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

scale, adequately handle the broad range of relevant problems in the integrated modeling
area? if not, what alternate approaches can be applied?
• can the reliability of each component, as well as the framework connecting components,
be improved to the point where integrated models can be used to routinely plan and
analyze burning plasma experiments in iteR?
research requirements
Theory is needed to improve the fundamental techniques used in multi-scaled simulations. improved
reduced models using the parameterization approach are needed for plasma startup and
subsequent evolution of a burning plasma discharge toward the final burning plasma configuration,
including episodic mhd phenomena, plasma-wall interactions and turbulent transport over
a wide range of conditions. a reliable prediction of the conditions needed for the l-h transition
is critically needed, particularly under conditions with a saturated reactor-relevant wall, along
with a model for the subsequent development of the density, temperature, and velocity pedestals.
models are needed to predict the onset of elm activity as well as the plasma evolution through
complete elm cycles. it is also important to predict the performance of elm control techniques,
now poorly understood. a neoclassical tearing mode model is needed that includes the effects of
mode coupling and rotation. an improved model of the core “sawtooth” crash is needed, which
must include the effects of fast ions and predict the fraction of magnetic reconnection. transport
models must be improved to predict transport near magnetic axis and in the high confinement
mode (h-mode) pedestal and sol region, rather than relying upon experimentally determined
values at an arbitrary outer boundary. it is likely that 3-d transport models must be developed
for regions near helical magnetic islands, and a dynamic model is needed for neutrals recycled
from plasma facing components into the sol and pedestal region. advances in radiofrequency
antenna-edge plasma coupling, wave propagation and absorption, and fast particle effects are
also needed. improved communications between first-principles physics simulations and reduced
models are needed to test and modify reduced models as needed during the evolution of a simulated
discharge.
coNtRol: additioNal RESEaRch REquiREMENtS
Overall goal: Investigate and establish schemes for maintaining high-performance burning plasmas
at a desired, multivariate operating point with a specified accuracy for long periods, without disruption
or other major excursions.
intRODuCtiOn
The control research needs of iteR are discussed in Theme 1. control research under Theme 2 focuses
on the needs of demo and an eventual power reactor. Fusion power plants are expected to
be among the most complex systems ever to operate for periods of many months without shutdown.
many of the operational control issues are similar to those encountered in present-day fusion
experiments and process-controlled plants. The number of regulated subsystems, the range
of time scales, the complexity of the highly coupled nonlinear multivariable control problems, the
complexity of the technologies, and the nuclear safety issues involved make it unlike any other
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