Modeling fast charge exchange recombination spectroscopy measurements from the Madison Symmetric Torus

Charge exchange recombination spectroscopy measurements of impurity ion temperature !Ti" and velocity !vi" on the Madison Symmetric Torus present a unique challenge due to two coupled effects: low temperature—typically 300–500 eV, though up to 2 keV in high current plasmas—and a dominant contribution from background, i.e., non charge exchange driven, emission. For low Ti, the background emission line shape is significantly asymmetric as a result of spin-orbit coupling effects. Accurate modeling of both the background and beam emission is therefore required to obtain precise values for local ion parameters. A model has been developed to provide robust simulation of the experimental measurements with #10 !s temporal resolution using atomic data obtained from the Atomic Data and Analysis Structure database. Measurements are made using C VI emission at 343.4 nm, with background and beam emissions obtained simultaneously using two fiber bundles with slightly displaced lines of sight. Emission from O VI contributes substantially to the background signal, and is included in the modeling. A complete description of the model will be presented, along with results for Ti measurements during magnetic reconnection. © 2006 American Institute of Physics. $DOI: 10.1063/1.2219412%