Spectra of ${\mathrm{W}}^{19+}-{\mathrm{W}}^{32+}$ observed in the EUV region between 15 and $55\AA$ with an electron-beam ion trap

We present extreme ultraviolet spectra of highly charged tungsten ions (${\mathrm{W}}^{19+}-{\mathrm{W}}^{32+}$) in the wavelength range of $15-55\AA$ obtained with a compact electron-beam ion trap (CoBIT) and a grazing-incidence spectrometer at the National Institute for Fusion Science. The electron energy dependence of the spectra was investigated for electron energies from 490 to $1320\mathrm{eV}$. Identification of the observed lines was aided by collisional-radiative (CR) modeling of CoBIT plasma. Good quantitative agreement was obtained between the CR-modeling results and the experimental observations. The ion charge dependence of the $6g\text{−}4f,5g\text{−}4f,5f\text{−}4d,5p\text{−}4d$, and $4f\text{−}4d$ transition wavelengths were measured.

Figure 1

EUV spectra of highly charged tungsten ions obtained at electron energy $E_e$ from 490 to $1320\mathrm{eV}$ in the wavelength range of $15-55\AA$. The peaks denoted by arrows were identified from comparison with the CR model. “Max. charge state” means the highest charge state of tungsten ions which can be produced in CoBIT at electron energy $E_e$.

Figure 2

Experimental spectra in CoBIT and calculated spectra of the CR model at electron energy $E_e=800\mathrm{eV}$ in the range of $15-45\AA$. The top panel is the CR-model calculation spectrum. The middle panel is the sum of these spectra. The bottom panel is the experimentally measured spectrum of CoBIT.

Figure 3

Experimental spectra in CoBIT and calculated spectra of the CR model at electron energy $E_e=1210$ and $1200\mathrm{eV}$ in the range of $15-45\AA$, respectively. The transition and wavelength of the lines labeled by numbers are shown in Table 1.

Figure 4

The charge dependence of the wavelength for each emission line. A circle, an open circle, a square, and an open square are the experimental values corresponding to the $6g\text{−}4f,5f\text{−}4d,5g\text{−}4f$, and $5p\text{−}4d$ lines, respectively. The dot-dashed line, dotted line, two-dot-dashed line, and dashed line, respectively, are the calculated wavelengths corresponding to the same transitions array in the above by our CR model.

Figure 5

Experimental spectra in CoBIT and calculated spectra of the CR model at electron energy $E_e=1210$ and $1200\mathrm{eV}$ in the range of $40-55\AA$, respectively. The transition and wavelength of these numbering lines are shown in Table 2.