1 humphreys/55 th aps-dpp/october 2012 d.a. humphreys 1, g.l. jackson 1, r. hawryluk 2, e. kolemen...
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1Humphreys/55th APS-DPP/October 2012
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 the55th Annual APS MeetingDivision of Plasma Physics Denver, Colorado
November 11–15, 2013
Novel Aspects of ITER Plasma Control
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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
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Novel Elements in the ITER Plasma Control Development Process Include Model-Based Design and Shot Verification
Scenarios and Physics
Understanding
ControlSchemes
ActuatorEffects
Diagnostic
Responses
Models
AlgorithmsContinuo
us Control
Exception Handling
PCS Implementati
onVerification Simulations
Experiments/Validation
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The Plasma Control Development Process Includes Equal Measures of Physics Knowledge and Mathematics Solutions
Scenarios and Physics
Understanding
ControlSchemes
ActuatorEffects
Diagnostic
Responses
Models
AlgorithmsContinuo
us Control
Exception Handling
PCS Implementati
onVerification Simulations
Experiments/Validation
PhysiPhysicscs
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The Plasma Control Development Process Includes Equal Measures of Physics Knowledge and Mathematics Solutions
Scenarios and Physics
Understanding
ControlSchemes
ActuatorEffects
Diagnostic
Responses
Models
AlgorithmsContinuo
us Control
Exception Handling
PCS Implementati
onVerification Simulations
Experiments/Validation
PhysiPhysicscs
MathematiMathematicscs
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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
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• 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
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
CurrentA. Pironti, CREATE
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Upper EC
Launchers
• Actuators and Scheme: – ECH, NBI, density,
loop voltage? – Multipoint q-profile
control– Share EC system with
MHD controlEquatorial
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
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Upper EC
Launchers
• Actuators and Scheme: – ECH, NBI, density,
loop voltage? – Multipoint q-profile
control– Share EC system with
MHD controlEquatorial
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 ControlD. Moreau, CEA
• q-profile regulated using LHCD, NBI, ICRH
Safety factor
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Start of Control
End of Control
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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
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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
ControlE. Kolemen, PPPL
No Detachment Control (#153814)
Detachment Control (#153815)
• Divertor Thomson measures detachment
• D2 gas injection to regulate partial detachment state084-13/DAH/jy
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• 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
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• 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, PPPLn
n=3 RMP coil current (kA)
Pinj (MW)
• n=3 RMP coils used to modify transport
• βN controlled during NBI power surge (red) emulating burn excursion
RMP Coils
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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
EquatorialEC
LauncherNBI
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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
ρEC
ρdiagρq
PECCD (MW)
wISLAND (cm)
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Continuous Tracking of Alignment Enables Rapid Suppression of Later Events and Low Average Power
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• 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
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Degree of Novelty and Research Needed Varies Widely Among ITER Control Categories
Category Scheme Actuators Models Algorithms
Integration/Exceptions
Axisymmetric
Current profile
Divertor
Tearing Mode
Burn
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Mature, ITER-relevant
Candidate ITER solutionsLimited ITER-relevant
experiments
Limited ITER solutionsLimited ITER-relevant
experiments
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Degree of Novelty and Research Needed Varies Widely Among ITER Control Categories
Category Scheme Actuators Models Algorithms
Integration/Exceptions
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 orrobust
- 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?
- ??? - ??? - ???
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Degree of Novelty and Research Needed Varies Widely Among ITER Control Categories
Category Scheme Actuators Models Algorithms
Integration/Exceptions
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 orrobust
- 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?
- ??? - ??? - ???
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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
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Additional Slides
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Catch and Subdue Events Must Be Rapid Enough and Infrequent Enough to Maintain Fusion Gain
Q = PFUS/PEXT
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
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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
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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 Simulati
on
Realtime Stability/ Control
Boundaries
ITER PCS Forecasting System Functional Block
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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
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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
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