Seminars Archive

Single shot diagnostic of electron bunch shapes at MHz+ repetition rates using diversity electro-optic scheme at EuXFEL, FLASH and FELBE

Abstract
Single-shot detection of THz waveforms at high repetition rates is a key requirement in a growing number of THzrelated applications, including time-domain spectroscopy, accelerator and Free-Electron Lasers diagnostics. Over the past decade, achieving MHz-range repetition rates has been demonstrated using chirped laser probe techniques, such as time-stretch and spectral decoding methods [1-3]. However, due to intrinsic physical limitations, these methods become increasingly unreliable when applied to broadband THz waveforms [4]. This presentation details a novel measurement methodology for THz waveform characterization, utilizing information diversity [5] to achieve robust single-shot detection. We demonstrate that simultaneous measurements provide the necessary information for precise THz signal retrieval. By combining spectral interferometry reconstruction algorithm with the recent Diversity Electro-Optical Sampling (DEOS) [5], our technique offers significant advantages, adapting to any probe laser imperfections, including high-order dispersion, and resolving the longstanding fundamental limitations of chirped pulse electro-optical detection [4], enabling high temporal resolution recording of short electron bunch shapes across extended temporal windows. A proof-of-principle experiment for the THz measurement method (together with it "self-adaptation" to the probe laser chirp), using a classical THz time-domain spectroscopy (TDS) experiment is presented. Two experimental implementations are presented, one at DESY, designed for sub-picosecond relativistic electron bunch at MHz+ repetition rates characterization, and another at FELBE, designed for THz narrowband pulse detection at 3.44 THz, including a Carrier Envelope Phase (CEP) diagnostic. This technique promises significant advancements in single-shot THz time-domain spectroscopy and accelerator physics.

[1] E. Roussel et al., "Observing microscopic structures of a relativistic object using a time-stretch strategy", Scientific Reports 5, 10330 (2015)
[2] N. Couture, M. Lippl, W. Cui, A.Gamouras, N.Y.Joly, andJ.-M.M´enard, "Performance analysis of tabletop single-pulse terahertz detection at rates up to 1.1 MHz" 21, 054020 (2024)
[3] B. Steffen et al., "Compact single-shot electro-optic detection system for THz pulses with femtosecond time resolution at MHz repetition rates", Rev. Sci. Instrum. 91, 045123 (2020)
[4] F. Sun, Z. Jiang, and X.-C. Zhang, " Analysis of terahertz pulse measurement with a chirped probe beam", Appl. Phys. Lett. 73, 2233 (1998).
[5] E. Roussel 1, C. Szwaj 1, C. Evain 1, B. Steffen, C. Gerth, B. Jalali and S. Bielawski, "Phase Diversity Electro-optic Sampling: A new approach to single-shot terahertz waveform recording", Light: Science & Applications 11, 14 (2022)