Effective γ x-ray excitation rates for plasma imputity measurements

This paper discusses metal impurity concentrations measured by the pulse-height-analyzer diagnostic from Kα x-ray peak intensities by use of an averaged excitation rate left-angle σv right-angle. Low-z impurity concentrations are inferred from the continuum enhancement due to metals. Since the PHA does not resolve lines from different charge states, left-angle σv right-angle is a weighted sum of rates; coronal equilibrium is usually assumed. Improved values of left-angle σv right-angle using recent calculations for H-, He-, and Li-like Fe are 45% larger than the earlier rates and yield metal concentrations in better agreement with those from VUV spectroscopy. The effect of charge exchange with neutral hydrogen on coronal equilibrium and left-angle σv right-angle is considered