Upgrade of the SPARC_LAB LLRF system and recent X-band activities in view of EuPRAXIA@SPARC_LAB project
SPARC_LAB is a high-brightness electron photoinjector dedicated to FEL radiation production and research on novel acceleration techniques. It has been in operation at LNF since 2005. It is composed of a newly designed brazeless 1.6-cell S-band RF gun, two 3 meter long travelling wave S-band accelerating structures, and a 1.4 meter C-band structure that acts as an energy booster. Recently, a plasma interaction chamber was installed to study and optimize beam-driven plasma acceleration schemes. During fall 2023, a major upgrade of the entire low-level RF (LLRF) system will take place to consolidate and improve performance in terms of amplitude, phase resolution, and stability. The original analog S-band and the digital C-band LLRF systems will be replaced by commercial, temperature-stabilized, FPGA-controlled digital LLRF systems manufactured by Instrumentation Technologies. Additionally, the reference generation and distribution will be updated. In parallel with this activity, there is a growing interest in X-band LLRF at LNF due to the EuPRAXIA@SPARC\_LAB project. This project aims to build an FEL user facility driven by an X-band linac at LNF in the coming years. To test X-band RF structures and waveguide components, a high-power X-band test stand named TEX has been installed and recently commissioned. A detailed view of the TEX LLRF system, based on a commercial S-band system with a dedicated up/down-converter stage, will be discussed, along with the limitations of such an approach.