Precursor wave induced by a bunch in an inter-digital structure

Forerunning wave and wakefield induced by a non-relativistic, charged Gaussian bunch moving along a wide-bandwidth, periodic structure have been simulated in time domain. Unusual waveform of the potential function is compared to theoretical predictions and time-domain, multi-mode analytical solution. The numerical experiment demonstrated anomalously high magnitude of the precursor wave. A specific case, when the group velocity is equal to the bunch velocity, is discussed as well. Potential applications include diagnostics, sensors, and probing tools for metamaterials and photonic crystals.