Field Radiated by an Electron Bunch Passing through a Linac Section

The field radiated by a single electron bunch crossing full an iris-loaded waveguide has been studied both theoretically and experimentally. Theories are based upon the normal mode expansion of the radiated field in the R.F. structure (T.W. or S.W. modes). They show the influence of the dispersion law on the radiated waveforms, in which a mixture of synchronous and cut-off modes mainly appears. Experimental works have been made on a low energy model in which the negligible electron velocity variation allows the results to be extended to ultra-relativistic linacs. Radiated fields observed on the TM01 mode quite satisfy the theoretical predicted results, and the method used can be generalized for studying the upper modes.