Sachiko Suzuki 1, Akira Yoshikawa 1, Hirotada Ishikawa 1, Yohei Kikuchi 1, Yuji Inagaki 1, Naoko Ashikawa 2, Akio Sagara 2, Naoaki Yoshida 3, Yasuhisa Oya 1 and Kenji Okuno 1 1 Radioscience Research Laboratory, Faculty of Science, Shizuoka University, Japan 2 National Institute for Fusion Science, Japan 3 Institute of Applied Mechanics, Kyushu University, Japan Hydrogen isotope behavior in C + and D 2 + simultaneous implanted tungsten

Combination usage of tungsten (W) and carbon fiber composite (CFC) Sputtering by direct contact of plasma Forming of re-deposition layer (W x C y ) Elucidation of chemical behavior of hydrogen isotopes implanted into C/W mixed materials Background

Fig. 1 D 2 TDS spectrum in WC Previous study [1] 400 K Peak 1 at 400 K 490 K Peak 2 at 490 K 600 K Peak 3 at 600 K Carbon vacancy 930 K Peak 4 at 930 K C-D bond Trapping sites of deuterium Interstitial sites [1] H. Kimura, et al., Fusion Eng. Des. 81 (2006) Objective Elucidation of h ydrogen isotope behavior in C + and D 2 + simultaneous implanted tungsten Elucidation of h ydrogen isotope behavior in C + and D 2 + simultaneous implanted tungsten

D 2 + gun Ion implantation chamber Sample insert port Fig. 2 The simultaneous C + and D 2 + implantation system C + gun Apparatus TDS chamber Ion source gas: CO 2 E×B mass separation filter Fig. 3 SRIM calculation results for implantation depth Energy: keV C + Flux: 2.0× ×10 18 C + m -2 s -1 Energy: keV D 2 + Flux: 2.0×10 17 – 2.0×10 18 D 2 + m -2 s -1

Samples W ( under stress-relieved conditions ) purchased from A.L.M.T. Corp. Density: 19.3 g/cm 3 Size: 10 mm Ф  0.5 mm Prepared and polished

Implantation conditions Energy: 3.0 keV D 2 +, 10 keV C + Flux: 1.0 × ions m -2 s -1 Fluence: 1.0 × ions m -2 Imp. temp.: R.T. Heating rate: 0.5 K s -1 Heating temp.: R.T. – 1173 K C +, D 2 + implantations TDS XPS X-ray source: Al K  Implantation procedures Only D 2 + imp. C + and D 2 + simultaneous imp. D 2 + imp. after C + imp. XPS Experimental procedure 1 Heating temp.: 1173 K Time: 10 min Preheating

C + imp. D 2 + imp. and C + imp. D 2 + imp. Implantation procedures Only D 2 + imp.C + and D 2 + simultaneous imp. C + and D 2 + sequential imp. D 2 + imp. D 2 + gun C + gun

Implantation conditions Energy: 3.0 keV D 2 +, 10 keV C + Flux: 1.0 × ions m -2 s -1 Fluence: 1.0 × ions m -2 Imp. temp.: R.T. Heating rate: 0.5 K s -1 Heating temp.: R.T. – 1173 K C +, D 2 + implantations TDS XPS X-ray source: Al K  Implantation procedures Only D 2 + imp. C + and D 2 + simultaneous imp. D 2 + imp. after C + imp. XPS Experimental procedure 1 Heating temp.: 1173 K Time: 10 min Preheating

Implantation conditions Energy: 3.0 keV D 2 +, 10 keV C + Flux: 1.0 × D 2 + m -2 s -1 Flux: 2.0 × × C + m -2 s Flux ratio of C + /D + : Fluence: 1.0 × D 2 + m -2 Fluence: 2.0 × × C + m -2 Imp. temp.: R.T. Heating rate: 0.5 K s -1 Heating temp.: R.T. – 1173 K C +, D 2 + implantations TDS XPS X-ray source: Al K  XPS Experimental procedure 2 Heating temp.: 1173 K Time: 10 min Preheating C + and D 2 + simultaneous imp. Implantation procedures The flux dependence of C +

Results and Discussion (1) Fig. 4 XPS spectra of C-1s with various implantation procedures C-W bond ・・・ eV [1] C-C bond ・・・ eV [2] [1] H. Kimura, et al., Fus. Eng. Des. 81 (2006) [2] C. D. Wagner, et al. Handbook of X-ray photoelectron spectroscopy, Rerking- Elmer Corp., Physical Electronics, Division. Fig. 5 Peak areas of C-C and C-W bonds with various implantation procedures The decrease of C-C bond by D 2 + imp. on C + -D 2 + sequential imp. The sputtering of carbon by D 2 + imp. The area of C-C bond Simultaneous imp. ＞ Sequential imp. Aggregation of carbon on surface after C + -D 2 + simultaneous imp. C-W bond C-C bond

Fig. 6 XPS spectra of W-4f with various implantation procedures [3] J. Kovac, et al., Vacuum 82 (2008) C + -D 2 + simultaneous imp. ・・・ The positive peak shift of about 0.4 eV Only C + imp. ・・・ The positive peak shift of about 0.9 eV C + -D 2 + simultaneous implantation→C-W bond Only C + implantation → carbon rich tungsten carbide (WC x ) Main chemical states Results and Discussion (2) W ： 31.5 eV [3]

800KC-D bond The higher desorption peak at around 800K ・・・ C-D bond The least total deuterium retention in Simultaneous imp. [4] T. Suda, et al., Fus. Eng. Des. 82 (2007) In C + -D 2 + simultaneous implantation deuterium was hardly trapped at higher temperature. Results and Discussion (3) Fig. 7 TDS spectra with various implantation procedures Fig. 8 Total D retention with various implantation procedures K 400 K 400 K Interstitial of W The large desorption peak at around 400 K → Interstitial of W

Results and Discussion (4) The flux dependence of C + Fig. 9 TDS spectra for the simultaneous implanted W with various C + /D + flux ratio Fig. 10 Total peak area of C-1s as a function of C + /D + flux ratio 800 K C-D bond C + /D + ＝ 0.2 : The large desorption peak at around 800 K → C-D bond Carbon concentration was decreased as the C + /D + ratio increased The enhancement of carbon re-emission in high C + /D + ratio The low re-emission of carbon leads high retention of D trapped by carbon.

Summary Elucidation of the trapping sites and role of carbon on hydrogen isotope retention in C/W mixed materials  D desorption at higher temperature side in C + -D 2 + sequential imp. →C-D bond  Total D retention Only D 2 + imp. C + -D 2 + sequential imp. Further studies Establishment of the simultaneous C + and D 2 + implantation system ＜ About 25% C + -D 2 + simultaneous imp. Elucidation of hydrogen isotope behavior in C + and D 2 + simultaneous implanted tungsten The flux dependence of C + The low reemission of carbon leads high retention of D trapped by carbon.

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284.6 eV C-C + C-D31.4 eV W-C Fig. 11 C-1s and W-4f XPS spectra after D 2 + implantation at various implantation temperatures eV C-W Interstitial site IInterstitial site II W D C Dependence of implantation temperature on change of chemical state of C and W in WC Peak 1 Peak 1: Interstitial site I Peak 2 Peak 2: Interstitial site II

Analysis methods TDS (Thermal Desorption Spectroscopy) XPS (X-ray Photoelectron Spectroscopy) D 2 + implantation QMS Heating Analyzer X-ray XPSTDS

Fig. 6 XPS spectra of W-4f with various implantation procedures [4] J. Kovac, et al., Vacuum 82 (2008) C + -D 2 + simultaneous imp. ・・・ The positive peak shift of about 0.4 eV Only C + imp. ・・・ The positive peak shift of about 0.9 eV W ： 31.5 eV [4] C + -D 2 + simultaneous implantation→C-W bond Only C + implantation → carbon rich tungsten carbide (WC x ) Main Chemical states Results and Discussion (2)

Fig. TDS spectra with various implantation procedures

Fig. Total retention for the simultaneous implanted W with various C + /D + ratio

Implantation Depth Fig. 2 SRIM calculation results for implantation depth The implantation depth of 10 keV C + is almost the same as that of 3 keV D 2 +

Deuterium ion gun Ion implantation chamber Sample insert port Fig. 1 The simultaneous C + and D 2 + implantation system (a) Photograph (b) Diagrammatic illustration Carbon ion gun Apparatus TDS chamber D 2 + ion gun QMS Manupilator Differential pumping system G.V. C + ion gun TDS chamber Ion implantation chamber (a) (b) Ion source gas: CO 2 E×B mass separation filter