Generation of coherent THz radiation by electron bunch tilting

We have been developing an rf transverse deflecting cavity for ultra-short electron bunch diagnostics. Our rf deflector system has 150 fs temporal resolution for 5 MeV electron beam. The rf deflecting cavity not only can measure the bunch length by sweeping directly the electron bunch but also tilt the electron bunch. We considered to use this bunch tilting for generating the coherent Cherenkov radiation. At Waseda University, we tested this scheme with photocathode rf electron gun, rf deflecting cavity and triangular prism made by TOPAS polymer as a target. The resulting radiation has a property of broad bandwidth, high peak power and coherent THz radiation. In this conference, the principle of coherent Cherenkov radiation by electron bunch tilting, recent experimental results and future prospective will be reported. (author)