文档介绍：NUCLEAR INSTRUMENTS AND METHODS 169 (1980) 1-10~ © NORTH-HOLLAND PUBLISHING CO.
DESIGN OF PERMANENT MULTIPOLE S
WITH ORIENTED RARE EARTH COBALT MATERIAL*
K. HALBACH
University o/ Cal(/brnia, Lawrence Berkeley Laboratmy, Berkeley, CA 94720, .
Received 20 August 1979
By taking advantage of both the ic strength and the astounding simplicity of the ic properties of oriented rare
earth cobalt material, new designs have been developed for a number of devices. In this article on multipole s, special
emphasis is put on quadrupoles because of their frequent use and because the aperture fields achievable (- T) are rather
large. This paper also lays the foundation for future papers on : (a) linear arrays for use as "plasma buckets" or undulators for
the production of synchrotron radiation; (b) structures for the production of solenoidal fields; and (c) three-dimensional
structures such as helical undulators or multipoles.
1. Introduction infrequently that they cannot be expected to be at
For some applications, the most important of the the fingertips of most readers.
many advantages of permanent s is the fact
that they can be made very small without reduction 2. Basic formulae, notation
of ic field strength. In conventionally pow- For three dimensional (3D) calculations, we use
ered s, the current density in the coils is the standar