Recent developments of insertion devices at the ESRF

57 Insertion Devices (IDs) segments are now in operation in the ESRF Storage Ring serving 29 beamlines. A review of the present situation is made together with a detailed description of the recently built in-vacuum undulator. The mechanical and magnetic designs together with the pumping and conditioning with beam are described. No lifetime reduction is observed for any magnetic gap larger than 6 mm. A summary is made of the most important properties of several new innovative IDs including the 3T permanent magnet wiggler, the quasi-periodic undulator and the fast switching helical undulator.