Characterization of capillary plasmas with different diameter [electrothermal guns]

The operation of an electrothermal gun is strongly related to capillary discharges. The operation of an electrothermal gun with a small capillary diameter is superior to one with a large diameter in the vacuum. In order to understand these experimental results clearly, the plasma parameters of electron density and temperature, which are strongly related to the operation characteristics of the electrothermal gun, were measured for different capillary diameters by spectroscopic and interferometer measurements. The electron density and temperature of the capillary plasma increase with decreasing the capillary diameter. The early operation of the electrothermal gun with a small capillary diameter is superior to that with a large capillary diameter because of the increase of the capillary plasma pressure. The electron density was also measured by an interferometer measurement in order to validate the density estimated by the spectroscopic measurement. The electron densities, 10/sup 17/-10/sup 19/ cm/sup -3/, estimated by the interferometer measurement agree with those from the spectroscopic measurement.