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ITPA TG – MHD Stability: Work Plan 2009

ITPA TG – MHD Stability: Work Plan 2009. A. Sen, E. Strait , Y. Gribov. 7th IEA Large Tokamak Workshop (W69) on “Implementation of the ITPA Coordinated Research Recommendations”. December 11-13, 2008 MIT Plasma Science and Fusion Center Cambridge, MA, U.S.A.

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ITPA TG – MHD Stability: Work Plan 2009

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  1. ITPA TG – MHD Stability: Work Plan 2009 A. Sen, E. Strait , Y. Gribov 7th IEA Large Tokamak Workshop (W69) on “Implementation of the ITPA Coordinated Research Recommendations” December 11-13, 2008 MIT Plasma Science and Fusion Center Cambridge, MA, U.S.A.

  2. Focus of 2009 work plan for MHD TG • ITER Urgent R&D Needs • Disruptions (control, mitigation, loads) – major theme (first topic in David’s viewgraphs on High Priority ITER R&D needs) • Plasma control • Vertical Stabilization • NTM stabilization • Sawtooth control • RWM control • Error Field control • Implementation • Joint experiments (MDC1,2,4,5,8,12-14,15-17) • Theory/Modeling } Scenario Development

  3. Disruptions • Electromagnetic loads – vertical & horizontal – due to halo currents, disruptions and VDEs • Improve 2D (DINA, TSC) and 3D halo current models • Extend ITPA disruption database: focus on halo currents • Runaway electrons • Diagnostics for generation, confinement, loss • Physics basis for runaway suppression by gas injection, MHD activity, or RMP • Requirements for ITER’s disruption mitigation system • Experiments and modeling (NIMROD, SOLPS, …) • Gas injection • Alternate delivery methods such as pellet injection • Disruption prevention • ECRH heating of precursor islands • Feedback stabilization of NTMs, RWMs or forced rotation of precursors

  4. Disruptions – EM loads etc. • MDC-15 Disruption database development • AUG, C-Mod, DIII-D, JET, JT-60U, MAST, NSTX, TCV • Develop empirical scalings for disruption parameters • Validate disruption models over a range of machine sizes and operating regimes • Extrapolate disruption parameters to ITER • Provide confidence in design limits (EM forces, heat deposition) • Identify range of outcomes, worst-case limits • Provide input to detection and mitigation scenarios • extend database to include halo currents and related quantities, including halo current amplitude, TPF, vertical displacement of the plasma, and EM forces on the vacuum vessel. • G. Pautasso (AUG), R. Granetz (C-Mod), J. Wesley (DIII-D), P. deVries (JET), Y. Kawano (JT-60U), R. Martin (MAST), S. Sabbagh (NSTX), J. Lister (TCV)

  5. Disruptions – Runaway electrons • MDC-16 Runaway electron generation, confinement, and loss • Characterize runaway electron generation and confinement: energy spectrum, time scale, seed generation mechanisms, conditions for generation during a VDE. • Is runaway level related to discharge shaping ? • NIMROD runs using a C-Mod low-elongation discharge • Low elongation equilibria (AUG, DIII-D, JET) with LH-driven runaway electrons (C-Mod) • Provide physics basis for runaway suppression and mitigation methods: GI (AUG, C-Mod, DIII-D, Textor ), Magnetic perturbations (C-Mod, DIII-D, TEXTOR ), position control of RE plasma (TEXTOR) • G. Pautasso (ASDEX-Upgrade), R. Granetz (C-Mod), J. Wesley (DIII-D), B. Esposito (FTU), J. Martin-Solis (JET), Y. Kawano (JT-60U), M. Lehnen (TEXTOR), F. Saint-Laurent (Tore Supra),

  6. Disruptions - Mitigation • MDC-1 Disruption mitigation by massive gas jets (also known as DSOL-11 – primary responsibility with MHD Stab. TG) • goal is to determine the optimal disruption mitigation scheme for ITER • Understand and improveefficiency of MGI (C-Mod, DIII-D & AUG) • Pellet injection expts on DIII-D • Modeling (NIMRAD, SOLPS, ….) • G. Pautasso (AUG), R. Granetz (C-Mod), E. Hollmann (DIII-D), B. Esposito (FTU), M. Lehnen (JET), S. Lisgo (MAST), M. Lehnen (TEXTOR), G. Martin (Tore Supra),

  7. Disruptions - Avoidance • MDC-17 Active disruption avoidance • Recent FTU and AUG L-mode expts have shown that disruptions can be avoided or delayed by direct heating of magnetic islands with ECRH • Quantify the requirements for postponement of disruptions with ECRH. • stabilization of disruption precursors using tangential NBI & other methods • Extend technique to H mode plasmas • M. Maraschek(AUG), R. Granetz (C-Mod), R. La Haye (DIII-D), B. Esposito (FTU), V. Riccardo (JET) • AUG, C-Mod, DIII-D, FTU, JET, JT-60U, MAST, NSTX, TCV

  8. Plasma Control Issues - Vertical Stability • Safe operation limit: ZMAX /a > 5% • Confirm design of in-vessel coils • Characterize plasma disturbances, e.g. ELMs • Effects of noise, disturbances on ITER controllability limits • Up-gradation of VS1 & VS2 as a backup? • Scaling with parameters other than li ,  … • Joint Expt (MDC-13): DIII-D, C-Mod, JET, NSTX • Refine past exptal findings on controllable vertical displacements and compare with model predictions • D Humphreys (DIII-D), I Hutchinson (C-MOD), F Sartori (JET), D Gates (NSTX), W Treutterer (AUG), J Lister (TCV)

  9. Plasma Control Issues - NTM Stabilization • Requirements for ECCD detection and stabilization • Determine diagnostic requirements for island detection • Confirm power requirements • Launcher capability for planned operating scenarios • Rotation effects • On threshold N – strong evidence from DIII-D, JET, NSTX • Rotation vs rotation shear, direction of rotation • Theoretical understanding lacking • Scaling of NTM limiting  with other parameters • Suppression through sawtooth control

  10. NTM Stabilization – aspect ratio dependence • MDC-4 Neoclassical tearing mode physics - aspect ratio comparison • 2005/2006 comparison expts AUG/MAST and NSTX/DIII-D • Complete MASTAUG NTM comparison experiments on onset and critical-b for 2/1 NTMs • M Maraschek (AUG), D Howell (MAST), S. Gerhardt (NSTX), R. LaHaye (DIII-D)

  11. NTM suppression through sawtooth control • MDC-5 Comparison of sawtooth control methods for neoclassical tearing mode suppression • improve NTM b-limits by controlling the sawtooth seed instability-may be an important technique for ITER • ECCD (extend to H mode), ICRF, ICCD • Plans: • JET – ICCD at higher  • DIII-D - ECCD sawtooth control in H-mode at high  • FTU plans to control sawtooth frequency using ECRH • HL2A a steerable mirror - angle of injection in the toroidal direction. • R Pinsker, R La Haye (DIII-D), H. Zohm (AUG), S. Coda (JET), S. Gerhardt (NSTX), T Goodman (TCV), Yi Liu (HL2A), S Wukitch (C-Mod), F Gandini (FTU), JT-60U (A Isayama)

  12. NTM Stabilization using current drive • MDC-8 Current drive prevention/stabilization of NTMs • R Buttery (JET), A Isayama (JT-60U), M Maraschek, H Zohm (AUG), R La Haye (DIII-D), S. Cirant (FTU), E Westerhof (TEXTOR), O Sauter (TCV) • Modulated ECCD stabilization of 2/1, 3/2 in the hybrid scenario and simultaneous control of the 4/3 and 3/2 NTMs. (DIII-D) • Use LH power (4 MW) to control 3/2 NTM (JET) • Overall aim is to provide a range of data to benchmark the Rutherford equation for NTM evolution to validate predicted requirements on ECCD power, alignment, and current drive width in ITER.

  13. NTM Stabilization – rotation effects • MDC-14 Rotation effects on NTMs • R Granetz (C-Mod), R Buttery(JET), M Maraschek (JET/AUG), R La Haye (DIII-D), S Gerhardt (NSTX), A Isayama (JT-60U), K Gibson (MAST), F Waelbroeck (theory) • 2/1 NTM bN limit for the hybrid scenario (DIII-D) • difference between balanced beam and genuine torque-free operation • Rationalize theoretical efforts • Flow and flow shear effects? • Stability changes due to /or inner layer dynamics? • Error field sensitivity of medium bN low rotation plasmas • Scaling with bulk plasma parameters • Effect of TBMs on NTM threshold – simulation • Effect of q profile and fast particles on NTMs

  14. RWM Control • Requirements for control coils and their power supplies • Current, voltage, frequency, toroidal mode requirements for RWM stabilization using • ELM control coils • External EFC coils • Effects of noise and plasma disturbances on the control system • Relook at RWM stability thresholds and destabilization mechanisms(critical velocity concept may not be adequate) • cross-machine comparison of RWM onsets and related MHD activities that may act as triggers • ELMS or fishbones, • EWM • RWM to kink • Identify possible nonlinear destabilzation mechanism • Continue benchmarking of RWM feedback codes • RFA expts and validation of theoretical models

  15. RWM Control (continued) • MDC-2 Joint experiments on resistive wall mode physics • H Reimerdes, A Garofalo (DIII-D), S D Pinches (JET), R Koslowski (TEXTOR), G Matsunaga (JT-60U), S Sabbagh (NSTX), M Gryaznevich (MAST),Y Liu (MARS-F code) • Cross-machine comparison of RFA • establish validity and relevant parameter range for various models (e.g. IPEC, MARS-F). • address the bN dependence of RFA • benchmark “perturbed equilibrium” calculations with IPEC and MARS-F

  16. Error Field Control • Error Field Correction: design of EFC methods • Criteria for EF tolerance in all operating scenarios • EFC methods for ITER: vacuum meas., plasma response • Effects of ferromagnetic steel in Test Blanket Modules: design of correction coils • Potential effects of TBM fields on many aspects of operation, including equilibrium reconstruction • Modeling needed to quantify these effects • Simulate TBM fields in existing devices? • Non-resonant Magnetic Braking • n=1,2,3 external magnetic perturbations • Validation of neoclassical toroidal viscosity models

  17. Error Field Control (continued) • MDC-12 Non-resonant Magnetic Braking • S Wolfe (C-Mod),T Hender (JET), D Howell, M Gryaznevich (MAST), M Schaffer and A Garofalo (DIII-D), R Koslowski (Textor), S Sabbagh (NSTX) • compare the magnetic braking from externally applied dominantly n=2 or 3 error fields and also examine the effects of non-resonant n=1 fields. • Carry out validation of various NTV models by suitable comparison with experimental data

  18. Joint Experiments Continuing MDC-1 Disruption mitigation by massive gas jets MDC-2 Joint experiments on resistive wall mode physics MDC-3 NTM physics (incl. error field effects) Closed (2008) MDC-4 NTM physics - aspect ratio comparison MDC-5 Sawtooth control methods for NTM suppression MDC-8 Current drive prevention/stabilisation of NTMs MDC-12 Non-resonant magnetic braking MDC-13 Vertical stability physics and performance limits MDC-14 Rotation effects on NTMs (+ remainder of MDC-3) New (proposed) MDC-15 Disruption database development MDC-16 Runaway electron generation, confinement, and loss MDC-17 Physics-based disruption avoidance [MDC-10 and MDC-11 transferred to Energetic Particles group]

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