Efficient charge neutralization with an ac corona ionizer

This paper discusses the problem of obtaining effective charge neutralization by an ac corona ionizer with airflow. The motion of ions and the neutralization of a charged object for different discharge frequencies and airflow velocities are investigated by a computer fluid model for positive and negative ions. The results of the investigation show that, in the region of ion transport, the quasi-neutralized charge distribution self-generated by positive and negative ions during charge neutralization can effectively transport the ions themselves from an ionizer to a charged object and significantly reduce both the unwanted fluctuation and dc offset in the potential of the object at a steady state, resulting in efficient and precise charge neutralization. Since the quasi-neutralization greatly depends on the relationship between the discharge frequency and airflow velocity, the control of the relationship may lead to better neutralization with an air-blowing ac ionizer.     

A Novel Method for Inhalation Control of Workplace Anthropogenic Pollutant Particles

This in vitro study investigated electrically charging effect on the deposition of inhaled workplace anthropogenic pollutant particles (APP) in a hollow throat cast model. Many occupational lung diseases are associated with exposure to workplace dust particles and other pollutants. Since the human throat is an effective filter, this study devised a novel idea of charging particles, and studying their deposition in the throat. Simulated workplace aerosol particles were generated from a commercially available nebulizer, and charged by a corona charger. Charged and uncharged particles were allowed to pass through a polyester resin cast of cadaver based throat, a replicate of a human oropharyngeal region. The aerosol particles' size and charge distribution were characterized by an Electronic Single Particle Aerodynamic Relaxation Time (ESPART) analyzer before and after passing the throat cast. The ESPART operates on the principle of Laser Doppler Velocimetry to measure simultaneously aerodynamic diameter and electrostatic charge on a single particle basis and in real time. The study results revealed that electrically charging increased agglomeration of smaller particles and increased deposition. Deposition of charged particles increased with increasing particle size which can be explained as the effect of inertial impaction.     

Statistical properties of aggregation with injection

We study a generalized aggregation process in which charged particles diffuse and coalesce randomly on a lattice. For one-dimensional and mean-field models, we show that there exists a statistically-invariant steady state when randomly charged particles are continuously injected. The steady-state charge distribution obeys a power law with the exponent depending both on the type of the injection and on the spatial dimension. The response of the system to a perturbation (i.e., relaxation) is characterized by either a power law decay (t ^– ,1) or a compressed exponential decay [exp(–t ),>1].     

Low energy (E0 < 10 keV) atom and ion scattering of neon from a Cu(100) surface; Ionization and neutralization

The ion fractions η⁺ of low energy (5–10 keV) neon particles scattered from a Cu(100) surface are measured with a time of flight spectrometer. These fractions are obtained for neutral as well as charged projectiles and for different crystal directions. The scattering angle θ was 30°. For a primary energy E₀ of 5 keV neutral projectiles have a value for η⁺ which is 30 times lower than for charged projectiles; these values are 0.15 and 4.5% respectively. For E₀ = 10 keV the values of η⁺ are about the same (~22%). Energy differences up to 22 eV, depending on E₀, are observed between the single scattering peaks in the ion spectra of charged and neutral projectiles but also between the single scattering peak in the spectra of all scattered particles and of ions, with ions as projectiles. A qualitative discussion of these data is given, involving charge transfer processes of noble gas particle and target atom. The data suggest that these neutralization processes can be described more adequately with interatomic neutralization processes along the trajectory than with Auger neutralization by conduction electrons.     

Numerical and experimental studies of collection efficiency of an ion electrostatic collector for a mini-volume electrical PM detector

The experimental efficiency was numerically and experimentally studied for collecting negative and positive ions in a coaxial cylindrical electrostatic collector for a mini-volume electrical PM detector. The commercial computational fluid dynamics software package COMSOL Multiphysics™ was used to predict the behaviors of the flow and electric fields as well as the particle trajectories in the collecting zone of the ion collector. In the experiment, the ions were generated by a corona-needle ionizer with concentrations greater than 10¹³ ions/m³, the positively and negatively applied voltages at the inner electrode ranged from 0 to 45 V and the ion flow rates ranged from 1 to 5 L/min. For these ion flow rates, 1–5 L/min, the ion precipitates due to space charge and diffusion effects ranged from 92 to 97 % for positive ions and 91–97 % for negative ions. The total collection efficiency of the collector increased to 100% at collection voltages larger than 5, 20 and 40 V respectively for the ion flow rates of 1, 3 and 5 L/min for both positive and negative ions. Numerical calculation results of the ion trajectory in the collecting zone of the collector; showed good agreement with the experimental results of the total collection efficiency and can be used to support the bettering of designing in order to refine an ion collector after the charger or ionizer in a mini-volume electrical aerosol detector. Finally, this shows that this ion collector was proven to be particularly useful as an electrostatic collector for positive and negative ions after the charger or ionizer in a mini-volume electrical aerosol detector.     

Internal charge distribution of iodine adatoms on silicon and silicon oxide investigated with alkali ion scattering

Time-of-flight spectra were collected for low energy ⁷Li⁺ and ²³Na⁺ ions backscattered from Si(1 1 1) surfaces covered with sub-monolayers of iodine. Li ions singly scattered from the iodine adatoms have consistently larger neutralization probabilities than those scattered from the silicon substrate, and the neutralization decreases with off-normal emission. This indicates that the internal charge distribution of the iodine adatoms is not uniform, presumably due to attraction of electron density to the positively charged bonding Si atom. Photoelectron spectroscopy shows that iodine adsorbed on pre-oxidized Si bonds through the oxygen atom, forming hypoiodite (-OI) moieties. The neutralization of ²³Na⁺ backscattered from such iodine adatoms is independent of the emission angle, indicating that there is less charge rearrangement than for iodine bonded directly to Si.     

Solution of the Einstein-Maxwell equations for a static distribution of massive charged particles

Exact solutions of the general relativistic field equations of Einstein and Maxwell have been found for a general static distribution of massive charged particles. As in the Newtonian case, the particles must have unit charge to mass ratioe ²/m ²=1. The active gravitational mass of the system of particles is precisely the sum of individual masses of the constituent particles.     

Generalized Noether theorems and applications

We generalize the first and second Noether theorems (Noether identities) to a constrained system in phase space. As an example, the conservation law deriving from Lagrange's formalism cannot be obtained fromH _E via the generalized first Noether theorem (GFNT); Dirac's conjecture regarding secondary first-class constraints (SFCC) is invalid in this example. A preliminary application of the generalized Noether identities (GNI) to nonrelativistic charged particles in an electromagnetic field shows that on the constrained hypersurface in phase space one obtains electric charge conservation. This conservation law is valid whether Dirac's conjecture holds true or not.     

Die Verteilung der natürlichen Radioaktivität auf das Größenspektrum des natürlichen Aerosols

The apparatus described allows to measure the distribution of natural radioactivity on aerosol particles. Careful measures were taken that the aerosol concentration and its size spectrum were not altered before being examined. To increase the accuracy of the measurements the natural aerosol was charged with thoron decay products. The resulting electric charge-distribution by ion diffusion on dust particles is known, therefore the radii of these particles could be calculated by mobility measurements. By means of the law, governing attachment of emanation decay products on dust particles — as derived byLassen orWieser andStierstadt (afterBricard), it is possible to calculate the size spectrum of natural aerosol from the measured activity spectrum. Until now we have onlyion spectra for the range of size 6×10^?7 to 10^?5 cm. With the quoted apparatus however it is possible to measure thesize spectrum of natural aerosol. So we have a simple size-spectrometer, that covers a large range of particles. Among other things can be deduced from these measurements, that the natural radioactivity of air is attached to particles of radii from 10^?6 up to 10^?5cm, — the main part of the activity being carried by aerosols with radii between 4 and 6×10^?6cm. From the calculated aerosol spectrum (r from 6×10^?7 to 10^?5 cm) follows a mean particle radius ofr=2,5×10^?6cm at a particle concentration of 3×10⁴cm^?3.     

Die Anlagerung von radioaktiven Atomen und Ionen an Aerosolteilchen

The attachment of radioactive atoms and ions to spherical aerosol particles has been studied theoretically. For uncharged atoms the deposition is considered to be solely governed by thermal diffusion. With calculations based on the “limiting-sphere”-method ofArendt-Kallman it is found, that the attached activity is proportional toΦ ² for aerosol particle diametersΦ smaller than 0.1 μm, and proportional toΦ forΦ greater than 1 μm. For charged ions the diffusion process is modified by the influence of electrostatic forces between the diffusing ions and the aerosol particles. In the frequently occurring case of a symmetrically bipolar charged aerosol this influence can be expressed by a functionG _p(Φ), which depends on the diameterΦ and the effective numberp of elementary charges on the aerosol particle. For an aerosol particle diameterΦ greater than 0.1 μm the attached activity is proportional toΦ ^1.1, and forΦ smaller than 0.01 μm it is proportional toΦ ^1.55. The effects of neglecting various terms in the calculation are considered. The distribution of natural radioactivity on atmospheric aerosols has been calculated for various particle size distributions according toJunge. The calculation shows that about 90% of the total natural activity should be attached to particles smaller thanΦ=0.5 μm, and about 35% to particles smaller thanΦ=0.1 μm. The time T_1/2, in which the concentration of the radioactive particles decreases to half the initial value, depends on the concentration of the aerosol particles and on their size distribution. For 10⁴ aerosol particles per cm³ and the size distributions mentioned,T _1/2 varies between 15 and 30 seconds for radioactive ions. For radioactive atomsT _1/2 is greater than it is for ions in the range of aerosol particle diameters belowΦ=0.25 μm, and smaller ifΦ greater than 0.25 μm.     

~(129)Xe~(q+)激发Mo表面产生的X射线谱

研究了高电荷态离子129Xeq+(q=25,26,27)入射金属Mo表面产生的特征X射线谱.实验结果表明,在束流强度小于120nA条件下,高电荷态离子129Xeq+可以激发Mo的L壳层特征X射线谱.单离子X射线相对产额可达10-8量级,特征X射线的相对产额随入射离子的动能和电荷态(势能)的增加而增加.通过Mo原子的Lα1特征X射线谱,利用Heisenberg不确定关系对Mo原子的第M能级寿命进行了估算.     

Efficiency of ionizers in removing airborne particles in indoor environments

Air ionizers are increasingly being used to clean indoor environments of particle pollution. We tested the efficiency of a small negative ion generator (Aironic AH-202) in removing ultrafine particles from indoor environments. A high-flow air filter fitted with a HEPA filter was used to compare the removal efficiencies. We estimated the percentage of particles removed when the ionizer was operated within a closed chamber of volume 1 m³, in a closed unventilated room of volume 20 m³ and in three force-ventilated rooms of volume 32, 45 and 132 m³. The closed chamber studies were conducted with ambient particles and with smoke at particle number concentrations of 5 × 10³ and 7 × 10⁴ cm⁻³, respectively. In both cases, 70% of the particles were removed by the ionizer in 15 min. In general, the particle removal efficiency of both the ionizer and the air filter decreased as the room size increased. Both devices were also more effective in unventilated rooms than in ventilated rooms. The most important finding in this study was that, while the air filter was more effective than the ionizer in the two small rooms, the ionizer was clearly more effective than the air filter in the three largest rooms. We conclude that air ionizers are more suited than high-flow air filters in removing ultrafine particles from rooms larger than about 25 m³. The investigation also showed that small ions produced by the ionizer, placed in one room, were carried through the air conditioning system into other rooms, effectively removing particles from the air in these rooms in the process.     

Geminate recombination of long-lived electron-hole pairs in doped carbazole-containing amorphous molecular semiconductors

This paper reports an investigation into the features of geminate recombination of long-lived electron-hole pairs in films of poly(N-epoxypropylcarbazole) (PEPC) containing intramolecular charge transfer compounds as centers of photogeneration of charge carriers carried out by measuring the attenuation kinetics of isothermal recombination luminescence over a wide range of temperatures (4.2–300 K) for times t>1 s, along with the kinetics of photoinduced EPR signals. A study is made of how the presence of a potential barrier to the reverse transition of carriers to the recombination center and the initial triplet state of the charged pairs affects the geminate recombination. It is established that the kinetics of isothermal recombintation luminescence attenuation follow the law I(t)∝t ^−m for the times under study, where m takes values from 0.65 to 1.05. The first observations of a nonmonotonic change in m with temperature are reported (m passes through a minimum at a certain temperature), and a mechanism is proposed for recombination of charged pairs in PEPC containing intramolecular charge-transfer compounds as an explanation for this phenomenon. Fiz. Tverd. Tela (St. Petersburg) 39, 1183–1187 (July 1997)     

Near infrared lights emission of <Superscript>40</Superscript>Ar<Superscript>16+</Superscript> impacting on metal surfaces

The highly charged ion ⁴⁰Ar¹⁶⁺ with the velocity (kinetic energy E _K=150 keV, velocity V=8.5×10⁵ m/s) smaller than Bohr velocity (V _Bohr=2.9×10⁶ m/s) was found to hove impacts on the surfaces of metals Ni, Mo, Au and Al, and the Ar atomic infrared light lines and X-rays spectra were simultaneously measured. The experimental results show that the highly charged ion that captures electrons is neutralized, and the multiply-excited hollow atom forms. The hollow atom cascade decay radiates lights from infrared to X-ray spectrum. The intensity of infrared lights shows that the metallic work functions play an important role in the neutralization process of highly charged ions during their interaction with metallic surfaces, which verifies the classical over-the-barrier model. Supported by the National Natural Science Foundation of China (Grant No. 10574132), the Natural Science Foundation of Shaanxi Province (Grant No. 2007A05) and the Talents Introduction Project of Xianyang Normal University (Grant No. 05XSYK103)     

Decrease in the static electric gas breakdown voltage in the presence of free electrons in a discharge gap

The dependence of the gas breakdown voltage U _B on the anode-cathode spacing d, pressure p, and other gas characteristics in the presence of a steady external ionizer in the discharge gap was determined within the avalanche discharge theory. The case was considered where the spatial charge created by the external ionizer did not distort the electric field in the discharge gap. In the absence of external ionizer the obtained dependence comes down to the well-known expression for the gas breakdown voltage (the Paschen law).     

Energy and charge distributions of fast hydrogen ions and atoms reflected from Cu in the case of grazing incidence

The energy and charge distributions of protons and hydrogen atoms reflected from the Cu surface in the case of grazing incidence angles are measured at energies of incident particles (H⁺ and H⁰) of 200 and 250 keV. The charged fractions of reflected particles are analyzed. A weak dependence of the neutral fraction of reflected particles on the scattering angle is discovered for incidence angles of 1°–2° and an energy of scattered particles of 60 keV or less. It is shown that the neutral fraction of reflected particles with an energy of 60–80 keV or more is independent of the scattering angle and is determined by the ratio of the cross sections for the electron capture and loss by ions in the material.     

Simplified classification of atmospheric charged particles

One of the most important problems on the atmospheric studies is electrostatic interaction between atmospheric cluster ions and aerosol particles.Atmospheric ions are currently classified into 5 overlapping categories having mobilities ranging from 1.3 cm² V^?1 s^?1 to less than 0.004 cm² V^?1 s^?1.We have considered charged ultrafine aerosols and cluster ions as charged atmospheric particles. This classification can be used in the interpretation of electrostatic interactions among these particles.Attachment processes between ultrafine aerosols can be considered as recombination processes between charged atmospheric particles. Atmospheric particles are grouped into two categories, but the number of recombination and attachment coefficients is not reduced.     

Quantum Tunneling of Dirac Particles from?the?Generalized Spherical Symmetric Evaporating Charged Black Hole

Kerner and Mann’s recent research shows that, for an uncharged and non-rotating black hole, its Hawking temperature and tunneling rate can be exactly obtained by the fermion tunneling method from its event horizon. In this paper, considering the tunneling charged particles with spin 1/2, we extend Kerner and Mann’s method to the generalized spherical symmetric evaporating charged black hole which is non-stationary. In order to investigate the fermion tunneling through the event horizon, we choose a set of appropriate matrices γ ^μ . As a result, the tunneling probability and truly effective temperature are well recovered by charged fermions tunneling from the black hole.     

Solutions of the Einstein-Maxwell equations with many black holes

In Newtonian gravitational theory a system of point charged particles can be arranged in static equilibrium under their mutual gravitational and electrostatic forces provided that for each particle the charge,e, is related to the mass,m, bye=G ^1/2 m. Corresponding static solutions of the coupled source free Einstein-Maxwell equations have been given by Majumdar and Papapetrou. We show that these solutions can be analytically extended and interpreted as a system of charged black holes in equilibrium under their gravitational and electrical forces.We also analyse some of stationary solutions of the Einstein-Maxwell equations discovered by Israel and Wilson. If space is asymptotically Euclidean we find that all of these solutions have naked singularities.Alfred P. Sloan Research Fellow, supported in part by the National Science Foundation.     

The scattering of hydrogen from a cesiated tungsten surface

The reflection of protons from a partially cesiated tungsten surface is studied in the energy domain between 100 and 2000 eV and in the angular domain between 75° and 85° with respect to the surface normal. The study is performed by measuring the angular and energy distribution of the scattered negative ions. The reflection can take place along two paths. One path is reflection from the cesium surface layer, the other one is reflection from the tungsten substrate. A dependence of the final charge state on the path is observed. It is inferred that this phenomenon is due to incomplete neutralization of the protons scattered from the cesium layer. The energy loss of the reflected ions cannot be accounted for by using only the binary collision model. Also the electronic stopping of the atoms by the metal electrons is shown to be an important energy loss mechanism. Total conversion measurements of H⁺ to H^- combined with the measurements of the negatively charged fraction of the scattered particles, as reported in the proceeding paper, yield the particle reflection coefficient as a function of the angle of incidence. These reflection coefficients show that for angles of incidence less than 75° already more than 50% of the particles do not reflect from the surface. Total conversion efficiency measurements with H^- ions as primary ions show that the influence of the initial charge state on the total conversion is very small.