摘要:

AbstractThis paper reviews the properties of the cathode ion flux generated in the vacuum arc. The structure and distribution of mass erosion from individual cathode spots and the characteristics of current carriers from the cathode region at moderate arc currents are described. An appreciable ion flux (∼10% of total arc current) is emitted from the cathode of a vacuum arc. This ion flux is strongly peaked in the direction of the anode, though some ion flux may be seen even at angles below the plane of the cathode surface. The observed spatial distribution of the ion flux is expressed quite well as an exponential function of solid angle. The ion flux is quite energetic, with average ion potentials much larger than the arc voltage, and generally contains a considerable fraction of multiply‐charged ions. The average ion potential and ion multiplicity increase significantly for cathode materials with higher arc voltages, but decrease with increasing arc current for a particular material.The main theories concerning ion acceleration in cathode spots are the potential hump theory (PH), which assumes that all ions are created at the same potential, and the gas dynamic theory (GD), which assumes that all ions are created with the same flow velocity. Experimental data on the potentials and energies of individual ions indicates that these theories in their original forms are not quite correct, however extensions or modifications of the PH and GD theories seem very likely to be able to predict correct values for the charge states, potentials, and energies of individual i

ISSN:0863-1042    

DOI:10.1002/ctpp.2150310302

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe etching of Si wafers in an RF discharge in CF4has been studied using single‐wavelength ellipsometry. The etch rate was measured as a function of surface temperature at two pressures. Only at high pressure (0,36 Torr) a small temperature effect was found. Furthermore, the existence of a modified top layer is suggested by the results of the measurement

ISSN:0863-1042    

DOI:10.1002/ctpp.2150310303

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractIn a preceding part of the paper, based on experimental methods and on a corresponding kinetic model, especially the impact of the effective life times of the 63P1and 61P1Hg resonance levels on the main properties of the low pressure Hg‐–Ar positive column has been studied. In the presented second part these investigations, which have been performed under the aspect of their application in fluorescent lamps, will be continued. They are related to the effects of tube radius and discharge current density. New fluorescent lamps have reduced tube radii fromR= 18 to 13 mm and compact lamps down toR= 5 mm. Thus it is of interest to study the electron distribution function and main macroscopic properties of such low pressure discharge plasmas, where the latter properties are obtained by adequate energy space averaging. At first, results are reported and discussed which are related to the dependence of main plasma parameters on the Hg partial pressure when reducing the discharge tube radius for constant discharge currentiand argon pressurepAr.Starting from the electron distribution function the particle and energy budget will be studied in detail, especially of course the change of the ultraviolet radiation output from both Hg resonance levels 63P1and 61P1and, in addition, of visible radiation. Then, to understand the effect of the discharge current density, as a representative example two cases with different values ofR,iandPAr but with equal current density have been investigated and discussed. Altogether the investigations made will shed light upon the complex relations in the mentioned mixture plasma and give hints to select suitable parameter values which can be useful to improve light sour

ISSN:0863-1042    

DOI:10.1002/ctpp.2150310304

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractTo discribe the temperature dependence of the etching rate of graphite in a hydrogen glow discharge a model is discussed taking into accout the transition from CH4to CH as the main etching product with increasing temperature.

ISSN:0863-1042    

DOI:10.1002/ctpp.2150310305

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractIn a preceding part of the paper, based on the Fourier expansion technique, a new method was developed to study the electron kinetics in weakly ionized, spatially uniform bulk plasmas ofrfdischarges in the established periodic state. Starting from the electron Boltzmann equation the Fourier expansion technique has been applied to the partial differential equation system forfandfA, the isotropic part and the first contribution to the anisotropy of the electron velocity distribution function, where both the distribution parts are the first two coefficients of the Legendre Polynomial expansion of the distribution function. In this part of the paper the new method will be applied to investigate the behaviour of the electron velocity distribution of therfbulk plasma in molecular hydrogen and, in addition, of main macroscopic quantities.The study of the latter quantities will be possible since these are determined by appropriate energy space averaging overfandft, respectively. Thus, a comprehensive harmonics analysis of the electron component of therfH2bulk plasma could be made in a widerffield frequency range. This includes the determination of the harmonics contributions to the isotropic and anisotropic distribution and to relevant macroscopic quantities as dependent on the field frequency for the mentioned widerffield frequency range as well as of the phase angles between the different harmonics. It could be proved that the so‐called 10‐term approximation is sufficient for the description. Further on the periodic alteration of important macroscopic quantities, as mean electron energy, power input from therffield and power loss in collision processes etc., and their period averages will be investigated in this truncation order. The results obtained are discussed and could be especially interpreted within a physical concept based on a comparison of therffield frequency with the lumped collision frequency for energy dissipation and that for impulse dissipat

ISSN:0863-1042    

DOI:10.1002/ctpp.2150310306

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe Saha equation for a plasma in thermodynamic equilibrium (TE) is approximately solved to give the temperature as an explicit function of population densities. It is shown that the derived expressions for the Saha temperature are valid approximations to the exact solution. An application of the approximate temperature to the calculation of TE plasma parameters is also described.

ISSN:0863-1042    

DOI:10.1002/ctpp.2150310307

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA KDV equation is derived to describe the weakly nonlinear behaviour of electron plasma waves propagating along a plasma‐filled cylindrical waveguide immersed in an external strong but finite axial magnetic field. Solution of the KDV equation shows that the soliton properties depend significantly on the strength of external magnetic field as well as on ion motio

ISSN:0863-1042    

DOI:10.1002/ctpp.2150310308

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractIon‐acoustic solitons in a generalized multicomponent plasma are studied through the derivation of Korteweg‐de Vries (K‐dV) equation. The negative ions and ion‐beams play quantitatively various roles on the existence of solitons in the plasma. Especially, the critical density introduced by the negative ions exhibits the existence of a large amplitude soliton in plasmas and due to which a derivation of a modified K‐dV (mK‐dV) equation is needed. By taking the higher order nonlinearity in the plasma, the transition of the K‐dV equation to the mK‐dV equation is also shown. Moreover, various models of the plasma due to the non‐isothermality are also considered in the discussions. Further study closely related to the stability of the soliton is made and yields the salient feature

ISSN:0863-1042    

DOI:10.1002/ctpp.2150310309

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA high power electromagnetic Gaussian beam is assumed to be incident on the F region ionosphere, which causes modification in the plasma temperature and density. Subsequently the evolution of a second Gaussian em beam in such modified F region inosphere has been studied numerically. The numerical calculations are carried out in a two dimensional grid space which covers a region of 80 km horizontally and 100 km vertically. It is seen that the second wave propagating through the modified plasma gets focused in the axial regions and gets filamented near its peak intensity point. Consequently the plasma gets irregularly structured and the resulting fluctuations in plasma temperature and density give rise to a pressure gradient force. This force inturn causes the formation of more number of filamentary structures about the axis in wave intensity and also amplifies the initially formed ones.

ISSN:0863-1042    

DOI:10.1002/ctpp.2150310310

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

ISSN:0863-1042    

DOI:10.1002/ctpp.2150310301

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY