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Overview of TCV Results

Overview of TCV Results. Ambrogio Fasoli for the TCV Team 1 Centre de Recherches en Physique des Plasmas Ecole Polytechnique Fédérale de Lausanne, Switzerland Association EURATOM-Swiss Confederation

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Overview of TCV Results

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  1. Overview of TCV Results Ambrogio Fasoli for the TCV Team1 Centre de Recherches en Physique des Plasmas Ecole Polytechnique Fédérale de Lausanne, Switzerland Association EURATOM-Swiss Confederation S.Alberti, P. Amorim (IST Lisbon, P), G. Arnoux, E. Asp, R. Behn, M. Bernard, P. Blanchard, A. Bortolon, A. Bottino, Y. Camenen, S. Coda, L. Curchod, B. Duval, E. Fable, A. Fasoli, W. Fundamenski (UKAEA, Cuhlam Science Center, UK), I. Furno, E.O. Garcia (Risö National Lab., DK), S. Gnesin, T. Goodman, J. Graves, A. Gudozhnik, B. Gulejova, M. Henderson, J.-Ph. Hogge, J. Horacek, B. Joye, A. Karpushov, I.Klimanov, H. Laqua (IPP-Greifswald, D) J.B. Lister, X. Llobet, T. Madeira (IST Lisbon, P), A. Marinoni, J. Marki, Y. Martin, M. Maslov, J.-M. Moret, A. Mueck, V. Naulin (Risö National Lab., DK), A.H. Nielsen (Risö National Lab., DK), I. Pavlov, V. Piffl (IPP Praha, CZ), R.A. Pitts, A. Pitzschke, A. Pochelon, L. Porte, J.J. Rasmussen (Risö National Lab., DK), O. Sauter, A. Scarabosio, H. Shidara, Ch. Schlatter, A.Sushkov (RRC Kurchatov, RF), G. Tonetti, M.Q. Tran, G. Turri, V. Udintsev, G. Véres (KFKI, Budapest, H), F. Volpe (IPP-Greifswald, D), H. Weisen, A. Zabolotsky, A. Zuchkova, C. Zucca.

  2. The TCV tokamak • R= 0.88m; a= 0.25m • BT ≤ 1.5T; Ip ≤ 1.2MA • 0.9< k <2.8; -0.6< d <0.9 • X3: 118GHz • 3  0.5MW, 2s • Top launch ECH • ncut-off = 11.51019m-3 • X2: 82.7GHz • 6  0.5MW, 2s • Side launch ECH, ECCD • ncut-off = 4.21019m-3 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  3. TCV research lines and lay-out of the talk • Transport of particles, energy and momentum in shaped plasmas • Density profile peaking in the absence of core particle source • Influence of plasma triangularity on energy transport • Spontaneous plasma rotation • Edge physics • Origin of anomalous transport in SOL • H-mode physics • High bN and stationary ELM-free regimes with strong electron heating • ECH and ECCD physics • Electron Bernstein wave heating • High performance steady-state scenarios • Electron Internal Transport Barriers: performance and role of q-profile • Outlook 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  4. ne0/<ne> Total power (MW) Density profile peaking • L-mode: profile flattening with core ECH saturates at PEC~3POH • Profiles remain moderately peaked, ne0/<ne>~1.5 • Peaking factor scales with current profile peaking and ECH deposition radius rdep Zabolotsky et al., EX/P3-7 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  5. ne0/<ne> eITBs H-mode Total power (MW) Density profile peaking • L-mode: profile flattening with core ECH saturates at PEC~3POH • Profiles remain moderately peaked, ne0/<ne>~1.5 • Peaking factor scales with current profile peaking and ECH deposition radius rdep • Stationary ELMy H-modes, eITBs • Density profiles are peaked despite pure electron heating and no core source ITER a-heated plasmas will have peaked density profiles Weisen et al., EX/8-4 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  6. OH Influence of plasma triangularity on transport • Large collisionality range: neff~ 0.15 - 2 • L-mode, large Te gradient: R/LTe>10 • Ohmic and EC heated • rdep=0.4, just outside q=1 • no ECCD • ce depends on ne, Te, Zeff via neff • ce decreases for increasing neff and for decreasing d (tE doubles from d=+0.4 to d=-0.4) • Gyro-fluid, gyro-kinetic models • TEM dominant, transport (mixing length) predicted to decrease with d, as observed Camenen et al., EX/P3-20 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  7. rinv Spontaneous plasma rotation • Diagnostic NBI • Vacc50kV, Pdeposited<20kW • Negligible induced rotation < 2km/s • Stationary toroidal rotation profiles in L-mode 170kA<Ip<320kA; <ne> < 3.7x1019 m-3 D-NBI • Counter current rotation (vde) • vf(r)~constant inside sawtooth inversion radius 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  8. rinv Spontaneous plasma rotation • Diagnostic NBI • Vacc50kV, Pdeposited<20kW • Negligible induced rotation < 2km/s • Stationary toroidal rotation profiles in L-mode 170kA<Ip<320kA; <ne> < 3.7x1019 m-3 • Counter current rotation (vde) • vf(r)~constant inside sawtooth inversion radius • Rotation decreases with Ip • Outside sawtooth inversion radius • vf(r)  Ti(r) • Empirical scaling for qe>3.2 • vf,max -const. Ti,max/Ip A. Scarabosio et al, PPCF 48 (2006) 663 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  9. Toroidal rotation inversion • Transition to regime with core rotation in co-current (vdi) direction during ne ramp • Ip>300kA, qe<3.5 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  10. Toroidal rotation inversion • Transition to regime with core rotation in co-current (vdi) direction during ne ramp • Ip>300kA, qe<3.5 • Dynamical evolution of rotation profile 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  11. Toroidal rotation inversion at high density • Transition to regime with core rotation in co-current (vdi) direction • Ip>300kA, qe<3.5 • Dynamical evolution of rotation profile 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  12. Toroidal rotation inversion at high density • Transition to regime with core rotation in co-current (vdi) direction • Ip>300kA, qe<3.5 • Dynamical evolution of rotation profile • Rotation is inverted up to r~0.8 • Similar shape, magnitude in core • Small variations for r>0.8 • Incompatible with momentum diffusion from edge  Mechanism? Bortolon et al., to be published on PRL (2006) 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  13. Origin of SOL transport • Measurements of turbulent particle flux, Gturb, in Ohmic plasmas, Ip=340 kA, single lower null divertor geometry • At the wall radius (important for main chamber recycling) transport is well described by effective convective velocity • Veff = Gturb/n, with Veff independent of n Horacek et al., EX/P4-21 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  14. Conditionally averaged n Origin of SOL transport • Comparison with 2D e.s. fluid model ESEL, with B effects (interchange drive) • Density field evolution shows radial propagation of blobs separatrix wall • Predicted sharp rise and trailing edge of density agree with measured temporal evolution of large amplitude bursts at wall radius • Agreement also on profiles of ne, dne/ne, pdf moments Horacek et al., EX/P4-21  Intermittent SOL transport is due to interchange driven radial motion of blobs 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  15. H-mode physics: High bN regime • Full X3 power (1.45MW) applied to raise b, Ti/Te at high density • Target plasma • ELMy H-mode • ne0~71019m-3 (max absorption) • Low q95~2.5, k~1.6, d~0.4 • Te~1keV, Ti~550eV • Achieved btor~2.5%, bN~2 • Large ELMs (DWdia/W15%) • Ion heating: Ti~1keV at r~0.6 X3 heating phase Porte et al., EX/P6-20 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  16. H-mode physics: Stationary ELM-free regime • Same ne as ELMy, but lower tparticle than transient ELM-free • tE~25ms, HIPB(y,2)~1.4-1.7, Zeff~3 • Different regime from • RI-mode • high Z imp., ion heating • EDA-mode • q95>3.7 (TCV: q95~2.5) • Te/Ti~0.3-0.5 (TCV: Te>Ti) • EHO-mode • NBI, cryo-pumping • Type II ELMy H-mode • q95>4 (TCV: q95~2.5) X3 heating phase Porte et al., EX/P6-20 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  17. Electron Bernstein wave heating • EB waves not subject to density cut-off • Alternative method for local heating of high density plasmas • O-X-B double mode conversion scheme • Needs large n • Target plasma in H-mode (d~0.55, low q95~2.5) • rdep~0.7-0.8 to avoid sawtooth perturbations (BT=1.4T) ART ray tracing calculation of wave path Pochelon et al., EX/P6-20 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  18. Electron Bernstein wave heating • Local deposition from soft X-ray profile at power modulation frequency • Deposition observed • In overdense region • Close to ART prediction (rdepexp~0.71, rdepth~0.78) • Long pulses at BT=1.2T, rdep~0.4, PEC~1MW • Heating observed (DTe~80eV, DTe/Te~10%) • First proof-of-principle of EBH via O-X-B in conventional aspect ratio tokamak  Potential for routine use of EBH and EBCD to be explored Pochelon et al., EX/P6-20 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  19. ne [1019 m-3] Te [keV] Electron Internal Transport Barriers • Obtained routinely with strong ECCD • eITB operational control tools • X2 ECCD power (3MW), location • OH transformer (10kW, pure current source) • Steep gradients of Te, ne • Steady-state • Vloop  0 • Stationary conditions • >100tE, ~10 tCRT • Can give rise to slow (~10Hz), m=n=0 Te, Ip oscillations, coupled to MHD activity, suppressed by adjusting the current profile 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  20. HRLW ~ tE/tL-mode bootstrap current fraction eITB performance • High confinement obtained with high bootstrap current fraction and bpol • In eITB region ne/ne~0.5Te/Te(thermo-diffusive pinch) Coda et al., EX/P1-11 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  21. HRLW ~ tE/tL-mode qmin~2.8 from barrier from OH L-mode qmin~1.8 JOH co- JOH counter- qmin=q0~1.7 Vloop [V] eITBs and q-profile • Role of q-profile investigated by inducing small OH current perturbations • co-ECCD off axis • ECH on axis • Negative central shear crucial for eITB • eITB strength and HRLW increase as shear becomes more reversed • eITB location unaffected • No special role of low-order rational qmin-surfaces (1.7<qmin<2.9) Coda et al., EX/P1-11 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  22. Summary and Outlook • TCV is addressing questions that limit our understanding of magnetic fusion plasmas and our ability to control them in ITER relevant scenarios, and is exploring properties of regimes of interest for future experimental reactors • Short term improvements • Fully digital, non-linear controller • Diagnostic upgrades: q-profile, turbulence (edge, core), ELM dynamics, fast electrons, plasma poloidal rotation and radial electric field • Medium term hardware developments under consideration • ELM control coils • Fast ion physics tools (e.g. Alfvén wave antenna) • Additional X3 power (total ~2.6MW) • Higher B-field operation (118GHz as X2) and/or direct ion heating by NBI (3MW) • Access to higher densities and larger Ti/Te • Exploration of b limits beyond the reach of present X2 and X3 ECH 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  23. TCV related posters • Transport of particles, energy and momentum in shaped plasmas • Zabolotsky et al., EX/P3-7: “Particle and impurity transport in electron heated discharges in TCV” • Camenen et al., EX/P3-20: “Impact of plasma shaping on electron heat transport in TCV L-mode plasmas at various collisionalities” • Edge physics • Horacek et al., EX/P4-21: “On the origin of anomalous radial transport in the tokamak SOL” • H-mode physics • Porte et al., EX/P6-20: “Plasma dynamics with 2nd and 3rd harmonic ECRH on TCV tokamak” • ECH and ECCD physics • Pochelon et al., EX/P6-2: “Electron Bernstein wave heating of overdense H-mode plasmas in the TCV tokamak via O-X-B double mode conversion” • High performance steady-state scenarios • Coda et al., EX/P1-11: “The physics of electron transport barriers in the TCV tokamak” 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  24. 21st IAEA Fusion Energy Conference, Chengdu, October 2006

  25. Low frequency oscillations in eITB regime • Slow (~10Hz), m=n=0 Te, Ip oscillations, coupled to MHD activity • Ex. with OH + counter-ECCD on-axis • Similar phenomenon observed in fully non-inductive case • Oscillations are removed by either reducing or increasing core shear • Co- or counter-current OH perturbation 21st IAEA Fusion Energy Conference, Chengdu, October 2006

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