Precise integration of undulator Hall probe scans

摘要

Procedures are described for obtaining precise magnetic field integral values for Hall probe scans of undulators. A technique is discussed for scaling the even portion of a nonlinear Hall probe calibration based upon sets of scans with the Hall probe installed in opposing orientations. An example is discussed where a 293 G-cm error is corrected by scaling which corresponds to an average adjustment of 0.7 G over a 3.0 T range. An analysis of measurement uncertainty is presented. A quantitative example is presented which shows that the expected level of uncertainty is of the order of 20 G-cm for undulator field integrals using the Advanced Light Source (ALS) magnet measurement facility. Sets of duplicate field integral measurements of ALS undulators demonstrate an accuracy and variation of results of better than 20 G-cm. A comparison of integrated Hall probe scans with integral coil measurements shows good agreement.