Capillary discharge in the open air

It is important to understand the physical processes contributed by the plasma injector in the development of an electrothermal-chemical (ETC) gun. To investigate basic properties of a capillary discharge, an injector was discharged in open air. Comparing the measured and the calculated plasma resistivities, the state of power balance was investigated. The capillary plasma discharged in open air showed large ejection of plasma without power-balancing, while the capillary plasma produced in the ETC gun experiment reaches near balanced steady-state as the pressure of the combustion chamber becomes appreciable. The ejected flames were monitored with a high-speed camera. Typically the observed flames were about 50 cm /spl sim/1 m long and 25 cm wide. To estimate temperature and density, a preliminary measurement of time-resolved spectra in the visible wavelength region was done.