Visible bremsstrahlung has been measured to evaluate the effective charge (Z_eff) in high-temperature plasmas. In high-temperature plasmas, it is known that a visible spectrum consists of continuum emissions including bremsstrahlung and line emissions, which existence is not desirable for the correct bremsstrahlung measurement. In order to observe the temporal- and spatial-resolved visible bremsstrahlung, a visible monochromatic system with optical interference filter and a visible spectrometer with CCD detector were installed on the Large Helical Device [1]. A central wavelength of 536.6nm and FWHM of 6.2nm was carefully chosen as the interference filter to avoid the contribution of spectral lines. In this wavelength region, however, many carbon emission lines such as CVI (529nm : n=8 to 7) and CI were detected in hydrogen plasmas. In addition, HeII (541nm : n=6 to 2) line was strongly emitted in helium plasmas. Intensities of the observed emission lines depend on discharge conditions. The percentage of line emissions to bremsstrahlung can be evaluated from the spectrum recorded by the spectrometer. As a result, the contribution of emission lines in helium plasmas was lower than that in hydrogen plasmas. In this paper, results of the spectral analysis in such visible range is reported as a function of fuel gas species, heating methods and wall conditioning such as He and Ne glow discharges, titanium gettering and boronization.

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