Seminars Archive

Ultrafast measurements of electric fields and optical pulses, and applications to electron bunch dynamics investigations.

Abstract
In order to investigate electron bunch dynamics - in particular the microbunching instability - we have developed single-shot Electro-Optic Sampling (EOS) diagnostics operating at multi-MHz repetition rates, and high sensitivity [1,2,3]. The principle consists to use the so-called photonic time stretch method [4] for ''slowing down'' the picosecond-scale electic signals to be analyzed, so that they can be recorded by an oscilloscope. This strategy has enabled to record successive CSR pulses emitted at SOLEIL, and the electron bunch near field at the ANKA storage ring. In order to record optical pulses shapes in single-shot, we are currently testing a slightly different strategy, which is based on ''temporal imaging'' concept [5]. We tested this system [6] (called time-microscope) on optical sources, and obtained performances that overcome streak-cameras, in particular concerning the trade-off between dynamical range and speed (40 dB for 250 fs resolution in our first tests). We will also show how the direct EOS measurements of CSR pulses allows to perform extremely stringent tests of the dynamical models of the electron bunch [1,3]. Numerical simulations are made using parallel Vlasov and macroparticle codes that are developed at PhLAM.

[1] E. Roussel et al.,Observing microscopic structures of a relativistic object using a time-stretch strategy, Scientific Reports 5 10330 (2015)
[2] C. Szwaj et al., High sensitivity photonic time-stretch electro-optic sampling of terahertz pulses, Review of scientific instruments 87, 103111 (2016)
[3] C. Evain, Direct Observation of Spatiotemporal Dynamics of Short Electron Bunches in Storage Rings, Phys. Rev. Lett. 118, 054801 (2017).
[4] F. Coppinger et al., Photonic time stretch and its application to analog-to-digital conversion. IEEE Trans. on Microwave Theory and Techniques 47, 1309 (1999)
[5] Kolner, B. H. & Nazarathy, M. Temporal imaging with a time lens. Opt. lett. 14, 630-632 (1989).
[6] P. Suret et al., single-shot observation of optical rogue waves in integrable turbulence using time microscopy, Nature Communications 7, 13136 (2016)