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Thermodynamic Evaluation of Hydrogen Absorption by Niobium During SRF Fabrication

Published

Author(s)

Richard E. Ricker, Ganapati R. Myneni

Abstract

The properties and performance of the ultra high purity Nb used to fabricate superconducting radio frequency (SRF) particle accelerator cavities have been found to vary with processing conditions. One hypothesis for these variations is that hydrogen, absorbed during processing, is responsible for this behavior. The key assumption behind this hypothesis is that niobium can absorb hydrogen from one or more of the processing environments. This paper reviews work examining the validity of this assumption. It was determined that Nb will spontaneously react with water producing adsorbed atomic hydrogen that is readily absorbed into the metal. The passivating oxide film normally prevents this reaction, but this film is frequently removed during processing and it is attacked by the fluoride ion used in the polishing solutions for SRF cavities. However, during electropolishing that cathodic reduction of hydrogen is transferred to the auxiliary electrode and this should suppress hydrogen absorption.
Proceedings Title
Symposium on the Superconducting Science & Technology of Ingot Niobium
Conference Dates
September 22-24, 2010
Conference Location
Newport News, VA
Conference Title
First International Symposium on the Superconducting Science & Technology of Ingot Niobium 2010

Keywords

Superconducting niobium, fabrication, chemical polishing, electropolishing, hydrogen absorption

Citation

Ricker, R. and Myneni, G. (2011), Thermodynamic Evaluation of Hydrogen Absorption by Niobium During SRF Fabrication, Symposium on the Superconducting Science & Technology of Ingot Niobium, Newport News, VA, [online], https://doi.org/10.1063/1.3579223 (Accessed April 17, 2024)
Created June 30, 2011, Updated November 10, 2018