Study On Free Dielectric Recovery Characteristics Of Laser Triggered Vacuum Switch

With the gradual expansion of pulse power applied range,the pulse waveform and repetition rate of pulse power generator are required to be higher.The closed switch is a key component in the pulsed power system,which has a nearly decisive influence on the repetition frequency,energy conversion,pulse steepness,peak value and pulse width.As a new closed switch in the field of pulse power,Laser triggered vacuum switch(LTVS),has many advantages,such as short delay time,small jitter,high triggering precision,strong current carrying capacity,long service life and so on.All these advantages determine LTVS has a very broad development prospect.Different from traditional vacuum switch,the interruption capacity of the LTVS is affected by the arc ablation electrode and the target.In order to further study the influence of different factors on the interruption capacity of LTVS at high frequency and improve its repetition rate,the inherent dielectric recovery strength of LTVS is measured,that is,the dielectric recovery process without recovery voltage.Firstly,the electromagnetic field simulation software Ansoft Maxwell is used to analyze the influence of target structure and position on the electric field;Then the three-dimensional model of cup-shaped axial magnetic contact is established,and the transient magnetic field solver is used to simulate and analyze the distribution of gap magnetic field at the time of current peak and current zero crossing under different current peak,frequency and electrode spacing;Combined with the previous electromagnetic field simulation results,the influence of electromagnetic field on the dielectric recovery characteristics of LTVS is discussed and analyzed;Secondly,the pulse high voltage source is designed and the pulse high voltage source circuit is studied to determine the component parameters of the pulse high voltage source and obtain the ideal pulse high voltage;The simulation software SIMULINK is used to calculate and solve the high frequency current source circuit and determine the parameters of each component in the experimental circuit.The laser trigger systems used in the main circuit and pulse high voltage circuit are designed respectively.Combined with the measurement and analysis results of the time delay and jitter that may occur in the circuit,the time interval of the output trigger signal is determined,and the design of the experimental control system is completed.Based on the detachable vacuum chamber,the test platform of LTVS dielectric recovery characteristics is built.By changing the current amplitude,frequency and electrode spacing,the curves of LTVS dielectric strength with time under different factors are compared,and the influence of various factors on LTVS dielectric recovery strength is discussed.Experimental results show that the dielectric recovery strength of LTVS decreases with the increase of current amplitude and electrode spacing.With the change of frequency,the dielectric recovery strength at higher frequency is lower than that at lower frequency in the initial period of time,but then the dielectric strength recovers rapidly.All the above studies provide references for improving the repetitive interruption performances of LTVS.