Showing papers on "Electric potential published in 1989"
TL;DR: A new static electromagnetic ion "trap" in which grounded screens placed just inside the usual "trapping" plates produce a good approximation to a "particle-in-a-box" potential (rather than the quadrupolar "harmonic oscillator" potential).
Abstract: Until now, it was thought that the optimal static electromagnetic ion trap for Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry should be designed to produce a quadrupolar electrical potential, for which the ion cyclotron frequency is independent of the ion's preexcitation location within the trap. However, a quadrupolar potential results in a transverse (to the magnetic field) electric field that increases linearly with distance from the center of the trap. That radially linear electric field shifts the observed ICR frequency, increases the ICR orbital radius, and ultimately limits the highest mass-to-charge ratio ion that can be contained within the trap. In this paper, we propose a new static electromagnetic ion "trap" in which grounded screens placed just inside the usual "trapping" plates produce a good approximation to a "particle-in-a-box" potential (rather than the quadrupolar "harmonic oscillator" potential). SIMION calculations confirm that the electric potential of the screened trap is near zero almost everywhere within the trap. For our screened orthorhombic (2.5 in. X 2 in. X 2 in.) trap, the experimental ICR frequency shift due to trapping voltage is reduced by a factor of approximately 100, and the experimental variation of ICR frequency with ICR radius is reduced by a factor of approximately 10 compared to a conventional (unscreened) 2-in. cubic ion trap.(ABSTRACT TRUNCATED AT 250 WORDS)
104 citations
TL;DR: In this paper, a spherical shell model is used to study ion transport and bias voltage formation in asymmetric, capacitive rf discharges, which have unequal areas A and glow-to-electrode voltages V at the powered (a) and grounded (b) electrodes.
Abstract: A spherical shell model is used to study ion transport and bias voltage formation in asymmetric, capacitive rf discharges, which have unequal areas A and glow‐to‐electrode voltages V at the powered (a) and grounded (b) electrodes. Ions are generated by thermal electron ionization and are lost by ambipolar diffusion in the glow. Resonant charge transfer with a constant cross section is assumed to dominate the ion transport. We obtain the density ratio scaling na/nb∝(Ab/Aa )7/24, where n is the density at the glow‐sheath edge. Three electrode sheath models are considered: collisionless ions, collisional (constant mobility) ions, and a constant‐ion cross‐section collisional law. Using these and the continuity of the rf current flow, we obtain the scaling of the electrode voltage ratio with the electrode area ratio: Va/Vb∝(Ab/Aa )q. For typical rf materials processing discharges, the constant cross section law yields q≊2.21. The effects of secondary electron ionization and local ionization near the sheaths due to stochastic heating are shown to further reduce the value of q.
93 citations
90 citations
TL;DR: In this article, the stability of liquid bridges in zero gravity conditions under the influence of an a.c. electric field tangential to the interface is examined, and a static analysis was carried out to find the bifurcation surfaces as a function of the three relevant non-dimensional parameters: Λ, the slenderness or ratio of height to diameter of the cylindrical bridge; β 0, the ratio of dielectric constants of the two fluids used and Ξ, a nondimensional quantity proportional to the applied voltage.
Abstract: The stability of liquid bridges in zero gravity conditions under the influence of an a.c. electric field tangential to the interface is examined in this paper. For the theoretical study, a static analysis was carried out to find the bifurcation surfaces as a function of the three relevant non-dimensional parameters: Λ, the slenderness or ratio of height to diameter of the cylindrical bridge; β0, the ratio of dielectric constants of the two fluids used and Ξ, a non-dimensional quantity proportional to the applied voltage. Stable and unstable regions of Λ−βo−Ξ space were distinguished. Results indicate a strong stabilizing effect for higher values of β0. The experimental study, using silicone and ricinus oil to approximate zero gravity conditions fully confirmed quantitatively the theoretical results.
79 citations
TL;DR: The ability of the solution to Laplace's equation for a spherical dielectric shell to quantitatively describe the membrane potential induced on a lipid bilayer could thus be critically evaluated and both the amplitude and the kinetics of the induced potential were consistent with the predictions of this simple model.
76 citations
TL;DR: Radiation is calculated from currents produced by a nonrelativistic point charge that moves at a constant velocity above a conducting grating to determine the surface charge and the far field vector potential from the surface current.
Abstract: Radiation is calculated from currents produced by a nonrelativistic point charge that moves at a constant velocity above a conducting grating. Two different limits are considered. In the high conductivity limit, the surface charge is calculated from a nonretarded image charge, surface currents from the continuity equation, and the far field vector potential from the surface current. In the plasma frequency limit of the grating substrate a nonretarded electric potential is calculated from a two-region problem, bulk current from an interior potential, and the far field vector potential from the bulk current.
54 citations
01 Oct 1989
TL;DR: In this article, the distribution of the corona space-charge density and the V-I characteristic of a DC precipitator, neglecting the presence of fly ash, are calculated by a numerical procedure based on the finite-element method, which imposes Kaptzov's assumption on the emitter surfaces.
Abstract: The distribution of the corona space-charge density and the V-I characteristic of a DC precipitator, neglecting the presence of fly ash, are calculated by a numerical procedure based on the finite-element method, which imposes Kaptzov's assumption on the emitter surfaces. The ion charge density, the electric potential, and the electric field distributions are evaluated with reference to a real wide-duct electrostatic precipitator installed for testing purposes in the slipstream of the flue-gas duct of a 35 MWe coal boiler. The V-I characteristic, obtained by means of the mathematical procedure described, is compared with the experimentally obtained one. The satisfactory agreement guarantees the reliability of the mathematical model. The model will be implemented by considering the induced effect of the dust present in the flue gas, the back corona, and the dynamic corona originating from the application of pulsed-voltage energization to the electrostatic precipitators. >
54 citations
TL;DR: In this paper, a computational method for calculating the electric potential generated by a set of electrodes on top of a layered dielectric medium is described, where the potential function is expressed by series expansions in terms of solutions of the Laplace equation.
Abstract: A computational method for calculating the electric potential generated by a set of electrodes on top of a layered dielectric medium is described. The potential function is expressed by series expansions in terms of solutions of the Laplace equation. One such expansion is written down for each homogeneous region of the layered structure. The structure coefficients of the different series are related to each other and to the potentials applied to the electrodes via boundary conditions. In the plane of the electrodes, the boundary conditions are satisfied at N discrete points with N being equal to the number of terms in the series expansions. The resulting system of inhomogeneous equations is solved by matrix inversion with the help of a personal computer. >
52 citations
01 Jan 1989
TL;DR: In this paper, the authors used electrokinetic phenomena associated with source-free ground water flow to produce electric potential anomalies at the earth's surface, which can be explained by Japanese geothermal areas.
Abstract: Electrokinetic phenomena associated with source-free ground water flow can produce electric potential anomalies at the earth's surface. Sources of conduction current (required for the appearance of electric potential at the surface) are located at the air-earth interface for terrain-related self-potentials (SP). Induced current sources for SP generation by hydrothermal circulation are thought to be located at underground thermal interfaces which act as boundaries between regions of differing streaming potential coefficients. Field survey results obtained in Japanese geothermal areas can be explained by these electrokinetic mechanisms.
51 citations
TL;DR: In this article, a Monte Carlo simulation of liquid water near a charged wall has been carried out for different values of the surface charge density, and the surface excess of electric potential as a function of charge density has been determined from the polarization profiles.
Abstract: A Monte Carlo simulation of liquid water near a charged wall has been carried out for different values of the surface charge density. The surface excess of electric potential as a function of charge density has been determined from the polarization profiles. The differential capacity of the simulated system is compared with the differential capacity of the mercury/water interface.
50 citations
TL;DR: In this article, numerical methods have been used to find the electric potential distribution in the stationary ion sheath that initially surrounds wedge-shaped cathodes in a plasma, following the application of a large negative voltage pulse.
Abstract: Numerical methods have been used to find the electric potential distribution in the stationary ion sheath that initially surrounds wedge-shaped cathodes in a plasma, following the application of a large negative voltage pulse.
TL;DR: In this paper, a closed dynamical system is constructed which is linear and has the electric charge as one of its degrees of freedom, and the dependence on e2 arises because the complete set of states is generated in a nonlinear, e2 dependent way.
TL;DR: In this article, the complete algebraic expression in the effective dipole approximation for the dielectrophoretic force acting on a spherical object surrounded by a shell when placed in an alternating electric field is deduced.
Abstract: The complete algebraic expression in the effective dipole approximation for the dielectrophoretic force acting on a spherical object surrounded by a shell when placed in an alternating electric field is deduced. In the approximation of a thin shell of low conductivity the frequency dependence of the dielectrophoretic force is discussed revealing the contribution of the shell. The electric potential difference across the shell is also calculated.
TL;DR: Molecular-level models for the solvation of ions, alignment of solvent dipoles, and adsorption of ions onto the pore surfaces of the membrane are combined with Poisson's equation for simulation of the electric potential within a membrane pore.
TL;DR: In this article, the authors extended the convection surge model for ion acceleration to include the self-consistent generation of magnetic-field-aligned electric fields and showed that the model leads to the generation of dynamical macroscopic magnetic field aligned electric fields that begin their strongest developments very near the magnetic equator and then propagate to higher latitudes.
Abstract: The 'convection surge' model for ion acceleration, designed by Mauk (1986) to explain the observed ion distributions and the field-aligned character of middle magnetospheric ion distributions during the expansion phase of a substorm, was extended to include the self-consistent generation of magnetic-field-aligned electric fields. Results from the modified model show that the convection surge mechanism leads to the generation of dynamical macroscopic magnetic field-aligned electric fields that begin their strongest developments very near the magnetic equator and then propagate to higher latitudes. Potential drops as high as 1 to 10 kV might be expected, depending on the mass species of the ions and on the electron temperatures. It is speculated that the convection surge mechanism could be a key player in the transient field-aligned electromagnetic processes observed to operate within the middle magnetosphere.
TL;DR: In this article, it has been estimated that the electrostatic potential propagates in semi-insulating substrates, which may be the primary origin of GaAs metal-semiconductor field effect transistor side gating effects.
Abstract: According to Shockley–Read–Hall statistics for deep traps, it has been estimated that the electrostatic potential propagates in semi‐insulating substrates. In n‐i‐n structures made on hole‐trap‐rich substrates, a negative electric potential applied on an n region is carried to the vicinity of the other electrode. On the other hand, substrates with electron traps act like usual insulators. This phenomenon may be the primary origin of GaAs metal‐semiconductor field‐effect transistor side‐gating effects.
20 Nov 1989-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In an ionization chamber the anode is made of a glass plate on the surface of which very small conductor strips are fixed, and the applied electric potential alternates between each strip as discussed by the authors.
Abstract: In an ionization chamber the anode is made of a glass plate on the surface of which very small conductor strips are fixed. The applied electric potential alternates between each strip. This microstrip anode replaces the wires generally used for electron multiplication in position sensitive gas detectors. The measured energy resolution, the position resolution and the value of the limiting counting rate are reported.
TL;DR: In this paper, a double-charged oxide trap model was proposed to explain channel resistance fluctuations in very small-area MOSFETs, which is brought about by trapping and detrapping of the individual electrons into and from interface traps, respectively.
Abstract: Channel resistance fluctuations in very small-area MOSFET's are caused by a localized modulation of the electrostatic potential at the channel region. The modulation is brought about by trapping and detrapping of the individual electrons into and from interface traps, respectively. The magnitude of the fluctuation is evaluated by using a screened Coulomb potential in two dimensional electron gas together with the electric image force. The magnitude of the channel current fluctuations increases with the number of trapped electrons. The RTS with three current levels is explained by the proposed "double-charged oxide trap" model.
TL;DR: In this article, combined measurements of soil temperature and electric potential in the upper 15 cm of a glacial sandy-loam soil were made during the winters of 1986-1987 and 1987-1988 at the University of Michigan Botanical Gardens at frequencies varying from 10 min to daily (midnight).
TL;DR: For the Schrodinger operator with periodic magnetic (vector) and electric (scalar) potentials, a new system of spectral invariants is found in this article, which is enough to prove the rigidity of isospectral deformations in the class of generic even and real analytic magnetic and electric potentials.
Abstract: For the Schrodinger operator with periodic magnetic (vector) and electric (scalar) potentials a new system of spectral invariants is found. These invariants are enough to prove the rigidity of isospectral deformations in the class of generic even and real analytic magnetic and electric potentials.
TL;DR: In this paper, a commercial capacitively coupled etcher operating at 400 mTorr with 60 W coupled power at 13.56 MHz was used to measure the time varying floating potential.
Abstract: Argon plasma measurements were conducted in a commercial capacitively coupled etcher operating at 400 mTorr with 60‐W coupled power at 13.56 MHz. Time varying floating potential was measured using a capacitively coupled probe which uses a capacitive voltage divider and a field effect transistor buffer amplifier. Average floating potential was obtained from a high‐input‐impedance Langmuir probe. The floating potential was found to be sinusoidal, [21 sin(wt)−4]V±1.5 V, with a maximum of 17±1.5 V and a minimum of −25±1.5 V. From these data and the use of a low‐input‐impedance Langmuir probe, a calibrated instantaneous I–V characteristic is used to obtain plasma potential and electron temperature. Plasma potential was found to be sinusoidal, [21 sin(wt)+30]V±1.6 V, with a maximum of 51±1.6 V and a minimum of 9±1.6 V. Electron temperatures were 6.58±0.19 eV at maximum plasma potential and 6.49±0.19 eV at minimum plasma potential. The electron density for this experiment was determined to be 1.48±0.83×1010 elec...
TL;DR: This dissertation aims to provide a history of web exceptionalism from 1989 to 2002, a period chosen in order to explore its roots as well as specific cases up to and including the year in which descriptions of “Web 2.0” began to circulate.
TL;DR: In this paper, the Coulomb blockade in a single normal tunnel junction is analyzed and the analysis allows an estimate of the tunneling time without contradicting the uncertainty principle, and explains the main features of the I-V characteristics without much mathematics.
TL;DR: In this article, a set of impedance spectroscopy, electroreflectance, and currentvoltage measurements of n-type Si wafers in methanolic solutions of ferrocene derivatives with LiClO4 as the supporting electrolyte have been analyzed using a complementary set of measurements.
Abstract: Photoelectrochemical cells consisting of n‐type 〈100〉‐Si wafers in methanolic solutions of ferrocene derivatives with LiClO4 as the supporting electrolyte have been analyzed using a complementary set of impedance spectroscopy, electroreflectance, and current‐voltage measurements. The results were interpreted in terms of charge accumulation modes correlated with junction parameters such as space‐charge layer, surface states, Fermi‐level pinning, and the possible presence of an insulating layer at the interface. The impedance of these junctions is interpreted in terms of an equivalent circuit. The Fermi level is partially pinned at a potential about 0.2 eV below the conduction band and is completely pinned at potentials positive to midgap. The electroreflectance results agree well with the impedance. The effect of an HF etching on the properties of the cells will be discussed. We have also compared the results in the methanolic solution with an aqueous electrolyte. The potential distribution obtained in this case is very similar to the ferrocene solution.
TL;DR: A theory is presented for a relationship between ion accumulation and electric current loops in multicellular systems such as the roots and stems of higher plants, which shows that the electric current transported across the cell membrane flows between an elongating region and a mature region, not only in roots but also in stems.
TL;DR: The present analysis shows that, unlike the situation for heavy-ion scattering, the Coulomb potential does not cut off the imaginary potential for p-/sup 208/Pb, and no rapid excursions in the parameters of the p+/Sup 208/ Pb potential are expected to occur until the incident energy is well below the Coulombs barrier where the nuclear potential is essentially unobservable.
Abstract: Elastic scattering of protons and neutrons from /sup 208/Pb in the energy range up to 61.4 MeV is analyzed in order to establish a consistent phenomenology with which to examine the recent results of dispersion theory. The present analysis avoids conventional assumptions about the energy dependences of potential depths or geometrical parameters and attempts to include estimates of the uncertainty in our knowledge of the derived potential parameters. Recently reported evidence for energy-dependent geometrical parameters in the n+/sup 208/Pb potential is supported by the present analysis, but no comparable effect is observed for phenomenological proton potentials in the range of available data (E/sub p/>9 MeV). The present analysis shows that, unlike the situation for heavy-ion scattering, the Coulomb potential does not cut off the imaginary potential for p+/sup 208/Pb. Consequently, no rapid excursions in the parameters of the p+/sup 208/Pb potential are expected to occur until the incident energy is well below the Coulomb barrier where the nuclear potential is essentially unobservable.
TL;DR: A new type of relativistic magnetiosonic soliton, which is electrically charged with a gigavolt potential, is found to exist in a magnetized electron-positron-proton plasma.
Abstract: A new type of relativistic magnetosonic soliton, which is electrically charged with a gigavolt potential, is found to exist in a magnetized electron-positron-proton plasma. Relativistic collisionless shocks resulting from such solitons can carry an even larger electric potential at the shock front. GeV electrons and positrons in some active astrophsyical sources may be produced due to acceleration by these electric fields.