Design and Construction of Carbon NanoTubes (CNTs) Triggered Pseudospark Switch
Type of Degreedissertation
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Pseudospark switches have been used as fast closing switches in pulsed power systems. Advantages include high hold off voltage of 10s kV, high conduction current of ~104 A, fast current rise time of 1011 A/s, low delay and jitter time approaching ns, and long lifetime. In general, pseudospark switches have hollow anode and hollow cathode geometry and can be triggered by several methods that increase the charge carrier density in the hollow cathode region. The efficiency of these charge carrier accumulation determines the performance of switch operation. In the electron injection triggering where electrons emitted from cold cathode emitter, are accelerated in the electric field and initiate the switch closing. Therefore, cold cathode material is critical to this trigger method. Carbon nanotubes (CNTs) are known for their excellent field emission characteristics. This property makes them a good candidate for the cold cathode material in this application. In this research work, pseudospark switch triggered by carbon nanotubes coated electrode is designed and constructed. The trigger electrode is fabricated by coating CNTs, either randomly aligned CNTs, vertically aligned CNTs or trench wall patterned CNTS on silicon in chemical vapor deposition method (CVD). The CNTs are synthesized under different growth conditions with varying sputtering time, oxidation time, and growth time. The patterned CNTs are fabricated using monolithic IC fabrication processes. The trigger electrode is then assembled and tested in a pseudospark switch constructed in-house with a quartz vacuum tube, a hollow cathode and a planar anode. The switch test experiments are carried out in different background pressures, different trigger voltages, and trigger electrodes with different types of CNTs. Delay and jitter time of the pseudospark switch under different working conditions are studied. Hold off voltage, conduction current and current rise time are presented, and optimizations of the switch operating characteristics are discussed.