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Preliminary ELM mitigation experiments on MAST Presented by Andrew Kirk

Preliminary ELM mitigation experiments on MAST Presented by Andrew Kirk EURATOM / UKAEA Fusion Association. M. Becoulet, E. Nardon CEA/Cadarache R. Koslowski, Y. Liang Juelich

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Preliminary ELM mitigation experiments on MAST Presented by Andrew Kirk

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  1. Preliminary ELM mitigation experiments on MAST Presented by Andrew Kirk EURATOM / UKAEA Fusion Association M. Becoulet, E. Nardon CEA/Cadarache R. Koslowski, Y. Liang Juelich B. Ayed, G. Counsell, G. Cunningham, R.Gaffka, M. Hood, D.Howell,R. Martin, H. Meyer, C.Perez Von Thun, S. Pinches A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  2. Installation of magnetic coils on MAST Plan to install 12 “DIII-D I-coils” in MAST To be used for ELM mitigation and TAE studies Complete installation by the end of 2007 A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  3. Error Field Correction Coils in MAST Set of four ex-vessel error field correction coils wired in pairs to produce odd-n spectrum,Imax = 15 kA·turns (3 turns) A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  4. EFCC in n=1 configuration : toroidal phasing for 4 coils (++--) Calculations have been performed by Marina Becoulet /CEA Configuration is ~resonant A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  5. EFCC in n=1 configuration : toroidal phasing for 4 coils (++--) Calculations show that 3kAturns produces islands of ~ 1.5 cm and is sufficient to ergodise the edge A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  6. EFCC in n=1 configuration : toroidal phasing for 4 coils (++--) A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  7. Preliminary n=1 experiments Error field A left at nominal value Increasing error field B L-H transition effected by size of Error field –need to ramp field only after the transition A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  8. Preliminary n=1 experiments Applying 3kA.t to both coils after the L-H transition (the simulated scenario) Often produced a H-L back transition Limited operational window where mitigation predicted and no locked mode A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  9. ELM mitigation using the Error field B coils in n=2 B + A + A B - + Using A to correct most of the intrinsic error field and adding the mitigation field to the modified B (i.e. as far as the simulations are concerned A carries zero current) A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  10. Simulations -Poloidal spectra and chirikov We have enough current capability to ergodise A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  11. Simulations -Magnetic perturbation, island size Br and island size comparable or larger than DIII-D A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  12. Experiments – target plasma Moderately regular ELMing plasma achieved – gas fuelling cut at 150 ms Density still ramps in H-mode but not so much A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  13. Experiments – application of n=2 ELMs are re-established as the plasma current is ramped down In this case 12 kA.t are used in EFFCB without a back transition Possible effect on ELMs observed A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  14. Experiments – effect on the pedestal *ped ~ 0.1-0.3 Teped larger in case with EFFCB = 12 kA.t A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  15. Effect on the strike point 17916 (without) 17919 (with) No visible splitting of the strike points A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  16. Effect on strike point 17916 (without) 17919 (with) No visible splitting of the strike points Power loadings to the targets greater in case with field applied A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  17. Expected effect on strike point MAST EFCCs n=2; I_EFCCs=10kAt Calculations by Eric Nardon Predicted splitting << strike point width The points represent the intersections of field lines with the divertor. A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

  18. Summary • Preliminary n=1 and n=2 ELM mitigation experiments have been attempted using the error field correction coils on MAST . • One problem has been establishing a good target plasma i.e. slow density rise, low neutral gas, regularly ELM-ing, Long H-mode • With n=1 had problems with H-mode access and modes that locked • Some interesting effects have been seen with n=2, especially at low collisionality • To be continued…. A.Kirk presented at ITPA Pedestal meeting, Garching, May 2007

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