Improved wire deflection method for magnetic field measurements in long undulators

Abstract

The method based on the deflection of a thin wire stretched through the investigated volume can be very useful for direct magnetic field measurements in undulators [1]. The first wire deflection systems did not provide high accuracy, for many reasons. To improve the method a new optical detector scheme [2] was introduced based on optical intensity measurement instead of direct wire position detection. With the above, an accuracy of magnetic field measurements comparable with that of high precision Hall probes was achieved [2]. The deviation of the wire from the ideal straight line leads to additional difficulties in the interpretation of the results. It becomes especially critical when the magnetic field changes significantly in distances comparable with the sag.