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Doppler broadening

About: Doppler broadening is a research topic. Over the lifetime, 5509 publications have been published within this topic receiving 92552 citations.


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TL;DR: In this paper, the morphology changes induced by low energy deuterium ions on tungsten surfaces are studied for particle fluxes similar to those expected in the ITER divertor, as high as 1024 m−2 s−1.

36 citations

Journal ArticleDOI
TL;DR: In this paper, the authors performed laser absorption experiments on atmospheric microwave induced argon plasmas produced by the 'Torche a Injection Axiale' in order to study the 4s 3P2 metastable densities and deduce plasma properties.
Abstract: Diode laser absorption experiments have been performed on atmospheric microwave induced argon plasmas produced by the `Torche a Injection Axiale' in order to study the 4s 3P2 metastable densities and deduce plasma properties. It is found that the density is maximal in the active plasma zone (~1.5×1018 m−3) and rapidly decreases in the recombining plasma zone. In strongly ionizing atmospheric plasmas the 4s population can be used to estimate the electron temperature. The obtained value (1.3 eV) is considerably lower than the temperature found with Thomson scattering in a previous study (~2.0 eV). The very strong scattering of the laser spot on the plasma in the expansion zone just above the nozzle suggests that in this region the plasma is filamentary. Above this zone lateral measurements have been Abel-inverted. Hollow profiles, like those determined for the electron density in previous studies, have not been observed for the 4s distribution. It is found that the plasma zone with high 4s density is extended further downstream with increasing gas flow whereas the introduction of typically a few per cent of CO2 already results in a significant quenching of the metastables. The width of the absorption profile varies from typically 10 GHz in the active zone, where Van der Waals broadening is dominant, to 4 GHz in the recombining zone, where Doppler broadening becomes significant. The position of the central absorption frequency is found to be dependent on among other things the position in the plasma. If this shift is attributed to the Stark effect it is obtained that the maximum electron density is within (2–4)×1021 m−3. Since this latter value is rather high, it must be concluded that the Van der Waals effect induces a shift as well. The width and shift have been used to study trends in plasma properties (i.e. gas temperature and electron density) as a function of various parameters (i.e. position in the plasma, gas flow and gas composition). The observed tendencies are in agreement with findings in previous studies.

36 citations

Journal ArticleDOI
TL;DR: In this article, a single running mode in a ring gas laser where inhomogenous Doppler broadening is dominant is considered, and the analytic linear stability analysis of the stationary solution leads to the conclusion that in the bad cavity limit a second threshold exists.

36 citations

Journal ArticleDOI
TL;DR: In this paper, a two-state model with five vibrational and one torsional degree of freedom was proposed to analyze the spectral broadening of anthracene and 9,9' -bianthryl spectra.
Abstract: Optical fluorescence spectra of anthracene (AN) and of 9,9’‐bianthryl (BA) have been measured in the apolar solvent 2‐methyl‐butane (2MB) at seven different temperatures in the range 123 K to 298 K. The AN spectra are strongly structured and consist of simple Franck–Condon (FC) progressions. The BA spectra on the other hand are broad and show unusual temperature dependencies. These effects are interpreted within a two state model with five vibrational and one torsional degree of freedom. A FC analysis is carried out using vibronic band shape functions which are convolutions of two functions. The first one is a Gaussian representing the spectral broadening due to librations and intermolecular interactions. The second one results from a semiclassical treatment of the intramolecular torsional mode (large amplitude motion, LAM). Optical transitions are assumed to occur from ensembles which are thermally equilibrated with respect to their nuclear degrees of freedom. The Boltzmann distribution with respect to the LAM potentials in combination with a change of the transition frequency as a function of the torsional angle φ is identified as the predominant broadening mechanism. The LAM potentials in the S0 and S1 state are represented by a three parameter cosine series. A nonlinear least‐squares fit of the experimental spectra leads to a single consistent set of model parameters valid for all temperatures. The S1 double minimum LAM potential of BA in 2MB is found to have minima at φeq=62° (and 118°) and a local barrier at φ=90° of 255 cm−1.

36 citations

Journal ArticleDOI
TL;DR: In this article, the power deposition profiles during minority ion cyclotron heating are analyzed in large tokamaks by using the global toroidal wave code LION and a heuristic formula is given.
Abstract: The power deposition profiles during minority ion cyclotron heating are analysed in large tokamaks by using the global, toroidal wave code LION. For tokamaks with large aspect ratio and with circular cross-section, the wave is focused on the magnetic axis and can be absorbed there by cyclotron absorption when the cyclotron resonance passes through the magnetic axis. The power deposition profile is then essentially determined by the Doppler broadening of the ion cyclotron resonance. For equilibria either non-circular or with a small aspect ratio the power deposition profile depends also on the strength of the damping. In this case the power deposition profile can be expressed as a sum of two power deposition profiles. One is related to the power absorbed in a single pass, and its shape is similar to that obtained for large aspect ratio and circular cross-section. The other profile is obtained by calculating the power deposition in the limit of weak damping, in which case the wave electric field is almost constant along the cyclotron resonance layer. A heuristic formula for the power deposition is given. The formula includes a number of calibration curves and functions which has been calculated with the LION code for JET relevant equilibria. The formula enables calculation of the power deposition profile in a simple way when the launched wave spectrum and damping coefficients are known.

36 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202331
202290
2021122
2020134
2019128
2018122