Vertical electropolishing station
Context
Chemical and electrochemical treatment of elliptical cavities (maximum cavity height: 1.8 m and maximum mass: 200 kg).
This station allows one to perform chemical or electrochemical polishing of the internal surface of niobium cavities.
Technical means
- Power supply: 20 V, 1200 A,
- Acid flow rate: 40 l / min,
- 300 l acid tank,
- Pipe and pumps made of PFA material, teflon coating of the acid tank,
- Cavities are handled by a crane with specific tooling for each cavity. The station is also equipped with a table for horizontally inserting the cathodes,
- Use of rotating cathode for uniform material removal,
- External cooling of the cavity with water sprays,
- Online measurement of the cavity thickness during treatment.
Electropolishing cycles are automated.
The station is located in a Non-Explosive Atmosphere Area. Measures are taken to limit the various sources of risk:
- Hydrogen detection via 2 detectors with automated shut-off of the generator and ventilation of the treatment booth which ensures a low concentration of process gases in the event of a leak,
- Control of the acid temperature (via an 18 kW power cooling unit connected to a heat exchanger: 156 m PFA pipe) to minimize the risks associated with exothermic reactions (the working temperature is below 20 °).
Additional facilities: acid storage room, gas extractor-washer which ensures the ventilation of workstations, acid liquid waste collection and treatment system, pure and ultrapure water treatment plant (resistivity : 17.7-17.9 MΩ.cm).
Vertical electropolishing cabinet
Achievements, related projects
- Treatment performed to increase the surface quality of superconducting cavities, in the framework of the XFEL, ESS and ILC projects,
- R&D experiments on vertical electropolishing,
- Preparation for other R&D related activities: doping, multilayer, coating.
Technical steps, expertise
- Vertical positioning of the cavity,
- Chemical or electrochemical treatment (automated cycle),
- Rinsing with ultrapure water (resistivity: 17.9 MΩ.cm) and extraction of acids and polluted water.
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