Diagnostics of tokamak divertor plasmas by Stark broadening of impurity emission lines

Line broadening by Stark and Doppler effects of some impurity spectral lines is proposed as a diagnostic tool for divertor plasmas. It is shown that the shape of the C IV n=6-7 λ~7726 Å line can be successfully used to infer the electron density averaged along the line of sight provided the electron and the ion temperatures are known. For illustrative purposes, the technique is applied to experimental data from the JT-60U tokamak. Using temperatures deduced from C IV line intensities, the line-integrated electron density and its spatial distribution around the X-point can be extracted from the shape of the C IV n=6-7 line.