In the framework of Future Circular Collider study, copper coated with niobium cavities must be fabricated to operate at a frequency of 400MHz. The two half-cells, to make one cavity, are traditionally manufactured by spinning through multiple forming steps, comprising intermediates heat treatments to achieve the required shape. Finally, the two half-cells are welded at the equator by electron-beam welding.
Shape conformity and processing time are key factors for the optimization of cavity fabrication. An alternative to conventional shaping method is electrohydraulic forming (EHF). By EHF, half-cells are obtained through ultra-high speed deformation of blank sheets, using shockwaves induced in water by a pulsed electrical discharge. With reference to traditional methods, this process brings about interesting results in terms of final shape precision, repeatability, higher formability and reduced spring back. This shaping technology has been tested at CERN for smaller half-cells (704MHz) and promising results were achieved in terms of shape accuracy and damaged layer in the material after forming.
In this work, large half-cells of Cu are produced by EHF for the first time. This new method and the conventional one (spinning) are compared regarding shape accuracy, mechanical properties and material characterization.