Direct visualization of relativistic Coulomb field in the near and far field ranges

Abstract Coherent emission coming from relativistic charged bunches is of great interest in a wide range user-oriented applications and high-resolution diagnostics. The complete characterization such therefore important view understanding its potential. Here we present temporally-resolved the radiation emitted by ultra-short electron using temporal diagnostic based on electro-optical sampling with few tens fs resolution. We have characterized, for first time to our knowledge, evolution (in THz range) both amplitude direction propagation varying detection (i.e. observer) position near far field (FF) range. Results show that near-field regime propagates collinearly beam; while, approaching FF regime, behaves as classical Cherenkov radiation.