Research On The High Voltage Pulse Power Supplies Of THz-FEL Linac

Electron linear accelerator(Linac),the key device in free electron laser,is widely applied to industry,agriculture,medical treatment,national defense and other fields.High voltage pulse power supply is an important component of Linac.Significantly,its accuracy and stability can affect the quality of the output beam of Linac.The related theories and experiments of electron gun pulse power supply and klystron linear pulse modulator of Linac are studied,and improvement schemes are raised to meliorate the performance of high voltage pulse power supply.The working process of the series resonant charging of the high voltage pulse power supply in discontinuous current model(DCM)is analyzed and derived.And consequently,the characteristics and change laws of equivalent charging voltage,charging current,resonant current and resonant capacitor voltage are obtained.The equivalent circuit of charging power converter is established,and its power transfer function is derived.The characteristics of charging power supply of high voltage pulse power supply are analyzed under different modulation modes.And the circuits of electron gun pulse power supply and linear pulse modulator charging power supply are simulated and analyzed.The voltage fluctuation of electron gun pulse power supply and the stability of linear pulse modulator are measured.Based on the theoretical analysis and measured results,improvement measures for the electron gun pulse power supply and the power pulse modulator are proposed respectively.For the electron gun pulse power supply,the stability of its control system is analyzed with automatic control theory,and a feedback control compensation network is designed to calibrate its feedback control system.The analysis of amplitude-frequency characteristics demonstrates a better stability of the power supply after calibration.For the linear pulse modulator,the topological structure of its charging power supply is analyzed.Then improvement measures are raised to reduce voltage over charge by connecting anti-parallel diode to resonant capacitor and to realize soft switching by using detecting current zero-crossing point to control the frequency conversion of the inverter switch tube.The feasibility of the improvement measures is verified by simulation analysis.