Research Needs for Magnetic Fusion Energy Sciences - US Burning ...

ing and design include computational tools for producing control-level models and simulations,
ideally derived from more complex models, and control-level and intermediate-level simulations.
These will enable development and testing of control algorithms and verification of real-time implementations.
models required include all elements of a fusion plant system: relevant plasma responses,
actuator responses to commands, diagnostic signal mappings to relevant physics, etc.).
integrated, comprehensive plasma and plant simulations will also be needed, primarily for discovery
of emergent phenomena, unexpected interactions, commissioning, performance and reliability
quantification, and certification. Real-time predictive models will be needed for on-line
operating point identification, controller adjustment and re-design, stability boundary proximity
identification and so on. models and simulations must be validated against relevant experimental
data to confirm the required accuracy.
aLgORitHMS anD aPPROaCHES
The requirement of producing quantifiably high-performance operational solutions requires research
to produce novel control algorithms. This research includes mathematical solutions for
nominal high-performance control, as well as supervisory and off-normal response algorithms
with provable reliability. control schemes must be developed for all required regulated parameters
and stabilized modes, including multi-physics integrated schemes where appropriate. design
tools and solutions must be developed to produce the necessary real-time, model-based control
algorithms (mathematical control solutions) with associated gains, point designs, and provable
high confidence performance.
as a specific example of the control research needed, a reactor design that operates near stability
limits to achieve high performance will require active suppression of tearing modes. Present-day
research has demonstrated the need for complex nonlinear control algorithms to locate and align
current deposition regions with relevant magnetic islands, to synchronize modulated current
with the island phase, and to sustain the alignment and phase synchronization as plasma conditions
evolve. The corresponding algorithms used in a reactor must be much more robust than
present solutions, and must operate correctly and effectively upon first-time use. at the same
time, the relative leverage provided by heating and current drive systems in self-heated burning
plasmas will be much smaller. These requirements necessitate a robust design based on high accuracy
models: the task is beyond the capability of empirical tuning, and in any case little opportunity
will exist in the commissioning process to achieve such tuning. mathematical control design
methods can guarantee a specified level of reliability and robustness, based on the accuracy and
reliability of the models on which the design is based, and can squeeze maximum effectiveness
from limited actuators. in exactly the same way as envisioned for fusion reactors, model-based
design of complex multivariable control algorithms is what enables modern commercial aircraft
to fly well and safely in their first flight tests, and indeed in all of their commercial flight operations.
tRaNSiENt plaSMa EvENtS: additioNal RESEaRch REquiREMENtS
Overall goal: Understand the underlying physics and control of high-performance magnetically
confined plasmas sufficiently so that “off-normal” plasma operation, which could cause cat-
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