High-precision Hall sensor array magnetic field measurement system

A Hall sensor array magnetic field measurement system consists of 16 HHP-MU [1] Hall sensors powered by a Keithley 6220 precision current source, which has been built and deployed at SSRF [2]. The voltages of the 16 sensors are sampled by 4 NI PCI-4462 and further converted to the magnetic field strength. The sensors mounted on a high-precision three-dimensional translating stage are used to scan the surface of a magnet block with the step-length of 1 mm. The surface field distributions of the magnet blocks within an in-vacuum undulator are obtainable using this system. Based on the data measured, the magnet blocks are sorted and installed on the undulator girders. The magnetic measurement results of this undulator indicate that this sorting strategy works well.