The physical nature of the production of moving striations in a d-c discharge plasma

The physical nature of the stratification of the d-c discharge plasma is found and physically interpreted. The interpretation is based on the mathematical expression of the production of periodic structure in plasma after an aperiodic disturbance, derived from an extremely simplified system of equations. Only three basic phenomena occurring in the plasma of each d-c discharge are included: a) the dependence of the rate of ionization on the electron temperature and hence on the electric field, b) the production of space charges due to the different rates of diffusion of the electrons and ions, c) the creation of additional electric fields due to the creation of space charges. The interactions of these phenomena gives rise to a chain, expanded in time and space, which leads to the production of moving striations. In agreement with experiment this structure is developed only on the side towards the anode from the place where the equilibrium state is disturbed.

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. (9, 10) (4, ), . , , : ) , , ; ) , ; ) , . , , — — . , .

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In conclusion the authors thank J. Fousek, J. Kaczér and M. Novák for carefully reading this paper and for valuable remarks, and J. Holub for carrying out the numerical and graphical work.     

The complex conductivity of the plasma of a d-c glow discharge in Ne

In paper [1] Fang derived an expression for the complex conductivity of plasma assuming that the distribution function of the electrons is Maxwellian and the collision frequency is directly proportional to their velocity. Since the assumptions are approximately satisfied in the positive column of a d-c glow discharge in Ne, the applicability of Fang's relation is investigated for this case.

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[1] , . , .

     

Equilibrium state of toroidal electron beam

The paper deals with the collective behaviour of electrons which rotate in a magnetic field used in a betatron. It is shown experimentally that there exists strong interaction between the electrons, which leads to the rapid formation of the equilibrium state with characteristic distribution of the charge density in the cross-section of the toroidal beam. The corresponding relaxation time is of the order of 1 sec. A statistical theory of the equilibrium beam is elaborated. Its main result is that the effective radius of the beam is a function of two parameters, one of which is proportional to the thermal energy of the electrons and the other to the perveance of the beam. The charge contained in a toroidal beam of given effective cross-section is equal to the product of the charge the beam would contain at zero temperature and a coefficient, which is a function of the temperature of the beam. Its value is unity at zero temperature and rapidly decreases with increasing temperature. The cause of cooling of the beam is shown.

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, . , , . 1S. . , , — I/(E₀/q)^3/2 (I — , ₀ — q ). , , , , , . . .

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Now Institute of Vacuum Electronics, Czechosl. Acad. Sci., Prague.

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In conclusion the author thanks J. Luká and L. Hyttych for invaluable help in the experiments, A. Rajský for constructing the electronic apparatus and J. Sokol for preparing the miniature probe.     

К ПРОБЛЕМЕ МАГНИТНОЙ ФОКУСИРОВКИ ПУЧКОВ ЭЛЕКТРОНОВ, ЭМИТТИРО ВАННЫХ С ТЕПЛОВЫМИ СКОРОСТЯМИ

, . — , , — - . , - -. - .     

РАДИОМЕТРИЯ В ГЕОФИЗ ИКЕ

cmambe ome, - . - .     

The influence of compression on the absorption of AgBr single crystals

The influence of compression on the edge of self absorption of AgBr single crystals was studied. The measurements were performed at a temperature of –180°C. The shift of the edge of self absorption was studied both in the field of elastic and plastic deformations. The shift of the absorption edge towards the UV end of the spectrum was determined in the field of elastic deformations and towards the i.r. end in the field of plastic deformations. After the ending of the deformation and after unloading the crystal the return of the absorption edge towards the original position was observed.

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AgBr

AgBr. –180°C. , . , — . .

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The author thanks Prof. Dr. L. Zachoval and K. K. Vacek C. Sc. for their interest in this work and for many comments given during the work.     

Die Temperaturabhängigkeit des Brechungsindex von Silizium

Zusammenfassung Es wird die Abhängigkeit des Brechungsindexn von Silizium von der TemperaturT im Wellenlängenbereich 1,1–5,5 und im Temperaturbereich 109–750°K angeführt. Die Abhängigkeitn=f(T) ist unlinear, für tiefe Temperaturen (T170°K) giltnT ². Theoretisch kann die beobachtete Abhängigkeit nicht unstreitig interpretiert werden, da eine explicite quantenmechanische Beziehung für den Brechungsindex der homeopolaren Kristalle nicht existiert. Es kann jedoch die Lorentzsche klassische Beziehung für Isolatoren angewandt werden. Für diese kann dn/dT numerisch ausgedrückt werden. Die berechneten Werte stimmen befriedigend mit den experimentalen überein. Unsere Ergebnisse sind in guter Übereinstimmung mit der Antoníkschen Theorie der Temperaturabhängigkeit des Brechungsindex der homeopolaren Kristalle.

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T =1,1–5,5 109– 750°. n=f(T) , (T170°) nT ². , . , . dn/dT . . .

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Abschließend danke ich Dr. Z. Trousil von dem Inst. f. techn. Physik der Tschechosl. A. d. W., Prag für die gewährung von Silizium, dem Kollegen Irra für polieren des Prismas, Dr. Tauc von demselben Institut dafür, daß er mir einige Messungen in seinem Laboratorium ermöglichte und der Kollegin ilhavá für ihre Hilfe bei den Messungen.     

ЗАМЕДЛЕНИЕ И ДИФФУЗИ Я НЕЙТРОНОВ В КОНЕЧНЫ Х СРЕДАХ

a - - . ( ) , [1]. - - . , , , .     

РЕАКЦИЯ (γ, р) НА КАДМИИ И ОЛОВЕ

, , , -. [3], . . , , ; . , . , . , . , , .

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(, p) Reaction on cadmium and tin

A study is made of the nuclear photoeffect on Sn and Cd where, in contrast to most of the experiments with this effect up to now, discrete rays were used. The paper complements paper [3], the experimental arrangement of which it has taken over. Several interesting results were obtained — particularly the discreteness of the energy spectrum and the unconventional form of the angular distribution. With tin, the top proton shell of which is completely occupied, the shape of the energy spectrum corresponds to the Wilkinson theory of gigant resonance; with cadmium the energy spectrum is similar to the evaporation spectrum. The angular distributions of the photoprotons of both elements do not satisfy the commonly used relations corresponding to existing theories of nuclear photoeffect. They can, however, be described quite well by empirical equations which contain associated Legendre polynomials of different orders. With both elements the results have features of both a direct and a collective process. The paper gives results, a satisfactory explanation of which would require a new theory including both types of processes.

     

ТЕПЛОВАЯ ЭНЕРГИЯ ДИССОЦИАЦИИ И ОСНОВН ОЕ СОСТОЯНИЕF 2 + -ЦЕНТРОВ

+ - , , g - . , . .F ₂ ⁺ -. .     

The influence of oscillations on ionization in a discharge path

The paper solves the problem of gas ionization in a discharge path in a very dilute gas, where the free path of the electrons is much larger than the dimensions of the path and the transit time of the electrons between the electrodes is of the order of the period of the applied h-f voltage. It was found that for a certain ratio of the transit time of the electrons between the electrodes in the discharge path to the period of the h-f oscillation, resonance occurs when the wattless current component is zero. The electron density rises in the path and thus also the gas ionization.

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, , , . , , . , .

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In conclusion, the author would like to thank F. Benda for preparing the equipment, M. Kivánek for preparing the equipment and some of the measurements, and A. Hrdá for the measurements and for working out the case with equally large a-c and d-c voltages within the framework of her thesis.     

The thickness dependence of the permittivity of barium titanate single crystals

A thickness dependence of the permittivity ofc-domain barium titanate single crystals was found. The experimental results were explained by means of a model of a dielectric with surface layers. The thickness of the layer and the permittivity of the surface layer and bulk of the crystal were determined.

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iO₃

iO₃, -. . , .

     

Quantum Observables,Lie Algebra Homology and TQFT

Let us consider a Lie (super)algebra G spanned by T where T are quantum observables in BV formalism. It is proved that for every tensor c^... that determines a homology class of the Lie algebra G the expression c^...T...T is again a quantum observable. This theorem is used to construct quantum observables in the BV sigma model. We apply this construction to explain Kontsevich's results about the relation between homology of the Lie algebra of Hamiltonian vector fields and topological invariants of manifolds.     

On the ferromagnetism of thin films

In this paper the magnetic properties of ferromagnetic thin layers are studied by calculating the partition function for the magnetic system inKirkwood's approximation of the second order. The results obtained for the Curie temperature and the magnetization are in somewhat better agreement with the experiment than those obtained by Valenta.

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. , , .

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The author extends his thanks to the group of research workers who performed the numerical calculation of the Curie temperatures on the computer CIFA 1, as well as gratitude to Dr. l. Valenta for so kindly supplying information on the results of his investigations on the same subject.     

Paramagnetic resonance of Fe3+ ion in CdWO4 monocrystal

The paramagnetic spectrum of the Fe³⁺ ion in a CdWO₄ monocrystal was measured on a frequency of 9600 kMHz at 290°K. The spin-Hamiltonian of the Fe³⁺ ion was determined and had the form of (1). The constants derived for the spin-Hamiltonian areE/D=0·144±0·002,D=23·8 kMHz.

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Fe³⁺ CdWO₄

Fe³⁺ CdWO₄ 9600 kMHz 290°K. - Fe³⁺ (1), E/D 0,144±0,002 D 23,8 kMHz.

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In conclusion, the authors thank . Bárta and V. Kment from the Society for Chemical and Metallurgical Production in Ústí n/L for producing and supplying the monocrystals and for much valuable advice.     

The rotation of bloch walls

A Bloch wall has an integral magnetic moment which is due to the spatial distribution of the magnetic moments of the spin. The external magnetic field thus acts on the wall with a torque, which leads to the rotation of the sub-domains and therefore to deformation of the walls. A theory of this rotation is given and from it a microphysical model of the undulatory surface structure in uniaxial ferromagnets is derived. Experiments performed on magnetoplumbite single crystals fully confirm the theoretical assumptions.

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. , , . , . , , .

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Our thanks go to J. Fousek and Z. Málek who by reading this paper contributed greatly to the clarity of its presentation.     

ОПРЕДЕЛЕНИЕ ПОСТОЯН НЫХ ДВУХПАРАМЕТРОВЫ Х РЕШЕТОК МЕТОДОМ ОТНО ШЕНИЙ

. . - 10^–4.     

A contribution to the theory of ferromagnetic resonance at high power levels

The instability of spin waves at ferromagnetic resonance is discussed. An equation of the stationary state of spin wavesk0 is derived by means of the quantum theory of spin waves. It is shown when discussing this equation that the concept of the critical uniform precession angle may be obtained when using an approximation which neglects the action of spin wavesk0 backward on their own excitation. We believe we are justified in supposing that, due to this effect, a stable stationary state can exist even above the critical amplitude of uniform precession, given by theories up to now.

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. k0. , , k0 . , , , , .

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In conclusion the author thanks G. A. Smolenskij for enabling him to carry out this work in his laboratory. Thanks also go to the theoretical staff of the Institute of Semi-conductors of Acad. Sci. USSR in Leningrad for valuable discussions, especially to A. I. Anselm, V. L. Gurevic and J. A. Firsov.     

ГАЛЬВАНОМАГНИТНЫИ Э ФФЕКТ В МАРГАНЕЦ-ЦИНК ОВЫХ ФЕРРИТАХ В ОКРЕСТНОС ТИ ТОЧКИ КЮРИ

. , . _c . , , . _c ; .

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The magnetoresistance in zinc-manganese ferrites in the vicinity of the Curie point

The paper describes an exact method for measuring the adiabatic and isothermal magnetoresistant effects in ferrites. It gives the results of studying the temperature dependence of the magnetoresistant effect, which is negative near the Curie point in ferrites and the temperature dependence of which has a maximum of absolute values inT _c . It is also shown that the pronounced maximum of the adiabatic magnetoresistant effect is to a certain extent caused by the magnetocaloric effect. When measuring the dependence of the magnetoresistant effect on the field strength for a temperature equal toT _c , certain small deviations from the theoretically assumed dependence were found; the influence of different factors on these deviations is discussed and a proposal for their explanation is given in analogy to the results known for metals.

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[1].

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