Influence of the presence of deuterium on displacement damage in tungsten T. Schwarz-Selinger 1 , J. Bauer 1 , S. Elgeti 1 M. Pe čovnik 2 , S. Markelj 2 1 2
Theoretical predictions - ‘ DFT molecular dynamics revealed that hydrogen clusters can prevent a vacancy from recombining with the neighboring crowdion-type self-interstitial- atom.’ D. K Kato o et al., Nuc ucl. Fus Fusion on 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 ’ 270 S.C. Midd ddlebur urgh gh, J. Nuc ucl. M Mater. 44 448 8 (2 (201 014) 4) 270 Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 2
Motivation In a future fusion reactor: In present day lab experiments: 14 MeV n 20 MeV W D plasma + D-T plasma D D D D D D D T D T T D bulk W mutual influence of D on damage creation/evolution? Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 3
Experimental strategy Shown before by Sabina: 10.8 MeV W sequentially or simultaneously + additional D decoration D D D D D Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 4
Experimental strategy Approach here: sequential treatment multiple times 20 MeV W D plasma 20 MeV W D plasma + + + … + D/W 1.7 at.% D/W 1.7 at.%? x at.% ? D D D D D D D D D D D D D D D D D D D D D D D D Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 5
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
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
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
D decoration: gentle plasma exposure PlaQ: known flux and energy - energy : „< 5 eV/D “ ( floating targets) - ion flux: 6 × 10 19 D/(m 2 s) (97% as D 3 + , 2% as D 2 + , 1% as D + ) - atom flux > 10 21 D 0 /(m 2 s) - ion fluence: up to 5·10 24 D/m 2 per day ’gentle’ loading = ‘decoration’: T = 370 K - no additional defect creation - no defect evolution/annealing) six samples simultaneously A. Manhard, Plasma Sources Sci. Technol. 20 20 (2011) 015010 Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 9
The tungsten substrate material confocal scanning laser microscopy • 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 × 10 12 m/m 3 [2] [1] A. Manhard et al., Pract. Metallogr. 50 (1) (2013) 6 – 15. [2] A. Manhard et al., Pract. Metallorg. 52 (2015) 437. Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 10
Creating displacement damage: W self-implantation 14 MeV fusion neutrons will cause • - transmutation - gas production - displacement damage (E pka < 200 keV) Here: only displacement damage aspect is studied with W self-implantation • Why tungsten ions? 20 MeV W in W target atoms + no chemical effects + dense cascades + fast: 1 dpa in 1 hour SRIM 2013 projectile - vacancies, vacancy clusters, ≈ µm voids, …. - too high E pka Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 11
Creating displacement damage: W self-implantation 2.3 μ m J. . Gr Grzonka onka et t al. l., , NI NIMB B Vol ol 340, 40, p. . 27 27 (201 2014) 4) 0.30 SRIM 2013 Calculated displacments (dpa KP ) 20 MeV W 0.25 7.8 10 17 W/m 2 with E dis = 90 eV* 0.20 STEM 0.15 micrograph 0.10 0.05 0.00 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Depth ( m) 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
Ł. ń D retention in self-damaged W 2.3 μ m calculated displacement damage (a.u.) 0 10 0.23 dpa 0 10 Previous investigation: D atomic fraction (at.%) 0.1 dpa -1 10 0.023 dpa fluence series 20 MeV W 6+ @ 290 K • SRIM -1 10 0.005 dpa D decoration with < 5 eV/D • -2 10 for 72 h (1.5 × 10 25 D/m 2 ) @ 450 K 0.001 dpa -2 10 D/W > 1 at.% @ 0.23 dpa • -3 10 0 dpa -3 10 detection limit 0 1 2 3 4 5 depth ( m) Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 13
Ł. ń D retention in self-damaged W 10 10 D decoration D atomic fraction (at. %) at 450 K Previous investigation: < 5 eV/D 17 ) Total D amount (10 1 1 fluence series 20 MeV W 6+ @ 290 K • • D decoration with < 5 eV/D TPD 0.1 0.1 for 72 h (1.5 × 10 25 D/m 2 ) @ 450K NRA @ 1.25 m D/W > 1 at.% @ 0.23 dpa • 0.01 0.01 linear increase for < 0.005 dpa • 5E-4 0.005 0.05 0.5 5 peak displacement damage (dpa NRT ) saturation in D for > 0.23 dpa • Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 14
Ł. ń D retention in self-damaged W 2 0.25 calculated displacement damage (dpa KP ) 25 D/m 2 ] D [10 2.25 Previous investigation: 0.20 D atomic fraction (at.%) 1.55 A0449, A0454, A0451, 0.23 dpa, PlaQ, floating, 450K 1.45 fluence series 20 MeV W 6+ @ 290 K • 0.40 0.15 0.10 1 • D decoration with < 5 eV/D 0.10 for 72 h (1.5 × 10 25 D/m 2 ) @ 450K 0.05 D/W > 1 at.% @ 0.23 dpa • 0 0.00 linear increase for < 0.005 dpa • 0 1 2 3 4 5 depth ( m) saturation in D for > 0.23 dpa • Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 15
Ł. ń D retention in self-damaged W 17 D) 2.0 integrated deuterium amount (10 1.5 Previous investigation: fluence series 20 MeV W 6+ @ 290 K • 1.0 • D decoration with < 5 eV/D for 72 h (1.5 × 10 25 D/m 2 ) @ 450K 0.5 D/W > 1 at.% @ 0.23 dpa • 0.0 0 1 2 linear increase for < 0.005 dpa • 25 D/m 2 ) deuterium fluence (10 saturation in D for > 0.23 dpa • Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 16
Saturating displacement damage with D st D decoration 1 0.4 D atomic fraction (at. %) ** 20MeV 0.23 dpa 2.0 nd D decoration + 2 0.3 1.5 * 1 times / 2 times PlaQ 72h, 370K, floating; This study: damage (dpa KP ) 0.2 SRIM 1.0 D decoration @ 370 K • 2 times 1.5·10 25 D/m 2 (2 x 72 h) • 0.5 0.1 check if damaged zone • is completely filled with D 0.0 0.0 0 1 2 3 4 5 Depth ( m) 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
Ł. ń D retention in self-damaged W beam sweep for laterally • homogenous damage accuracy, reproducibility: • normalized proton integral (a.u.) normalized proton integral (a.u.) 1.2 1.2 better than 5% 1.0 1.0 box like D reservoir D145 0.8 0.8 0 5 10 0 5 10 15 short axis (mm) long axis (mm) Thomas Schwarz-Selinger et al. | mod-pmi 2019 | NIFS | June 20, 2019 | Page 18
Until IBIS isn’t ready: ‘simultaneous for the poor’ ● ‘Recrystallized W’ – μ ● ≙ ● ≙ ● Displacements during 20 MeV W 1.2 1.2 SDTrimSP calculation: 20 MeV W on W, containing 2 % D • 1.0 fraction of detrapped D 1.0 fraction of displaced W = 7.87 × 10 17 W 6+ /m 2 • 0.8 0.8 displacement energy • 0.6 0.6 - E displ. W = 90 eV, E cutoff, W = 2.2 eV - E displ, D = 1 eV, E cutoff, D = 0.25 eV 0.4 0.4 0.2 0.2 tungsten atoms are displaced and defects are generated (0.23 dpa) 0.0 0.0 0.0 0.5 1.0 1.5 2.0 2.5 simultaneously, retained deuterium depth [ m] 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
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