Eine Bemerkung zum Verhalten von Glimmentladungen bei Brennspannungsänderungen im Nanosekundenbereich

A previous experimental investigation showed that the short time behaviour of glow discharges at fast changes of Cathode potential is determined by a damped plasma oscillation in the negative glow. A simple oscillation model brought satisfactory agreement between the measured quantities and those determined by this model. Only the plasma densities were 10 times smaller than the experimental values obtained by other methods. In this work it is shown that taking into account the cathode dark space in a manner analogue to the treatment of the sheath capacities in the theory of the plasma resonance probe gives correct values of densities, too.     

Feldstärke,Stromdichten und mittlere Energien im Katodenfallraum von Glimmentladungen

By integration of energy distribution functions for the cathode fall of H₂ glow discharges we may show:

• 1) Space charge is almost constant within a large part of the dark space, therefore the field strength is a nearly linearly decreasing function of distance from cathode. Deviations from linearity are quantitatively discussed.
• 2) Composition of space charge: The contribution of atomic ions to the space charge may range from 5 to 10%. and the contribution of electrons from 0,1 to 10%, increasing with growing voltage.
• 3) Relative ion and neutral current densities at the cathode (ion current from the glow edge = 1) are decreasing with growing voltage. Molecular neutral current density equals 3 to 10 times molecular ion current density, in case of atomic particles the relation is from 1 to 5.
• 4) Total current density is increasing from 2.0 · 10^?4 A/cm² torr² at the voltage U₀ = 0,19 kV to 3,7 A/cm² torr² at U₀ = 10 kV; cathode field strength is increasing from 0,53 kV/cm torr to 97 kV/cm torr.
• 5) The mean energy of neutrals is smaller than the mean ion energy by a factor of about 0.45…0.85, and the mean energy of molecules is smaller than the energy of atoms by a about 0.2…0.8. The dependence of the mean energies from voltage is discussed.
• 6) The energy gain of electrons is growing from 15% of total dark space energy at 0.19 kV to 70% at 10 kV; the energy gain of neutrals is decreasing at the same time.

     

Zum Mechanismus des Wachstums von Polymerschichten in Glimmentladungen

Starting from the theory of positive column a relation between plasma-parameters and the velocity of growth of polymerfilms produced in glow-discharges is derived.     

Untersuchung von run-away-Elektronen im Neutralgas

The theory of run-away electrons is applied to a special device, where electrons of a given initial velocity move in a neutral gas through a homogeneous electric field. The average velocity of the electrons as a function of the space coordinate for different initial velocities and relative electric fieldsE/p is calculated. In an experimental investigation of this case the velocity distribution of the electrons after their passage of the field space for different initial velocities and relative fieldsE/p is analyzed. Within the range of experimental errors the measured average velocities agree with the calculated ones. On the basis of these experimental velocity distributions the runaway effect at large initial velocities but medium electric fields can be demonstrated.     

Energieanalyse im Elektroneninterferenzbild von Silizium-Einkristallen

Energy analysis are carried out of the electron diffraction pattern of silicon single crystals. Their interpretation gives additional information about the origin of the scattering into Laue- and Bragg-spots, background, and Kikuchi lines. In transmission experiments, most of the intensity appears with the characteristic energy loss of 17 eV and its multiples; these multiples contribute with different amounts to the total intensity in the different parts of the diffraction pattern. In the case of reflexion, most of the intensity has a broad continuous energy loss spectrum; the Bragg-spots and the background show in addition the characteristic energy loss of 10 eV, while in the Kikuchi lines, the transmission energy loss of 17 eV is found again. The quantitative interpretation of these phenomena gives information obout the scattering processes which would not be expected without energy analysis.     

Verteilung von Wismut-Spuren im Korngrenzenbereich von technischem Kupfer

Kupferproben mit Gehalten von 40 bis 100 ppm Wismut, die bei 580 °C eine halbe Stunde geglüht wurden, zeigen eine groβe Anreicherung dieses Elements im Bereich der Korngrenzen. Die Abnahme des Anreicherungsgrades mit fallender Bi-Ge-halten verläuft nicht proportional. Eine Glühung bei 750 °C führt zu einer besseren Verteilung bzw. geringeren Bi-Anreicherung in diesem Bereich.     

Retardierungseffekte im Energieverlustspektrum von GaP

Investigations were made on energy loss intensities of 50 kV electrons in thin single crystals of GaP. Discrepancies in the low energy region were found comparing the measured energy loss intensities with those calculated from the dielectric constant ? by means of former theories: Deviations in the absolute intensities and an additional peak at 3.3 eV. This additional intensity in the energy loss spectrum is due to the radiation losses of the electrons, because ?₁ of GaP is so large that Cerenkov-radiation becomes possible. The experimental results are in good agreement with the energy loss probability calculated by Kröger taking into account the retardation.     

Nichtdiagrammlinien im K-Spektrum von Neon

Ohne Zusammenfassung

---

     

Stark-Effekt-Verbreiterung von Argon-I-Linien im Bogenplasma

The Stark broadening of Ar I spectral lines characterized by quadratic Stark effect was investigated in a wall-stabilized argon arc plasma. Only in some cases the theoretical interruption broadening half widths according toWeisskopf-Unsöld-Lindholm agree with the experimental values, usually they are smaller up to the factor 0.44. On the other side the Stark half widths calculated by the new Griem method are higher than the experimental values, however, mostly they are in the experimental limit of error.     

Tritium im Niederschlag von Freiberg

Die Monatsmittel der spezifischen Tritium-Aktivitäten des Niederschlags von Freiberg für den Zeitraum von 1969 bis 1976 werden mitgeteilt. Der Vergleich mit den entsprechenden Werten einer der benachbarten Stationen, die dem ?Tritium in Precipitation Network” der Internationalen Atomenergiebehörde angehört, zeigt, daß einzelne, ungewöhnlich stark vom normalen Verlauf ab-wichende Monatsmittelwerte auftraten. Diese Abweichungen können zu einer merklichen Verschiebung der über einen mehrjährigen Zeitraum gemittelten spezifischen Tritium-Aktivitäten führen. Bei der Anwendung des Umueltisotops Tritium zur Untersuchung von Grundwasser oder von anderen Prohlemen lokalen Charakters ist daher die Dichte des ?Tritium in Precipitation Network” nicht ausreichend. Der Tritiumgehalt des Niederschlags sollte für das Untersuchungsgebiet oder für eine möglichst nahegelegene Station über einen Iängeren Zeitraum zusätzlich bestimmt werden.     

Stark-Effekt-Verbreiterung von Kohlenstoff I-Linien im Bogenplasma

The half widths of Stark broadened C I spectral lines measured in a wall stabilized arc plasma were compared with theoretical half widths according toGriem. Within the errors of Griems line broadening calculations of about 20% there was agreement between experimental and theoretical half widths for all measured spectral lines with known calculated broadening parameters.     

Kontinuierlicher Absorptionsquerschnitt von Argon im Bogenplasma

Optical pumping on Cs¹³³ atoms was performed by means of a new transmission technique. The cesium vapor was pumped towards equilibrium by an intensive circulary polarizedD ₁ orD ₂ light beam. A weakD ₁ detecting beam was polarized alternately σ⁺, σ^? and allowed one to measure continuously amount and sign of the absorption difference between σ⁺ and σ^? light. The measured signals are proportional to the electron spin polarization. The new technique was used to investigate the influence of Cs buffer gas collisions on the pumping cycle and to measure the influence of radio frequency induced Zeeman transitions on the ground state polarization. In addition the variation of magnetic field and of pumping light intensity and polarization was studied. Some measurements demonstrate the high sensitivity of the applied method. The obtained qualitative results are discussed and further experiments are proposed.