摘要:

AbstractUnipolar arcs have been produced by contacting metal surfaces with microsecond pulse plasmas. Plasma temperatureTe, densityneand potential (with respect to ground) were controlled in the limits 7–12 eV, 1018–1019m−3, 20–40 V, respectively, and the influence of these parameters on arc current amplitude (50–500 A) and ignition probability has been investigated. It was found that the ignition is the most limiting process requiring surface contaminations as well as the transport of net currents to the surface. The amplitude of the current was proportional

ISSN:0005-8025    

DOI:10.1002/ctpp.19830230602

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractOn a déterminé expérimentalement la distribution radiale de la densité des atomes métastables Ar(3P2) et résonnants Ar(1P1) dans deux types de décharges électriques de forme cylindrique: le plasma de la colonne positive d'une décharge en courant continu et le plasma produit par une onde étectromagnétique de surface. En comparant les distributions radiales de densité mesurées pour Ar(3P2) avec les distributions correspondantes calculées à partir du bilan radial création‐destruction de la population de ce niveau, on a pu obtenir les valeurs, en fonction de la position radiale, des coefficients de création et de destruction de ce niveau par collisions électroniques. Ces résultats sont obtenus pour diverses valeurs de la densité électronique sur l'axe. Les valeurs déjà, publiées de ces coefficients dans la colonne positive sont fondées sur l'hypothèse qu'ils ne dépendent pas du courant de la décharge, alors que l'on montre ici que leur valeur décroît en fait lorsque la densité électronique augmente. Ce travail montre de façon plus générale les possibilités considérables qu'offre l'examen de la distribution radiale de densité des atomes excités pour déterminer la

ISSN:0005-8025    

DOI:10.1002/ctpp.19830230603

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe arc spot life time and velocity before reaching melting temperature have been calculated for different electrode materials. They vary between 10−10to 10−14s and 102to 106m/s for heat flux densities of 109to 1012W/m2. The experimental examination of such results was carried out by means of fast rotating electrode disks and tubular electrodes in plasmatrons. The measurements resulted in life times of more than 10−5s with erosion rates from 10−10to 10−2g/As and electrode spot diameters ranging from 0,01 to 5 mm while the heat flux density varied between 107to 1012W/m2. Ten different types of continuous traces, single spots, and craters have been found. Some spot phenomena, the high erosion rates of rotating disks and the similarity of ignition events have been clarified for electrodes made from good conductive materials and less conductive. But the melting and boiling of the spot surfaces was inevitable in

ISSN:0005-8025    

DOI:10.1002/ctpp.19830230604

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractCO/H2‐Gemische lassen sich durch nichtthermische Aktivierung in einer Glimmentladung teilweise in Kohlenwasserstoffe (KW), insbesondere Methan, umsetzen. Als höchster Umsetzungsgrad des CO → KW ergab sich 12%, als höchster Methan‐Partialdruck 3%. Die CO‐Umsetzung ist abhängig von den Entladungsparametern, der Entladungszeit bzw. dem Energieeinsatz und dem CO/H2‐Mischungsverhältnis. Die gebildeten KW sind Zwischenverbindungen, die zu höheren, darunter auch festen KW, weiterreagieren. Auf Grund massenspektrometrischer Ionenanalysen wurde für die KW‐Bildung ein Reaktionsschema entwickelt, das sowohl für ionische als auch für Neutralteilchen‐Reaktionen als

ISSN:0005-8025    

DOI:10.1002/ctpp.19830230605

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractRecently, based on the semigroup approach a new proof was presented of the existence of a unique solution of the non‐stationary Boltzmann equation for the electron component of a collision dominated plasma. The proof underlies some restrictions which should be overcome to extend the validity range to other problems of physical interest. One of the restrictions is the boundary condition applied. The choice of the boundary condition is essential for the proof because it determines the range of definition of the infinitesimal generator and thus the operator semigroup itself. The paper proves the existence of a unique solution for generalized boundary conditions, this solution takes non‐negative values, which is necessary for a distribution function from the physical point of v

ISSN:0005-8025    

DOI:10.1002/ctpp.19830230606

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe instability of a weakly ionized monoenergetic particle beam in a plasma is investigated by means of the weak cold beam description. Such an instability is characterized not only by a collective interaction of the beam electrons with the plasma electrons via the unstable waves but also by collisions of the beam electrons with the neutral beam particles.The considered instability is characterized by a strong velocity focusing and intensive bunching of the beam electrons. An essential enlargement of the maximum wave amplitude relative to the resonant reactive instability [1] was observed.

ISSN:0005-8025    

DOI:10.1002/ctpp.19830230607

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractIt is shown that nonlinear electron plasma surface waves are modulationally unstable and can propagate as solitons on a cold electron plasma‐vacuum interfac

ISSN:0005-8025    

DOI:10.1002/ctpp.19830230608

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe effect of resonant elastic collisions of electrons in He on their “exact” mean energy variation for free path in the presence of a d.c. electric field is analysed.Different values of E/N and both isotropic and anisotropic initial velocity distributions, just after collision, are considered.It is shown that for sufficiently elevated values of E/N a necessary condition for electron (resonance) trapping becomes satisfied.This result is discussed in the light of an interpretative model advanced to explain some electroluminescence phenomena in rare ga

ISSN:0005-8025    

DOI:10.1002/ctpp.19830230609

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractIn the present work the question of the possible use of the hydrodynamic approach for describing a plasma beam discharge is investigated. It is shown that the condition νei>(νei+ νen) XW/nTis the Maxwelliazation criterion of moderate energy particles in a plasma beam discharge. In this case the value of moderate energy is less than 3÷4 values of plasma electrons thermal ernergy.The influence of the tail of the distribution function on electron heating is considered qualitativ

ISSN:0005-8025    

DOI:10.1002/ctpp.19830230610

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe propagation of axisymmetric linear and nonlinear dispersive waves in a three species plasma to include the thermoelectrostatic effects together with the dissipative effects of main ions has been discussed. The impurity driven MHD fluid modes have been examined when the electrostatic drift has been taken into account. We have discussed the linear propagation of dispersive cylindrical waves in the plasma system for different ion thermal phase number. The thermal force resulting from the collisions between main ion and impurity ion densities (i.e. αiI= 0) has been neglected. The shock waves and the soliton solutions are obtained for two different cases of the non‐collisional plasma and the non‐dissipative pl

ISSN:0005-8025    

DOI:10.1002/ctpp.19830230611

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY