DEMAZEUX Quentin : Ultrafast measurement in accelerator based-sources

Résumé de thèse :

The main purpose of this thesis is to realize systems that are able to record in single shot the shapes of pico or femtosecond relativistic electron bunch shapes, as well as the terahertz light that is emitted by accelerator-based sources.

To do so, we will use single-shot electro-optic (EO) detection, where a THz electric field is encoded into the spectrum of a chirped probe laser pulse inside a Pockels crystal.

The project is the fruit of a collaboration between DESY (German national research center on accelerators science) and the PhLAM CNRS laboratory at Lille University which give us the opportunity to develop and test new measurements strategies at accelerator facilities (FLASH and EuXFEL).

Recently single shot measurements of THz electric field with simultaneously high temporal and spectral resolution at high repetition rate (1-2 MHz) become possible [1][2].

However the sensitivity of EO detection at this high repetition rate, as well as higher order effect remains a strong limitation that may cause distortions of the THz field reconstruction [3].

A new reconstruction algorithm has been developed to eliminate distortions caused by higher-order effects, and preliminary results of electron bunch measurements at EuXFEL will be presented.


[1] Roussel, E. et al. Phase Diversity Electro-optic Sampling: A new approach to single-shot terahertz waveform recording. Light Sci Appl 11, 14 (2022).

[2] B. Steffen et al. Compact single-shot electro-optic detection system for THz pulses with femtosecond time resolution at MHz repetition rates. Review of Scientific Instruments , 91(4) :045123, April 2020.
[3] Xiao-Yu Peng et al. Distortion analysis of pulsed terahertz signal measured with spectral-encoding technique. Journal of Applied Physics , 108(9) :093112, November 2010.


Doctorant : DEMAZEUX Quentin

Directeur de thèse : BIELAWSKI Serge, SZWAJ Christophe