Development of 1.3 GHz superconducting cavity for ERL main linacs

Umemori, Kensei*; Sakai, Hiroshi*; Sakanaka, Shogo*; Sawamura, Masaru; Shinoe, Kenji*; Suwada, Tsuyoshi*; Takahashi, Takeshi*; Furuya, Takaaki*

We have been developing a 1.3-GHz superconducting cavity which is one of the essential components for energy-recovery linacs (ERLs). The ERL requires the accelerating gradient of 15-20 MV/m and CW beam operation of 100 mA. Damping of higher order modes is important for high current beam accelerators such as ERLs. We designed a new cavity of large iris diameter, ellipsoidal shape of equator and large beam pipe diameter to reduce the impedance of dipole modes. We also proposed eccentric-fluted beam pipe to damp quadrupole modes. The model cavities were manufactured and surface-treated. We report results of vertical measurement.