| 1. |
- Blom, Anders, et al.
(författare)
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Parametrization of the Zeeman effect for hydrogen-like spectra in high-temperature plasmas
- 2002
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335. ; 44:7, s. 1229-1241
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for parametrizing the Zeeman effect in hydrogen-like systems in high-temperature plasmas, where the fine-structure is completely unresolved. The method is based on the observation that the different polarization components behave collectively like separate entities, with simple relations. The entire Zeeman pattern can then be reduced to just three components, whose dependence on the magnetic field and the temperature can be described by only three numerical parameters. This makes it possible to include the influence of the Zeeman effect directly into ion temperature diagnostic procedures with minimal increase in the required computational effort and without the need for pre-calculated correction factors. We have tabulated such parametrizations-which are accurate for a wide range of fields and temperatures, even for cases when the total line-shape is no longer Gaussian-for 44 commonly studied hydrogen-like transitions. The effects of non-statistical population distribution in the upper sub-levels are briefly discussed, and we also note a temperature-dependent wavelength shift of the centre positions of the transitions.
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| 2. |
- Borges, F O, et al.
(författare)
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Weighted oscillator strengths and lifetimes for the SVII spectrum
- 2004
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Ingår i: Journal of Quantitative Spectroscopy & Radiative Transfer. - 0022-4073. ; 83:3-4, s. 751-763
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Tidskriftsartikel (refereegranskat)abstract
- The weighted oscillator strengths (gf) and the lifetimes presented in this work were carried out in a multiconfiguration Hartree-Fock relativistic approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work, we presented all the experimentally known electric dipole S VII spectral lines.
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| 3. |
- G, Möller, et al.
(författare)
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Lifetime measurements of some low-lying quartet levels in al-like sulphur chlorine and iron
- 1989
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Ingår i: Journal de Physique. Colloques. - : EDP Sciences. - 0449-1947. ; 50:C1, s. 1-602
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Tidskriftsartikel (refereegranskat)abstract
- Lifetimes of some low-lying quartet levels in sulphur, chlorine and iron have been measured using the beam-foil technique. In general, the lifetimes obtained by curve fitting are in agreement with theory. However, the lifetime results for 3s3p(3P)3d 4P04D0 are somewhat higher than predicted, possibly due to the neglection of some of the cascades in the data analysis
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| 4. |
- Giroud, C., et al.
(författare)
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Method for experimental determination of Z dependence of impurity transport on JET
- 2007
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 47:4, s. 313-330
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Tidskriftsartikel (refereegranskat)abstract
- The prediction of impurity peaking in future fusion devices such as ITER necessitates the study of the dependence on Z of the impurity transport in present devices. In this paper we describe a novel technique to determine the transport of impurities with different atomic numbers independently. A technique has been developed that allows simultaneously the measurement of the transport of Ne and Ar in the same discharge while minimizing the systematic errors in the spectroscopic measurements. The reproduction of the charge-exchange measured densities, absolute vaccum ultra-violet line intensities and absolute soft x-ray intensity is achieved in an impurity transport simulation. The method used to estimate the errors on the transport coefficients of neon (Ne) and argon (Ar) is presented. In the plasma region where the diffusion and convection coefficients are determined for hybrid discharges, the transport of Ne and Ar is observed to exceed neoclassical predictions. In the same regions, the diffusion coefficients of both impurities are similar. The convection coefficients are also comparable for Ne and Ar. The peaking of Ne and Ar density profiles are comparable during the period where the intermittent slow reconnecting n = 1 mode is stable in these hybrid discharges.
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| 5. |
- Jupén, Christer, et al.
(författare)
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Additions to the spectra of highly ionized molybdenum, Mo XXIV-Mo XXVIII
- 2003
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Ingår i: Physica Scripta. - 0031-8949. ; 68:4, s. 230-232
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Tidskriftsartikel (refereegranskat)abstract
- We have observed radiation from highly charged molybdenum ions in the JET tokamak plasmas. Spectra were recorded in the wavelength range 70-110 Angstrom, resulting in the classification of 15 new n = 3. Deltan = 0 transitions in Mo XXIV-Mo XXVIII.
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| 6. |
- Jupén, Christer, et al.
(författare)
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Analysis of 3s, 3p, 3d and 4f configurations of Sc XIII and V XV
- 2002
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Ingår i: Physica Scripta. - 0031-8949. ; 66:2, s. 150-158
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Tidskriftsartikel (refereegranskat)abstract
- In spectra obtained from foil-excited and laser-produced plasmas, we have identified 70 new lines as belonging to the spectra of fluorine-like scandium and vanadium ions, Sc XIII and V XV The new lines in the wavelength region from 70 to 600 Angstrom represent 2p(4)3s-3p, 3p-3d and 3d-4f transition arrays. The spectra have been interpreted with the aid of theoretical calculations, and the consistency of our derived 3s, 3p, 3d and 4f energy levels has been checked by means of isoelectronic comparisons.
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| 7. |
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| 8. |
- Jupén, Christer, et al.
(författare)
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The 2p53s, 3p and 3d configurations in neon-like Ti XIII and Fe XVII
- 1984
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Ingår i: Physica Scripta. - 0031-8949. ; 30:2, s. 112-112
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Tidskriftsartikel (refereegranskat)abstract
- Spectra emitted from laser-produced plasmas of scandium, titanium, vanadium and chromium have been recorded in the region 270-600 Å, and lines belonging to the 3s-3p and 3p-3d transition arrays in neonlike ions have been identified. The 2p53s, 3p and 3d energy levels have been derived from the observations for Ti XIII and from solar flare lines for Fe XVII. Hartree-Fock calculations and parametric fits have yielded scaling factors for ab initio energy integrals that make it possible to predicts 3s-3p and 3p-3d wavelengths. Observed and predicted wavelengths for the strongest lines in Sc XII, V XIV, Cr XV and Ni XIX are presented.
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| 9. |
- Jupén, Christer, et al.
(författare)
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The spectrum and term system of SVII
- 2002
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Ingår i: Physica Scripta. - 0031-8949. ; 66:2, s. 140-149
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Tidskriftsartikel (refereegranskat)abstract
- The spectrum of six times ionized sulphur, S VII, has been investigated in the wavelength region 200-4000 Angstrom by means of the beam-foil and laser-produced plasma techniques. The analysis comprises 219 lines of which 105 are newly identified. The present work establishes 123 2s(2)2p(5)nl energy levels of which 66 are new. The level energies are determined with an internal consistency of better than 20 cm(-1). The observed level structure has been investigated by means of parametric calculations. The center-of-gravity ionization energy of the 2s(2)2p(5 2)P limit has been determined to 2 269 410 +/- 60 cm(-1). Of the identified 3s-3p and 3p-3d lines 27 are present in the solar coronal spectrum recorded by the SUMER instrument onboard the SOHO satellite. The present work adds 2 new solar identifications and improved wavelengths of some other solar coronal lines.
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| 10. |
- Martinson, Indrek, et al.
(författare)
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Atomic structure studies using fusion plasmas
- 2003
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Ingår i: Physica Scripta. - 0031-8949. ; 68:6, s. 123-132
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Forskningsöversikt (refereegranskat)abstract
- Atomic spectroscopy plays an important role in fusion research and extensive knowledge of atomic parameters is needed for plasma diagnostics. However, a magnetically confined hot plasma can be considered as a spectroscopic fight source which has some unique properties, including high temperature and low density. Fusion devices can therefore be used to tackle problems in basic atomic physics. This paper reviews the contributions to the structure of atomic ions, which have been obtained by the spectroscopy of fusion plasmas. Studies of highly charged ions, forbidden transitions, QED effects and connections between solar physics and fusion plasma physics will be discussed.
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| 11. |
- Mattioli, M, et al.
(författare)
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Experimental and simulated M-shell nickel spectra in the 14.4-18.0 nm region from magnetic fusion devices
- 2004
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:1, s. 13-40
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Tidskriftsartikel (refereegranskat)abstract
- Experimental M-shell nickel spectra in the 14.4-16.5 nm region from the JET tokamak (from both divertor and limiter configurations) and from the reversed field pinch RFX have been simulated. These spectra include lines from five ionization states, namely from K-like N-i9+ to P-like Ni13+ ions. For the JET limiter configuration the spectrum upper wavelength limit was higher (18.0 nm) and lines from Si-like Ni14+ ions were also observed. Collisional-radiative (CR) models have been built for these six Ni ions, considering electron collisional excitation and radiative decay as the main populating processes for the excited states. These models give photon emission coefficients (PECs) for the emitted tines at electron density (n(e)) and temperature (T-e) values corresponding to the experimental situations. Impurity modelling is performed using a 1D impurity transport code, calculating the steady state radial distribution of the Ni ions. The Ni line brightnesses are evaluated in a post-processing subroutine and simulated spectra are obtained. The spectrum from a single ion, in the absence of blendings, depends only on the T-e and n(e) values in the emitting shell of the ionization state considered. On the other hand, the superposition of these spectra depends on the experimental conditions, as a consequence of the fact that the ion charge distribution depends not only on the radial profiles of T-e and n(e) but also on the chosen ionization and recombination rate coefficients and on the radial profiles of the impurity transport coefficients in the region of the emitting shells. Since the aim of the paper is the investigation of the atomic physics of the M-shell ions, the section discussing the plasma physics phenomena is purposely limited. For each experimental spectrum a few simulations are presented, since a unique choice has not been found by selecting the input parameters of the transport code. The effect of the T-e and n(e) values on the emitting shells as well as the influence of line blendings on the single-ionization-degree spectra are stressed. These, in turn, are then compared with the predictions. For the n(e) range considered the PECs are practically independent of n(e). The T-e dependence is much reduced due to the fact that the spectral fits performed are actually comparisons of line ratios. The agreement found between experimental and simulated single-ionization-degree spectra gives confidence in the atomic data used in the CR models.
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| 12. |
- Pagan, C. J. B., et al.
(författare)
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Wavelengths, Energy Levels, Lifetimes, and Weighted Oscillator Strengths for the S VIII Spectrum
- 2011
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Ingår i: The Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 196:2
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Tidskriftsartikel (refereegranskat)abstract
- The weighted oscillator strengths (gf) and lifetimes for S VIII presented in this work were obtained by a multiconfigurational Hartree-Fock relativistic approach. In this calculation, the electrostatic energy parameters were optimized by a least-squares procedure in order to improve the adjustment to experimental energy levels. The values for gf and lifetimes were then calculated on the basis of these adjusted parameters. New classifications are proposed for energy levels belonging to the 4s and 4d configurations and lines related to them.
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| 13. |
- von Hellermann, M G, et al.
(författare)
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Complex spectra in fusion plasmas
- 2005
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Ingår i: Physica Scripta. - 0031-8949. ; T120, s. 19-29
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Tidskriftsartikel (refereegranskat)abstract
- The need for quantitative evaluation of complex line emission spectra as observed in hot fusion plasmas initiated a challenging development of sophisticated interpretation tools based on integrating advanced atomic modelling with detailed treatment of the plasma environment. The successful merging of the two worlds has led to routine diagnostic procedures which have contributed enormously to the understanding of underlying plasma processes and also to a wide acceptance of spectroscopy as a reliable diagnostic method. In this paper three characteristic types of spectra of current and continuing interest are presented. The first is that of medium/ heavy species with many ionisation stages revealed in survey VUV and XUV spectra. Such species occur as control gases, as wall materials, as ablated heavy species and possible as layered wall dopants for monitoring erosion. The spectra are complex with line- like and quasi-continuum regions and are amenable to advanced 'pattern recognition' methods. The second type is of few electron, highly ionised systems observed as line-of-sight integrated passive emission spectra in the soft X-ray region. They are analysed successfully in terms of plasma parameters through matching of observation with predicted synthetic spectra. Examples used here include highly resolved helium-like emission spectra of argon, iron and titanium observed on the tokamaks TEXTOR and Tore Supra. The third type, and the emphasis of this work, comprises spectra linked to active beam spectroscopy, that is, charge exchange recombination spectroscopy (CXRS) and beam emission spectroscopy ( BES). In this case, a complex spectrum is again composed of a ( usually) dominating active spectrum and an underlying passive emission spectrum. Its analysis requires modelling of both active and passive features. Examples used here are from the CXRS diagnostic at JET and TEXTOR. They display characteristic features of the main light impurity ions (C+6, He+2, N+7, Ne+10 and Ar+18), as well as that of the bulk plasma ions, H+, D+ and T+. A main conclusion is that spectral complexity is not necessarily negative, but that 'complex structures' can provide a rich source of information on the plasma and its parameters - provided it is matched with integrated analysis - and that the methods can have universal applicability. In the present preparatory phase of the next generation fusion experiment ITER ( International Thermonuclear Experimental Reactor) the concepts and expectations of complex spectra and integrated data analysis play an important role in the design and optimisation procedure of the ITER diagnostic assembly.
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