Accelerator Magnet Technology Division

Measurement facility

Harmonic Bench model 692

The DANFYSIK multipole magnet measurement system, Model 692 (obtained on loan basis from ESRF, France) is developed for measurement of the strength and quality of multipole magnet fields, for magnetic centering, and for precise positioning of alignment targets on the magnets. The measurement system has been designed with the aim to perform precise, fast and reliable measurements of series of magnets. Care has been taken to ensure that the mechanical constructions have sufficient stability against or is insensitive to vibrations and thermal expansion. With computerized routines for prealignment, harmonic measurement and data analysis, magnetic centering and alignment, the need for operator intervention during the actual measurements and data evaluation is minimized.

The measurement system is based on the Phharmonic coil methodPh in which a mechanically stable cylinder holding the main measuring coil is rotated inside the bore of the magnet. The induced voltage across the coil terminals is sampled and integrated over equally spaced angular intervals. This measurement provides an accurate determination of the integrated field and the magnet center position. Table 1 gives the overall specifications of multipole magnet measurement system, model 692. Figure 1 shows the photo of harmonic bench during installation.

Table 1: Overall specifications of the bench

Relative accuracy of integrated main harmonic


Angular phase absolute accuracy

±0.2 mrad

Lateral positioning of magnetic center with respect to rotation axis

±0.03 mm

Positioning accuracy of alignment targets with respect to coil axis

±0.03 mm

Accuracy of ratio between integrated field of a multipole component and the main component at major coil radius


Figure 1: Photo of harmonic bench

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