Speaker
Description
In previous editions of this workshop, we demonstrated that Plasma Electrolytic Polishing (PEP) works well as a surface-finishing route for small niobium coupons, offering effective smoothing with environmentally benign electrolytes while avoiding aggressive HF-based acids. Scaling the process to larger surfaces, however, proved far less straightforward: results were inconsistent and difficult to reproduce, with recurring issues such as surface oxidation and non-uniform oxide staining that ultimately made the treated surfaces unusable.
In this contribution, we show how these limitations have been overcome through a revised electrolyte formulation, voltage tuning, and mixing protocol developed at INFN-LNL, which suppresses oxide formation and restores stable, reproducible polishing on larger workpieces.
The improved process delivers smooth, reflective surfaces with average roughness reduced from above 3 µm down to below 100 nm Sa. We present results obtained on medium-sized samples up to approximately 10 × 5 cm and on QPR niobium samples, possibly including RF measurements if timing allows, and we show that the process is equally applicable to 3D-printed niobium samples.
Finally, we report on the first steps toward the internal surfaces polishing of elliptical cavities, with a preliminary test on dummy samples.