Temporal changes of particle densities and temperatures in a decaying arc discharge

This study deals with a decaying argon plasma at atmospheric pressure. It is shown that cylindrical symmetry is maintained, which enables us to measure experimentally the plasma composition at any moment after the switch-off. The changes in the particle density and the kinetic temperature have been deduced. For an electron density lower than 3x10¹⁶cm^-3, equilibration of the electrons towards the gas temperature is observed. Partial LTE between electrons and excited atoms is discussed.     

Determining the charged particle concentration in a dc arc from the emission spectrum of sodium

Several methods of measuring charged particle concentrations from the emission spectrum of sodium are discussed. The limits of applicability of each method are specified. Discrepancies in charged particle concentrations measured on the basis of the broadening of spectral lines with different Stark constants in an arc discharge are due to the fact that the peak intensities of these lines are determined in various narrow discharge zones. A method for determining the charged particle concentration over the radius of an inhomogeneous axisymmetrical source (arc discharge) from the broadening of several emission lines of sodium with different Stark constants is proposed. It is shown that in the case of strongly inhomogeneous sources the vanishing of spectral lines from the series cannot be used to determine the charged particle concentration in the plasma.In conclusion, the authors wish to thank M. A. El'yashevich for discussing the present paper.     

Design and construction of a home-made and cheaper argon arc lamp

The authors report on the design and construction of an argon arc lamp which provides noticeably a cheaper instrument for laser and medical applications. Cesium-doped tungsten and pure tungsten rods were used, respectively, for the lamp cathode and anode. To seal the glassy tube, a 50–50 Fe–Ni alloy was successfully used as a medium to attach the tungsten electrodes to the borosilicate glass tube. Starting voltage of the lamp versus the gas pressure, operation voltage–current diagram at various gas pressures, and lamp spectrum in the various pressures were measured. A comparison was made with krypton arc lamp. The lamp operation was satisfactory without any crack or fracture during lightening operation. The results showed that the lamp-lightening threshold voltage depends linearly on the pressure and arc length in such a way that there is an increase in the voltage by raising these two parameters. We have also observed that by increasing the argon pressure, there is a shifting in emission spectrum from the ultraviolet to the visible region. Comparison with krypton arc lamp indicated that argon lamp needs a higher threshold lightening voltage.     

Embedding of a relativistic charged particle

A charged particle following the Reissner-Weyl vacuum field-distribution shows in its interior a real singularity (the matter-tensor becomes infinite). By embedding the interior submanifoldds ²=g ₁₁·dr ²+g ₀₀·dt ² into a pseudo-Euclidean spaceE ₃:ds ²=dZ ₁ ² +dZ ₂ ² –dZ ₃ ² one finds that the embedded (r, t)-metric looks like a cone with the top liying in theZ ₁,Z ₂ plane. The general formulas of embedding the complete manifold into a pseudo-Euclidean spaceE ₆ are discussed.     

Behavior of a charged particle in a schwarzschild field

The influence of the De Witt self-action force on the motion of and electromagnetic emission from a charged particle in a Schwarzschild field is considered. It is shown that a charged particle in a Schwarzschild field is equivalent to a neutral particle of the same mass in a certain Reissner-Nordstrom field. A relationship is found between the power of the electromagnetic emission from an accelerated charge and the power of the thermal emission generated in a reference frame with the same acceleration at the event horizon. The quantum-mechanical problem of the motion of and emission from a charge in the field of a minihole is considered. Wave functions, the energy spectrum, and the widths of quasi-stationary levels are found with allowance for the De Witt self-action force. It is shown that the latter is important for large charges, when the solution becomes oscillatory. "Brainstorm" Little Science and Technology Enterprise. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 75–82, July, 1998.     

Electromagnetic energy and momentum from a charged particle

We compute the flux of the stress-energy tensor across a tube surrounding the world line of a charged particle. By slight modifications of the definition of the Coulomb energy-momentum, the resulting expression contains the radiation reaction term (proportional to the square of the four-acceleration) but not the Schott term (proportional to the derivative of the acceleration). The equation of motion for the particle derived from this expression implies a variable rest mass.     

Dynamics of a charged particle bunch in a penning trap

The Lagrangean equations for gas dynamics of a spherical bunch of charged particles in a Penning trap are solved. The solution describes the pulsation of an inhomogeneous particle bunch whose center behaves as a spatial oscillator in a coordinate system rotating with the Larmor frequency.     

Brownian motion of a charged particle in a magnetic field

We develop and numerically illustrate an exact solution of the multivariate, stochastic, differential equations that govern the velocity and position of a charged particle in a plane normal to a uniform, stationary, magnetic field. The equations self-consistently incorporate the Lorentz force into an Ornstein-Uhlenbeck collision model. Properties of the solution in the infinite dissipation limit are explored and the spectral energy density function is found     

Dynamics of a charged particle in a progressive plane wave

The dynamics of a charged particle in a relativistic strong electromagnetic plane wave propagating in a medium is studied. The problem is shown to be integrable when the wave propagates in vacuum. When it propagates in plasma, and when the full plasma response is considered, an exhaustive numerical work allows us to conclude that the problem is not integrable.     

Stability of a charged particle in a combined Penning-Ioffe trap

The axial symmetry of a familiar Penning trap is broken by adding the radial magnetic field of an Ioffe trap. Despite the resulting loss of a confinement theorem, stable orbits related to adiabatic invariants are identified, expressions are given for their frequencies, and resonances that must be avoided are characterized. It seems feasible to experimentally realize the new Penning-Ioffe trap to test these theoretical predictions. It also may be possible to simultaneously confine cold positrons and antiprotons in a Penning-Ioffe trap, along with any cold antihydrogen they may form.     

Adsorption of a polyampholyte on a charged spherical particle

We develop a scaling theory for a single polyampholyte chain adsorbed on a charged spherical particle in a theta-solvent. Adsorption of a polyampholyte molecule is due to its polarization in the electrostatic field of the particle. For large particles with sizes exceeding the thickness of the adsorbed layer, the conformations of the chain are similar to the one found for polyampholyte adsorption on charged planar surface. However, an adsorbed polyampholyte chain forms a self-similar flower-like structure near the particles with sizes smaller than its Gaussian size. These self-similar structures result from the balance of the polarization energy of loops and the excluded volume interactions between monomers. The structure of an adsorbed polyampholyte in the flower-like conformation is similar to that of a neutral star polymer. Received 3 March 2000 and Received in final form 5 July 2000     

Radiation of a charged particle in a random stack of plates

Radiation from a charged particle moving in a system of randomly spaced plates is considered. It is shown that the dominant radiation mechanism is diffusion. The total intensity of radiation is investigated, and its quadratic dependence on particle energy is noted in the optical region. A comparison with Cherenkov radiation is carried out. Zh. éksp. Teor. Fiz. 114, 91–99 (July 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

The motion of a charged particle in magnetostatic and electromagnetic fields

The exact solutions are given of the relativistic equations of motion for both the momentum and displacement of a charged particle which is injected into an arbitrary number of intense electromagnetic waves of any polarization and frequency, including zero, all of which propagate parallel to a uniform magnetostatic field with the speed of light. The solutions are implicit in time.     

Dynamics of a charged particle in a linearly polarized traveling wave

The basic physical processes in laser-matter interaction, up to (for a neodymium laser) are now well understood, on the other hand, new phenomena evidenced in PIC code simulations have to be investigated above . Thus, the relativistic motion of a charged particle in a linearly polarized homogeneous electromagnetic wave is studied, here, using the Hamiltonian formalism. First, the motion of a single particle in a linearly polarized traveling wave propagating in a non-magnetized space is explored. The problem is shown to be integrable. The results obtained are compared to those derived considering a cold electron plasma model. When the phase velocity is close to c, it is shown that the two approaches are in good agreement during a finite time. After this short time, when the plasma response is taken into account no chaos take place at least when considering low densities and/or high wave intensities. The case of a charged particle in a traveling wave propagating along a constant homogeneous magnetic field is then considered. The problem is shown to be integrable when the wave propagates in vacuum. The existence of a synchronous solution is shown very simply. In the case when the wave propagates in a low density plasma, using a simplifying Lorentz transformation, it is shown that the system can be reduced to a time-dependent system with two degrees of freedom. The system is shown to be nonintegrable, chaos appears when a secondary resonance and a primary resonance overlap. Finally, stochastic instabilities are studied by considering the motion of one particle in a very high intensity wave perturbed by one or two low intensity traveling waves. Resonances are identified and conditions for resonance overlap are studied.     

Dynamics of a charged test particle in a hard rod fluid

The motion of a charged hard rod, accelerated by a constant and uniform external field, in a fluid of mechanically identical neutral particles is studied. The system, initially at rest, is excited through collisions with the accelerated particle. A class of initial configurations is found for which recollisions between the charged rod and the excitation caused by it (a moving particle) never occur. The evolution of the velocity distribution of the test particle is analyzed in this case. The possibility of obtaining from microscopic dynamics a kinetic equation is discussed. The dependence of the current on the external field is shown to agree with that predicted by the Boltzmann equation.     

Motion of a charged particle in a uniform rotating magnetic field

The motion of a charged particle in a rotating, uniform magnetic field is investigated. Expressions are obtained for the domains of steady-state motion and for the particle trajectories. The investigation includes a treatment of conditions specifying the particle localization within the bounded space domain.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 7–11, December, 1976.     

Screening of a charged particle field in rarefied ionized gas

A self-consistent field of a charged micron-size particle placed in a rarefied ionized gas is created by both free ions moving along infinite trajectories and trapped ions moving in closed orbits. The character of screening of the particle field is analyzed under dynamic conditions in a nonequilibrium plasma where the temperature (or the mean energy) of electrons greatly exceeds the ion temperature. Under these conditions, trapped ions are generated in a restricted region of the particle field where the transitions between closed ion orbits resulting from resonant charge exchange dominate. This leads to a higher number density of trapped ions compared to that of free ions. The parameters of the self-consistent field of the particle and ions are found when free or trapped ions determine the screening of the particle field, and a similarity law is established for a simultaneous variation of the number density of plasma particles and the particle size. In dusty plasmas of the Solar System, which result from the interaction of the solar wind with dust, formation of trapped ions increases the plasma number density compared to that in the solar wind.