121st General Meeting of the KCS

Type Poster Presentation
Area Physical Chemistry
Room No. Event Hall
Time 4월 20일 (금요일) 11:00~12:30
Code PHYS.P-144
Subject Development of Ultrafast Electron Diffraction (UED) apparatus in IBS
Authors Jun Heo, Hyotcherl Ihee1,*, Doo-Sik Ahn2
Department of chemistry, Korea Advanced Institute of Science and Technology, Korea
1Department of Chemistry, Korea Advanced Institute of Science and Technology, Korea
2Institute for Basic Science, Korea
Abstract Visualization of chemical reactions is one of the ultimate goals in chemical dynamics of isolated molecules, liquids and materials.[1-3] Ultrafast Electron Diffraction (UED), a member of 4D electron imaging apparatus, is a toolkit to film the snapshot of transient structures during the bond dissociation or formation. Recently we have introduced RF compressing technique to bunching the electron beam which is a promising tool to get the tens of femtosecond electron pulse duration in the laboratory-scale machines. UED apparatus in IBS is designed for sub-Å (spatial) and sub-200 femtosecond (time) resolution in single shot. UED apparatus in IBS mainly consists of three parts: 1) electron gun driven by Ti:Sapphire femtosecond laser system, 2) RF-based electron beam compressor and 3) scattering chamber coupled to detector assembly to measure the diffraction pattern as a function of delay time. 80 keV accelerated electron beam generated by tripled output of Ti:Sapphire femtosecond laser output (800 nm, 1 kHz, 35 fsec) fly to the RF-compressor to re-compress the lengthened electron pulse duration flying. The diffraction patterns for transient structures are obtained by pump(laser)-probe(electron) scheme. Time synchronization between RF-compressor and electron beam is achieved by Phase-Locked Loop (PLL) device. For the characterization of generated electron bunches. Measuring the time-duration of electron bunch also have been one of the most important steps in the UED experiment. Our group newly introduce the streak camera system. Bunch duration is measured by this streak camera system which contains two streak plates for charging high voltage.[4] The electric potential on both plates are rapidly discharged by pump beam irradiation on GaAs photo-switch. This fast discharging induces the oscillatory damped electric field, which forces electron bunches to be streaked. For trajectory simulation of electrons and checking the validity of streak camera system, GPT (General Particle Tracer) program was used to optimize the experimental conditions. In this presentation, we will present the current status of development, especially about streak camera system.
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