摘要:

AbstractThis report will give an introduction to theX‐line emission processes in laser‐generated plasmas according to a plasma physical point of view. After a short discussion of the experimental results using laser pulses in the range of ≲ 10 J and irreadiances of 1 to 100 MW/cm2and of first conclusions about the temperature scaling and the dependence of the emission concerning the atomic number of the target material some models of laser‐generated plasmas are analysed. The simple hot‐spot model neglects any hydrodynamics and only solves for the rate equations. We discuss the underlying collisional‐radiative model and evaluate the numerical results of a more complete model for the spatial and temporal plasma evolution including the hydrodynamics. The applications of such plasmas as small, strong, short sources ofX‐rays in the keV range is discussed with regard to the lithographic replication of sub‐μm structures and to the EXAFS spectroscopy. Laser‐generated plasmas are compared with conventional X‐ray tubes (with rotating anode) and with synchrotrons. The question of amplified spontaneous emission in the XUV range (superradicantX‐ray sources) is only shortly touched upon. In conclusion some comments are given to the recoil momentum effects of the ablating plasma on the target ar

ISSN:0005-8025    

DOI:10.1002/ctpp.19820220402

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractStarting from the conventional theory of thermo‐field emission of electrons from metal surfaces, the range of validity and the errors of several approximate emission formulae are examined that are additive or harmonic combinations of the limiting thermionic (Richardson) and field emission (Fowler—Nordheim) equations. An optimization of such kinds of equations results in the simple dependence (for example)\documentclass{article}\pagestyle{empty}\begin{document}$$ iTf{\rm } \approx {\rm }k(AT^2 {\rm } + {\rm }BF^{9/8}){\rm }\exp \,[-(T^2 /C_1 \, + \,F^2 /D_1)^{ - 1/2],} $$\end{document}(iTFelectron current density,Ttemperature,Ffield strength,k, A, Betc. are constants), or\documentclass{article}\pagestyle{empty}\begin{document}$$ iTF\, \approx \,A'Y^2 \exp( - C'/Y) $$\end{document}(dependent on only one variableY=T+ β′F β′ = const.).If the emission equations are applied to arc cathodes, bothTandFmust be expressed as functions of the ion current (Ii) and the ion current density (ji); a simple interpolating formula of the electron current densityjeadapted to numerical results in the case of Cu cathodes becomes\documentclass{article}\pagestyle{empty}\begin{document}$$ i_e \, \approx \,\overline A i_i \,\exp \,[\overline B i_i \, - \,(\overline C i_i I_i)^{ - 1}], $$\end{document}(Ā, B̄, C̄

ISSN:0005-8025    

DOI:10.1002/ctpp.19820220403

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractFrom several points of view it is of advantage to know the properties of the collision operators in kinetic equations, e.g. in the well known Boltzmann equation, in particular for the purpose of solving eigenvalue problems. With regard to elastic, exciting and deexciting processes some attemps were recently made to investigate such operators in the Boltzmann equation describing the behaviour of electrons in weakly ionized plasmas.In the following we will prove that in the case of a finite dimensional inscattering operator the eigenvalues and the corresponding eigenfunctions can be represented explicitly. Finite dimensional operators were used successfully in special models to approximate the inscattering operators; they possess the property of compactness and are well suitable for analytical or numerical calculations.The representation has been obtained by solving an adequate linear equation system. The generalized eigenfunctions correspond to the normal solutions used by Case in the neutron transport theory. The regularization of the singular integrals which are necessary to obtain this solution will be given in detail. Further a velocity dependence of the collision frequency which need not be monotonous in the considered case and the dependence on the direction could be included.

ISSN:0005-8025    

DOI:10.1002/ctpp.19820220404

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThomson scattering with a 1.5 ms long pulse mode 20 J ruby laser has been applied to a radiative argon plasma with electron densitiesnefrom 2.5 1019m−3to 1.5 1020m−3and an electron temperatureTeof about 3 eV. Photon counting techniques have been used. The accuracy ofneandTeto be reached is about 5% after 10 shots. The signal to noise ratioS/Nhas been optimized by the use of optical filters and a special purpose grating. The effects of these elements onS/Nhave been calculated. The entrance angle, transmission and quantum efficiency have also been optimized. A comparison between 5 possible laser systems, including a normal mode and a Q‐switched mode ruby laser, has been carrie

ISSN:0005-8025    

DOI:10.1002/ctpp.19820220405

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe investigations on the transition between the discharge modes in NeN2mixtures are described in [1]. In the present paper we investigate NeAr mixtures with a view to comparing the behaviour of these different mixtures. The measurements confirm the transition mechanism between the bistable pulse mode and the non‐bistable continous mode in Ne‐Penning mixtures. The life time of metastable atoms is important for the existence of the continuous mode. If the life time is changed by varying the cross sections for the Penning ionizationQp(e.g. in other mixtures), the transition frequency of both these discharge modes shows a corresponding shift, which, for both mixtures, is in good agreement with literature values ofQp. The second part presents a study of the quasiglow mode. The transition between the pulse mode and the quasiglow mode correlates to the ion transit time. The three discharge modes are represented in the existence

ISSN:0005-8025    

DOI:10.1002/ctpp.19820220406

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractA plasma obtained in argon near the surface of ferroelectric BaTiO3ceramics has been examined in this work. It was found that the population densities of the excited Ar II doublet levels are greater than those of the excited Ar II quartet levels. This fact is related to the specific conditions of argon atoms excitation in the electric field of the ferroelectric domains. There is a possibility of ionization with simultaneous excitation of the neutral argon atoms.

ISSN:0005-8025    

DOI:10.1002/ctpp.19820220407

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0005-8025    

DOI:10.1002/ctpp.19820220401

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY