Diagnostics of JT-60U divertor plasmas by Stark-Doppler broadening of carbon spectral lines

Line broadening by Stark and Doppler effects of C iv line spectra is suggested for the diagnostic of detached JT-60U divertor plasmas. Owing to the competition between Stark and Doppler broadening mechanisms, the C IV n = 6-7 (λ ∼ 7726 A) line profile depends on both the plasma electron density and temperature and the C3+ ion temperature. C IV n = 6-7 line spectra, measured during an X-point MARFE phase in the JT-60U divertor using a high-resolution visible spectrometer, are fitted assuming the same temperature for both electrons and ions in order to determine the average electron density along the line of sight. These average electron densities deduced from the fit of C IV n = 6-7 spectral line shapes corroborate those obtained using C IV line intensities and collisional-radiative modeling. Line broadening of C IV spectra is proposed to be used for the spatial characterization of the JT-60U divertor.