Study On Ultrafast Electron Diffraction System Performance Improvement

Ultrafast electron diffraction is an effective technique for measurement oftransient structure and ultrafast structural dynamics by use of ultra-short electronpulses and ultra-short laser pulses. It has characteristic of high spatial resolution andtemporal resolution. Ultrafast electron diffraction system has been an importanttechnique in studying the ultrafast phenomenon of physical, chemical and biologicalprocesses. Femtochemistry, femtobiology and femtophysics are developing rapidly byuse of it.In this thesis, the ultrafast electron gun is simulated and optimized. The electricfield and the magnetic flux of the focus region is calculated with boundary elementsmethod. The electron trajectory in the ultrafast electron gun is traced withRunge-Kutta method. The location of the best image plane has been found. Weanalyze the temporal, spatial and energy distribution of7000electrons when theyreach the prime plane. The size of the electron beam is0.029mm，the divergenceangle is0.029o,the energy distribution is9.8eV, temporal resolution of this system is270femtosecond and spatial resolution is60lp/mm.The components of ultrafast electron diffraction system are ultrafast electron gun,vacuum chamber, femtosecond laser light source, vacuum system, detection systemand control system. The functional mechanism of each part is introduced in detail. Anultrafast electron diffraction system with both ultrafast temporal resolution andultrahigh spatial resolution was established.Investigation and optimization on spatial resolution of the system wereperformed. The experimental results demonstrate that the system can provide anelectron beam diameter that less than300μm and a incident angle less than0.09o. X-Ydeflection plates and stability of the electron beam were quantitative analysis.Diffraction patterns of Al is obtained by this system and it demonstrates that thesystem can distinguish diffraction peak position changes of0.36%...