Stellarator optimization

In tokamaks, a significant part of the confining magnetic field is produces by the currents flowing in the plasma itself. In contrast, the confining magnetic field of stellarators may be dominated by externally imposed magnetic fields (depending on the configuration). Since the confinement properties of toroidally confined devices depend sensitively on the magnetic field, the question arises whether this external control may be used to improve confinement properties, and thus facilitate the development of an economically attractive stellarator reactor.

Several optimization strategies have been developed and/or are being studied. ^[1]

Optimization of Neoclassical transport. See omnigeneity and quasisymmetry.
Optimization of Anomalous transport^[2]
Combined numerical approaches^[3]

Optimized stellarators

W7-X - Neoclassical optimization; under construction
HSX - Quasihelical symmetry; operational
QPS - Quasipoloidal symmetry; under construction
NCSX - Quasi-axisymmetry; cancelled

References

[1] H.E. Mynick, Transport optimization in stellarators, Phys. Plasmas 13 (2006) 058102

[2] H.E. Mynick, N. Pomphrey, and P. Xanthopoulos, Optimizing Stellarators for Turbulent Transport, Phys. Rev. Lett. 105 (2010) 095004

[3] F. Castejón, A. Gómez-Iglesias, M.A. Vega-Rodríguez, J.A. Jiménez, J.L. Velasco and J.A. Romero, Stellarator optimization under several criteria using metaheuristics, Plasma Phys. Control. Fusion 55 (2013) 014003

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