Preparation of High Purity Niobium Ingot for RF Superconducting Cavity

The high purity niobium ingot for RF superconducting cavities was prepared by electron beam melting of more than three times under high vacuum. The obtained high pure niobium ingots have a purity more than 99.99% and an RRR value more than 300. The purity of the niobium ingots has reached the standard specifications of RF superconducting cavities. The RRR value of high purity niobium ingot is mainly affected by interstitial impurities such as H, N, O, and C. With increasing the times of electron beam melting, the interstitial impurities can be removed effectively, and the RRR values increase steadily. RRR value and impurity content should be combined to evaluate the quality of high purity niobium, since the impurity content alone is insufficient.