Determination of radial electric field from Pfirsch-Schlter flows in the HSX stellarator

Inboard/outboard asymmetry in the impurity ion parallel flow is observed in the HSX stellarator using charge exchange recombination spectroscopy (CHERS). This observation shows the presence of counter-streaming Pfirsch-Schlter flow predicted by neoclassical theory. The asymmetry of the flow is used to calculate the magnitude and direction of the radial electric field (E-r), as well as the mean flow, using computed magnetic geometry factors. This method enables calculation of E-r near the core of the HSX plasma where the E-r obtained from the radial force balance equation has large uncertainties due to the relatively large width of the diagnostic neutral beam with respect to the plasma minor radius.