≤100 ? 520 & 850
JET [2] ≤20 4 380-520
PISCES-B [3] ~2×1022 100 0.5; 1; 1.4 350-1200
Ion source [4] ~4×10-5 ~6×1019 500 1 300, 500
Magnetron [5] 1 ~1×1021 400 ≤4 363-773
Experimental
[1] G.Federici et al., J. Nucl. Mater. 313-316 (2003) 11-22[2] J.P. Coad, et.al., J. Nucl. Mater. 313-316 (2003) 419-423[3] F.C. Sze et.al., J. Nucl. Mater. 266-269 (1999) 1212-1218[4] M.Poon, et al., J. Nucl. Mater. 337-339 (2005) 629-633[5] This work
*Ei≈ZUsheath + 2Ti ≈ Te(3Z+1), Usheath≈3Te/e0
Ti≈Te/2
Ei- ion impact energyZ- charge state of the impacting ionUsheath- sheath potentialTe& Ti – temperatures of electrons and ions
18
Irradiation conditions
Pdiv, Pa Flux, D/m2s Ei, eV At.% C Tsurface, K
ITER [1] 4 ~1×1023-24 ≤100 ? 520 & 850
JET [2] ≤20 4 380-520
PISCES-B [3] ~1×1022 100 0.5; 1; 1.4 350-1200
Ion source [4] ~4×10-5 ~6×1019 500 1 300, 500
Magnetron [5] 1 ~1×1021 400 ≤4 363-773
Experimental
[1] G.Federici et al., J. Nucl. Mater. 313-316 (2003) 11-22[2] J.P. Coad, et.al., J. Nucl. Mater. 313-316 (2003) 419-423[3] F.C. Sze et.al., J. Nucl. Mater. 266-269 (1999) 1212-1218[4] M.Poon, et al., J. Nucl. Mater. 337-339 (2005) 629-633[5] This work
19
W erosion as function of Te and C impurity concentration*
*K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310
Introduction Erosion of tungsten by carbon
20
Experimental conditions
Ei=400 eV Rp, nm
(SRIM 2003)
Kerosion Kdiffusion
(m2s-1)
Conclusion R
D2+→W 2 - 1× 10-9 * No limits for diffusion 1
C+→W 1 0.1 1× 10-19 ** Thin C-W mixed layer 2
Experimental
D ion energy, eV Time, sec Flux,
(m-2s-1)
Fluence,
(m-2s-1)
Erosion,
nm/sec
200 1800 1× 1019 2× 1024 ≤1 nm/sec
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388[2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310
* T=770 K
**T=1030 K
21
Erosion of tungsten
Experimental
Estimation: V erosion=1.5-2 μm/30 min ~1 nm/s ~6×1019 at.W/m2s
Closed area
Plasma-impact area
Interference fringes(Linnik micro-interferometer)
Initial surface
Eroded surface
22
Sputtering yields curves for fusion relevant materials for irradiation by deuterium*(Physical sputtering yields for some ion mass are plotted in the case of W)
*G.F. Matthews, J. Nucl. Mater. 337-339 (2005) 1-9
Experimental Erosion of tungsten by carbon
23
Experimental conditions
Ei=400 eV Rp, nm
(SRIM 2003)
Kerosion Kdiffusion
(m2s-1)
Conclusion R
D2+→W 2 - 1× 10-9 * No limits for diffusion 1
C+→W 1 0.1 1× 10-19 ** Thin C-W mixed layer 2
Experimental
D ion energy, eV Time, sec Flux,
(m-2s-1)
Fluence,
(m-2s-1)
Erosion,
W at./m2s
200 1800 1× 1019 2× 1024 ≤6×1019
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388[2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310
* T=770 K
**T=1030 K
1%C in plasma: 1018 C/m2s→ 1017 W/m2s
24
Irradiation T, K Eth, eV Kerosion at Ei= 400 eV
C+, N+, O+ →W 293 ~35 ~ 0.1
Ta+ →W 293 ~2
D2+→W 293 160-200 ≤0.0001
D2+→WO 293 65
D2+→WC 293 150 ≤ 0.0001
The threshold energies of sputtering
Experimental
25
DEUTERIUM RETENTION IN TUNGSTENAT HIGH LEVEL OF SURFACE EROSION
Experimental
26
Experimental conditions
Ei=400 eV Rp, nm
(SRIM 2003)
Kerosion Kdiffusion
(m2s-1)
Conclusion R
D2+→W 2 - ~ 1× 10-9 * No limits for diffusion 1
C+→W 1 0.1 ~ 1× 10-19 ** Thin C-W mixed layer 2
Experimental
D ion energy, eV
Time, sec
Flux,
(m-2s-1)
Fluence,
(m-2s-1)
Erosion,
W at./m2sec
Temperature,
K
200 1800 1× 1019 2× 1024 ~6×1019 363-773
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388[2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310
* T= 773 K
**T=1030 K
27
Diffusion coefficient for C in a wide concentration range for C in W*
*K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310
Introduction
28
Experimental conditions
Ei=400 eV Rp, nm
(SRIM 2003)
Kerosion Kdiffusion
(m2s-1)
Conclusion R
D2+→W 2 - ~ 1× 10-9 * No limits for diffusion 1
C+→W 1 0.1 ~ 1× 10-19 ** Thin C-W mixed layer 2
Experimental
D ion energy, eV
Time, sec
Flux,
(m-2s-1)
Fluence,
(m-2s-1)
Erosion,
W at./m2sec
Temperature,
K
200 1800 1× 1019 2× 1024 ~6×1019 363-773
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388[2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310
* T= 773 K
**T=1030 K
29
Experimental conditions
Ei=400 eV Rp, nm
(SRIM 2003)
Kerosion Kdiffusion
(m2s-1)
Conclusion R
D2+→W 2 - ~ 1× 10-9 * No limits for diffusion 1
C+→W 1 0.1 ~ 1× 10-19 ** Thin C-W mixed layer 2
Experimental
D ion energy, eV
Time, sec
Flux,
(m-2s-1)
Fluence,
(m-2s-1)
Erosion,
W at./m2sec
Temperature,
K
200 1800 1× 1019 2× 1024 ~6×1019 363-773
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388[2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310
* T= 773 K
**T=1030 K
30
H diffusivity vs temperature for W773 K
E. Serra, G. Benamati, O.V. Ogorodnikova, J. Nucl. Mater. 255 (1998) 105-115
Experimental
31
H diffusivity vs temperature for W773 K
R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388
Experimental
32
H diffusivity vs temperature for W773 K
A.P. Zakharov, V.M. Sharapov, E.I. Evko, Soviet Mater. Sci. 9 (1973) 149
Experimental
33
Experimental conditions
Ei=400 eV Rp, nm
(SRIM 2003)
Kerosion Kdiffusion
(m2s-1)
Conclusion R
D2+→W 2 - ~ 1× 10-9 * No limits for diffusion 1
C+→W 1 0.1 ~ 1× 10-19 ** Thin C-W mixed layer 2
Experimental
D ion energy, eV
Time, sec
Flux,
(m-2s-1)
Fluence,
(m-2s-1)
Erosion,
W at./m2sec
Temperature,
K
200 1800 1× 1019 2× 1024 ~6×1019 363-773
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388[2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310
* T= 773 K
**T=1030 K
Kdiffusion ~ 1× 10-9 m2s-1 →h=(Dt)1/2~ 1mm
34
Methods of the analysisExperimental
Mechanically & electrochemically polishedHot-rolled tungsten foil (99.0 at.%)
Size = 6×8×0.5 mm3
C/D-plasma irradiation: planar DC magnetron Eions (D2+; C+; N+, O+, Ta+)= 400 eV
Flux=1×1019 D/m2s, 30 min
Deuterium profiles:Nuclear Reaction Analysis (NRA):• 0 - 0.5 μm: D(3He,α)H reaction•0.5 - 7 μm: D(3He,p)4He reaction
Deuterium retention:Thermal Desorption Spectroscopy (TDS)•D2 & HD molecules were detected by QMS•Temperature range: 300-1100 K•Heating rate = 3.2 K/s
Profiles & chemical state of impurities:X-ray Photoelectron Spectroscopy (XPS)• Depth profiles of C, O, W • 3 kev Ar+, 2×2 mm2, 0.4 μm
35
NRA & TDS data
300 400 500 600 700 800Irradiation tem perature, K
0
2
4
6
8
1
3
5
7D
eute
riu
m r
eten
tio
n,
×10
20
D/m
2 D+C- plasma, 200 eV D+, ~2×1024 D/m2
NRA data, 0-7 mTDS data
Results & Discussion
6
m
36
NRA data
0 1 2 3 4 5 6 710 -4
10 -3
10 -2
10 -1
100 363 K 383 K 463 K 563 K 653 K 773 K
D c
on
ce
ntr
ati
on
[a
t.%
]
Depth [m]
Results & Discussion
3
37
XPS data
2 9 0 2 8 8 2 8 6 2 8 4 2 8 2 2 8 0
4 0 0 c /s
C 1s
D + C p la s m aT
exp = 3 8 3 K
g ra p h ite
D p la s m aT
exp = 4 9 3 K
W2C
W C
d is o rd e re d CX
PS
in
ten
sit
y
B in d in g en erg y [eV ]
Results & Discussion
(3 keV Ar at fluence=1×1019 Ar/m2 )
38
NRA data
0 1 2 3 4 5 6 710 -4
10 -3
10 -2
10 -1
100 363 K 383 K 463 K 563 K 653 K 773 K
D c
on
ce
ntr
ati
on
[a
t.%
]
Depth [m]
Results & Discussion
3
39
Blistering in the temperature range 363-653 K
Results & Discussion
Pre-TDS; T=563 K at fluence=2× 1024 D/m2
40
TDS data
0 100 200Time, s
0
4
8
12
2
6
10
Des
orp
tio
n f
lux,
×10
18 D
/m2 s
400
600
800
1000
300
500
700
900
Tem
per
atu
re,
K
D+C plasm a W PC363 K383 K463 K563 K653 K773 KTemperature
Results & Discussion
41
TDS dataResults & Discussion
300 400 500 600 700 800Irradiation tem perature, K
0
2
4
6
1
3
5
7
Deu
teri
um
ret
enti
on
, ×
102
0 D
/m2 D+C- plasma, 200 eV D+, ~2×1024 D/m2
First peakSecond peak
T1=650-710 KT2=900-1000 K
42
TDS modeling: contributions from 1.4 eV traps and blisters (TMAP7)
at 563 K
Results & Discussion
1.0
0.8
0.6
0.4
0.2
0.0
De
sorb
ed
Flu
x (n
orm
aliz
ed
)
1000800600400
Temperature (K)
TMAP7 Simulated TDS spectrum563 K exposure temperature
1.4 eV trap contribution blister (100 nm caps) bister (1 micron caps) blister (5 micron caps)
43
Three types of traps can explain our TDS data
1. Near-surface layer (≤ 0.5 m): 1.4 eV traps=
one D in vacancy
2. Sub-surface layer (≤ 7 m): 1.8-2.1 eV=D chemisorption on blister/bubble wall + D2 molecules inside
3. Bulk (up to 1 mm): 1.8-2.1 eV traps=
D chemisorption on inner walls of small cavity and voids
44
Fitting of TDS data are in progress
45
NRA & TDS data
300 400 500 600 700 800Irradiation tem perature, K
0
2
4
6
8
1
3
5
7D
eute
riu
m r
eten
tio
n,
×10
20
D/m
2 D+C- plasma, 200 eV D+, ~2×1024 D/m2
NRA data, 0-7 mTDS data
Results & Discussion
Bulk trapping !
m
46
General experimental results
Strong W sputtering
Blistering
Enhanced D retention
NRA ≈ TDS from 363 to 563 K
NRA<<TDS from 563 to 773 K
Results & Discussion
47
General conclusions
Blistering & enhanced D retention even at strong W surface sputtering are revealed Irradiation temperature of 550-600 K corresponds to
transition from a near/sub-surface to a bulk D trapping in polycrystalline W foils
Carbon influence: enhanced W erosion;
W2C barrier layer formation & increased D retention
Conclusions
48
General conclusions
Blistering & enhanced D retention even at strong W surface sputtering are revealed Irradiation temperature of 550-600 K corresponds to
transition from a near-surface to a bulk D trapping in polycrystalline W
Carbon influence: enhanced W erosion;
W2C barrier layer formation & enhanced D retention
Conclusions
49
General conclusions
Blistering & enhanced D retention even at strong W surface sputtering are revealed
Irradiation temperature of 550-600 K corresponds
to transition from a near-surface to a bulk D trapping in polycrystalline W
Carbon influence:
enhanced W erosion;W2C barrier layer formation & enhanced bulk D retention
Conclusions
50
Scheme of plasma-surface interaction
W
Carbon-modified layer (W2C, WC)
D-C plasma
D stop diffusion & retention
No erosion
a-C:H film
4 nm
51
Scheme of plasma-surface interaction
W
Carbon-modified layer (W2C, WC)
D-C plasma no limits for diffusion high retention level in bulk
Erosion rate 1 nm/s
D
1 nm
2 m
a-C:H film
52
To be or not to be for D retention in Wstrongly depends on irradiation
parameters and surface conditions
53
Thank you for attention