Angular distribution of coherent Cherenkov radiation from a bunch passing through a vacuum channel in the dielectric target

Coherent Cherenkov radiation (ChR) generated by an electron bunch passing through a vacuum channel in the dielectric target has been considered. Simulation of ChR characteristics has been carried out basing on polarization current method. Spectral-angular distributions of coherent ChR generated by the short electron bunches are presented for a flat target with a slit and a conical target with a vacuum channel. We demonstrate feasibility of using cesium iodide conical target for bunch length diagnostics. Bunch length of about 100 fs (rms) could be determined measuring the angular distribution of coherent ChR due to material frequency dispersion.