Speaker
Description
In undulator development, strong attractive force acting between the top and bottom magnetic arrays is one of the important factors for determining the required specification of an undulator flame. An attractive force cancellation scheme using monolithic multipole magnets is implemented in In-Vacuum Undulator for SPring8-II(IVU-II) to relax the required specification. In theory, the scheme could compensate the attractive force completely, however, remaining force due to the error of magnetization of magnet pieces and misalignment of magnets is unavoidable in assembling the undulator magnet array. In order to evaluate the effectiveness of this scheme, we developed an attractive force measurement system, where one of the magnetic arrays was moved using a pair of lack and pinions located at Bessel points of the top magnetic array, while the bottom side was fixed. The distance of two magnetic arrays, namely the undulator gap, was monitored using a laser displacement sensor. The magnetic force acting on the magnetic arrays was measured using two load cells as a function of the undulator gap. In this presentation, we will give the detail of the system and some of the measurement result.
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