An Introduction to the Halbach Array
By Paul Fears | 07 September 2020
Halbach Arrays feature in many common-day devices such as brushless DC motors and even the Inductrack Maglev train. The Halbach Array is a specific arrangement of permanent magnets that cancels the magnetic field to nearly zero on one side, but significantly increases the strength of the magnetic field on the opposite side. This magnetic phenomenon is only achieved when there is a spatially rotating pattern of magnetisation. The rotating pattern repeats indefinitely without any alternation in the magnetic properties. The effect is comparable to placing a bank of horseshoe magnets next to each other, with the similar poles touching.
Halbach Array assemblies produce high-strength but controllable magnetic fields, which is hugely beneficial in many applications. They are commonly produced in either straight or circular arrangements to suit the application.
The Origin of the Halbach Array
British-American physicist, John C. Mallinson (1932-2015), first discovered the effect behind the Halbach array in 1973. Mallinson initially described the “one-sided flux” structures as a “curiosity”, before applying the magnetic phenomenon to improving magnetic tape technology.
Further advances occurred in the 1980s, when physicist Klaus Halbach (1925-2000), a physicist working in the Lawrence Berkeley National Laboratory with the Engineering Division, independently invented the Halbach array for use in lasers, traveling wave tubes, and particle accelerator beams. Halbach became an international expert in magnetic systems for particle accelerators.
Manufacturing Halbach Arrays
Bunting’s specialist magnet production team assembles Halbach Arrays at their Berkhamsted plant in the UK. This requires specialist skills due to the complexity and necessity for assembly to take place with the magnets in a magnetised state.
Halbach Arrays and Modern Technology
The Halbach Array is a fundamental design component used widely in modern technology. As Halbach cylinders, they produce an intense and contained magnetic field. Such magnetic cylinders feature in brushless DC motors, magnetic couplings, and high-field particle focusing cylinders.
Even simple refrigerator and noticeboard magnets use Halbach arrays – producing a strong attractive magnetic force on one side, but with hardly any attraction on the opposite side.
Other applications include:
- Particle accelerators, magnetic lenses, and free-electron lasers,
- Magnets used for fixing and holding;
- Medical applications;
- Power generating rotors;
- Magnetic levitation;
The Halbach Array is in action whenever there is a magnet with a magnetic field that increasing on one side and decreasing on the other side.
- Related technical article: Replicating True Radial Arc and Ring Magnets with Pseudo-Radial Arcs and Rings
Bunting design and manufacture a wide range of magnets and magnetic assemblies. Many are bespoke for specific applications. For further information on bespoke magnet assemblies and magnet designs, please contact us via:
Phone: +44 (0) 1442 875081
Email: sales.berkhamsted@buntingmagnetics.com
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