Performances of OPHELIE : a new type of undulator at LURE

The first electromagnetic Onuki-type undulator has been operating on the 80 0 MeV storage ring Super-ACO since spring of 1998. It consists of two cross ed overlapped, 2.7 meter long, undulators able to produce any kind of polar ized light in the VUV energy range with a switching rate of 1 Hz, The maxim um magnetic field of 0.12 T is produced in both planes by the mean of bipol ar +/- 210 A/+/- 190 V and monopolar 210 A/135 V power supplies. The undula tor producing vertical magnetic field can be shifted along longitudinal axi s in order to change the phase of magnetic fields. Main design is summarize d: mechanical structure, different sets of correcting coils, water cooling. Magnetic measurement results obtained by different methods are described, in particular, the tuning of the beam transverse excursion according to the main current variations and the flux capture effect when the phase is chan ging. A good agreement was found between magnetic measurements, calculation s and on-beam tests.