Super Fast Diagnosis Of Time Focusing And Amplification Technology Research

The ultrafast dignosis technique is the core detecting method in some areassuch as ICF (Inertial Confinement Fusion), Z-pinch, synchron radicalization,photobiology, photochemistry, X-ray laser physics、plasma physics, atomicphysics, etc．Especially the ultrafast electron diffraction, the temporal resolutionup to femtosecond and the spatial resolution up to picometre make the dream of“molecular movie and atomic movie” to be true some day. Restricted by theinitial energy dispersion and the sweeping speed (now can be up to2.8c) on thedeflection plates and others, the temporal resolution based on the streak cameracan not break through100fs yet while the lasers have been in the era of asmagnitude or even faster.With the rapid development of modern science and technology, newgeneration of streak tubes with femtosecond time resolution has beenintensively studied for further application. In this paper, time amplifyingtechnique is adopted to improve the temporal resolution of the newly-designedstreak camera to a great extent. This method uses a time-dependent decelerationfield to lengthen the photoelectron bunch, which can improve the timeresolution and reduce the time dispersion caused by initial energy spread. At last,Tracing and simulating large numbers of photoelectrons through Monte-Carlomethod and finite difference methods，the temporal resolution can improve10times better (up to66fs), which lays a foundation to develop the streak camerasto explore more ultrafast phenomena.The realization of the compression of electron pulses in temporal domain isa core technique to improve the temporal resolution of ultrafast electrondiffraction systems。 In this paper, the time focusing technique is adopted topotentially improve the temporal resolution of the ultrafast electron diffractionsystems. This method uses a time-dependent acceleration field to greatly compensate the time dispersion between photocathode and anode, that is theelectrons arriving earlier see relative lower accelerating field than the electronsarriving later by appropriately choosing field ramping slope so that thedispersion of the electron bunch will be decrease to a great extent. Eventually,the physical temporal resolution can be improved as much as possible. Tracingand simulating large numbers of photoelectrons through Monte-Carlo methodand finite difference methods，the electron pulses with300fs can be compressedto50fs, which lays a foundation to develop the ultrafast electron diffractionsystems with better than100fs temporal resolution.