Energy-mass coupling in high-pressure liquid-injected arcs

Highly collisional, low-temperature plasmas are created by discharging a 25- mu s, 40-160-J current pulse through a quartz capillary tube of a few millimeters diameter, into which liquid water is injected. Discharge electrical resistance is measured as a function of current, capillary diameter, axial position, and radial distribution of the liquid. Time-resolved spectra show strong line emission at early times and continuum emission later in the pulse, indicating a transition from a 3-4-eV optically thin plasma to a 1-2-eV plasma that is optically thick. The spectra are used to measure mean electron density and plasma temperature at early times. A one-dimensional, unsteady numerical model of plasma properties and total electrical resistance is presented which gives good agreement with experimental resistance measurements.< >