Calibration of grazing incidence spectrometers using charge transfer excitation

The sequence of radiative cascades following charge transfer between energetic neutral atoms and C6+, N7+, and O8+ are readily observed in high-temperature plasma devices where the field of view of a vacuum spectrometer includes a neutral heating beam. These charge exchange excited (CXE) lines have well defined relative intensities that are not strongly dependent on the theory used to compute the primary excitation. They have been exploited in the ISX-B tokamak as an in situ method of measuring the relative response of a grazing incidence spectrometer from 102 to 1164 A. Mixing of energy levels by external fields or by collisions are shown to have little effect on treating l as a good quantum number when computing the ratios of effective emission cross sections