Probe Measurements in D. C. Plasma Jet

Some preliminary experiments concerning high speed probe techniques has been undertaken in D. C. plasma jet. A conductivity probe, a typical Langumuir probe and velocity probe were used for the investigation at the surface layer of the high temperature jet core. When a probe is operated in high temperature plasma flow, it appears unlikely that the static theory of the probe method will be directly applicable. So, Clayden's assumptions were given for the interpretation of results from our experiments. Thus, apparent plasma conductivity, apparent electron temperatures and ion densities were estimated and the probe current wave form were studied. It was found that the electrical conductivity of plasma jet increased significantly with the arc current. Typical values of specific resistance were less than 300KΩ・cm which is equal to the resistance of the seeded Argon plasma. The results obtained from the measurements by the Langmuir probe and the velocity probe were as follows. The electron temperature were 6500°K for Nozzle N-2,12000°K for Nozzle N-5 and the ion densities were 4.08×10^<14>ions/cm^3 for N-5,9.91×10^<14>ions/cm^3 for N-11 respectively. A random pulse observed in the probe current vanished with the increase of the arc current.