Design and Performance of a New Magnetized Magnet Block on EPU Structure

Abstract

A prototype of an Apple-II elliptically polarized undulator (EPU4.6), of length 0.46 m, has been constructed to test the performance of the newly designed magnet block, which was magnetized at a tilt angle 10 . The magnet design and various mechanism analysis are performed to clarify the error source of multipole field components. Good end pole design in the EPU4.6 revealed the variation of the first integral field strength as function of gap and phase is minimized. Shimming algorithm had been used to improve the field quality and phase error. We report here the scheme of the magnetized block arrangement, an analysis of the design mechanism, the end pole design, field shimming and the final test performance using the Hall-probe mapping system.Index Terms-APPLE-II, elliptically polarized undulator, end pole design, magnetic field measurement.

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“…Although the Apple-II EPU has the greatest rates of polarization and the maximum magnetic-flux density in the horizontal field, the field roll-off of the two transverse field components declines rapidly, adversely affecting the top-up injection and dynamic aperture. For this reason the vertical field (B y ) rolloff was improved with either a thin shim at the edge of the magnet block [56] or an optimal angle of magnetization with respect to the vertical axis [57] of the magnet block. Figure 4 displays the mechanisms by which those two solutions decelerate the rapid decline of field roll-off; Fig.…”