  As a novel non-destructive bunch length diagnostic of the electron beam, an
experimental observation of the coherent Cherenkov radiation generated from a
dielectric caesium iodide crystal with large spectral dispersion was proposed
for the 30MeV femtosecond linear accelerator at Shanghai Institute of Applied
Physics (SINAP). In this paper, the theoretical design, the experimental setup,
the terahertz optics, the first angular distribution observations of the
coherent Cherenkov radiation, and the future plans are presented.
