MHD Stability and Fast Particle Confinement Where are we?

1. 6th ITPA MHD Topical Group Meeting combined withW60 IEA Workshop on Burning PlasmasSummarySession IIMHD Stability and Fast Particle Confinementchaired by A.Fasoli, CRPP-EPFL (Switzerland)

2. MHD Stability and Fast Particle ConfinementWhere are we? • Ripple effects: well understood (single particle) • Low frequency MHD • Fishbones: qualitatively understood, no problem for ITER? • kBMs: theory advanced, limited comparison with expt. • Sawteeth: still basic open questions, but ICRH period control methods work • NTMs: progress on FIR, control through sawteeth (ICRH), ECCD control, including real-time as part of general mode/disruption control • Fast particle thermalisation: Classical for T, ’s in conventional discharges, no clear results in RS, NBI ‘anomaly’? • High frequency MHD (Alfvén) • Linear stability • Drive ~OK, damping qualitatively OK for low-n’s, extreme sensitivity to parameters, especially at edge, quantitative theory/expt. discrepancy (core damping) • Nonlinear development (redistribution and losses) • First complete self-consistent scenarios modelled, strong sensitivity to assumptions, strong effect of NBI in ITER • Nonperturbative modes (EPMs) • Theory: EPMs in ITER may cause sizeable redistribution of alphas, especially in RS • Diagnostic use • MHD spectroscopy used to get info on background plasma and fast particle parameters • Possibilities for burn control: very preliminary results on isolated ‘building blocks’

3. MHD Stability and Fast Particle ConfinementWhere do we want to go? • Ripple effects: quantify the influence of ITER test blanket module • Low frequency MHD • Sawteeth: control methods with fast ions, effect on NTM island size • NTMs: triggering, optimisation of ECCD control (injection geometry, cw vs modulated) • Fast particle thermalisation • NBI off-axis current drive ‘anomaly’, understand interaction of drift turbulence with fast ions • High frequency MHD (Alfvén) • Linear stability • Which modes are most unstable, in which ITER scenarios? Parameters that control stability? • Nonlinear development (redistribution and losses) • Which modes are most dangerous for alpha transport? Limits to ITER operational scenarios? • Self-consistent fast particle profile in ITER? • Nonperturbative modes (EPMs) • EPM effects on ’s in ITER • Diagnostic use • Reliable meas. of q_min(r,t) in RS, info on D-T ratio and fast ion phase space distribution • Possibilities for burn control • Establish methods to detect changes in and affect the fast particle pressure profile

4. MHD Stability and Fast Particle ConfinementHow do we get there? • Ripple effects: modelling and dedicated experiments (JET, JT60U) • Low frequency MHD • Sawteeth: test ICRH control methods, use realistic theoretical tools • NTMs: multi-machine ECCD experiments and theory comparisons • Fast particle thermalisation: more (D-)T expt. in RS, specific expts. and theory on interaction between drift turbulence and fast ions, develop core diagnostic tools • High frequency MHD (Alfvén) • Linear stability: drive and damping database with active MHD for intermediate n’s • Systematic expt.-theory comparison in ITER relevant n-range • Measure radial and poloidal structure, perform theory sensitivity analysis, benchmark codes • Nonlinear development (redistribution and losses) • Obtain data on fast ion redistribution and losses, quantitative comparison with theory • identify scenarios with large modes (and overlapping) and possibly to excite large amplitude modes with external antennas • Nonperturbative modes (EPMs) • Identify scenarios with EPMs, measure their effects in present experiments • Real geometry to be included in codes, compare with expt. • Diagnostic use: compare info from MHD spectroscopy with ‘conventional’ diagnostics • Possibilities for burn control • Demonstrate ‘building blocks’: real time AE stability control, ext. power (e.g. ICRH) actuator