Addressing ITER High Priority Topics - Transport and Confinement -

1. Addressing ITER High Priority Topics- Transport and Confinement - S.M. Kaye Chair, T&C ITPA Group IEA Joint Expt Meeting MIT, Dec. 11-13, 2008

2. Plan based on Proposed ITER R&D Program for ITER Transport and Confinement • Focused on High Priority items • Near-term (2 to 3 year horizon) • Did not attempt to address all High Priority items • Want to ensure that quantitative answers can be given on some • Chose areas for which Group felt they could commit the most resources and for which resolution could be achieved • Some progress already achieved in some areas • Many topics in the T&C Physics Program document more relevant to other ITPA groups (will indicate which and where) • Items will be addressed through Joint Activities (JEXs are a subset of these; includes, e.g., modeling) • Recommend reclassifying all as “JACs” (Joint Activities) • Has real implications for commitment of resources by various parties

3. High Priority Items I • Transport and confinement during transient phases • Develop models/scalings for ramp-up/down phases (OH, L-, H-) • Develop models of confinement transients during stationary phase (L-H, H-L, ITBs, etc) • Access to high confinement regimes during steady-state and ramp-up/down H, D, and DT phases • Determine power required for L-H transition and its minimization • Determine power required for steady Type III H-mode operation • Determine power required for H~1 Type I H-mode operation • Determine power required for H access during plasma current ramp-up/down with similar requirements to ITER (dIp/dt, shape(t), etc.) • Isotope mass and species scaling of L-H threshold power for Type III and H~1 Type I operation

4. High Priority Items II • Characterization of proposed schemes for ELM control, compatibility with scenario requirements • Determine edge magnetic field perturbation characteristics for ELM control and integration with ITER high fusion gain scenarios • Determine requirements for ELM control by pellet pacing and integration with ITER high fusion gain scenarios • This will be addressed by the Pedestal group, not the T&C group • Determination of ripple effects on ITER plasma performance and on fast particle confinement • Some of this will be addressed by T&C, most by Pedestal and Energetic Particles

5. High Priority Items III • Particle transport and fueling in ITER reference scenarios • Demonstrate physics basis for core plasma fueling in ITER (pellets) • Develop and validate models for pellet ablation and particle transport/loss of pellet fueling efficiency • High priority items will be addressed through Joint Activities (experiments, analysis, modeling) and by individual efforts • Progress in some of these areas has already been made

6. Transport and confinement during transient phases • Develop models/scalings for ramp-up/down phases (OH, L-, H-) • In conjunction with IOS group for core transport • Focus is on electron transport since Te governs current profile evolution • Work plan • Validate a number of transport models (physics and “ad-hoc”) during ramp-up phase initially • Choose several representative discharges, including ITER demonstration discharges, from JET, DIII-D, Asdex-U and C-Mod • Must be well diagnosed • Use profile database as repository • Choose four time points during ramp-up for time slice benchmarking of models • Also perform time-evolving benchmark • Define density profile evolution initially (no prediction), Zeff, etc.

7. Ip • Specific models to be tested would include • Coppi-Tang • TGLF, GLF23 • Bourdelle quasi-linear ITG/TEM approximations • ……. • Tools and modelers • Kinsey • Bourdelle • EU Modeling (JETTO, Cronos) • PTRANSP (Budny, Lehigh?) • Time frame for completion of ramp-up: 2009 • Could benefit from an infusion of resources (i.e., we could use some help)! • Benchmarking ramp-down requires guidance on scenario Time

8. Kinsey - GA Bourdelle - CEA Imbeaux et al - EFDA

9. Develop models of confinement transients during stationary phase (L-H, H-L, ITBs, etc) • Work plan • Multi-scale model addressing ITB formation and collapse being developed by M. Yagi (Kyushu University) • Transport driven by ITG turbulence, assumes negative magnetic shear key to formation • Includes momentum source to investigate effect of toroidal flows and flow shear on sustainability • ITB collapse with growth of 4/3 mode near the qmin location • Time scale for completion: ongoing; results in 2009-2010 and beyond Yagi, Kyushu U.

10. Region of maximum torque from applied n=3 ci/ci,neo=3.9 Decreasing shear ci/ci,neo=2.3 ci/ci,neo=1.2 • Joint experiments will address ITB formation • TC-5: Investigate effect of rotation and rotation shear on high performance operation; hybrid, AT, ITBs, etc. • TP8.3 (closed out): ITB similarity expts between JET and JT-60U • Torque scan in JT60-U, ripple scan in JET • Understand effect of q-profile • q0~2 just before formation • Analysis underway: time scale for completion ~ 1 year Kaye (IAEA) - NSTX Sakamoto - JAEA

11. ~0.8nGr ne L-H ~0.4nGr PADD Access to high confinement regimes during steady-state and ramp-up/down H, D, and DT phases(L-H threshold studies) • Work plan – three JEXs, database analysis, edge turbulence studies dedicated to addressing the key issues of L-H threshold • Work being carried out in conjunction with Pedestal group • TC-2: Hysteresis and access to H-mode with H~1 • Operate devices close to the threshold in ITER like shape • Characterize H-mode properties • Density: low – ramp – high (~0.4-0.8 nGr) • Power: Maintain at 1.0 – 1.2 x Pth (low density)

12. Some studies to determine H98y,2 just above threshold power have begun, and are tied into the hysteresis studies • Lowest enhancement seen in Type III scenario • Experiments need to be performed • JET, AUG, TCV, NSTX, MAST • Expect results in 2009, compeleted in 2010 Ryter - AUG

13. TC3: Scaling of the low density limit to the H-mode threshold in H&D plasmas • C-Mod, AUG and JFT-2M data suggest nth,min increases linearly with increasing BT, but JET and JT-60U show weaker trend • Additional work to be performed on JET, AUG, C-Mode and TCV in 2009 • Focus on Ip, BT scaling of minimum density ITPA Database 2007-08 RF C-Mod 2007-08 OH C-Mod Y. Martin, 2008

14. TC4: Species dependence of L-H threshold • Experiments in He and H performed on AUG and DIII-D respectively • Additional experiments to be done in 2009 on DIII-D, AUG, JET, NSTX, and JT-60U will provide data from previous experiments • Threshold and confinement characteristics • Where possible, studies to understand effect of rotation on L-H threshold will also be performed (using RMP coils) • Proxy to study error field, ripple effects • Multi-machine database focus on edge parameters, profiles (J. Hughes) Ryter - AUG Gohil – DIII-D

15. Determination of ripple effects on ITER plasma performance and on fast particle confinement • At present, most of the experiments in this area have been done in JET • No plans at present by other devices to explore this area • The joint experiment on ITBs in JET and JT-60U (TP8.3) has been completed • Part of the analysis will be to assess the effect of ripple on the performance of these ITB plasmas • Analysis to be done within ~ 1 year

16. Particle transport and fueling in ITER reference scenarios • Development and validation of models for pellet ablation and transport/loss • MAST performing HFS pellet fueling experiments to test ITER assumptions (Polevoi model) • All particles deposited inside of pedestal • Particle losses do not depend on fueling pellet • Find both assumptions can be violated • Significant number of particles deposited between Q=0.95 and 1, with or without inward drift (both expt and modeling) • Edge properties can be altered dramatically by fueling pellet • Induce L-H transition, ELM-triggering in H-mode, modify ELM mitigation with RMP, particle loss depends on pellet deposition radius • Quantify results with respect to models assumed for ITER fueling • Modify assumptions of model for development of fueling scenario • TC-11: He profiles and transport (new Joint Experiment) • Measure and understand He transport in hybrid, AT and ITB plasmas • JET, DIII-D, AUG, C-Mod, TCV, Tore-Supra, MAST, JT-60U (?) • ~ 2 year time scale