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Introduction to Spherical Tokamak

SUNIST. for 4th Workshop on Nonlinear Plasma Sciences & International School on Plasma Turbulence and Transport. Introduction to Spherical Tokamak. GAO, Zhe Department of Engineering Physics Tsinghua University, Beijing 100084 gaozhe@tsinghua.edu.cn. Hangzhou 2005. OUTLINE

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Introduction to Spherical Tokamak

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  1. SUNIST for 4th Workshop on Nonlinear Plasma Sciences & International School on Plasma Turbulence and Transport Introduction to Spherical Tokamak GAO, Zhe Department of Engineering Physics Tsinghua University, Beijing 100084 gaozhe@tsinghua.edu.cn Hangzhou 2005

  2. OUTLINE • What is the spherical tokamak? • ST advantage • ST worldwide • New physics of toroidal plasmas • Potential contribution

  3. What is the Spherical Tokamak?

  4. Spherical tokamak=low aspect ratio tokamak Aspect ratio, A=R/a

  5. ST in Fusion configuration family

  6. UNIST SUNIST The first ST: START

  7. Advantage Compact configuration Natural elongation Large qaincrease the efficiency of toroidal field (Ip/Irod>1) large plasma current lower toroidal field (paramagnetism) High β High density limit Less major disruption (instead of IREs) Good energy confinement Improved confinement mode achieved

  8. ST worldwide SUNIST SUNIST

  9. Parameters achieved

  10. Extended toroidal plasmas & New Physics • elongation>3, Bp/Bt~1, β~40%, Vrotation/Valfven~0.3 High β, larger rotation, strong shaped equilibrium (2) High β, low Valfven,, strong shear γE*B~106/s Electromagnetic turbulence and tranport at low A (3) a/ρi~30-50, a/ρfast ion~3-10, near omnigeneity, strongly mag well Neoclassical transport at low A (4) Valfven～Vs, Vfast ion>>Valfven ,less damping on TAE Fast ion physics (5) High dielectric constant (ωpe2/ ωce2~50-100) Wave-particle interaction (RF heating &CD) (6) Narrow inner regions and Low li Solenoid-free startup

  11. UNIST SUNIST Topical Research Plan of ST ( NSTX Five Year Plan) • MHD: RWM active and passive stabilzation Fast-ion MHD (Alfven like) NTM (stabilization by RF) High beta equilibrium • Transport and turbulence: high k and low k turbulence H mode Electron thermal barriers Aspect ratio scaling • Wave-plasma interaction: HHFW, EBW • Solenoid-free startup: Transient CHI, PF induction, RF(ECH/EBW) • Boundary Physics: Li conditioning, SOL transport • Integration

  12. What might ST bring to fusion application？

  13. Contribute to AT & burning plasma (ITER) physics • Advanced Tokamak concept High plasma kinetic pressure Good confinement High self-sustained current (Quasi-) Stationary state Advance fuel recycle • Burning plasma

  14. Other application: VNS CTF Contribution to AT and burning plasma research Space propulsion

  15. Future Steps Tokamak * T-3, T-4, ST etc. 1970’s ** PLT, ASDEX etc. later 70’s ***TFTR,JET, JT-60U, 80—90‘s **** ITER 2100’s

  16. SUNIST: Sino United Spherical Tokamak major radius R 0.3m minor radius a 0.23m Aspect ratio A ~1.3 elongation κ ~1.6 toroidal field （R0） BT 0.15T plasma current IP 50kA central rod current IROD 0.225MA flux (double swing) ΔΦ 0.06Vs

  17. Acknowledgement Collecting material from the following references: Peng Y-K, STW2004, Kyoto. Gryaznevich M, STW2004, Kyoto. Peng Y-K, STW2003, Culham. Peng Y-K, Phys. Plasmas 2000, 7(5): 1681. Sykes A, Nucl. Fusion 1999, 39(9Y):1271. NSTX team, NSTX five year research plan Peng Y-K and Strikler DJ, Nucl. Fusion 1986, 26:576 and many ST Websites.

  18. TOKAMAK

  19. Spheromak

  20. UNIST SUNIST ST: more compact

  21. ST: natural elongation

  22. ST: High qa

  23. ST: high beta

  24. UNIST SUNIST ST: high density

  25. ST: more stable for VDI Internal Reconnection Event (IRE)

  26. ST: good confinement

  27. High beta equilibrium with larger rotation

  28. turbulence and transport

  29. Single particle motion in ST

  30. HHFW CD

  31. EBW CD

  32. Diffusion near the T-P boundary

  33. CHI startup

  34. Outer Poloidal Field startup

  35. ECH startup

  36. Bootstrap current MAST (real discharge) NSTX (Theo prediction)

  37. Divertor configuration Divertor configurations in MAST: Single-Null Divertor (SND) Double-Null Divertor (DND) Limited, or Natural Divertor (ND) H-mode in DND and Natural Divertor plasmas

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