Research On LTVS Optimal Design Of Laser Transmission System And Trigger Characteristics

Laser Triggered Vacuum Switch(LTVS),as a kind of pulse power switch device,hasns-level trigger time-delay,higher trigger accuracy,faster insulation recovery speed,and higher stability performance.Compared with other types of pulse switches,LTVS shows its extremely attractive development and application prospects due to its excellent working performance.Experimental research on factors that affect the optimal design and trigger characteristics of LTVS laser transmission system will help improve the performance of LTVS and accelerate the practical process of LTVS.Firstly,the theoretical basis of LTVS trigger mechanism is analyzed and introduced,which is divided into two parts: trigger source and trigger mechanism.The trigger source of the switch is laser,which is mainly produced under the action of three factors such as working substance,excitation source and optical resonant cavity,and has good directionality and high brightness.In the trigger mechanism section,three mechanisms are mainly analyzed and introduced: 1)laser-target interaction effect,2)photoelectric effect,3)thermionic emission effect.The process of reflection,absorption,melting,gasification,and initial plasma generation of the target target under the action of laser and its heat conduction model are discussed.And briefly discusses the process of the initial plasma generated by the target in the photoelectric effect and thermionic emission effect.Secondly,the design of LTVS trigger characteristic experiment is divided into basic structure of LTVS,atmospheric laser transmission system component simulation design and the construction of experimental platform.In this experiment,a detachable vacuum chamber was selected as LTVS,and the electrode spacing was adjustable in the range of 0 ~ 20 mm.And through Gaussian beam laser simulation software to determine the components used in the switch laser transmission path.At the same time,based on the experimental conditions and simulation results,design and build a reasonable atmospheric laser transmission system and LTVS experimental circuit.Then,based on the atmospheric laser transmission system LTVS,a trigger characteristic experiment was carried out to change the laser power density,laser focal area,electric field intensity,clearance distance and other parameters.And combined with the initial plasma generation and development process in LTVS under different polarities,the trigger characteristics of LTVS are analyzed.According to the experiment: The trigger characteristics of LTVS with positive polarity are obviously better than that with negative polarity.Thetrigger time-delay of LTVS decreases with increase of laser power density,laser focal area and electric field intensity in the gap,and increases with increase of electrode spacing.As laser power density increases,the trigger time-delay of LTVS gradually decreases and tends to be stable.In the case of different working polarities,the difference in trigger time-delay of LTVS decreases significantly with the laser power density increases,especially when laser power density is 14.98 × 107 W / cm2,the difference is only 6.21 ns.Finally,the laser transmission system in LTVS is optimized,the atmospheric laser transmission system and the optical fiber transmission system are compared,and advantages of the latter are given.The principles,techniques and problems to be avoided in laser-fiber coupling,fiber selection and laser output shaping are discussed in the design of fiber transmission system.On this basis,the optical fiber transmission system LTVS was successfully built,and experiments proved that the LTVS can work normally,and under the laser energy is 6m J,its trigger time-delay at the minimum operating voltage of 200 V is 250 ns.