Plasma Stability in a Triggered Vacuum Switch

A triggered vacuum switch (TVS) has found fast growing applications in the fields of pulse power system. However, its popularization is still limited due to the trigger stability and accuracy. Research on the trigger process of TVS is one of valid ways to enhance the TVS performances. A sample of TVS was fabricated in this paper. An LC test circuit of two groups of parameters was set up. The trigger pulse parameters were adjustable, and trigger processes were stored by digital oscilloscope and high-speed camera, respectively. Experimental tests were made in three different kinds of trigger power according to the numerical degree. The different trigger power leads to different initial plasmas, i.e., sufficient initial plasma, insufficient initial plasma, and the transition stage between them. The trigger process and its stability are discussed based on the waveforms and photographs. Field emission causes the point discharge of trigger pin and leads to the primary stage of initial plasma. The development of initial plasma is analyzed by theoretical analysis and experimental data. The results show that sufficient initial plasma is a prerequisite for the stability of turning-on TVS, while insufficient initial plasma leads to chopping both in trigger current and voltage when triggering TVS. Sufficient initial plasma can also promote the trigger lifetime and accuracy, with a trigger delay limited in hundreds of nanoseconds.