Research On The Self-coupling Pre-ionization Switch

The switch is one of the key technologies in the pulsed power field. In this thesis, atransverse capacity-coupling UV pre-ionization switch is proposed and some theoreticaland experimental work is carried out to investigate the basic principle and operationcharacteristic. This result shows that pre-ionization switch can effectively improve theoutput stabilization of switch. The detailed work includes the followings:Firstly, the breakdown features of different field distribution is analyzedtheoretically according to the gas discharge principle and the instability of breakdownvoltage is found to result from the randomness of statistical delay time. When thenumber of initial electrons reaches104or more, the total delay time will be equal to theformation time and the stability of breakdown voltage is improved. The relationshipbetween the breakdown voltage and the length of the protrusion in the plane electrodesis analyzed. As the protrusion becomes longer, the breakdown voltage will decrease,which is of significance for the design of structure of the UV pre-ionization switch andfor the estimation of breakdown voltage.Secondly, the factors which affect the intensity of UV pre-ionization isanalyzed,such as pre-ionization current peak、storage energy、gas press and spaceattenuation，and the feasibility of the pre-ionization from the capacitor of pF-order isanalyzed. Besides, the cause of initial electrons from UV pre-ionization in the metalsurface is discussed and the photoelectric effect is considered to be the main factor. Theincidence of initial electrons can alter the moment when electron avalanche istransformed into streamer to control the development speed of streamer and shorten thestatistic breakdown delay effectively, which can be presented by numerical calculationand simulation.Thirdly, Some experiments of the UV pre-ionization switch are carried out. Theresults indicate that in the main switch which is full of N2or SF6, the effect of UVpre-ionization is evident and the scatter of the breakdown voltage is reduced effectively.Contrasting with different window material, it is approved that pre-ionization relies onultraviolet radiation mainly from spark. The distance between pre-ionization gap andmain gap can influence the effect of pre-ionization. When the distance exceeds athreshold size, the UV-illumination on the surface will weaken because of spaceattenuation, and the number of initial electrons will be less than104to result in theinefficacy of pre-ionization.Fourthly, according to the results above, the transverse capacity-coupling UVpre-ionization switch is designed to satisfy the demands by adjusting the shape ofelectrodes and insulation skeleton. This design guarantees the stability of breakdown voltage without the complicated external circuit, which has advantages of simplestructure and volume compactification. The short length can effectively reducedshelf-inductance when gap switches into conduction.