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 (THz CSR). 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.
@article{arxiv.1607.08072,
title = {Direct observation of spatio-temporal dynamics of short electron bunches in storage rings},
author = {C. Evain and E. Roussel and M. Le Parquier and C. Szwaj and M. -A. Tordeux and L. Manceron and J. -B. Brubach and P. Roy and S. Bielawski},
journal= {arXiv preprint arXiv:1607.08072},
year = {2017}
}