Research On Triggered Characteristics Of LTVS With Different Mixed Target Materials

Laser Triggered Vacuum Switch?LTVS?uses vacuum with strong insulation and fast dielectric recovery as the insulating medium.The short pulse laser is used as trigger source to realize electrical isolation between trigger circuit and main circuit,so false trigger probability is reduced.LTVS has a short trigger delay,high operational stability,and long-range triggering.This paper mainly studies triggering process of LTVS.Previous studies have shown that triggering performance of LTVS is affected by interaction between pulsed laser and target materials.In order to improve working performance of LTVS,this paper chooses different powder mixture metal?Mn,Ti,W?and metal salt?KCl,NaCl,K₂CO₃,Na₂CO₃?are adopted to be the targets of LTVS.The metal material has a good laser absorption rate,and the metal salt material has good chemical activity.Firstly,theoretical analysis of triggering process of LTVS is carried out,and interaction process between laser and target material is discussed,including laser ablation,radiation and heat conduction process of energy in the target material.The MHD model was established,and the initial plasma was simulated by COMSOL software.It was found that density of initial plasma was the highest at the most central position of laser radiation.The heat transfer process of surface of laser radiation target material was simulated and analyzed.The absorption capacity of laser of different metal materials was studied.It was found that the temperature of Mn material with higher resistivity was higher,and the heat transfer rate of Cu material with higher thermal conductivity was faster.The smaller pulse width of laser,the smaller spot radius,and the higher energy,the higher temperature of surface of target.The electrostatic field of LTVS is simulated under different groove depths.It is found that electric field strength decreases as the groove depth increases,which provides guidance for selecting appropriate placement position of target material.Secondly,an experimental test system was built to study triggering performance of LTVS when laser wavelength was 1064 nm.The experimental results show that with appropriate target material,the trigger delay of LTVS can be reduced and voltage drop rate can be increased.Compared with other target materials,the triggering performance of Mn and K₂CO₃ mixed targets is better.In addition,as laser energy increases,electrode spacing decreases,and groove depth decreases,both trigger delay and jitter delay decrease,increasing operating voltage and metal content of mixed target,and reducing vacuum degree can reduce trigger delay,but it has little effect on jitter delay.In positive polarity,trigger delay of LTVS is small,the voltage drop rate is large,and stability is good.The lower degree of vacuum,shallower groove,higher operating voltage and greater laser energy,the greater rate of voltage drop.Finally,the ablation of target material was studied.The results show that target material will leave ablation pit on surface after ablation,and the ablation degree will decrease as groove depth increases.After laser and arc ablation,trigger delay of LTVS increases,voltage drop rate decreases,and operational stability of switch decreases,affecting the service life of LTVS.