Behavior Of Spectral Lines Research Articles

Target heating and plasma dynamics during hot magnetron sputtering of Nb

In this work, the direct current (DC) hot magnetron sputtering (HMS) of Nb has been studied and compared with the conventional cold magnetron sputtering (CMS) discharge. Particularly, these two magnetron systems were investigated in terms of current–voltage trends, behaviour of spectral lines, target temperature, and deposition rate. The current–voltage evolution showing strong variations over time in the HMS system was used to monitor the moment when thermionic emission becomes considerable. Meanwhile, thanks to the time-resolved optical emission spectroscopy (OES), the dynamics of plasma particles and the population of their electronic levels were analysed as a function of the target temperature. The target temperature was measured owing to both pyrometry and OES-based approach, i.e. by fitting an emission spectrum baseline. Finally, in the HMS configuration used in this work, the deposition rate up to 100 nm min−1 was obtained at the applied power density of 30 W cm−2, which is three times higher than the maximum power density applicable to the classical CMS system. However, with further increase in the power density, the deposition rate values were found to be saturated, which is likely caused by a significant increment in a number of thermal electrons in the discharge area.

MANTIS: A real-time quantitative multispectral imaging system for fusion plasmas.

This work presents a novel, real-time capable, 10-channel Multispectral Advanced Narrowband Tokamak Imaging System installed on the TCV tokamak, MANTIS. Software and hardware requirements are presented together with the complete system architecture. The image quality of the system is assessed with emphasis on effects resulting from the narrowband interference filters. Some filters are found to create internal reflection images that are correlated with the filters' reflection coefficient. This was measured for selected filters where significant absorption (up to 65% within ∼70 nm of the filter center) was measured. The majority of this was attributed to the filter's design, and several filters' performance is compared. Tailored real-time algorithms exploiting the system's capabilities are presented together with benchmarks comparing polling and event based synchronization. The real-time performance is demonstrated with a density ramp discharge performed on TCV. The behavior of spectral lines' emission from different plasma species and their interpretation are qualitatively described.

Non-LTE line formation of Fe in late-type stars – IV. Modelling of the solar centre-to-limb variation in 3D

Our ability to model the shapes and strengths of iron lines in the solar spectrum is a critical test of the accuracy of the solar iron abundance, which sets the absolute zero-point of all stellar metallicities. We use an extensive 463-level Fe atom with new photoionisation cross-sections for FeI as well as quantum mechanical calculations of collisional excitation and charge transfer with neutral hydrogen; the latter effectively remove a free parameter that has hampered all previous line formation studies of Fe in non-local thermodynamic equilibrium (NLTE). For the first time, we use realistic 3D NLTE calculations of Fe for a quantitative comparison to solar observations. We confront our theoretical line profiles with observations taken at different viewing angles across the solar disk with the Swedish 1-m Solar Telescope. We find that 3D modelling well reproduces the observed centre-to-limb behaviour of spectral lines overall, but highlight aspects that may require further work, especially cross-sections for inelastic collisions with electrons. Our inferred solar iron abundance is log(eps(Fe))=7.48+-0.04.

Shielding effects in the laser-generated copper plasma under reduced pressures of He atmosphere

Irradiation of samples was performed with 6ns, 1064nm Nd:YAG laser. For an applied irradiance range (108–1010W/cm2), the ablation process exhibits non-linear dependance. Ablated mass of the sample was directly determined using 100ng resolution mass comparator after ablation under various pressures of helium. The ablation rates were dictated by plasma formation mechanisms as well as ambient conditions. However, the surrounding atmosphere did not significantly affect the value of threshold irradiance of about 2 ×109W/cm2 for the onset of ablation mechanism change. This value is additionally verified via spectroscopic information from Cu I lines in the range from 0.4 to 1μs after the laser pulse. Behaviour of spectral lines was monitored with respect to the laser pulse energy. Plasma diagnostics of axial electron density and excitation temperature distributions was performed under He pressure of 200Torr. An influence of the possible shielding mechanisms responsible for the plasma absorption is discussed.

Behavior of spectral lines and degree of spatial coherence in the presence of refraction.

The propagation of radiation from a source embedded in an inhomogeneous refractive medium is studied, using both mode-analysis and ray-tracing methods. Scaling laws for excitation strengths of the modes, the degree of spatial coherence, and the shift of the spectral line are derived.

Variable flux of P Cygni in continuum and spectral lines

Recently, cyclic variations have been discovered both photometrically in the continuum flux of P Cygni (Percy et al. 1988) and by position measurements of different components in spectral lines of this star (Kolka 1983, Markova, Kolka 1985, Lamers et al. 1985). Additionally, more stochastic polarimetric (Haves 1985) and radio flux (van den Oord et al. 1985) variations were discovered, too. It has recurrently been stressed that simultaneous multiwavelength observations are badly needed. Fortunately, we had a possibility to complement our own observational data from 1982 with some additional data of the same year from astronomical literature to compare the B, V-filter flux with the behavior of spectral lines having two flux estimates for this period, too.

A Modified Version of the Grimm's Glow Discharge Lamp for Use as a Demountable Hollow Cathode Emission Source. IV. Further Data on the Behavior of Blackening Curves for Copper

Abstract The blackening behavior of spectral lines emitted by a hollow cathode in the case of copper was further investigated at closer gas pressure intervals (259, 289, 314, 342, 375 and 416 Pa) and electrode distances (15.0, 17.5, 20.0, 22.5, 25.0, 27.5, 30.0, and 33.0 mm). Results show that a pressure range from 300 to 380 Pa can be considered a transition region in which the electrode distance corresponding to blackening maximum shifts progressively from 20 to 33 mm. These data agree with previous findings on the dependene of photographic blackening of copper spectral lines on electrode distance.

The Behavior of Spectral Lines at the Positive Pole of the Metallic Arc

The Behavior of Spectral Lines at the Positive Pole of the Metallic Arc