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

Proposed actions:
Short-term: begin development of nuclear-robust control-specific diagnostics, high-performance
actuators, reduced models, and robust control algorithms with appropriate enhancement and exploitation
of presently operating devices. increase integration of relevant areas of expertise in diagnostics
and actuators for control requirements, control model development, control algorithm
mathematics, computational simulations, and physics understanding.
Medium-term: Use new experiments to demonstrate solutions with extended pulse duration in
deuterium (d-d) plasmas, through international collaboration where possible.
Long-term: Use iteR and new deuterium-tritium (d-t) devices being proposed to develop and
demonstrate the integrated control solutions required for demo.
The key element that distinguishes the advanced tokamak (at) and related scenarios from more
conventional limited-pulse tokamak operation is the unprecedented level of active control required
for robust high-performance operation. The ultimate goal of a control system is to control
the power flow in a reactor safely and efficiently, by controlling the plasma. The central aim of the
Thrust then is to enhance, develop, and demonstrate the enabling science and technology for controlling
and sustaining fusion plasmas in steady state and in close proximity to or beyond passive
stability limits. This will require progressive development and integration of control solutions,
diagnostics, and control actuators for a set of plasma parameters that are strongly interrelated:
global parameters; plasma shape; current density profile; density and temperature profiles, rotation
profile; d-t ratios; and impurity fractions. control of each element requires technologies for:
(i) diagnosis of the current state. Generally the diagnostic involves a set of measurements
from which the parameters of interest can be derived.
(ii) an actuator to modify the state. typically this involves controlling several kinds of
input to the plasma that can be related to the parameter needing to be controlled.
(iii) an algorithm to translate the required change in the state to the actuators controlling
the input to the plasma.
The necessary control will require a unified and comprehensive system in which the required sensors,
algorithms, and actuators are fully coordinated to diagnose and modify the parameters, profiles,
and their nonlinear interactions in a largely self-heated and self-driven tokamak plasma.
The facility for robust detection, avoidance, and response to significant transients and off-normal
events must be an integral component of the overall goal of maintaining steady state. This Thrust
will combine expertise from different communities to produce the integrated control-specific engineering,
physics, computational methods, simulations and mathematical solutions essential to
the success of a robust and reliable control system. The vision would be akin to that of modern
high-performance aerospace engineering systems that also operate beyond passive stability limits.
The challenges in a fusion reactor are that the fusion environment is much more hostile to
sensors and actuators, and the system is more fully self-driven.
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