Recording THz pulses and electron bunch shapes using electro-optic detection: recent advances in time resolution and repetition rate; Control of the longitudinal bunch dynamics during the microbunching instability to produce stable coherent THz radiation

Although widely used for monitoring electron bunch shapes and THz pulses, single-shot electro-optic detection techniques have been suffering from several limitations, in particular for achieving simultaneously high repetition rate and high temporal resolution. We present recent two recent advances in the field, and that are compatible with each other: photonic time-stretch for achieving multi-MHz acquisition rates, and the recently introduced Diversity Electro-Optic Sampling (DEOS) method for achieving high temporal resolution. Test at several facilities - including SOLEIL, KARA, DESY, FERMI and ELBE - will be presented.

The microbunching instability is an omnipresent behavior appearing systematically when bunches with high charge are considered. This instability is characterized by the spontaneous appearance of micro-structures in the longitudinal profile of the bunch, leading to an emission of strong coherent radiation (usually in the THz range).

However, these instability usually comes with a bursting behavior, making this source not directly usable. In this presentation, we will present a scheme based on a feedback loop - and inspired by methods of control of chaos - allowing to suppress the bursting behavior, while keeping the micro-structures in the bunch.

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