Characterization of edge radial electric field structures in the large helical device and their viability for determining the location of the plasma boundary

Kamiya, Kensaku; Ida, Katsumi*; Yoshinuma, Mikiro*; Suzuki, Chihiro*; Suzuki, Yasuhiro*; Yokoyama, Masayuki*; LHD Experimental Group*

This paper provides and proposes a new technique to determine the location of the LCFS that is based on a characterization of the structure derived from CXS measurements in the LHD. We found that the spatial derivative in the structure had the local maximum value at the region very near, or possibly outside the vacuum LCFS location of vacuum magnetic field at the outer midplane in the low plasma.