Displacement damage stabilization byhydrogen presence under simultaneous W
ion damaging and D ion exposure
S. Markelj1, T. Schwarz-Selinger2, M. Pečovnik1, M. Kelemen1,31Jožef Stefan Institute, Ljubljana, Slovenia
2 Max-Planck-Institut für Plasmaphysik (IPP), Garching, GermanycJožef Stefan International Postgraduate School, Jamova cesta 39, 1000 Ljubljana, Slovenia

WP PFCThis work has been carried out within the framework of the EUROfusion
Consortium and has received funding from the Euratom research andtraining programme 2014-2018 and 2019-2020 under grant agreement
No 633053. The views and opinions expressed herein do notnecessarily reflect those of the European Commission.

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Tungsten –plasma facing material
Fusion device scenario
D/T plasma exposure + neutron irradiation
D,Tn - 14 MeV

S. Markelj et al. | MoD PMI 2019, Japan | Page 2

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Tungsten –plasma facing materialD,Tn - 14 MeV

Neutron bombardment= Displacement damage
creation
Vacancy

Vacancy cluster

Damagecreation at RT+
damageannealing

Dislocation

Self-Interstitials
Interstitials

Damagecreation atelevatedtemperatures

S. Markelj et al. | MoD PMI 2019, Japan | Page 3

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Tungsten –plasma facing material
D,TFuel implantation• ions and neutrals - energy few
eV – keV;• High fluxes up to 1024 m-2s-1

n - 14 MeV

Neutron bombardment= Displacement damage
creation
Vacancy

Implantation
Reflection

Adsorption

Dislocation

Recombination

Desorption

Trapping
Vacancy cluster
Diffusion

Hydrogen

Fuel transport:
diffusion
trapping
de-trapping

Metal atom

Fuelretention

Damagecreation at RT+damage
annealingSelf-Interstitials
Interstitials

Damagecreation atelevated
temperatures

S. Markelj et al. | MoD PMI 2019, Japan | Page 4

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Tungsten –plasma facing material
Neutron bombardment= Displacement damage
creation

Fuel implantation• ions and neutrals - energy few
eV – keV;• High fluxes up to 1024 m-2s-1
Vacancy
Implantation
Reflection

Adsorption

Dislocation

Recombination

Desorption

Trapping
Vacancy cluster
Diffusion

Fuel transport:
diffusion
trapping
de-trapping

Hydrogen

Fuelretention

Metal atom

Damagecreation at RT+damage
annealingSelf-Interstitials
Interstitials

Damagecreation atelevated
temperatures

S. Markelj et al. | MoD PMI 2019, Japan | Page 5

WP PFCOutline
 Different displacement damaging procedures
 Comparison between:Sequential W ion irradiation and D exposureSimultaneous W ion irradiation and D exposure Comparison atoms versus ions
 Conclusions

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14 MeV neutron irradiation
Displacement damage creation

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Influence of neutron irradiation on D retention
activation of samples, long irradiation time,
14 MeV neutrons not available (fission neutrons)!

20 µm

20 µm

W self-damaging
20 MeV W in W
1 µm
SRIM calculation of ion trajectoryHigh energy ion damaging
MeV W ion irradiation = Surrogate for neutronirradiation• Dense cascades and no chemical effect• No transmutation
Ion damaging

Few µmneutron damaging

Few cm
S. Markelj et al. | MoD PMI 2019, Japan | Page 7

Displacement damage creation
MeV W ion irradiation
W self-damaging

W ion irradiation by MeV W ions
• Creation of displacement damage

7.9x1017 W/m2

0.23 dpaKP

Recrystallized W

W6+ 20 MeV

W ions 20 MeVWP PFCbulk W

Damaged layer characterization byScanning Transmission
Electron Microscopy [Zaloznik et al.
Phys Scr. T167 (2016) 014031 ]S. Markelj et al. | MoD PMI 2019, Japan | Page 8

Displacement damage creation
MeV W ion irradiation

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W ion irradiation by MeV W ions
• Creation of displacement damage• Increased fuel retention in ion damaged W
material from ~ 10-3 at. % ↗ ~ 1 at. %•et al. NF 2012, Schwarz-Selinger FEC 2018]DD

10.8/20 MeV W irradiatedDW

D atom exposure @ 600 K

D D DDD
D DDD saturation observed at damage dose > 0.2dpa
for RT W irradiation! [Alimov et al. JNM 2013, Hoen

bulk W
S. Markelj et al. | MoD PMI 2019, Japan | Page 9

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Simultaneous W/D exposure
W ionsD ions/atoms

Simultaneous W/D exposure:
W ion irradiation @ different highD exposure
temperatures≈ 2µm
recrystallized

bulk W

S. Markelj et al. | MoD PMI 2019, Japan | Page 10

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Simultaneous W/D-D exposure
D ions/atoms

Simultaneous W/D-D exposure:
W ion irradiation @ different highD exposure
temperatures
D exposure@ low≈ 2µm

recrystallized

bulk W

temperature topopulate createdtraps

 D retention a way to determine
defect concentration

S. Markelj et al. | MoD PMI 2019, Japan | Page 11

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Sequential W-D exposure
W ionsD ionsSequential W-D exposure:
W ion irradiation @ different hightemperatures≈ 1.2 µm
recrystallized

bulk W

D exposure@ low temperature
to populate createdtraps

 D retention a way to determine
defect concentration

S. Markelj et al. | MoD PMI 2019, Japan | Page 12

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Experiment with atoms – 0.28 eV/D

Simultaneous/sequential W/D, W-D atom loading
Defect population - exposure D atoms @ 600 K – fluence 3.7 ×1023 D/m22 Collimator slits
In-beam meshchargecollector

4 mm
A

W6+ E=10.8 MeV
Sample at hightemperatures ≤ 1000K
Heater
Simultaneous/sequential W irradiation
and D atom exposure at hightemperatures for 4 h
Atom flux=5.4x1018 D/m2s
ΓD=8x1022 D/m2

Analysis methods:
 Deuterium depth profile
measurement by Nuclear
Reaction Analysis (NRA)TDS – final step – D
desorption kinetics and DamountW fluence = 1.4x1018 W/m2
Dose→ 0.47 dpaKP
Displ. Rate = 3*10-5 dpa/s
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Effect of D presence – atom exposure
Comparison of D concentration

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Neutron damaging simulated by self implantation
Simultaneous W ion damaging and D atom loading

Comparison to different damaging procedures
 Sequential: Damage at TEXP; D
population at 600 K

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Effect of D presence – atom exposure
Comparison of D concentration

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Neutron damaging simulated by self implantation
Simultaneous W ion damaging and D atom loading

Comparison to different damaging procedures
 Sequential: Damage at TEXP; D
population at 600 K
 Simultaneous: Damage & D
exposure at TEXP; D population at600 K
 Observed synergistic effects but not
dramatic – 30 % increase Competition between defectannihilation at elevated temp. anddefect stabilization by D
For more details see:
• S. Markelj, et al, Nuclear Materials and Energy 12(2017) 169.
• E. Hodille et al. Nucl. Fusion 59 (2019) 016011
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Experiment with ions– 300 eV/D

Simultaneous/sequential W/D, W-D ion loading
Defect population - exposure D ions @ 450 K – fluence 2.7×1023 D/m2

Analysis methods:
 Deuterium depth profile
measurement by Nuclear
Reaction Analysis (NRA)

Ion energy 300 eV/D
Ion flux=1.3x1018 D/m2s
ΓD=1.9x1022 D/m2

W fluence = 1.0x1018 W/m2
Dose→ 0.35 dpaKP
Displ. Rate = 2.4*10-5 dpa/s

TDS – final step – D
desorption kinetics and Damount•S. Markelj et al, Nucl. Fusion(2019) in press
M. Pecovnik et al. submitted toNucl. Fusion•S. Markelj et al. | MoD PMI 2019, Japan | Page 16

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TDS - Sequential experiment
W ion damaging at
300 K – sequential
D atom exposure at
600K

Sequential W-D; W damaging @ 300 K

 Single peak
 Two de-trapping
energies 1.82 eV and2.06 eV

D ion exposure at450K
 Double peak Five de-trapping
energies 1.35 eV - 2.09eV
 3x higher D amountRate equation modelling(MHIMS, Hodille et al.
JNM 2017)
S. Markelj et al. | MoD PMI 2019, Japan | Page 17

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Simultaneous W/D exposure
W ionsD ionsSimultaneous W/D exposure:
W ion irradiation @ 450 K
D ion exposure≈ 2µm
recrystallized

bulk W4h simultaneous W/D
W ions – flux 𝟗. 𝟕𝟑 × 𝟏𝟎𝟏𝟑 W/m2s – 0.34 dpa
D ions - Ion flux=1.4x1018 D/m2s
ΓD=2.0x1022 D/m2

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Simultaneous W/D exposure @ 450 K
D depth profile

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Simultaneous W/D-D exposure @ 450 K
D ionsSimultaneous W/D-D exposure:
W ion irradiation @ 450 K
D ion exposure+D ion exposure @ 450 K – to≈ 2µm
recrystallized

bulk W

populate createdtraps

4h simultaneous W/D
W ions – flux 𝟗. 𝟕𝟑 × 𝟏𝟎𝟏𝟑 W/m2s – 0.34 dpa
D ions - Ion flux=1.4x1018 D/m2s.
D fluence=2.0x1022 D/m2+
41h D ion exposure - D fluence 2.1×1023 D/m2

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Simultaneous W/D-D exposure @ 450 K
D depth profile

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Sequential W-D exposure
W ionsD ions/atoms

Sequential W-D exposure:
W ion irradiation @ 450 K+≈ 1.2 µm

recrystallized

bulk W

D ion exposure@ 450 K to populate
created traps

4h W irradiation
W ions – flux 𝟗. 𝟕𝟑 × 𝟏𝟎𝟏𝟑 W/m2s – 0.34 dpa+
39 h D ion exposure - D fluence 2.0×1023 D/m2

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D depth profile comparison @ 450 K

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D depth profile comparison @ 450 K
 Difference in Dconcentration in theregion where D wastrapped during the
1. step – simultaneous
W/D Factor of 2 difference

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D depth profile comparison @ 450 K
 Difference in Dconcentration in theregion where D wastrapped during the 1.
step – simultaneous
W/D Factor of 2 difference Comparison to oldermeasurement – D
depth profile similar
with stepped
distribution

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Comparison TDS sequential / simultaneous Defect population by
300eV/D ion exposure at450K
 No drastic change in TDS
peak shape - double peak forboth cases Temperature dependence
also for individual traps

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D depth profile comparison – all temperatures

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Sequential W-D exposure Sequential W-D exposure

300 eV/D ion exposure at 450K

 D concentration decreases
with irradiation temperature
 Less defects created atelevated temperatures

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Comparison to Simultaneous W/D-D exposure Sequential W-D exposure

300 eV/D ion exposure at 450K

 Simultaneous W/D-Dexposure Increase of D concentration– larger defect concentration
 Strong temperaturedependence:
 450 K – 2.1
 600 K – 1.7
 800 K – 1.1
 1000 K – 2.1

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Simultaneous W/D exposure
D depth profiles – all temperatures

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Simultaneous W/Dexposure: Depth profiles after first4h
 Temperature
determines the speed ofdiffusion and populationof traps by D Lower D retention athigh temperatures dueto thermal D detrapping
Defect stabilization
dependent on the Dconcentration during thesimultaneous W/DS. Markelj et al. | MoD PMI 2019, Japan | Page 30

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Comparison ions versus atoms

 D concentration during W/D
exposure determines theefficiency of defectstabilization by D presence
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Effect of presence of D
Ab-initio calculations

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Fusion device scenario neutron irradiation during D/T plasma exposure
Two possible effects
Density Functional Theory (DFT) calculation
with hydrogen in interstitial tetrahedral sitein W [S.C. Middleburgh et al. , JNM 448 (2014) 270–275]:• 25% lower than the vacancy formationenergy in W without H.

 Higher probability of defectcreation due to presence of H
DFT calculation with hydrogen cluster in avacancy in W [D. Kato et al. , NF 55 (2015) 083019]:• Hydrogen cluster prevents vacancy
from recombining with adjacent selfinterstitial atoms (1 1 1-crowdion) Lower probability for defectannihilation due to trapped D
S. Markelj et al. | MoD PMI 2019, Japan | Page 32

Stabilization by D trapping

WP PFCWe have upgraded the damage creation model, first introduced by Duesing et al. 1969,
Ogorodnikov JAP 2008, Hodille NF 2018 - by including a stabilization mechanism:𝑑𝑛𝑖 (𝑥, 𝑡) 𝛤 𝜂𝑖 𝛳(𝑥)ni 𝑥, 𝑡=1−𝑑𝑡ρni,max

ni 𝑥, 𝑡 − 𝑛𝑖0 (𝑥, 𝑡)
1 − 𝛼𝑖ni 𝑥, 𝑡Defects are stabilized to a degree by D trapped in them, meaning that the probability for aFrenkel pair annihilation is lower. Stabilization is parametrized by a free parameter denoted
as 𝛼𝑖 .
𝛤 ... W ion flux (W m-2s-1)
𝜂 ... Creation probability (m-1)
𝛳(𝑥) ... SRIM dam. distribution (1)ni,max ... Saturation density (1 (at. fr.))

M. Pečovnik et al. under review in Nucl. Fusion
S. Markelj et al. | MoD PMI 2019, Japan | Page 33

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Experiment versus modelling
TDS

VACANCIES – 2 fill levels
S. VACANCY CLUSTERS – 2 fill levels
L. VACANCY CLUSTERS – 1 fill level

D depth profiles

Stabilization by trapped D

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Conclusions
Study of D presence on displacement damage stabilization
Sequential W-D experiment Decreased D retention with higher temperature

Simultaneous W/D-D experiment Effect of stabilization of defects increased for ion exposure as compared toatoms
 Observed temperature dependence of defect stabilization
 Concentration of created traps dependent on D concentration during thesimultaneous W/D Increase of D concentration at 1000 K unclear

 Fusion scenario: higher fluxes of hydrogen fuel – higher D concentration athigh temperatures – larger effect
References - ions
• S. Markelj, et al, Nucl. Fusion (2019) in press• M. Pečovnik et al. under review Nucl. Fusion

References atoms:• S. Markelj, et al, Nuclear Materials andEnergy 12 (2017) 169.
• E. Hodille et al. Nucl. Fusion 59 (2019)016011
S. Markelj et al. | MoD PMI 2019, Japan | Page 35

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D mobile concentration comparison

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