Measurement of E × B drift of impurities in the C-2W inner divertor using spatial heterodyne spectroscopy

Edge control in the C-2W field-reversed configuration experiment is crucial for the stability and energy confinement of the core plasma. Such edge control is achieved by electrical biasing on the end-on electrode plates. The radial electric field generated by the electrode biasing can be measured by E × B induced drift of impurity ions. Spatial heterodyne spectroscopy (SHS) is a promising method of high light throughput spectroscopy. Doppler shifted spectra of O⁴⁺ ion emission lines have been measured using a novel, in-house built SHS system. The electric field in the jet plasma inside the inner divertor of C-2W was estimated using the temporal profile of the rotational velocity of the oxygen ions. SHS system details, obtained measurements, and the methods of improving the system performance will be discussed.