The synchrotron SOLEIL is both a 2.75 GeV third-generation synchrotron light source and a research laboratory at the forefront of experimental techniques dedicated to matter analysis down to the atomic scale, as well as a service platform open to all scientific and industrial communities. We present the performance of the accelerators delivering extremely stable photon beams to 29 beamlines. The beam delivery schedule and the operation have been affected by the energy crisis. Shortages of cryogenic fluids and electronic components, coupled with a high inflation, are impacting the operation budget and the related projects. The update on the construction of the new low-energy footprint cooling station is presented. Finally, new developments and testing of prototype equipment related to the upgrade of the injector complex and the main storage ring are discussed.

The Upgrade from the third to the fourth-generation light source of the SOLEIL synchrotron requires significant work on the reorganization of the equipment in the storage ring. Higher performance such as low emittance, small transverse size and high brightness are expected but requires redesigning the lattice. New constraints appear, requiring innovative designs of insertion device (ID) in order to keep the spectral range currently offered to users as large as today. The current straight sections can welcome two juxtaposed undulators to allow the beamline to cover a wide spectral range. However, the average space of straight sections dedicated to ID of SOLEIL II will be decreased in the future by 30%. SOLEIL Insertion Group studied several technical solutions combining two magnetic periods in a shorter space. Bi-periodic undulator project would make it possible to design a unique compact device with special magnet arrangement allowing to operate the ID alternatively with one periodicity to its triple value by means of longitudinal displacement of magnet arrays. Such an undulator enables to cover a wide spectral range of photons and only requires short space. A complete magnetic design with magnetic and spectral/optical performance will be presented and compared to usual solutions. Impact on the electron beam dynamics and magnetic forces will be also considered to have a complete knowledge on the feasibility of this project.

Developing Free Electron Lasers using Laser Plasma Acceleration open great hopes for compact laboratory scale light sources. The COXINEL line developed at Synchrotron SOLEIL (France) has been moved at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) (Germany) for using high-quality electron beam generated by the 150 TW DRACO laser. After proper electron beam transport, seed and undulator radiation temporal, spectral and spatial overlaps, the seeded Free Electron Laser driven by the DRACO laser plasma accelerator has been observed in the UV. Good agreement is found between measurements and simulations.