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Halbach Arrays

Halbach Array Configurations

A Halbach array is a special magnet assembly with rotating magnetization pattern. It is designed to achieve higher magnetic flux required on one side while reduce the flux on the other side, and/or it can concentrate magnetic flux to achieve higher density than regular magnets.

This structural concept, one-sided flux as shown in figure 1, was first proposed by J. Mallinson [1] when he theoretically demonstrated the magnetic flux enhancement for tapes, disks and other planar magnetic structures in the 1970s.

one sided flux
Figure 1. One-sided flux. (Adapted from Ref. [1])

In the 1980s, Klaus Halbach [2] developed practical permanent magnet systems, now known as Halbach arrays, when he was designing high magnetic flux for accelerators and electron storage rings.

halbach cylinders, dipole, quadrupole
Figure 2. Halbach Array Rings: (a) Dipole and (b) quadrupole. (Adapted from Ref. [2])
linear halbach array, planar halbach array
Figure 3. Linear Undulator. (Adapted from Ref. [2])
linear halbach flux simulation, planar halbach field simulation
Figure 4. Planar Halbach magnetic flux distribution. (Adapted form Ref. [3])
circular halbach flux simulation, halbach dipole field
Figure 5. Circular Halbach magnetic flux distribution. (Adapted form Ref. [3])

Halbach Array Magnet Materials

Regular Halbach array industrial magnet materials: NdFeB magnet, samarium cobalt.

Halbach Array Applications

Linear Halbach arrays help confine magnetic field, the field is approaching twice as large on the side the flux confined. They are suitable for particle accelerators and synchrotron radiation applications.

Halbach cylinders with self shielding can help electric motors use lighter materials instead of back irons. The confined magnetic field also help yield high power density. They are applied in brushless DC motors, AC motors, magnetic couplings.

References

[1] J. Mallinson, “One-sided fluxes – A magnetic curiosity?”, IEEE Transactions on Magnetics 9, 678 (1973).

[2] Klaus Halbach, “Application of permanent magnets in accelerators and electron storage rings (invited)”, Journal of Applied Physics 57, 3605 (1985).

[3] Wikipedia, Halbach array, https://en.wikipedia.org/wiki/Halbach_array.