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Title: Tungsten Spectroscopy for Fusion Plasmas

Abstract

Tungsten is one of very few candidate materials for plasma facing components in future fusion devices. Therefore, investigations have been started at fusion devices and EBITs to provide atomic data for W in fusion plasmas. Usually the influx of impurities is deduced from the intensity of spectral lines from neutrals or ions in a low ionisation state. For this purpose the appropriate ionisation rates and excitation rates have to be known. At the moment, a WI transition (7S-7P) at 400.9 nm is used, but an extension of the method to other lines is under investigation. In the core of present day plasmas ionisation states up to W56+ can be reached and in a reactor states up to around W68+ will be present. In order to extract information on the local W concentrations over the whole plasma radius atomic data (wavelength, excitation, ionisation, recombination) for all the charge states up to the maximum ionisation state are necessary. Similarly, a high sensitivity has to be achieved since the central W concentrations should stay below 10-4. For an unambiguous identification of the transitions EBIT measurements are of great advantage, but due to the lower electron density compared to fusion plasmas, investigations there aremore » indispensable.« less

Authors:
; ;  [1]; ;  [2]
  1. Max-Planck-Institut fuer Plasmaphysik, Euratom Association, Boltzmannstr.2, 85748 Garching (Germany)
  2. Institut fuer Plasmaphysik, Euratom Association, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany)
Publication Date:
OSTI Identifier:
21056931
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 901; Journal Issue: 1; Conference: ICAMDATA: 5. international conference on atomic and molecular data and their applications, Meudon (France), 15-19 Oct 2006; Other Information: DOI: 10.1063/1.2727359; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA). ASDEX Upgrade Team; TEXTOR Team
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CHARGE STATES; ELECTRON DENSITY; EMISSION SPECTROSCOPY; EXCITATION; FIRST WALL; IONIZATION; MULTICHARGED IONS; PLASMA; PLASMA CONFINEMENT; PLASMA DIAGNOSTICS; PLASMA IMPURITIES; RECOMBINATION; SENSITIVITY; THERMONUCLEAR DEVICES; TUNGSTEN; TUNGSTEN IONS; WAVELENGTHS

Citation Formats

Neu, R., Puetterich, T., Dux, R., Pospieszczyk, A., and Sergienko, G. Tungsten Spectroscopy for Fusion Plasmas. United States: N. p., 2007. Web. doi:10.1063/1.2727359.
Neu, R., Puetterich, T., Dux, R., Pospieszczyk, A., & Sergienko, G. Tungsten Spectroscopy for Fusion Plasmas. United States. doi:10.1063/1.2727359.
Neu, R., Puetterich, T., Dux, R., Pospieszczyk, A., and Sergienko, G. 2007. "Tungsten Spectroscopy for Fusion Plasmas". United States. doi:10.1063/1.2727359.
@article{osti_21056931,
title = {Tungsten Spectroscopy for Fusion Plasmas},
author = {Neu, R. and Puetterich, T. and Dux, R. and Pospieszczyk, A. and Sergienko, G.},
abstractNote = {Tungsten is one of very few candidate materials for plasma facing components in future fusion devices. Therefore, investigations have been started at fusion devices and EBITs to provide atomic data for W in fusion plasmas. Usually the influx of impurities is deduced from the intensity of spectral lines from neutrals or ions in a low ionisation state. For this purpose the appropriate ionisation rates and excitation rates have to be known. At the moment, a WI transition (7S-7P) at 400.9 nm is used, but an extension of the method to other lines is under investigation. In the core of present day plasmas ionisation states up to W56+ can be reached and in a reactor states up to around W68+ will be present. In order to extract information on the local W concentrations over the whole plasma radius atomic data (wavelength, excitation, ionisation, recombination) for all the charge states up to the maximum ionisation state are necessary. Similarly, a high sensitivity has to be achieved since the central W concentrations should stay below 10-4. For an unambiguous identification of the transitions EBIT measurements are of great advantage, but due to the lower electron density compared to fusion plasmas, investigations there are indispensable.},
doi = {10.1063/1.2727359},
journal = {AIP Conference Proceedings},
number = 1,
volume = 901,
place = {United States},
year = 2007,
month = 4
}
  • The radiation emitted from highly charged tungsten ions has been measured at the Berlin Electron Beam Ion trap using high-resolution x-ray and EUV spectrometers. Highly charged tungsten ions ranging from Pm-like W{sup 13+} to N-like W{sup 67+} have been produced and excited in EBIT. The line emission originating from electric and magnetic dipole transitions is studied in a wide wavelength range from 0.12 to 80 nm. The results of our measurements are compared with predicted transition wavelengths from atomic structure calculations and observations at the ASDEX Upgrade tokamak. Here we focus on the quasi-continuum emission around 5 nm from tungstenmore » ions with an open 4 d shell (In-like W{sup 25+} to Rb-like W{sup 37+}) and the L-shell spectra of ions with configurations close to Ne-like one.« less
  • Under the auspices of the IAEA Atomic and Molecular Data Center and the Korean Atomic Energy Research Institute, our assembled group of authors has reviewed the current state of dielectronic recombination (DR) rate coefficients for various ion stages of tungsten (W). Subsequent recommendations were based upon available experimental data, first-principle calculations carried out in support of this paper and from available recombination data within existing atomic databases. If a recommendation was possible, data were compiled, evaluated and fitted to a functional form with associated uncertainty information retained, where available. In conclusion, this paper also considers the variation of the Wmore » fractional abundance due to the underlying atomic data when employing different data sets.« less
  • The shielding effects of ablation cloud around a small dust grain composed of iron, molybdenum, or tungsten in fusion plasmas are considered. These include collisional dissipation of momentum flux of impinging plasma ions, heat transfer by secondary plasma created due to electron impact ionization of the ablated atoms, and radiative plasma power losses in the ablation cloud. The maximum radius, which limits applicability of existing dust-plasma interaction models neglecting the cloud shielding effects, for dust grains of the considered high-Z metals is calculated as function of plasma parameters. The thermal bifurcation triggered by thermionic electron emission from dust grains, observedmore » for some of the considered materials, is analyzed. The results are compared with previous calculations for dust composed of low-Z fusion related materials, i.e., lithium, beryllium, and carbon.« less
  • The ITER tokamak will have tungsten divertor tiles and, consequently, the divertor plasmas are expected to contain tungsten ions. The spectral emission from these ions can serve to diagnose the divertor for plasma parameters such as tungsten concentrations, densities, ion and electron temperatures, and flow velocities. The ITER divertor plasmas will likely have densities around 10{sup 14-15} cm{sup -3} and temperatures below 150 eV. These conditions are similar to the plasmas at the Sustained Spheromak Physics Experiment (SSPX) in Livermore. To simulate ITER divertor plasmas, a tungsten impurity was introduced into the SSPX spheromak by prefilling it with tungsten hexacarbonylmore » prior to the usual hydrogen gas injection and initiation of the plasma discharge. The possibility of using the emission from low charge state tungsten ions to diagnose tokamak divertor plasmas has been investigated using a high-resolution extreme ultraviolet spectrometer.« less
  • The development of spectroscopic modeling of M-shell tungsten z-pinch plasma is presented. The spectral region from 3.5 to 6.5 A includes three distinct groups of transitions, and the best candidates for M-shell diagnostics are identified. Theoretical modeling is benchmarked with LLNL electron beam ion trap data produced at different energies of the electron beam and recorded by crystal spectrometers and a broadband microcalorimeter. A new high temperature plasma diagnostic tool, x-ray spectropolarimetry, is proposed to study polarization of W line emission and is illustrated using the results of x-pinch polarization-sensitive experiments. The x-ray line polarization of the prominent M-shell tungstenmore » lines is calculated, and polarization markers are identified. The advantage of using x-pinch W wire experiments for the development of M-shell diagnostics is shown.« less