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Description
A PrFeB-based cryogenic permanent-magnet undulator (CPMU) with 15 mm period length (CU15) is being constructed to provide high brilliant X-rays for the Taiwan Photon Source (TPS) nano-probe scope beamline. Field measurements of this undulator will be performed with a Hall probe in vacuum environment. The in-situ Hall probe measurement system is improved to measure and tune the magnetic field of the CU15. A field strength and temperature dependent calibration of the Hall probe is done to obtain the real field distributions.
By tuning the differential adjusters and spring modules, we can correct the magnetic field errors causing by assembly repr-ducibility and temperature gradients along magnetic arrays, lowering the phase errors to reach our design goals. This paper describes details of improvements in the measurement system, field tuning methods, and measurement results at cryogenic temperature.