Design Of BPM System For FEL Facility At NSRL And Research On THz-driven Streak Camera

Beam diagnostics,which includes the measurements of beam intensity,transverse position,transverse size,longitudinal length,energy and so on,is essential for reli-able commissioning and stable operation of accelerator machines.In recent years,there has been an increasing interest on the free electron lasers(FELs),diffraction limited synchrotron radiations(DLSRs)and compact accelerator concepts like ter-ahertz driven acceleration.With the rapid development of accelerator techniques,there are corresponding challenges on the beam instrumentation.This dissertation mainly focuses on beam position monitor(BPM)and bunch length measurement:(i)the beam position monitor system for a tunable infrared free electron laser(IR-FEL)machine at national synchrotron radiation laborat,ory(NSRL);(ii)terahertz(THz)driven deflector based streak camera for femtosecond electron beam diagnostics.Beam position monitor system for an IR-FEL project at NSRLA compact IR-FEL user facility was constructed at NSRL,which can generate FEL radiation covering far-infrared range from 40 ?m to 200 ?m and mid-infrared range from 2.5 ?m to 50 ?m.The design of a reliable,precise and cost eficient BPM system for this machine is necessary,the requirement of this system is to provide a macro pulse position resolution better than 50 ?m.To meet this criteria,10 button BPMs were chosen as the main diagnostics device considering the performance and low cost of the button BPM;additionally,a resonant stripline BPM is also planned with the main purpose of studying on this newer type of BPM,considering its capability to provide a better resolution and the compatibility with the electronics for button BPM.The design,simulation and tests of these two BPMs,as well as the evaluation of position resolution are presented in detail.THz driven deflector based streak cameraStreak cameras are commonly used to measure duration and temporal structure of subpicosecond pulses.The resolution of a streak camera system strongly depends on the slew rate of the deflecting element,which approximately equals to the product of the amplitude and operation frequency of the device.As a combination of high frequency and high gradient,a THz-driven deflector based streak camera system has been proposed as an attractive tool to reach femtosecond scale or even better resolution.This dissertation contributes to this growing area of research by investigating promising designs of broadband THz deflectors with central frequencies at 0.3 THz.The basic properties of each structure are presented.Then one structure was used for a THz streaking experiment with 35 MeV electron beam,the experimental results are shown and the sources of imperfections are discussed.As a portion of the error might be attributed to the influence of higher order modes,a systematical method to analyze multipole fields of structures and the derived results are presented.In the end,several optimized designs of each structure based on this method are presented.