Seamless SRF Cavity Fabrication by Spin-Necking and Hydroforming

Superconducting radio frequency (SRF) cavities for use in the International Linear Collider (ILC) are currently fabricated by electron-beam welding of press-formed half-cell cups. Cavities produced in this method experience weld-related defects that limit accelerator performance and increase the cost of supplying the SRF system to the end user. E-beam welding in its optimum state is expensive and causes additional manufacturing risk and lead time. This project will develop a weld-free cavity forming process which will eliminate welds and weld-related defects and therefore reduce cavity cost. The primary reference model will be the 1.3 GHz 9-cell TESLA-style SRF cavity but the objective will be to produce a 3-cell cavity. The sequential forming processes of spin-necking and hydroforming will be employed to produce cavities from a single, weld-free tube of cavity metal. Cavity irises and equators will be mechanically formed on a spinning machine and ultimately a hydroforming press to produce final cavity geometry. Copper will be employed for this Phase I project. The Work Plan objective is to produce a spin- necked perform portion of the seamless cavity forming process, leaving the hydroform stage to a Phase II work plan. However, hydroform tooling system design will be performed in the Phase I Work Plan so that the system will be ready for construction in the proposed Phase II and III commercialization stages of the project. The Phase I Work Plan will verify methods development previously performed by Proposer through numerical analysis of spin-necking and hydroforming and then operate a spin-necking process to produce a spin-necked tube, ready for the subsequent hydroform process.