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The influence of wall conditionings on hydrogen evolution and removal on EAST

CUP- PWI/PFC and Fusion Technologies 27-29 October, 2008, Huangshan Anhui, China. The influence of wall conditionings on hydrogen evolution and removal on EAST. Y.W.Yu , J.S.Hu , X.Gao , J.H.Li , Y.Chen and Y.P.Zhao. Institute of Plasma Physics, Chinese Academy of Sciences. Outline.

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The influence of wall conditionings on hydrogen evolution and removal on EAST

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  1. CUP- PWI/PFC and Fusion Technologies 27-29 October, 2008, Huangshan Anhui, China The influence of wall conditionings on hydrogen evolution and removal on EAST Y.W.Yu, J.S.Hu, X.Gao, J.H.Li, Y.Chen and Y.P.Zhao Institute of Plasma Physics, Chinese Academy of Sciences

  2. Outline • Introduction • Wall conditioning on EAST • Hydrogen evolution and removal • Summary

  3. Mo limiter ICRF antenna ICRF antenna GDC anode Graphite wall GDC anode Introduction • EAST • 2006-2007 • 316L stainless steel • 2008 • Full graphite • R=1.85 m, a=0.48 m

  4. Wall conditioning on EAST • Baking • GDC: He/D2, 2 A • ICRF: 30 MHz, He/D2, 5-30 kW • Boronization • ICRF + C2B10H12 • Base pressure • Ultimate pressure • Partial pressure (from RGA)

  5. Outline • Introduction • Wall conditioning on EAST • Hydrogen evolution and removal • Baking • GDC • ICRF cleaning • Boronization • Summary

  6. Hydrogen evolution • Hydrogen & wall recycling • Specific source of H • Wall deflation • H2 puffing • Boronization C2B10H12

  7. Baking • Improve wall release • Base pressure of H2 • Similar trend in curve

  8. GDC • Use one of four electrodes, 2 A • Helium 0.5-0.8 Pa • Obvious removal of H2 4 hours GDC in He

  9. ICRF cleaning • Typical parameters: • ICRF Power: 5-30 kW, 0.5s ON/ 2s OFF • Gas species: He/D2 • Neutral pressure: (0.5-1)x10-2 Pa ICRF plasma LFS HFS

  10. ICRF cleaning • Influence of parameters • ICRF power • Gas species • Neutral pressure Totally ~ 2 hours ICRF in D2 + He Notable removal of H2 by ICRF cleaning

  11. Boronization • Great increment of H2 • Major H injection (C2B10H12)

  12. Boronization • Enhanced wall recycling • Ha emission at breakdown • Higher H2 removal by ICRF Followed ICRF cleaning was effective to remove hydrogen

  13. Removal & Base pressure • Pressure in cleaning & base pressure • GDC: Similar trend • ICRF: Approximate same GDC only used at the beginning Base pressure reflects wall condition Pressure in cleaning can also reflect!

  14. Summary • Baking, GDC and ICRF cleaning were effective ways to remove hydrogen on EAST • Boronization (C2B10H12) was a major injection of hydrogen, followed ICRF cleaning was effective to remove hydrogen • Partial pressure of H2 in discharge cleaning had the similar trend with that of base pressure, it could also reflect wall condition besides base pressure

  15. Acknowledgement Thank you for your attention!

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