Charged Wire Research Articles

Study of the characteristics of a gas-discharge counter with a negatively charged wire in the air

Abstract Gas-discharge counters with a negative potential at the thin central electrode are studied. In a counter with thus applied high-voltage, electron avalanches develop in the direction away from the centre in a greatly decreasing electric field. The mechanism for this process and the effect of various factors are described. The counting and amplitude characteristics are given for one of the counters. The geometrically sensitive region and the dependence of its performance on the type of primary ionization is studied. The counter was tested in the air under normal conditions.

A neutral atom and a wire: towards mesoscopic atom optics

A large variety of trapping and guiding potentials can be designed by bringing cold atoms close to charged or current-carrying material objects. Using a current-carrying wire we demonstrate how to build guides and traps for neutral atoms and using a charged wire we study a 1/r 2 singularity. The simplicity and versatility of the principles demonstrated in our experiments will allow for miniaturization and integration of atom optical elements into matter-wave quantum circuits.

A matter-wave interferometer based on the dc-Stark effect

We present a new separated beam atom interferometer in which the recombination of the atomic wave packet is due to the dc-Stark interaction of an induced atomic dipole with a cylindrically symmetric electric field of a charged wire. The fringe period shows a weak power-law dependence on the de Broglie wavelength and the polarizability of the particles. We present a semiclassical theoretical model for this interferometer which resembles the measured performance of the interferometer without free parameters. A discussion of possible applications of this interferometer for atoms and molecules is given.

Aharonov-Bohm scattering of charged particles and neutral atoms: The role of absorption

The Aharonov-Bohm (AB) scattering of charged particles by the magnetic field of an infinitely long and infinitely thin solenoid (magnetic string) in an absorbing medium is studied. We discuss the partial-wave approach to this problem and show that the standard partial-wave method can be adjusted to this case. The effect of absorption leads to oscillations of the AB cross section. Based on this we investigate the scattering of neutral atoms with induced electric dipole moments by a charge wire of finite radius, which is placed in a uniform magnetic field. The physical realistic and practically important case that all atoms that collide with the wire are totally absorbed at its surface is studied in detail. The dominating terms of the scattering amplitude are evaluated analytically for different physical constellations. The remaining terms are written in a form suitable for a numerical computation. We show that if the magnetic field is absent, the absorbing charged wire causes oscillations of the cross section. In the presence of the magnetic field the cross section increases and the dominating Aharonov-Bohm peak appears in the forward direction, suppressing the oscillations.

Coupled charged Bose quantum wires

We investigate the effect of many-body correlations on the ground-state properties of two coupled charged Bose quantum wires. The intrawire and interwire correlations are treated on the same footing within the self-consistent mean-field theory of Singwi, Tosi, Land and Sjölander. Static properties, viz., pair-correlation functions, local-field correction factors, screened interactions and susceptibilities, are calculated for a range of wire spacings d, wire radii , and boson density parameters . We find that the qualitative dependence of intrawire correlations on and remains the same as found for an isolated wire, except that they become slightly weaker with the decreasing spacing d. The interwire correlations, on the other hand, depend strongly on d and are found to grow in magnitude with decreasing d. Further, we find no evidence for the existence of a charge-density-wave ground state in the density range investigated, , in the close proximity of wires. A comparison with the similar studies on the coupled electron quantum wires reveals that the charge-density-wave instability observed there may be an artifact of the neglect of interwire correlation effects.

Ground-state correlations in a charged Bose quantum wire

We study the ground-state correlations in a charged Bose quantum wire within the self-consistent-field approximation of Singwi, Tosi, Land, and Sjölander. A simple cylindrical model for the quantum wire is used. Static properties (structure factor, pair correlation function, and screened interaction potential), elementary excitation spectra, and ground-state energies are calculated at different boson number densities and wire radii. Our study shows that, in addition to the density of bosons, the wire radius provides an extra control on the strength of the many-body correlations. The correlation effects are found to become increasingly important with decreasing wire radius at a fixed density, and vice versa. The results obtained using the lower-order random-phase approximation are also given. We have compared our results for the screened potential with those for the semiconductor electron quantum wire. It is found that the screened potential for charged bosons is more attractive than that for electrons for rs<8, while the two potentials become essentially the same for rs>8. Therefore, we conclude that the exchange effects associated with the electron statistics act to oppose the overscreening properties of the charged Bose system and are dominated by the Coulomb correlation effects at low carrier densities corresponding to rs>8.

Charged Wire Interferometer for Atoms

We have realized a new type of atom interferometer based on the refraction of matter waves in the radially symmetric electric field of a charged wire. The fringe period shows a power law dependence on the field strength and the de Broglie wavelength. Since the latter dependence is weak, the interferometer has an almost ``white light'' character.

Aharonov-Bohm scattering of neutral atoms with induced electric dipole moments

We investigate the scattering of neutral polarizable atoms from an electrically charged wire placed in a homogeneous magnetic field. The atoms carry an induced electric dipole. The reflecting wire is discussed. We calculate the scattering amplitude and cross section the practically more important case that atoms are totally absorbed at the surface of the wire. If the magnetic field is present, there is a dominating Aharonov-Bohm peak in the forward direction followed by decreasing oscillations for larger angles. An experimental realization of this modulated Aharonov-Bohm scattering should be possible.

Influence of electric fields and pH on biofilm structure as related to the bioelectric effect.

Mixed species biofilms of Klebsiella pneumoniae, Pseudomonas fluorescens, and Pseudomonas aeruginosa were grown in a flow cell fitted with two platinum wire electrodes. The biofilm growing on the wires reached a thickness of approximately 50 microm after 3 days. When a voltage was applied with oscillating polarity, the biofilm attached to the wire expanded and contracted. The biofilm expanded by approximately 4% when the wire was cathodic but was reduced to 74% of the original thickness when the wire was anodic. The phenomenon was reproduced by alternately flushing the flow cell with media adjusted to pH 3 and pH 10 with no electric current. At pH 10 the biofilm was unaltered, but it became compacted to 69% of the original thickness at pH 3. We explained these phenomena in terms of the molecular interactions between charged acidic groups in the biofilm slime and the bacterial cell walls. Contraction of the biofilm under acidic conditions may be caused by (i) the elimination of electrostatic repulsion from neutralization of negatively charged carboxylate groups through protonation and (ii) subsequent hydrogen bonding between the carboxylic acids and oxygen atoms in the sugars. Electrostatic interactions between negatively charged groups in the biofilm and the charged wire may also be expected to cause biofilm expansion when the wire was cathodic and contraction when the wire was anodic. The consequences of the explanation of the increased susceptibility of biofilm cells to antibiotics in an electric field, the "bioelectric effect," are discussed.

Electric field of insulated wire at the interface of two dielectric media

The electric field of a straight charged wire is calculated when the wire is coated with a cylindrical insulation and is placed on the plane boundary between two dielectric media. The exact solution of the problem is derived in form of a rapidly convergent series. The technique used for the solution is based on the effective methods of the theory of functions of complex variables. The peculiarities of the electric field configuration are discussed. Some remarks are included concerning possible generalization of the solution to a system with multiple wires.

Macroscopic study of fine particle plasmas generated by the boat method

The aluminum fine particles generated by the boat method were made into the fine particle plasmas by the irradiation of u.v. light and mixture of gaseous plasmas. The motion of the cloud around the charged sphere indicated that the fine particle cloud irradiated by u.v. light was in mixtures of positively charged particles and negatively charged particles. When fine particle plasmas immersed in argon glow discharge plasmas, the fine particles took a negative charge and were attracted to a positively charged small sphere and wire. This fact was clearly explained by Spitzer's investigation.

In vitro antimicrobial efficacy of silver iontophoretic catheter

A silver iontophoretic catheter was designed consisting of two silver wires connected to an electric power source and disposed in a parallel and helical manner around the proximal subcutaneous segment of a silicone catheter. In an in vitro tunnelled bridge model the silver iontophoretic catheter prevented the migration of Staphylococcus epidermidis from the highly contaminated hub to the sterile tip over a 40-d period. The silver impregnated cuff and electrically charged wires made of aluminium or iron delayed migration for only 72 h. A modified Kirby-Bauer technique, used to test the inhibitory activity of antimicrobial catheters, showed that the silver iontophoretic catheter has a broad spectrum inhibitory activity against Gram-positive bacteria, Gram-negative bacteria and Candida albicans. The silver iontophoretic catheter provides a long-term electrochemical barrier against the migration of organisms from the external contaminated environment into the sterile intravascular compartment.

Silver Iontophoretic Catheter: A Prototype of a Long-Term Antiinfective Vascular Access Device

A silver iontophoretic catheter (SIC) was developed consisting of two electrically charged parallel silver wires helically wrapped around the proximal segment of a vascular catheter. In vitro and in vivo activities of this catheter were compared with those of an aseptic catheter coated with chlorhexidine and silver sulfadiazine (CH/SS). The SIC demonstrated broad-spectrum in vitro inhibitory activity against bacteria and Candida albicans comparable to that of the CH/SS-coated catheter. The durability of activity was determined by incubating catheters in serum at 37 degrees C for various time intervals. After 30 days, the antimicrobial activity of the SIC did not change significantly, while that of the CH/SS-coated catheter was reduced to a suboptimal level. In a rabbit model, the SIC was safe and significantly more efficacious than the CH/SS-coated catheter in preventing colonization with Staphylococcus aureus (P < .05). The SIC has broad-spectrum inhibitory activity of long durability and is highly efficacious in preventing colonization in vivo.

Momentum conservation in the Aharonov-Casher effect

In the Aharonov-Casher effect, the neutron exerts a non-vanishing force on a static line charge (a charged wire). The reaction of this force is the time rate of change of the electromagnetic momentum.

Charge division read-out in a 1.8-m-long wire chamber

This paper reports on the design and the test results of a charge division electronic read-out system for a charged particle proportional wire detector. Electronic calibration and probable error analysis of the system are also discussed. Position resolution for the system has been measured to be 4.8-mm FWHM on a wire of 1.8-m length (0.26%, relative). >

A wire trap for neutral atoms

We present new ways of trapping a neutral atom with static electric and magnetic fields. We discuss the interaction of a neutral atom with the magnetic field of a current carrying wire and the electric field of a charged wire. Atoms can be trapped by the 1/r magnetic field of a current-carrying wire in a two-dimensional trap. The atoms move in Kepler-like orbits around the wire and angular momentum prevents them from being absorbed at the wire. Trapping was demonstrated in an experiment by guiding atoms along a 1 m long current-carrying wire. Stable traps using the interaction of a polarizable atom with the electric field of a charged wire alone are not possible because of the 1/r2 form of the interaction potential. Nevertheless, we show that one can build a microscopic trap with a combination of a magnetic field generated by a current in a straight wire and the static electric field generated by a concentric charged ring which provides the longitudinal confinement. In all of these traps, the neutral atoms are trapped in a region of maximal field, in theirhigh-field seeking state.

Electrostatic fields with straight flux lines

Electrostatic vacuum fields having straight flux lines—so that flux lines are possible orbits for charged test particles—are shown to be restricted to those cases which come to mind immediately: the fields of a point charge, an infinite straight charged wire, and the homogeneous fields. The length of the argument is surprising.

Force on insulated wire at the interface of two dielectric media

The electric field is calculated and the forces are evaluated for the system consisting of an infinitely long charged filamentary conductor located parallel to the plane boundary surface between two dielectric media. The straight filamentary wire is surrounded by a cylindrical insulator. It is established that the direction of the force acting on the charged wire is determined only by a difference in value between the permittivities of the two media and does not depend on the permittivity of the insulation of the wire. The solution of the problem is derived in an analytical form that shows directly the influence of the dielectric materials on the distribution of the electric field and on the values of the forces in the examined system. >

On the solution of periodic cylindrical structures with mixed boundary conditions

In various types of EMP simulators, the existence of spurious electrons is an annoying problem. To reduce this effect, charged wire structures have been employed. The solution of a wire mesh charged to a sufficiently high negative potential to repel these unwanted electrons has previously been handled theoretically by conformal transformation for the limiting case of thin-wire structures. The generalized case of finite-radii cylindrical structures has also been dealt with previously by Fourier transformation. In the present work, separation of variables and the method of moments have been used for a two-dimensional study of the problem of a cylindrical satellite with a periodic structure of narrow sheets having a constant negative voltage. The result is applicable to repelling unwanted electrons in system-generated EMP simulators. The technique is general and hence can easily be extended to the case of a coaxial line with slots as well as other shielding enclosures and similar applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Quantum chaotic scattering with CsI molecules.

A molecular beam of CsI molecules passed through the electric field created by a pair of charged wires is proposed as a laboratory experiment on quantum chaotic scattering. It is shown that the proposed experiment is realistic.