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Work in Progress: Dependence of RMP ELM Suppression on Width of the Island Overlap Region

Work in Progress: Dependence of RMP ELM Suppression on Width of the Island Overlap Region M.E. Fenstermacher on behalf of the Thrust IT-1 ELM Control for ITER Group Special Thanks to M. Aldan, T.E. Evans, P. Gohil, A.W. Leonard, R.A. Moyer, T.H. Osborne, M. Schaffer Presented at the

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Work in Progress: Dependence of RMP ELM Suppression on Width of the Island Overlap Region

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  1. Work in Progress: Dependence of RMP ELM Suppression on Width of the Island Overlap Region M.E. Fenstermacher on behalf ofthe Thrust IT-1 ELM Control for ITER Group Special Thanks to M. Aldan, T.E. Evans, P. Gohil, A.W. Leonard, R.A. Moyer, T.H. Osborne, M. Schaffer Presented at the 12th Pedestal and Edge Physics ITPA Meeting IPP, Garching, Germany May 7-10, 2007

  2. Recent Experiments (April 3 & 6) Focused on Width of Island Overlap Region Needed for Complete ELM Suppression • Goals: • Develop an ELM suppression criterion based on the required width of the stochastic region that could be used for comparative evaluation of different proposed ITER RMP coil designs • Determine the effect of toroidal rotation on the penetration of the RMP fields in the plasma. • Width of the Island Overlap Region Varied in 5 Different Ways in ITER Similar Shape Plasmas, at ITER e*, at feedback controlled N = 1.9 • q95 scans --- Changes in q95 and q-shear affect island overlap • I-coil current scans --- Amplitude of RMP affects island size • 2 toroidal rotation values --- Screening of RMP affected by rotation • ODD parity I-coil at high q95 ~ 7 --- n=3 modes pitch resonant for odd parity and high q95 • C-Coil amplitude variation --- Mixture of n=1 modes used to “fill in” edge mode spectral density

  3. Strength of n=3 RMP from I-coil depends on up/down parity of coil sets Increasing C-coil current increases strength of n=1 RMP beyond nominal error field correction Combination of Internal I-coils and External C-coils Used for RMP ELM Control and Error Field Correction Schaffer

  4. ITER Similar Shape plasmas (ISS) have higher magnetic shear and a narrower resonant window Evans, SFP Talk • Larger RMP coil current needed in ISS plasmas for ELM control • Resonant window smaller in ISS plasmas with larger RMP current • May be a signature of increased RMP screening

  5. Changes in plasma profiles previously suggested that effect of the RMP in the region 0.85 < YN < 0.95 might be important Evans, SFP Talk Evans, SFP Talk

  6. ELM Suppressed I: 6.3 kA C: 1x EFC For q95=3.6 in Resonance Window, Higher RMP Coil Current Suppresses ELMs, Vacuum Islands Overlap in to N = 0.78 Schaffer • Clear gap at N = 0.78 between 7/3 and 4/2 islands

  7. ELMing I: 4 kA C: 1x EFC While ELMing, Overlap of Vacuum Magnetic Islands for q95=3.6 in Resonance Window Extends to N=0.87 Schaffer • Small gap at N = 0.867 between 3/1 and 8/3 islands

  8. pedptot ELM Suppressed I: 6.3 kA C: 1x EFC pTOT| (kPa/YN) pedptot ELMing I: 4 kA C: 1x EFC stocvac stocvac Region Where Island Overlap Boundary Changes Inside of Location of Maximum Pressure Gradient Change Schaffer • Islands well overlapped at pedestal top in both cases • Change from ELMing to ELM Suppressed for change in overlap well inside pedestal top (vacuum fields) • ELMing Dstocvac / Dpped = 1.9 • ELM Suppressed Dstocvac / Dpped = 4.4

  9. Pedestal Width Extracted from Fits to Thomson and CER Data, example 6.4 kA, q95=3.6, ELM suppressed Osborne ne fz Te Ti Wi pe

  10. For q95=3.8 Outside Resonance Window, Small Increase of C-coil Current Achieves ELM Suppression q95 Icoil 3 kA C-coil 1.2x Icoil 3 kA C-coil 1.0x Ip Da Pinj ne Da Icoil Bdotodd Ccoil vrotcore vrotedge Bdoteven

  11. pedptot ELMing I: 3 kA C: 1x EFC pTOT| (kPa/YN) pedptot ELM Suppressed I: 3 kA C: 1.2 x EFC stocvac stocvac Comparison Suggests that Vacuum Island Overlap in to N < 0.9 Required for ELM Suppression Schaffer, Aldan • ELMing Dstocvac / Dpped = 2.5 • ELM Suppressed Dstocvac / Dpped = 3.5

  12. For q95=3.2 Lower than Resonance Window, Increased I-coil plus C-coil Current Produced ELM Suppression q95 Icoil 4 kA C-coil 2x Icoil 3 kA C-coil 1.0x Ip Da Pinj ne Da Icoil Ccoil Bdotodd vrotcore vrotedge Bdoteven

  13. pTOT| (kPa/YN) pedptot ELMing I: 3 kA C: 1x EFC pedptot ELM Suppressed I: 4 kA C: 2x EFC stocvac stocvac ELM Suppression at Low q95 =3.2 Outside Resonance Window Achieved by Broadening Island Overlap Region Schaffer, Aldan • n=1 islands from C-coil used to “fill-in” edge mode spectral density • ELMing Dstocvac / Dpped = 2.4 • ELM Suppressed Dstocvac / Dpped = 4.5

  14. ELM Suppression Achieved with Odd Parity I-coil Pitch Resonant at high q95 ~ 7.2 q95 - 5 Icoil 6.4 kA C-coil 1x Icoil 0.0 kA C-coil 1x Ip Da Pinj ne Da Icoil Ccoil Bdotodd vrotcore vrotedge Bdoteven

  15. pedptot ELMing I: 0 kA C: 1x EFC pTOT| (kPa/YN) pedptot ELM Suppressed I: 6.4 kA C: 1x EFC stocvac stocvac At high q, ODD parity Vacuum Island Overlap for ELM Suppression Extends in to N = 0.77 Schaffer, Aldan • Large number of islands give deep overlap at high q95 • ELMing Dstocvac / Dpped = 0.4 • ELM Suppressed Dstocvac / Dpped = 3.8

  16. At q95=3.8 ELM Suppression Obtained by Increasing I-coil Current from 3 kA to 4 kA q95 Icoil 4 kA C-coil 1x Icoil 3 kA C-coil 1x Ip Da Pinj ne Da Icoil Ccoil Bdotodd vrotcore vrotedge Bdoteven

  17. pedptot ELMing I: 3 kA C: 1x EFC pTOT| (kPa/YN) ELM Suppressed I: 4 kA C: 1x EFC pedptot stocvac stocvac Again ELM Suppression Correlated with Increase in Width of the Vacuum Island Overlap Region Aldan, Schaffer • Small increase in overlap changes ELMing character • ELMing Dstocvac / Dpped = 3.75 • ELM Suppressed Dstocvac / Dpped = 7.1

  18. Analysis needed to develop criteria for ITER coil evaluation in progress - contains linked components • Goal is to evaluate the degree of island overlap and the radial width of the overlap region • Plot we want is DWELM / Wped as function of Dstoc / Dpped --> sequence: • Thomson profiles, Dpped - needs Thomson re-calibration Done • CERFIT analysis, Dpped - done for previous good shots Done • Kinetic efits, Wped Some Shots • SURFMN analysis of island structure (w/ Fitzpatrick In Progress corrections), Dstoc and Chirikov parameter, • Fast magnetics analysis and evaluation of DWELM In Progress • TRIP3D calc. of field line loss fraction and connection lengths • Initial analysis with vacuum fields and MSE EFITs suggests: • ELMing for 0 <= stocvac / Dpped <~ 3.5 • ELM Suppressed for 3.5 <~ stocvac / Dpped < 7

  19. Profile data from spatial sweeps sufficient quality for kinetic EFITs, example 4 kA, q95=3.8, ELM suppressed Osborne ne fz Te Ti Wi pe

  20. Kinetic EFITs make a significant difference in the edge q-profile - 3 kA EVEN, q95=3.8, ELMing (80-99% of cycle) Osborne <J//> • EFITs with model p’ and ff’ and constrained only by MSE data do not represent edge bootstrap current peak • Kinetic EFIT shows different q-shear in the pedestal q • Black - EFIT02 w/ MSE • Magenta - Kinetic EFIT a

  21. pedptot ELMing Kinetic I: 3 kA C: 1x EFC pTOT| (kPa/YN) ELM Suppressed Kinetic I: 4 kA C: 1x EFC pedptot stocvac stocvac At q95~4, increase in Width of the Island Overlap Region for ELM Suppression Less in Kinetic EFIT than in MSE EFIT Aldan, Schaffer • Island overlap width less in both cases • Change for ELM suppression less • ELMing Dstocvac / Dpped = 3.0 • ELM Suppressed Dstocvac / Dpped = 5.4

  22. pedptot ELMing Kinetic I: 0 kA C: 1x EFC pTOT| (kPa/YN) ELM Suppressed Kinetic I: 6.4 kA C: 1x EFC pedptot stocvac stocvac At High q95~7.5 Little Difference in Vacuum Width of Island Overlap Region in Kinetic vs MSE EFITs Aldan, Schaffer • Overlap width may be slightly larger • Different than low q kinetic EFIT case • ELMing Dstocvac / Dpped ~ 2.5 • ELM Suppressed Dstocvac / Dpped = 5.4

  23. Discharges with ELM Suppression Show Consistently Higher Normalized Island Overlap Region Width • Initial analysis with vacuum fields and MSE EFITs suggests: • ELMing for 0 <= Dstocvac / Dpped <~ 3.5 • ELM Suppressed for 3.5 <~ Dstocvac / Dpped < 7

  24. Conclusion - Initial Analysis Points to Correlation Between Width of Vacuum Island Overlap Region and ELM Suppression • Correlation suggests criteria for comparison of candidate coils designs for ITER could be developed • Very preliminary analysis: Dstocvac / Dpped > 3.5 for ELM Suppression • Many upgrades to this analysis are necessary: • Kinetic EFITs for accurate q-profiles in island overlap region • Calculation of field line loss fraction with TRIP3D including effect of relative toroidal phases between I-coil, C-coil and Error Field perturbations • Corrections to RMP penetration strength due to toroidal rotation screening - use formulation of Fitzpatrick theory • Need to compare cases based on pedestal energy loss during remaining transients, not just based on Da intensity • Updates will be presented: May 24 at ITPA MHD Group, July 3 at EPS poster, Various ITER Design Review WG1 DRPO Meetings (if requested)

  25. Back-up Slides

  26. Width of q resonance window expands with I-coil and C-coil current Da 4 kA Icoil, 2x C-coil q95=[3.2, 3.8] 3 kA I-coil, 2x C-coil 3 kA I-coil, 1.2x C-coil 3 kA I-coil, 1.0x C-coil, Q95=[3.45, 3.6] q95 Da ne Da C79 Da IU30

  27. Increasing C-coil Current for Fixed ODD Parity I-coil can Produce ELM Suppression Ip q95 Icoil 6.4 kA C-coil 4x Icoil 6.4 kA C-coil 1x q0 Pinj Bdotodd ne Da gapout Da Bdoteven vrotT1 IU30 C79 vrotT23

  28. Island overlap at high q, ODD parity Aldan, Schaffer Icoil 6.4 kA C-coil 4x Icoil 6.4 kA C-coil 1x ELM Suppressed ELMing

  29. For q95=3.8 Outside Resonance Window, Small Increase of C-coil Current Achieves ELM Suppression q95 Ip Icoil 3 kA C-coil 1.2x Icoil 3 kA C-coil 1.0x q0 Pinj ne Bdotodd Da gapout Da Bdoteven vrotT1 IU30 C79 vrotT23

  30. Strength of n=3 RMP from I-coil depends on up/down parity of coil sets Increasing C-coil current increases strength of n=1 RMP beyond nominal error field correction Combination of Internal I-coils and External C-coils Used for RMP ELM Control and Error Field Correction

  31. Are transients that return at low rotation driven by NTMs in core? vrotT7 esl079 pr12 dB/dt even n1rms Da Da n2rms n3rms ne vrotT9 dB/dt odd

  32. RMP H-modes have reduced particle confinement times compared to ELMing H-modes Evans, SFP Talk • Three small ELM-like D bursts are triggered during the HFS pellet ablation phase but do not persist.

  33. In new ODD Parity RMP Shots Pellet Density Perturbation Evolution Different from Low q95 EVEN Parity Cases Jernigan, Baylor ne ne Da Da Da Da ne ne

  34. Splitting of OSP j_sat on floor probes using radial SP sweeps - useful for validation of RMP penetration Models Watkins • New ODD parity I-coil case at q95 = 7.2 • Peak near separatrix • Additional peaks in SOL • Also peak in PF region • Similar to features seen at low q95, EVEN parity

  35. ISP Splitting of C1+ emission at 150º Depends on I-coil Parity/Phase - Useful for Validation of RMP Penetration West, Schmitz 128465 @ 5365 ms L-mode Odd parity 0° Phase C II 514 nm 128473 @ 5428 ms L-mode Even Parity 60° Phase

  36. Plasma profiles look good with 2007 Leonard/Bray calibration - 4 kA, q95=3.8, ELM suppressed Osborne ne fz Te Ti Wi pe

  37. Width of the Island Overlap Region Varied in 5 Different Ways in ITER Similar Shape Plasmas at ITER n*e • q95 scans • Changes in q95 and q-shear affect island overlap • I-coil current scans • Amplitude of RMP affects island size • 2 toroidal rotation values • Screening of RMP affected by rotation • ODD parity I-coil at high q95 ~ 7 • N=3 modes pitch resonant for odd parity and high q95 • C_Coil amplitude variation • Add mixture of n=1 modes to “fill in” edge mode spectral density

  38. Island overlap at high q, ODD parity Aldan, Schaffer ELMing Icoil 0.0 kA C-coil 1x

  39. Island overlap at high q, ODD parity Aldan, Schaffer Icoil 6.4 kA C-coil 1x ELM Suppressed

  40. I-coil parity controls pedestal island overlap Evans EPS05 • Both parities suppress ELMs • Odd (weak RMP)  small islands  little or no change in pedestal • Even (strong RMP)  stochastic  transport / pedestal control

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