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

• availability of high-power radiofrequency (electron cyclotron heating) and neutral beam
heating systems with proven application to stellarators
Scale and integration of Efforts
The Us stellarator program is prepared to make significant advances in the area of sustained disruption-free
confinement. however, its experimental facilities are inadequate for testing the innovative
ideas in Qs confinement at high plasma pressure and temperature simultaneously. While
the large international experiments can provide important information in this regard, they are
not quasi-symmetric.
two Qs experiments with sufficient heating power to test ion confinement, plasma stability, limiting
mechanisms, divertor performance, and integration of good confinement with high b would
span the necessary range of operating space in quasi-symmetry and plasma current to extrapolate
with confidence to an optimal Pe-scale stellarator, and ultimately a reactor. They would be designed,
built, and operated as a unified effort. This would ensure that the necessary scientific comparisons
can be made, and that an appropriate range of coil design and divertor options, as well
as heating systems, will be considered. The elements of this Thrust are clearly integrated toward
this goal. in addition to construction costs, the effort will require manpower to be allocated to:
• Physics modeling and magnet coil optimization.
• Three-dimensional divertor design.
• machine design and engineering.
• Physics planning.
• diagnostics development and 3-d equilibrium reconstruction techniques.
• integrated predictive theory.
Other Scientific benefits
now that 3-d effects are known to affect many toroidal confinement schemes, improved understanding
of 3-d shaping is a broad scientific benefit to magnetic confinement. The Thrust to improve
the integrated performance of a system that operates steady state without disruption addresses
the clear need of fusion-scale devices to avoid severe off-normal events, as called for in
the Greenwald Panel report. techniques and analysis of nonsymmetric trim magnet coils are applicable
to resonant magnetic perturbation coils for tokamaks in which urgent efforts are underway
to understand and develop effective elm-suppression approaches for Jet and iteR. lastly,
the obvious application of high-temperature superconductors to steady-state stellarators could
motivate more rapid development of that technology for all fusion systems requiring continuous
high fields.
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