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Influence of the presence of deuterium on displacement damage in tungsten T. Schwarz-Selinger 1 , J. Bauer 1 , S. Elgeti 1 M. Pe ovnik 2 , S. Markelj 2 1 2 Theoretical predictions - DFT molecular dynamics revealed that hydrogen clusters

slide-1
SLIDE 1

Influence of the presence of deuterium

  • n displacement damage in tungsten
  • T. Schwarz-Selinger1, J. Bauer1, S. Elgeti1
  • M. Pečovnik2, S. Markelj2

1 2

slide-2
SLIDE 2

Theoretical predictions

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 2

  • ‘DFT molecular dynamics revealed that

hydrogen clusters can prevent a vacancy from recombining with the neighboring crowdion-type self-interstitial-atom.’

  • D. K

Kato

  • et al., Nuc
  • ucl. Fus

Fusion

  • n 55

55 (2 (201 015) 5) 08 0830 3019 19

  • ‘Atomic scale computer simulations have

predicted a decrease in the W vacancy formation energy in the presence of H … Findings of this work suggest that H not only promotes vacancy formation in W, but once formed the vacancy will also initiate further H clustering’ S.C. Midd ddlebur urgh gh, J. Nuc

  • ucl. M
  • Mater. 44

448 8 (2 (201 014) 4) 270 270

slide-3
SLIDE 3

Motivation

In a future fusion reactor: In present day lab experiments:

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 3

 mutual influence of D on damage creation/evolution? 14 MeV n D T D T T D D-T plasma

bulk W

20 MeV W D plasma

+

D D D D D D

slide-4
SLIDE 4

Experimental strategy

Shown before by Sabina:

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 4

10.8 MeV W D D D D D sequentially or simultaneously + additional D decoration

slide-5
SLIDE 5

Experimental strategy

Approach here: sequential treatment

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 5

+

20 MeV W

D/W 1.7 at.%

D plasma D D D D D D

D/W 1.7 at.%?

20 MeV W D D D D D D

+ + …

D D D D D D D D D D D plasma D D

+

x at.% ?

multiple times

slide-6
SLIDE 6

Experimental strategy

  • Compare D retention in
  • tungsten free of D
  • tungsten ‘saturated with D’

after 20 MeV W bombardment and D decoration of defects  Questions to address beforehand:

  • D uptake as function of W damaging fluence (Does damage saturate?)
  • D uptake as function of D fluence (How to decorate defects without

creating new ones?)

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 6

slide-7
SLIDE 7

Outline

  • Motivation
  • D retention in self-damaged tungsten
  • Multiple sequence experiments: Damage creation D loading

D depth profiles and thermal desorption data

  • Present rate equation modelling approaches

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 7

slide-8
SLIDE 8

A comment before I start

  • High energy and/or high flux D (plasma) exposure leads to
  • H oversaturation

[L.Gao et al., Nucl. Fusion 2017 https://doi.org/10.1088/0029-5515/57/1/016026]

  • damage creation (point defects … blisters)

which we want to avoid in this study (not trivial, see e.g.

  • S. Kapser et al., Nucl. Fusion, 2018 http://dx.doi.org/10.1088/1741-4326/aab571)
  • The strategy here is to investigate the effect of displacement damage,

hence D loading needs to be done without creating new damage

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 8

slide-9
SLIDE 9

D decoration: gentle plasma exposure

  • known flux and energy
  • energy: „<5 eV/D“ (floating targets)
  • ion flux: 6 ×1019 D/(m2s)

(97% as D3 +, 2% as D2 +, 1% as D+)

  • atom flux > 1021 D0/(m2s)
  • ion fluence: up to 5·1024 D/m2 per day
  • ’gentle’ loading = ‘decoration’:

T = 370 K

  • no additional defect creation
  • no defect evolution/annealing)
  • six samples simultaneously

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 9

PlaQ:

  • A. Manhard, Plasma Sources Sci. Technol. 20

20 (2011) 015010

slide-10
SLIDE 10

The tungsten substrate material

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 10

  • Plansee AG hot-rolled tungsten, purity 99.97 wt.-%
  • chemo-mechanically polished to mirror finish [1]
  • annealed at 2000 K for 2 min at p < 5 ×10-8 mbar

to reduce initial defect density

  • to 2×1012 m/m3 [2]

[1] A. Manhard et al., Pract. Metallogr. 50 (1) (2013) 6–15. [2] A. Manhard et al., Pract. Metallorg. 52 (2015) 437. confocal scanning laser microscopy

slide-11
SLIDE 11

Creating displacement damage: W self-implantation

  • 14 MeV fusion neutrons will cause
  • transmutation
  • gas production
  • displacement damage (Epka < 200 keV)
  • Here: only displacement damage aspect is studied with W self-implantation

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 11

Why tungsten ions? + no chemical effects + dense cascades + fast: 1 dpa in 1 hour

  • vacancies, vacancy clusters,

voids, ….

  • too high Epka

≈ µm

20 MeV W in W SRIM 2013 target atoms projectile

slide-12
SLIDE 12

2.3 μm

Creating displacement damage: W self-implantation

  • 300 keV W would reduce information depth to 30 nm : Too little material for

diagnostics (nuclear reaction analysis, thermal desorption spectroscopy)

  • Cascade splitting makes it still relevant (?)

[A. Sand et al. Mater. Res. Lett. 5 (5), 357–63 (2017)]

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 12

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.00 0.05 0.10 0.15 0.20 0.25 0.30

Calculated displacments (dpaKP) Depth (m) SRIM 2013 20 MeV W 7.810

17 W/m 2

with Edis= 90 eV*

J. . Gr Grzonka

  • nka et

t al. l., , NI NIMB B Vol

  • l 340,

40, p. . 27 27 (201 2014) 4)

STEM micrograph

slide-13
SLIDE 13

2.3 μm

1 2 3 4 5 10

  • 3

10

  • 2

10

  • 1

10 10

  • 3

10

  • 2

10

  • 1

10

0.23 dpa 0.1 dpa 0.023 dpa 0.005 dpa 0.001 dpa

D atomic fraction (at.%) depth (m)

SRIM 0 dpa

calculated displacement damage (a.u.)

detection limit

D retention in self-damaged W

Previous investigation:

  • fluence series 20 MeV W6+ @ 290 K
  • D decoration with < 5 eV/D

for 72 h (1.5 ×1025 D/m2) @ 450 K

  • D/W > 1 at.% @ 0.23 dpa

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 13

Ł. ń

slide-14
SLIDE 14

D retention in self-damaged W

Previous investigation:

  • fluence series 20 MeV W6+ @ 290 K
  • D decoration with < 5 eV/D

for 72 h (1.5 ×1025 D/m2) @ 450K

  • D/W > 1 at.% @ 0.23 dpa
  • linear increase for < 0.005 dpa
  • saturation in D for > 0.23 dpa

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 14

Ł. ń

0.01 0.1 1 10 5E-4 0.005 0.05 0.5 5 0.01 0.1 1 10

D atomic fraction (at. %) peak displacement damage (dpaNRT)

D decoration at 450 K < 5 eV/D

Total D amount (10

17)

TPD NRA @ 1.25 m

slide-15
SLIDE 15

D retention in self-damaged W

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 15

Ł. ń

1 2 3 4 5 1 2

0.00 0.05 0.10 0.15 0.20 0.25

D atomic fraction (at.%) depth (m)

D [10

25 D/m 2]

2.25 1.55 1.45 0.40 0.10

A0449, A0454, A0451, 0.23 dpa, PlaQ, floating, 450K

calculated displacement damage (dpaKP)

Previous investigation:

  • fluence series 20 MeV W6+ @ 290 K
  • D decoration with < 5 eV/D

for 72 h (1.5 ×1025 D/m2) @ 450K

  • D/W > 1 at.% @ 0.23 dpa
  • linear increase for < 0.005 dpa
  • saturation in D for > 0.23 dpa
slide-16
SLIDE 16

D retention in self-damaged W

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 16

Ł. ń

1 2 0.0 0.5 1.0 1.5 2.0

integrated deuterium amount (10

17 D)

deuterium fluence (10

25 D/m 2)

Previous investigation:

  • fluence series 20 MeV W6+ @ 290 K
  • D decoration with < 5 eV/D

for 72 h (1.5 ×1025 D/m2) @ 450K

  • D/W > 1 at.% @ 0.23 dpa
  • linear increase for < 0.005 dpa
  • saturation in D for > 0.23 dpa
slide-17
SLIDE 17

Saturating displacement damage with D

This study:

  • D decoration @ 370 K
  • 2 times 1.5·1025 D/m2 (2 x 72 h)
  • check if damaged zone

is completely filled with D  It is, up to 1.7 at.% Doubling the D fluence does not increase D amount

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 17

1 2 3 4 5 0.0 0.5 1.0 1.5 2.0

0.0 0.1 0.2 0.3 0.4

1

st D decoration

+ 2

nd D decoration

D atomic fraction (at. %) Depth (m)

*1 times / 2 times PlaQ 72h, 370K, floating; **20MeV 0.23 dpa

damage (dpaKP)

SRIM

slide-18
SLIDE 18

D retention in self-damaged W

  • beam sweep for laterally

homogenous damage

  • accuracy, reproducibility:

better than 5%  box like D reservoir

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 18

Ł. ń

5 10 15 0.8 1.0 1.2 5 10 0.8 1.0 1.2 long axis (mm)

normalized proton integral (a.u.)

short axis (mm)

normalized proton integral (a.u.)

D145

slide-19
SLIDE 19

Displacements during 20 MeV W

SDTrimSP calculation:

  • 20 MeV W on W, containing 2 % D
  •  = 7.87×1017 W6+/m2
  • displacement energy
  • Edispl. W = 90 eV, Ecutoff, W = 2.2 eV
  • Edispl, D = 1 eV, Ecutoff, D = 0.25 eV

 tungsten atoms are displaced and defects are generated (0.23 dpa)  simultaneously, retained deuterium atoms (1.7%!) are de-trapped in the vicinity of the displacement damage: kinetic detrapping

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 19

 Until IBIS isn’t ready: ‘simultaneous for the poor’

  • ‘Recrystallized W’

– μ

  • ≙
  • ≙
  • 0.0

0.5 1.0 1.5 2.0 2.5 0.0 0.2 0.4 0.6 0.8 1.0 1.2

0.0 0.2 0.4 0.6 0.8 1.0 1.2

fraction of displaced W fraction of detrapped D depth [m]

slide-20
SLIDE 20

D depth profiles

What happens to the initially retained D?

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 20

1 2 3 4 5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.2 0.4 0.6 0.8

D atomic fraction (at. %) depth (m)

1

st D decoration

damage (dpaKP)

SRIM

slide-21
SLIDE 21

D depth profiles

What happens to the initially retained D?  no change in depth profile  D gets efficiently re-trapped during W implantation

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 21

1 2 3 4 5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.2 0.4 0.6 0.8

D atomic fraction (at. %) depth (m)

1

st D decoration

+ 2

nd W implantation

damage (dpaKP)

SRIM

slide-22
SLIDE 22

D effusion during thermal desorption

What happens to the D binding?

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 22

5000 10000 15000 2 4 6 8 1

st D decoration

D Effusion Flux [10

17 D m

  • 2s
  • 1]

time [s]

400 600 800 1000

temperature [K]

slide-23
SLIDE 23

D effusion during thermal desorption

What happens to the D binding?  shift of desorption to larger desorption energies!  new trap types?

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 23

5000 10000 15000 2 4 6 8 1

st D decoration

+ 2

nd W implantation

D effusion Flux [10

17 D m

  • 2s
  • 1]

time [s]

400 600 800 1000

temperature [K]

slide-24
SLIDE 24

D depth profiles

Decoration after 2nd damaging:  D retention increases to 2.8 at.% (!) exceeding D at. fraction by ≈ factor 2 beyond previous ‘saturation value’!  new trap types now filled?

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 24

1 2 3 4 5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.2 0.4 0.6 0.8

D atomic fraction (at. %) depth (m)

1

st D decoration

+ 2

nd W implantation

+ 2

nd D decoration

damage (dpaKP)

SRIM

slide-25
SLIDE 25

Thermal desorption spectroscopy

Decoration after 2nd damaging:  TDS spectra resembles again the spectrum of the initially decorated, singly damaged W!  only larger intensity  same trap types?

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 25

5000 10000 15000 2 4 6 8 + 2

nd D decoration

+ 2

nd W implantation

1

st D decoration

D effusion Flux [10

17 D m

  • 2s
  • 1]

time [s]

400 600 800 1000

temperature [K]

slide-26
SLIDE 26

Artefact from surface blisters?

Suspicion:

  • increased retention due to surface blisters?

(unlikely giving the same depth profile)

  • 30 SEM micrographs (30 µm in size) show no

indication on gas filled cavities

  • in line with dedicated studies such as a
  • S. Kapser et al., Nucl. Fusion
  • in line with lack of D2 bursts in TDS spectra

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 26

SE images

slide-27
SLIDE 27

Rate equation modelling

TESSIM-X code with fill-level-dependent trapping [K. Schmid et al. JAP 116, 134901 (2014)]

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 27

5000 10000 15000 2 4 6 8 experiment model

D Effusion Flux [10

17 D m

  • 2s
  • 1]

time [s]

400 600 800 1000

Temperature [K]

Parameters from previous isotope exchange study:

  • diffusion coefficient

D0 = 1.58×10-7/2 , Ediff = 0.25 eV

  • one trap type with five fill-levels,

(Edetrap = 1.18 eV, 1.32 eV, 1.46 eV, 1.7 eV, 1.84 eV, 0 = 1 x1013 s-1),

  • trap profile constant down to 2.2 µm
slide-28
SLIDE 28

Rate equation modelling

TESSIM-X code with fill-level-dependent trapping [K. Schmid et al. JAP 116, 134901 (2014)]

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 28

5000 10000 15000 2 4 6 8 experiment model

D Effusion Flux [10

17 D m

  • 2s
  • 1]

time [s]

400 600 800 1000

Temperature [K]

  • creation of additional empty traps

(by a factor of 1.7 during 2nd W implantation) explains temperature shift!

  • TDS spectra with and without

kinetic de-trapping indistinguishable

slide-29
SLIDE 29

Rate equation modelling

TESSIM-X code with fill-level-dependent trapping [K. Schmid et al. JAP 116, 134901 (2014)]

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 29

5000 10000 15000 2 4 6 8 3

rd W-D

2

nd W-D

experiment model

D Effusion Flux [10

17 D m

  • 2s
  • 1]

time [s]

1

st W-D

400 600 800 1000

Temperature [K]

  • creation of additional empty traps

(by a factor of 1.7 during 2nd W implantation) explains temperature shift!

  • TDS spectra with and without

kinetic de-trapping indistinguishable

slide-30
SLIDE 30

Rate equation modelling

  • evolution of D solute concentration

during 50 minutes W damaging

  • differentiation between solute

and retained D meaningful on timescale of damage cascade?

  • D is static on ps timescale

(1 Å in 1 ps @ 2000 K) See: T. Schwarz-Selinger et al. Nucl. Mater. Energy 17 (2017): 228–34. https://doi.org/10.1016/j.nme.2018.10.005.

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 30

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 1 2 3 4 5 6 10 sec 40 sec 500 sec 3000 sec

solute D concentration [10

  • 8 at.%]

depth [m]

slide-31
SLIDE 31

Triple damaging

  • Did we reach with 2.8 at. % the

maximum D concentration?

  • Triple damaging
  •  3.6 at. %

1 2 3 4 5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.2 0.4 0.6 0.8 multiple W damaging + D decoration

D atomic fraction (at. %) depth (m)

3

rd W-D

2

nd W-D

1

st W-D

damage (dpaKP)

SRIM Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 31

slide-32
SLIDE 32

Triple damaging

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 32

5000 10000 15000 2 4 6 8 multiple W damaging + D decoration

D Effusion Flux [10

17 D m

  • 2s
  • 1]

time [s]

3

rd W-D

2

nd W-D

1

st W-D

400 600 800 1000

temperature [K]

  • Did we reach with 2.8 at. % the

maximum D concentration?

  • Triple damaging
slide-33
SLIDE 33

Damage stabilization modelling

Damage stabilization model: ni(x, t): density of defect type i. W: flux of damaging W particles, ϴ(x): SRIM calculated primary damage profile 𝜃: probability of an impinging W particle to create a defect per unit length ρ: density of tungsten 𝑜𝑗

0: density of empty defects of type i

Free parameters of the model 𝑜𝑗,𝑛𝑏𝑦: saturation density of defect type i, 𝛽𝑗: stabilization parameter for defect type i. [M. Pečovnik et al. submitted to Nucl. Fusion]

𝑒𝑜𝑗(𝑦,𝑢) 𝑒𝑢

=

𝛥𝑋 𝜃 𝛴(𝑦) ρ

1 −

ni 𝑦,𝑢 ni,max 1 − 𝛽𝑗 ni 𝑦,𝑢 − 𝑜𝑗

0(𝑦,𝑢)

ni 𝑦,𝑢

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 33

ratio of D occupied defects of type i

slide-34
SLIDE 34

Damage stabilization modelling

Damage stabilization model:

  • defect type I: nmax = 0.21 at.%

fill level energies: 1.07 eV, 1.15 eV, 1.23 eV, 1.33 eV, 1.43 eV,

  • defect type II: nmax = 0.29 at.%

fill level energies: 1.66 eV, 1.84 eV,

  • defect type III: nmax = 0.04 at.%

fill level energy: 2.06 eV.

𝑒𝑜𝑗(𝑦,𝑢) 𝑒𝑢

=

𝛥𝑋 𝜃 𝛴(𝑦) ρ

1 −

ni 𝑦,𝑢 ni,max 1 − 𝛽𝑗 ni 𝑦,𝑢 − 𝑜𝑗

0(𝑦,𝑢)

ni 𝑦,𝑢

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 34

1 2 3 4 5 1 2 3 4 5

D atomic fraction (at. %) depth (m)

exp model 3

rd W-D

2

nd W-D

1

st W-D

slide-35
SLIDE 35

Damage stabilization modelling

𝑒𝑜𝑗(𝑦,𝑢) 𝑒𝑢

=

𝛥𝑋 𝜃 𝛴(𝑦) ρ

1 −

ni 𝑦,𝑢 ni,max 1 − 𝛽𝑗 ni 𝑦,𝑢 − 𝑜𝑗

0(𝑦,𝑢)

ni 𝑦,𝑢

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 35

400 500 600 700 800 900 1000 2 4 6 8 exp model 3

rd W-D

2

nd W-D

1

st W-D

D desorption flux [10

17 D/m 2s]

temperature [K]

Damage stabilization model:

  • defect type I: nmax = 0.21 at.%

fill level energies: 1.07 eV, 1.15 eV, 1.23 eV, 1.33 eV, 1.43 eV,

  • defect type II: nmax = 0.29 at.%

fill level energies: 1.66 eV, 1.84 eV,

  • defect type III: nmax = 0.04 at.%

fill level energy: 2.06 eV.

slide-36
SLIDE 36

Damage stabilization modelling

𝑒𝑜𝑗(𝑦,𝑢) 𝑒𝑢

=

𝛥𝑋𝜃 𝛴(𝑦) ρ

1 −

ni 𝑦,𝑢 ni,max 1 − 𝛽𝑗 ni 𝑦,𝑢 − 𝑜𝑗

0(𝑦,𝑢)

ni 𝑦,𝑢

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 36

Damage stabilization model:

  • defect type I: nmax = 0.21 at.%

fill level energies: 1.07 eV, 1.15 eV, 1.23 eV, 1.33 eV, 1.43 eV,

  • defect type II: nmax = 0.29 at.%

fill level energies: 1.66 eV, 1.84 eV,

  • defect type III: nmax = 0.04 at.%

fill level energy: 2.06 eV.

  • Fill levels: N1

fill = 5, N2 fill = 2 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 experiment model

maximum D fraction [at.%] number of damaging / decoration cycles

cmax = n1/(1 - 1) N

fill 1 + n2/(1 - 2) N fill 2 + n3 N fill 3

D-free W D presence

slide-37
SLIDE 37

Present interpretation

Different saturation/defect levels:

  • D free W: saturation in nDmax = 1.7 at.% above 0.2 dpa

because Frenkel pairs can annihilate with existing ones

  • D filled W: nDmax = 4.2 at.%

because newly created defects cannot annihilate with existing ones when they are occupied by D: stabilization

  • Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 37
slide-38
SLIDE 38

Summary

Influence of the presence of D on displacement damage

  • Multiple sequences of creating displacement damage and decorating defects

with D allows to study the influence of D on damage creation/stabilization (even at low temperatures) without the need for a dual beam in-situ setup

  • D retention exceeds the initial ‘saturation value’ by more than a factor of

two (at 290 K damaging) nD = 1.7 at.%  2.8 at.%  3.6 at.%  … 4.x at.%

  • No D is lost during consecutive W implantations / D is de-trapped but is

effectively re-trapped

  • D is redistributed from the low temperature de-trapping peak to the high

temperature de-trapping peak (during W irradiation or during TDS)

  • TDS shows no indication for new defect nature but only increased density
  • Rate equation modelling successful with increased defect density only
  • Damage stabilization model describes observation successfully

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 38

slide-39
SLIDE 39

Backup slides

Backup slides

slide-40
SLIDE 40

Related MD modelling

  • Simulating the cascade core by heating to 10000 K for 5 ps (using a

Langevin thermostat) to emulate the core region of a collision cascade with and without D present (work in progress)

  • Using descriptor based method [F. J. Domınguez-Gutierrez and U. von Toussaint,

submitted to J. Nucl. Mater] to identify defects created (IAEA challenge winner)

  • F. J. Domınguez-Gutierrez and U. von Toussaint

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 41

41 point defects 32 point defects PFMC 2019 D free 2% D

slide-41
SLIDE 41

Potential diagram

20 40 60 80 100 120

  • 4
  • 2

2 4 6 8

QSol

Energy (arb.)

Reaction coordinate

ED Surface Bulk Lattice sites (solute)

½ Ediss Ech

bcc lattice Tetrahedral sites in

Edes

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 42

slide-42
SLIDE 42

Potential diagram

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 43

Parameters for W ½ Ediss= 2.25 eV Ech=0.5 – 0.8 eV QSol=1.04 eV Two populations: DED = 0.39 eV (better 0.25 eV?) DEtrap ≈ 0.8 – 2 eV

20 40 60 80 100 120

  • 4
  • 2

2 4 6 8

ETrap

QSol

Energy (arb.)

Reaction coordinate

ED Surface Bulk Defect sites Lattice sites (solute)

½ Ediss Ech Edes

slide-43
SLIDE 43

Defect evolution during gentle loading

  • D retention in W foils after 192 h plasma exposure (fluence ≈ 4∙1025 D/m²)
  • S. Kapser et al., Nucl. Fusion, 2018 http://dx.doi.org/10.1088/1741-4326/aab571)

Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 44