6 th itpa mhd topical group meeting combined with w60 iea workshop on burning plasmas session ii mhd...
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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