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Deuterium retention on HT-7 with full metal PFMs

Deuterium retention on HT-7 with full metal PFMs. H.Y. Wang, J.S. Hu, X. Gao, B. Cao Institute of Plasma Physics, Chinese Academy of Sciences, China. 1. outline. Introduction Retention in tokamaks Motivation Method: Particle balance Retention in various materials Molybdenum PFMs

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Deuterium retention on HT-7 with full metal PFMs

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  1. Deuterium retention on HT-7 with full metal PFMs H.Y. Wang, J.S. Hu, X. Gao, B. Cao Institute of Plasma Physics, Chinese Academy of Sciences, China 1

  2. outline • Introduction • Retention in tokamaks • Motivation • Method: Particle balance • Retention in various materials • Molybdenum PFMs • Lithium PFMs • Boron PFMs • Summary 2

  3. Retention in tokamaks • Fuel retention on walls would lead recycling and density control problem which would terminate plasma discharge, specially in a long plasmas required in future SSO fusion devices; • Fuel retention would also cause safety problem, such as T operation in ITER. • In 2011, HT-7 PFMs was changed from C to Mo, and Li coating become main method for wall conditioning. 3

  4. Motivation • Investigation of D retention on different plasma facing materials, such as Mo, Li and B coated films. • Comparison with the previous retention on doped graphite on HT-7. • Realize the PFMs influence on fuel retention. • Provide data accumulation for EAST(PFM will be Mo/W) and ITER. 4

  5. Method • Particle Balance (PB) • Real-time • Global inventory • Couldn’t give location ofretention • Post-mortem Analysis (PA) • Location of retention • Accumulated retention • Couldn’t tell inventory of one shot or one day • During 2011 campaign of HT-7: • Mo tiles: 1.28m2 • Li coating: 28 times (totally 350g) • 1 boronization following Li coatings 5

  6. outline • Introduction • Retention in tokamaks • Motivation • Method: Particle balance • Retention in various materials • Molybdenum PFMs • Lithium coating PFMs • Boron PFMs • Conclusion 6

  7. 2.1 Retention on Mo tiles • In beginning shots, D release from walls due to disruptions. • D retention during D wall conditioning before plasma operation; • Most of plasmas was disrupted at low current， I<90KA, t<1s. • Very small fueling, <30Pa.l • After ~100 plasma discharges, the retention ratio increased, but lower than ~10%. 7

  8. 2.2 Retention on Li coated films • After Li coating • Retention ratio increased (Mo). • Required more fueling. After the 4th Li coating, the retention ratio increased 20%. 8

  9. After each coating, high retention ratio on fresh films, then it decreased slowly to a steady value; • Steady retention ratio after each coating also increased with increasing of coated Li quantity. The 27th time lithium coating Fueled gas: 1000~1500 Pa.l 9

  10. 2.3 Retention on B films • Boronization: • Followed 28 Li coatings • 3g C2B10H12 • After the boronization, • Abundant H released (80% in pumped gases); • H/(H+D) raised from 20% to 80%; • Increase retention ratio, possible due to H-D exchange; 10

  11. The inventory divide by plasma length is called retention rate • Although the Li films stable retention ratio is higher than the boron's, their stable retention rate is almost same (400 Pa.l/s). • The H/(H+D) can explain this well. 11

  12. Accumulated influence • The retention fuel increased shot by shot, there is no signal of saturation (Li, B films). 12

  13. Comparison (HT-7)

  14. outline Introduction Retention in tokamaks Motivation Method: Particle balance Retention in various materials Molybdenum PFMs Lithium coating PFMs Boron PFMs Summary 14

  15. Summary • We have systemically investigate D retention on various walls, such as Mo, Li and B coated films, in 2011 campaign of HT-7; • Compared with Mo (possible W), it was found Li and B films, also C has a high retention ratio for D retention; • The different of the retention on various walls maybe reveal its various mechanism; • This research would give same reference for D retention on Mo walls in EAST, and data accumulation for T retention in ITER.

  16. Thanks for your attention! • Acknowledgments • This research is funded by National Magnetic confinement Fusion Science Program under contract 2010GB104002 and the National Nature Science Foundation of China under contract 11075185. • Thank Bernard PEGOURIE from IRMF for his useful discussion for some basic issues. 16

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