Recent Developments in Insertion Devices at the ESRF: Working Toward Diffraction-Limited Storage Rings

The development of permanent-magnet insertion devices (IDs) is a feature of third-generation light sources (3GLS). Since the early 1990s, an important research and engineering effort has been carried out on various types of undulators at the ESRF, as in many other 3GLS facilities. We are presently at the forefront of an interesting migration toward new storage ring lattices with ultra-low horizontal emittance 1 M. Erikson, Journal of Synchrotron Radiation, 21(5), 837–842 (2014).Crossref], PubMed], Web of Science ®] , Google Scholar], 2 M. Borland, Synchrotron Radiation News, 27(6), 2–31 (2014).Taylor &; Francis Online] , Google Scholar]]. The upgrade of the ESRF accelerator will take place before 2020. A new magnet lattice comprising seven bending magnets per cell will replace the existing DBA structure, leading to a dramatic reduction of the horizontal emittance from 4 nm to about 130 pm. Because the new ring will be operated at the same energy as the current ring, the majority of existing IDs will be used in the upgraded ring, at least as a starting point. From the present state of the art in ID technology, one can obviously identify the development of very short-period, small-gap undulators as potential major X-ray sources in such new storage rings. Technically, various methods in magnetic field processing and correction need to be revisited and possibly updated.