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This study presents a new stellarator magnetic configuration that achieves "piecewise omnigenity," a modified version of the omnigenity principle used in fusion reactor designs like tokamaks. Unlike traditional omnigenous fields that require continuous magnetic field strength, this approach allows for discontinuities while still maintaining perfect confinement of charged particles in the absence of collisions and turbulence. The configuration demonstrates improved transport properties, reduced particle losses, favorable stability characteristics, and compatibility with island divertor systems, meeting the standard physics requirements for a viable fusion reactor.
Why it matters
This work expands the design space for fusion reactor candidates beyond conventional omnigenous stellarators, potentially enabling new pathways to commercially viable fusion energy. By demonstrating that discontinuous magnetic field configurations can still meet reactor physics criteria, it could accelerate the development of more practical and efficient fusion power plant designs.
Understand the Science
arXiv:2601.14886v2 Announce Type: replace
Abstract: In piecewise omnigenous magnetic fields, charged particles remain perfectly confined in the abscence of collisions and turbulence. This concept extends the traditional notion of omnigenity, the theoretical principle upon which most of existing magnetic fusion reactor designs, including tokamaks, are based. While piecewise omnigenity broadens the range of potentially viable stellarator reactor candidates, it is achieved by relaxing the requirement of continuity in the magnetic field strength, which could appear to pose significant challenges for the design of magnetohydrodynamic equilibria. In this work, a stellarator magnetic configuration is presented that satisfies the ideal magnetohydrodynamic equilibrium equation and that achieves unprecedented levels of piecewise omnigenity. As a result, it exhibits favorable transport characteristics, including reduced bulk radial (neoclassical and turbulent transport), bootstrap current and fast ion losses. In addition, the configuration displays robust MHD stability across a range of b{eta} values and possesses a rotational transform profile compatible with an island divertor. Collectively, these features satisfy the standard set of physics criteria required for a viable reactor candidate which, until now, were believed to be attainable only by certain types of omnigenous stellarators.
Source: Piecewise omnigenous magnetohydrodynamic equilibria as fusion reactor candidates