Performance verification of a precise vibrating-wire magnet alignment technique for next-generation light sources.

K Fukami,S Takano,S Matsui,T Watanabe,J Kiuchi,C Zhang,N Azumi,S Inoue,T Kai,H Kimura

doi:10.1063/1.5086505

K Fukami, S Takano + Show 8 more

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https://doi.org/10.1063/1.5086505

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Abstract

The high-accuracy alignment of magnets is a key issue in the development of next-generation light-source rings. To obtain adequate dynamic apertures, the magnets must be aligned to an accuracy of 10 µm or better. Recently, a new technique that utilizes a vibrating wire has attracted attention for this purpose as it can directly determine with high resolution the magnetic centers in a series of multipole magnets on a straight section between bending magnets. In conventional vibrating-wire alignment techniques, wire sag, which causes alignment errors, is determined from the theoretical catenary curve. By contrast, in the present study, we have measured the sag profiles of various wires in the longitudinal direction to micrometer-order accuracy. We concluded that we can reduce deviations of the actual wire sag from the theoretical curve by choosing a suitable wire. By setting up a test bench of a vibrating-wire alignment system for a series of multipole magnet on a straight section, we have achieved the total error of the magnetic-center measurements of micrometer-order in the standard deviation. Moreover, two systematic error factors, the drift of the magnetic centers due to thermal deformations of the magnets after they are excited and the change in the magnetic centers due to reassembly of the magnets after installing the vacuum chamber, are included in practical magnet alignments. We have experimentally investigated these error factors using the test bench.

Highlights

Next-generation light sources are being designed or are under construction at synchrotron radiation facilities around the world with the aim of reducing the electron emittance by orders of magnitude compared with existing light sources.1–3 As such low-emittance rings naturally require high-gradient multipole magnets, the alignment tolerances of the magnets for obtaining adequate dynamic apertures tend to be smaller than for the previous high-emittance rings
By setting up a test bench of a vibrating-wire alignment system for a series of multipole magnet on a straight section, we have achieved the total error of the magnetic-center measurements of micrometer-order in the standard deviation
We report the measured deviations of the sag of an actual wire from the ideal catenary curve as well as the effects of local kinks in the wires, and we discuss a method of properly correcting the magnetic-center measurements for the wire sag profile

Summary

Introduction

Next-generation light sources are being designed or are under construction at synchrotron radiation facilities around the world with the aim of reducing the electron emittance by orders of magnitude compared with existing light sources. As such low-emittance rings naturally require high-gradient multipole magnets, the alignment tolerances of the magnets for obtaining adequate dynamic apertures tend to be smaller than for the previous high-emittance rings. Next-generation light sources are being designed or are under construction at synchrotron radiation facilities around the world with the aim of reducing the electron emittance by orders of magnitude compared with existing light sources.1–3 As such low-emittance rings naturally require high-gradient multipole magnets, the alignment tolerances of the magnets for obtaining adequate dynamic apertures tend to be smaller than for the previous high-emittance rings. The field profile of a multipole magnet near its magnetic center can be measured by detecting the vibration of the wire at its resonance frequency We have adopted this method to align a series of multipole magnets in a straight section, taking advantage of the feature that one can align the magnets while directly observing the magnetic center of each magnet without fiducialization

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