Research On Improvement Of Linear Pulse Modulator And Control System For THz-FEL LINAC

Linear pulse modulator and control system are two important components of the THz-FEL linear accelerator(LINAC).The former affects the quality of the electron bunch,and the latter affects the accelerator’s operation and efficiency.Based on the preliminary completion of the linear pulse modulator and the control system,the existing problems are analyzed and corresponding improvement measures are raised.The theory and the discharge process of the chain pulse forming network(PFN)are analyzed,and the relation between the high voltage pulse jitter of the modulator and the instability of the electron bunch is inferred and calculated.The circuit simulation model of linear pulse modulator for the THz-FEL is set up,and the influence of each inductance of PFN on the pulse waveform is simulated and analyzed.Further,the requirements of the high voltage pulse jitter are calculated,and an improvement scheme for pulse modulator is proposed,and the high voltage pulses jitter before and after improvements are measured and analyzed.For the existing problems of the THz-FEL LINAC control system,a scheme of using the LabVIEW to unify the programming environment and using the interface of EPICS and LabVIEW called CALab to achieve the data communication based on the Client/Server structure is proposed.The program for the electron gun modulator control system is developed by LabVIEW,and the program has functions of remote control,data acquisition and display,status alarm and so on.Then the host computer communication system is set up by the CALab,and the data communication problem between multiple LabVIEW programs in distributed control system are perfectly solve.On the basis of host computer communication system,the closed-loop control of microwave power is achieved.Further,the data recording program is developed,which provides a key reading,saving and printing functions for the huge operating parameters of THz-FEL.Moreover,the host computer communication system is established,which provides a technical basis for further improvement of the control system.