Observation of Tungsten Line Emissions in Wavelength Range of 10 - 500 Å in Large Helical Device

Abstract

Tungsten spectra have been observed in Large Helical Device (LHD) by injecting a coaxial tungsten pellet to identify the emission lines in extreme ultraviolet (EUV) range of 10 - 500 Å. The spectra of line emissions from tungsten ions have been measured in neutral-beam-heated discharges using two EUV spectrometers of EUV_Short and EUV_Long working in wavelength ranges of 10 - 130 Å and 50 - 500 Å, respectively. As a result, a lot of tungsten lines from low-ionized ions of W⁴⁺, W⁶⁺ and W⁷⁺ are observed for the first time in the toroidal device in addition to tungsten lines from highly ionized ions of W⁴¹⁺-W⁴⁵⁺. Measured line emissions are carefully identified based on the NIST database and the determined wavelengths show a good agreement with the NIST database. The result is summarized in table with information on blended lines obtained from the radial profile measurement.