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Macroscopic Stability Research on NSTX – Results and Theory Interaction S.A. Sabbagh 1, S.P. Gerhardt 2, R.E. Bell 2, J.W. Berkery 1, R. Betti 3, J.M. Bialek 1, J. Breslau 2, R. Buttery 4, L. Delgado- Aparicio 5, D.A. Gates 2, B. Hu 3, R. LaHaye 4, J-K. Park 2, J.E. Menard 2, H. Reimerdes 1, K.C. Shaing 5, K. Tritz 6, and the NSTX Research Team 1 Department of Applied Physics, Columbia University, New York, NY 2 Plasma Physics Laboratory, Princeton University, Princeton, NJ 3 University of Rochester, Rochester, NY 4 General Atomics, San Diego, CA 5 University of Wisconsin, Madison, WI 6 Johns Hopkins University, Baltimore, MD PPPL MHD Science Focus Group Meeting January 6th, 2010 PPPL College W&M Colorado Sch Mines Columbia U Comp-X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U Old Dominion U ORNL PPPL PSI Princeton U Purdue U Sandia NL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Maryland U Rochester U Washington U Wisconsin Culham Sci Ctr U St. Andrews York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Hebrew U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST POSTECH ASIPP ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep U Quebec NSTX Supported by v1.0
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 2 NSTX Macrostability Research is Addressing Topics Needed to Maintain Long-Pulse, High Performance ST Motivation / Goals (e.g. from recent ReNeW process) Maintenance of high N with sufficient physics understanding allows confident extrapolation to ST applications (Hybrid, CTF, DEMO) Sustain target N of ST applications with margin to reduce risk Physics studied in NSTX to best ensure steady-state ST operation Locked mode behavior at low to moderate N < N no-wall Ability of plasma rotational stabilization to maintain high N Possibility of multiple RWMs that can affect active control Physics of 3D fields to control plasma rotation profile (for greater stability, confinement) NTM onset and marginal island width for stabilization Multiple scalable control systems to maintain pulse Successful connections being made to theory – continue/expand interaction…
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 3 NSTX Macrostability Research – Topics Covered in Talk Error fields (n = 1 and n = 3) Resistive wall modes Non-resonant magnetic braking physics NTM threshold physics Improving pulse with n = 1 and N feedback
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 4 n = 1 error field threshold for mode locking decreased as β N increased n = 1 rotating modes sometimes observed, study limited to static modes IPEC resonant field joins linear n e correlation from low-β to increased-β Ideal plasma amplification of applied resonant field restores linear correlation of mode locking threshold with density Lower-β locked later (w/ larger RWM currents) XP903: J.-K. Park Ideal Plasma Amplification Higher-β locked earlier (w/ smaller RWM currents) vacuum IPEC
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 5 Optimal n=3 Error Field Correction Determined vs. I P, B T 2009 “optimal” n = 3 error field correction attained by maximizing angular momentum, scanning I p, B t, elongation n = 3 error field consistent with known equilibrium field coil distortion scales with equilibrium field coil current field phase and amplitude of correction is consistent with that expected from coil distortion n = 3 error field correction routinely used to maximize plasma performance in conjunction with n = 1 RWM feedback control NTV theoretical analysis performed by J-K Park for these cases XP902: S. Gerhardt
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 6 NSTX Macrostability Research – Topics Covered in Talk Error fields (n = 1 and n = 3) Resistive wall modes Non-resonant magnetic braking physics NTM threshold physics Improving pulse with n = 1 and N feedback
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 7 Resistive wall modes can terminate NSTX plasmas at intermediate plasma rotation levels without active control (no simple, scalar crit ) Kinetic modification to ideal MHD growth rate Trapped and circulating ions, trapped electrons Alfven dissipation at rational surfaces Stability depends on Integrated profile: resonances in W K (e.g. ion precession drift) Particle collisionality Trapped ion component of W K (plasma integral) Energy integral collisionality profile (enters through ExB frequency) Hu and Betti, Phys. Rev. Lett 93 (2004) 105002. precession driftbounce Modification of Ideal Stability by Kinetic theory (MISK code) investigated to explain experimental RWM stabilization
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 8 Kinetic modifications show decrease in RWM stability at relatively high V Marginally stable experimental plasma reconstruction, rotation profile exp Variation of away from marginal profile increases stability Unstable region at low Role of energetic particles now under investigation (Berkery, et al.) Theoretical variation of Marginally stable experimental profile 121083 RWM stability vs. V (contours of w ) /a/a / exp 2.0 1.0 0.2 /2 (kHz) Im( W K ) Re( W K ) / exp w experiment 2.0 1.0 0.2 unstable / exp J.W. Berkery
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 99 Channel of “Weak Rotation” for RWM passive stabilization observed in MISK calculations for NSTX; altered by plasma collisionality Stabilization from precession drift resonance at low rotation and bounce resonance at high rotation Stability dependence on collisionality key for ST fusion burn devices w contours vs. ν and NSTX 121083 unstable Marginal stability experiment J.W. Berkery (APS DPP 2009 invited talk; PRL accepted)
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 10 High N shots exhibit low frequency mode activity in magnetic and kinetic diagnostics 133775 0.80.40.61.01.2 t(s) Multi-energy SXR data shows ~ 30 Hz mode activity 02 03 04 05 06 08 10 14 edge core NN 2 4 8 133775 0.80.40.61.01.2 t(s) 0.20.0 I RWM-6 (kA) 0.2 0 0 4 8 ch-18 (kHz) B pu n=1 (G) B N n=1 (G) I p = 0.8 MA ME-SXR low-2 30 50 10 0.5 1.5 Soft X-ray measurements show low frequency mode activity is global Mode activity in RWM frequency range coincident in magnetics, SXR n = 1 RWM feedback on 0 40 0 0 100 0 200 0 0 0 400 0 (arb) XP935: S.A. Sabbagh When unstable, growing n = 1 RWM appears to be independent of ~30 Hz activity
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 11 RWM multimode response theoretically expected to be significant at high N based on ideal MHD theory Boozer multimode criterion for n = 1 met at high N | W | smallest for 2 nd n = 1 eigenfunction Ratio of | W | for 3 rd vs. 1 st least stable mode sometimes also > 1 NN (PoP 10 (2003) 1458.) 133775 mode 3 mode 1 mode 2 t(s) W (arb) no-wall stability DCON 0.20.80.40.60.01.01.2 -20 -10 0 10 | W| ratio 0 2 4 mode 1/mode 3 mode 1/mode 2 n = 1 multimode period t = 0.655s mode 1 mode 2 2.01.00.0 R(m) 1.0 Z(m) 2.0 0.0 -2.0 DCON B N mode 3 (deg) 1800 B N (arb) mode 1 mode 2 mode 3 133775 XP935: S.A. Sabbagh
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 12 Multi-mode VALEN code (RWM control) testing successfully on high N NSTX plasmas mmVALEN to be used to examine response of 2 nd mode to n = 1 feedback, error field and compare to experiment NN Growth rate vs. # of modes – mmVALEN 133775 t = 0.655s 116 DCON modes 76 DCON modes Typical growth times (experiment) J. Bialek
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 13 NSTX Macrostability Research – Topics Covered in Talk Error fields (n = 1 and n = 3) Resistive wall modes Non-resonant magnetic braking physics NTM threshold physics Improving pulse with n = 1 and N feedback
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 14 Stronger braking with constant n = 3 applied field as E reduced – accessing superbanana plateau NTV regime XP933: S.A. Sabbagh 133367 t = 0.815 s i = 1 nq E i / (kHz) Torque not 1/ (non-resonant) NTV in “1/ regime” (|nq E | < i / and * i < 1) Stronger braking expected when E ~ 0 (superbanana plateau) ( K.C. Shaing et al., PPFC 51 (2009) ) – theoretical analysis continues (Sabbagh) E ~ 0 /2 (kHz) 20 15 10 5 0 1.01.11.21.31.41.5 R(m) t(s) 0.795 0.805 0.815 NN 4 I c (kA) 2 ch-5 (kHz) ch-12 (kHz) ch-18 (kHz) core mid outer 6 0 0.4 0.0 20 10 0 20 10 0 8 4 0 0.50.60.70.8 Faster braking with Constant N, applied n = 3 field No mode activity t (s) 40 0 Broad, near zero WITHOUT rational surface locking n = 3 braking 80
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 15 NSTX Macrostability Research – Topics Covered in Talk Error fields (n = 1 and n = 3) Resistive wall modes Non-resonant magnetic braking physics NTM threshold physics Improving pulse with n = 1 and N feedback
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 16 Consistent pre-2009 DIII–D/NSTX results on m/n = 2/1 NTM marginal island width for stability; good restabilization data sets in 2009 W marg / 0.5 i ratio ~ 2 in tokamaks AUG, DIII-D, JET data for 3/2 mode First results show W marg / 0.5 i also ~ 2 for NSTX (2/1 mode) (!) NSTX XP914: R. LaHaye Pre-20092009 data Status: DIII-D Used gas puff to stay in H-mode 5 good 2/1 (and 2 good 3/1) cases Status: NSTX Achieved a reproducible onset condition using modest Li evaporation 8 good cases (2009)
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 17 Required (missing) bootstrap drive for NTM onset better correlated with rotation shear than rotation magnitude Rotation variation via n = 1 or 3 applied field Operational space fully spanned up to locked mode limits No measureable trend vs. rotation Weak positive correlation with normalized rotation shear Lowest/highest thresholds at low/high rotation shear 2d fit vs rotation & rotation shear offers little improvement Consistent with prior results (S.P. Gerhardt, et al., 2008) 0 L q j BS,Sauter /B (dF/dr) A L S F 2/1 Hz XP915: R. Buttery
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 18 NSTX Macrostability Research – Topics Covered in Talk Error fields (n = 1 and n = 3) Resistive wall modes Non-resonant magnetic braking physics NTM threshold physics Improving pulse with n = 1 and N feedback
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 19 Successful N feedback at varied plasma rotation levels Prelude to control Reduced by n = 3 braking does not defeat FB control Increased P NBI needed at lower Steady N established over long pulse independent of over a large range 135468 135513 0.80.40.61.01.2 t(s) 0.20.0 NN 2 4 6 I RWM-6 (kA) 0.6 0 2 4 6 -0.6 P NBI (MW) ch-18 (kHz) ch-5 (kHz) 4 8 10 20 10 n = 3 error correcting phasing n = 3 braking phasing n = 1 feedback XP934: S.A. Sabbagh S.A. Sabbagh, S. Gerhardt, D. Mastrovito, D. Gates 0
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 20 NSTX Macrostability Research – Interaction with Theory Error fields (n = 1 and n = 3) IPEC used successful to support experiment; continue IPEC development, including interface of ideal plasma response to other analyses (Park, Boozer) Resistive wall modes MISK development continues (CU, U. Rochester, PPPL), present focus on energetic particle description, comparison to experiment (Berkery, et al.) Multi-mode RWM analysis with new mmVALEN code (Bialek, Boozer), comparison to experiment (Sabbagh) Non-resonant magnetic braking physics Continued development of MHD models (CU, PPPL, UW), working from Shaing model (Sabbagh), Park/Boozer model (Park), etc. (e.g. Cole, et al.) Work aimed for comparison to particle codes (GTC-Neo (Wang), FORTEC-3D (Satake)) should continue NTM threshold physics Mostly empirical, or simple MRE assumptions to date, largest gap in theory support here (linear – computation of ’ (PEST 3), non-linear codes ?) Improving pulse with n = 1 and N feedback, general RMPs Multi-faceted, including beta, rotation control (Gerhardt, Koleman), RWM control optimization (Hopkins, et al.), ideal, RWM, NTM, ELM stability theory
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 21 Backup Slides
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 22 NSTX Macrostability Research in 2009 is Addressing Topics Furthering Steady Operation of High Performance Plasmas Ideal plasma amplification of applied n = 1 resonant field (IPEC) joins linear density scaling of mode locking threshold from low to moderate-β Optimal n=3 error field correction determined vs. I P, B T RWM instability, observed at intermediate plasma rotation, correlates with kinetic stability theory; role of energetic particles under study Low frequency ~ O(1/ wall ) mode activity at high N being investigated as potential driven RWM Theory shows multi-mode RWM response may be important at high N ; multi-mode VALEN code now passing initial tests Strong non-resonant braking observed NTV braking observed from all i /nq E (R) variations made; apparent transitions in NTV at low Expanded NTM onset experiments continue to find best correlation between NTM onset drive and flow shear Successful NBI power limitation via new N feedback control system; initial success in regulation of N at varied plasma rotation levels
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 23 When unstable, observed growing n = 1 RWM appears to be independent of the driven, ~30 Hz activity Unstable RWM is locked; driven mode co-rotating at low frequency Unstable RWM grows (magnetics); low frequency mode appears steady in SXR 02 03 04 06 08 10 14 high-f mode core 133467 edge NN 4 0.4 0.8 I RWM-6 (kA) 0.2 2 10 8 4 ch-18 (kHz) B pu n=1 (G) B N n=1 (G) 30 50 10 20 0 I P (MA) ch-5 (kHz) 6 2 -0.2 -0.6 6 2 6 10 0 B Ru n=1 (G) 133467 0.20.00.4 t(s) 0.8 t(s) 0.6 0.650.60.70.80.750.85 NN 4 6 2 B N n=1 (G) 2 6 ME-SXR low unstable RWM n = 3 braking unstable RWM
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 24 Multi-mode VALEN code (RWM control) testing successfully on ITER Scenario 4 cases (reversed shear) At highest N, n =1 and 2 are unstable NN Number of modes (VALEN) Growth rate (1/s) single-mode matched to N wall multi-mode VALEN (converged) DCON W shows several modes with high response Three n = 1 modes at high N Two n = 2 modes at high N n = 1 J. Bialek
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 25 Illustration of B n ( ) on plasma surface from mmVALEN for ITER Scenario 4, N = 3.92 n = 1 eigenfunctions shown multi mode response (incl. wall), total B n B n from wall, plasma B n from wall alone toroidal poloidal outboard inboard outboard inboard J. Bialek
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NSTX PPPL MHD SFG mtg: Macroscopic Stability Research on NSTX – Results and Theory (S.A. Sabbagh, et al.)January 6 th, 2010 26 Illustration of B n ( ) on plasma surface from mmVALEN for NSTX shot 133775 (t=0.655s) single mode response, total B n multi mode response, total B n B n from wall, multi mode response toroidal poloidal J. Bialek outboard inboard outboard inboard outboard inboard
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