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

proved physics understanding is required, including sufficiently detailed computational physics
models and control-level models. control models frequently require far less accuracy and/or
precision than the goals of detailed physics codes, although measurement accuracy and precision
requirements tend to be very high for real-time control. Improved mathematics and algorithmic
understanding is required in most cases for development of the required control schemes
and controller designs. The engagement and coordination of cross-disciplinary expertise, including
physics, control mathematics, and fusion system engineering, is essential to fill these research
gaps.
OPERating REgiME REguLatiOn
Regulation of fusion plant system operating regimes generally includes the equilibrium shape
and position state, bulk quantities (such as plasma current and beta), various profiles (including
current density, pressure, density, and rotation), and the divertor configuration. Particular solutions
needed for power plants include operating point regulation for noninductive, true steadystate,
self-heated, sustained duration operation, likely with high bootstrap current fraction. specific
research requirements identified for operating regime control include developing algorithms
and approaches for use of superconducting coils in reactor regimes and noninductive operation,
as well as general methods for integrated regulation of global parameters (e.g., plasma current,
stored energy, fusion power output). Plasma shape control schemes must be developed consistent
with limited availability of diagnostics and coils. experimental demonstrations of operating regime
control of self-heated plasmas must be performed in discharges with high (up to 90%) bootstrap
current fraction.
PLant StaRtuP anD SHutDOWn
control demands for plant startup and shutdown are expected to be challenging in demo, owing
to limitations in central solenoid size and available flux. For example, startup of several aRies
point designs with attractive cost of electricity will require several hours, relying on initiation
and burn-through using a small solenoid followed by pure noninductive rampup 2,3 . Research is required
to develop and experimentally demonstrate such a plasma current ramp-up to the steadystate
regime, followed by ramp-down using minimal inductive current drive.
KinEtiCS
outstanding solutions required for kinetic control (e.g., temperature and density profiles) in plant
operation include steady-state fueling solutions and divertor kinetic operation (including heat
flux, radiation state, impurity and pumping regulation, and control of advanced configurations
with high multipole moment magnetic topologies). Research requirements in this area include
development of methods for and demonstration of coupled performance in the core and divertor
(neutron rate/fusion power, h-mode confinement state, power flow through pedestal into sol).
divertor operation will require development of methods for regulation of the divertor magnetic
configuration consistent with a high nuclear fluence reactor environment, which may be particularly
challenging for high magnetic multipole configurations (e.g., “snowflake” or “super-X” divertors,
discussed in Theme 3) with stringent requirements on divertor coil proximity and diagnos-
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