BEHAVIOR OF CAPILLARY PLASMAS WITH DIFFERENT DIAMETERS

During the early phase of electrothermal gun operation, the operation characteristics improve at low ambient pressures because the discharge occurs on the surface of the capillary: resulting in-a higher rite of wall ablation and a higher capillary plasma density than in the case or operation at higher ambient pressures. In addition, it has been rep orted that reduction of the capillary diameter at low pressures result s in an increase that in the kinetic energy of the projectile. Al low pressures, an electrothermal gun with a small capillary diameter is th erefore superior to one with a large capillary diameter. In order to u nderstand these experimental results clearly, we measured the plasma p arameters of electron density and temperature, which are strongly rela ted to the operation characteristics of the electrothermal gun, for di fferent capillary diameters using a spectroscopic technique, and compa red the results with results for a zero-dimensional time-dependent mod el. The electron density of the capillary plasma increases with decrea sing capillary diameter.