Adjustment and measurement of a hybrid undulator

Adjustment and measurement of a hybrid undulator have been discussed. The magnetic field quality is limited by factors such as inhomogeneities of the permanent magnets, fabrications and assembly errors. Considering these factors, re-sorting of aluminum holders using the simulated annealing method and iron shimming have been used for the adjustment of the undulator. The measured rms field error was reduced from 3% to 0.3%, the electron trajectory deviation is around 0.1 mm. During our magnetic measurement, a small variation of magnetic period length was observed. An approach to reduce the deviation of the relative phase of electrons in the ponderomotive potential, which will lead to the reduction of laser gain degradation due to magnetic field errors is also discussed