THE DIII D PROGRAM THREE-YEAR PLAN

Transcription

1 THE PROGRAM THREE-YEAR PLAN by T.S. Taylor Presented to Program Advisory Committee Meeting January 2 21, 2 3 /TST/wj

2 PURPOSE OF TALK Show that the program plan is appropriate to meet the goals and is well-aligned with the FESAC goals Define and motivate the research elements Thrusts* Topical science* *Thrusts and topical science area details provided in later talks. 3 /TST/wj

3 OUTLINE/SUMMARY The Program is a strong science-based program with a focus on the Advanced Tokamak Two steady-state high performance scenarios are planned High bootstrap fraction (NCS) High l i High bootstrap fraction (NCS) is our near-term primary advanced tokamak scenario Research thrusts have been identified to address key issues for the NCS scenario Topical science research provides broad scientific base International collaboration is an important element of the program 3 /TST/wj

4 THE PROGRAM IS A MISSION ORIENTED SCIENCE PROGRAM Fusion Energy Goal/mission FESAC Goal 3 FESAC Goal 1 and 3 Focus Tokamak Optimization Goals and Thrusts Goal 1 Goal 1 and 3 FESAC Goal 1 and 2 Stability Wave Transport & Particle Edge Physics Goal 2 and 3 Scientific Base Research thrusts are based on (and contribute to) solid scientific base they are expected to lead to the optimization of the tokamak Broad scientific base (topical science) forms foundation for research thrusts and tokamak optimization, as well as contribute to advancing plasma and fusion science on a broad front QTYUIOP -3 /rs

5 FOCUS OF RESEARCH IS ON ADVANCED TOKAMAK PHYSICS Innovative concept improvement of the tokamak } concept toward FESAC Goal #3 Simultaneously integrated FESAC Goal #1 Control tools FESAC Goal #4 High power density 3 Improved stability Compact (smaller) 3 Improved confinement Steady state 3 High bootstrap fraction high β N 3 Current drive and divertor optimization A self-consistent optimization of plasma physics through Magnetic geometry (plasma shape and current profile) Plasma profiles (pressure, density, rotation, radiation) MHD feedback stabilization SAN DIEGO Requires strong coupling between theory, simulation and experiment Challenging and rich scientific research Improved and new physics measurements 3 99/TST/wj

6 ADVANCED TOKAMAK GOAL Program objectives: Establish a firm scientific basis for the optimization of the tokamak approach to fusion energy production FESAC Goal #1 FESAC Goal #4 Goal #3 Strategy: Demonstrate improvements separately, then simultaneously Develop solid scientific understanding and predictive capability β N H 3 Diagnostics 3 Theory/modeling 3 Require strong coupling of theory and experiment Develop control scenarios and tools based on scientific understanding Increase performance and duration 3 Disruption avoidance through control of profiles and active stabilization τ DUR /τ E GOAL 3 /TST/wj

7 SCIENTIFIC UNDERSTANDING IS ESSENTIAL FOR PROGRESS TOWARD ADVANCED TOKAMAK GOAL Details of profiles and geometry are important Strong nonlinear interaction of many physics elements Current profile transport pressure profile current profile Heating deposition pressure profile ω E B transport pressure profile New and improved physics measurements are needed Empirical scaling Integrated modeling Physics Understanding Diagnostic measurements Physics based models (stability, transport, etc.) Global and single point measurements Time dependent profile measurements Turbulence, turbulentdriven transport; 3-D equilibrium 3 /TST/wj

8 NCS AND HIGH l i ARE TWO DIFFERENT APPROACHES TO STEADY-STATE HIGH PERFORMANCE Motivated by steady state energy gain Q P Fus γ cur PFus γcur εeff β2 = N PCD nrip 1 fbs nq 1 ξ A qβn ( ) ( ) High bootstrap fraction (NCS) Off-axis current profile control Pressure profile control (ITB control) as f BS 1 High central current drive (high l i ) High current drive High bootstrap NCS J high i ρ 3 99/TST/wj

9 <J> (MA/m 2 ) Advantages INCREASING H AND β N WITH l i SUGGEST AN ATTRACTIVE ADVANCED TOKAMAK SCENARIO Ease of central current drive High β N, high H observed on many experiments No power threshold Compatibility with ELMing H mode, radiative I mode Challenge: Self-Consistent High β, High li Scenario Total current Bootstrap current ψ 1/2 Limitation Alignment of bootstrap current limits achievable li Low edge J, high Ŝm Reduced edge transport High edge p High edge bootstrap High edge J q o = 1.5 with sawtooth q o =.55 l i = 1.2 stabilization l i = q 95 ~ 8 I BS /I p ~ 5% 6% ECCD and FWCD are primary β N ~ 4 H ~ 2 3 motivates high l i Thrust #6 current drive and sawtooth stabilization tools 3 /TST/wj

10 HIGH BOOTSTRAP FRACTION NCS SCENARIO IS PRIMARY STEADY-STATE HIGH PERFORMANCE ADVANCED TOKAMAK (AT) SCENARIO Reduced current drive requirements with aligned bootstrap is predicted Ozeki et al., Nucl. Fusion 33, 125 (1993) Kessel, Phys. Rev. Lett. 72, 1212 (1994) Manickam, Phys. Plasma 1, 161 (1994) Turnbull, Phys. Rev. Lett. 74, 718 (1995) Reverse Magnetic Shear Improved performance observed experimentally Reduced core transport observed in a number of experiments Highest performance in is in NCS with H mode edge Great progress in understanding the ion transport in internal transport barriers ω E B > γ LIN χ ~ χ Neo < ρ < 1 Challenges remain in understanding electron thermal and particle transport Current profile control and transport barrier control is needed to increase duration Broad pressure profiles and wall stabilization are needed for improved stability ECH is primary tool for off-axis CD Motivates ECH validation Thrust #9 motivates high bootstrap fraction NCS scenario Thrust #2 3 99/TST/wj

11 THE PROGRAM WILL EMPHASIZE TWO ADVANCED TOKAMAK SCENARIOS IN THE NEAR TERM Other thrusts are chosen which contribute to realization of the scenarios and to the broader scientific base HIGH BOOTSTRAP FRACTION ADVANCED TOKAMAK (INTERMEDIATE SCENARIOS) SUSTAIN OPTIMIZE MODERATE PULSE ADVANCED TOKAMAK FESAC ASSESS- MENT Topical science areas provide broad scientific base and contribute to research thrusts and scenarios TRANSPORT/CONFINEMENT STABILITY HEATING AND CURRENT DRIVE (WAVE/PARTICLE) EDGE AND DIVERTOR HIGH l i SCENARIO PHYSICS INTERMEDIATE SCENARIO DEMONSTRATION 3-/TST/rs

12 IMPORTANT FEATURES OF NCS Broad or hollow current profile and broad pressure profile q min > 1 stability to central modes q, q min >> 1 high bootstrap fraction Strong coupling of external modes to wall Well-aligned bootstrap current, edge current (H mode) ITB gives good confinement Requirements Off-axis ECCD Density control Active wall stabilization Edge stability control ITB control Research element ECH/ECCD validation Thrust #2 AT divertor Thrust #8 RWM stabilization Thrust #4 Edge stability Thrust #1 ITB physics Thrust #7 3 /TST/wj

13 PRIMARY INTEGRATED SCENARIO NCS USING OFF AXIS ECCD (ρ ITB ~ ρ qmin ) χ e various models 1 MW (Source) Using ECCD χ i ~ neoclassical inside ρ(qmin) P EC (MW) 7 (1 source) ~ 5 neoclassical at edge P FW (MW) 6.5 Solved for T e, T i, J(r) P NBI (MW) 6.5 Off-axis ECCD I P (MA) 1.6 I BOOT (MA) 1.7 Ne(r) fixed I ECCD (MA) B T (T) 1.95 β (%) 7.5 J tot β N H 89P 3.5 J BS n (1 2 m 3 ).57.5 n/n G.4 J ECCD T i () 15 J NB T e () 8.5 (MA/m 2 ) ρ jy

14 SIGNIFICANT IMPROVEMENT IN LONG-PULSE ADVANCED TOKAMAK PERFORMANCE HAS BEEN ACHIEVED (T#2) Recent emphasis is on increasing the duration of high performance and increasing the fraction of bootstrap current β 4 N H = 9 for 16 τ E 21 goal, β N H > 1, τ dur > 2 s, f BS > 5% 2 ELM-free H-mode ELMy H-mode L-mode edge 5 β N 4 l i H 89 ARIES-RS SSTR ARIES-RS SSTR β N H89p DIII-D Advanced Tokamak Target ARIES-RS Progress Conventional Tokamak β N H 89 P NBI I P D α 2 s 1.2 MA 11 MW f bs = ~ 5% ARIES-RS SSTR τ duration /τ E Time (ms) 29-99/rs

15 THE PATH TO THE NCS AT GOAL LEADS THROUGH MANY STABILITY ISSUES Pressure Profile Broad P (r) Higher H Larger ITB Better Bootstrap Alignment Peaked P (r) Lower H Narrow ITB H mode Edge Broader P (r) L mode Edge More Peaked P (r) Kink Mode β limit { Edge Stability (T1, T5) Neoclassical Tearing (T3) Wall Stabilization (T4) Larger ρ ITB Broader P(r), J(r) (T7) { NCS AT Goal rds/jy

16 WALL STABILIZATION AND PLASMA SHAPING ESSENTIAL FOR HIGH PERFORMANCE ADVANCED TOKAMAK OPERATION β N B T /(I/aB β N ~ 6 with wall stabilization β N ~ 3 without wall stabilization β N Ideal Stability, n = 1, GATO q ρ J TOR B T B p = 25 ( 1 + k 2 ) ( ) β N (%-m-t/ma) β N 1 f BS = C BS ε 1/2 B p 2 4 P FUS B T B T rwall /rwall ~ ~ motivates RWM Thrust #4 motivates optimal divertor shape Thrust #5 3 /TST/wj

17 β N (%-m-t/ma) STABILITY LIMIT IMPROVES WITH INTERNAL TRANSPORT BARRIER WIDTH AND RADIUS Fixed shape DND, q 95 = 5.1, q = 3.2, q min = 2.2 Hyperbolic tangent pressure representation Ideal n = 1, wall at 1.5a P ψ ITB =.36 Half Width W ITB (flux space) β N (%-m-t/ma) P W ITB =.32 Stable Stable Unstable Unstable ITB Radius ψ ITB (flux space) motivates ITB thrust # /RDS/jy

18 Motivation TIME DEPENDENT TRANSPORT SIMULATIONS HELP DEFINE INTEGRATED AT SCENARIOS Optimization of scenarios and identification or capabilities Guide to experimental demonstration of target plasma (Thrust 2) Improve understanding of key physics involved Two approaches to simulations Experimentally based Determine χ e,i from best target discharges, scaling them if necessary based on global scaling expression Replace inductive J OH with J ECH at fixed total power Optimize bootstrap alignment, ECCD and extend duration toward steady state Confidence in predictions improves as experimental discharges more closely approach our goal Transport model based Theory-based models allow temporal evolution of transport coefficients 3-/TT/jy

19 INTEGRATED MODELING IDENTIFIES FULL NON-INDUCTIVE HIGH PERFORMANCE TARGETS P EC (MW) P FW (MW) P NBI (MW) B T (T) I P (MA) I BOOT (MA) I ECCD (MA) β N H n/n G Wall stabilized Wall stabilized 3 /KHB/wj

20 FULL NON-INDUCTIVE SIMULATIONS START WITH RECENT (1999) WELL ANALYZED ADVANCED TOKAMAK DISCHARGE P inj (MW) I p 1 (MA) H 89P β N nebar n e (1 19 m 3 ) T i, T e, (kev), n e (1 19 m 3 ) χ (m 2 /s) T e T i χ e n e χ i. 5 1 Time (ms) 1 χ i,neo Radius, ρ 3-/rs

21 EXPERIMENTALLY OBTAINED HIGH PERFORMANCE SCENARIOS PROVIDE BASIS FOR NEAR-TERM SUSTAINMENT WITH ECCD Safety factor, q (a) q p tot Initial (experiment) t = 1 s (simulation) Total pressure, p tot (1 5 Pa) EXP Simulation P EC (MW) 3 P NBI (MW) I P (MA) I Boot (MA) j tot (MA/m2) j tot (init) P EC = 3 MW t = 1 s. I ECCD (MA).9.14 I OH (MA) β N H 89P j NB j OH j boot jeccd n/n G Density control needed to obtain full non-inductive discharge Radius, ρ 3 /rs

22 DENSITY AND IMPURITY CONTROL ARE CRITICAL FOR EFFECTIVE CURRENT DRIVE I CD T e 1 n (Z e eff + 5) AT divertor enables particle control 25 2 Simulation ( ) P EC = 3 MW; r EC =.48 I p = 1.2 MA I EC, I OH (ka) 15 1 I EC 5 I OH Experiment n e (1 19 m -3 ) motivates AT divertor thrust #8 3-/rs

23 THE 2 ADVANCED TOKAMAK RESEARCH THRUSTS FOR INTERNAL TRANSPORT BARRIER PHYSICS RESISTIVE WALL MODE FEEDBACK AT DIVERTOR RWM STABILIZATION AT AND RADIATIVE DIVERTOR OPTIMAL MODE SPECTRUM ITB AT LARGE RADIUS ADVANCED METHODS HIGH BOOTSTRAP FRACTION ADVANCED TOKAMAK (INTERMEDIATE SCENARIOS) SUSTAIN OPTIMIZE MODERATE PULSE ADVANCED TOKAMAK FESAC ASSESS- MENT ECH/ECCD VALIDATION EDGE STABILITY STUDIES NEOCLASSICAL TEARING- AFFECT MODE EDGE STABILITY CONTROL NTM-CONTROL MODE GROWTH NTM-STABILIZE MODE HIGH l i SCENARIO PHYSICS INTERMEDIATE SCENARIO DEMONSTRATION 3-/RDS/rs

24 PHYSICS ISSUE THRUST Integrated NCS Scenario NCS scenario (2) Current (q) profile control ECCD physics (9) validation Density control AT divertor (8) Radiative divertor and AT divertor (8) n/n G ~.4 Transport/transport barrier control ITB physics (7) Wall stabilization RWM (4) Neoclassical tearing NTM (3) modes (stab) Edge stability control Edge stability (1) physics High δ shaping Optimal edges (5) S N, D N Integrated high l i scenario High l i (6) 3-/TT/jy

25 Thrust 2 (AT Scenario) FOCUS OF THRUST EFFORTS (2) Develop scenario at lower density with divertor pumping Initial off-axis ECCD, validate current drive Thrust 1 (Edge Stability) Focus on data analysis and model development Impact of details of f BS and P on edge stability Impact of q 95 and β on edge stability and coupling to core f BS Detailed comparison of edge stability with JT 6U Develop and improve edge diagnostics Measurement of edge J with Zeeman splitting (Li beam) Improved edge T i and E r measurements with CER Thrust 3 (Neoclassical Tearing Mode Stability Area) Evaluation of polarization drift threshold model Active stabilization with ECCD Continue collaboration with JET and ASDEX to understand basic physics, scaling, and stabilization Thrust 4 (Resistive Wall Mode) RWM physics model evaluation; especially quantifying rotation and stability thresholds Active stabilization Conceptual design for additional stabilizing coils 3 /TST/wj

26 US/JAPAN EDGE STABILITY COLLABORATION VALIDATES THEORETICAL MODELS THROUGH DETAILED EXPERIMENT AND THEORY COMPARISON Use common analysis tools: EFIT for equilibrium reconstruction, BALOO and GATO for stability analysis β N = JT 6 JT-6U β N = 1.6 α (norm. p ) 4 α (norm. p ) ψ N ψ N 3-/TT/jy

27 Thrust 2 (AT Scenario) FOCUS OF THRUST EFFORTS (2) Develop scenario at lower density with divertor pumping Initial off-axis ECCD, validate current drive Thrust 1 (Edge Stability) Focus on data analysis and model development Impact of details of f BS and P on edge stability Impact of q 95 and β on edge stability and coupling to core f BS Detailed comparison of edge stability with JT 6U Develop and improve edge diagnostics Measurement of edge J with Zeeman splitting (Li beam) Improved edge T i and E r measurements with CER Thrust 3 (Neoclassical Tearing Mode Stability Area) Evaluation of polarization drift threshold model Active stabilization with ECCD Continue collaboration with JET and ASDEX to understand basic physics, scaling, and stabilization Thrust 4 (Resistive Wall Mode) RWM physics model evaluation; especially quantifying rotation and stability thresholds Active stabilization Conceptual design for additional stabilizing coils 3 /TST/wj

28 FOCUS OF THRUST EFFORTS (2) (Continued) Thrust 5 (Optimum Edge) Experimental work completed Complete analysis Continue high density, high confinement in divertor topical area and in collaboration with JT 6U Team Thrust 6 (High l i Scenario) Postponed Thrust 7 (ITB) Continue to develop physics basis for controlling ITB to larger radius, using counter-nbi, off-axis ECH, impurity puffing Active collaboration with JET on optimized shear and ITB physics Thrust 8 (Advanced Tokamak Divertor) Characterize new private flux baffle Develop density control for advanced tokamak scenarios (in support of Thrust 2) Develop impurity control with differential flow (puff and pump) Thrust 9 (ECH Hardware and Physics Validation) Commission 4 gyrotron system Validate axial and off-axis current drive physics (NTM, Thrust 2) 3 /TST/wj

29 FOCUS OF TOPICAL SCIENCE AREAS (2) Stability Neoclassical tearing mode physics and stabilization by ECCD Disruption mitigation physics Internal (sawtooth, resistive interchange) stability Wave and particle ECCD physics Collisionality dependence Efficiency vs power density Ray tracing studies Transport Compare theoretical predictions with experimental results Core transport 3 Electron vs ion thermal transport 3 Velocity shear decorrelation of turbulence Edge transport 3 L H transition 3 Pedestal height and width Edge/divertor Impurity control by forced flow Physics of high density high confinement discharges Role of divertor shape 3 /TST/wj

30 INTERNATIONAL COLLABORATION IS AN IMPORTANT ELEMENT OF THE SCIENCE PROGRAM Aimed at addressing outstanding scientific issues Choose those that provide high leverage for Synergistic Complementary Extremely productive for developing physics understanding and predictive capability of common physics models International collaboration has several forms Contribution to international databases Participation and cooperation on experiments 3 Synergistic 3 Complementary Cooperation on analysis and modeling tools 3 Equilibrium reconstruction (JET, JT 6U, START, MAST...) 3 Determination of localized current drive (ASDEX U, JT 6U,...) Detailed experimental comparisons 3 Edge stability (/JT 6U) 3 Radiative improved modes (, JET) 3 /TST/wj

31 SUMMARY The Program is a science program aimed at an energy goal Thrusts advanced tokamak mission-oriented with strong science element Topical science provides broad science base The goals and program plans are well-aligned with the FESAC goals The Program addresses the key issues needed for full non-inductive high-performance tokamak operation The Program plan contributes to the basis for the FESAC fusion program assessment in 24 3 /TST/wj