SPIDER is the 100 keV full-size Negative Ion Source prototype of the ITER Neutral Beam Injector, operating at Consorzio RFX in Padova, Italy. The largest Negative Ion Source in the world, SPIDER generates an RF driven plasma from which Deuterium or Hydrogen negative ions are produced and extracted. At the end of 2021, a scheduled long-term shutdown started to introduce major modifications and improvements aiming to solve issues and drawbacks identified during the first three years of SPIDER operations. The first action of the shutdown period was the disassembly and characterization of the SPIDER beam source after removal from the vacuum vessel and its placement inside the clean room. Each component was carefully assessed and catalogued, following a documented procedure. Some source components, i.e., the Plasma Grid, Extraction Grid and Bias Plate, revealed the presence of different and non-uniform red, white and green coatings that might be correlated to back-streaming positive ions impinging on grid surfaces, electrical discharges and caesium evaporation. Thus, several analyses have been carried out to understand the nature of such coatings, with the study still ongoing. The evidence of caesium evaporation and deposition on molybdenum-coated SPIDER components, such as the formation of oxides and hydroxides, is demonstrated through surface characterization analyses with the use of the Scanning Electron Microscope (SEM), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS).

No abstract

No abstract

Additive manufacturing (AM) is revolutionizing the industrial scenario. Four copper samples have been printed via Laser Powder Bed Fusion (LPBF) at DIAM Laboratory (INFN—Sezione di Padova, Padova, Italy). Samples had different geometrical characteristics, to test the feasibility of the AM as a productive technique for the creation of unsupported copper structures that are characterized by surfaces with a very small inclination angle, where supports cannot be placed. Parts have been printed successfully even in case of 18° of inclination of unsupported walls with respect to the horizontal plane, and on the same samples, surface finishing treatments (performed by Rösler Italiana S.r.l. and INFN-LNL) have been performed to reduce the roughness of the down-facing surfaces. Indeed, the down-skin regions are the most critical areas of AM parts. Several surface treatments are under investigation: mass-finishing treatments (mechanical and chemically assisted mechanical processes), chemical polishing, and electropolishing, and for some of them, the results are extremely positive: from an initial roughness (Ra) of 30–35 µm, the treatments allowed us to achieve a Ra value lower than 1 µm. The study here exposed presents a good way to rapidly reduce the roughness of 3D-printed parts, reaching a mirror-like aspect.