Spectral quality of ALS U5.0 undulator and field error effects

The first insertion device of the Advanced Light Source (ALS), a U5.0 undulator, has been carefully adjusted and qualified with a specially designed magnetic measurement system. The magnetic field of the undulator has been fully mapped at a series of gaps with very high accuracy. Based upon these measured field data, we evaluate the radiation spectral quality of this device in terms of an ideal sinusoidal device and examine the field error effects. Moreover, the statistical correlation between the field errors and radiation degradation is examined by using the large quantity of magnetic field data sets accumulated in the process of adjusting and qualifying the U5.0 undulator