Work in Progress: Dependence of RMP ELM Suppression on Width of the Island Overlap Region
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Transcript of Work in Progress: Dependence of RMP ELM Suppression on Width of the Island Overlap Region
M E Fenstermacher Thrust 1 YearEnd Rev 04/22/23 02:12 AM 1
M.E. Fenstermacher 12th PEP/8th DIVSOL ITPA04/22/23 02:12 1
Work in Progress: Dependence of RMP ELM Suppression on Width of the Island Overlap
Region
M.E. Fenstermacheron 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 the12th Pedestal and Edge Physics ITPA Meeting
IPP, Garching, GermanyMay 7-10, 2007
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• 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
Recent Experiments (April 3 & 6) Focused on Width of Island Overlap Region Needed for Complete ELM Suppression
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Combination of Internal I-coils and External C-coils Used for RMP ELM Control and Error Field Correction
• 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
Schaffer
M.E. Fenstermacher 12th PEP/8th DIVSOL ITPA04/22/23 02:12 4
ITER Similar Shape plasmas (ISS) have higher magnetic shear and a narrower resonant window
• 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
Evans, SFP Talk
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Changes in plasma profiles previously suggested that effect of the RMP in the region 0.85 < N < 0.95 might be important
Evans, SFP TalkEvans, SFP Talk
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For q95=3.6 in Resonance Window, Higher RMP Coil Current Suppresses ELMs, Vacuum Islands Overlap in to N = 0.78
Schaffer
ELMSuppressedI: 6.3 kAC: 1x EFC
• Clear gap at N = 0.78 between 7/3 and 4/2 islands
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While ELMing, Overlap of Vacuum Magnetic Islands for q95=3.6 in Resonance Window Extends to N=0.87
Schaffer
ELMingI: 4 kAC: 1x EFC
• Small gap at N = 0.867 between 3/1 and 8/3 islands
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Region Where Island Overlap Boundary Changes Inside of Location of Maximum Pressure Gradient Change
• 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 stoc
vac / pped = 1.9
• ELM Suppressed stoc
vac / pped = 4.4
Schaffer
pedptot
pedptot
pTOT| (kPa/N)
ELMingI: 4 kAC: 1x EFC
ELMSuppressedI: 6.3 kAC: 1x EFC
stocvac
stocvac
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Pedestal Width Extracted from Fits to Thomson and CER Data, example 6.4 kA, q95=3.6, ELM suppressed
Osborne
fz
Te
ne
Ti
pe i
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For q95=3.8 Outside Resonance Window, Small Increase of C-coil Current Achieves ELM Suppression
Icoil 3 kA
C-coil
1.2x
Icoil 3 kA
C-coil
1.0x
ne
q95
Icoil
vrotcore
vrotedge
D
D
Ccoil
Ip
Pinj
Bdotodd
Bdoteven
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Comparison Suggests that Vacuum Island Overlap in to N < 0.9 Required for ELM Suppression
Schaffer, Aldan
pedptot
pedptot
pTOT| (kPa/N)
ELMingI: 3 kAC: 1x EFC
ELMSuppressedI: 3 kAC: 1.2 x EFC
stocvac
stocvac
• ELMing stoc
vac / pped = 2.5
• ELM Suppressed stoc
vac / pped =
3.5
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For q95=3.2 Lower than Resonance Window, Increased I-coil plus C-coil Current Produced ELM Suppression
ne
q95
Icoil
vrotcore
vrotedge
D
D
Ccoil
Ip
Pinj
Bdotodd
Bdoteven
Icoil 4 kA
C-coil
2x
Icoil 3 kA
C-coil
1.0x
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pedptot
pedptot
ELMingI: 3 kAC: 1x EFC
ELMSuppressedI: 4 kAC: 2x EFC
stocvac
stocvac
pTOT| (kPa/N)
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 stocvac
/ pped = 2.4
• ELM Suppressed stoc
vac / pped = 4.5
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ELM Suppression Achieved with Odd Parity I-coil Pitch Resonant at high q95 ~ 7.2
Icoil 6.4 kA
C-coil
1x
Icoil 0.0 kA
C-coil
1x
ne
q95 - 5
Icoil
vrotcore
vrotedge
D
D
Ccoil
Ip
Pinj
Bdotodd
Bdoteven
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At high q, ODD parity Vacuum Island Overlap for ELM Suppression Extends in to N = 0.77
Schaffer, Aldan
pedptot
pedptotELMing
I: 0 kAC: 1x EFC
ELMSuppressedI: 6.4 kAC: 1x EFC stoc
vac
stocvac
pTOT| (kPa/N)• Large number of
islands give deep overlap at high q95
• ELMing stocvac
/ pped = 0.4
• ELM Suppressed stoc
vac / pped =
3.8
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At q95=3.8 ELM Suppression Obtained by Increasing I-coil Current from 3 kA to 4 kA
Icoil 4 kA C-coil
1x
Icoil 3 kA C-coil
1x
ne
q95
Icoil
vrotcore
vrotedge
D
D
Ccoil
Ip
Pinj
Bdotodd
Bdoteven
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Again ELM Suppression Correlated with Increase in Width of the Vacuum Island Overlap Region
Aldan, Schaffer
pedptot
pedptot
pTOT| (kPa/N) ELMingI: 3 kAC: 1x EFCELM
SuppressedI: 4 kAC: 1x EFC
stocvac
stocvac
• Small increase in overlap changes ELMing character
• ELMing stocvac
/ pped = 3.75
• ELM Suppressed stoc
vac / pped = 7.1
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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 WELM / Wped as function of stoc / pped --> sequence:
– Thomson profiles, pped - needs Thomson re-calibration Done
– CERFIT analysis, pped - done for previous good shots Done
– Kinetic efits, Wped Some Shots
– SURFMN analysis of island structure (w/ Fitzpatrick In Progress corrections), stoc and Chirikov parameter,
– Fast magnetics analysis and evaluation of WELM 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 / p
ped <~ 3.5
– ELM Suppressed for 3.5 <~ stocvac / p
ped < 7
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Profile data from spatial sweeps sufficient quality for kinetic EFITs, example 4 kA, q95=3.8, ELM suppressed
Osborne
fz
Te
ne
Ti
pe i
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Kinetic EFITs make a significant difference in the edge q-profile - 3 kA EVEN, q95=3.8, ELMing (80-99% of cycle)
• 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
Osborne
q
<J//>
•Black - EFIT02 w/ MSE
•Magenta - Kinetic EFIT a
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At q95~4, increase in Width of the Island Overlap Region for ELM Suppression Less in Kinetic EFIT than in MSE EFIT
Aldan, Schaffer
pedptot
pedptot
pTOT| (kPa/N)
ELMing KineticI: 3 kAC: 1x EFC
ELMSuppressedKineticI: 4 kAC: 1x EFC
stocvac
stocvac
• Island overlap width less in both cases
• Change for ELM suppression less
• ELMing stoc
vac / pped = 3.0
• ELM Suppressed stoc
vac / pped =
5.4
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At High q95~7.5 Little Difference in Vacuum Width of Island Overlap Region in Kinetic vs MSE EFITs
Aldan, Schaffer
pedptot
pedptotELMing
KineticI: 0 kAC: 1x EFC
ELMSuppressedKineticI: 6.4 kAC: 1x EFC
stocvac
stocvac
pTOT| (kPa/N)• Overlap width
may be slightly larger
• Different than low q kinetic EFIT case
• ELMing stocvac
/ pped ~ 2.5
• ELM Suppressed stoc
vac / pped =
5.4
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Discharges with ELM Suppression Show Consistently Higher Normalized Island Overlap Region Width
Shot 126435 126442 128371 128372 128376 128377 128474 128475 128464 128466
Q95, Icoil, Ccoil
3.6 4 kA 1x
3.6 6.3 kA 1x
3.8 3 kA 1x
3.8 3 kA 1.2x
3.8 3 kA 1x
3.8 4 kA 1x
3.2 4 kA 2x
3.2 3 kA 1x
7.2 6.4 kA 4x
7.2 0 kA 1x
ELMs? Yes No Yes No Yes No No Yes No Yes
stocvac .135 .222 .10 .14 .15 .2 .16 .09 .228 .03
pped .07 .05 .04 .04 .04 .028 .035 .04 .06 .06
stocvac /
pped 1.9 4.4 2.5 3.5 3.75 7.1 4.5 2.4 3.8 0.4
• Initial analysis with vacuum fields and MSE EFITs suggests:– ELMing for 0 <= stoc
vac / pped <~ 3.5
– ELM Suppressed for 3.5 <~ stocvac / p
ped < 7
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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: stocvac / p
ped > 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 D 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)
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Back-up Slides
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Width of q resonance window expands with I-coil and C-coil current
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]
ne
q95
C79
IU30
D
D
D
D
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Increasing C-coil Current for Fixed ODD Parity I-coil can Produce ELM Suppression
ne
q95
IU30 vrotT1
vrotT23
gapoutD
q0
D
C79
Ip
Pinj
Bdotodd
Bdoteven
Icoil 6.4 kA
C-coil
4x
Icoil 6.4 kA
C-coil
1x
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Island overlap at high q, ODD parity
Aldan, Schaffer
ELMing
ELM Suppressed
Icoil 6.4 kA C-coil
4x
Icoil 6.4 kA C-coil
1x
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For q95=3.8 Outside Resonance Window, Small Increase of C-coil Current Achieves ELM Suppression
ne
q95
IU30 vrotT1
vrotT23
gapout
D
q0
D
Ip
Pinj
Bdotodd
Bdoteven
Icoil 3 kA
C-coil
1.2x
Icoil 3 kA
C-coil
1.0x
C79
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M.E. Fenstermacher 12th PEP/8th DIVSOL ITPA04/22/23 02:12 30
Combination of Internal I-coils and External C-coils Used for RMP ELM Control and Error Field Correction
• 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
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Are transients that return at low rotation driven by NTMs in core?
ne
dB/dt odd
vrotT9
D
n3rms
D
pr12 esl079
vrotT7
n2rms
n1rms
dB/dt even
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RMP H-modes have reduced particle confinement times compared to ELMing H-modes
• Three small ELM-like D bursts are triggered during the HFS pellet ablation phase but do not persist.
Evans, SFP Talk
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In new ODD Parity RMP Shots Pellet Density Perturbation Evolution Different from Low q95 EVEN Parity Cases
Jernigan, Baylor
D
D
ne ne
ne ne
D
D
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Splitting of OSP j_sat on floor probes using radial SP sweeps - useful for validation of RMP penetration Models
• 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
Watkins
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ISP Splitting of C1+ emission at 150º Depends on I-coil Parity/Phase - Useful for Validation of RMP Penetration
128465 @ 5365 ms L-mode Odd parity 0° Phase
128473 @ 5428 msL-mode Even Parity60° Phase
C II 514 nm
West, Schmitz
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Plasma profiles look good with 2007 Leonard/Bray calibration - 4 kA, q95=3.8, ELM suppressed
Osborne
fz
Te
ne
Ti
pe i
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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
M E Fenstermacher Thrust 1 YearEnd Rev 04/22/23 02:12 AM 38
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Island overlap at high q, ODD parity
Aldan, Schaffer
ELMing
Icoil 0.0 kA C-coil
1x
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M.E. Fenstermacher 12th PEP/8th DIVSOL ITPA04/22/23 02:12 39
Island overlap at high q, ODD parity
Aldan, Schaffer
ELM Suppressed
Icoil 6.4 kA C-coil
1x
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I-coil parity controls pedestal island overlap
Both parities suppress ELMsOdd (weak RMP) small islands little or no change in pedestalEven (strong RMP) stochastic transport / pedestal control
Evans EPS05