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

• applying 3-d shaping to understand nonsymmetric quasi-single helicity (Qsh) equilibria
in reverse field pinches (RFPs).
suppression of type 1 edge localized modes (elms) in tokamaks (see Thrust 2) is required for
iteR. While not explicitly a type of 3-d shaping, the successful application of 3-d perturbation
fields to control elms makes use of analytic tools developed and used in stellarator research.
key research steps include:
• conceptual design and modeling of quasi-axisymmetric stellarators with variable levels of
3-d shaping to perform as stellarator-tokamak hybrids.
• test of variable 3-d shaping on stellarator-tokamak hybrids.
• application of 3-d analysis techniques to reverse field pinch plasmas.
• application of 3-d analysis and design approaches to elm suppression on existing
tokamaks and iteR.
Understanding the fundamental consequences of 3-d shaping could bring wide-ranging benefits
to the science of toroidal confinement.
Readiness
The Us has the leading theoretical and experimental program in quasi-symmetric stellarators,
and operates the only Qs stellarator (hsX, with Qh symmetry) in the world. a small stellaratortokamak
hybrid (cth) investigates the suppression of current-driven instabilities with 3-d shaping.
Us researchers also are leaders in the control of elms by application of 3-d fields. in concert
with a broad international program in stellarators, the Us research program is scientifically
and technically ready to proceed with diverted, hot-ion Qs experiments at the proof-of-principle
scale. The Thrust activities draw from:
• Positive results obtained on Qs confinement from ongoing hsX experiments.
• optimization procedures developed for the design of ncsX, a proof-of-principle scale
Qa experiment, providing a comprehensive suite of codes for the design of any new Qs
facility.
• The ncsX facility, which if completed would fulfill many of the scientific needs of the
intermediate-scale Qa facility described in this Thrust. construction of this facility
has been suspended, and serious consideration should be given to its completion and
operation, subject to appropriate review.
• knowledge of confinement scaling, stability, divertor performance, long-pulse
sustainment, and limiting behavior in stellarators, obtained primarily from lhd and
W7-as.
• existing and developing 3-d equilibrium and stability analysis tools.
• ongoing experimental work on stellarator-tokamak hybrids.
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