A Convenient Method of Calibrating Relative Sensitivity of Multi-Channel Thomson Scattering Diagnostic System

LHD is equipped with a 200-channel Thomson scattering diagnostic, which can yield electron temperature {\textbf{\textit{Te}}} and density {\textbf{\textit{ne}}} profiles along the major radius passing the magnetic axis. Though the {\textbf{\textit{Te}}} profiles are of fairly good quality, the {\textbf{\textit{ne}}} profiles are far from satisfactory due to incomplete sensitivity calibration of each polychromator. In order to elaborate this issue more efficiently, we are developing a versatile method of calibration: To simulate light coming from the scattering volumes in a plasma and passing the view window, we used light diffusively reflected from a BaSO$_4$-coated plate set on the surface of the viewing window in the airside, which is illuminated by 10 ns pulse light from an OPO with wavelength scanned between 600-1060 nm. Combining the scattering length and the solid angle for each spatial-channel with the polychromator-sensitivity thus obtained, we can obtain the coefficients necessary for deducing {\textbf{\textit{ne}}} profile. We will examine the {\textbf{\textit{ne}}} profiles at the position where the structures are observed on {\textbf{\textit{Te}}} profiles.