Measurements of inhomogeneities of magnetic fields in a model beam-analyzing magnet

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Abstract

A sectorial model beam analyzing magnet has been fabricated to obtain some precise information about the inhomogeneities of magnetic fields for an ordinary magnet. The magnet has field homogenizers, air gap spacers machined accurately, pole pieces separated from the yokes and a power supply with a current-stability better than 1 part in 104.

In the magnet constructed so as to suppress mechanical aberrations, the important sources producing the field inhomogeneities in an azimuthal direction are the saturation effect in the pole piece iron, the mechanical accuracy of the pole pieces, the setting procedure of the field, the type and iron material of the pole pieces, and so on. The field inhomogeneities in a radial direction arise mainly from the difference of the leakage factor in the pole piece sides at small and large radii, and the narrowness of the effective pole piece width. Field homogeneities are not improved by introducing the field homogenizers. The B-constant design of the pole pieces has excellent effects on the field homogeneity.

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