Diagnostics of an electron beam of a linear accelerator using coherent transition radiation

The three-dimensional distribution and the divergence of electrons in a bunch have been determined for a short-bunch beam of an L-band linear accelerator by the observation of coherent transition radiation at millimeter and submillimeter wavelengths. The transverse size of the beam and its emittance are derived as 22±{}4 mm in diameter and (4.0±{}2.0)×{}10² mm mrad. The longitudinal distribution of electrons in the bunch is found to be a triangular shape with a bunch length (full width at half maximum) of 8.5±{}1.0 mm (28 ps). An advantage of this method in determining the longitudinal distribution function of electrons is discussed in comparison with the conventional method using a streak camera.