M9: Integrated Plasma Scenario Experiments

1. M9: Integrated Plasma Scenario Experiments Clive Challis & Michele Romanelli on behalf of the contributors to the MAST IPS programme CCFE is the fusion research arm of the United Kingdom Atomic Energy Authority

2. M9 Headlines • ELM control with 3D magnetic perturbations • Evolution and stability of the edge pedestal • Role of ion-scale turbulence in core transport • Development of integrated scenarios for the MAST upgrade • Development and benchmarking of edge modelling tools in benefit of the divertor upgrade • Fast-ion transport to guide profile and heating optimisations

3. Proposals Process • Proposals considered: • 17 through proposal webpage • 5 transferred to Fast Particle Physics Programme Area • 2 transferred from Stability Programme Area • 3 raised during Integrated Plasma Scenarios meetings • =17 proposals requesting ~437 shots • Amalgamation and prioritisation led to: • 9experiments requiring227shots • Plus 80 shots for coordinated development of plasma scenarios required for M9 experiments for all Programme Areas

4. Main Experiments *includes external collaboration

5. Parasitic, Back-up & Dropped *includes external collaboration

6. M9-IPS-001: Prepare M9 Scenarios • Background • Experimenters often carry scenario development overhead necessary for their scientific investigations • Aim • Coordinate development of generic plasma scenarios required for M9 experiments in all Programme Areas • Strategy • Collect scenario requirements for M9 experiments through Programme Leaders • Re-establish or develop plasma scenarios early in M9 • Priority for scenarios required for multiple experiments • Opportunity for parasitic data (e.g. M8-IPS-011/13) • Specific requirements • Good machine conditions, typically 1-2 beams

7. M9-IPS-002: Avoid FI Redistribution neutron camera profiles low density plasma with off-axis beams strong n=1 MHD &FI redistribution 3MW 1.5MW 3MW high density plasma with off-axis beams weak n=1 MHD &FI redistribution 1.5MW • Background • Fast ion redistribution observed with high power beams • Indication that responsible MHD avoided at high density MHD spectrograms n=1 IP=600kA weakn=1 IP=800kA impact radius (m) time (s)

8. M9-IPS-002: Avoid FI Redistribution • Background • Redistribution correlates with pfast & n=1 MHD • Guides MAST-U scenario design & beam optimisation • Aim • Determine domain to avoid FI redistribution in density & q0 • Measure beam driven current parasitically • Strategy • Scan density & q0 in L-mode with on-axis beams • Neutron camera scans & FIDA settings for M8-FPP-007 • Incorporate M8-FPP-005/6 to study effects of: • TAE avalanches; fishbones; long lived mode • Specific requirements • DI scenario, neutron camera, FIDA, MSE, 2-beams • Collaborations: Uppsala U.; PPPL

9. M9-IPS-003: Measure Resistivity • Background • Simulations of q-profile during current ramp-up do not reproduce measurements • Similar observation on JET, but ‘stationary’ q-profile reproduced[see Jenkins et al EPS 2010] From: Keeling et al EPS 2011

10. M9-IPS-003: Measure Resistivity • Background • q-profile simulations fail during current ramp-up • MAST-U scenario predictions rely on ‘stationary’ q-profile modelling • Aim • Measure ‘stationary’ q-profile to test simulations • Strategy • Develop Ohmic plasma as close to ‘stationary’ as possible • 400-500kA for high q to minimise impact of sawteeth • vary density to test collitionality dependence of resistivity • Measure q-profile shape for comparison with modelling • Specific requirements • MSE beam, TS profiles, Zeff profile

11. M9-IPS-004: Control HFS Gas • Background • Controllable HFS (cHFS) gas valve commissioned in M8 • on/off functionality only • not controlled by PCS • HFS gas envisaged as primary fuelling source for MAST-U • Aim • Develop gas flow rate control using cHFS • Strategy • Establish cHFS control by PCS • Demonstrate cHFS flow rate control using piezo to drive valve • Specific requirements • PCS control for cHFS valve, piezo operation enabled (avoid periods when mechanical operation required)

12. M9-IPS-005: Access Early H-mode • Background • MAST-U operation envisaged at low li & high  • Early H-mode needed to maintain transient low li & high  • Early H-mode difficult with large edge-j and low density

13. M9-IPS-005: Access Early H-mode • Background • Early H-mode difficult with large edge-j and low density • Aim • Develop MAST scenario with early H-mode transition • Strategy • Investigate access to early H-mode by optimising: • current ramp rate (controls edge-j via Vloop) • plasma density (affects PL-H threshold) • early heating power (risks IREs) • plasma shape (e.g. X-point position & wall clearance) • Parasitic data for study of H-mode ne & Te profiles with q0>>1 (M8-IPS-013 & M8-IPS-014) • Specific requirements • Good machine conditions, 2-beams

14. M9-IPS-006: n=2 Error Field Correction • Background • MAST n=1 & n=2 error fields measured using Hall probe • Dynamic n=1 error field correction developed in M8 • Aim • Determine n=2 error field using lower ELM coils and apply correction to investigate effect on H-mode plasma • Strategy • Perform n=1 & n=2 error field measurements using density ramp-down method for different IP4/IP5 • Determine error field correction algorithm based on IP4 & IP5 and compare effect on H-modes with correction based on Hall probe data (e.g. effect on IREs – M8-IPS-011) • Specific requirements • Lower ELM coils in n=2 mode

15. M9-IPS-007/8: EBW Start-up • Background • Non-inductive start-up important issue for STs • 33kA achieved without solenoid flux using EBW in MAST From: Shevchenko et al NF 50 (2010) 022004

16. M9-IPS-007/8: EBW Start-up • Background • 33kA achieved without solenoid flux using EBW in MAST • Aim • Extend EBW start-up with higher injected power • Make transition from EBW start-up to NBI heated plasma • Strategy • Use increased EBW power • Optimise: gas; Bvertical; EBW waveform; plasma position • Investigate: flux surface topology; current dependencies • Use limited solenoid assist to trigger faster current rise • Specific requirements • Good machine conditions, 1 NB PS for EBW; 2 expt blocks • Potential collaborations: ORNL; PPPL; Tokyo U.; Kyoto U.; Ioffe I.

17. M9-IPS-009: Real-Time Control • Background • 3-point plasma shape control developed using rtEFIT measured X-pt height requested P2 controldisabledduringpolaritychange P2 current

18. M9-IPS-009: Real-Time Control • Background • 3-point plasma shape control developed using rtEFIT • Real-time control required for MAST-U with super-X • Aim • Develop real-time control of divertor strike point position • Establish routine shape control during current flat-top for example M9 scenarios • Strategy • Establish and test control for lower-outer strike point • Select 1 or 2 M9 scenarios, test real-time control in typical conditions, and then release PCS for routine use • Evaluate performance parasitically (M8-IPS-012) • Specific requirements • Small groups of shots (3-4) at regular intervals

19. M9-IPS-010: JINTRAC validation • Background • HFS gas injection in DND plasma can produce localised emission in SOL that moves preferentially downwards & poloidally asymmetric plasma density inside the LCFS asymmetric density density temp 50ms HFS gas feature

20. M9-IPS-010: JINTRAC validation • Background • HFS gas injection in DND plasma can produce localised emission in SOL that moves preferentially downwards & poloidally asymmetric plasma density inside the LCFS • Aim • Reproduce localised HFS gas effects in SND plasma to allow modelling with JINTRAC/EDGE2D • Strategy • Apply HFS gas to LSND plasma with small plasma-wall gap at gas injection point • If DND features reproduced, bid for further shots to characterise phenomenon (e.g. q-variation, NBI heating) • Specific requirements • HFS gas injection, Ohmic plasma

21. Main Experiments *includes external collaboration