HIGH-RESOLUTION MEASUREMENTS, LINE IDENTIFICATION, AND SPECTRAL MODELING OF K-ALPHA TRANSITIONS IN FE-XVIII-FE-XXV

A detailed analysis of the iron Kalpha emission spectrum covering the wavelength region from 1.840 to 1.9 angstrom is presented. Measurement s are made with a high-resolution Bragg crystal spectrometer on the Pr inceton Large Torus (PLT) tokamak for plasma conditions which closely resemble those of solar flares. A total of 40 features are identified, consisting of either single or multiple lines from eight charge state s in iron, Fe XVIII-Fe XXV, and their wavelengths are determined with an accuracy of 0.1-0.4 mangstrom. Many of these features are identifie d for the first time. In the interpretation of our observations we rel y on model calculations that determine the ionic species abundances fr om electron density and temperature profiles measured indePendently wi th nonspectroscopic techniques and that incorporate theoretical collis ional excitation and dielectronic recombination rates resulting in the excitation of the ls2s(r)2p(s) configurations. The model calculations also include the effect of diffusive ion transport. Good overall agre ement between the model calculations and the observations is obtained, which gives us confidence in our line identifications and spectral mo deling capabilities. The results are compared with earlier analyses of the Kalpha emission from the Sun. While many similarities are found, a few differences arise from the somewhat higher electron density in t okamak plasmas (10(13) cm-3), which affects the fine-structure level p opulations of the ground states of the initial ion undergoing electron -impact excitation or dielectronic recombination. We also find that se veral spectral features are comprised of different transitions from th ose reported in earlier analyses of solar data.