Development of microwave cavities for measurement of muonium hyperfine structure at J-PARC. - Tanaka, K S; Iwasaki, M; Kamigaito, O; Kanda, S; Kawamura, N; Matsuda, Y; Mibe, T; Nishimura, S; Saito, N; Sakamoto, N; Seo, S; Shimomura, K; et al. (Progress of Theoretical & Experimental Physics: PTEP, 2021)