A spectral line shape analysis of motional stark effect spectra

12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France)Recent observations of MSE spectra carried out on Tore-Supra show discrepancies between experimental and theoretical intensities calculated at equilibrium. We present here a kinetic model, based on the selectivity of excitation cross sections of Stark states in the parabolic basis. Redistribution due to ion-atom collisions among Stark states of level n=3 allow to calculate the population of Stark states. This model permits to improve significantly the agreement between measured and calculated MSE spectra

Spectral Line Shapes as a Diagnostic Tool in Magnetic Fusion

Spectral line shapes and intensities are used for obtaining information on the various regions of magnetic fusion devices. Emission from low principal quantum numbers of hydrogen isotopes is analyzed for understanding the complex recycling mechanism. Lines emitted from high principal quantum numbers of hydrogen and helium are dominated by Stark effect, allowing an electronic density diagnostic in the divertor. Intensities of lines emitted by impurities are fitted for a better knowledge of ion transport in the confined plasma

Stark broadening of high-members of the helium diffuse series in divertor plasmas

International audienceStark profiles of high-members (n≥7) of the helium triplet diffuse series 1s2p 3 P @BULLET −1snd 3 D are calculated for tokamak divertor conditions using dipole reduced matrix elements obtained with a hydrogenic approximation. It is shown that the socalled " standard model " of Stark broadening is particularly suited to the description of the isolated lines 1s2p 3 P @BULLET − 1snd 3 D with n = 8 − 10. Applications to spectroscopic diagnostics in existing and future magnetic fusion-oriented devices like ITER are discussed

Doppler spectral line shapes and apparent velocity distribution in plasmas affected by low-frequency turbulence

Starting from first principles, we derive for the first time a comprehensive formalism allowing to calculate Doppler spectral line shapes emitted in plasmas affected by low-frequency turbulence. The apparent velocity distribution function (VDF) of the emitters in a turbulent plasma, deduced from spectral line analysis, is expressed in terms of the joint probability density function (PDF) of the fluctuating plasma fields. In the case where temperature fluctuations are dominant, we use analytic expressions for the PDF, allowing theoretical predictions for the apparent VDF. We show that temperature PDFs behaving asymptotically as a power law lead to a similar behaviour for the Doppler line wings

Stark broadening of hydrogen lines in low-density magnetized plasmas

Stark broadening of hydrogen lines in the presence of a magnetic field is revisited, with emphasis on the role of the ion component under typical conditions of magnetized fusion devices. An impact theory for ions valid at low density (N-e less than or similar to 10(14) cm(-3)) and taking into account the Zeeman degeneracy removal of the atomic states is developed. It is shown that the Stark widths of the Lorentz triplet components strongly depend on the magnetic field. The model is validated by a computer simulation method. For the lateral sigma components of Ly alpha, we show that the impact approximation still holds for densities as high as N-e similar to 10(15) cm(-3). In contrast, for the central pi component as well as for the other lines from low principal quantum number, significant discrepancies between the proposed theory and the simulation results appear at high density. Application to D alpha in tokamak divertor plasma conditions shows that, in this case, the quasistatic approximation becomes more relevant

Spectral line shapes modeling in turbulent plasmas

In this work we investigate the influence of low frequency turbulence on Doppler spectral line shapes in magnetized plasmas. Low frequency refers here to fluctuations whose typical time scale is much larger than those characterizing the atomic processes, such as radiative decay, collisions and charge exchange. This ordering is in particular relevant for drift wave turbulence, ubiquitous in edge plasmas of fusion devices. Turbulent fluctuations are found to affect line shapes through both the spatial and time averages introduced by the measurement process. The profile is expressed in terms of the fluid fields describing the plasma. Assuming the spectrometer acquisition time to be much larger than the turbulent time scale, an ordering generally fulfilled in experiments, allows to develop a statistical formalism. We proceed by successively investigating the effects of density, fluid velocity and temperature fluctuations on the Doppler profile of a spectral line emitted by a charge exchange population of neutrals. Line shapes, and especially line wings are found to be affected by ion temperature or fluid velocity fluctuations, and can in some cases exhibit a power-law behavior. These effects are shown to be measurable with existing techniques, and their interpretation in each particular case would rely on already existing tools. From a fundamental point of view, this study gives some insights in the appearance of non-Boltzmann statistics, such as Lévy statistics, when dealing with averaged experimental data

Diagnostics of JT-60U divertor plasmas by Stark-Doppler broadening of carbon spectral lines

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Plasma spectroscopy in the conditions of the ITER tokamak

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