Theoretical And Experimental Studies On Pulsed Ablative Capillary Discharge Plasmas

Electrothermal plasmas are characterized by high number densities andrelatively low plasma temperatures. Electrothermal plasma devices are of greatimportance in electrothermal or electrothermal chemical launchers and many othertechnological applications. In this thesis , a novel two-gap capillary plasma generator (TGCPG) isdeveloped as a realistic alternative to the conventional capillary in electrothermallaunchers and expected to be a versatile capillary plasma generator for otherapplications. It is designed to accomplish two goals: repetitive operation and acompact power supply system in which capillary itself serves as a closing switch. Inaddition, a simple power conditioning system with which a two-pulse dischargecurrent curve can be generated for electrothermal launchers is also developed and itsfeasibility is theoretically and experimentally examined. In the experimental part of this thesis, the dependence of characteristics of themain discharge on the size of capillary, main capacitor and its initial charged voltageis obtained. The life expectation of TGCPG and the stability of the dischargecharacteristics under repetitive operation are examined. The dependence of thetrigger delay time of TGCPG on the capillary size and trigger energy is also studied. Two one-dimensional time-dependent models of TGCPG are proposed tosimulate the trigger process and the main discharge process respectively. Thedependence of the exit parameters such as plasma density, pressure, temperature andvelocity on the size of capillary, main capacitor and its initial charged voltage isstudied, the trigger delay time is also calculated and its comparison with theexperimental results gives a good agreement. It is found that capillary wall ablationcan greatly change the behavior of trigger discharge arc and drastically diminishesthe trigger delay time. In a word, this study focus on the characteristics of plasmas generated inTGCPG discharges by ablation-stabilized arcs, and some valuable conclusions aredrawn.