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

The modeling of near-surface plasmas for liquid surfaces uses similar tools and has similar issues
to the modeling of solids, but here the evaporative fluxes into the plasma volume can be important.
Furthermore, the motion of the liquid is an issue that has received some attention, but needs
more work for flowing-liquid systems (also see Thrust 11). Given the encouraging results on existing
devices, the edge modeling capability that includes liquids, while available in some codes,
should be expanded.
dust formation and transport are a major concern in future large devices because of their potential
mobilization during an accident and possible core impurity contamination. models of dust
transport exist and can be utilized. needed are better understanding and models of dust formation,
either in Thrust 10 or Thrust 14.
c. Integrated models and synergies: The couplings between the dynamic wall and the sol, between the
sol, pedestal and core, and between local turbulence and long-time transport are not well modeled.
This is a key area for continued development, with initial scientific discovery through advanced computing
(scidac) projects now underway with Facets for the core/pedestal-sol/wall and the center
for Plasma edge simulation (cPes) for the pedestal/sol (see also Thrusts 4, 6). The development of
models associated with the boundary region should be designed in standard manner to fit into integration
efforts. important questions that can be answered by such coupling include the following:
• how does a dynamic wall/sol/pedestal system respond during time-dependent “blob” or
elm transport, i.e., how is it different from time-averaged models?
• how do sol/pedestal turbulent transport, neoclassical transport, and particle sources
combine to determine the pedestal plasma and divertor heat-flux profiles widths?
• how do impurities transport into the core through a turbulent sol/pedestal?
• how is the core density limit related to pedestal/sol behavior?
• how do sol flows influence core rotation?
3. Diagnostic and model development for radiofrequency antenna and launcher interactions
as noted, a substantial number of boundary plasma simulation codes and radiofrequency codes
exist, but these two communities have not collaborated strongly. Thus, there should be a concerted
effort to integrate radiofrequency effects into boundary codes and vice versa. There is also only
sparse data on radiofrequency sheath interactions leading to sputtering, and this should be enhanced.
to complement the outline of the types of boundary tools available above, the radiofrequency scidac
project, including collaborators in europe, is developing a set of radiofrequency codes to describe
the antenna coupling (toPica) and wave propagation (aoRsa, toRic). some preliminary
work has been done on the use of a sheath boundary condition in these codes and a newly developed
code to describe radiofrequency sheaths in the sol plasma. This work is guided by a number
of models to describe radiofrequency sheath formation under various assumptions. some studies
of radiofrequency-induced sputtering and self-sputtering have also been carried out and compared
with Jet and tFtR data. very modest work on physics integration has been carried out. in-
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