Measurements of the energy distribution of W atoms sputtered by low energy Ar ions using high-resolution Doppler spectroscopy

Ertmer, S.; Marchuk, O.; Dickheuer, S.; Brezinsek, S.; Boerner, P.; Schmitz, J.; Kreter, A.

doi:10.1088/1361-6587/abc519

Cited by 6 publications

(7 citation statements)

References 21 publications

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“…is shown in blue, the counter-clockwise polarization measured at the angle of −45 • in orange and the measurements of both polarization in green (0 • ). In the latter case the observed line-shape is identical to the measurements without the quarter wave plate since both components pass the polarizer with the same intensity [6]. A cubic interpolation of the data is also shown using the same color to guide the eye.…”

Section: Methodssupporting

confidence: 56%

“…This is caused by population processes of the excited atomic levels via electron impact excitation in the plasma and the lifetime of this level. The impact of the Langmuir-Debye-sheath and the impact of ionization on the emission of the sputtered atoms on the spatial development can be neglected here [6]. The non-isotropic angular distribution of sputtered atoms lead to lower loss rate emission in comparison with 1/r 2 dependence, see also [16].…”

Section: Methodsmentioning

confidence: 99%

“…Moreover, the perturbation of spectral lines caused by a magnetic eld is crucial for determination of other parameters. So, for instance, the measurements of energy distribution of sputtered atoms performed recently in linear plasma [5,6] required the value of the magnetic eld to be taken elsewhere. In this paper we demonstrate how the optical isolation of spectral lines could be ef ciently applied to determine the magnetic eld using the spectra of sputtered atoms at plasma-solid interface, relevant in many kinds of laboratory plasmas such as magnetrons or the glow discharges.…”

Section: Introductionmentioning

confidence: 99%

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Optical isolation of spectral lines emitted by sputtered tungsten in a weakly magnetized plasma

Ertmer¹,

Marchuk²,

Kreter³

et al. 2020

J. Phys. B: At. Mol. Opt. Phys.

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Optical isolation of the clockwise or the counter-clockwise circular polarization of spectral lines was applied to emission of sputtered tungsten atoms. As a result one measures the weak magnetic field at plasma-surface interface resulting in splitting of spectral lines (W I at 4008.751 Å and 4982.593 Å) being negligibly small with respect to the Doppler broadening. One relies only on the phase rotation of a reflected circular polarized light propagating at the normal incidence to the mirror-like surface. The spectral shift of the signal from sputtered W atoms on the detector using high-resolution spectrometer provides the value of the magnetic field at a known dispersion, i.e. no further modeling or additional assumption on the distribution of atoms is required. The isolation of spectral line components is equivalent to isolation of the effect of the magnetic field from the measured line shape. It is complete for Zeeman triplet lines and partial for other lines. The results are found to be in a very good agreement of 3% with calculations and the Zeeman resolved laser absorption spectroscopy (10%) on metastable levels of Ar I atoms.

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Section: Methodssupporting

confidence: 56%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical isolation of spectral lines emitted by sputtered tungsten in a weakly magnetized plasma

Ertmer¹,

Marchuk²,

Kreter³

et al. 2020

J. Phys. B: At. Mol. Opt. Phys.

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“…At linear plasma devices, such as PSI-2, or in magnetron sputtering discharges, high-resolution emission spectroscopy, laser absorption spectroscopy and laser-induced fluorescence resolve the shape of the radiative transitions by sputtered atoms [26][27][28][29]. Also, the measurements of polarization properties of metallic mirrors using emission properties of the backscattered atoms rely on the theoretical description of the measured line shapes [30].…”

Section: Introductionmentioning

confidence: 99%

Space-resolved line shape model for sputtered atoms of finite-size targets

Sackers,

Marchuk,

Ertmer

et al. 2023

Phys. Scr.

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High-resolution emission spectroscopy provides valuable information on the physical sputtering process during plasma-wall interaction. Up to now, analyzing the observed spectral lines during sputtering did not account for the finite size of the targets. It becomes crucial if the size of the target becomes comparable with the distance the sputtered atoms travel before emitting the photons. So, for example, the generally used standard emission model based on an infinite target or the point source approximation breaks for observations using two lines of sight: parallel and perpendicular to the normal of the target. It is impossible to achieve consistent results for energy and angular distribution of sputtered atoms. The new space-resolved emission model for finite-size targets developed in this work removes this gap. It incorporates the space-velocity transformation for the distribution function and includes the finite lifetime of excited states. The model was validated using emission spectra of sputtered atoms from a polycrystalline tungsten sample bombarded by monoenergetic Ar+ with kinetic energies of 100 eV to 140 eV at normal incidence in the linear plasma device PSI-2. Using the new model enables the simultaneous fitting of the line shapes of sputtered tungsten for both observation angles. The optimization process is performed using the standard Thompson distribution by separating the energy-dependent parameter and the angular distribution.

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“…However, to emulate the conditions at fusion experiments (ion fluxes, ion energy, etc) the plasma in these dedicated devices is confined by a magnetic field. This poses a challenge for the investigations since now also the Zeeman effect has to be considered in the analysis of the emission profile [17]. For low magnetic field strengths the Zeeman splitting of the absorption lines is much less than the thermal (Doppler) broadening.…”

Section: Introductionmentioning

confidence: 99%

Zeeman-resolved TDLAS using metastable levels of Ar in the weakly magnetized plasma of the linear plasma device PSI-2

Sackers¹,

Marchuk²,

Ertmer³

et al. 2021

J. Phys. D: Appl. Phys.

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Tunable diode laser absorption spectroscopy was applied at the linear plasma device PSI-2 to measure the magnetic field, temperature of argon and density of metastable species in a low density gas discharge. The measurements on the two metastable levels of Ar were performed by scanning the plasma column of PSI-2 at different radii. The obtained magnetic field using the lines at 763 and 772 nm (Ar) was found to be systematically lower (by 5% to 17%) than the calculated vacuum field. Part of the deviation arises from the line integration of the absorption signal. The radial gradient of the magnetic field strength combined with the radial metastable density determines the magnitude of this contribution (2%-3%). The temperature of the neutral gas was found to be essentially constant within the discharge chamber. The gas temperature rises with increasing cathode current and magnetic field due to an increase in the plasma density and, consequently, an increase in the energy transferred to the neutral gas by collisions with the charged particles. The density of the 4 s metastable level with J = 2 was found to be 8-9 times higher than that of the level with J = 0 similarly to observations by others in non-magnetized plasmas. To understand this trend a simple collisional-radiative model for the metastable argon 4s J = 2 level was developed. Depending on the treatment of the 4p levels it predicts a lower and an upper limit of the metastable density. The experimental values are within the limits predicted by the model indicating that the complex kinetics of the excitation and deexcitation collisional-radiative processes lead to this deviation from the statistical equilibrium.

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Measurements of the energy distribution of W atoms sputtered by low energy Ar ions using high-resolution Doppler spectroscopy

Cited by 6 publications

References 21 publications

Optical isolation of spectral lines emitted by sputtered tungsten in a weakly magnetized plasma

Optical isolation of spectral lines emitted by sputtered tungsten in a weakly magnetized plasma

Space-resolved line shape model for sputtered atoms of finite-size targets

Zeeman-resolved TDLAS using metastable levels of Ar in the weakly magnetized plasma of the linear plasma device PSI-2

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