Measured and modeled radiation profiles for LHD plasma. A comparison during plasma detachment

Detached (from the divertors) plasma regime is a very important operational phase for future fusion device operation and is sustained in the Large Helical Device (LHD) by applying an m/n = 1/1 resonant magnetic perturbation (RMP). The radiation from the plasma is found to be localized near the X-point of this RMP during plasma detachment which is confirmed both by the EMC3-EIRENE edge impurity transport code and experiments. This agreement motivates the establishment of a comparison between the results from the transport model and InfraRed imaging Video Bolometer (IRVB) experiments. A synthetic instrument has been developed which can simulate the radiation by tracing the sight lines through the three dimensional carbon impurity radiation results of the EMC3-EIRENE, giving a synthetic image. These synthetic images can be compared with the IRVB image obtained experimentally. Such a comparison is attempted here for two IRVBs installed on LHD for the data from the 2012 and 2013 experimental campaigns. The comparison reveals a fair amount of qualitative agreement but quantitative disagreement among both the approaches. Probable causes for the disagreement are discussed and corrective measures are suggested. (author)