Nonlinear Burn Control in Tokamaks using In-Vessel Coils
A. Pajares and E. Schuster
IEEE Multi-conference on Systems and Control
Buenos Aires, Argentina, September 19-22, 2016
Abstract
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The tokamak is a magnetic-confinement device where a plasma is confined
with the final purpose of generating power from fusion reactions.
Unfortunately, working points with favorable fusion conditions in tokamaks
are normally found in a region in which the plasma may be thermally unstable.
Therefore, regulation of the plasma temperature and density to produce a
certain amount of fusion power while avoiding thermal instabilities, known
as burn control, is one of the key issues that need to be solved for
the success of burning plasma tokamaks such as ITER. Most previous
controllers make use of approximate linearization techniques. In the
present work, a model-based control approach us- ing nonlinear
techniques is proposed. This nonlinear control approach avoids
approximate linearization of the model, is applicable to a greater
range of operating conditions, and is stable against a larger set of
perturbations. In addition to conventional actuation, like modulation
of the auxiliary power and modulation of the fueling rate, the in-vessel
coil system is considered as a new actuator. The in-vessel coils have
the capability to generate non-axisymmetric magnetic fields that modify
the plasma confinement, which influences the plasma energy dynamics.
A model is proposed to account for the influence that the in-vessel
coil actuation has on the plasma confinement. Finally, the effectiveness
of the controller is demonstrated via a simulation study for an ITER-like scenario.