摘要:

AbstractBy means of thermodynamic equilibrium calculations emission coefficients of molecular bands of A1O and CN are computed. For given pressure and particle concentrations the coefficients show well defined maxima at certain temperatures, usually referred to as normalized temperature of the band system. This behaviour applied to electrical arcs explains the existence of aureoles caused by molecular emission of CN and some metallic oxide bands localized at fixed distances from the centre of the arc. The local temperature of the area of maximum intensity depends not only on the dissociation energy and excitation energy of the molecule in question, but may be altered by the presence of additional components and stoichiometric conditions. Thus, the normalized temperature of band systems arising from heteronuclear molecules cannot be considered as an unchangeable quantity.

ISSN:0005-8025    

DOI:10.1002/ctpp.19770170102

出版商:WILEY‐VCH Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractVariation of field emitters on Mo‐ and Cu‐cathodes were investigated by field emission microscopy after application of nanosecond voltage pulses. The emitters delivered emission currents with densities of more than 1013Am−2without breakdown. Heating by these currents caused desorption and melting of emitter tips. From the desorption events resonance tunneling was deduced with typical UHV‐conditions. Melting caused blunting of the emitters. Hence sharp micro‐points exploded only by sufficiently fast heating (with time constants ≦ 1 ns) or by secondary effects due to contaminations. By introduction of air in the pressure region of 10−4‐ 10−3Pa new emitting sites appear with time constants of about 10−8s, probably by

ISSN:0005-8025    

DOI:10.1002/ctpp.19770170103

出版商:WILEY‐VCH Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractDas Verhalten von impulsförmig verlaufenden HF‐Entladungen an isolierten Elektroden wird unter anwendungsbedingten Gesichtspunkten für den Fall Ne—N2‐gefüllter kapillarartiger Entladungsraumgeometrien untersucht und insbesondere der Verlauf der Zünd‐ und minimalen Erhaltungsspannung und die Lichtabstrahlung am Kapillarende in Abhängigkeit vom Fülldruck, N2‐Zusatz, Frequenz der Erhaltungsspannung und den geometrischen Parametern verfolgt. Es kann nachgewiesen werden, daß die Entladungen als die bekannten pulse und continuous modes auftreten. Sie besitzen jedoch im allgemeinen höhere ZündspannungenUZals die an ebenen Geometrien und zeigen in ihren Abhängigkeiten von geometrischen Größen Besonderheiten. Die niedrigsteUZhaben dünne zylindrische Elektroden auf Quarz, die wegen der erhöhten Elektrodenkapazität auch die stärkere Lichtabstrahlung besitzen, die höchste gekreuzte Drahtelektroden. — Bei der Konditionierung durch eingestrahltes UV können Rückwirkungen aufUZauftreten. Die Lichtabstrahlung am Kapillarende erfolgt wegen der Linsenwirkung des beim Abziehen entstandenen Glastropfens gerichtet und hängt außer von Gasart und ‐druck von der Zahl der gezündeten Zellen, ihrem Abstand vom Kapillarende, sowie von Freq

ISSN:0005-8025    

DOI:10.1002/ctpp.19770170104

出版商:WILEY‐VCH Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractThe hydromagnetic stability of a self‐gravitating composite plasma has been studied to include the effects of ion viscosity and the finiteness of the ion Larmor radius. The whole medium is embedded in a uniform horizontal magnetic field. The F. L. R. effects have been included through the stress tensor. An explicit solution for a semi‐infinite plasma of finite depth and with an exponential density variation along the vertical is obtained by means of a variational principle characterizing the problem. Numerical calculations show that the influence of the effects of ion viscosity and F. L. R. is to reduce the growth rate of unstable perturbations. On the other hand the effects of neutral gas collisions have been found to be both stabilizing as well as destabiliz

ISSN:0005-8025    

DOI:10.1002/ctpp.19770170105

出版商:WILEY‐VCH Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractThe interaction between fast magnetoacoustic waves within a plasma with periodical nonhomogeneities, perturbed by Alfvén waves has been studied. It has been ascertained the appearance of phenomena of a decay instability and an instability involving an increase of the amplitude oscillations.A study of the influence of perturbed plasma parameters on these instability phenomena has been made. It has been found that the optimal perturbing frequency for giving rise to the instability phenomenon is twice the frequency of fast magnetoacoustic waves

ISSN:0005-8025    

DOI:10.1002/ctpp.19770170106

出版商:WILEY‐VCH Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractThe forces acting on the cathode arc spot surface and removing the molten layer from the crater bottom are composed mainly of the ion pressure, the neutral gas pressure and the evaporation recoil whilst electrostatic forces diminish the effective pressure that is in the order of some 109dyn/cm2. The motion of the liquid layer caused by these forces is treated with the hydrodynamic equations. A simple solution exists in the special case of constant layer depth, that is achieved a few nanoseconds after spot formation. From this model the layer depths (some 0.1 μm) and the ejection velocities at the crater rims (few 104cm/s) are calculated. The real spot velocity agrees with the velocity of the melting front below the spot surface, but because of the stochastic character of the spot motion the apparent velocity decreases with growing observation time intervals Δt according to Δt

ISSN:0005-8025    

DOI:10.1002/ctpp.19770170107

出版商:WILEY‐VCH Verlag    

年代:1977

数据来源: WILEY

ISSN:0005-8025    

DOI:10.1002/ctpp.19770170101

出版商:WILEY‐VCH Verlag    

年代:1977

数据来源: WILEY