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OVERVIEW OF ITER PHYSICS

ITER. OVERVIEW OF ITER PHYSICS. V. Mukhovatov 1 , M. Shimada 1 , A.E. Costley 1 , Y. Gribov 1 , G. Federici 2 ,A.S. Kukushkin 2 , A. Polevoi 1 , V.D. Pustovitov 3 , Y. Shimomura 1 , T. Sugie 1 , M. Sugihara 1 , G. Vayakis 1

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OVERVIEW OF ITER PHYSICS

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  1. ITER OVERVIEW OF ITER PHYSICS V. Mukhovatov1, M. Shimada1, A.E. Costley1, Y. Gribov1, G. Federici2,A.S. Kukushkin2, A. Polevoi1, V.D. Pustovitov3, Y. Shimomura1, T. Sugie1, M. Sugihara1, G. Vayakis1 1 International Team, ITER Naka Joint Work Site, Naka, Ibaraki, Japan 2 International Team, ITER Garching Joint Work Site, Garching, Germany 3 Nuclear Fusion Institute, RRC Kurchatov Institute, Moscow, Russia V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  2. Contents • Introduction • ELMy H-mode • Operational limits • Confinement • Instabilities • Improved H-mode • Internal Transport Barriers • Formation • Performance • Control • Summary V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russi

  3. Introduction • Predictive methodologies for tokamak Burning Plasma Experiment (BPX) have been summarized in theITER Physics Basis(IPB)published in 1999 [Nucl. Fusion 39 (1999) 2137-2638]. • In recent years,significant progresshas been achieved in many areas of tokamak physics • New achievements have had significant impact on new ITER design (stronger shaping, methods to suppress NTMs and RWMs) • This talk reviews the ITER physics basistaking account of therecent progressin tokamak studies V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  4. Major ITER-Relevant Confinement Modes • H-mode(High Confinement Mode) associated with formation of edge transport barrier(ETB) • Reference mode for ITER inductive high-Q operation • Improved H-mode • Candidate mode for inductive and/or hybrid ITER operation • Advanced Tokamak(AT) modeassociated with formation of Internal Transport Barrier(ITB) • Candidate mode for steady-state ITER operation V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  5. Physics Rules for Selection of ITER Design Parameters • Q ≥ 10Q = 5Pa/Paux • ELMy H-mode reference operation mode • ITERH-98P(y,2) scaling for energy confinement time • Safety factor q95 ≥ 2.5 q95µ (5B/I)(ka2/R) • Electron density ne ≤ nGnG=I/(pa2), Greenwald density • Normalized beta bN≤ 2.5[bN = b(%)(aB/I)] • Strong plasma shapingksep = 1.85, dsep = 0.48 • Heating power P ≥ 1.3 PL-HP= Pa + Paux- Prad PL-H is H-mode power thresh. V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  6. ELMy H-MODE

  7. ELMy H-mode • ELMy H-mode: H-mode with bursts of Edge Localized Modes (ELMs) • Reference ITER mode for inductive high-Q operation • Robust mode observed in all tokamaks under wide variety of conditions at heating power above the threshold, P>PL-H • Good prospects for long-pulse operation • >20 years of studies • Rich experimental database • High confidence that ELMy H-mode will be obtained in ITER V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  8. Energy Confinement Projections for ELMy H-mode in ITER • Three approaches (discussed in details in IPB) predict compatible results for ITER reference high Q scenario • Transport models based on empirical scalings for the energy confinement time • Physics-based transport models • Dimensionless analysis V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  9. ITER Reference Scalings H-mode power threshold scaling ITER: PL-H= 49 MW [28.4, 84.1]MW 95% interval estimate ITERH-98P(y.2) confinement scaling ITER: tE = 3.66s ±14% [2.78, 4.83]s 95% nonlinear interval estimate J A Snipes et al PPCF 42 (2000) A299 O.Kardaun, Nucl. Fusion 42 (2002) 841 V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  10. Effect of Plasma Dilution with Helium • ITER performance depends onplasma dilution with He • B2/Eirenecode: Helium content in ITER plasma reduces due to Helium atom elastic collisions with D/T ions • Reduction of He content improves ITER performance 1/2D ITINT1.SAS code with Psep ≥ PL-H O.J.W.F. Kardaun NF 42 (2002) 841 V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  11. Theory Based Transport Models • WEILAND, MMM, GLF23 and IFS/PPPLtransport models • Transport driven by drift wave turbulence • Detailed treatment is somewhat different • Boundary conditionstaken from experiments or fromempirical or semi-empirical scalings • Reasonable agreement with experimental datafor plasma core V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  12. ITER Predictions by Physics Based Models Pedestal scalings (a) J G Cordey, et al 19th FEC Lyon (b) J G Cordey, et al 19th FEC, Lyon (c) M Sugihara, et al NF 40 (2002) 1743 (d) A H Kritz, et al 29th EPS D-5.001 (e) M Sugihara, et al submitted to PPCF (g)K S Shaing T H Osborne et al 19th FEC, Lyon V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  13. ITER Predictions by Physics Based Models Predictions for ITER by different models atthe same input parameters(G. Pereverzev et al. 29th EPS 2002 P-1072) V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  14. Edge Pedestal in ELMy H-mode Two-term confinement scalingsfor thermal energy W = Wcore+ Wped Edge temperature gradient limited by thermalconduction ITER: Wped = 174 MW Tped = 5.2 keV Edge gradient limited by ELMs(MHD limit): ITER: Wped= 98 MW Tped ≈ 3.0 keV J.G.Cordey et al IAEA Lyon Conf. 2002 M Sugihara et al , submitted tp PPCF 2003 V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  15. Non-Dimensional Confinement Scalings • GyroBohm like scalings have been found in experiments withELMy H-mode: BtEµ(r*)-3.15 b 0.03 (n*)-0.42in DIII-D BtEµ(r*)-2.7 b -0.05 (n*)-0.27in JET(r*= ri/a) • JET DT discharge with all dimensionless parameters,b, n*, q, R/a, k, d, etc,except r*,the same as ITER: JET #42983:r*= 4.25 10-3 JET-like ITER:r*= 1.88 10-3 ==> Q = 6 - 13 V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  16. High Performance H-Modes at High DensityDemonstrated • One of the major achievementsin recent tokamak experiments was demonstration of good confinement in H-mode at high plasma density required for ITER,i.e. H98(y,2)= 1 at n ≥ 0.85 nG • There are several ways to improve confinement at high density • Increase in plasma triangularity; gentle gas fuff • Impurity seeding • High field side pellet fueling V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  17. Good Confinement at High Density HH Energy confinement reduces with density but improves with plasma triangularitydor shaping parameter q95/qcyl H(y,2)corr = 0.46 + 1.35 ln(q95/qcyl) - 0.17 n/nG + 0.38(n/nped -1) ITER: H(y,2)corr=0.91at n/nped=1; H(y,2)corr=1.05 at n/nped=1.3 JET ITER V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  18. Power and Particle Control in ITER • B2/Eirene code: steady state divertor power loads are within the proven limits • He density at the separatrix reduces by 3-5 times due to elastic collisions of He atoms with D/T ions A S Kukushkin, H D Pacher PPCF 44 (2002) 943 V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  19. Major Instabilities in ELMy H-mode • Sawteeth • Edge localized modes (ELMs) • Neoclassical tearing modes (NTMs) • Alfven instabilities • Disruptions V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  20. EDGE LOCALIZED MODES (ELMs)

  21. H-mode Regimes with Smaller ELMs • Expected energy fluxes on the ITER divertor associated with ELMs are close to being marginal for an acceptable divertor target life time • There are alternative high confinement modes with small ELMs found at q95 > 3.6-4 and high triangularity • H-mode with ‘grassy’ or ‘minute’ ELMs in DIII-D and JT-60U • Enhanced Da (EDA) mode in Alcator C-Mod with quasi-coherent density fluctuations • Advanced H-mode with Type II ELMs in ASDEX-U • Impurity seeded H-mode in JET with reduced Type I ELMs • High density H-mode with rear small ELMs in JET • Quiescent Double Barrier (QDB) H-mode in DIII-D • ELM mitigationwith frequent pellet injection is promising V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  22. ELM Mitigation Using Pellet Injection A. Herrmann PSI 2002 ? . ELM induced energy loss is reduced in ASDEX Upgrade at sufficiently high frequency of pellet injection(P Lang, 2002) 4Hz pellet injection in ITER can reduce the energy loss per ELM to acceptable level(A Polevoi et al 19 FEC Lyon 2002) V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  23. NEOCLASSICAL TEARING MODES (NTMs)

  24. Neoclassical Tearing Modes (NTMs) • Neoclassical tearing modes (NTMs) are induced by reduction of bootstrap current inside magnetic islands • Deteriorate confinement and determine the lowest beta limit • NTMs methastable: ‘seed’ islands are required • NTM can be stabilized with localized current drive within magnetic island V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  25. Neoclassical Tearing Modes (NTMs) • Complete 3/2 NTM suppression demonstrated (AUG, DIII-D, JT-60U) with localized ECCD • Complete2/1 NTM suppression demonstrated (DIII-D) • Real-timeECCD position control demonstrated (DIII-D) V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  26. Suppression of NTMs in ITER • Extrapolation to ITER: PECCD = (30 ± 15) MW (G Giruzzi and H Zohm, ITPA MHD Meering, Naka, Feb 2002) • Early injection would enable NTM stabilizationwith PECCD< 20 MW • ITER design: PECCD = 20 MW m/n = 2/1 A Zvonkov , 2000 V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  27. DISRUPTION MITIGATION

  28. Disruption Mitigation • Mechanical loads during disruptions are within the design limits (confirmed by DINA) (M.Sugihara et al, this Conference) • Promising disruption mitigation technique • DIII-D: High-pressure noble gas jet injection (D G Whyte FEC 2002, Lyon) V. Riccardo, this Session V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  29. Noble Gas Jet Injection in ITER • Preliminary modeling: the technique is feasible for ITER • Operation space limited bymelting/ablating the first wall 2 0 1 0 8 0 (1021 m-3) ITER-98 01 234t (ms) D G Whyte 19th FEC 2002, Lyon V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  30. IMPROVED H-MODE

  31. Q=10 Scenario at Reduced Current • Regime with lower current (higher q95) would be beneficial to reduce disruption forces and for access to benign (Type II) ELM regime but requires improved confinement • Recently ASDEX Upgrade, DIII-D and JET demonstrated a possibility to obtain plasmas with improved confinement, H98(y,2) = 1.2-1.4, at q95 =3.6-4.2 (correspond to I = 12.5 - 10.5 MA in ITER) V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  32. AdvancedH-mode with Type II ELMs  18 MW / m2  6 MW / m2 outer divertor inner divertor No sawteeth q(0) ≥1 bN = 3.5 q95 = 3.6 H98(y,2) = 1.3 n = nG Dt = 40 tE Low divertor heat load (Type II ELMs) ASDEX Upgrade V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  33. INTERNAL TRANSPORT BARRIERS (ITBs)

  34. Steady-State Q≥5 Operation in ITER • Requirements • H98P(y.2) > 1.3-1.5 • High beta bN > 2.6 • High bootstrap current fraction,fBS ≥50% • Advanced Tokamak Mode • Regimes with Internal Transport Barriers (ITBs) • Weak or negative magnetic shear • Resistive wall mode stabilization V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  35. ITB Power Threshold • The target plasmas with weak or negative magnetic shearrequire lower heating powerfor ITB formation [G T Hoang et al, 29th EPS Conf. 2002] • The rarefaction of resonance surfaces at low/zero magnetic shear helps ITB formationwhile the barrier width is probably controlled by the ExB shear • JET and ASDEX-U indicate importance of rational qin the vicinity of zero magnetic shear [E Joffrin et al 19th FEC Lyon 2002] V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  36. Real-Time Control of ITBs in JET V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia 50

  37. JT-60U: ITB and Current Hole Transiently: I=2.6 MA, q95=3.3, tE=0.89 s, Qeq=1.2 HH98y,2~1.5, bN~ 1.6 ne(0) = 1020 m-3 • Current hole and ITB at strong negative shear has been sustained for ~5 s in JT60-U at I = 1.35 MA, q95=5.2, HH98y,2~1.5, bN~ 1.7 • T(r) and n(r) are flat inside the current hole V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  38. RESISTIVE WALL MODES (RWMs)

  39. Suppression of Resistive Wall Modes • DIII-D: Dynamic error field corrections by feedback control allows rotational stabilization of RWMsbN=bN(ideal wall) ~ 2bN(no-wall limit) at wrot > 2%wAlfven • DIII-D: Negative central shear plasma fBS = 65%, fnon-ind = 85%,bT ≥ 4%(E J Strait et all 19th FEC Lyon 2002) V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  40. Suppression of RWM in ITER • Extrapolation to ITER • Model developed taking account realistic vessel and coil geometry and plasma rotation (A Bondeson, next report) • Side correction coils will be used for RWM stabilization (similar to that in DIII-D) Cb = 0.8 is achievable V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  41. Requirements for Power Reactor • Analysis study suggests that it is possible to achieve most normalized plasma parameters in ITER to enable projection to fusion power reactor, i.e. demonstration of Pfus~0.7GW and simulation of Pfus ~ 1 GW (M.Shimada, this Conference, Thursday 10 July) V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  42. Requirements for Plasma Measurements • The requirements for plasma and first wall measurements on ITER are well developed and many diagnostic systems have been designed to an advanced level • Solutions to many of the difficult implementation issues that arise on a DT machine have been found, and design and R&D is in progress on outstanding issues • It is believed that the measurements necessary for the machine protection and basic plasma control can be made at the required level of accuracy etc, and also many of those now identified as necessary to support the advanced operation • There are several papers on ITER diagnostics presented in the diagnostic sessions on Thursday and Friday afternoons including an overview oral by A Costley on long pulse issues in ITER diagnostics V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  43. Summary - I • The reference plasma parameters required for inductive high-Q operation in ITER(bN= 1.8, q95 = 3, H98(y,2) = 1, n/nG = 0.85) are demonstrated on present machines • The feasibility of achieving Q ≥10 in H-mode predicted by transport model based on empirical confinement scaling is confirmed by dimensionless analysis and theory-based transport modeling • Active control of NTMs and mitigation of ELMs and disruptions may be necessary. Relevant control and mitigation techniques suggested and tested. Extrapolation to ITER needs further work V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  44. Summary - II • Requirements for ITER steady-state Q≥5 operation (bN > 2.6, H98(y,2) > 1.3, fBS > 0.5, n ~ nG)developed. Normalized parameters demonstrated in experiments • More sophisticated control schemes (i.e. current and pressure profiles) will be necessary for steady state operation. Such schemes are under development • Achievement of more demanding normalized parameters(bN > 3.6) and high fusion power, 700MW, necessary to facilitate extrapolation of plasma performance to fusion power reactor is under study and looks possible V. Mukhovatov et al., 30th EPS Conf. on Control. Fusion and Plasma Phys., July 7-11, 2003, St Petersburg, Russia

  45. LIST OF ITER IT REPORTS AT THIS CONFERENCE V. Mukhovatov Overview of ITER Physics (Wednesday, July 9) I-3.3A M. Shimada High Performance Operation in ITER (Thursday, July 10) P-3.137 M. Sugihara Examination on Plasma Behaviors during Disruptions on Existing Tokamaks and Their Extrapolations to ITER (Tuesday, July 8) P-2.139 A.S. Kukushkin Effect of Carbon Redeposition on the Divertor Performance in ITER (Thursday, July 10) P-3.195 A. Costley Long Pulse Operation in ITER: Issues for Diagnostics (Friday, July 11) O-4.1D K. Itami Study of Multiplexing Thermography for ITER Divertor Targets (Friday, July 11) P-4.62 T. Kondoh Toroidal Interferometer/Polarimeter Density Measurement System for Long Pulse Operation on ITER (Friday, July 11) P-4.64 T. Kondoh Prospects for Alpha-Particle Diagnostics by CO2 Laser Collective Thomson Scattering on ITER (Friday, July 11) P-4.65 T. Sugie Spectroscopic Measurement System for ITER Divertor Plasma: Divertor Impurity Monitor (Friday, July 11) P-4.63 C. Walker Erosion and Redeposition on Diagnostic Mirrors for ITER: First Mirror Test at JET and TEXTOR (Friday, July 11) P-4.59 C.I. Walker ITER Generic Diagnostic Components and Systems for Integration (Friday, July 11) P-4.61

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