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

ties that take advantage of simple geometries to enable high-throughput, with well-diagnosed
material characterization. modeling efforts will span a range of complexities and assumptions,
from exploration of elementary processes such as sputtering due to single-ion impact, to coupled
codes modeling the full Psi environment. These include, for example, sheath formation, erosion
and material migration, and evolving surface morphology and concentrations of mixed materials.
strengthened effort in these theoretical simulations, validated properly by measurement from
test facilities, can significantly increase understanding and predictive capabilities of the Psi processes.
internal Components and Radiofrequency testing needs
Functional internal components (antennas, launchers, sensors, mirrors, control coils, etc.) must
meet the same criteria of other plasma facing components in terms of resistance to high heat (~1 -
20 mW/m 2 ) and neutron fluxes and acceptable levels of impurity production, while also maintaining
the capability to perform heating, diagnostic, or control functions. internal components can
also suffer damage if they lie in the path of particle fluxes produced in transient events; an important
example of such a scenario is the production of runaway electrons during a tokamak plasma
disruption. There are significant challenges in the areas of diagnostics, radiofrequency antennas
and launchers, and internal control coils.
burning plasma properties introduce new fundamental measurement limitations to some existing
measurement techniques, and present an environment that challenges a range of diagnostics.
maintenance of the optical quality of mirrors, polarizers, and windows located close to a burning
plasma environment represents a significant challenge. in particular, redeposition and erosion
combined with long plasma exposures are significant concerns.
Reliable performance of radiofrequency antennas and launchers is needed. many of the issues
concerning the interaction of the near field of the antenna and launcher with the scrape-off layer
plasma (sol) are not well understood. There is a need to predict, measure, adjust for, and modify
this edge environment since it is the region through which power is coupled. Radiofrequency
breakdown and arcing in the antenna structure are some of the main power limiting issues with
operating the antenna in the plasma environment, and are poorly understood. in addition, the
antenna structure and Faraday shield will likely be constructed from layered or coated materials
that require good conductivity and high heat resistance. The behavior of these structures in a nuclear
environment and the survivability in long-term operations are concerns.
Performance validation of ICs is required from both dedicated test stands and testing on toroidal facilities.
While many of the Psi processes can be addressed in a linear plasma device, the performance issues
for antennas and launchers can be addressed in a specialized radiofrequency test facility.
dedicated test facilities offer the advantages of providing a controlled and flexible environment
that is well-diagnosed and capable of long-pulse and cost-effective operations. toroidal devices
can be used for integrated effects, model verification, and demonstration of fully reliable ic components.
a dedicated high flux linear facility can be used to validate many ic design issues, including thermal
stresses at the joints subjected to high heat and neutron fluxes, cracking due to voids in braz-
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