Hall Element Relative Position and Angle Calibrations for the Cryogenic Permanent Magnet Undulator

A three dimensions Hall probe has be manufactured for characterizing the magnetic performance of Cryogenic Permanent Magnet Undulator (CPMU) of Chinese High Energy Photon Source (HEPS) at Institute of High Energy Physics (IHEP). The positional and angular misalignment errors of the Hall sensors play an important role in the measurement accuracy of CPMU. In order to minimize the misalignment errors, a method of calibrating relative displacements and assembly angles of a 3-D Hall probe is carried out. In this paper, details of the calibration procedures and the data processing are presented. INTRODUCTION Chinese High Energy Photon Source (HEPS) is a 6 GeV third generation synchrotron radiation facility with ultralow emittance and extremely high brightness [1] [2]. In the straight sections, several Cryogenic Permanent Magnet Undulator (CPMU) will be installed to deliver a high-performance X-ray [1]. The CPMU is a full scale invacuum undulator with a period of 12 mm and a magnetic length of 1.6 m. With a gap of 5 mm and cryogenic temperatures of 83 K, the target peak field achieved will be more than 0.8 T. Since the RMS phase error and the field integrals of CPMU have a strong influence on the spectral flux and the closed orbit. The precise measurement of the magnetic quantities is essential to characterize magnetic errors [3]. A Hall bench used to measure the CPMU magnetic field are under development. Table 1 shows the specifications of the in-vacuum Hall probe bench. Table 1: Specifications of the in-vacuum Hall probe bench