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SUNIST. JSPS-CAS Core University Program , 2005. Preliminary experiment of plasma current startup by ECR wave on SUNIST spherical tokamak HE Yexi, ZHANG Liang, *FENG Chunhua, FU Hongjun, GAO Zhe, TAN Yi, WANG Wenhao, *WANG Long, *YANG Xuanzong, XIE Lifeng

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  1. SUNIST JSPS-CAS Core University Program, 2005 Preliminary experiment of plasma current startup by ECR wave on SUNIST spherical tokamak HE Yexi, ZHANG Liang, *FENG Chunhua, FU Hongjun, GAO Zhe, TAN Yi, WANG Wenhao, *WANG Long, *YANG Xuanzong, XIE Lifeng yexihe@mail.tsinghua.edu.cn, 86-10-62791874 (o), 86-10-62782658 (fax) SUNIST United Laboratory Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China *Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China This work was supported by JSPS-CAS Core-University Program on Plasma and Nuclear Fusion, the National Nature and Science Fund of China (Grant numbers: 10275041 and 10375089) , and International Atomic Energy Agency (Research contract No. 12935/R0) . SUNIST- Sino UNIted Spherical Tokamak

  2. UNIST SUNIST OUTLINE SUNIST spherical tokamak Preliminary result Remained questions

  3. UNIST SUNIST SUNIST spherical tokamak SUNIST United Laboratory SUNIST United Laboratory founded in 2004, consists of Department of Engineering Physics, Tsinghus University (DEP) ; Institute of Physics, Chinese Academy of Science (IOP) and keeping very close collaboration with Southwestern Institute of Physics (SWIP) and Institute of Plasma Physics, Chinese Academy of Science (IPPAS). Members of SUNIST Laboratory He, Yexi Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-10-62791874(lab), 86-10-62782658(fax), yexihe@mail.tsinghua.edu.cn (e-mail) Yang, Xuanzong Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China 86-10-82649132(office), xzyang@aphy.iphy.ac.cn (e-mail) Wang, Long Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China 86-10-82649137(office), wanglong@aphy.iphy.ac.cn (e-mail) Feng, Chunhua Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China 86-10-82649132(office), chfeng@aphy.iphy.ac.cn (e-mail) Gao, Zhe Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-10-62776446(lab), 86-10-62782658(fax), gaozhe@mail.tsinghua.edu.cn (e-mail) Wang, Wenhao Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-10-62776446(lab), 86-10-62782658(fax), whwang@mail.tsinghua.edu.cn (e-mail) Xie, Lifeng Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-10-62776446(lab), 86-10-62782658(fax), xielf@mail.tsinghua.edu.cn (e-mail)

  4. SUNIST SUNIST spherical tokamak SUNIST spherical tokamak SUNIST main parameters: major radius R 0.3m minor radius a 0.23m Aspect ratio A ~1.3 elongation κ ~1.6 toroidal field （R0）BT0.15T plasma current IP 0.05MA flux (double swing) ΔΦ 0.06Vs

  5. UNIST SUNIST SUNIST spherical tokamak SUNIST spherical tokamakmagnets and power supply Vacuum vessel and BV magnet assembling toroidal magnet pre-assembling Cross section and designed magnetic surface

  6. SUNIST SUNIST spherical tokamak SUNIST spherical tokamakvacuum and vacuum vessel main parameters – vacuum vessel: outer diameter 1.2 m inner diameter 0.13 m height 1.2 m volume ~ 1 m3 surface area ~ 2.3 m2 vacuum pumps: TMP (1000l//s) Sputtering Ti pump (200l/s) wall conditioning: baking: PTC（Curie point 160 0C) glowing discharge, siliconization background pressure:~ 6×10-5 Pa leaking rate on cross seal:≯2×10-7 Pam3/s

  7. SUNIST SUNIST spherical tokamak SUNIST spherical tokamakdiagnostics and data acquisition Diagnostics electromagnetic probes:2 Rogowski probes, 9 flux loops (4 inside vessel) 15 2-D minor probes (13 in one poloidal cross section) electrostatic probes:sets of movable 4 probes for Isi, Φ, and Vtoroidal Data acquisition: 48 channel ADC: 32ch new, 16ch used in CT-6B

  8. SUNIST SUNIST spherical tokamak Typical Discharge

  9. UNIST SUNIST OUTLINE SUNIST spherical tokamak Preliminary result Remained questions

  10. SUNIST Preliminary result Typical discharge of ECR startup Microwave: Pout ~ 100kW, t pulse ~ 30 ms, f = 2.45 GHz background pressure < 110-5 Pascal hydrogen pressure ~ 110-2 Pascal during discharge

  11. SUNIST Preliminary result Discharge with a group of plasma current peaks

  12. SUNIST Preliminary result Dependence of plasma current on vertical field

  13. SUNIST Preliminary result Electrode arrangement

  14. SUNIST Preliminary result Typical discharge with electrode assistance

  15. SUNIST Preliminary result Plasma current counteracted by electrode current

  16. SUNIST Preliminary result One special discharge with electrode assistance

  17. SUNIST Preliminary result Special discharges in CT-6B in 1997

  18. SUNIST Preliminary result Performances of preliminary ECR current startup Plasma current is just a peak ~ hundred millisecond of bottom width. The dependence of driven plasma current on vertical fieldis consistent with the toroidal plasma current by vertical field drift effect in ECR plasma. Plasma current could increase above 10%(Fig. 7) in co-direction Plasma current would be counteracted more obviously(Fig.8), in counter-direction We obtained one special discharge that the current of plasma and electrode is cutoff with on density and Iisat limitation, and the same time scale of injected wave

  19. UNIST SUNIST OUTLINE SUNIST spherical tokamak Preliminary result Remained questions

  20. SUNIST Remained questions Remained questions This kind of plasma current peak is impossible to develop to typical ST plasma current. We didn't consider the mode conversion to EBW in microwave launch system, then we faced the density cut off problem of ECR wave propagated in plasma. That is an only way to modification the feeding line & antenna according to the request of mode conversion to electron Bernstein wave.

  21. SUNIST Remained questions Remained questions The discharge shown in Fig. 9 suggests that there is a discharge regime with no limitations of density cut off on ECR current startup and Ii-sat with electrode discharge assistance. The questions are why this regime exists and how to find it for developing it from occasional event to reproducible discharge.

  22. SUNIST Remained questions Remained questions In preliminary experiments, the background pressure of vacuum vessel increased from less than 110-5 Pascal up to a balanced value, ~ 310-5 Pascal. Driven plasma current decreased with the increase of background pressure just like to scan fuelling gas to higher pressure. It is necessary to control wall condition for further experiments.

  23. SUNIST JSPS-CAS Core University Program, 2005 Preliminary experiment of plasma current startup by ECR wave on SUNIST spherical tokamak THANKS SUNIST- Sino UNIted Spherical Tokamak

  24. SUNIST Preliminary result Vertical field effect on driving toroidal current

  25. SUNIST Preliminary result Toroidal field and ECR layer

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