Forced modulation of self excited striations in a discharge tube of varying diameter

Observations on striations contained in a discharge tube of varying diameter are reported and explained in terms of forced modulation.     

Spherical striations in a glow discharge

The stratification of a volume glow discharge is observed experimentally. Spherically symmetric stationary striations are detected. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 11, 679–682 (10 December 1997)     

The successive production of striations in a glow discharge in hydrogen

The manner of successive production of striations moving from the cathode to the anode in a glow discharge in hydrogen is experimentally investigated. For this purpose use is made of the method of an artifically produced transient process in the positive column. It is shown that the fundamental phenomenon in the production of these striations, similarly as with an inert gas, is the wave of stratification. The wave of stratification in hydrogen, however, differs from that in the plasma of an inert gas in the direction of motion of the striations. This direction in a hydrogen discharge is the same as the direction of the successive production of striations, i. e. from cathode to anode. The phenomenological theory of the successive production of moving striations elaborated earlier is also applicable for the wave of stratification in hydrogen.     

THe mechanism of the amplification of moving striations in a d-c discharge

To determine the mechanism of the amplification of moving striations one starts out from the processes which [3] showed to be decisive for the production of stratification of the plasma of a positive column. An analysis of the influence of other processes shows that the main processes leading to the decay of space charges and thus to a smoothing out of the inhomogeneities and thereby to the attenuation of the periodic structure, cannot by overcome by ionization phenomena caused by changes in the concentration of electrons but only partially compensated.It was found that the process which can lead to the predomination of the processes of amplification over the attenuation is the process of the spatial shift of the temperature deflections of the electrons with respect to the additional electric field, which is expressed in a simplified way by Eq. (12).By solving the extremely simplified basic equations it is proved that under favourable conditions this displacement can lead to both a time and a spatial amplification of the striations. Such a possibility is also verified quantitatively by substituting numerical values into the formulae obtained.

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, [3] . , , , , , ., , (12). , , . .

     

Spatial period of moving striations as function of electric field strength in glow discharge

During a systematic investigation of the parameters of a moving stratification in a glow discharge in helium and neon it was found that the spatial period of the striations is a simple, unique function of the d-c (constant) component of the longitudinal electric field strengthE. It was found that this dependence is hyperbolic and that the simple relation (1) or (2) thus holds. In the relation has the significance of a potential fall between the corresponding points of two neighbouring striations and in the measured range of pressures, currents and diameters of discharge tubes it depends only on the sort of gas and type of striations.

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, , E. , , , (1) (2). (1) (2). , .

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The principal results of this work were reported at the 1st conference on electronics in Prague on April 26, 1960.     

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.     

Interaction of modules in discharge tube

We have shown experimentally that by choosing the value of the direct component of the discharge current and the frequency of modulation of alternating component it is possible to control the coupling of modules in a multi-module gas-discharge CO₂-laser with series connection of modules having common resonator and gas space. The depth of intermodulation was measured when one of modules is supplied with only direct current, while other one by the modulated.     

Experimental verification of the theory of the successive production of striations in a glow discharge

The properties of the wave of stratification in the plasma of the positive column in a glow discharge in neon are measured. The measurements are compared with the results of the theory of the successive production of striations and good agreement is found.

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In conclusion the author thanks M. Novák for help in measuring and evaluating the experimental results, and F. Kroupa and V. Krejí for carefully reading this paper and for valuable remarks.     

The theory of moving striations in a D-C discharge plasma II. High current approximation

The integrodifferential equation of striations, found in the preceding part [1] of this theory, is simplified for the case when the Debye lengthl _D is vanishingly small in comparison with the wave-length of the striations. It then takes the form (51b). The still non-zero space charge field then influences the motion of the charge carriers in such a way that it takes on the character of ambipolar diffusion in the axial direction. This is expressed by the first term on the right-hand side of Eq. (51b). The second and third terms describe the influence of the space charge field on the ionization rate through the changes in the electron temperature. Thus the third (integral) term causes the oscillatory behaviour of the transient process excited by a pulse disturbance, while the second term can lead to growth of the amplitude (i.e. to amplification) of the transient wave.The transient solution of Eq. (51b) is given by the formula (73). It is in full qualitative agreement with the experiment and the quantitative agreement is also sufficient. This shows that processes found to be decisive for the very nature of moving striations [11] and for their amplification [16] do determine with sufficient accuracy even other finer properties of striations. The choice of optimum wave-length, in the conditions studied in this paper, is fulfilled by the ambipolar diffusion in the axial direction, which damps the short wave-length striations, and by the final value of the relaxation length of the electron temperature [1/a ₁, see Eq. (4)] which limits the long-distance effect of the electric space charge field on the ionization rate.In conclusion, the authors thank F. Kroupa and M. Novák for carefully reading the paper and for valuable remarks, and S. Vepek for help in the calculations.     

脉冲气体放电管特性测量实验

用TDS210型存贮示波器测量了脉冲气体放电管(闪光灯)的放电特性，同时用PIN型硅光电池测量脉冲光的波形，测量了它们之间的延迟，并计算了脉冲气体放电管的动态电阻，讨论了放电过程从触发到结束的物理图象．     

Directed transport of a Brownian particle in a periodically tapered tube

The problem of the motion of a Brownian particle in a periodically tapered tube induced by a time-periodic longitudinal force with zero mean is considered. Under the action of this force, the particle is shown to drift in a direction opposite to the constant load force applied to it. Analytical solutions for the drift velocity, the stopping force (the load causing the effect to disappear), and the efficiency of converting the energy introduced by perturbations into directed motion have been obtained at a large amplitude of the driving force, when the effect being discussed is maximal. In the range of its applicability extending from zero to asymptotically large force switching frequencies (proportional to the amplitude of the driving force), these solutions are in good agreement with the results of Brownian dynamics simulations.     

Electron thermal diffusion instability and standing striations in the plasma of a dc discharge in molecular gases

A linear theory of waves in the positive column of dc discharge in molecular gases is presented. Full account is taken of local electron hydrodynamics (s.c. quasi-homogeneous equations), which is derived on the basis of a local non-equilibrium distribution of the electron gas. The production term on the right-hand-side of the ion balance equation gives the familiar ionization wawes, but the ion drift enhanced by the high value of the logitudinal field strength, together with the modification of the pertubed electric field incurred by the electron thermal diffusion, causes the dispersion curve to inersect thek-axis. This provides a natural explanation of the amplified low frequency anode directed wave commonly observed in molecular gas discharges as well as of the standing striation pattern. Numerical examples are given for the case of nitrogen.     

脉冲形成线放电过程中Tesla变压器锥形绕组电压分布特性

介绍了Tesla变压器与脉冲形成线一体化结构的工作原理,实验研究了形成线放电过程中形成的冲击电压波在Tesla变压器锥形次级绕组中的分布特性;给出了输入电压脉宽分别为1 μs,500 ns和100 ns时,锥形绕组中的对地电压和匝间电压分布规律;采用首端并绕、末端并绕和在首端加入屏蔽环三种措施优化绕组结构。结果表明：形成线放电过程中,变压器锥形次级绕组不会明显影响形成线中的电场分布,绕组的对地电压呈线性分布,匝间电压曲线起伏剧烈,首端电压梯度最大;三种优化措施都能抑制电压振荡,首端并绕对降低绕组首端电压梯度最为有效,末端并绕对降低绕组末端电压梯度最有效。     

脉冲形成线放电过程中Tesla变压器锥形绕组电压分布特性

 介绍了Tesla变压器与脉冲形成线一体化结构的工作原理,实验研究了形成线放电过程中形成的冲击电压波在Tesla变压器锥形次级绕组中的分布特性;给出了输入电压脉宽分别为1 μs,500 ns和100 ns时,锥形绕组中的对地电压和匝间电压分布规律;采用首端并绕、末端并绕和在首端加入屏蔽环三种措施优化绕组结构。结果表明：形成线放电过程中,变压器锥形次级绕组不会明显影响形成线中的电场分布,绕组的对地电压呈线性分布,匝间电压曲线起伏剧烈,首端电压梯度最大;三种优化措施都能抑制电压振荡,首端并绕对降低绕组首端电压梯度最为有效,末端并绕对降低绕组末端电压梯度最有效。     

The connection between moving and standing striations in a d.c. glow discharge in Ne

The paper describes the standing structure (standing ionization waves) in a d.c. glow discharge in Ne at low currents, and its connection with moving ionization waves. We have found three types of standing waves and have associated them with the dispersion curves established from measurements on all three types of moving waves. Thus one wavelength of standing waves is associated with each dispersion curve related to one type of moving ionization waves.