In-vacuum undulators at ESRF

Five in-vacuum undulators are currently in routine operation at the ESRF with a minimum gap of 5 mm to 6 mm. The results of the magnetic measurements are presented. The measured interaction with the stored beam (closed orbit distortion, lifetime) are discussed. Three additional devices are at present being constructed including a magnetic structure of hybrid type. They are all dedicated to operation at high photon energy above 50 keV and require an optimum spectrum shimming. The magnet temperature is permanently monitored in all different time filling modes of the ring. An estimation of the heat load deposited by the beam in the flexible input/output transition as well as in the copper sheet covering the magnet blocks is given.