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

• investigate how demountable coils could improve maintenance issues for stellarators.
• determine whether conductor elements can be “printed” on structural elements for coil
formation.
thE SphERical toRuS
introduction
The spherical torus (st) is a low aspect ratio tokamak that offers advantageous physical properties
due to very strong magnetic curvature and compact geometry (Figure 3). This configuration
produces high plasma pressure relative to the external magnetic pressure and strongly affects
plasma stability and confinement. it offers the promise of simple magnet design, reduced size,
cost, and ease of maintainability. a description of the st can be found in the Report of the Fesac
toroidal alternates Panel (2008) (http://fusion.gat.com/tap/).
Figure 3. ST magnetic field geometry compared to conventional tokamak geometry.
research Goals
The ReneW st panel largely adheres to the iteR-era goal stated in the executive summary of the
taP Report and the topical areas of research, with some important clarifications of emphasis and
alterations. The iteR-era goal is stated as: “Establish the ST knowledge base to be ready to construct
a low aspect-ratio fusion component testing facility that provides high heat flux, neutron flux, and duty
factor needed to inform the design of a demonstration fusion power plant.” The ReneW st Panel clarifies
that properly informing the design of a demonstration fusion power plant requires that research
extend past the needs of an st fusion nuclear science component testing facility (st-ctF)
in the iteR-era. it is equally important that this research examine a high level of plasma control
flexibility and performance beyond baseline st-ctF design needs to minimize performance risk
for st-ctF. This is because an st-ctF will not be a research facility, but rather an application of st
research, with limited diagnostics and control variation capabilities to determine design optimizations.
other proposed st applications are the driver for a fusion-fission hybrid device, and an
st-based demonstration fusion power plant (demo). The majority of the st Panel further suggests
that research aggressively pursue improvements to the st concept that advance an st-based
demo, proposed by Us and international researchers. These clarifications, related to minimizing
the risk of attaining the iteR-era goal, were adopted when preparing the research needs for st research
described in this document. The original twelve critical research issues defined in the taP
report are retained, now expanding the “3-d fields” critical issue to more broadly include needed
research in “stability and steady-state control.”
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