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ASDEX Upgrade: Recent hardware upgrades

ASDEX Upgrade: Recent hardware upgrades. extended pulse length to 10 s current flattop (= 2-3 t R even at 10 keV) extended PF coil operational window to run < d> = 0.55 discharges developed ICRH to routinely deliver > 5 MW in ELMy H-mode

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ASDEX Upgrade: Recent hardware upgrades

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  1. ASDEX Upgrade: Recent hardware upgrades • extended pulse length to 10 s current flattop (= 2-3 tR even at 10 keV) • extended PF coil operational window to run <d> = 0.55 discharges • developed ICRH to routinely deliver > 5 MW in ELMy H-mode • increased W coverage of inner wall (70%): centerpost, upper divertor and PSL

  2. ASDEX Upgrade: Recent hardware upgrades • extended pulse length to 10 s current flattop (= 2-3 tR even at 10 keV) • extended PF coil operational window to run <d> = 0.55 discharges • developed ICRH to routinely deliver > 5 MW in ELMy H-mode • increased W coverage of inner wall: centerpost, upper divertor and PSL Note: new fast steerable ECRH launcher has been installed during last opening

  3. ASDEX Upgrade: Recent hardware upgrades • extended pulse length to 10 s current flattop (= 2-3 tR even at 10 keV) • extended PF coil operational window to run <d> = 0.55 discharges • developed ICRH to routinely deliver > 5 MW in ELMy H-mode • increased W coverage of inner wall: centerpost, upper divertor and PSL • commissioned / started development of new diagnostics: • Doppler reflectometry • Edge Ti from Li beam • Ultrafast (ns) Thomson digitisation for filament detection • Collective Thomson Scattering (Risø, development started) • Fast ion loss detector (first light last week)

  4. High Z PFC development 5 MW (3.7 GHz) The future: preparing ITER operation

  5. EU Associations play active role in the programme

  6. Task Forces in 2003/2004

  7. Understanding of Transport

  8. Understanding the density peaking • Density peaking shows a variation with density itself • Low density L-modes with strong electron heating: 'density pump-out' (!) • Density dependence well described by dependence on neff = nei / wDe • (curvature drift frequency wDe provides estimate of ITG/TEM growth rate)

  9. Difference between particle and heat transport • ITG dominated transport should peak density profile • TEM dominated transport should flatten density profile • Method to discriminate between different modes – looks promising

  10. Active NTM Control

  11. Direct ECCD stabilisation – impact on ITER ASDEX Upgrade experimental points ITER upper ECRH launcher design • ASDEX Upgrade results impact design of ITER ECRH launcher • design requirements based on extrapolation of experimental results • strong interaction with design team • In addition: explore alternative NTM control methods

  12. Frequently Interrupted Regime (FIR) NTMs Pure (3,2) NTM Full symbols: JET Open symbols: ASDEX Upgrade (3,2) coupled to (4,3) FIR regime similar in dimensionless parameters (JET and ASDEX Upgrade) Physics: 3-wave coupling to ideal (m+1,n+1) instability reduces NTM

  13. Transition to FIR NTMs can be induced by ECCD =const. (power control) co-ECCD ctr-ECCD local CD at q=4/3 surface decreases 4/3 stability and provokes FIR NTMs

  14. Sawtooth tailoring by ECCD in ASDEX Upgrade • Experiments with slow Bt-ramp, 0.8 MW co-ECCD and 5.1 MW NBI: • increase of sawtooth period for deposition outside inversion radius • decrease of sawtooth period for deposition inside inversion radius • Ctr-ECCD shows inverse behaviour

  15. Removal of sawteeth avoids NTM during ECCD pulse Bt ramp + feedback controlled b-ramp maintain correct ECCD deposition

  16. Active ELM Control

  17. Triggering ELMs by pellet injection Injection of small pellets at high velocity triggers type I ELMs With pellet repetition rate higher than ELM frequency, control is achieved

  18. Other ELM control methods: supersonic jet (1.5 km/s) Collaboration with CEA Cadarache • Delay time between injection and ELM decreases with amount of gas • Pellet triggered ELMs show much less delay (favourable to minimise losses) • Note: supersonic gas jet has a high fuelling efficiency (> 50%)!

  19. Other ELM control methods: plasma 'wobbling' A slight wobbling of the z-position can lock the type I ELM frequency Locking demonstrated over a surprisingly wide range (up and down) Note: ELM triggered during downward motion (contrary to TCV!)

  20. Other ELM control methods: ECRH modulation

  21. Scenario Development

  22. Beyond standard H-mode: the improved H-mode • confinement improved by density peaking (no sawteeth, fishbones) • NTM onset is high (shaping?) and high b operation leads to FIR NTMs • compatible with type II ELM power exhaust

  23. 0.7 0.6 0.5 0.4 H89 betaN / (q95**2) 0.3 0.2 0.1 0 0 .2 .4 .6 .8 1 1.2 1.4 sqrt(eps) betap Application to ITER: hybrid operation at higher q Longer pulses ITER 1.4 • At fixed geometry and Bt: nTt scales like bN H / q952 • H=1.2 and bN=2.15 allow to drop Ip from 15 MA to 12 MA (q95 up to 3.8) • pulse length more than doubles at constant Pfus and Q ('hybrid' operation)

  24. Application to ITER: hybrid operation at higher q 0.7 Duration longer 10 conf. times 0.6 Longer pulses 0.5 ITER 0.4 H89 betaN / (q95**2) 0.3 0.2 0.1 0 0 .2 .4 .6 .8 1 1.2 1.4 sqrt(eps) betap • At fixed geometry and Bt: nTt scales like bN H / q952 • H=1.2 and bN=2.15 allow to drop Ip from 15 MA to 12 MA (q95 up to 3.8) • pulse length more than doubles at constant Pfus and Q ('hybrid' operation)

  25. Application to ITER: high Q operation (at low q) 0.7 Higher fusion power 0.6 0.5 ITER 0.4 H89 betaN / (q95**2) 0.3 0.2 0.1 0 0 .2 .4 .6 .8 1 1.2 1.4 sqrt(eps) betap • At fixed geometry Bt, and IP, H=1.2 and bN=2.55 double Pfus and Q • this scenario has the potential to become the new ITER reference • world wide effort is under way (ASDEX Upgrade, DIII-D, JET, JT-60U)

  26. 0.7 q-range 3-4 0.6 4-5 5-6 6-7 0.5 7-8 0.4 H89 betaN / (q95**2) 0.3 0.2 0.1 0 .1 .2 .3 .4 .5 .6 .7 .8 .9 1 1.1 1.2 sqrt(eps) betap Application to ITER: high Q operation (at low q) Higher fusion power Recent progress ITER • Note (1): lower q emphasises higher nTt • Note (2): similarity not perfect, ITER has somewhat stronger shaping

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