Progress in impurity study based on EVU spectrometers in HL-2A

Two extreme ultraviolet (EUV) spectrometers have been developed on HL-2A with different purposes related to impurity study. One of them (EUVL-I) is used to measure the spectral wavelength with high time response for impurity monitoring, and the other one (EUVL-II) with space-resolved capability is used to measure the vertical distribution of impurity line emissions in HL-2A plasma. The absolute intensity calibration of EUVL-II spectrometer is done by comparing the bremsstrahlung continuum intensity between EUV and visible wavelength ranges. The line of sight of EUVL-II is inclined to a downward direction to measure an entire profile of the impurity line emission at lower half (0≤Z≤-40cm) of HL-2A tokamak plasmas. The vertical position of impurity profile is absolutely calibrated by a metal bar with different widths installed at the diagnostic port, and the calibration is done with changing wavelengths. The spectra of tungsten introduced by laser blow-off (LBO) system is recorded by the EUVL-I spectrometer, and quasi-continuum spectra of tungsten is observed in three wavelength ranges of 25-42A, 47-70A and 140-280A. In addition, isolated line emissions of tungsten emitted from W⁶⁺ ion are measured for the first time in tokamak plasma, and are identified as 216.219A (5p-5d) and 261.387A (5p-5d), respectively. (author)