Speaker
Description
Hall sensors are used to measure magnetic field profiles of undulators for synchrotron radiation sources. They are typically calibrated with a standard dipole magnet and a Nuclear Magnetic Resonance (NMR) Teslameter to obtain the magnetic field to voltage relationshipDue to the alternating nature of the magnetic field profile in an undulator a small error might result in a significant change in the measured field integrals. This would lead to inaccurate trajectories which is especially detrimental for multi-undulator applications such as FELs or in-line undulator configurations in storage rings. To overcome this issue, we developed a technique by using undulator gap-dependent magnetic field measurements with both the Hall sensor and a long coil field integral measurement system to derive refined corrections to the Hall probe calibration file. We describe the technique in detail and report on results of several in-line undulator measurements performed at the Advanced Photon Source.