Stellarators with Permanent Magnets.

  title={Stellarators with Permanent Magnets.},
  author={Per Helander and Michael Drevlak and M. Zarnstorff and S C Cowley},
  journal={Physical review letters},
  volume={124 9},
It is shown that the magnetic-field coils of a stellarator can, at least in principle, be substantially simplified by the use of permanent magnets. Such magnets cannot create toroidal magnetic flux, but they can be used to shape the plasma and thus to create poloidal flux and rotational transform, thereby easing the requirements on the magnetic-field coils. As an example, a quasiaxisymmetric stellarator configuration is constructed with only 8 circular coils (all identical) and permanent… 

Figures from this paper

Designing stellarators using perpendicular permanent magnets
We have developed a fast method to design perpendicular permanent magnets for simplifying stellarator coils based on existing codes. Coil complexity is one of the main challenges for stellarators. To
Geometric concepts for stellarator permanent magnet arrays
The development of stellarators that use permanent magnet arrays to shape their confining magnetic fields has been a topic of recent interest, but the requirements for how such magnets must be
Design of an arrangement of cubic magnets for a quasi-axisymmetric stellarator experiment
The usage of permanent magnets to shape the confining magnetic field of a stellarator has the potential to reduce or eliminate the need for non-planar coils. As a proof-of-concept for this idea, we
Calculation of permanent magnet arrangements for stellarators: a linear least-squares method
A problem arising in several engineering areas is to design magnets outside a volume that produce a desired magnetic field inside it. One instance of this problem is stellarator design, where it has
Design of quasi-axisymmetric stellarators with varying-thickness permanent magnets based on Fourier and surface magnetic charges method
To obtain engineering-feasible designs of stellarators with permanent magnets and simplified coils, a new algorithm has been developed based on Fourier decomposition and surface magnetic charges
Existence of an optimized stellarator with simple coils
An optimized compact stellarator with four simple coils is obtained from direct optimization via a coil shape. The new stellarator consists of two interlocking coils and two vertical field coils
Magnetic Fields with Precise Quasisymmetry for Plasma Confinement.
Quasisymmetry is an unusual symmetry that can be present in toroidal magnetic fields, enabling the confinement of charged particles and plasma. Here it is shown that both quasiaxisymmetry and
Topology optimization of permanent magnets for stellarators
We introduce a topology optimization method to design permanent magnets for advanced stellarators. Recent researches show that permanent magnets have great potentials to simplify stellarator coils.
Design of quasi-axisymmetric stellarators with variable-thickness perpendicular permanent magnets based on a two-step magnet design strategy
A new method for designing stellarators with variable-thickness perpendicular permanent magnets has been developed, based on a two-step magnet design strategy that we previously proposed for
Magnetic fields with precise quasisymmetry
Quasisymmetry is an unusual symmetry that can be present in toroidal magnetic fields, enabling confinement of charged particles and plasma. Here it is shown that both quasi-axisymmetry and


ESTELL: A Quasi‐Toroidally Symmetric Stellarator
This work presents the physics design for a simple quasi‐axially symmetric stellarator. A plasma configuration described by a modest number of Fourier coefficients was found to establish this
Quasi-helical symmetry in stellarators
The quasi-helical stellarator, which was invented by Nuhrenberg and Zille in 1988, is a toroidal fusion concept that has the excellent alpha confinement of the axisymmetric tokamak without the
Theory of plasma confinement in non-axisymmetric magnetic fields.
  • P. Helander
  • Physics
    Reports on progress in physics. Physical Society
  • 2014
The mathematical apparatus to describe stellarator plasmas is developed from first principles and basic elements underlying confinement optimization are introduced.
Equilibrium of a Magnetically Confined Plasma in a Toroid
A variety of properties are derived satisfied by any static equilibrium of a plasma governed by the well‐known magnetostatic equations. Some of these are local and quite trivial. Others involve
General Analytical Method for Magnetic Field Analysis of Halbach Magnet Arrays Based on Magnetic Scalar Potential
This paper presents a general analytical method for predicting the magnetic fields of different Halbach magnet arrays with or without back iron mounted on slotless permanent magnet (PM) linear
Solution of stellarator boundary value problems with external currents
Neumann boundary value problems are solved for stellarator fields generated by external currents. The method can be applied to the construction of external coil configurations of stellarators and to
Design of a Halbach Magnet Array Based on Optimization Techniques
We have designed a Halbach magnet array by using a numerical optimization method based on finite-element analysis. The magnetization direction of each element is defined as the design variable. The
One-sided fluxes -- A magnetic curiosity?
It is shown that a previously unknown class of magnetization patterns exists in planar structures which have the unique property that all the flux escapes from one surface with none leaving the other
Results from the International Collaboration on Neoclassical Transport in Stellarators (ICNTS)
Numerical results for the three mono-energetic transport coefficients required for a complete neoclassical description of stellarator plasmas have been benchmarked within an international
An improved current potential method for fast computation of stellarator coil shapes
Several fast methods for computing stellarator coil shapes are compared, including the classical NESCOIL procedure [Merkel, Nucl. Fusion 27, 867 (1987)], its generalization using truncated singular