To complete the Italian In-Kind contribution to the ESS SRF Linac, we are working on the qualification of the last eight missing cavities. To achieve this, we are proceeding with reprocessing of not yet qualified cavities and, as a mitigation, we are constructing at the vendor four more cavities. In this paper, we report on the actual status of both of these activities with the most recent results.

To advance in the characterization of photocathodes for high brightness sources, the measurement of the thermal emittance plays a key role. The TRAnsverse Momentun Measurement device developed at INFN LASA will allow equipping our photocathode laboratory with an advance device able gving in quasi on-line feedback during the photocathode growth process. This paper reports on the status of the apparatus and its latest achievements.

INFN LASA photocathode lab develops and produces films that are used in high brightness photoinjectors. Besides the long-time and still on-going experience on Cs2Te, recently we have restarted an activity on alkali-antimonide films, sensitive to visible light, exploring the possibility of their stable operation in CW machine. We report in this paper the recent results obtained both on the advancements on cesium telluride and on the characterization of alkali antimonide.

The photoinjectors of FLASH at DESY (Hamburg, Germany) and the European XFEL are operated by laser driven RF-guns. In both facilities cesium telluride (Cs$_2$Te) photocathodes are successfully used since several years. We present recent data on the lifetime and quantum efficiency (QE) of the current photocathode at FLASH \#105.2, operated before and after a long shutdown. In addition, data for the cathodes that recently have been exchanged at the European XFEL will be presented.

We present the conceptual design of a compact light source named BriXSinO. BriXSinO was born as a demonstrator of the Marix project, but contains also a dual high flux radiation source Inverse Compton Source (ICS) of X-ray and a Free-Electron Laser Oscillator of THz spectral range radiation conceived for medica applications and general applied research. The accelerator is a push-pull CW-SC Energy Recovery Linac (ERL) based on the technology of superconducting cavities and allows to sustain MW-class beam power with al-most just one hundred kW active power dissipation/consumption. ICS line produces 33 keV monochromatic X-Rays via Compton scattering of the electron beam with a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz. The THz FEL oscillator is based on an undulator imbedded in optical cavity and generates THz wavelengths from 15 to 50 micron. The possibility of generating in the FEL cavity also synchronized X radiation is also shown.

A High Brightness Beams Test Facility has been recently funded at the INFN-LASA laboratory in Segrate (Milan- Italy). The Test Facility will allow to perform developments in ERL construction and design and to carry out experiments with the high current CW electron beam in frontier areas of accelerator physics. The Test Facility setup will comprise a high-performance laser driven DC Gun followed by a normal conducting RF buncher-acceleration section to provide 1 MeV 5 mA CW electron beam. A Superconducting RF booster linac able to increase the electron energies up to 5-10 MeV maintaining beam current up to 2.5 mA is part of the proposal for further funding.

As the series production of PIP-II 650 MHz low beta cavities approaches, INFN-LASA R&D activities on cavity prototypes are ongoing. Different surface treatments have been exploited in a joint effort between INFN and FNAL, to establish the series cavity recipe. Meanwhile, the vertical test facility has been upgraded for the test of high-Q cavities, by increasing its capability to reduce the trapped magnetic flux and by developing of a magnetic mapping system suitable in the cryostat environment. Here, we report the latest experimental results.