Open loop compensation for the eddy current effect in the APS storage ring vacuum chamber

Results of the effort to counter the effect due to the finite inductance of the magnet and the eddy current in the 1/2-in-thick aluminum storage ring vacuum chamber are presented. The amplitude attenuation and the phase shift of the correction magnet field inside the APS storage ring vacuum chamber were measured. A circuit to compensate for this effect was then inserted between the signal source and the magnet power supply. The amplitude was restored with an error of less than 20% of the source signal amplitude and the phase shift was reduced from 80 degrees to 12 degrees at 10 Hz. Incorporation of this circuit in the closed-loop feedback scheme and the resulting beneficial effect in the closed-orbit stabilization is discussed.<
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