Electro-Pulse Nb SRF Cavities

For particle accelerators that use superconducting RF (SRF) cavities there is a need to develop new fabrication and processing techniques for niobium cavities to reduce the cost and improve quality factor and accelerating gradient. Nb based SRF cavities are presently manufactured by a forming and e-beam welding approach which requires a large number of EB welds followed by extensive surface cleaning and etching processes which often include electro- polishing with acid as well as high temperature anneals. A route which can directly form Nb based SRF cavities is of great interest, both for reduced processing, but also reduced waste, thus reducing the number of cavities that do not hit specification. Of interest would be a technique for directly forming the final RF cavity shape with techniques that maximize deformation. In this Phase I, We will develop an Impulse-forming and/or Impulse manufacturing methods that uses high pressure and high speed metalworking that can dramatically improve formability, decrease material damage and improve dimensional tolerance versus conventional methods. This Phase I SBIR will demonstrate the applicability of the vaporizing foil method for the fabrication of SRF Cavities. In this method, the forming pressure is generated by electrically-driven rapid vaporization of a thin metallic conductor, which is in the form of a foil or a wire. Several different media will be explored, including liquid and solid. Such forming methods have been previously demonstrated on flat Nb workpieces to deform them into half-cells which can be welded together. However, the real promise of this approach is the direct formation of cavities with no welds over a nine-cell length. The impulse approach will be used to increase the deformation of the Nb, so that the dual forming and necking processes such as that needed for hydroformed cavities are avoided. According to a U.S. EPA article, more than 97% of the 15,000 accelerators in use around the world have commercial applications, e.g. in the diagnosis and treatment of cancer, the locating of oil and minerals in the earth, the processing of semiconductor chips for computers, the determination of the age of materials through radiocarbon dating, the sterilizing of medical equipment and food products.