SOFT-X-RAY EMISSION OF GALLIUM-LIKE RARE-EARTH ATOMS PRODUCED BY HIGH-TEMPERATURE LOW-DENSITY TOKAMAK AND HIGH-DENSITY LASER PLASMAS

Spectra of rare-earth atoms praseodymium, Z=59, to ytterbium, Z=70, em itted from the high-temperature (1 keV) low-density (10(13) cm-3) lase r TEXT tokamak (at the Fusion Research Center, University of Texas, Au stin) and high-density (10(20) cm-3) laser plasmas have been recorded in the soft-x-ray range of 50-200 angstrom with an image intensifier d etector and on photographic plates. The brightest n = 4 to n = 4 trans itions of galliumlike ions have been identified and their emission pat terns have been studied by comparison with ab initio atomic structure calculations and collisional radiative models under the respective pla sma conditions. We have investigated the use of the ratios of the inte nsities of 4-4 transitions as indicators of plasma densities. This is possible owing to the doublet structure of the galliumlike ground stat e, which leads to a strong density dependence for ratios of transition s between low-lying levels. We have also used semiempirical ionization balance calculations to characterize the charge state distribution of the tokamak plasmas, in preparation for an investigation of the use o f ratios of galliumlike to zinclike and copperlike emission features a s indicators of whether the impurities are in coronal equilibrium or u ndergoing ionization.