Metallurgical and Technological Request for High Purity Niobium in SRF Application
- Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22607 Hamburg (Germany)
Properties of niobium are analyzed regarding application in superconducting radio frequency accelerator systems. High purity niobium should meet the tough specification. Interstitially dissolved impurities like oxygen, nitrogen and carbon should be kept under few wt. ppm. Hydrogen can under definite condition significantly reduce the cavity quality factor (hydrogen decease) and should be carefully controlled during fabrication as well as during cavity treatment. The main metallic impurity is tantalum. Clusters of foreign material can essentially deteriorate the cavity performance. An eddy current scanning system with rotating table is applied for diagnostic of foreign material inclusions and cracks in niobium sheets. In addition the acceptance tests for Nb sheets include the RRR (RRR - Residual Resistivity Ratio) measurement, microstructure analysis, analysis of interstitial and metallic impurities, hardness measurement and tensile test.High thermal conductivity in the cavity wall in order to guide the dissipated RF power away is required. It can be additionally improved almost by one order of magnitude during the post purification (solid state gettering) applied for Tesla Test Facility TTF cavities at DESY. The cavities are heated to 1350-1400 deg. C and a thin titanium layer is evaporated on the surface. Softening of Nb and grain growth is the main drawback of the purification annealing.
- OSTI ID:
- 20798722
- Journal Information:
- AIP Conference Proceedings, Vol. 837, Issue 1; Conference: 2. international symposium on hydrogen in matter (ISOHIM), Uppsala (Sweden), 13-17 Jun 2005; Other Information: DOI: 10.1063/1.2213059; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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