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Fundamental Study of Micro-Defects in Electropolished EB-Welded and Hydroformed SRF Accelerating Structures. Final Report.

DE141150839

Publication Date	2014
Personal Author	Sumption, M. D.
Page Count	37
Abstract	In the area of niobium elecroploshing fundamentals, we focused on undersanding the influence of the surface topology, and geometry with effects from gravity included. The formation of a viscous film is essential for the electropolishing process to take place. The exact nature and composition of the film formed on niobium is still unknown because of its solubility in the electrolyte. Extensive pitting may take place at surface where a stable film cannot form. This has to be taken into consideration while determining the speed with which the SRF cavities are rotated while EP. Hydrodynamic aspects must be taken into consideration while optimizing the polishing parameters. There is improvement in surface finish with polishing time. There is a huge change in surface quality when the EP time is increased from 2 hours to 4 hours but not much change takes place when the time is further increased to 6 hours. So keeping the economic points in view, about 100 um defect layer removal may be sufficient to get the desired performance. In the area of Electropolishing of untreated and treated niobium with Weld Joints we studied untreated and treated Nb, especially for the heat affected areas next to welded bumps, electropolished for different durations. The electropolishing of the untreated Nb caused the formation of pits on the surface at about 15 min but they disappeared when the electropolishing duration was more than 15 min.
Keywords	Superconducting cavity resonators Defects Electrolytes Electrons Electropolishing Gradients Hadrons Linear accelerators Niobium Reliability Synchrotrons Welding
Source Agency	Technical Information Center Oak Ridge Tennessee
NTIS Subject Category	46 - Physics
Corporate Authors	Department of Energy, Washington, DC. Office of High Energy and Nuclear Physics.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	201503
Contract Number	DE-SC0004217

Fundamental Study of Micro-Defects in Electropolished EB-Welded and Hydroformed SRF Accelerating Structures. Final Report.

Fundamental Study of Micro-Defects in Electropolished EB-Welded and Hydroformed SRF Accelerating Structures. Final Report.
DE141150839

Publication Date	2014
Personal Author	Sumption, M. D.
Page Count	37
Abstract	In the area of niobium elecroploshing fundamentals, we focused on undersanding the influence of the surface topology, and geometry with effects from gravity included. The formation of a viscous film is essential for the electropolishing process to take place. The exact nature and composition of the film formed on niobium is still unknown because of its solubility in the electrolyte. Extensive pitting may take place at surface where a stable film cannot form. This has to be taken into consideration while determining the speed with which the SRF cavities are rotated while EP. Hydrodynamic aspects must be taken into consideration while optimizing the polishing parameters. There is improvement in surface finish with polishing time. There is a huge change in surface quality when the EP time is increased from 2 hours to 4 hours but not much change takes place when the time is further increased to 6 hours. So keeping the economic points in view, about 100 um defect layer removal may be sufficient to get the desired performance. In the area of Electropolishing of untreated and treated niobium with Weld Joints we studied untreated and treated Nb, especially for the heat affected areas next to welded bumps, electropolished for different durations. The electropolishing of the untreated Nb caused the formation of pits on the surface at about 15 min but they disappeared when the electropolishing duration was more than 15 min.
Keywords	Superconducting cavity resonators Defects Electrolytes Electrons Electropolishing Gradients Hadrons Linear accelerators Niobium Reliability Synchrotrons Welding
Source Agency	Technical Information Center Oak Ridge Tennessee
NTIS Subject Category	46 - Physics
Corporate Authors	Department of Energy, Washington, DC. Office of High Energy and Nuclear Physics.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	201503
Contract Number	DE-SC0004217