| Nowadays, pulsed power technology has been used increasingly in civilian and military fields.However, its further development is restricted for the reason that the traditional high-voltage and strong-current pulsed switch, as the key component, has a difficulty in striking a balance in all performance parameters due to the influence of media types and trigger modes. Combining the traditional technologies about pulse switch, Laser-Triggered Vacuum Switch(LTVS) can probably be a kind of high-voltage and strong-current pulsed switch with better performance. It has the advantages of high flux capacity, achieving repetition frequency trigger easily, low delay-time and jitter and large range of operating voltage. But there have been few studies about mechanisms of trigger and conduction of LTVS at home and abroad.With LTVSs designed by a group of the cooperation unit, experimental studies on different laser-pulse parameters, main gap voltage, position irradiated by laser and LTVS structure's influences on conduction parameters are achieved. Besides, studies on trigger life of target electrode, effect of energy on loss of target electrode, and arc spectrum are achieved.From these studies above, theories about mechanism of plasma generation from laser pulse and target matter interaction and LTVS conduction mechanism are analyzed. These help to optimize the lase-pulse parameters,and the material and structure of the target electrode. By using COMSOL simulation software and experimental data, the effects of target electrode surfaced electric field and switch structure are analyzed. The results prove that the increasing electric field intensity near target electrode can optimize conduction parameters effectively,and the conduction parameters of multi-electrode type LTVS are better than ones of plane type LTVS obviously. These are helpful to provide methods and bases for optimizing the performance of LTVS further.The mechanism of plasma and small neutral particles generation from laser pulse and matter interaction, namely LTVS trigger mechanism, is introduced and analyzed, including evaporation ablation, explosion ablation, photoemission, thermionic emission, multiphoton ionization, inverse bremsstrahlung ionization. The mechanism of choosing KCl and Ti as the target materials is analyzed. Experimental studies about the effects of ns-pulse laser of different energies, waveforms, pulse widths, polarization and focusing characteristics onconduction parameters of LTVS at different main gap voltages. Preliminary results are obtained:(1) With the energy of single pulse increasing, the optimization of conduction parameters will show a tendency toward saturation;(2) Only with small laser energy,enlarging the main gap voltage can optimize conduction parameters, and the research on arc spectrum shows that spectral intensity and arc plasma species are influenced by main gap voltage;(3) The experiments about the focal spot and defocus amount shows that the optimization of conduction parameters approaches a limit with energy density increasing.(4)The difference of 1064 nm and 532 nm wavelength hasn't effect on conduction parameters, as thermal effect mechanism dominates the lasers-matter interaction. And different polarization of ns-pulse laser has little effect on parameters of initial plasma and hasn't effect on conduction parameters;(5) Doublet pulse can produce more initial plasma, but singlet pulse can produce more vapor cloud and small particles. Singlet pulse leads to better conduction parameters.(6) The life of target electrode is studied by using laser pulses of different energies to trigger LTVS repeatedly. The results prove that the performance of target electrode goes bad obviously after 18000 times irradiation, and loss ratio of KCl/Ti increases with energy increasing, which leads to faster deterioration of target electrode performance. |
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