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March 25, 2004

Niobium Cavity Design
Dr. Yitung Chen , Qin Xue

Modeling and Optimization of the Chemical Etching Process in Niobium Cavities Niobium cavities are an important component of integrated NC/SC high-power linacs. Researchers in several countries have tested various cavity shapes and concluded that elliptically-shaped cells and buffered chemical polishing produce the best performance. The objective of this paper is to study and optomize the process on the effect of chemical etching on the surface roughness. Chemical etching of the inner surface of the cavity is achieved by circulating acid through it. The acid interacts with the surface and eliminates imperfections. During etching, the end of the cavity is blocked. A pipe with baffles is inserted within the cavity to direct the flow along the surfaces. A finite element computational fluid dynamics model is developed for the etching process. The problem is modeled as a two-dimensional, axisymmetric, steady state fluid flow problem. This model is used to study the parameters affecting the uniformity of the etching process, such as flow rate and geometry of the baffle. The model is parameterized so it can be used within an optimization program to improve quality of the surface finish.

Sponsor: Advanced Accelerator Application/University Particpation Program
Collaborator: Los Alamos National Laboratory



Nevada Center for Advanced Computational Methods