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Displacement damage stabilization by hydrogen presence under simultaneous W ion damaging and D ion exposure S. Markelj 1 , T. Schwarz-Selinger 2 , M. Pe ovnik 1 , M. Kelemen 1,3 1 Jo ef Stefan Institute, Ljubljana, Slovenia 2

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This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

Displacement damage stabilization by hydrogen presence under simultaneous W ion damaging and D ion exposure

  • S. Markelj1, T. Schwarz-Selinger2, M. Pečovnik1, M. Kelemen1,3

1Jožef Stefan Institute, Ljubljana, Slovenia 2 Max-Planck-Institut für Plasmaphysik (IPP), Garching, Germany cJožef Stefan International Postgraduate School, Jamova cesta 39, 1000 Ljubljana, Slovenia

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

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n - 14 MeV D,T

Fusion device scenario D/T plasma exposure + neutron irradiation

Tungsten –plasma facing material

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

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Vacancy Dislocation Self-Interstitials Interstitials Vacancy cluster

Tungsten –plasma facing material

Neutron bombardment = Displacement damage creation Damage creation at RT + damage annealing Damage creation at elevated temperatures n - 14 MeV D,T

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

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Vacancy Dislocation Self-Interstitials Interstitials Vacancy cluster Recombination Implantation Hydrogen Metal atom Reflection Diffusion Trapping Adsorption

Desorption

Tungsten –plasma facing material

Neutron bombardment = Displacement damage creation Damage creation at RT + damage annealing Damage creation at elevated temperatures Fuel transport: diffusion trapping de-trapping Fuel retention n - 14 MeV D,T Fuel implantation

  • ions and neutrals - energy few

eV – keV;

  • High fluxes up to 1024 m-2s-1
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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 5

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Vacancy Dislocation Self-Interstitials Interstitials Vacancy cluster Recombination Implantation Hydrogen Metal atom Reflection Diffusion Trapping Adsorption

Desorption

Tungsten –plasma facing material

Neutron bombardment = Displacement damage creation Damage creation at RT + damage annealing Damage creation at elevated temperatures Fuel implantation

  • ions and neutrals - energy few

eV – keV;

  • High fluxes up to 1024 m-2s-1

Fuel transport: diffusion trapping de-trapping Fuel retention

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 6

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  • 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

Outline

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

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

  • Dense cascades and no chemical effect
  • No transmutation

20 MeV W in W

1 µm

14 MeV neutron irradiation Displacement damage creation

SRIM calculation of ion trajectory

W self-damaging

High energy ion damaging

20 µm 20 µm

Few µm Ion damaging neutron damaging Few cm

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 8

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W self-damaging

0.23 dpaKP bulk W Recrystallized W

Damaged layer characterization by Scanning Transmission Electron Microscopy [Zaloznik et al.

Phys Scr. T167 (2016) 014031 ]

W6+ 20 MeV W ion irradiation by MeV W ions

  • Creation of displacement damage

Displacement damage creation MeV W ion irradiation

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

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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. %

  • D saturation observed at damage dose > 0.2dpa

for RT W irradiation! [Alimov et al. JNM 2013, Hoen

et al. NF 2012, Schwarz-Selinger FEC 2018]

10.8/20 MeV W irradiated D atom exposure @ 600 K bulk W W D D D D D D D D D D D

Displacement damage creation MeV W ion irradiation

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

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bulk W recrystallized ≈ 2µm D ions/atoms

Simultaneous W/D exposure

W ions

Simultaneous W/D exposure: W ion irradiation D exposure

@ different high temperatures

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

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bulk W recrystallized ≈ 2µm D ions/atoms

Simultaneous W/D-D exposure: W ion irradiation D exposure

  • D exposure

@ different high temperatures @ low temperature to populate created traps

Simultaneous W/D-D exposure

 D retention a way to determine defect concentration

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

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bulk W recrystallized ≈ 1.2 µm D ions

Sequential W-D exposure

W ions

Sequential W-D exposure: W ion irradiation

  • D exposure

@ different high temperatures @ low temperature to populate created traps

 D retention a way to determine defect concentration

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 13

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  • Simultaneous/sequential W/D, W-D atom loading
  • Defect population - exposure D atoms @ 600 K – fluence 3.7 ×1023 D/m2

Heater

Sample at high temperatures ≤ 1000K

W6+ E=10.8 MeV

A

4 mm

In-beam mesh charge collector 2 Collimator slits

Simultaneous/sequential W irradiation and D atom exposure at high temperatures for 4 h Atom flux=5.4x1018 D/m2s ΓD=8x1022 D/m2 W fluence = 1.4x1018 W/m2 Dose→ 0.47 dpaKP

  • Displ. Rate = 3*10-5 dpa/s

Experiment with atoms – 0.28 eV/D

Analysis methods:

  • Deuterium depth profile

measurement by Nuclear Reaction Analysis (NRA)

  • TDS – final step – D

desorption kinetics and D amount

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 14

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

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

Effect of D presence – atom exposure Comparison of D concentration

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 15

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

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

 Observed synergistic effects but not dramatic – 30 % increase

 Competition between defect annihilation at elevated temp. and defect stabilization by D

Effect of D presence – atom exposure Comparison of D concentration

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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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 16

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

Experiment with ions– 300 eV/D

Analysis methods:

  • Deuterium depth profile

measurement by Nuclear Reaction Analysis (NRA)

  • TDS – final step – D

desorption kinetics and D amount

  • S. Markelj et al, Nucl. Fusion

(2019) in press

  • M. Pecovnik et al. submitted to
  • Nucl. Fusion
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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 17

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TDS - Sequential experiment

W ion damaging at 300 K – sequential D atom exposure at 600K

 Single peak  Two de-trapping energies 1.82 eV and 2.06 eV

D ion exposure at 450K

 Double peak  Five de-trapping energies 1.35 eV - 2.09 eV  3x higher D amount Rate equation modelling (MHIMS, Hodille et al. JNM 2017) Sequential W-D; W damaging @ 300 K

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 18

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bulk W recrystallized ≈ 2µm D ions

Simultaneous W/D exposure

W ions

Simultaneous W/D exposure: W ion irradiation D ion exposure

@ 450 K 4h simultaneous W/D W ions – flux 𝟘. 𝟖𝟒 × 𝟐𝟏𝟐𝟒 W/m2s – 0.34 dpa D ions - Ion flux=1.4x1018 D/m2s ΓD=2.0x1022 D/m2

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 19

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Simultaneous W/D exposure @ 450 K D depth profile

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 20

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bulk W recrystallized ≈ 2µm D ions

Simultaneous W/D-D exposure: W ion irradiation D ion exposure + D ion exposure

@ 450 K @ 450 K – to populate created traps

Simultaneous W/D-D exposure @ 450 K

4h simultaneous W/D W ions – flux 𝟘. 𝟖𝟒 × 𝟐𝟏𝟐𝟒 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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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 21

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

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 22

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bulk W recrystallized ≈ 1.2 µm D ions/atoms

Sequential W-D exposure

W ions

Sequential W-D exposure: W ion irradiation + D ion exposure

@ 450 K @ 450 K to populate created traps 4h W irradiation W ions – flux 𝟘. 𝟖𝟒 × 𝟐𝟏𝟐𝟒 W/m2s – 0.34 dpa + 39 h D ion exposure - D fluence 2.0×1023 D/m2

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 23

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D depth profile comparison @ 450 K

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 24

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D depth profile comparison @ 450 K

  • Difference in D

concentration in the region where D was trapped during the

  • 1. step – simultaneous

W/D

  • Factor of 2 difference
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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 25

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D depth profile comparison @ 450 K

  • Difference in D

concentration in the region where D was trapped during the 1. step – simultaneous W/D

  • Factor of 2 difference
  • Comparison to older

measurement – D depth profile similar with stepped distribution

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 26

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  • Defect population by

300eV/D ion exposure at 450K  No drastic change in TDS peak shape - double peak for both cases  Temperature dependence also for individual traps

Comparison TDS sequential / simultaneous

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 27

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D depth profile comparison – all temperatures

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 28

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  • Sequential W-D exposure

 D concentration decreases with irradiation temperature  Less defects created at elevated temperatures

Sequential W-D exposure

300 eV/D ion exposure at 450K

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 29

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  • Sequential W-D exposure
  • Simultaneous W/D-D

exposure

  • Increase of D concentration

– larger defect concentration

  • Strong temperature

dependence:

  • 450 K – 2.1
  • 600 K – 1.7
  • 800 K – 1.1
  • 1000 K – 2.1

Comparison to Simultaneous W/D-D exposure

300 eV/D ion exposure at 450K

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 30

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Simultaneous W/D exposure:  Depth profiles after first 4h

  • Temperature

determines the speed of diffusion and population

  • f traps by D
  • Lower D retention at

high temperatures due to thermal D de- trapping

Simultaneous W/D exposure D depth profiles – all temperatures

Defect stabilization dependent on the D concentration during the simultaneous W/D

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 31

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Comparison ions versus atoms

  • D concentration during W/D

exposure determines the efficiency of defect stabilization by D presence

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 32

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Fusion device scenario neutron irradiation during D/T plasma exposure

Effect of presence of D Ab-initio calculations

Density Functional Theory (DFT) calculation with hydrogen in interstitial tetrahedral site in W [S.C. Middleburgh et al. , JNM 448 (2014) 270–

275]:

  • 25% lower than the vacancy formation

energy in W without H.

  • Higher probability of defect

creation due to presence of H

Two possible effects DFT calculation with hydrogen cluster in a vacancy in W [D. Kato et al. , NF 55 (2015) 083019]:

  • Hydrogen cluster prevents vacancy

from recombining with adjacent self- interstitial atoms (1 1 1-crowdion)

  • Lower probability for defect

annihilation due to trapped D

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 33

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Stabilization by D trapping

We have upgraded the damage creation model, first introduced by Duesing et al. 1969, Ogorodnikov JAP 2008, Hodille NF 2018 - by including a stabilization mechanism: 𝑒𝑜𝑗(𝑦, 𝑢) 𝑒𝑢 = 𝛥 𝜃𝑗 𝛴(𝑦) ρ 1 − ni 𝑦, 𝑢 ni,max 1 − 𝛽𝑗 ni 𝑦, 𝑢 − 𝑜𝑗

0(𝑦, 𝑢)

ni 𝑦, 𝑢 Defects are stabilized to a degree by D trapped in them, meaning that the probability for a Frenkel pair annihilation is lower. Stabilization is parametrized by a free parameter denoted as 𝛽𝑗.

𝛥 ... W ion flux (W m-2s-1) 𝜃 ... Creation probability (m-1) 𝛴(𝑦) ... SRIM dam. distribution (1) ni,max ... Saturation density (1 (at. fr.))

  • M. Pečovnik et al. under review in Nucl. Fusion
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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 34

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Stabilization by trapped D VACANCIES – 2 fill levels

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

Experiment versus modelling

TDS D depth profiles

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 35

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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 to

atoms

  • Observed temperature dependence of defect stabilization
  • Concentration of created traps dependent on D concentration during the

simultaneous W/D

  • Increase of D concentration at 1000 K unclear
  • Fusion scenario: higher fluxes of hydrogen fuel – higher D concentration at

high 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 and

Energy 12 (2017) 169.

  • E. Hodille et al. Nucl. Fusion 59 (2019)

016011

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  • S. Markelj et al. | MoD PMI 2019, Japan | Page 44

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D mobile concentration comparison