Overview of TCV Results Ambrogio Fasoli for the
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 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. 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
The TCV tokamak q R= 0. 88 m; a= 0. 25 m q BT ≤ 1. 5 T; Ip ≤ 1. 2 MA q 0. 9< k <2. 8; -0. 6< d <0. 9 • X 2: 82. 7 GHz • 6 0. 5 MW, 2 s • Side launch ECH, ECCD • ncut-off = 4. 2 1019 m-3 2 • X 3: 118 GHz • 3 0. 5 MW, 2 s • Top launch ECH • ncut-off = 11. 5 1019 m-3 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
TCV research lines and lay-out of the talk q 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 q Edge physics • Origin of anomalous transport in SOL q H-mode physics • High b. N and stationary ELM-free regimes with strong electron heating q ECH and ECCD physics • Electron Bernstein wave heating q High performance steady-state scenarios • Electron Internal Transport Barriers: performance and role of q-profile q Outlook 3 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Density profile peaking • Profiles remain moderately peaked, ne 0/<ne>~1. 5 • Peaking factor scales with current profile peaking and ECH deposition radius rdep ne 0/<ne> q L-mode: profile flattening with core ECH saturates at PEC~3 POH Total power (MW) Zabolotsky et al. , EX/P 3 -7 4 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Density profile peaking • Profiles remain moderately peaked, ne 0/<ne>~1. 5 • Peaking factor scales with current profile peaking and ECH deposition radius rdep ne 0/<ne> q L-mode: profile flattening with core ECH saturates at PEC~3 POH e. ITBs H-mode q Stationary ELMy H-modes, e. ITBs • Density profiles are peaked despite pure electron heating and no core source Total power (MW) ITER a-heated plasmas will have peaked density profiles Weisen et al. , EX/8 -4 5 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Influence of plasma triangularity on transport q Large collisionality range: neff~ 0. 15 - 2 q L-mode, large Te gradient: R/LTe>10 q Ohmic and EC heated • rdep=0. 4, just outside q=1 • no ECCD q ce depends on ne, Te, Zeff via neff q ce decreases for increasing neff and for decreasing d (t. E doubles from d=+0. 4 to d=-0. 4) q Gyro-fluid, gyro-kinetic models • TEM dominant, transport (mixing length) predicted to decrease with d, as observed 6 OH Camenen et al. , EX/P 3 -20 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Spontaneous plasma rotation q Diagnostic NBI • Vacc 50 k. V, Pdeposited<20 k. W • Negligible induced rotation < 2 km/s D-NBI q Stationary toroidal rotation profiles in L-mode 170 k. A<Ip<320 k. A; <ne> < 3. 7 x 1019 m-3 rinv q Counter current rotation (vde) q vf(r)~constant inside sawtooth inversion radius 7 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Spontaneous plasma rotation q Diagnostic NBI • Vacc 50 k. V, Pdeposited<20 k. W • Negligible induced rotation < 2 km/s q Stationary toroidal rotation profiles in L-mode 170 k. A<Ip<320 k. A; <ne> < 3. 7 x 1019 m-3 rinv q Counter current rotation (vde) q vf(r)~constant inside sawtooth inversion radius q Rotation decreases with Ip q Outside sawtooth inversion radius • vf(r) Ti(r) q Empirical scaling for qe>3. 2 • vf, max -const. Ti, max/Ip A. Scarabosio et al, PPCF 48 (2006) 663 8 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Toroidal rotation inversion q Transition to regime with core rotation in co-current (vdi) direction during ne ramp • Ip>300 k. A, qe<3. 5 9 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Toroidal rotation inversion q Transition to regime with core rotation in co-current (vdi) direction during ne ramp • Ip>300 k. A, qe<3. 5 q Dynamical evolution of rotation profile 10 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Toroidal rotation inversion at high density q Transition to regime with core rotation in co-current (vdi) direction • Ip>300 k. A, qe<3. 5 q Dynamical evolution of rotation profile 11 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Toroidal rotation inversion at high density q Transition to regime with core rotation in co-current (vdi) direction • Ip>300 k. A, qe<3. 5 q Dynamical evolution of rotation profile • Rotation is inverted up to r~0. 8 • Similar shape, magnitude in core • Small variations for r>0. 8 Ø Incompatible with momentum diffusion from edge Mechanism? Bortolon et al. , to be published on PRL (2006) 12 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Origin of SOL transport q Measurements of turbulent particle flux, Gturb, in Ohmic plasmas, Ip=340 k. A, single lower null divertor geometry q 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/P 4 -21 13 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Origin of SOL transport q Comparison with 2 D e. s. fluid model ESEL, with B effects (interchange drive) • Density field evolution shows radial propagation of blobs separatrix • 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 wall Conditionally averaged n Horacek et al. , EX/P 4 -21 Intermittent SOL transport is due to interchange driven radial motion of blobs 14 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
H-mode physics: High b. N regime q Full X 3 power (1. 45 MW) applied to raise b, Ti/Te at high density q Target plasma • ELMy H-mode Øne 0~7 1019 m-3 (max absorption) ØLow q 95~2. 5, k~1. 6, d~0. 4 ØTe~1 ke. V, Ti~550 e. V X 3 heating phase q Achieved btor~2. 5%, b. N~2 • Large ELMs (DWdia/W 15%) • Ion heating: Ti~1 ke. V at r~0. 6 Porte et al. , EX/P 6 -20 15 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
H-mode physics: Stationary ELM-free regime q Same ne as ELMy, but lower tparticle than transient ELM-free q t. E~25 ms, HIPB(y, 2)~1. 4 -1. 7, Zeff~3 X 3 heating phase q Different regime from • RI-mode Ø high Z imp. , ion heating • EDA-mode Ø q 95>3. 7 (TCV: q 95~2. 5) Ø Te/Ti~0. 3 -0. 5 (TCV: Te>Ti) • EHO-mode Ø NBI, cryo-pumping • Type II ELMy H-mode Ø q 95>4 (TCV: q 95~2. 5) Porte et al. , EX/P 6 -20 16 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Electron Bernstein wave heating q EB waves not subject to density cut-off • Alternative method for local heating of high density plasmas q O-X-B double mode conversion scheme • Needs large n Ø Target plasma in H-mode (d~0. 55, low q 95~2. 5) • rdep~0. 7 -0. 8 to avoid sawtooth perturbations (BT=1. 4 T) ART ray tracing calculation of wave path Pochelon et al. , EX/P 6 -20 17 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Electron Bernstein wave heating q Local deposition from soft X-ray profile at power modulation frequency q Deposition observed • In overdense region • Close to ART prediction (rdepexp~0. 71, rdepth~0. 78) q Long pulses at BT=1. 2 T, rdep~0. 4, PEC~1 MW • Heating observed (DTe~80 e. V, DTe/Te~10%) Pochelon et al. , EX/P 6 -20 • 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 18 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
Electron Internal Transport Barriers q Obtained routinely with strong ECCD q e. ITB operational control tools q Steep gradients of Te, ne q Steady-state • Vloop 0 • Stationary conditions Ø >100 t. E, ~10 t. CRT q Can give rise to slow (~10 Hz), m=n=0 Te, Ip oscillations, coupled to MHD activity, suppressed by adjusting the current profile 19 21 st IAEA Fusion Energy Conference, Chengdu, October 2006 ne [1019 m-3] • OH transformer ( 10 k. W, pure current source) Te [ke. V] • X 2 ECCD power ( 3 MW), location
e. ITB performance HRLW ~ t. E/t. L-mode q High confinement obtained with high bootstrap current fraction and bpol q In e. ITB region ne/ne~0. 5 Te/Te (thermo-diffusive pinch) Coda et al. , EX/P 1 -11 bootstrap current fraction 20 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
e. ITBs and q-profile q Role of q-profile investigated by inducing small OH current perturbations q Negative central shear crucial for e. ITB q e. ITB strength and HRLW increase as shear becomes more reversed q e. ITB location unaffected q No special role of loworder rational qminsurfaces (1. 7<qmin<2. 9) HRLW ~ t. E/t. L-mode Ø co-ECCD off axis Ø ECH on axis qmin~1. 8 qmin=q 0~1. 7 Coda et al. , EX/P 1 -11 21 qmin~2. 8 from barrier from OH L-mode JOH co- Vloop [V] 21 st IAEA Fusion Energy Conference, Chengdu, October 2006 JOH counter-
Summary and Outlook q 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 q 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 q Medium term hardware developments under consideration • ELM control coils • Fast ion physics tools (e. g. Alfvén wave antenna) • Additional X 3 power (total ~2. 6 MW) • Higher B-field operation (118 GHz as X 2) and/or direct ion heating by NBI ( 3 MW) Ø Access to higher densities and larger Ti/Te Ø Exploration of b limits beyond the reach of present X 2 and X 3 ECH 22 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
TCV related posters q Transport of particles, energy and momentum in shaped plasmas • Zabolotsky et al. , EX/P 3 -7: “Particle and impurity transport in electron heated discharges in TCV” • Camenen et al. , EX/P 3 -20: “Impact of plasma shaping on electron heat transport in TCV L-mode plasmas at various collisionalities” q Edge physics • Horacek et al. , EX/P 4 -21: “On the origin of anomalous radial transport in the tokamak SOL” q H-mode physics • Porte et al. , EX/P 6 -20: “Plasma dynamics with 2 nd and 3 rd harmonic ECRH on TCV tokamak” q ECH and ECCD physics • Pochelon et al. , EX/P 6 -2: “Electron Bernstein wave heating of overdense H-mode plasmas in the TCV tokamak via O-X-B double mode conversion” q High performance steady-state scenarios • Coda et al. , EX/P 1 -11: “The physics of electron transport barriers in the TCV tokamak” 23 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
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Low frequency oscillations in e. ITB regime q Slow (~10 Hz), m=n=0 Te, Ip oscillations, coupled to MHD activity q Ex. with OH + counter. ECCD on-axis q Similar phenomenon observed in fully noninductive case q Oscillations are removed by either reducing or increasing core shear • Co- or counter-current OH perturbation 25 21 st IAEA Fusion Energy Conference, Chengdu, October 2006
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