1. 1 st ITPA T&C Meeting, Milan, 20-22 October 2008 - WAHPage 1 ITER R&D Needs for Transport & Confinement W.A. Houlberg ITER Organization 1st ITPA Transport & Confinement TG Meeting 20-22 October 2008 Milan, Italy

2. 1st ITPA T&C Meeting, Milan, 20-22 October 2008 - WAH Page 2 ITER R&D Needs – Description & Implementation The ITER STAC (Science & Technology Advisory Committee) requested the IO (ITER Organization) to propose a programme to address ITER R&D needs: –Written descriptions and resource estimates presented to STAC this week –Here we cover Transport & Confinement Physics relevant to ITPA T&C TG (some overlap with other TGs, e.g. regarding ELMs and operating scenarios) Implementation is expected through various channels: –ITPA (the hope is for ITPA to co-ordinate much of the basic R&D) –Voluntary Physics R&D (voluntary in the sense that ITER doesn’t pay) –Design Tasks –Visiting Scientists to IO Guidance to ITPA T&C TG in tackling needs: –Appropriate people, ideas, resources? Joint effort with other TGs?

3. 1st ITPA T&C Meeting, Milan, 20-22 October 2008 - WAH Page 3 Near-Term Activities – 2009-2011 Near-term activities are defined by their direct influence on: –Procurement agreements (PAs) –Foreseen operation of ITER and/or its reference operating scenarios ITER systems which could be influenced by this R&D are: –Plasma magnetic control schemes and requirements (detailed specifications to be developed from 2010) –Final criteria for optimisation of the ferromagnetic inserts for TF ripple correction (end of 2009 – beginning of 2010) –Pellet injection system and gas introduction systems (PAs to be signed in May-July 2010) –First wall and blanket modules (PAs to be signed in July 2011) –In-vessel coils for ELM control and vertical position control (PAs tentatively scheduled for signature in September 2010)

4. 1st ITPA T&C Meeting, Milan, 20-22 October 2008 - WAH Page 4 Short-Term Activities – Transport and confinement Transport and confinement during transient phases Access to high confinement regimes Schemes for active ELM control Ripple effects Particle transport and fuelling

5. 1st ITPA T&C Meeting, Milan, 20-22 October 2008 - WAH Page 5 Transport and Confinement During Transient Phases – Impacts control requirements, e.g. the PF and heating systems Development of transport models/scalings for ITER ramp-up/down phases (Ohmic, L-mode and H-mode) –Ramp-up (and ramp-down) phases provide the operational transition between Ohmic and strong auxiliary heating conditions (and visa versa) –Particularly address electron thermal transport since it determines the electron temperature profile that governs current profile evolution Development of transport models/scalings for confinement transients during stationary phases of the discharges –L-H and H-L transitions –Formation and collapse of internal transport barriers –Collapses of peaked density profile regimes

6. 1st ITPA T&C Meeting, Milan, 20-22 October 2008 - WAH Page 6 Access to High Confinement Regimes – During steady/state and ramp-up/down H, D and DT phases Under ITER-like plasma conditions (high , low and high n e /n GW, low plasma-main wall interactions, e.g. distance between separatrix/wall ~ 2 n L-mode, etc), determine: –Power for H-mode threshold –Power for steady (  t ≥ 10  E ) Type III H-mode –Power for steady (  t ≥ 10  E ) H 98 = 1 H-mode (Type I ELMy H-mode, EDA, etc) –Power for H-mode access during plasma current ramp-up/down (i.e., L-H and H-L hysteresis under non-steady conditions) –Isotope mass and species scaling (H and He plasmas) of the above In all cases, develop strategies for minimisation of power to access these regimes

7. 1st ITPA T&C Meeting, Milan, 20-22 October 2008 - WAH Page 7 Schemes for Active ELM Control – Compatibility with scenario requirements The ITPA T&C TG should focus on the underlying transport in the edge between (or in the absence of) ELMs Establish a physics basis for ELM control by edge magnetic field perturbations: –Dependence on edge collisionality and/or density –Plasma response: magnetic field screening, plasma rotation/rotation shear, influence on pedestal and/or total plasma b –Influence of the magnetic field spectrum on the degree of ELM control/suppression: dependence on edge q, plasma shape, resonant versus non resonant spectra, etc –Effect of edge magnetic perturbation on edge energy and particle transport –Effect on plasma rotation/rotational shear and core confinement

8. 1st ITPA T&C Meeting, Milan, 20-22 October 2008 - WAH Page 8 Ripple Effects – Transport is possibly related to physics of ELM suppression Determine physics mechanisms of toroidally periodic TF ripple leading to: –Decrease of thermal energy and plasma density –Changes in plasma rotation –Examine dependencies on plasma dimensional and dimensionless parameters Investigate similarities with ELM control experiments by edge magnetic perturbations –Dedicated experiments with systematic variation of TF ripple, plasma shape/shear and plasma  (which affects the edge magnetic field structure) Experimental studies should be accompanied with a dedicated modelling effort to: –Evaluate changes in plasma energy, momentum and particle transport –Develop physics models to describe these changes and validate them

9. 1st ITPA T&C Meeting, Milan, 20-22 October 2008 - WAH Page 9 Particle Transport and Fuelling – Physics basis for core plasma fuelling in ITER The effectiveness of plasma fuelling by pellets that are ablated in the plasma periphery needs to be addressed: –Additional losses caused by triggering of ELMs –Enhanced particle losses from steep density gradients following the pellet ablation caused by shallow deposition –Drift effect as a function of launch location –The effect of a particle pinch on required fuelling depth Experiments should: –Match the pellet ablation profile as close as possible to that expected in ITER –Address the role of dimensional and dimensionless plasma parameters expected to influence pellet transport dynamics and core particle transport Develop and validate models for pellet ablation and transport/loss

10. 1st ITPA T&C Meeting, Milan, 20-22 October 2008 - WAH Page 10 Coordination with IOS and PEP TGs Focus of the Transport and Confinement TG should be to characterize the underlying transport processes: –Between ELMs –During transients as well as steady-state conditions –Influence of non-axisymmetry –Particle, energy, momentum transport –Bifurcations phenomena –Continuous treatment from core to separatrix The Integrated Operation Scenario TG applies the recommended models together validated source models to evaluation of scenarios The PEP TG examines conditions for and characteristics of ELMs