Improvements of the pulsed-wire method to measure undulators

In this paper, we will present the Pulsed-Wire Method (PWM) for undulators measurements used for the first crossed overlapped electromagnetic undulato r OPHeLIE. This method gives directly the first integral of the magnetic fi eld by use of short current pulse and the second integral using a step curr ent pulse through the wire. We characterized OPHeLIE by use of the second i ntegral mode to optimize the beam trajectory in the respect of specificatio ns. There was a good correlation between these results and those obtained f rom the on-beam test. We were therefore encouraged to further develop this method to determine optical performances of undulators. In order to validat e this approach we compared spectrum determined by pulsed-wire technique an d Hall probe scans, used as reference, applied both to the OPHeLIE prototyp e, which is a shorter planar version. For the PWM, we used the short curren t pulse according to the undulator's period (the fil st integral mode). An introduction of digital data processing techniques has been used to improve the signal-to-noise ratio, to minimize the effect of the background vibrat ions and characterize the wire's response.