Measurements of coherent diffraction radiation from a slit of a variable width generated by short electron bunches were performed in millimeter and submillimeter range. Experimental data are compared with transition radiation case and theoretical predictions. More realistic description, than the conventional theory does, is necessary to correctly account for the data. No noticeable difference in the bunch length value was observed between the diffraction radiation mode in a wide range of the slit widths and transition radiation one in the bunch length evaluation.
M et al. (Mon,) studied this question.