For the manufacture of six 217 MHz high-purity niobium (RRR>300) superconducting cavities, the required niobium material shall be supplied in accordance with the specified specification and the accompanying bill of materials.

The planned cavities have a wall thickness of 4 to 5 mm and are surrounded by helium jackets made of titanium. The production of the cavities requires extremely precise machining and shaping of the individual niobium sheets or the solid niobium material in compliance with the highest purity requirements in order to avoid contamination of the material during the manufacturing process. One of the biggest challenges is to achieve the required resonance frequency of the cavity within 0.10/00. To ensure this, the tolerances during bending/machining of the assemblies and the deformations during welding must be less than 0.15 mm.