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Energetic Particle Physics in Burning Plasmas: from ITER to DEMO

Energetic Particle Physics in Burning Plasmas: from ITER to DEMO. Guoyong Fu on behalf of Energetic Particle SFG. Acknowledgement: E. Fredrickson, C. Kessel, G. Kramer, N. Gorelenkov, R. Nazikian, W. Tang. FESAC Strategic Planning Meeting, Aug. 7, 2007, PPPL. Outline. Introduction

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Energetic Particle Physics in Burning Plasmas: from ITER to DEMO

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  1. Energetic Particle Physics in Burning Plasmas: from ITER to DEMO Guoyong Fu on behalf of Energetic Particle SFG Acknowledgement: E. Fredrickson, C. Kessel, G. Kramer, N. Gorelenkov, R. Nazikian, W. Tang FESAC Strategic Planning Meeting, Aug. 7, 2007, PPPL

  2. Outline • Introduction • Alpha particle-driven modes: linear stability and nonlinear dynamics • Alpha particle-driven modes in ITER and DEMO • New initiative for advanced predictive simulations of multiple modes in ITER and DEMO

  3. Introduction • A key question for burning plasmas is whether alpha particle transport is classical (i.e., slow-down via collisions or anomalous due to instabilities. • In a fusion reactor, super-Alfvenic alpha particles can resonantly destabilize Alfven eigenmodes and EPMs. • Alpha particle loss or redistribution can be caused by: Ripple MHD modes such as sawteeth and NTM Alfven instabilities (fishbone/TAE/EPM)

  4. Why we care • Alpha particle loss can seriously damage reactor wall and degrade alpha heating; • Alpha particle redistribution can modify alpha heating deposition profile; • Alpha particles can significantly influence MHD stability (sawtooth, resistive wall modes, kinetic ballooning modes etc) • Alpha particle-driven Alfven modes may influence thermal plasma equilibrium, stability and confinement via their effects on NBI-driven current, zonal flow etc (nonlinear coupling !)

  5. What we know • Single particle confinement is well understood (slowing-down, ripple loss, loss due to a given MHD perturbation) • Linear stability of TAE is well understood (alpha drive and damping mechanisms) • Nonlinear dynamics of a single alpha-driven mode (saturation due to wave-particle trapping, hole-clump formation and frequency chirping)

  6. A variety of AEs and collective effects due to fast ions Models and numerical tools: High frequency modes ci, ci(velocity transport): Linear MHD NOVA code ci,ci Linear wave code TORIC Nonlinear HYM initial value, hybrid Low frequency modes ci (radial transport): Linear codes: HINST – local nonperturbative ballooning NOVA-K –hybrid MHD-kinetic NOVA-KN – nonperturbative global hybrid Nonlinear codes: M3D – initial value hybrid MHD-kinetic code NOVA-K – reduced theoretical model for wave saturation and fast ion transport Single particle motion: ORBIT code Rich spectrum of modes in tokamaks

  7. What we don’t know well • Alpha particle transport in the presence of multiple modes • Feedback of alpha particle-driven instabilities on thermal plasmas

  8. Linear Stability of TAE • Alpha particle drive • Plasma dampings: ion Landau damping electron collisional damping “radiative damping” due to FLR  stability is sensitive to plasma parameters and profiles !

  9. Alpha particle drive is maximized at kqra ~ 1 G.Y. Fu et al, Phys. Fluids B4, 3722 (1992)

  10. Parameters of Fusion Reactors

  11. Critical alpha parameters of TFTR/JET, ITER and DEMO DEMO_Japan ba/bc DEMO_EU ARIES-AT ARIES-ST ITER JET TFTR a/ra

  12. Multiple high-n TAEs are expected be excited in ITER from NOVA-K Instability is maximized at kqra ~ 1 N.N. Gorelenkov, Nucl. Fusion 2003

  13. NSTX observes that multi-mode TAE bursts can lead to larger fast-ion losses than single-mode bursts 1% neutron rate decrease: 5% neutron rate decrease: • TAE avalanches cause enhanced fast-ion losses. • Potential to model island overlap condition with full diagnostic set. E. Fredrickson, Phys. Plasmas 13, 056109 (2006)

  14. State of art nonlinear simulations (M3D) can treat a few low-n modes (n=1,2 & 3) time

  15. DEMO versus ITER • Alpha drive is higher and mode number is larger in DEMO • Expect stronger Alfven instability and more modes >> wave particle resonance overlap and alpha particle redistribution likely ! • Alpha beta is a significant fraction of thermal beta >> alpha particle effects on MHD modes and thermal plasma stronger !

  16. New initiative for predictive simulation of multiple alpha-driven high-n Alfven modes in ITER and DEMO • It is needed urgently for ITER operation and for design of DEMO; • This is a scientific grand challenging project. • Needs most advanced supercomputer because it requires much higher spatial resolution and much longer simulation time as compared to the state of art. • Needs careful experimental validation for predictive capability.  better diagnostic for Alfven modes and alpha particle distribution.  need more manpower for nonlinear simulations.

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