Relative calibration of grazing incidence spectrometers from charge-exchange excitation of hydrogenic ions

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Abstract
Charge transfer from hydrogen atoms having energies below 35 keV to fully ionized low-Z impurities takes place predominantly in two excited levels. It is shown that the subsequent radiative cascades from C5+, N6+; and O7+ can be used to obtain the relative response of grazing incidence spectrometer systems in the region between 102 and 1164 Å. In principle, the technique can be extended to 19 Å. The method is useful in plasma devices employing neutral beams for heating or for diagnostic probing. The absolute sensitivity of a system is then established by normalizing to only one branching ratio measurement from a pair of lines having accurately known transition probabilities. Results from the Impurity Studies Experiment-B (ISX-B) tokamak are presented.