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

field and temperature fluctuations and profile. Pedestal gradients may invalidate the ordering assumptions
of gyrokinetic simulations, and may therefore force consideration of full kinetic simulations,
at least under limited conditions, to test if and when the gyrokinetic models break down.
comparison of experiment and simulation will likely require development of new synthetic diagnostics
(e.g., bes, probes, hibP, and/or GPi) and integration of these tools with edge gyrokinetic
simulations for direct experiment-model validation tests. new measurements of magnetic fluctuations
and edge current on existing tokamaks would help shed light on the physics of elms and
elm mitigation techniques. many of these studies can be done in existing tokamaks and laboratory
experiments. however, it must be recognized that experiments in iteR are required to simultaneously
access the collisionality, normalized gyroradius, and neutral fueling depth conditions
expected in demo.
Radiofrequency Modeling for Heating and Current Drive
Science Opportunities:
• how do alpha particles affect radiofrequency wave propagation and absorption?
• What possible transport effects from radiofrequency waves on alphas may be expected?
• What degree of plasma flow will be generated by radiofrequency waves in iteR and
demo?
• What are the current drive and heating power requirements and degree of location control
in iteR and demo?
research requirements
The validity of the geometrical optics wave propagation approach in h-mode with high pedestal
densities and steep gradients must be examined and perhaps replaced with full wave approaches.
improvements in wave particle interaction modeling, particularly for electron cyclotron wave
based approaches, are needed. accurate modeling of the edge geometry, including the PFc-RF
sheath interaction and edge gradients that are on the scale of the radiofrequency wavelength, is
needed. These tools must succeed in predicting radiofrequency coupling and loading of an antenna
to the edge plasma in the reactor environment, where antenna-plasma separation will be larger
than in present-day experiments. integrated modeling needs include development of RF-mhd
and RF-turbulence interactions. diagnostics for launched wave and mode converted wave detection,
as well as fast particle detection, should be deployed and compared with synthetic diagnostics
implemented in radiofrequency codes. Radiofrequency probe arrays in the sol would allow
improved radio frequency sheath physics and wave coupling understanding.
integrated Modeling
Science Opportunities:
• how can modeling bridge the disparate spatiotemporal scales that link different aspects
of high-performance steady-state burning plasma physics?
• can the current approach, invoking scale-separation arguments to decompose the
problem into a slowly evolving background coupled to a rapidly evolving spatiotemporal
92