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| 2. |
- Clementson, Joel, et al.
(author)
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Extreme Ultraviolet Spectra of Few-Times Ionized Tungsten for Divertor Plasma Diagnostics
- 2015
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In: Atoms. - : MDPI AG. - 2218-2004. ; 3:3, s. 407-421
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Journal article (peer-reviewed)abstract
- The extreme ultraviolet (EUV) emission from few-times ionized tungsten atoms has been experimentally studied at the Livermore electron beam ion trap facility. The ions were produced and confined during low-energy operations of the EBIT-I electron beam ion trap. By varying the electron-beam energy from around 30-300 eV, tungsten ions in charge states expected to be abundant in tokamak divertor plasmas were excited, and the resulting EUV emission was studied using a survey spectrometer covering 120-320 angstrom. It is found that the emission strongly depends on the excitation energy; below 150 eV, it is relatively simple, consisting of strong isolated lines from a few charge states, whereas at higher energies, it becomes very complex. For divertor plasmas with tungsten impurity ions, this emission should prove useful for diagnostics of tungsten flux rates and charge balance, as well as for radiative cooling of the divertor volume. Several lines in the 194-223 angstrom interval belonging to the spectra of five- and seven-times ionized tungsten (Tm-like W vi and Ho-like W viii) were also measured using a high-resolution spectrometer.
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| 3. |
- Clementson, Joel, et al.
(author)
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Spectroscopy of M-shell x-ray transitions in Zn-like through Co-like W
- 2010
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In: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 81:1, s. 1-015301
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Journal article (peer-reviewed)abstract
- The M-shell x-ray emission of highly charged tungsten ions has been investigated at the Livermore electron beam ion trap facility. Using the SuperEBIT electron beam ion trap and a NASA x-ray calorimeter array, transitions connecting to levels of the ground configurations in the 1500–3600 eV spectral range of zinc-like W44+ through cobalt-like W47+ have been measured. The measured spectra are compared with theoretical line positions and emissivities calculated using the FAC code.
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| 4. |
- Clementson, Joel, et al.
(author)
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Wavelength measurement of n = 3 to n = 3 transitions in highly charged tungsten ions
- 2010
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In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 81:5, s. 1-052509
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Journal article (peer-reviewed)abstract
- 3s1/2-3p3/2 and 3p1/2-3d3/2 transitions have been studied in potassiumlike W55+ through neonlike W64+ ions at the electron-beam ion trap facility in Livermore. The wavelengths of the lines have been measured in high resolution relative to well known reference lines from oxygen and nitrogen ions. Using the high-energy SuperEBIT electron-beam ion trap and an R = 44.3 m grazing-incidence soft-x-ray spectrometer, the lines were observed with a cryogenic charge-coupled device camera. The wavelength data for the sodiumlike and magnesiumlike tungsten lines are comparedwith theoretical predictions for ions along the isoelectronic sequences.
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| 5. |
- Lennartsson, Thomas, et al.
(author)
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Experimental wavelengths for intrashell transitions in tungsten ions with partially filled 3p and 3d subshells
- 2013
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In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 87:6
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Journal article (peer-reviewed)abstract
- Spectra and measured wavelengths of intrashell n = 3 transitions in highly charged tungsten ions with partially filled 3p and 3d valence shells, Al-like W61+ through Fe-like W48+, are presented. The ions were created and excited at the electron-beam ion-trap facility at the Lawrence Livermore National Laboratory and measured with a high-resolution grazing-incidence spectrometer. The spectral lines were studied in the 27-41 angstrom range and were analyzed by a comparison with synthetic spectra based on a collisional-radiative model. We determined that the emission includes not only electric-dipole-allowed transitions, but also several electric-quadrupole and magnetic-dipole transitions. Line-position uncertainties as low as 25 ppm were achieved. Thus, our measurements provide much-needed benchmarks for calculations of the atomic structure of highly charged ions with a partially filled subshell, since these ions are difficult to calculate due to electron-correlation effects.
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