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Lithium experiments on HT-7 and EAST tokamak G. Z. Zuo, J. S. Hu, Z.S, J. G. Li, EAST team

Lithium experiments on HT-7 and EAST tokamak G. Z. Zuo, J. S. Hu, Z.S, J. G. Li, EAST team Institute of Plasma Physics, Chinese Academy of Sciences, China D.K. Mansfield, L.E. Zakharov Princeton Plasma Physics Laboratory, Princeton, USA Jan. 23, 2010. Outline. Introduction

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Lithium experiments on HT-7 and EAST tokamak G. Z. Zuo, J. S. Hu, Z.S, J. G. Li, EAST team

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  1. Lithium experiments on HT-7 and EAST tokamak G. Z. Zuo, J. S. Hu, Z.S, J. G. Li, EAST team Institute of Plasma Physics, Chinese Academy of Sciences, China D.K. Mansfield, L.E. Zakharov Princeton Plasma Physics Laboratory, Princeton, USA Jan. 23, 2010

  2. Outline • Introduction • Lithium limiter on HT-7 • Lithium coating on EAST • Latest results on EAST • Further plan

  3. Inner Structure of HT-7 • Main limiter • toroidal limiter on the top and bottom of HT-7 : R270mm, 1.2m2 • belt Limiter located at high field side:R270mm, 0.54m2 • total limiter area: 1.74m2 • Other limiter • south and northpoloidal limiter: R275~280mm, 0.06m2 • guard Limiter for protecting LHCD antenna: R276~278mm, 0.077m2 • total area: 0.137m2 • Medium-sized superconducting tokamak; • Major radius 1.22 m; • Minor radius 0.27 m; • Plasma volume ~1.75 m3; • First wall materials: • stainless steel; • 18% covered by graphite tiles.

  4. Lithium limiter on HT-7 • First lithium limiter experiment • Free lithium surface; • Lithium plate with plasma facingarea~377cm2;(130mm in width, 290mm in length). • The lithium is 3mm in thickness. • SS dish has Mo protection at each side. • Second lithium limiter experiment • CPS configuration was used for confinement of lithium; • Other structure similar to the first lithium limiter. • Liquid Lithium was kept to 230degree during plasma discharge

  5. Results of lithium limiter with free surface on HT-7 • H recycling measured by Hα intensity decreased by a factor of 4; • The carbon and oxygen impurities measured by CIII and OV spectroscopy decreased; • Loop voltage had a slight decline; the core electron temperature slightly increased;

  6. Plasma confinement • Particle confinement time increased by a factor of 2; and the energy confinement time increased from 25.86ms to 30.04ms.

  7. Lithium limiter with CPS configuration on HT-7 • Further reduction of H recycling; • Impurity radiation was further decreased; • Improvement of lithium confinement using CPS configuration by comparing lithium distribution after experiment.

  8. Outline • Introduction • Lithium limiter on HT-7 • Lithium coating on EAST • Latest results on EAST • Further plan

  9. Introduction of EAST • EAST • Non – circular advanced steady-state experimental device; • Plasma volume ~26m3; • Plasma facing areas~50~60m2; • EAST had a major radius R=1.847 m, a minor radius a=0.483m, the position of moveable limiter R=2.33m, an elongation rate of 1.7-1.9 • Doped graphite (GBST1308：1%B，2.5%Si，7.5%Ti）with 100~200 micron SiC coating was served for the plasma facing materials. EAST

  10. First Lithium coating on EAST by evaporation and ICRF discharge in 2009 • Lithium coating using lithium evaporation at single position by means of ICRF plasma on EAST in 2009 • Only 2 grams of lithium injection; • SXR radiation and total impurity radiation decreased; • Higher and broader electron temperature distribution; Lithium oven

  11. Lithium coating on EAST • Evaporating lithium by oven to realize lithium coating as a routine way in the second campaign in 2010 • Total 67 times and use 982.4g lithium • Using two ovens • 14.2 grams lithium/oven • 500~550℃/outside of oven • 1~2Hr./coating • 10~28.4g/coating;1-2 time /day(~100 shots) • Inserted oven to more close to center of vacuum vessel • By means of ICRF/GDC or only evaporation oven Red zone during lithium coating Red zone during lithium coating oven 300 ℃ 475 ℃ ICRF lithium coating

  12. Li coating by dropper from PPPL dropper 120 • 50mg/s for EAST • 3 x106 Li Spheres/s • ~2 x D influx EAST • 14 x Evaporator Rate Li Powder 100 80 Output (mg/s) 60 40 20 0 0 2 4 6 8 10 12 Applied RMS Voltage • Real time coating by Li powder dropper: • ~50 mg/s; • lithium injecting during 550 discharges; • Using about 38.9g lithium powder in second campaign in EAST Lithium powder 44 µm dia. 30 nm Li2CO3 99.9% Li 0.1% Li2CO3

  13. Results of lithium coating on EAST by oven • Easy plasma recover • After lithium coating, plasma recovers after ~1 shot; • After siliconization, about 5-10shots ; • Without wall coating, it needs more shots to recover. • Realize 1MA plasma current ; • Lower H recycling; • Decrease H/H+D from about 45% before lithium coating to • below 10%(min ~7%) to lead to improve ICRF heat efficiency. • Reduce impurity radiation, Zeff~2 during plasmas; • Suppress MHD activity; • Improve plasma confinement; • increase plasma stored energy; • Reduce H-mode power threshold and get H-mode.

  14. Effect of lithium coating on plasma #29686 and 29688: before lithium coating #29689:the first shot after lithium coating • Via the lithium coating • the plasma can restore quickly and the plasma current • can be easily controlled; • also the disruption discharges significantly reduces.

  15. Effect of lithium coating on plasma Circular plasmas Divertor plasmas with double null By lithium coating, impurity and MHD activity (magnetic probe measurement) was effectively.

  16. Improvement of ICRF heating efficiency H/H+D ~10% Te increase ~200ev Stored energy~10kJ • Siliconization: H/H+D above 25% • Lithium coating : ~10%(min ~7%) to lead to improve ICRF heat efficiency.

  17. H-mode after lithium coating by oven • Ip/600kA/Nel~2./LHW~1MW/It~7000A; • H-mode keeps about 200ms • H/(H+D)~7% # 32924 CCD

  18. Results of lithium powder injection on EAST • Lithium powder injection is very effective in suppressing MHD (spring campaign in 2010 on EAST ).

  19. Improve plasma performance using lithium powder injection-H mode #32525 :Before the shot , ~100g lithium coated by oven, powder injection from 1.9s to 2.9s, the confinement improves from about 4.8s; #32537: IT～ 6000A, IP～600kA， ne～2.1*1019/m2， PLHCD~1MW, LSN from 3s; before the shots, about 30 shots lithium powder injection Initial phase statistics about H mode:No.32525-33590: Total H-mode plasma: 141 shots (37.5 %) ; In H-mode plasmas, lithium powder injection:61 shots, 43.3 %.

  20. #32537 CCD

  21. Benefit for long plasma operation by Lithium injection Plasma current(KA) CIII emission LiII emission Ha emission MHD signal 91s plasma discharge with 9 times lithium powder injection during a discharge

  22. Benefit for H mode discharge by lithium injection Longest H mode shot when using 4 times lithium powder injection During a discharge in EAST

  23. Outline Introduction Lithium limiter on HT-7 Lithium coating on EAST Latest results on EAST Further plan

  24. Latest results on EAST— 6.4s H mode New milestone:H-mode Operation 6.4S！ Ip Ip ne PLHCD Beta P PICRF WDIA Da/Ha ECE Sx-ray XUV Ip~0.6MA, Bt=1.9T, ΔWDIA>45KJ,PICRF=0.75MW, f=27MHz,PLHCD=1.0MW, f=2.45GHz

  25. Latest results on EAST—100s long pulse

  26. Latest results on EAST—1MA plasma

  27. L-H transition in current ramping up and down phase L-H transition in current ramping down phase L-H transition in current ramping up phase

  28. DN LSN

  29. Outline • Introduction • Lithium limiter on HT-7 • Lithium coating on EAST • Latest results on EAST • Further plan

  30. Future plan • Design new systems of lithium coating : • Another two new ovens evaporating systems—four systems for next campaign in EAST • Design and upgrade lithium dropper. • Bench test for flowing liquid lithium limiter for HT-7 • 2010-2011 • Test whether liquid lithium can fluently flow by means of pump driving; • Some problems related with field and plasma can not resolve in preliminary experiment • Full metal walls with lithium limiter in HT-7 • 2011-2012 • Remove all graphite limiter • Install Mo poloidal limiter • Modify the bottom to lithium limiter with a large area • Possibly after 2014 for EAST • 2014 • After all PFCs be modified from C to W • Flowing liquid lithium divertor

  31. Bench test

  32. HT-7 lithium limiter 1and 2:Poloidal Mo limiter 3:removable Mo limiter 4:high field Mo limiter 5and6: liquid lithium limiter

  33. Thank you for your attention!

  34. Lithium limiter with CPS configuration on HT-7 • Improvement of lithium confinement using CPS configuration . • In the case of lithium limiter with free surface, lithium spots were so big and dense; • When using CPS on the top of the lithium limiter, lithium spots were small. Lithium spots deposited by using free lithium surface Lithium spots deposited by using lithium limiter CPS configuration

  35. Outline • Introduction • Lithium limiter on HT-7 • Lithium coating on EAST • Latest results on EAST • Further plan

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