Plasma stability in a triggered vacuum switch

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. A test circuit was set up with an inductance of 46.4 muH and a group of capacitances of 236.4 mF connected in series. The trigger pulse parameters were adjustable and trigger processes were stored by digital oscilloscope and high-speed camera. Experimental tests were made in three different kinds of trigger power according to the numerical degree. The different trigger power leads to different trigger plasma, i.e. sufficient trigger plasma, insufficient trigger 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 initial stage of trigger plasma. The development of trigger plasma is analyzed by theoretical analysis and experimental data. The results show that the initial constriction of the vacuum arc is unavoidable during the trigger process. Sufficient trigger plasma is a prerequisite for the stability of turning-on TVS, while insufficient trigger plasma leading to chopping both in trigger current and voltage when triggering TVS. Sufficient trigger plasma can also promote the trigger lifetime and accuracy, with trigger delay limited in hundreds of nanoseconds.