Direct Observation of Spatiotemporal Dynamics of Short Electron Bunches in Storage Rings

Abstract

In recent synchrotron radiation facilities, the use of short (picosecond) electron bunches is a powerful method for producing giant pulses of terahertz coherent synchrotron radiation. Here we report on the first direct observation of these pulse shapes with a few picoseconds resolution, and of their dynamics over a long time. We thus confirm in a very direct way the theories predicting an interplay between two physical processes. Below a critical bunch charge, we observe a train of identical THz pulses (a broadband Terahertz comb) stemming from the shortness of the electron bunches. Above this threshold, a large part of the emission is dominated by drifting structures, which appear through spontaneous self-organization. These challenging single-shot THz recordings are made possible by using a recently developed photonic time stretch detector with a high sensitivity. The experiment has been realized at the SOLEIL storage ring.

Phase Diversity Electro-optic Sampling: A new approach to single-shot terahertz waveform recording

“…Future work will include a systematic experimental study of the new limits set by the method in terms of ultimate resolution, time-window, and repetition rate. In this respect, an important direction will consist in combining the present DEOS terahertz recording method with photonic time-stretch 19 , 42 , 49 , as this should theoretically allow repetition rate to reach the hundred of megahertz range.…”

Cross-Correlation of THz Pulses from the Electron Storage Ring BESSY II

“…Especially, the transition from stable CSR emission via quasi harmonic micro-bunching to the chaotic bursting is very different among the various storage ring facilities and call for sophisticated diagnostics. The electron bunch spatio-temporal dynamics have been studied by the experimentally obtained spectral content of THz pulses in comparison with numerical simulations [21][22][23]. A straightforward approach to study the emitted CSR pulses is not available due to the lack of suitable THz recording electronics, but the quasi-direct observation of sub-picosecond microstructures within an electron bunch became recently possible by a time-stretching scheme [24][25][26].…”

High throughput data streaming of individual longitudinal electron bunch profiles

“…As a result, microstructures can form spontaneously in the phase space [1]. Because these microstructures produce strong THz radiation bursts with an intensity more than 5 orders of magnitude higher than incoherent synchrotron radiation [2] potentially leading to e.g. applications in non-linear spectroscopy, this process is subject to intense investigations [3][4][5][6][7][8][9][10][11][12].…”