SPATIALLY AND TEMPORALLY RESOLVED EMISSION AND FLUORESCENCE IN A POWER MODULATED INDUCTIVELY COUPLED PLASMA

Energy coupling, vertical transport and radial transport processes were studied via time and space resolved Ba II emission and fluorescence measurements. The Ba II emission to fluorescence intensity ratios in the first 2 ms following an abrupt decrease in power were consistent with some coupling of energy more than 10-15 mm above the load coil. During this time changes in excitation were dominant over variations in Ba ion number density. There was no evidence of radially dependent cooling of the plasma. At times later than 3 ms from the decrease in power, large changes in Ba+ number density were observed. The Ba+ number density changes were consistent with transport of cooler gas from below. The Ba II emission and fluorescence behavior following an abrupt increase in power was consistent with production of energetic species low in the plasma followed by transport upward and inward. At 9 mm above the load coil and higher, vertical transport processes were more important than radial transport. Emission response times for species with a wide range of excitation energies were similar to those expected from equilibrium models except for two Mg II lines. The sum of excitation and ionization energies for the two anomalously behaving Mg II lines was greater than 16 eV, precluding excitation via charge transfer from ground state Ar ions. © 1990.