Specific heat treatments applied to superconducting radio-frequency (SRF) cavities, such as nitrogen infusion or Mid-T baking, aim to improve the quality factor (Qo) at medium accelerating fields (˜10–20 MV/m). These treatments reduce the BCS surface resistance by tuning the mean free path of niobium over a few hundred nanometers, either by diffusing oxygen from the native oxide layer or by diffusing nitrogen after the dissolution of the oxide layer. However, these treatments preclude the usual chemical polishing, as it would reverse the beneficial effects of the heat treatments, making the cavities highly sensitive to surface contamination. In particular, the formation of niobium carbides, which can mask the expected benefits, strongly depends on the annealing conditions, surface preparation, and the material’s history. To better understand these phenomena, niobium samples was annealed under ultrahigh vacuum (Mid-T baking) with plasma treatment to investigate surface contamination with *in-situ* heat treatment and XPS analysis.

Specific heat treatments applied to superconducting radio-frequency (SRF) cavities, such as nitrogen infusion or Mid-T baking, aim to improve the quality factor (Qo) at medium accelerating fields (˜10–20 MV/m). These treatments reduce the BCS surface resistance by tuning the mean free path of niobium over a few hundred nanometers, either by diffusing oxygen from the native oxide layer or by diffusing nitrogen after the dissolution of the oxide layer. However, these treatments preclude the usual chemical polishing, as it would reverse the beneficial effects of the heat treatments, making the cavities highly sensitive to surface contamination. In particular, the formation of niobium carbides, which can mask the expected benefits, strongly depends on the annealing conditions, surface preparation, and the material’s history. To better understand these phenomena, niobium samples was annealed under ultrahigh vacuum (Mid-T baking) with plasma treatment to investigate surface contamination with *in-situ* heat treatment and XPS analysis.

Modern particle accelerators, while enabling cutting-edge research, face major challenges in energy efficiency and beam intensity. The PERLE (Powerful Energy Recovery Linac for Experiments) project, developed at IJCLab/CNRS, aims to demonstrate a high-current energy recovery linac (ERL) using superconducting RF technology. By recovering the beam energy after use, PERLE drastically reduces RF power consumption and cryogenic load, paving the way for sustainable, high-performance accelerators. A key element is the development of alkali-antimonide photocathodes, combining high quantum efficiency and low thermal emittance. CsK₂Sb photocathodes, in particular, show excellent response to visible light, enabling operation with lower laser power and improved beam quality. Their fabrication relies on a unique deposition system equipped with a dedicated transfer line that links the glove box—where precursors are prepared—to the molecular beam epitaxy (MBE) chamber for growth, and ultimately to the electron gun for installation. Preliminary tests at IJCLab achieved a quantum efficiency of 3 %, validating this integrated approach for high-current ERLs such as PERLE.

In an Energy Recovery Linac (ERL), the beam, after acceleration and interaction, is recirculated and decelerated in the accelerating cavities of the linac. In such a scheme, the power of the beam is recovered within the SRF cavities, leading to substantial savings in electrical power. PERLE (Power Energy Recovery Linac for Experiments) is a high-power ERL demonstrator in Orsay, aiming to investigate multi-turn energy recovery. The electron beam can be recirculated in a superconducting linac up to 250 MeV (802 MHz). The high intensity electron beam (20 mA) is created by a photoinjector comprising a DC gun, a RF buncher, a SRF booster (7 MeV) and a merging section. The gun aims to produce 500 pC bunches at 40 MHz to inject the ERL ring with photocathodes of bi-alkali material (CsKSb). The photocathodes are deposited in a preparation facility (PPF) consisting of a molecular beam epitaxy (MBE) chamber for growth, linked via transfer lines to a glove box for precursor preparation and to the gun vacuum chamber. With this unique system, photocathodes can be prepared and loaded into the gun chamber under excellent vacuum conditions. Green light at 515 nm is used to produce electron bunch from the photocathode. The gun will be operated at 350 kV using as insulating gas N2 instead of SF6, a potent greenhouse effect gas. The photogun and its PPF, are installed at IJCLab- Orsay (France). The commissioning, currently underway, will be presented.