Anomalous Diffusion in a Linear Plasma Generator

Waldmann, O.; Meyer, H.; Fußmann, G.

doi:10.1002/ctpp.200710079

Cited by 20 publications

(17 citation statements)

References 21 publications

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“…which follows from an analytical treatment assuming anomalous diffusion and a shell like plasma source at r = r 0 (see [10]) and with r = |x|. Here k and n e (r 0 ) are fitting parameters and I 0 and K 0 are the modified Bessel functions.…”

Section: Density Profiles In Psi-2mentioning

confidence: 99%

“…Different working gases can be blown into the discharge region where a plasma is produced between a heated, hollow, cylindrical LaB 6 -cathode and a cylindrically-shaped Mo-anode. The geometry of the discharge region results in a hollow profile in electron density and temperature ( [9], [10]). Guided by an axial magnetic field the plasma streams with a typical cross-section of 80 mm through a differential pumping system and a so called target chamber and is terminated at the neutralizer plate (cf.…”

Section: Experimental Set-upmentioning

confidence: 99%

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Influence of the Langmuir Probe Shaft on Measuring Plasma Parameters

Waldmann

Fußmann

2008

Contrib. Plasma Phys.

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Because of their good spatial and temporal resolution Langmuir probes are often used for plasma diagnostics. One has to keep in mind, however, that the presence of the probe can substantially perturb the neighboring plasma. Apart from the probe tip, in particular the probe shaft may affect the measured values of temperature and density. We have studied this latter effect at the linear plasma generator PSI-2 which provides a stationary plasma column of 2.6 m in length and 8 cm in diameter. Two single probes differently arranged were used in these experiments. In the first case the probes were in the same plane but tilted to each other in azimuthal direction. In the second arrangement the probes were separated by a distance along the magnetic field lines at the same azimuthal angle. One probe was kept at a fixed (but variable) position while the other was scanning the plasma radially. It is found that the electron temperature is hardly influenced by the presence of the second probe, but the electron density is decreased up to 30%. The results can approximately be described in the frame of a global particle model treating the probe shafts as additional plasma sinks. Most striking is the observation that large global reductions of the density are accompanied by only moderate local changes. This means that the perturbations caused by the probe are characterized by a large scale effect, possibly indicating anomalous diffusion.

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Section: Density Profiles In Psi-2mentioning

confidence: 99%

Section: Experimental Set-upmentioning

confidence: 99%

Influence of the Langmuir Probe Shaft on Measuring Plasma Parameters

Waldmann

Fußmann

2008

Contrib. Plasma Phys.

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“…emission lines. Slightly different profiles of the D α line in (a,c) are attributed to the projection of poloidal rotation velocity of the ions on different lines-of-sight [13]. The measured profiles of D α and D β lines are used to derive the ion temperature of the plasma.…”

Section: Methodsmentioning

confidence: 99%

Emission of fast non-Maxwellian hydrogen atoms in low-density laboratory plasma

Brandt

Marchuk

Pospieszczyk

et al. 2017

AIP Conference Proceedings

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Abstract. The source of strong and broad emission of the Balmer-α line in mixed plasmas of hydrogen (or deuterium) and noble gases in front of metallic surfaces is a subject of controversial discussion of many plasma types. In this work the excitation source of the Balmer lines is investigated by means of optical emission spectroscopy in the plasma device PSI-2. Neutral fast non-Maxwellian hydrogen atoms are produced by acceleration of hydrogen ions towards an electrode immersed into the plasma. By variation of the electrode potential the energy of ions and in turn of reflected fast atoms can be varied in the range of 40 − 300 eV. The fast atoms in front of the electrode are observed simultaneously by an Echelle spectrometer (0.001 nm/channel) and by an imaging spectrometer (0.01 nm/channel) up to few cm in the plasma. Intense excitation channels of the Balmer lines are observed when hydrogen is mixed with argon or with krypton. Especially in Ar-H and Ar-D mixed plasmas the emission of fast hydrogen atoms is very strong. Intermixing hydrogen with other noble gases (He, Ne or Xe) one observes the same effect however the emission is one order of magnitude less compared to Kr-H or Kr-D plasmas. It is shown, that the key process, impacting this emission, is the binary collision between the fast neutral hydrogen atom and the noble gas atom. Two possible sources of excitation are discussed in details: one is the excitation of hydrogen atoms by argon atoms in the ground state and the second one is the process of the so-called excitation transfer between the metastable states of noble gases and hydrogen. In the latter case the atomic data for excitation of Balmer lines are still not available in literature. Further experimental investigations are required to conclude on the source process of fast atom emission.

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“…In the linear plasma device PSI-2 [2,4] hydrocarbon layer formation can be studied on large time scales (hours). A schematic is depicted in Fig.…”

Section: Methodsmentioning

confidence: 99%

Interaction Between Nitrogen And Hydrocarbons In Magnetized Plasmas

Cwiklinski

Маркин

Baudach

et al. 2008

AIP Conference Proceedings

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Abstract. The deposition of amorphous hydrocarbon (a-C:H) films and the influence of nitrogen on these films were studied. The experiments were performed in low temperature plasmas with T e = 3 . . . 6 eV and n e = 1 · 10 16. . . 4 · 10 17 m −3 . The ratio between injected nitrogen and methane was varied as well as the substrate temperature and the neutral gas pressure. Additionally, the deposition distribution as a function of distance was determined. In situ measurements of the a-C:H growth rate show that the carbon redeposition can be suppressed completely by nitrogen injection (scavenger effect).

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Anomalous Diffusion in a Linear Plasma Generator

Cited by 20 publications

References 21 publications

Influence of the Langmuir Probe Shaft on Measuring Plasma Parameters

Influence of the Langmuir Probe Shaft on Measuring Plasma Parameters

Emission of fast non-Maxwellian hydrogen atoms in low-density laboratory plasma

Interaction Between Nitrogen And Hydrocarbons In Magnetized Plasmas

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