HIGH-PRECISION HARMONIC MAGNETIC-FIELD MEASUREMENT AND ANALYSIS USINGA FIXED ANGLE HALL PROBE

A special theoretical concept involving the harmonic magnetic-field me asurement and analysis method using a fixed angle Hall probe was devel oped at the Synchrotron Radiation Research Center (SRRC) for measuring as well as analyzing the triple bending achromat magnets of the stora ge ring. The method can be used to simulate the harmonic magnetic-fiel d calculation of the two-dimensional (2D) ''MAGNET'' program. This met hod has a quite simple mechanism. The Hall plate was fixed at a 0 degr ees angle with respect to the horizontal plane of magnet to measure on ly the vertical field. Additionally, the 2D nonlinear least-square fit ting was used to fit the mapping data so as to find the normal and ske w multipole field strength. If necessary, the angle of Hall probe coul d be rotated 90 degrees precisely for measuring the horizontal field. Consequently, the skew dipole field could be obtained. A real-time Hal l-probe automatic magnetic-field measurement system was also developed for fulfilling the concept of the harmonic field measurement. Some sp ecial mapping trajectories for different kinds of magnets were discuss ed to match this special theoretical concept with the analysis methodo logy. This was done so as to obtain the reliable and accurate harmonic field strength. The accuracy and precision of the harmonic field stre ngth measurement and analysis of this method being better than +/-0.01 % was confirmed by experimental results.