DIAGNOSING SELENIUM PLASMAS USING SE-XXVI AND SE-XXXV LINE CLUSTER RATIOS

Ratios of resonance and satellite line clusters in fluorinelike (Se XX VI) and neonlike (Se XXV) ions are used in the development of a diagno stics procedure for analyzing high density, optically thin selenium pl asmas. The atomic model employed in this work to calculate line intens ities for n=2-3 transitions includes detailed fine-structure levels fo r the n=3 excited configurations, n=3 inner-shell excited states at th e configuration level, and lumped n=4 levels for both Se XXVI and Se X XV. All relevant atomic processes connecting these levels and all coll isional couplings among the excited states are included in the model. The collisional and radiative data such as collisional excitation and ionization (including inner shell), and both radiative and dielectroni c recombination rates, are obtained using several different sophistica ted atomic codes. From these data, collisional-radiative equilibrium s olutions to a fully coupled single set of rate equations are obtained for the populations of the ground as well as all excited levels, and u sed for the computation of the line intensities. For calculations of t he satellite line intensities, populations of the doubly excited state s are obtained from the sum of contributions from dielectronic recombi nation of ground states and inner-shell excitation of singly excited s tates. Because experimental L-shell spectra of the n=2-3 resonance and satellite lines contain many lines, often they are not spectroscopica lly resolved unless obtained under extremely high resolution. Therefor e, instead of using individual lines which often cannot be separated e xperimentally from other overlapping lines, resonance line as well as satellite line configuration clusters in Se XXVI and Se XXV are used i n this diagnostic work. The intensity ratios of the resonance and sate llite line clusters are functions of both electron temperature and ion density and simultaneous determinations of these quantities are possi ble using contour plots of specific cluster ratios. These plots are ob tained for a wide range of densities and temperatures, and they reflec t the detailed effects of the different atomic processes on the intens ities of the resonance and satellite lines as a function of plasma con ditions.