| 1. |
- Clementson, Joel, et al.
(författare)
-
Atomic data and theoretical X-ray spectra of Ge-like through V-like W ions
- 2014
-
Ingår i: Atomic Data and Nuclear Data Tables. - : Elsevier BV. - 0092-640X. ; 100:2, s. 577-649
-
Tidskriftsartikel (refereegranskat)abstract
- The atomic structure and spectra of ten tungsten ions have been calculated using the Flexible Atomic Code. The calculations yield energy levels, radiative lifetimes, spectral line positions, transition probability rates, and oscillator strengths for the tungsten ions isoelectronic to germanium, W42+, through vanadium, W51+. Collisional-radiative models for high-temperature, low-density plasmas have been implemented to produce line emissivities for X-ray transitions in the 1-4 keV (3-12 angstrom) spectral interval. The Ge-like through V-like W ions are important in nuclear fusion research where their spectra may provide diagnostic information on magnetically confined plasmas. (C) 2013 Elsevier Inc. All rights reserved.
|
|
| 2. |
- Clementson, Joel, et al.
(författare)
-
Experimental setup for tungsten transport studies at the NSTX tokamak
- 2010
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 81:10
-
Konferensbidrag (refereegranskat)abstract
- Tungsten particles have been introduced into the National Spherical Torus Experiment (NSTX) in Princeton with the purpose to investigate the effects of tungsten injection on subsequent plasma discharges. An experimental setup for the study of tungsten particle transport is described where the particles are introduced into the tokamak using a modified particle dropper, otherwise used for lithium-powder injection. An initial test employing a grazing-incidence extreme ultraviolet spectrometer demonstrates that the tungsten-transport setup could serve to infer particle transport from the edge to the hot central plasmas of NSTX. (C) 2010 American Institute of Physics. [doi:10.1063/1.3499607]
|
|
| 3. |
- Clementson, Joel, et al.
(författare)
-
Extreme Ultraviolet Spectra of Few-Times Ionized Tungsten for Divertor Plasma Diagnostics
- 2015
-
Ingår i: Atoms. - : MDPI AG. - 2218-2004. ; 3:3, s. 407-421
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 4. |
- Clementson, Joel, et al.
(författare)
-
Grazing-incidence spectrometer on the SSPX spheromak
- 2008
-
Ingår i: Review of scientific instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 79:10, s. 10-538
-
Konferensbidrag (refereegranskat)abstract
- The silver flat field spectrometer (SFFS) is a high-resolution grazing-incidence diagnostic for magnetically confined plasmas. It covers the wavelength range of 25-450 A with a resolution of Delta lambda=0.3 A full width at half maximum. The SFFS employs a spherical 1200 lines/mm grating for flat-field focusing. The imaging is done using a backilluminated Photometrics charge-coupled device camera allowing a bandwidth of around 200 A per spectrum. The spectrometer has been used for atomic spectroscopy on electron beam ion traps and for plasma spectroscopy on magnetic confinement devices. Here we describe the design of the SFFS and the spectrometer setup at the sustained spheromak physics experiment in Livermore.
|
|
| 5. |
- Clementson, Joel
(författare)
-
Spectroscopic Investigations of Highly Charged Tungsten Ions - Atomic Spectroscopy and Fusion Plasma Diagnostics
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The spectra of highly charged tungsten ions have been investigated using x-ray and extreme ultraviolet spectroscopy. These heavy ions are of interest in relativistic atomic structure theory, where high-precision wavelength measurements benchmark theoretical approaches, and in magnetic fusion research, where the ions may serve to diagnose high-temperature plasmas. The work details spectroscopic investigations of highly charged tungsten ions measured at the Livermore electron beam ion trap (EBIT) facility. Here, the EBIT-I and SuperEBIT electron beam ion traps have been employed to create, trap, and excite tungsten ions of M- and L-shell charge states. The emitted spectra have been studied in high resolution using crystal, grating, and x-ray calorimeter spectrometers. In particular, wavelengths of ∆n = 0 M-shell transitions in K-like W55+ through Ne-like W64+, and intershell transitions in Zn-like W44+ through Co-like W47+ have been measured. Special attention is given to the Ni-like W46+ ion, which has two strong electric-dipole forbidden transitions that are of interest for plasma diagnostics. The EBIT measurements are complemented by spectral modeling using the Flexible Atomic Code (FAC), and predictions for tokamak spectra are presented. The L-shell tungsten ions have been studied at electron-beam energies of up to 122 keV and transition energies measured in Ne-like W64+ through Li-like W71+. These spectra constitute the physics basis in the design of the ion-temperature crystal spectrometer for the ITER tokamak. Tungsten particles have furthermore been introduced into the Sustained Spheromak Physics Experiment (SSPX) spheromak in Livermore in order to investigate diagnostic possibilities of extreme ultraviolet tungsten spectra for the ITER divertor. The spheromak measurement and spectral modeling using FAC suggest that tungsten ions in charge states around Er-like W6+ could be useful for plasma diagnostics.
|
|
| 6. |
- Clementson, Joel, et al.
(författare)
-
Spectroscopy of M-shell x-ray transitions in Zn-like through Co-like W
- 2010
-
Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 81:1, s. 1-015301
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 7. |
- Clementson, Joel, et al.
(författare)
-
Tungsten spectroscopy relevant to the diagnostics of ITER divertor plasmas
- 2010
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 43:14
-
Tidskriftsartikel (refereegranskat)abstract
- The possibility of using extreme ultraviolet emission from low charge states of tungsten ions to diagnose the divertor plasmas of the ITER tokamak has been investigated. Spectral modelling of Lu-like W3+ to Gd-like W10+ has been performed by using the Flexible Atomic Code, and spectroscopic measurements have been conducted at the Sustained Spheromak Physics Experiment (SSPX) in Livermore. To simulate ITER divertor plasmas, tungsten was introduced into the SSPX spheromak by prefilling it with tungsten hexacarbonyl prior to the usual hydrogen gas injection and initiation of the plasma discharge. The tungsten emission was studied using a grazing-incidence spectrometer.
|
|
| 8. |
- Clementson, Joel, et al.
(författare)
-
Wavelength measurement of n = 3 to n = 3 transitions in highly charged tungsten ions
- 2010
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 81:5, s. 1-052509
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 9. |
- Clementson, Joel, et al.
(författare)
-
X-ray spectroscopy of E2 and M3 transitions in Ni-like W
- 2010
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 81:1
-
Tidskriftsartikel (refereegranskat)abstract
- The electric quadrupole (E2) and magnetic octupole (M3) ground-state transitions in Ni-like W46+ have been measured using high-resolution crystal spectroscopy at the LLNL electron-beam ion trap facility. The lines fall in the soft x-ray region near 7.93 angstrom and were originally observed as an unresolved feature in tokamak plasmas. Using flat ammonium dihydrogen phosphate and quartz crystals, the wavelengths, intensities, and polarizations of the two lines have been measured for various electron-beam energies and compared to intensity and polarization calculations performed using the Flexible Atomic Code (FAC).
|
|
| 10. |
- Lennartsson, Thomas, et al.
(författare)
-
Experimental wavelengths for intrashell transitions in tungsten ions with partially filled 3p and 3d subshells
- 2013
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 87:6
-
Tidskriftsartikel (refereegranskat)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.
|
|
