6 th ITPA MHD Topical Group Meeting combined with W60 IEA Workshop on Burning Plasmas Session II MHD Stability and Fast Particle Confinement General scope.

6th ITPA MHD Topical Group Meeting combined with

W60 IEA Workshop on Burning PlasmasSession II

MHD Stability and Fast Particle Confinement

• General scope of the meeting – A major goal of this workshop on "Burning Plasma Physics

and Simulations" is to provide a road map for burning plasma research

– After the workshop we would like to have a short paper, outlining what our present knowledge is and where the gaps in our knowledge are ("where are we"), what we want to achieve ("where do we want to go"), and how we want to achieve this ("how do we get there")

Progress in key physics areas is leading to next step burning plasma experiment

Burning plasma

Wave-particle interaction

Turbulence and transport

Plasma /wall interaction

Macro- stability

Burning plasma ’s

’s

’s

’s’s’s

Wave-particle interaction

Turbulence and transport

Plasma /wall interaction

Macro- stability

But the essence of burning plasma physics is the coupling between different elements

Can we progress on individual ‘building blocks’ and possible couplings in weakly self-heated plasmas, with fast particles

produced by additional heating, before real BPX?

MHD Stability and Fast Particle Confinement

• Ripple effects• Low frequency MHD

– fishbones, kBMs– Sawteeth and NTMs

• Fast particle thermalisation• High frequency MHD (Alfvén)

– Linear stability – Nonlinear development (redistribution and losses)– Nonperturbative modes (EPMs)– Diagnostic use– Possibilities for burn control

Ripple effects– Ripple losses in ITER?

• Relatively well understood– Optimization of ferritic inserts in ITER to reduce ripple alpha

losses in reversed shear configurations by more than one order of magnitude

• Not an issue for ITER?

Low frequency MHD and fast particles• Interaction of fast ions with low frequency MHD

– Fishbones: nonlinear modeling in qualitative agreement with experiments

– Linear theory of kBMs interchange modes well advanced

• Neoclassical tearing modes– Questions being addressed

• Mechanisms for seed island formation, mode coupling in NTM triggering

• Island size after sawtooth crash (effect of -stabilised sawteeth)– Sawtooth stabilisation by NBI– Quantitative effect of sawteeth on distribution

• Fast ion motion with NTMs (Hamamatsu)• Robust control method for (2,1) mode (Strait)• ECCD for NTM control (Modulated or continuous) (Guenter)

Fast particle thermalisation

Too low current

Current profile not apt to confine ’s

V.G.Kiptily et al.,

PRL 93, p.115001 (2004)

• Trace T experiments -ray spectroscopy

( on Be) at T blipdirect observation of

collisional slowing down in the absence of instabilities

• Interaction between drift turbulence and fast ions: an open question

• Is slowing down classical?– Large effort to develop methods to simulate fusion ’s in

plasmas without significant fusion reactivity fast and Rfast ITER

• vpart/vA ITER

• But slowing down time/E >> ITER and *fast >> ITER

At the core of burning plasma physicsEffect of collective instabilities on self-heating

thermalisation by collisions

Tion P

Tel

eei

Collective instabilities

plossesIf instabilities are excited resonantly by ’s and reach large amplitude

redistribution / losses

effect on fusion Q

wall damage

High frequency MHD and fast particles Linear stability

• Most unstable fast ion driven modes in ITER scenarios?• Parameters that control mode stability?

– Large amounts of data on instability thresholds, all n’s (anisotropic fast ion distribution)– Experimental techniques to launch and detect stable modes: large experimental

databases of for low-n AEs, starting for intermediate/high n’s (Fasoli, Snipes)– Drive and damping mechanisms qualitatively understood– Quantitative predictions on damping to be improved, especially in regimes in which fluid

and kinetic models give different results (Guenter, Gorelenkov)– Methods for systematic expt.-theory comparison when many modes coexist

MAST

High frequency MHD and fast particles Nonperturbative modes (EPMs)

– Effect of Energetic Particle Modes well above marginal stability on profile?

• Ex. of simulation of -AE interaction redistribution

n(r)AE wave-fieldinitial

final

r/a r/aF.Zonca et al.

High frequency MHD and fast particlesNonlinear wave-particle interaction

– Redistribution and losses• Limits to ITER operational scenarios?• Self-consistent fast particle profile in ITER?

• Significant progress in qualitative understanding, particularly in weakly nonlinear regime, where even some quantitative aspects are reproduced

• Limited experimental data on fast ion redistribution and losses (difficulty in achieving large amplitudes and in diagnosing radial distribution of fast ions)Todo, Gorelenkov, Takechi

High frequency MHD and fast particlesDiagnostic use

– Information from MHD spectroscopy?• Background plasma (e.g. Alfvén Cascades: qmin(t))• Fast particle distribution

– Potential for stand alone use and real time applications to be demonstrated

High frequency MHD and fast particlesPossibilities for burn control

– Burn control tools and methods?

• Some building blocks based on control of fast particles and related modes (AEs + ICRH) are being tested (e.g. at JET)

• Attempts at simulating burning plasmas using NBI to mimic heating (JT-60U)

• Otherwise open question

6th ITPA MHD Topical Group Meeting combined with W60 IEA Workshop on Burning Plasmas

Session II MHD Stability and Fast Particle Confinement  

14.30 Introduction A Fasoli

14.40 TAE and EAE damping in JET A Fasoli

14:55 TAE damping rates compared with NOVA-K J Snipes

15.15 Fast particle driven modes - a new gyrokinetic code with full orbits S Guenter

15.35 Alfvén Eigenmode stability with beams and alpha-particle profile quasilinear relaxation in ITER

N Gorelenkov

15.55 Nonlinear evolution of Alfven eigenmodes in an ITER-like plasma Y Todo

16.15 Coffee

16.35 Fast particle confinement and TAEs in JT-60U M Takechi

16.55 CAEs on MAST L Appel

17.15 Fast ion motion perturbed by NTM magnetic island K Hamamatsu

17.35 ECCD feedback on NTMs on AUG S Guenter

17.55 2/1 NTM stabilisation on DIII-D T Strait

18.15 Discussion Led by A Fasoli

19:30 Close