Temperature measurements in a laminar plasma jet generated at reduced pressure

Abstract

a b s t r a c t Double electrostatic probe method and Boltzmann-plot method are applied to measure the electron temperature and the excitation temperature of a DC laminar argon plasma jet generated at reduced pressure. Attempts are also made to measure the gas temperature by using a pair of WRe-5/26 thermocouple. Experimental results show that the measured excitation temperature at the jet center increases with the vacuum chamber pressure and the arc current, but is appreciably lower than the measured electron temperature, indicating that the plasma jet under study is evidently deviated from the LTE state. The temperature indicated by the thermocouple probe is much lower than the measured excitation temperature and electron temperature. Theoretical analysis shows that the thermocouple method intended for gas temperature measurement contains very large errors due to rarefied-gas heat transfer effects, and thus is unsuitable for this purpose.

The distribution pattern of the electron density and the electron temperature in a weakly compressible argon plasma jet measured by a Langmuir triple probe

“…The integration of equation ( 25) requires an initial value, but which is unknown, so in the calculation, the ξ m at initial point (i.e. Z = 11 mm, denoted ξ m,11 mm ) is tested over a wide range with 16 values of 0.0001, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.1. n t is set to 10 22 m −3 , corresponding to the characteristic gas temperature of 1450 K [48].…”