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

Figure 1. Configuration space for toroidal magnetic confinement.
of plasma conditions, and thereby enhancing the opportunity for scientific discovery and innovation
in toroidal confinement. it is possible that the optimum magnetic configuration will have
features and qualities that are significantly different from any of those studied in present-day devices,
including the tokamak.
For each of the four alternates, the taP identified a research goal for the iteR era, roughly the
next 20 years. The taP also identified the critical research issues and gaps in knowledge for each
of the magnetic configurations. The organization of the optimizing the magnetic configuration
Theme inherited the structure of the taP process by creating a panel for each of the alternate configurations.
The issues and gaps identified by the panel formed the basis for elaborating the research
needs that appear later in this chapter.
highlightS oF accoMpliShMENtS iN toRoidal altERNatE coNFiNE-
MENt RESEaRch
significant progress has been made in toroidal alternate research in recent years. each configuration
is described briefly, and highlights of research accomplishments noted.
Stellarator
The stellarator uses nonplanar magnets to produce nearly all of the helical magnetic field required
for toroidal confinement, thus reducing or eliminating the need for a plasma current. stellarators
are intrinsically steady state, and they do not exhibit current-driven instabilities that lead to fast
disruptive termination. The magnetic field has a visibly large degree of 3-d shaping, but the field
can be designed with “quasi” symmetry to attain similar confinement properties of axisymmetric
plasmas. highlights of stellarator research include:
• many stellarator devices have been successfully built and operated. Fusion plasma
parameters achieved are second only to tokamaks. ion temperatures of 7 kev have been
attained, and energy confinement is similar to tokamak scaling. advanced quiescent
confinement modes have been obtained without impurity ion accumulation.
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