Piecewise omnigenous stellarators with zero bootstrap current

Authors:
  • ICIvan Calvo
    Ivan Calvo
  • JVJose Luis Velasco
    Jose Luis Velasco
  • PHPer Helander
    Per Helander
  • FPFelix I. Parra
    Felix I. Parra
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Abstract
Until now, quasi-isodynamic magnetic fields have been the only known stellarator configurations that, at low collisionality, give small radial neoclassical transport and zero bootstrap current for arbitrary plasma profiles, the latter facilitating control of the magnetic configuration. The recently introduced notion of piecewise omnigenous fields has enormously broadened the space of stellarator configurations with small radial neoclassical transport. In this Letter, the existence of piecewise omnigenous fields that give zero bootstrap current is proven analytically and confirmed numerically. These results establish piecewise omnigenity as an alternative approach to stellarator reactor design.