Electro-polished cavities using china ningxia large grain niobium material

For the International Linear Collider (ILC), superconducting RF cavity technology was chosen. The superconducting cavity is made of polycrystalline niobium material so far. However, the material cost is high and the cavity performance has a rather scatter now. Large grain (LG) niobium cavity has the potential of simplifying the production and reducing the cost of the superconducting RF cavities for the ILC. To investigate the feasibility of fabrication and the possibility to achieve high gradient by LG cavities, three single-cell cavities were made of China Ningxia LG niobium. A series of vertical tests has been carried out on several different surfaces treatment procedures by electro polishing. One cavity has reached the high gradient of more than 43 MV/m repeatedly. The maximum accelerating field of 47.9 MV/m has been achieved. This paper describes the features of electro polishing on China Ningxia LG niobium and presents the preliminary results of the research.