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Novel Aspects of ITER Plasma Control

Novel Aspects of ITER Plasma Control. D.A. Humphreys 1 , G.L. Jackson 1 , R. Hawryluk 2 , E. Kolemen 2 , D. Moreau 3 , A. Pironti 4 , G. Raupp 5 , O. Sauter 6 , J. Snipes 7 , W. Treutterer 5 , F. Turco 8 , M.L. Walker 1 , and A. Winter 7 General Atomics, San Diego

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Novel Aspects of ITER Plasma Control

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  1. Novel Aspects of ITER Plasma Control • D.A. Humphreys1, G.L. Jackson1,R. Hawryluk2, E. Kolemen2,D. Moreau3, A. Pironti4, G. Raupp5,O. Sauter6, J. Snipes7, W. Treutterer5,F. Turco8, M.L. Walker1, and A. Winter7 • General Atomics, San Diego • Princeton Plasma Physics Lab, Princeton • Commisariat a l’Energie Atomique, Cadarache • CREATE/Univ. of Naples, Naples • Max Planck Institut fur Plasmaphyzik, Garching • CRPP-EPFL, Lausanne • ITER International Organization, St. Paul lez Durance • Columbia Univ., New York • Presented at the • 55th Annual APS Meeting • Division of Plasma Physics • Denver, Colorado • November 11–15, 2013 084-13/DAH/jy

  2. Novel Challenges of ITER Control Require Novel Solutions • ITER control is different from present devices in several important ways: • Highly robust control required • Model-based control designs • Simulations verify every discharge before execution • Exception Handling: fault responses for low disruptivity • Progress has been made, but substantial control research remains to be done before ITER operates: • Control physics: specific physics knowledge for robust control • Control mathematics: specific algorithmic solutions to satisfy ITER performance and robustness requirements 084-13/DAH/jy

  3. Novel Elements in the ITER Plasma Control Development Process Include Model-Based Design and Shot Verification Actuator Effects Scenarios and Physics Understanding Diagnostic Responses Control Schemes Models Algorithms Exception Handling Continuous Control PCS Implementation Verification Simulations Experiments/Validation 084-13/DAH/jy

  4. The Plasma Control Development Process Includes Equal Measures of Physics Knowledge and Mathematics Solutions Actuator Effects Scenarios and Physics Understanding Diagnostic Responses Physics Control Schemes Models Algorithms Exception Handling Continuous Control PCS Implementation Verification Simulations Experiments/Validation 084-13/DAH/jy

  5. The Plasma Control Development Process Includes Equal Measures of Physics Knowledge and Mathematics Solutions Actuator Effects Scenarios and Physics Understanding Diagnostic Responses Physics Control Schemes Models Mathematics Algorithms Exception Handling Continuous Control PCS Implementation Verification Simulations Experiments/Validation 084-13/DAH/jy

  6. Axisymmetric Control is Well-Advanced But Requires Some Additional Research • Actuators and Scheme: • SC PF coils, Cu vertical control coils • Boundary scheme: plasma-wall gaps • Vertical stability scheme: velocity control • Used in continuous discharge control AND many exception handling scenarios Cu Vertical Stability (VS) Coils Superconducting PF Coils 084-13/DAH/jy

  7. Axisymmetric Control is Well-Advanced But Requires Some Additional Research JET Model for Plasma Response to Coil Current • Actuators and Scheme: • SC PF coils, Cu vertical control coils • Boundary scheme: plasma-wall gaps • Vertical stability scheme: velocity control • Used in continuous discharge control AND many exception handling scenarios A. Pironti, CREATE Cu Vertical Stability (VS) Coils • Status/Research Gaps: • Many experiments done, but ITER specific not demonstrated • Need model-based algorithms for exception handling • Need robust PF/VSsharing scheme, runaway control Superconducting PF Coils 084-13/DAH/jy

  8. Current Profile Control Has Been Studied on Several Devices But Remains Highly Experimental • Actuators and Scheme: • ECH, NBI, density, loop voltage? • Multipoint q-profile control • Share EC system with MHD control Upper EC Launchers Equatorial EC Launcher • Status/Research Gaps: • Some experiments done • ITER specific candidate not identified and demonstrated • Need robust actuator sharing scheme • Need integrated goals: scenario/kinetic and stability control NBI 084-13/DAH/jy

  9. Current Profile Control Has Been Studied on Several Devices But Remains Highly Experimental JET q-Profile Control • Actuators and Scheme: • ECH, NBI, density, loop voltage? • Multipoint q-profile control • Share EC system with MHD control D. Moreau, CEA Safety factor Upper EC Launchers Start of Control Equatorial EC Launcher • Status/Research Gaps: • Some experiments done • ITER specific candidate not identified and demonstrated • Need robust actuator sharing scheme • Need integrated goals: scenario/kinetic and stability control NBI End of Control • q-profile regulated using LHCD, NBI, ICRH 084-13/DAH/jy

  10. Divertor Control Experiments Have Been Performed But Research is Still Needed for ITER Solutions • Actuators and Scheme: • Fueling pellets and local impurity gas injection (N, Ne, Ar?) • Integrated regulation of core and divertor radiation to minimize target heat flux • Maintain partial detachment Fueling pellet launcher • Status/Research Gaps: • Limited experiments • No ITER solution • Need model-based exception handling • Need robust actuator sharing scheme • Need integrated goals: scenario/kinetic and divertor control Divertor Ne gas puff 084-13/DAH/jy

  11. Divertor Control Experiments Have Been Performed But Research is Still Needed for ITER Solutions DIII-D Divertor Detachment Control • Actuators and Scheme: • Fueling pellets and local impurity gas injection (N, Ne, Ar?) • Integrated regulation of core and divertor radiation to minimize target heat flux • Maintain partial detachment E. Kolemen, PPPL Fueling pellet launcher No Detachment Control (#153814) • Status/Research Gaps: • Limited experiments • No ITER solution • Need model-based exception handling • Need robust actuator sharing scheme • Need integrated goals: scenario/kinetic and divertor control Divertor Ne gas puff Detachment Control (#153815) • Divertor Thomson measures detachment • D2 gas injection to regulate partial detachment state 084-13/DAH/jy

  12. Burn Control Has Been Studied Minimally in Experiments and Requires Significant Research for ITER Solutions • Actuators and Scheme: • Fueling species balance, transport control (RMP coils?) • Integrated regulation of kinetic operating point and burn state RMP Coils Fueling pellet launcher • Status/Research Gaps: • Limited experiments • No ITER solution yet • Need model-based exception handling • Need integrated goals: scenario/kinetic and burn control 084-13/DAH/jy

  13. Burn Control Has Been Studied Minimally in Experiments and Requires Significant Research for ITER Solutions DIII-D Burn Control Experiment • Actuators and Scheme: • Fueling species balance, transport control (RMP coils?) • Integrated regulation of kinetic operating point and burn state R. Hawryluk, PPPL bn RMP Coils n=3 RMP coil current (kA) Fueling pellet launcher • Status/Research Gaps: • Limited experiments • No ITER solution yet • Need model-based exception handling • Need integrated goals: scenario/kinetic and burn control Pinj (MW) • n=3 RMP coils used to modify transport • βN controlled during NBI power surge (red) emulating burn excursion 084-13/DAH/jy

  14. ITER Tearing Mode Control Involves Multiple Control Goals and Integrated Sharing of Many Actuators • ITER TM Control Scheme Includes: • Profile/kinetic control to maintain distance from controllability boundary • Continuous (periodic) sawtooth control • Continuous (periodic) TM suppression: repeated “Catch and Subdue” • Exception handling response to off-normal TM • TM control involves complex sharing of actuators and integrated control goals: • 24 gyrotrons, 20 MW total: shareable between upper/equatorial launchers • 33 MW NBI, 20 MW ICRF, transport (burn) control for beta and profile regulation • Active sawtooth and TM control with ECH/ECCD Upper EC Launchers Equatorial EC Launcher NBI 084-13/DAH/jy

  15. Tearing Mode Continuous Control in ITER Enables Multiple Catch and Subdue Events Simulated ITER 2/1 Catch and Subdue • Continuous active suppression scheme: “Catch and Subdue” • Maintain mirror alignment near resonant surface… • As soon as mode grows beyond noise threshold, align to island and turn on ECCD power before saturation (“Catch”) • Fully suppress (“Subdue”) mode, turn off ECCD • Repeat as necessary • Periodic, as-needed ECCD minimizes average power ρq ρdiag ρEC PECCD (MW) wISLAND (cm) DIII-D Catch and Subdue 084-13/DAH/jy

  16. Continuous Tracking of Alignment Enables Rapid Suppression of Later Events and Low Average Power • Active tracking of alignment after mode suppressed • Seed islands triggered by sawtooth, ELMs are immediately suppressed • CW suppression  12 MW average power • Catch/Subdue  1 MW average power 084-13/DAH/jy

  17. Degree of Novelty and Research Needed Varies Widely Among ITER Control Categories Mature, ITER-relevant Candidate ITER solutions Limited ITER-relevant experiments Limited ITER solutions Limited ITER-relevant experiments 084-13/DAH/jy

  18. Degree of Novelty and Research Needed Varies Widely Among ITER Control Categories 084-13/DAH/jy

  19. Degree of Novelty and Research Needed Varies Widely Among ITER Control Categories 084-13/DAH/jy

  20. Much Progress Has Been Made But Novel Aspects of ITER Control Require Ongoing Plasma Control Science Research • Control Physics: • Good progress made in physics understanding needed for control • Further advances needed in highly novel areas including divertor, burn, tearing mode, current profile control • Control Mathematics: • Many candidate control algorithm solutions have been proposed • Quantified controllability and effective exception handling algorithms needed to maximize physics productivity and prevent disruptions • Integrated solutions and experimental demonstrations: • Methods for integrating control goals and robustly sharing actuators • Many specific solutions remain to be qualified on operating devices 084-13/DAH/jy

  21. Additional Slides 084-13/DAH/jy

  22. Catch and Subdue Events Must Be Rapid Enough and Infrequent Enough to Maintain Fusion Gain Q~7 for 2/1 stabilized with 20 MW CW at HH=1.0 Q = PFUS/PEXT 3/2 2/1 Reduced Q due to confinement loss from unstabilized saturated islands O. Sauter, PPCF 52 (2010) 025002 084-13/DAH/jy

  23. Accomplishment of ITER Control Requires a Sophisticated Exception Handling System Exception Handling Will Use a Finite State Machine Architecture • Exceptions: • Off-normal event requiring a change in control • Prediction by forecasting system • Direct detection • Exception handling policy includes: • Relevant plasma/system context (e.g. stored energy, saturation state of actuators) • Specific signals to be predicted or detected • Control modification response to exception: command waveforms, algorithm characteristics… Research is Required to Prevent Explosion in Complexity 084-13/DAH/jy

  24. ITER Exception Handling System Requires a Powerful Forecasting Capability for Sufficient Look-Ahead ITER PCS Forecasting System Functional Block • Forecasting Outputs: • Controllability thresholds to trigger Exception Handling response • Quantified Risk of disruption to trigger Disruption Mitigation System (> 10-20 ms before) System Health Projection Faster Than Realtime Simulation Realtime Stability/ Control Boundaries 084-13/DAH/jy

  25. ITER Control Will Depend Critically on Full Pulse Schedule Verification and Validation via Simulation ITER Plasma Control System Simulation Platform Architecture Likely Similar to Structure of Pulse Verifier • Verification of pulse schedule: • Pulse schedule = set of program waveforms and control characteristics that define the pulse execution • Verify consistent with administrative limits and requirements • Verify consistent with experiment goals • Validation of control performance: • Confirm sufficient nominal control for scenario • Confirm sufficient controllability in presence of “expected” exceptions PCSSP ITER Plant Simulator ITER PCS Simulator PCS Development 084-13/DAH/jy

  26. ITER Control will Depend Critically on Full Pulse Schedule Verification and Validation via Simulation ITER Plasma Control System Simulation Platform Architecture Likely Similar to Structure of Pulse Verifier • Verification of pulse schedule: • Pulse schedule = set of program waveforms and control characteristics that define the pulse execution • Verify consistent with administrative limits and requirements • Verify consistent with experiment goals • Validation of control performance: • Confirm sufficient nominal control for scenario • Confirm sufficient controllability in presence of “expected” exceptions PCSSP ITER Plant Simulator ITER PCS Pulse Validation 084-13/DAH/jy

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