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Progress and scientific results in the TCV tokamak

Progress and scientific results in the TCV tokamak. S. Coda. for the TCV team*. * including collaborating institutions:. S. Coda, 23 rd IAEA Fusion Energy Conference, OV/5-2, Daejeon , 13 October 2010. Outline. TCV parameters and capabilities Scientific mission and guidelines

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Progress and scientific results in the TCV tokamak

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  1. Progress and scientific resultsin the TCV tokamak S. Coda for the TCV team* *including collaborating institutions: S. Coda, 23rdIAEA Fusion Energy Conference, OV/5-2, Daejeon, 13 October 2010

  2. Outline • TCV parameters and capabilities • Scientific mission and guidelines • Technical progress • Scientific highlights • Torque-free generation and transport of rotation • Particle and energy transport, turbulence • Advanced real-time control • Alternative confinement topologies • Summary and outlook

  3. TCV 4.5 MW ECRH power, 7 steerable launchers R = 0.88 m, a = 0.25 m Ip < 1 MA, BT < 1.54 T k < 2.8, -0.6 < d < 0.9 ×4 ×2

  4. Scientific guidelines of the TCV program • Experiments in preparation for ITER • Alternative configurations,tokamak concept improvement

  5. ITER preparation + alternative paths Multiple steerable EC launchers, r/t controlNTM stabilization

  6. ITER preparation + alternative paths Flexible shaping

  7. Highlights of technical progress • Improved charge exchange spectroscopy resolution(from 2 to 1 cm) + sensitivity (5-10×): Ti, vf, vq,nC • New digital real-time network to control coils and EC systems potential to use massively multichannel diagnostics

  8. Outline • TCV parameters and capabilities • Scientific mission and guidelines • Technical progress • Scientific highlights • Torque-free generation and transport of rotation • Particle and energy transport, turbulence • Advanced real-time control • Alternative confinement topologies • Summary and outlook

  9. Symmetry breaking  toroidal momentum transport by turbulence New theory validated by TCV experiments • Static, up-down symmetric plasma: fundamental symmetry upon reversal of v//andpoloidal angle net turbulence-driven momentum flux is zero • Symmetry breaking  net momentum flux: from vf, vf, or up-down asymmetry(Y. Camenen et al, PRL 2009)

  10. Turbulent momentum transport inward • Direction of radial fluxshould reverse withBfsign, Ipsign, up-down flip • All reversals have been confirmed by experiment B drift Same Bf, Ip outward Bq • Radial turbulent momentum flux changes signas expected from up-down flip • vf varies most at edge where asymmetry is greatest Y. Camenen et al, PRL 105, 135003 (2010)

  11. Spontaneous plasma rotation • observed systematically in TCV L-modes (no torque) • at low to moderate current (qedge>3),vf is counter-current in core • central rotation is limited by sawtooth crashes imparting a co-current spin • vf changes sign at high current and density • New experiments performed to • quantify and document effect of sawteeth(i.e., 1/1 internal kink) and other MHD modes • study effect of ECRH on rotation A. Bortolon et al, PRL 2006 B.P. Duval et al, PPCF 2007 B.P. Duval et al, PoP 2008 A. Fasoli, IAEA 2008 overview

  12. Plasma spin-up at sawtooth crash • Reproducible co-current spin-up inside the inversion radius • Rapid relaxation (in <15% of sawtooth period) • Enhanced CXRS time resolution by coherent averaging over multiple sawteeth Inv. radius B.P. Duval et al, EXC/P4-01 (this afternoon)

  13. Average effect of sawteeth on rotation • ...to the point of changing sign at high enough current • Slightly hollow inside the mixing radius... Self-similar gradients outside the mixing radius

  14. Influencing rotation with ECRHthrough sawteeth • EC power inside mixing radius hollows out vf profile • Similar to Ip increase: consistent with effectof current profile peaking on sawteeth O. Sauter et al, EXS/P2-17

  15. Outline • TCV parameters and capabilities • Scientific mission and guidelines • Technical progress • Scientific highlights • Torque-free generation and transport of rotation • Particle and energy transport, turbulence • Advanced real-time control • Alternative confinement topologies • Summary and outlook

  16. Sawteeth affect particle transportsimilarly to momentum transport Stronger peaking for impurities than for electrons Similar edge gradients Stronger flattening by sawteeth for impurities Electrons Carbon ions Y. Martin et al, EXC/P8-13 (Friday afternoon)

  17. The effect of shape on turbulence • Triangularity strongly influences transport: confinement of EC-heated d=-0.4 plasmas is up to twice as good as for d=+0.4 (for similar profiles) • Gyrokinetic simulations explain this through the effect of toroidalprecessional drift of trapped electrons on TEM turbulence Y. Camenen et al, NF 2007 A. Marinoni et al, PPCF 2009 A. Fasoli, IAEA 2008 overview

  18. The effect of shape on turbulence • Measurements of temperature fluctuations by a tunable 2-channel correlation ECE system reveal a broadband spectrum in the expected 20-150 kHz range

  19. Longer correlation length at d>0 • larger random-walk step, consistent with more transport B. Labit et al, EXC/P8-08 (Friday afternoon)

  20. Outline • TCV parameters and capabilities • Scientific mission and guidelines • Technical progress • Scientific highlights • Torque-free generation and transport of rotation • Particle and energy transport, turbulence • Advanced real-time control • Alternative confinement topologies • Summary and outlook

  21. Real-time control in TCV • All algorithms developed in powerful and intuitive Simulink environment • Real-time nodes generate C code automatically from Simulink

  22. Profile control with ECRH • Based on soft X-ray profile • Simple system with 2 actuators: on- and off-axis ECRH powers to control amplitude and width • Modelparametrizedthrough System Identification from random binary modulation of the EC power J.I. Paley et al, PPCF 51, 124041 (2009) F. Felici, Ph.D. thesis (2011)

  23. Profile control with ECRH Profile peak amplitude J.I. Paley et al, PPCF 51, 124041 (2009) F. Felici, Ph.D. thesis (2011)

  24. Outline • TCV parameters and capabilities • Scientific mission and guidelines • Technical progress • Scientific highlights • Torque-free generation and transport of rotation • Particle and energy transport, turbulence • Advanced real-time control • Alternative confinement topologies • Summary and outlook

  25. The “snowflake” divertor • 2nd order null point (Bq=0, Bq=0) • Sixseparatrix branches, four divertor legs • Increased flux expansion and connection lengthmay alleviate divertor heat loads • Snowflake (SF) is a point along a continuumfrom SF+ to SF-

  26. The snowflake divertor in TCV • SF+ • SF • SF- F. Piras et al, PPCF 51 055009 (2009)

  27. Snowflake H-mode  Promising scaling for average power loss • SFcompared to single-null: • 2-3× slower (type-I) ELMs • only 20-30% more energy loss per ELM • SF compared to • single-null: • similar L-H threshold • SF compared to • single-null: • similar L-H threshold • 2-3× slower ELMs B. Labit et al, EXC/P8-08 (Friday afternoon) F. Piras et al, PRL 105, 155003 (2010) B. Labit et al, EXC/P8-08

  28. Summary • Studies aligned with ITER requirements: • spontaneous generation and transport of momentum • particle and energy transport • effect of shape on turbulence • real-time profile and MHD control • Concept improvement and theory testing: • new mechanism for turbulent momentum transport • snowflake divertor in L- and H-mode

  29. Outlook: major upgrades • Up to 3 MW NBI heating • Up to 3 MW additional X3 ECRH heating • Refurbished LFS first wall for increased power handling • In-vessel ergodization and error-field coilsfor ELM control TCV research is built on unique flexibilityin ECRH and plasma shaping • further empower these unique characteristics • diversify and expand operational domain

  30. CRPP contributions • TCV • EXS/P2-17: O. Sauter et al, “Effects of ECH/ECCD on tearing modes in TCV and link to rotation profile”, Tue pm • EXC/P4-01: B.P. Duval et al, “Momentum transport in TCV across sawteeth events”, Wed pm • EXC/P8-08: B. Labit et al, “Transport and turbulence with innovative plasma shapes in the TCV tokamak”, Fri pm • EXC/P8-13: Y. Martin et al, “Impurity transport in TCV: neoclassical and turbulent contributions”, Fri pm • Fusion technology • FTP/P1-16: N. Baluc et al, “From materials development to their test in IFMIF: an overview”, Tue am • JET • THS/9-1: J.P. Graves et al, “Sawtooth control relying on toroidally propagating ICRF waves”, Sat am • EXW/P7-27: D.S. Testa et al, “Recent JET experiments on Alfvéneigenmodes with intermediate toroidal mode numbers: measurements and modelling, Fri am • Basic plasma physics • EXC/P8-09: A. Fasoli et al, “Turbulence and transport in simple magnetized toroidal plasmas”, Fri pm

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