FROO07 　加速構造②　 9月4日 講演会場１ 17:20-17:40

4 K 高 Q 値運転可能な超伝導加速空洞のための電気メッキ法による Nb3Sn 成膜

Nb3Sn Formation Using Electroplating Method for 4 K HIGH-Q Operable SRF Cavity

○井藤 隼人，早野 仁司，文珠四郎 秀昭（高エネルギー加速器研究機構），柏木 茂，本多 史憲（東北大学），菊池 章弘（物質・材料研究機構）

○Hayato Ito, Hitoshi Hayano, Hideaki Monjushiro (KEK), Shigeru Kashiwagi, Fuminori Honda (Tohoku University), Akihiro Kikuchi (NIMS)

Forming Nb3Sn onto the inner surface of the SRF cavity allows us to operate the cavity with 1010 Q value at around 4 K instead of the usual 2 K operation, since Nb3Sn becomes superconducting at twice as high temperature as standard SRF material Nb. Also, the superheating field Hsh of Nb3Sn is twice as that of Nb. Here, Hsh is the ultimate limit for an ideal superconductor. this twice Hsh would mean an accelerating gradient of nearly 100 MV/m, which would be extremely beneficial accelerator applications. However, this gradient is far from being realized and alternative formation methods is expected instead of the conventional method. An electroplating method has been developed at FNAL for pursuing the promise of the alternative method. In order to advance the research on this method, KEK has started electroplating of Nb3Sn with the same method but different plating solutions under the US-Japan cooperation. The thermal treatment and characterization of Nb3Sn samples have been performed in the cooperation of NIMS and Tohoku University. In this paper, the evaluation of the Nb3Sn samples and the progress on surface treatments since the year 2019 are reported.