1. 1 Humphreys/55 th APS-DPP/October 2012 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 1)General Atomics, San Diego 2)Princeton Plasma Physics Lab, Princeton 3)Commisariat a l’Energie Atomique, Cadarache 4)CREATE/Univ. of Naples, Naples 5)Max Planck Institut fur Plasmaphyzik, Garching 6)CRPP-EPFL, Lausanne 7)ITER International Organization, St. Paul lez Durance 8)Columbia Univ., New York Presented at the 55 th Annual APS Meeting Division of Plasma Physics Denver, Colorado November 11–15, 2013 Novel Aspects of ITER Plasma Control 084-13/DAH/jy

2. 2 Humphreys/55 th APS-DPP/October 2012 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. 3 Humphreys/55 th APS-DPP/October 2012 Novel Elements in the ITER Plasma Control Development Process Include Model-Based Design and Shot Verification Scenarios and Physics Understanding Control Schemes Actuator Effects Diagnostic Responses Models Algorithms Continuous Control Exception Handling PCS Implementation Verification Simulations Experiments/Validation 084-13/DAH/jy

4. 4 Humphreys/55 th APS-DPP/October 2012 The Plasma Control Development Process Includes Equal Measures of Physics Knowledge and Mathematics Solutions Scenarios and Physics Understanding Control Schemes Actuator Effects Diagnostic Responses Models Algorithms Continuous Control Exception Handling PCS Implementation Verification Simulations Experiments/Validation Physics 084-13/DAH/jy

5. 5 Humphreys/55 th APS-DPP/October 2012 The Plasma Control Development Process Includes Equal Measures of Physics Knowledge and Mathematics Solutions Scenarios and Physics Understanding Control Schemes Actuator Effects Diagnostic Responses Models Algorithms Continuous Control Exception Handling PCS Implementation Verification Simulations Experiments/Validation Physics Mathematics 084-13/DAH/jy

6. 6 Humphreys/55 th APS-DPP/October 2012 Axisymmetric Control is Well-Advanced But Requires Some Additional Research Cu Vertical Stability (VS) Coils 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 Superconducting PF Coils 084-13/DAH/jy

7. 7 Humphreys/55 th APS-DPP/October 2012 Status/Research Gaps: – Many experiments done, but ITER specific not demonstrated – Need model-based algorithms for exception handling – Need robust PF/VS sharing scheme, runaway control Axisymmetric Control is Well-Advanced But Requires Some Additional Research Cu Vertical Stability (VS) Coils 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 Superconducting PF Coils JET Model for Plasma Response to Coil Current A. Pironti, CREATE 084-13/DAH/jy

8. 8 Humphreys/55 th APS-DPP/October 2012 Upper EC Launchers Actuators and Scheme: – ECH, NBI, density, loop voltage? – Multipoint q-profile control – Share EC system with MHD control Equatorial EC Launcher NBI Current Profile Control Has Been Studied on Several Devices But Remains Highly Experimental 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 084-13/DAH/jy

9. 9 Humphreys/55 th APS-DPP/October 2012 Upper EC Launchers Actuators and Scheme: – ECH, NBI, density, loop voltage? – Multipoint q-profile control – Share EC system with MHD control Equatorial EC Launcher NBI Current Profile Control Has Been Studied on Several Devices But Remains Highly Experimental 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 JET q-Profile Control D. Moreau, CEA q-profile regulated using LHCD, NBI, ICRH Safety factor 084-13/DAH/jy Start of Control End of Control

10. 10 Humphreys/55 th APS-DPP/October 2012 Divertor Ne gas puff 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 Divertor Control Experiments Have Been Performed But Research is Still Needed for ITER Solutions 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 084-13/DAH/jy

11. 11 Humphreys/55 th APS-DPP/October 2012 Divertor Ne gas puff 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 Divertor Control Experiments Have Been Performed But Research is Still Needed for ITER Solutions 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 DIII-D Divertor Detachment Control E. Kolemen, PPPL No Detachment Control (#153814) Detachment Control (#153815) Divertor Thomson measures detachment D 2 gas injection to regulate partial detachment state 084-13/DAH/jy

12. 12 Humphreys/55 th APS-DPP/October 2012 Actuators and Scheme: – Fueling species balance, transport control (RMP coils?) – Integrated regulation of kinetic operating point and burn state Fueling pellet launcher Burn Control Has Been Studied Minimally in Experiments and Requires Significant Research for ITER Solutions Status/Research Gaps: – Limited experiments – No ITER solution yet – Need model-based exception handling – Need integrated goals: scenario/kinetic and burn control RMP Coils 084-13/DAH/jy

13. 13 Humphreys/55 th APS-DPP/October 2012 Actuators and Scheme: – Fueling species balance, transport control (RMP coils?) – Integrated regulation of kinetic operating point and burn state Fueling pellet launcher Burn Control Has Been Studied Minimally in Experiments and Requires Significant Research for ITER Solutions Status/Research Gaps: – Limited experiments – No ITER solution yet – Need model-based exception handling – Need integrated goals: scenario/kinetic and burn control DIII-D Burn Control Experiment R. Hawryluk, PPPL nn n=3 RMP coil current (kA) P inj (MW) n=3 RMP coils used to modify transport β N controlled during NBI power surge (red) emulating burn excursion RMP Coils 084-13/DAH/jy

14. 14 Humphreys/55 th APS-DPP/October 2012 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. 15 Humphreys/55 th APS-DPP/October 2012 Tearing Mode Continuous Control in ITER Enables Multiple Catch and Subdue Events 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 DIII-D Catch and Subdue Simulated ITER 2/1 Catch and Subdue ρ EC ρ diag ρqρq P ECCD (MW) w ISLAND (cm) 084-13/DAH/jy

16. 16 Humphreys/55 th APS-DPP/October 2012 Continuous Tracking of Alignment Enables Rapid Suppression of Later Events and Low Average Power 084-13/DAH/jy 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

17. 17 Humphreys/55 th APS-DPP/October 2012 Degree of Novelty and Research Needed Varies Widely Among ITER Control Categories CategorySchemeActuatorsModelsAlgorithmsIntegration/E xceptions Axisymmetric Current profile Divertor Tearing Mode Burn 084-13/DAH/jy Mature, ITER-relevant Candidate ITER solutions Limited ITER-relevant experiments Limited ITER solutions Limited ITER-relevant experiments

18. 18 Humphreys/55 th APS-DPP/October 2012 Degree of Novelty and Research Needed Varies Widely Among ITER Control Categories CategorySchemeActuatorsModelsAlgorithmsIntegration/E xceptions Axisymmetric- Gaps - VS3 for Z - SC PF - Cu VS3 - Valid - Metrics - Robust - Model- based - Exception Handling - Disruptions Current profile- Multipoint - q profile? - EC, NBI - Ohmic ψ - Density? - Simple - Valid? - Metrics? - Static? - Adaptive - Actuator Sharing w/ MHD control Divertor- Impurity inj for radiation - Integrated core/div ctrl - Gas valves - Pellets - Simple & heuristic - Metrics? - Simple, not model- based or robust - Exception Handling - Actuator Sharing Tearing Mode- Sawtooth - Profile - Direct ctrl - ECH/ECCD - Profile ctrl - MRE - Metrics? - Profile params? - Model- based, but not robust - Exception Handling - Actuator Sharing Burn- Fueling ctrl - Transport ctrl? - Pellets - NTM ctrl? - RMP coil? - ??? 084-13/DAH/jy

19. 19 Humphreys/55 th APS-DPP/October 2012 Degree of Novelty and Research Needed Varies Widely Among ITER Control Categories CategorySchemeActuatorsModelsAlgorithmsIntegration/E xceptions Axisymmetric- Gaps - VS3 for Z - SC PF - Cu VS3 - Valid - Metrics - Robust - Model- based - Exception Handling - Disruptions Current profile- Multipoint - q profile? - EC, NBI - Ohmic ψ - Density? - Simple - Valid? - Metrics? - Static? - Adaptive - Actuator Sharing w/ MHD control Divertor- Impurity inj for radiation - Integrated core/div ctrl - Gas valves - Pellets - Simple & heuristic - Metrics? - Simple, not model- based or robust - Exception Handling - Actuator Sharing Tearing Mode- Sawtooth - Profile - Direct ctrl - ECH/ECCD - Profile ctrl - MRE - Metrics? - Profile params? - Model- based, but not robust - Exception Handling - Actuator Sharing Burn- Fueling ctrl - Transport ctrl? - Pellets - NTM ctrl? - RMP coil? - ??? 084-13/DAH/jy

20. 20 Humphreys/55 th APS-DPP/October 2012 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. 21 Humphreys/55 th APS-DPP/October 2012 084-13/DAH/jy Additional Slides

22. 22 Humphreys/55 th APS-DPP/October 2012 Catch and Subdue Events Must Be Rapid Enough and Infrequent Enough to Maintain Fusion Gain Q = P FUS /P EXT O. Sauter, PPCF 52 (2010) 025002 Reduced Q due to confinement loss from unstabilized saturated islands 3/2 2/1 Q~7 for 2/1 stabilized with 20 MW CW at HH=1.0 084-13/DAH/jy

23. 23 Humphreys/55 th APS-DPP/October 2012 Accomplishment of ITER Control Requires a Sophisticated Exception Handling System 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… Exception Handling Will Use a Finite State Machine Architecture Research is Required to Prevent Explosion in Complexity 084-13/DAH/jy

24. 24 Humphreys/55 th APS-DPP/October 2012 ITER Exception Handling System Requires a Powerful Forecasting Capability for Sufficient Look-Ahead 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 ITER PCS Forecasting System Functional Block 084-13/DAH/jy

25. 25 Humphreys/55 th APS-DPP/October 2012 ITER Control Will Depend Critically on Full Pulse Schedule Verification and Validation via Simulation 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 ITER Plasma Control System Simulation Platform Architecture Likely Similar to Structure of Pulse Verifier PCSSP ITER PCS Simulator ITER Plant Simulator PCS Development 084-13/DAH/jy

26. 26 Humphreys/55 th APS-DPP/October 2012 ITER Control will Depend Critically on Full Pulse Schedule Verification and Validation via Simulation 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 ITER Plasma Control System Simulation Platform Architecture Likely Similar to Structure of Pulse Verifier PCSSP ITER PCS ITER Plant Simulator Pulse Validation 084-13/DAH/jy