Research On Conduction Characteristics Of A Laser Triggered Vacuum Switch

As an important fast closing device in pulse power system, triggered vacuum switch have attracted a wide spread attention with the development of pulse power technology. Due to the traditional electric triggered vacuum switch's poor time delay characteristic and short service life, its applications is restricted. High power laser triggered vacuum switch, due to its accuracy, reliability and anti-electromagnetic interference, has a very attractive application prospects in fast closing switch, electromagnetic emissions, series compensation capacitor protection and other fields.In this paper, a flat electrode type Laser Triggered Vacuum Switch is presented. In order to improve its service life, the selection of trigger material and the choice of trigger material's location are studied theoretically. The designed trigger electrode can be effectively ablative. KCl and Ti, NaCl and Ti, TiH2 is used as target material, which can provide extensive initial plasma for the switch. The trigger performance of switch is improved, and the shortest delay is up to 650ns. Then, the experiment platform of LC oscillation circuits is set up. The relationship among laser parameters, focus lens positions, applied voltages and the trigger characteristics (initial plasma generation, trigger threshold, minimum operating voltage* trigger success rate) and the delay time are analyzed in detail. Trigger threshold theory and arc ignition mechanism are proposed to explain the switch conduction, which can provide the theory basis of the design of the LTVS. It is concluded that:1) Trigger threshold of LTVS exists in certain structure and under-voltage ratio. The trigger threshold value increases with the increase of voltage decreases; when the voltage exceeds 300 V, the trigger threshold of the switch reaches stable, the stable value is 4.5×107 w/cm2.2) Under normal focused work way, with the increase of energy, the lowest work voltage almost stays the same, and the voltage value is lower than that of other ways, the minimum operating voltage value is low to 30 V. In addition, compared to the work voltage and the focus position, the effect of laser energy to trigger success rate of LTVS is more obvious.3) A short transition phase of strongly fluctuating exists. When the arc current value is beyond 5A, the oscillation phenomenon disappears and the vacuum arc is ignited stably.4) If other conditions are agreed, time delay of LTVS increases with the work voltage, and decreases as the energy of laser increases. Furthermore, time delay of LTVS is reduced with decreasing gap distance, and reducing the gap distance can improve stability of LTVS. Compared to negative polarity, positive polarity configuration can shorten time delay of LTVS.