Linear focal cherenkov-ring camera for single shot observation of longitudinal phase space distribution for non-relativistic electron beam

Test accelerator as a coherent Terahertz (THz) source (t-ACTS) has been constructed at Tohoku University, in which generation of intense coherent THz radiation from sub-picosecond electron bunches will be demonstrated. Since final electron bunch length of accelerated beam is mostly dictated by the longitudinal phase space distribution at the exit of electron-gun. Measurement of initial electron distribution in the longitudinal phase space is indispensable for stable production of very short electron bunches. A novel method for measurement of electron kinetic energy applying a velocity dependence of the opening angle of Cherenkov light from a radiator medium has been proposed for relatively lower energy electrons. Combined use of a streak camera and a "turtle- back" mirror designed specifically that confines the Cherenkov light onto a linear focal line may allow us to observe the longitudinal phase space distribution directly. In this report, we describe the concept and designing of the linear focal Cherenkov-ring (LFC) camera system, as well as the current status of the system development.