Development of s-band accelerating structure

In Pohang Accelerator Laboratory (PAL) in Korea construction of XFEL (X-ray Free electron Lazar) institution is under construction aiming at the completion in 2014 [1]. Energy 10GeV of the linac part of this institution and main frequency are planned in S-band (2856 MHz), and about 178 S-band 3m accelerating structures are due to be used for this linac. The oscillation of an X-ray laser requires very low emittance electron beam. On the other hand, since the accelerating structure which accelerates an electron beam has a feed port of microwave (iris), the electromagnetic field asymmetry of the microwave feeding device called coupler worsens the emittance of an electron beam. MHI manufactured two kinds of S-band accelerating structures with which the electromagnetic field asymmetry of coupler cavity was compensated for PALXFEL linac. We report these accelerating structures.