A successful establishment of the new ERL mode currently under development at S-DALINAC requires an improved beam quality of the injector, especially in regard to bunch length and energy spread. Furthermore, to re-enable an usage of the spin-polarized photo-gun, the low-energy acceptance has to be expanded. To address these issues, the first superconducting injector cavity will be replaced by a beta-adapted capture structure in order to improve the acceleration of electrons from the normal-conducting low-energy transport section. The project focuses on the technical implementation of the upgrade, including cavity manufacturing, modifications of the cryomodule, testing, installation and commissioning of the structure. Additionally, a new diagnostics beamline was installed upstream of the capture cavity. This setup allows for an detailed characterization of the bunches entering the superconducting injector, which supports refined beam dynamics simulations and a reliable setup of the machine.

The project is in the final phase before completion, with the cavity ready for installation and the diagnostics line commissioned. First beam in the upgraded injector is expected in spring 2021.