Design of Comb Fabricated Halbach Undulators

Abstract

An approach to fabricating Halbach array undulators using “combs” machined from single magnets is introduced. This technique is especially relevant to the fabrication of short period micro-undulators with period lengths considerably less than the few-centimeter-scale typical of current undulators. Manual, magnet-by-magnet assembly of micro-undulators would require the manipulation and alignment of thousands of magnets smaller than a grain of rice: comb fabrication dramatically increases the size of the basic unit cell of assembly with no increase in undulator period by creating many periods from a single piece, in a single machining modality. Further, as these comb teeth are intrinsically indexed to each other, tolerances are dictated by a single manufacturing step rather than accumulating errors by assembling many tiny magnets relative to each other. Different Halbach geometries, including M ′ = 2 , M ′ = 4 , isosceles triangle, and hybrid, are examined both from a theoretical perspective and with 3D magnetostatic simulations.

Keywords

• undulators
• magnet design
• permanent magnets
• microfabrication
• nonconventional machining