Optimization of Stationary High-Performance Scenarios

Optimization of Stationary High-Performance Scenarios Presented by T.C. Luce National Fusion Program Midterm Review Office of Fusion Energy Science Washington, DC September, 6 QTYUIOP 8-6/TCL/rs

Strategy for Optimizing Tokamak Performance The program strategy is to determine the operational limits and establish the scientific basis for design choices in future tokamaks (Fusion Performance) β Advanced Inductive Current Limit Conventional Tokamak Steady State β β N = N = 5 β P (Bootstrap Current) Equilibrium Limit Conventional tokamak scenarios (like the ITER baseline scenario) run at relatively low pressure near the current limit Advanced inductive scenarios have higher pressures, but still are close to the current limit Steady-state scenarios move away from the current limit to maximize the self-driven bootstrap current and push toward the pressure limit to maximize fusion performance without current drive 8-6/TCL/rs

Advanced Scenarios Under Development in Are Uniquely Associated with Distinct Current Profiles 5 Optimization objectives: q Steady State High q min High l i Conventional Advanced Inductive or Hybrid Steady state True steady-state operation at high fusion energy gain Advanced inductive or hybrid Maximum fusion power, maximum fluence per inductive pulse (increased duty cycle)... ρ.6.8. 8-6/TCL/rs

Optimization Strategy Provides Essential Information for ITER Operation and Beyond Toward ITER needs: advanced inductive scenario research indicates ITER has significant margin to achieve its Q fus = goal and may be able to pursue a limited nuclear testing program steady-state scenario research is working toward establishing the operational basis for noninductive performance with Q fus 5 in ITER Beyond ITER: The program seeks to provide input on a crucial issue for DEMO whether to continue with designs for high gain with inductive current drive or jump directly to a design optimized for steady-state operation The program is striving to provide the essential scientific basis for optimization of tokamak design (double null vs single null, current profile, shape,...) for other uses of fusion (CTF, H production,...) 8-6/TCL/rs

Outline In this talk, three research areas will be addressed: Steady-state scenarios Control tools and methods Advanced inductive or hybrid scenarios In each area, the following points will be addressed: Goals envisioned in the 8 proposal Progress achieved toward these goals Adaptations of the research plan will be discussed in the summary Modeling is a key element in the progress achieved in all areas, but the time is insufficient to describe the progress and how it was achieved 8-6/TCL/rs

Status of Steady-State Scenario Development in (kev).5..5. 8 I p (MA) l i P inj ( MW) β N T i () Time (ms) n e ( m ) M.R. Wade, IAEA Post-deadline oral M.R. Wade et al., Nucl. Fusion, 6 () ECCD Power (au) q min q T e () f NI 9%, f BS 6% (see packet material) β N =., H 89 =., t dur > 5 τ E Duration limited by slow evolution of the remaining inductive current Stationary, full noninductive operation requires an increase in β to increase f BS and an increase in ECCD to maintain stable current profile (see packet material) 8-6/TCL/rs

Fully Noninductive Current Achieved With Increased β Flux Surface Averaged Toroidal Current Density (A/cm ) 5 5 J(ρ) J ind J tot MEASUREMENT (Eq. Measurement) 5....6.8. RADIUS, ρ Flux Surface Averaged Toroidal Current Density (A/cm ) 5 5 J(ρ) J NB J EC J boot J tot ANALYSIS 96F5 5....6.8. RADIUS, ρ Measurements: f ind =.5%, f NI = 99.5% Analysis shows: f BS =59% f NB =% f EC = 8% f NI = 98% Key element was feedback control of non-axisymmetric magnetic fields Discharge is still not perfectly stationary (t dur <.5 τ R ) more ECCD power with optimized profile required Murakami, APS 5 Invited Talk M. Murakami, et al., Phys. Plasmas, 566 (6) 8-6/TCL/rs

Steady-State Scenario Development Goals Listed in the Five-Year Program Plan Integrate high stability and current sustainment Extend duration to > τ R Optimize full noninductive scenarios (fusion performance and gain) Pumped, high-triangularity lower divertor to allow single-null vs double-null comparison Integrate solutions for heat flux reduction (e.g. radiative divertor) Integrate ELM mitigation solutions Investigate % bootstrap solutions (requires β N 5) 8-6/TCL/rs

Experiments Have Demonstrated Performance Required for an ITER Steady-State Scenario Normalized fusion performance, G.5.... ITER Q~5 steady-state scenarios - -5...5. Average noninductive current fraction, f NI The ability to approach stationary noninductive conditions at parameters relevant to fusion energy is a unique capability of It still remains to explore conditions with overdrive, as this will be necessary for control of high performance noninductive discharges Murakami, APS 5 Invited Talk M. Murakami, et al., Phys. Plasmas, 566 (6) 8-6/TCL/rs

Early Shape Optimization Experiments Showed the Largest Improvement in β Came From Single Null to Double Null...8.6 β N Double Null Higher δ Single Null 5. 5. 5.8 6. q 95 I/aB (MA/mT) Significant improvement observed in changing from single null to double null (confirmed in pumped longer-pulse discharges this yearsee packet) Little improvement observed with more triangularity at fixed elongation Experiments validated plan to install lower divertor symmetric to the existing upper divertor Pressure limits probed transiently without pumping J. Ferron, APS Invited Talk J. Ferron, et al., Phys. Plasmas, 566 (5) 8-6/TCL/rs

Recent Optimization of Plasma Shape Leads to Stable Operation at Higher β and Higher Confinement 5 H 89.5..... β N β H /q N 89 95 ITER baseline target 5 Time (ms) Optimal shape has both higher sustained pressure and higher confinement Elongation and triangularity are fixed; outer squareness is varied this quantity does not appear in any empirical scaling Best case approaches the ITER Q fus = target conditions C. Greenfield, IAEA 6 Talk 8-6/TCL/rs

Early q Profile Optimization Experiments Showed the Achievable Pressure Decreases with Increasing q min β N..5. Transient Maximum Experimental β N Long duration The no-wall, long-pulse, and transient pressure limits all drop with q min This correlation implies the expected gain in f BS at higher q min may be offset by a lower pressure pressure limit.5. Measured no-wall β N limit.5..5 q min J. Ferron, APS Invited Talk J. Ferron, et al., Phys. Plasmas, 566 (5) Experiments are planned to see if this result applies generally to all shapes Preliminary experiments with an alternate optimization (high l i ) also transiently exceed β N = (see packet) 8-6/TCL/rs

Exploration Experiments Seeking Higher Pressure (β N > ) Have Begun.5..5..5 Time (s) t=.87 s J BS J ll 5 J NB MHD stability studies indicate that broader current profiles should have higher pressure limits (β N 5) Ramping down the toroidal field results in an off-axis inductive current drive, giving broader current profiles transiently -5 - J EC J TRANSP OH J VLOOP OH Initial experiments combined with a plasma current ramp-up and active RWM control have reached β N > A. Garofalo, APS 5, Invited Talk A. Garofalo, et al., Phys. Plasmas, 56 (6) 8-6/TCL/rs

Progress Toward Steady-State Scenario Development Goals Listed in the Five-Year Program Plan Integrate high stability and current sustainment (ongoing) Extend duration to > τ R (pending EC power increase) Optimize fully noninductive scenarios (fusion performance and gain) Pumped, high-triangularity lower divertor to allow single-null vs double-null comparison (experiments underway) Integrate solutions for heat flux reduction (e.g. radiative divertor) (achieved in advanced inductive) Integrate ELM mitigation solutions (experiments underway in advanced inductive) Investigate % bootstrap solutions (requires β N 5) (theory scoping study and experiments on tools started) 8-6/TCL/rs

Goals for Control in Advanced Scenarios for 8 Particle control maximize ECCD, maximize steady-state fusion gain Install high-triangularity lower divertor q profile control optimize scenario performance, maintain optimal operating point Increase FW and EC power Increase electron β (for bootstap enhancement) Closed-loop control of q() β control operate reliably close to pressure limits Simultaneous rotation and β control Rotation control establish transport and physics basis for rotating and non-rotating plasmas Closed-loop control 8-6/TCL/rs

Status of Control for Advanced Scenarios in Particle control Upper single-null discharges achieved high performance with pumping Highly shaped lower single null or double null could not be pumped q profile control No real-time control possible β control Routine use of closed-loop control of β N available Rotation control No real-time control possible (Instability control is discussed elsewhere) 8-6/TCL/rs

Specialized Experiments Were Performed to Demonstrate the Effectiveness and Physics of Pumping Double-Null Discharges..8 Γ UP-BAF /Γ DN-BAF LSN DN USN Pumping Particle control was effective in double-null with both outer legs pumped.6...9 -. -.5.5. drsep.6 (cm) B B ion drift direction toward the lower divertor T. Petrie, et al., Nucl. Fusion 6, 57 (6) B B ion drift direction toward the upper divertor B B B B drsep ~ Inner leg pump contributes little in true double null Drift direction is important for particle balance in double null 8-6/TCL/rs

Initial Experiments in 6 with Pumped Double Null Have Recovered the Highest Sustained Performance with Modest Density Control 8 6..5 n ( 9 m ) 999 6.5 I (MA) 999 6 β N in the pumped shape is as high as previously achieved in stationary plasmas Density increasing in the unpumped case, but decreasing in the pumped case. l i 999 6 Present density is sufficient for ECCD access, but further optimization of pumping is planned Time (ms) Lower Divertor Modification 8-6/TCL/rs

Closed-Loop Control of q() Evolution Using Off-Axis ECH is Effective in the Current Ramp P EC (MW) Resonant at ρ =. 579 58 58 Closed-loop control employs real-time equilibrium reconstruction including MSE data every ms 6 5 5 5 q() No EC reference Minimum power for EC feedback End of current ramp Target value 5 5 Time (ms) Control works during L-mode current ramp; insufficient EC power to maintain target in flattop Two different targets reproduce good (red) and degraded (blue) breakdown conditions J. Ferron, et al., Nucl. Fusion 6, L (6) 8-6/TCL/rs

q min has been Controlled to High Values for Long Duration Using Neutral Beam Heating in H-mode..5..5...5..5..5. 8 6 q min Feedback Begins β N P beam (MW) Plasma Current Ramp Measured Feed Forward + Gain *Error 5 5 Time (ms) Feed Forward Power 9 Target Control works in ramp-up and flattop Large power demand on NBI can drive the plasma to β limit Control of q min and q() - q min probably not possible with only NBI 5 J. Ferron, et al., Nucl. Fusion 6, L (6) 8-6/TCL/rs

Development of a Controller to Generate Target q Profiles for Advanced Scenarios is Proceeding via Significant Collaborations q min NBI Current Density (A/m ) 5..5..5..5..5. 5.5..5..5..5...5. Shot CRONOS, Modified NBI CRONOS, Original NBI EFIT.5..5. Time (s) Modified Original.....5 ρ.6.7.8.9. Reproducible and automatic generation of the desired target q profile will be a key enabling technology for advanced scenarios CEA-Cadarache has supplied the CRONOS simulation code which has the capability to test closed-loop control schemes on a variety of plasma models ( man-months) at GA in 6 initiated through ITPA) SWIP (China) supplied 8 man-months in 6 of experienced modellers to help analyze data and compare models (initiated through ITPA) Lehigh U. personnel have spent man-months building a fast poloidal flux evolution simulator and testing open-loop target generation schemes (see packet) 8-6/TCL/rs

Goals for Control in Advanced Scenarios for 8 Particle control Install high-triangularity lower divertor (complete) q profile control Increase FW and EC power (ongoing) Increase electron β (for bootstap enhancement) (pending EC and FW power upgrade) Closed-loop control of q() (initial experiments successful) β control Simultaneous rotation and β control (initial experiments successful) Rotation control Closed-loop control (initial experiments successful) 8-6/TCL/rs

Status of Advanced Inductive or Hybrid Research in 5 5 I p (x MA) P NB (MW) P NB (MW) n= Mirnov (G) l i β N n ( 9 m ) Φ D / (torr l/s) Z c 6 8 Time (ms) Discharges with β N H 89 ~ 7 were demonstrated with Stationary current profiles (t dur > τ R ) Stationary pressure profiles (t dur > 5 τ E, H 89 =.5) No wall pumping No impurity accumulation (Z eff =.6) At q 95 =.-.5, β N H 89 /q 95 =.8., (ITER-FEAT Q fus = design value.) 8-6/TCL/rs

Five-Year Program Plan Goals for Advanced Inductive Scenarios While this mode of operation was established at the beginning of the present program plan, no explicit strategy was given This is an area where significant adaptation to technical progress and favorable response from the ITER team and the international community has led to expansion of the original plan 8-6/TCL/rs

Performance at or Above ITER Baseline Design Has Been Achieved Over a Wide Range in q 95 5 5..5. 99 586 5 I P (MA) ) I P (MA) ) P ) NB (MW) 5 P NB (MW) β β N N l l i i ITER Baseline Scenario ITER Baseline Scenario H 89P H 89P ITER Baseline Scenario ITER Baseline Scenario G ITER Baseline Scenario. G.5 ITER Baseline Scenario. 5 6 5 6 Time (s) Time (s) q 95 =. q 95 =. no-wall no-wall β N β N β N > ~.8 β N G G ITER G.5 G ITER No sawteeth Small sawteeth T. Luce, APS Invited Talk T. Luce, et al., Phys. Plasmas, 66 () 8-6/TCL/rs

Experiments Have Demonstrated High Performance Operation For >9 Current Relaxation Times (G).5 I P (MA)..5. 5 5 5..5. ~ n = B rms ~ n = B rms τ E H 98y τ R H 89 β N n e ( 9 m ) Z eff (ρ =.5) P NBI (MW/) 6 8 Time (s) M. Wade, IAEA Talk M. Wade, et al., Nucl. Fusion 5, 7 (5) β T D α β T % β N.7 H 89P =. H 98y =. Z eff =. 8-6/TCL/rs

.5..5 q_95..5 5. Fusion Performance Maximizes at Low q 95 ; G G ITER at q 95 =.5 β N All sustained for at least τ R.8.6 G = β N H 89 /q 95. ITER Baseline Sawteeth No Sawteeth.. ITER Baseline.5..5 H 89 H 98y ITER Baseline..5..5 q 95..5 5. Density scan also completed (see packet)..5.5..5..5 5. q 95 ITPA Joint Experiment M. Wade, IAEA M. Wade, et al., Nucl. Fusion 5, 7 (5) 8-6/TCL/rs

Ability to Suppress the / Tearing Mode with ECCD Demonstrates Its Essential Role in Maintaining Stationary Current Without Sawteeth No / mode With / mode Co-ECCD suppresses / mode Ctr-ECCD enhances / mode 5 5 5 5 ~ n = B rms (G) EC On EC On ~ n = B rms (G).. 5. Time (s) Sawteeth Sawteeth 6. 7. q ().5..5. Co ECCD.95... Before ECCD W / (m) Counter ECCD.6.8. M. Wade, IAEA Talk M. Wade, et al., Nucl. Fusion 5, 7 (5) Direct MSE measurements across an ELM crash show the importance of ELMs (see packet) 8-6/TCL/rs

Radiative Divertor Operation Has Been Achieved in Advanced Inductive Scenario Discharges 5 5 8 n ( 9 /m ) H 89P β N Current x (MA) P NB (MW) P rad /P NB P NB (MW) P rad (MW) D flow (torr l/s) Ar flow (torr l/s) 75 ~ B (n=) (G) ~ B (n=) (G) 6 8 Time (ms) Impurity gas used is argon Strong D flow in the SOL required to get divertor argon enrichment Peak heat flux in the divertor was reduced by nearly a factor of Pressure limit not determined Modest reduction in confinement See M. Fenstermacher talk for details of the divertor operation 8-6/TCL/rs

Systematic Scan of Counter-NB Power Shows the Influence of Rotation on Advanced Inductive Scenario 5 5 5 f tor (ρ=.5) (khz) P NB (MW) Rotation varies by a factor of 5 T NB (N.m) Confinement drops by ~% as rotation drops (not compensated for first orbit losses) 5 H89P β N =.6 and density held constant by feedback control 5 5 5 55 6 Time (ms) 8-6/TCL/rs

Program Goals for the Remainder of the Five-Year Program Plan for Advanced Inductive Scenarios Work toward establishing the physics basis for the existence of stationary current profiles with high tearing mode pressure limits Effects of tearing modes and ELMs on J() Measurements of fast ion distribution Modeling of poloidal flux evolution Understanding of what initial conditions are necessary and sufficient to access high performance Work toward establishing the physics basis for transport extrapolations to burning plasmas ρ * scaling Rotation effects T e /T i effects Note: These goals are closely aligned to the ITPA/IEA Joint Experiment goals 8-6/TCL/rs

Summary Research in the area of stationary high-performance scenario development has made significant progress since. Delays in pulse extension experiments due to source limitations of the EC and FW systems have been compensated by accelerating work in the control and optimization areas Additional scope has been added in the area of advanced inductive or hybrid scenarios in recognition of the potential uses in ITER The work on all advanced scenarios has been substantially enhanced by the international cooperation fostered by the ITPA. Sharing of personnel, analysis tools, and results among several tokamaks has benefited the research program 8-6/TCL/rs

Additional Material Referenced But Not Presented

Current Balance Calculation from Steady-State Case Indicates Direction for Stationary Noninductive Discharge % more noninductive current required for current balance Bootstrap and ECCD required at ρ=.6. to maintain stable current profile (MA/m )..8.6. Noninductive Current Fractions f NI (exp) ECCD + NBCD + Bootstrap ECCD + NBCD (MA/m ) 6 t =.7 s t =.7 s J OHM.. 5 ECCD 5 5 Time (ms)....6.8. Normalized Radius M.R. Wade, IAEA Post-deadline oral M.R. Wade Nucl. Fusion, 6 () 8-6/TCL/rs

Advanced Tokamak Research Plan from Five-Year Program Plan MHD control for high β N Wall stabilization (RWM) Rotation Active feedback stab. Magnetic island stabilization (NTM) Optimal shape for high, β Shape β N, and density control 5 6 7 8 β β N >> no wall N with rotation m/n = / stab. β Critical rot. velocity Physics of rot. stab. Effect of rotation n= feedback Physics of error field amplification Enternal coils Internal coils Optimization and exploitation β > βno wall N m/n = / stab. and optimize β m/n = / stab. Stabilize multiple modes and density control studies Exploitation Lower pumped Optimal mode spectra coils and sensors, low rotation Hi δ double null Current profile control for high β and high bootstrap Off-axis control Validate ECCD physics Optimize driven current Increase βe FWH and elec. transport Sustain high q min discharges Central control q, magnetic shear FWCD coupling Feedback control q Increase power Extend duration ( seconds) Bootstrap Evaluate self-consistent profiles High performance, high bootstrap (~%) Pressure profile for high β N, H, f BS Transport control (E B) Non-axisymmetric RF heating Rotational control fields with counter-nbi QDB Transport control (Shafranov shift) ECH/ECCD to modify and control Evaluate Current holes High β, high bs, high H demonstration Localized ECH Integrate high β stab., & current sustainment Low rotation, separate E B and α Boundary control Density and impurity control Establish need for DND pump Mass flows and transport Optimized divertor Heat flux reduction QH-mode HFS pellet Pedestal optimization Validate MHD models Measure J edge QH-mode Understand EHO Broaden E r with counter-nbi Fueling HFS, pellet Ergodization Evaluate, modeling, I-Coils Design optimal coil set Implement Steady state Extend duration to t dur > t CR Optimize Increase β & f BS 8-6/TCL/rs

Strong Coupling Exists Between Hardware Improvements and Development of Steady-State Scenarios EC Ctr NB FW Control Current profile RWM Sawtooth Rotation profile Density ELMS Optimization Physics Basis RWM stability w/out rotation Transport scaling SN/DN comparison I-coils Lower Divertor Long Pulse 8-6/TCL/rs

Progress Toward the Goal of Noninductive Operation for > τ R.. f NI Full time-dependent profile analysis carried out.8.6.. Profile DB f BS.....6 tdur /τ R.8. Performance limits set by MHD stability Duration limits set by ECCD ability to supply the necessary off-axis current Murakami, APS 5 Invited Talk M. Murakami, et al., Phys. Plasmas, 566 (6) 8-6/TCL/rs

Pumped Double Null Allows Significantly Higher Sustained Performance than Pumped Single Null 5.5..... β N H 89 ITER steady-state target ITER baseline target β N H 89 /q 95 5 Time (ms) Sustained higher β operation is demonstrated Higher confinement quality is obtained at higher β Both shapes yield fusion gain parameters at or above the ITER steady-state target Density control from new divertor enables better ECCD efficiency -6/TST/rs

High l i Steady-State Scenario Has Been Tested Transiently..5..5. 5 l i H 89 β N Elongation l i 55 l i increase by fast κ ramp Maximum l i limited by q= and rise of pedestal current β N ~ l i as expected (no wall stabilization) β limited by fast growing instability Confinement enhancement correlated with l i as expected.6.8.. Time (s)..6.8. 8-6/TCL/rs

Many Improvements Have Been Made in the Plasma Control System Since New hardware and diagnostic acquisition Thomson scattering n e and T e profiles CER rotation and T i profiles channel T e profile from ECE 9 khz control cycle frequency for RWM feedback More than doubled real-time CPU power to > CPUs Real-time display of the discharge boundary New real-time analysis and control algorithms Real-time equilibrium reconstruction with MSE for q profile NTM control including active tracking of the resonant q Feedback control of q() or q min evolution Real-time calculation of beta from the equilibrium reconstruction Simultaneous control of beta and toroidal rotation Control of T e at two locations simultaneously using ECH Advanced shape controller (MIMO) demonstration PCS technology in use at NSTX, MAST, EAST, KSTAR, Pegasus In preparation Real-time spectrum analysis of fluctuation measurements Modulation of gyrotron power in phase with NTM Increase in the real-time EFIT computation grid resolution to 65 x 65 8-6/TCL/rs

Fusion Gain Metrics Indicate the Rationale for Advanced Scenarios Advanced Inductive Gain P fus /(P loss P α ) Steady-state Gain P fus /P CD β N H q 95 Operation at higher pressure or confinement quality Performance enhancement at fixed q 95 Risk reduction at higher q 95 β N f G Large leverage from operation at higher pressure Significant benefit from density control f G n/n Greenwald C CD ( C BS β N q 95 ) Motivation for higher q 95 8-6/TCL/rs

First-Generation Open Loop Target q Optimizer Will Be Tested in Upcoming Experiments I (MA)...8 8..5..5..5 Time (s) n ( 9 /m ).5......9.8..5..5..5 Time (s). Optimizer tries many variations of the time history of the three actuators modeled Power, current, density Suggested open-loop trajectories will then be coded into the PCS for testing on P (MW) 6 Z.. Closed-loop feedback control β also under study. Target Calculated..5..5..5 Time (s)......5.6.7.8.9. Radius ρ 8-6/TCL/rs

Transformerless Operation Shows Control of High Bootstrap Fraction Plasmas Will Be Challenging 5 5.7 I (MA) P NB (MW) <P NB > (MW) 9787 The desired steady-state operating point may not be a stationary solution to the coupled fluid equations. If not, active control is required.6.5 l i H 89 Inductive control of the plasma current may be desirable noninductive overdrive will be required q min β N At high safety factor (q 95 ~) and high q min (~), the bootstrap current fraction achived here is >8% 5 6 Time (s) 8-6/TCL/rs

Strong Coupling Exists Between Hardware Improvements and Tools Needed to Establish the Physics Basis for Advanced Inductive Scenarios EC Ctr NB FW Stability Why is the / mode more stable? What role does the / mode play? Transport What roles do rotation, T e /T i, magnetic shear play in good confinement? What are the transport scalings? Pedestal/SOL/Divertor What role do shape and q 95 play a divertor heat load? Is a radiative divertor compatible with this scenario? Improved diagnostics Long pulse Lower divertor 8-6/TCL/rs

Fusion Performance Weakly Dependent on Plasma Density..5..5. β N H 89 { H 98y { ITER Baseline ITER Baseline.5....6.8. n e /n GW.8.6.. ITPA Joint Experiment q 95 =. q 95 =.5 G = β N H 89 /q 95 ITER Baseline.....6.8. n e /n GW All discharges are at stationary (>τ R ) β limit M.Wade, IAEA Talk M. Wade, et al., Nucl. Fusion 5, 7 (5) 8-6/TCL/rs

Time-Resolved MSE Measurements Through the ELM Cycle Indicated the Key Role of ELMs and Tearing Modes q = /.. 76 q = / Change across the ELM crash is shown 5.. ΔB z (mt)..... Δq q at small radius increases when the ELM crashes Bootstrap current near the tearing mode increases indicating shrinkage of the island at the crash...... Δ J CD (MA/m ) Δ J BS (MA/m ).....8...8 ρ ρ C. Petty, Phys. Rev. Lett. in preparation 8-6/TCL/rs

Comparison of Hybrid Discharges with Dominant / NTM or Dominant / NTM, Shows the Confinement Impact of the Tearing Modes 9 PNB 6 β N (MW) H 89P Time (s) Dominant / NTM Dominant / NTM 5 6.6.. / Mode (G) / Mode (G) q min 778 775 τ R. 5 6 Time (s) / and / modes compete for same free energy source, so they don t usually co-exist Discharge with dominant / NTM has 5% higher H 89P -Factor Dominant / NTM discharge also has q min < and sawteeth Dominant / NTM discharges only exist for β N <.8 8-6/TCL/rs