Buffered Electrochemical Polishing of Niobium

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The standard preparation of superconducting radio-frequency (SRF) cavities made of pure niobium include the removal of a 'damaged' surface layer, by buffered chemical polishing (BCP) or electropolishing (EP), after the cavities are formed. The performance of the cavities is characterized by a sharp degradation of the quality factor when the surface magnetic field exceeds about 90 mT, a phenomenon referred to as 'Q-drop'. In cavities made of polycrystalline fine grain (ASTM 5) niobium, the Q-drop can be significantly reduced by a low-temperature ({approx} 120 C) 'in-situ' baking of the cavity if the chemical treatment was EP rather than BCP. As ... continued below

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721-730

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Gianluigi Ciovati, Hui Tian, Sean Corcoran March 1, 2011.

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Description

The standard preparation of superconducting radio-frequency (SRF) cavities made of pure niobium include the removal of a 'damaged' surface layer, by buffered chemical polishing (BCP) or electropolishing (EP), after the cavities are formed. The performance of the cavities is characterized by a sharp degradation of the quality factor when the surface magnetic field exceeds about 90 mT, a phenomenon referred to as 'Q-drop'. In cavities made of polycrystalline fine grain (ASTM 5) niobium, the Q-drop can be significantly reduced by a low-temperature ({approx} 120 C) 'in-situ' baking of the cavity if the chemical treatment was EP rather than BCP. As part of the effort to understand this phenomenon, we investigated the effect of introducing a polarization potential during buffered chemical polishing, creating a process which is between the standard BCP and EP. While preliminary results on the application of this process to Nb cavities have been previously reported, in this contribution we focus on the characterization of this novel electrochemical process by measuring polarization curves, etching rates, surface finish, electrochemical impedance and the effects of temperature and electrolyte composition. In particular, it is shown that the anodic potential of Nb during BCP reduces the etching rate and improves the surface finish.

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721-730

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  • Journal Name: Journal of Applied Electrochemistry; Journal Volume: 41; Journal Issue: 6

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  • Report No.: JLAB-ACC-09-1026
  • Report No.: DOE/OR/23177-0852
  • Grant Number: AC05-06OR23177
  • DOI: 10.1007/s10800-011-0286-z | External Link
  • Office of Scientific & Technical Information Report Number: 1032483
  • Archival Resource Key: ark:/67531/metadc836325

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • March 1, 2011

Added to The UNT Digital Library

  • May 19, 2016, 3:16 p.m.

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  • Aug. 3, 2016, 6:17 p.m.

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Gianluigi Ciovati, Hui Tian, Sean Corcoran. Buffered Electrochemical Polishing of Niobium, article, March 1, 2011; Newport News, Virginia. (digital.library.unt.edu/ark:/67531/metadc836325/: accessed December 12, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.