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

fectiveness, dynamic performance, and accuracy. Experimental demonstrations of control schemes
and specific control algorithms are essential to fully confirm the solution before application to
iteR. Improved physics understanding may still be required, including sufficiently detailed computational
physics models and control-level models. control models frequently require far less accuracy
and/or precision than that for detailed physics codes (although measurement accuracy and
precision requirements tend to be very high for real-time control). Improved mathematics and algorithmic
understanding are required in many cases to develop the required control schemes and controller
designs. The engagement of cross-disciplinary expertise, including physics, control mathematics,
and fusion system engineering, will be essential in filling these research gaps.
Providing robust, reliable control of plasma
Plasma Startup and Shutdown: achievement of robust, non-disruptive startup and shutdown
scenarios for iteR represents a challenging operational control problem owing to the tight constraints
on the available transformer action (i.e., volt-seconds), superconducting coil voltages and
currents, plasma shape, and allowable disruptivity. development and experimental demonstration
of startup and normal shutdown solutions will be required for each iteR operating scenario.
Rapid shutdown solutions must also be developed for an unscheduled demand shutdown or to
preempt an impending off-normal event.
Operating Regime Regulation: Regulation of the iteR operating regime includes the equilibrium
shape and position state, bulk quantities (such as plasma current and stored energy), various
profiles (including current density, pressure, density, and rotation), and the divertor configuration.
because iteR scientists recognize the importance of using robust model-based multivariable
control solutions for shape and stability control, this approach must be demonstrated and
qualified in operating devices prior to iteR operation, along with the pulse verification simulations
envisioned to precede each iteR discharge. solutions for equilibrium control consistent
with the iteR operating environment must also be developed and demonstrated.
Kinetic Control: achieving self-consistent solutions that combine adequate d-t fusion power
generation in the core and sufficient heat dispersal for protection of the plasma facing materials
requires methods for controlling the kinetic state of the plasma, including fueling and divertor
regulation. Fueling solutions consistent with iteR requirements (e.g., high-field-side deeply
injected pellets, ~1.0 cm 3 solid d-t) must be developed, although full demonstration will likely
await the iteR burning plasma. methods for active control of divertor-target heat flux, radiation
state, and degree of detachment all must be developed and demonstrated. although iteR will
probably operate in the thermally stable regime, methods for demonstrating burn regulation (e.g.,
fueling regulation coupled with saturated mhd amplitude regulation to modify transport) will be
required to ensure minimal excursions arising from operating point fluctuations.
Stability Control: iteR operation in high-performance regimes requires active and reliable
stabilization of a number of instabilities, including the resistive wall mode, neoclassical tearing
modes, axisymmetric instabilities, elms, and possibly also sawteeth and energetic particle-driven
modes. development of active stabilization solutions for these and other instabilities will require
greatly increased understanding of all relevant modes and their stabilization mechanisms,
along with experimental demonstrations in multivariable, highly coupled, integrated forms prior
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