Temperature measurement of N/sub 2/-H/sub 2/ plasma by emission spectroscopy

Summary form only given, as follows. Measurement of plasma temperature has been performed by the emission spectroscopy technique. A 9 MB Metco Gun was used with nitrogen as the primary gas (80 scfh), hydrogen as the secondary gas (15 scfh) and air as the environment gas. Gun current of 500 A, with voltage of 73 V, was selected. The optical system scans the plasma and collects the light emitted by the plasma. A special scanner is used to quickly scan the plasma field. The continuum spectrum at 4955 /spl Aring/ is chosen for the measurement. Data evaluation is based on the assumptions that the plasma is axisymmetric, in local thermodynamic equilibrium, and the ratio of nitrogen and hydrogen remains constant throughout the plasma. The electron density of the N/sub 2/-H/sub 2/ mixture is calculated and used to obtain the temperature from the measured continuum emission coefficients. Also, the free-bound and free-free factors are included in the relationship between temperature and emission coefficients. Plasma temperatures were determined at axial locations to 20 mm from the nozzle exit. The temperatures range from 9050 K to 13580 K, for axial locations from 2 mm to 20 mm from the nozzle exit and for radial distances from the axis to 2.54 mm. Measured temperatures are compared with numerical modeling results. Temperature differences at the centerline are about 10%. Measured temperatures are much higher (more than 50%) than those calculated when the radial distances are more than 2 mm and the axial stations are greater than 10 mm.