Activities per year
Abstract
The problem of finding an optimal curve for the target magnetic axis of a stellarator is addressed. EulerLagrange equations are derived for finite length threedimensional curves that extremise their bending energy while yielding fixed integrated torsion. The obvious translational and rotational symmetries are exploited to express solutions in a preferred cylindrical coordinate system in terms of elliptic Jacobi functions. These solution curves, which, up to similarity transformations, depend on three dimensionless parameters, do not necessarily close. Two closure conditions are obtained for the vertical and toroidal displacement (the radial coordinate being trivially periodic) to yield a countably infinite set of oneparameter families of closed nonplanar curves. The behaviour of the integrated torsion (Twist of the Frenet frame), the Linking of the Frenet frame, and the Writhe of the solution curves are studied in light of the Calugareanu theorem. A refreshed interpretation of Mercier's formula for the onaxis rotational transform of stellarator magnetic fieldlines is proposed.
Original language  English 

Article number  092508 
Journal  Physics of Plasmas 
Volume  25 
Issue number  9 
DOIs  
Publication status  Published  1 Sep 2018 
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Activities

Simons Collaboration on Hidden Symmetries and Fusion Energy
David Pfefferle (Participant)
28 Mar 2019 → 30 Mar 2019Activity: Conferences and workshops › Contribution or participation in a conference

60th Annual Meeting of the APS Division of Plasma Physics CoLocated with the 71st Annual Gaseous Electronics Conference
David Pfefferle (Participant)
5 Nov 2018 → 9 Nov 2018Activity: Conferences and workshops › Participation in workshop, seminar or course