Low-voltage Excitation Research Articles

Saturation effects in Y2SiO5:Tb under low-voltage excitation

Low-voltage field emission device phosphors that are excited at high current densities often exhibit brightness saturation with increasing current. The physical processes responsible for saturation can be complex, with several mechanisms contributing, including ground state depletion and excited energy transfer. A two-level model, in conjunction with cathodoluminescence brightness and transient measurements, is used to show the influence of ground state depletion and thermal quenching on the saturation behavior of Y2SiO5:Tb under low-voltage excitation.

Low-Voltage On-Resonance Ion Selection and Storage: An Alternative to Quadrupolar Axialization for FTMS

A new alternative to quadrupolar axialization for ions trapped within a cubic Fourier transform mass spectrometer cell is presented. This method, low-voltage on-resonance excitation, requires no electronic switching hardware, as is necessary for the quadrupolar axialization technique. However, it yields equivalent ion selection performance, both for single- and broad-band ion selection, as is demonstrated with spectra for a number of poly(ethylene glycol) samples, gramicidin S, and a bovine insulin b-chain sample.

Optimal design and noise consideration of micromachined vibrating rate gyroscope with modulated integrative differential optical sensing

A novel design of a micromachined vibrating rate gyroscope is presented. The rate gyroscope consists of a suspended proof mass which is attached by indium bumps to a CMOS chip. The proof mass is excited to vibration by electrostatic force. The displacements due to rate are sensed optically, using CMOS-integrated photodiodes and analog electronics. System considerations, including the mechanical behaviour, optical sensing, electronics, and noise sources of the rate gyroscope, are discussed. An expression for the noise equivalent rate (NER) of the system is obtained in order to derive an optimal design approach for the rate gyroscope. Optimal design and simulations of a case study of a rate gyroscope are presented. The device shows the ability of sensing 1 deg/h even at moderate quality factors of the order of 5000 and low-excitation voltages of 2.25 V.

Kinetics of Oxygen, Platinum/Stabilized Zirconia and Oxygen, Gold/Stabilized Zirconia Electrodes under Equilibrium Conditions

The kinetics of electrodes of the type oxygen, noble metal/stabilized zirconia were investigated electrochemically under equilibrium conditions. Single‐crystal cubic, polycrystalline cubic, and polycrystalline tetragonal zirconia were chosen as electrolyte materials; platinum and gold were employed as metal components. An electrode setup including a working electrode with a massive metal contact was developed and found to be suitable for well‐reproducible long‐term measurements. Impedance spectra were recorded in the temperature range from 773 to 1173 K with an oxygen partial pressure range from 1 to 101,325 Pa using a low excitation voltage. For platinum, the results indicate a uniform reaction mechanism which involves surface diffusion of dissociatively adsorbed oxygen on the metal surface as rate‐determining step. From this, the determination of characteristic thermodynamic data is possible. For gold, the results indicate a change in the reaction mechanism. The results are consistent with one mechanism, in which diffusion limitation of dissociatively adsorbed oxygen on the metal surface occurs, and a competing mechanism, in which transfer limitation of oxygen adsorbed indirect vicinity of the three‐phase boundary takes place. The comparison of the different electrolytes does not exhibit significant differences concerning the electrode kinetics.

The effects of particle size and surface recombination rate on the brightness of low-voltage phosphor

A theoretical expression for the brightness of powder phosphor is derived in order to investigate the effects of phosphor’s properties on low-energy cathodoluminescence. It contains the particle size, surface recombination rate, lifetime of holes, carrier diffusion coefficients, and anode voltage. As such, it can be applied to systematically optimize the design parameters of phosphors for maximum efficiency at low-voltage excitation. Use of the given expression is illustrated and a typical case is analyzed in this study.

Influence of single-phase excitation and magnetizing reactance on transformer leakage reactance measurement

Low voltage and single-phase excitation are often used to measure leakage reactance or short-circuit impedance of transformers. Winding distortion may be detected by comparing field results with factory nameplate values measured at 25-100% of the rated current using three-phase excitation. The results of single- and three-phase excitation will not always correlate. If the voltage applied in the field is not properly selected then the data may be influenced by the magnetizing reactance. The resulting difference between the nameplate value and the field data might then lead to erroneous analysis of test results and could be interpreted as an indication of winding distortion. The intent of this paper is to analyze the physics of the process and gain insight on test circuit selection and analysis of the results. Methods for avoiding erroneous test results are suggested.

Theory of quantized dynamic capacitance charging spectroscopy in nanostructures.

The dynamic mechanism of electrons tunneling back and forth between a source and a nanostructure, leading to a quantized capacitance charging spectroscopy, is revealed. We predict that (1) lock-in voltages show a single peak structure at low ac excitation voltage amplitudes and a twin peak structure at high amplitudes for the tunneling of a single electron; (2) the lock-in voltages show several peaks with different heights for multitunneling electrons within the ac voltage oscillation range. We find that the peak height increases nonlinearly with increasing number of tunneling electrons. These findings are in excellent agreement with experimental measurements.

Photoluminescence of Mn2+‐Doped ZnGa2 O 4 Single‐Crystal Fibers

Manganese‐doped zinc gallate is a new promising cathode ray phosphor material with low excitation voltage. On excitation of the host, we observed strong emission from both the self‐activated (SA) host material and tetrahedrally coordinated Mn2+ ions in single‐crystal fibers. The efficient host‐Mn2+ energy transfer makes this material an attractive candidate for display technology. The experimental results show that the SA center is not an intermediate involved in the host‐Mn2+ energy‐transfer process.

The Dynamics of Helical Shape Memory Actuators

This paper presents an experimental and theoretical study of the dynamic and thermal characteristics of SHAPE MEMORY ALLOY (SMA) actuators. The actua tors are made of a NIckel-TItanium (NITINOL) wires formed in the shape of helical coils that are capable of generating large deflections when subjected to low voltage excitations. The deflections produced are accompanied by significant forces resulting from the unique phase transformation of the NITINOL alloy as it is heated past its transition temperature.

The Preparation and Low Energy Electron (LEE) Excitation of SnO2 : Eu Powder Phosphor

We carried out an investigation on preparation and low energy electron (LEE) luminescence of powder phosphors. Solid powder mixing, hydroxide coprecipitation, and oxalate coprecipitation methods were examined for preparation. The oxalate method was found to give best results. powder phosphors made with 0.5 atomic percent (a/o) and more Eu contained as separate phase. No change of the lattice parameters could be observed up to 8 a/o of added Eu. The amount of Eu actually dissolved in the lattice is estimated to be between 0.05 and 0.5 a/o of Eu/Sn. Cathodoluminescence of phosphors was examined at high and at low excitation voltage. Measured emission spectra did not show green and blue emission lines due to transitions from and higher states, in contrast to observations on single crystals by Crabtree. phosphors show orange‐red emission without any charge‐up effect when excited by electrons as low as 10V. The luminous efficiency was about 0.2–1 lumens/W for various excitation voltages and pulse duties.

Simulation of Ion-Acoustic Wave and Pseudowave Generation in a Plasma

The unexpected effects of a grid in attempts to launch ion-acoustic waves are discussed. A time varying potential on a grid was found to inherently produce ion bursts (pseudowaves) at all voltages and frequencies used. The voltages φ ranged from low (eφ=κTi), to medium (eφ=κTe), to high (eφ≫κTe) in cases where the electron-to-ion temperature ratio was large (Te/Ti=30). The frequencies f used ranged from below to above the ion plasma frequency fpi(0.25fpi≤f≤2fpi). Ion-acoustic waves, however, could be clearly observed only for low excitation voltages and for frequencies at and below the ion plasma frequency. In the computer simulation, the grid is treated as a one-dimensional source of potential, and particle absorption and scattering by the grid wires is neglected. A one-dimensional ion distribution function F(x, v, t) is found by numerically integrating the nonlinear ion Vlasov-Poisson equations by a finite difference method for phase space. Electrons are treated as a massless neutralizating fluid, and the electron density is computed by balancing the electric field against the thermal electron pressure in a self-consistent fashion [ne=n0 exp (eφ)(κTe)−1].

Display devices based on low-voltage excitation of ZnO in a gas plasma

Using a gas plasma as a source of free electrons, a brightness of 60 fL is obtained from an extended layer of ZnO phosphor with about 5 V applied to it. The phosphor efficiency, >10 lm/W, shows little change during 5000 h of operation. For display purposes devices have been constructed incorporating multiple phosphor-coated anodes whose potentials are controlled by low-voltage semiconductor circuits.

Low Voltage CO_2 Laser Excitation

A report of experiments on low voltage excitation of cw CO(2) lasers is presented. Pertinent plasma considerations are given along with the design of various electrode configurations tested. Preliminary results suggest that low voltage excitation of cw CO(2) lasers is practical using a grid structure and an inverted brush cathode assembly in a reduced height transverse geometry. The positive resistance V-I characteristics so obtained permit an order of magnitude reduction in external ballast.

Doppler Measurements of the Kinetic Energies Produced in Radio-Frequency Plasmoids

Measurements of the Doppler widths of the emission lines from radio-frequency plasmoids show that the ions and atoms have much higher kinetic energies in a discharge which forms dark-ring radio-frequency plasmoids than in a discharge which does not form such plasmoids. The values of the translational kinetic energy are shown to depend on the peak rf excitation voltage and the system gas pressure. These experimental results seem to support the potential-well model of plasmoid formation at low pressure and at low rf excitation voltage.

Low Voltage Excitation of Sodium

In an attempt to clarify the available data on excitation of atoms by low velocity electron impact, the author has studied the optical excitation function of the resonance lines in sodium vapor in the range from 1.8 to 4.2 volts. It is found that the excitation probability has three distinct maxima, corresponding to excitation to $3^{2}P$, $4^{2}S$ and $5^{2}S$ states. Within two-tenths of a volt of the excitation potential the probability has dropped to zero and remains at that value until a new energy level is reached. No excitation to the $3^{2}D$ appears, possibly because of the existence of a selection principle in electronic excitation.

Low Voltage Excitation of the Spectrum of Caesium

Low Voltage Excitation of the Spectrum of Caesium