円筒形磁気シールドへのアクティブ・キャンセルの適用

概要

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We have improved the low-frequency axial shielding factor (ASF) of the open-ended cylindrical magnetic shield by incorporating the active canceling system to it. The amplitude and the phase of the incoming magnetic field to the shield were measured along the axis of the cylinder, and along lines on the inner and the outer surface of the cylinder in the frequency range 2 - 50 Hz. A simple feed-forward active canceling system has been developed, which consists of three canceling ring coils and a single monitoring flux-gate magnetometer. The magnetometer was located at a position on the outer surface of the magnetic cylinder, where the canceling magnetic field does not interfere to the magnetometer. The ASF achieved with active cancel was as high as 3000 at 2 Hz, 855 at 10 Hz and 113 at 50 Hz. These high ASFs can only be obtained with a longer magnetic cylinder if the active cancel is not employed.
2003-08-01