Current status of the spoke cavity prototyping for the JAEA-ADS linac

Tamura, Jun; Kondo, Yasuhiro   ; Yee-Rendon, B. ; Meigo, Shinichiro   ; Maekawa, Fujio  ; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Domae, Takeshi*

The Japan Atomic Energy Agency (JAEA) has proposed an accelerator-driven subcritical system (ADS) to efficiently reduce high-level radioactive waste generated at nuclear power plants. One of the challenging R&D aspects of ADS is the reliability of the accelerator. In preparation for the full-scale design of the CW proton linac for the JAEA-ADS, we are now prototyping a low-beta (around 0.2) single spoke cavity. Since there is no experience in Japan in manufacturing a superconducting spoke cavity, prototyping and performance testing of the cavity is essential to ensure the feasibility of the JAEA-ADS linac. In the Japanese fiscal year 2021, we have started welding cavity parts together. By preliminarily examining the electron beam welding conditions, each press-formed niobium part was joined with a smooth welding bead. At present, we have fabricated the cavity's body part.