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Transcript of DEUTERIUM RETENTION IN POLYCRYSTALLINE TUNGSTEN 2013-10-18¢  Deuterium Retention in...

  • DEUTERIUM RETENTION IN POLYCRYSTALLINE TUNGSTEN

    By

    Zhe Tian

    A thesis submitted in conformity with the requirements for the degree of

    Master of Applied Science

    Graduate Department of Aerospace Studies

    University of Toronto

    © Copyright by Zhe Tian (2009)

  • ii

    Deuterium Retention in Polycrystalline Tungsten Zhe Tian

    Master of Applied Science Graduate Department of Aerospace Studies

    University of Toronto 2009

    Abstract

    Deuterium retention in two types of polycrystalline tungsten was studied as a function

    of ion fluence, irradiation temperature and ion energy. Fluence dependence: D retention at

    300 K tends to saturate in both Rembar and Plansee PCW. At 500 K, D retention in the

    Plansee PCW increases with increasing ion fluence, similar to previous results for Rembar

    tungsten. Even at a fluence of 8×1025 D+/m2, no sign of saturation was observed.

    Temperature dependence: D retention in Plansee PCW decreases with increasing irradiation

    temperature (300 - 500 K). Energy dependence: varying the D+ energy from 100 to 500

    eV/D+ plays a minor role in D retention in W, suggesting that D retention depends more on

    the W structure, irradiation temperature and fluence, rather than on the ion energy when the

    energy is below the displacement threshold.

  • iii

    Acknowledgements

    I would like to gratefully thank my supervisors Prof. A.A. Haasz and Dr. J.W. Davis for

    giving me this opportunity to participate in a fresh research project. Prof. Haasz’s generosity,

    patience, and excellent guidance are very much appreciated. Dr. Davis’s encouragement and

    technical support for each particular problem during the research not only keeps me on the

    right track but inspires me in new ways of thinking. Special thanks to Dr. Makoto Oyaidzu

    for his valuable instructions in the beginning of my research, and to Mr. Charles Perez for his

    high quality and prompt work on preparing specimens and fabricating components for my

    experiments. The financial support provided by the Natural Science and Engineering

    Research Council (NSERC) of Canada is gratefully acknowledged.

    In my first two years’ life in Canada, I am pleased to have studied in such a

    multicultural environment and friendly atmosphere at UTIAS. So, big thanks to Fusion lab

    mates, Bernie Fitzpatrick, John Roszell, Cedric Tsui and Andre LeBelle, for their help,

    support and communications during the work time. Also thanks to ASA members, UTIAS

    soccer players, and everybody at the Institute to make the school life much more enjoyable.

    Special thanks go out to Dr. Alan Yu and Dr. Joseph Chen for their wisdom and substantial

    support in helping me accommodate to life in Toronto.

    Finally, I would express my gratitude to my family for their endless encouragement

    and love.

  • iv

    Table of Contents Abstract……………………………………………………………………… ii

    Acknowledgements………………………………………………………….. iii

    List of figures………………………………………………………………... vi

    List of tables…………………………………………………………………. viii

    1. Introduction……………………………………………............... 1

    1.1 Fusion energy…………………………………………………............. 1

    1.2 Plasma-facing materials……………………………………………… 2

    1.3 Tungsten……………………………………………………………….. 3

    1.4 Thesis objective……………………………………………………….... 4

    2. Background: deuterium retention in tungsten…..................... 4

    2.1 Irradiation effects on structure evolution of tungsten materials…… 5

    2.2 Fluence dependence of deuterium retention in tungsten………….… 7

    2.3 Temperature dependence of D retention in tungsten……………….. 10

    2.4 Flux dependence of deuterium retention in tungsten.......................... 10

    3. Experimental apparatus................................................................ 11

    3.1 Polycrystalline tungsten specimens…………………………………….. 11

    3.2 Ion beam implantation system………………………………………… 12

    3.2.1 Single-beam ion accelerator……………………………..………... 12

    3.2.2 Specimen holder………………………………………..………….. 13

    3.3 Thermal desorption system……………………………………………. 14

    3.4 Scanning electron microscopy (SEM)……………………………........ 15

    4. Experimental procedure………………………………………. 16

    4.1 Specimen preparation and anneal……………………………………. 16

  • v

    4.2 Deuterium ion implantation…………………………………………... 17

    4.3 Thermal desorption spectroscopy (TDS) …..…….. …………….…... 18

    4.4 TDS analysis………………………………………………………...…. 19

    5. Results and discussion…………………………………….…… 21

    5.1 Fluence dependence of D retention in PCW…………………………. 21

    5.1.1 D retention in Rembar PCW at 300 K……………………..……. 21

    5.1.2 D retention in Plansee PCW at 300 K……………..…………….. 23

    5.1.3 D retention in Plansee PCW at 500 K…………..……………….. 24

    5.1.4 Discussion of fluence dependence………………………………... 25

    5.2 Temperature dependence of D retention in PCW……....………….... 27

    5.3 Ion energy dependence of D retention in PCW…………..…..…....… 28

    6. Conclusions…………………………………….………………. 29

    6.1 Fluence dependence………………………………….…………...…… 29

    6.2 Temperature dependence……………………….…………………...... 30

    6.3 Ion energy dependence………………………….………………......… 30

    References………………………………………….…...……..… 32

    Figures……………………………………………………...…... 36

  • vi

    List of figures: Figure 2-1: Depth profiles of D trapped as D atoms (a) and D2 molecules (b) in single crystal

    and hot-rolled W implanted with 6 keV D ions at 300 K determined by the SIMS/RGA method.

    Figure 2-2: Retained vs. cumulative-fluence for 1 keV/D+ implantations at 500 K. Data are shown for specimens W2 (1023 D/m2 probe-fluence only), W1 (9×1023 D/m2 damage-fluence and probe-fluence), and W3 (1025 D/m2 damage-fluence and probe-fluence).

    Figure 2-3: Retained vs. cumulative-fluence for 500 eV/D+ implantations at 500 K. Data are shown for specimens W5 (1023 D/m2 probe-fluence only), W4 (9×1023 D/m2 damage-fluence and probe-fluence), W6 (3×1024 D/m2 damage-fluence and probe-fluence), W7 (1025 D/m2 damage-fluence and probe-fluence), and W9 (3×1025 D/m2 damage-fluence and probe-fluence).

    Figure 2-4: Fluence dependence of D retention in PCW at 300 K under various D ion energies

    Figure 2-5: NRA measurements of the near-surface D depth profiles. (a) 1 keV and 500 eV D+ (1024 D+/m2 incident fluence) implanted into W at 300 K. Implantation profiles for 1 keV and 500 eV D+ as calculated by TRVMC are shown for comparison (normalized to the peak height of the measured profiles). (b) 500 eV D+ implanted at 500 K into W (1024 D+/m2) and W-1% La2O3 (3.3×1024 D+/m2).

    Figure 2-6: Fluence dependence of D retention in W at elevated temperatures using ion beams.

    Figure 2-7: Fluence dependence of D retention in W at elevated temperatures using plasma devices and tokamaks.

    Figure 2-8: Temperature dependence of D retention in W and W-1%La2O3. (a) 1 keV/D+ at fluences of 1023 and 1024 D+/m2, (b) 500 eV D+ at fluence of 1023 D+/m2.

    Figure 2-9: Temperature dependence of D retention in M-SCW with an incident fluence of 1024 D+/m2.

    Figure 2-10 (a): Deuterium retention in single-crystal and polycrystalline fine-grain tungsten exposed to low-energy (200 eV/D+) and high flux (about 1×1021 D/m2s) D plasmas as a function of exposure temperature. For comparison, the temperature dependence of the D retention in polycrystalline coarse-grained W irradiated with 200 eV/D+ ions and flux of 4×1019 D m−2 s−1 to a fluence of 1×1024 Dm−2 is also shown. Note that the deuterium retention was calculated from deuterium depth profiles measured up to a depth of 7μm.

    Figure 2-10 (b): Deuterium retention in polycrystalline tungsten exposed to low-energy (98–100 eV/DT) and high flux ((8.7–10)×1021 D(T)m−2 s−1) D or (D+ T) plasmas as a function of exposure temperature.

    Figure 2-11: Deuterium retention as a function of incident D+ flux at three fluences (1021, 1022, and 1023 D+/m2) at room temperature.

    Figure 3-1: Schematic of single-beam ion accelerato