Tuesday, September 26, 2017
A rigorous way to analyze flush mounted Langmuir probes has yet to be developed. All current techniques involve the fitting of a free parameter to account for the expansion of the sheath. The 'rail' probe design currently installed on Alcator C-Mod circumvents the need for this by mitigating the effects of sheath expansion. However, there still exist discrepancies between the two probe designs: electron temperature and floating potential measurements; ion saturation current and floating potential fluctuations; and ion to electron saturation current ratios. One possible reason for these discrepancies may lie in the return current pathway through the plasma. Preliminary results from this analysis have been promising and further investigation is ongoing.