14th Collaboration Workshop on Longitudinal Diagnostics

Laser-free and low-jitter Electro-Optic Sampling of FEL-based THz radiation by intrinsic ultrafast laserlike-pulses at FLASH

Not scheduled

20m

Building 3, hallway, ground floor (DESY Campus, Hamburg)

Poster Poster Presentations

Speaker

Seung-gi Gang (FS-FLASH-B (FLASH Photon Beamlines and Optics))

Description

The FLASH1 THz beamline at DESY produces intense multicycle THz undulator radiation along with quasi-single-cycle edge radiation. Precise characterization of such FEL-based THz pulses is hindered by the inherent timing jitter between the THz pulse and external lasers synchronized to the FEL master clock. While Electro-Optic Sampling (EOS) is a powerful diagnostic technique, this timing jitter fundamentally limits temporal resolution and spectral bandwidth, motivating the development of alternative approaches.

Afterburner EOS (ABEOS) is a laser-free and low-jitter method that uses broadband, laserlike probe pulses delivered with the THz pulse from the same electron bunch. ABEOS measurements show excellent consistency with simulations for both multi-pulse (10-pulse sequence) and single-pulse probe configurations. Comparisons with conventional methods—scanning EOS with an external laser, single-shot EOS (SSEOS), and FTIR spectroscopy—demonstrate reliable performance and validate the method up to 2 THz, with prospects for higher-frequency applications.

ABEOS thus provides a laser-free and low-jitter approach for precise FEL THz waveform characterization.