Development of a 1.3GHz 9-cell superconducting cavity for the energy recovery linac

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

For the energy recovery linacs (ERLs), strong higherorder-mode (HOM) damping is necessary to achieve high current operations. For this purpose, we have newly designed a 1.3 GHz 9-cell superconducting cavity. The cell shape of this cavity is designed and optimized for the high current ERL operation. The HOMs are extracted through the beam pipes and damped with RF absorbers. Furthermore, an idea of eccentric-fluted beam pipe (EFB) is proposed in order to extract the quadrupole HOMs. In this paper, strategy for the HOM suppression to optimise for the ERL operation and estimated HOM characteristics are described. Other important R&D items are also reported.