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13 results on '"Dickheuer, Sven"'

3. The Balmer lines emission of fast hydrogen atoms at the plasma-solid interface in a low density plasma

Author

Dickheuer, Sven Oliver (M. Sc.)

Subjects
Plasmadiagnostik, Zeeman-Effekt, ddc:530, Emissionsspektroskopie, Balmer-Linie, Polarisiertes Licht
Abstract

Die starke Verbreiterung von Balmerlinien in H oder H-Mischplasmen ist ein intensiv und vielfach untersuchtes Phänomen in der Plasmaphysik. In Laborplasmen werden sowohl die Quelle der schnellen H Atome vor der Oberfläche als auch der Ursprung der beobachteten Emission kontrovers diskutiert. Durch Messungen in einem ArH Mischplasma konnte gezeigt werden, dass die Anregungsquelle von H bei der Wechselwirkung mit Ar unter den genutzten Bedingungen in Niederdruckplasmen auf nur zwei mögliche atomare Prozesse eingegrenzt werden kann: Grundzustandanregung oder Anregung über metastabile Zustände. Durch Variation des Oberflächenmaterials konnte gezeigt werden, dass die Quelle der dopplerverschobenen Emission nur an der Oberfläche zurückgestreute Atome sind. Aus der blau- und rotverschobenen Komponente der Emission werden sowohl die spektrale Reflektion der Oberfläche als auch die Polarisationseigenschaften des Materials während der Plasmaexposition in situ bestimmt.

Published
2020

4. The Balmer lines emission of fast hydrogen atoms at the plasma-solid interface in a low density plasma: challenges and applications

Author

Dickheuer, Sven Oliver

Subjects
Physics::Plasma Physics, 530 Physik
Abstract

The wide broadening of Lyman and Balmer lines in H or H mixed plasmas is a widelyobserved and studied phenomena in many kinds of different plasmas, ranging fromstellar to laboratory plasmas. The source of the fast H atoms in front of the surface aswell as the origin of the observed emission in laboratory plasmas is under controversialdiscussion. A. V. Phelps proposes a "sheath-collision" model in which H$^{+}$, H$^{+}_{2}$ and H$^{+}_{3}$ ions are accelerated in the sheath and create fast H atoms by charge transferor dissociation interaction with gas or the metallic surface. There are a number ofexperiments trying to explain the broadening of the lines, but the community couldonly agree on the fact that the broadening is caused by the Doppler effect. Usually experiments in this field are performed in high pressure plasmas (p $\geq$ 1 Pa), but this makes it very difficult to analyze the Doppler-shifted emission due to the following reasons. On the one hand, the high pressure leads to emission of accelerated ions and backscattered atoms which makes the detected signal a superposition of both effects. On the other hand, the emission of ions inside the Debye sheath leads to a Stark broadening of the emitted lines and makes the analysis of the emission spectra complicated. [...]

Published
2020

6. Emission of Fast Hydrogen Atoms in a Low Density Gas Discharge—The Most “Natural” Mirror Laboratory

Author

Marchuk, Oleksandr, primary, Dickheuer, Sven, additional, Ertmer, Stephan, additional, Krasikov, Yuri, additional, Mertens, Philippe, additional, Brandt, Christian, additional, Brezinsek, Sebastijan, additional, Goriaev, Andrei, additional, Ialovega, Mykola, additional, Göths, Beatrix, additional, Kreter, Arkadi, additional, and Linsmeier, Christian, additional

Published
2019
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10. In situ measurements of the spectral reflectance of metallic mirrors at the Hα line in a low density Ar–H plasma

Author

Dickheuer, Sven, primary, Marchuk, Oleksandr, additional, Brandt, Christian, additional, Pospieszczyk, Albrecht, additional, Goriaev, Andrei, additional, Ialovega, Mykola, additional, Göths, Beatrix, additional, Krasikov, Yuri, additional, Krimmer, Andreas, additional, Mertens, Philippe, additional, and Kreter, Arkadi, additional

Published
2018
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12. <italic>In situ</italic> measurements of the spectral reflectance of metallic mirrors at the <italic>H</italic><italic>α</italic> line in a low density Ar–H plasma.

Author

Dickheuer, Sven, Marchuk, Oleksandr, Brandt, Christian, Pospieszczyk, Albrecht, Goriaev, Andrei, Ialovega, Mykola, Göths, Beatrix, Krasikov, Yuri, Krimmer, Andreas, Mertens, Philippe, and Kreter, Arkadi

Subjects
*SPECTRAL reflectance measurement, *PLASMA devices, *FAST ion-atom collisions, *HYDROGEN atom, *MAGNETICS
Abstract

The efficient and reliable control and monitoring of the quality of the optical properties of mirrors is an open problem in laboratory plasmas. Until now, the measurement of the reflectance of the first mirrors was based on the methods that require additional light calibration sources. We propose a new technique based on the ratio of the red- and blue-shifted emission signals of the reflected hydrogen atoms which enables the in situ measurement of the spectral reflectance of metallic mirrors in low-density Ar–H or Ar–D plasmas. The spectral reflectance coefficients were measured for C, Al, Ag, Fe, Pd, Ti, Sn, Rh, Mo, and W mirrors installed in the linear magnetized plasma device PSI-2 operating in the pressure range of 0.01-0.1 Pa. The results are obtained for the Hα line using the emission of fast atoms induced by excitation of H atoms through Ar at a plasma-solid interface by applying a negative potential U = −80, …, −220 V to the mirror. The agreement between the measured and theoretical data of reflectance is found to be within 10% for the investigated materials (except for C). The spectra also allow us to efficiently determine the material of the mirror. [ABSTRACT FROM AUTHOR]

Published
2018
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13. In situ measurements of the spectral reflectance of metallic mirrors at the H α line in a low density Ar-H plasma.

Author

Dickheuer S, Marchuk O, Brandt C, Pospieszczyk A, Goriaev A, Ialovega M, Göths B, Krasikov Y, Krimmer A, Mertens P, and Kreter A

Abstract

The efficient and reliable control and monitoring of the quality of the optical properties of mirrors is an open problem in laboratory plasmas. Until now, the measurement of the reflectance of the first mirrors was based on the methods that require additional light calibration sources. We propose a new technique based on the ratio of the red- and blue-shifted emission signals of the reflected hydrogen atoms which enables the in situ measurement of the spectral reflectance of metallic mirrors in low-density Ar-H or Ar-D plasmas. The spectral reflectance coefficients were measured for C, Al, Ag, Fe, Pd, Ti, Sn, Rh, Mo, and W mirrors installed in the linear magnetized plasma device PSI-2 operating in the pressure range of 0.01-0.1 Pa. The results are obtained for the H α line using the emission of fast atoms induced by excitation of H atoms through Ar at a plasma-solid interface by applying a negative potential U = -80, …, -220 V to the mirror. The agreement between the measured and theoretical data of reflectance is found to be within 10% for the investigated materials (except for C). The spectra also allow us to efficiently determine the material of the mirror.

Published
2018
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