Feasibility studies of a charge exchange recombination diagnostic for measurement of impurity flows in the divertor of the DIII-D tokamak

Charge exchange recombination, a well-established technique for measuring impurity flows and ion temperature in the core of tokamak plasmas, was evaluated for measuring the same plasma parameters in the divertor region of the DIII-D tokamak. Because divertor temperatures are typically much lower than those in the core, different charge exchange reaction processes must be considered. A combination of experimental measurements and code modeling were carried out to quantify the expected signal-to-background ratio. In conclusion, it was determined that a divertor charge exchange recombination diagnostic is not feasible, even employing lock-in detection methods to extract a beam-modulated signal from background radiation at the same wavelength. (author)