Thermodynamic Evaluation of Hydrogen Absorption by Niobium During SRF Fabrication

Published

June 30, 2011

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

Pub Type

Conferences

Download Paper

https://doi.org/10.1063/1.3579223

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 December 14, 2024)