Field Quality From Tolerance Analyses In Eight-Piece Quadrupole Magnet

Abstract

Quadrupole magnets are used extensively in particle accelerators, synchrotrons, and storage rings all over the world. Excellent field quality is needed in these magnets, which requires machining the magnet parts to high precision. An eight-piece quadrupole design and assembly method is developed that produces the desired magnetic field quality by accurately positioning the pole tips. In this magnet design, all the parts need to be machined only within standard machining tolerances. This paper presents the magnetic and mechanical tolerance analyses of this quadrupole design. We performed mechanical tolerance stack-up analyses using the Teamcenter Variation Analysis software to evaluate the relationship of part-level machining tolerances to final magnet assembly errors. We then performed finite element analyses using OPERA to estimate the effect of assembly errors on magnetic field quality; and in turn to set the acceptable machining tolerances for parts to achieve the desired magnetic performance. We conclude from our tolerance analyses that a 0.025-mm symmetry in pole tip gaps and pole tip diagonal gaps can be achieved with 0.050-mm standard machining tolerances, resulting in improved field quality. The analysis results are compared to the magnetic measurements in an R&D eight-piece quadrupole magnet.