Electron temperature and density sensitive X-ray emission line ratios for CI XVI

Recently calculated electron impact excitation rates for transitions in helium-like CI XVI are used to derive the electron temperature sensitive emission line ratio G = [( x + y + z )/ w ] and the electron density sensitive ratio R = [ z /( x + y )] where w, x, y and z are the resonance 1 s 2 1 S 0 -1 s 2 p 1 P 1 , intercombination 1 s 2 1 S 0 -1 s 2 p 3 P 2,1 and forbidden 1 s 2 1 S 0 -1 s 2 s 3 S 1 transitions, respectively. These calculations, which differ from those of previous authors, are compared with experimental R and G ratios obtained from X-ray spectra from the JET (Joint European Torus) plasma, for which the electron temperature and density have been measured by independent methods. The R ratio is approximately in its low density limit ( R o ) for this device and is therefore not electron density sensitive. However it does function as an electron temperature diagnostic as does the G ratio. A comparison is also made with the previously reported results from the Alcator-C tokamak, where the experimental results lie in the electron density sensitive region. The current results show good agreement between theory and observation, with discrepancies of typically 7% in R o and 10% in G for JET, implying that the theoretical results may be applied to the analysis of remote plasma sources in order to derive values for these parameters, where no independent measurements exist. A departure from coronal equilibrium due to diffusion effects is taken into account for the JET plasma conditions, and the resulting non-coronal ionization balance is found to produce changes to the theoretical ratios at temperatures exceeding T m .