Study on 2 cell rf-deflector cavity for ultra-short electron bunch measurement

We have been studying on a system to measure ultra-short electron beam bunch length at Waseda University. We adopted the rf-deflector system which can convert the longitudinal distribution to transverse by sweeping the electron bunch. By using HFSS, we optimized the design of the 2-cells rf-deflector which is operating on π-mode, standing wave, dipole (TM₁₂₀) mode at 2856 MHz. This rf-deflector was designed to have enough performance for measuring the 200 femto second bunch. Adjusting the cavity parameters, which was calculated in HFSS, we have finished manufacturing under the collaboration with High Energy Accelerator Research Organization (KEK). We will integrate the rf-deflector into an S-band Cs-Te photocathode rf electron gun system in Waseda University, and carry out bunch length measurement. In this paper, the design of rf-deflector, the estimation for rf-deflector performance, and the future plan will be described. (author)