Study on casting niobium superconducting accelerating resonators

Cavity E010-resonators are the useful and convenient model when developing superconducting resonance structures of electron accelerators. The results of measurements of proper Q-factor and critical fields of superconducting E010-resonators and 10-cm short diaphramatic wave guides are presented. It is shown that residual surface resistance of cast niobium of the NσR-type can be decreased almost to the theoretical value. Application of the same methods of treatment to niobium of the NVCh-type allows to form the surface, resistance of which is almost by an order higher. The surface state and niobium cavity purity are discussed