Aerosol Charge Neutralization by a Radioactive Alpha Source

The performance of a Po-210 radioactive ionizer for aerosol charge neutralization and bipolar charging has been evaluated. Monodisperse neutral and singly charged aerosols have been passed through the ionizer and their approach to the steady-state Boltzmann charge measured by measuring the fraction of particles that are electrically charged. The result shows that an Nt of approximately 2.5 × 10⁵ cm^?3 s is needed for the development of a steady-state charge fraction equal to that given by the Boltzmann' s law where N is the ion concentration and t is the residence time of the aerosol in the neutralizer. In addition, the performance of the ionizer for particle charge neutralization in a vibrating-orifice aerosol generator has been evaluated and the result shows that the source is less effective for this application and the residual charge on the particles is considerably higher than that given by the Boltzmann's law.     

A novel ion monitoring device

A new design for an ion monitoring device is proposed. This ion monitor is capable of simultaneous measurement of positive and negative ion currents resulting from the presence of airborne ions (as created by an air ionizer, for example). Information acquired in this way can be used in real-time monitoring of ionizer. Ion balance and production rate of ions of both polarities can be recorded by the new ion monitor, regardless of the type of the ionizer. Robustness and feasibility of the newly developed instrument were verified against the standard charged plate monitor unit (ANSI ESD STM 3.1-2000: EOS/ESD Association Standard for Protection of Electronic Discharge Susceptible Items—Ionization, ESD Association, 2000). The ion monitor significantly shortens the time necessary to evaluate an ionizer, and may additionally provide a feedback signal needed to keep an ionizer unit in balance.     

Characteristics of VUV ionizer in a vacuum chamber of flat panel displays

Flat panel displays are often exposed to the electrostatic damage during various panel manufacturing processes. In this paper, we report the electrostatic discharge failure in a unique process condition of OLED display process during which the substrate of OLED display is turned over while in the vacuum chucking condition. In order to solve this failure, we adopted newly developed technology of VUV (Vacuum Ultraviolet) radiation to neutralize the electrostatic electricity. This technology generates ions and electrons by ionizing residual molecules in vacuum chamber such that it enables the charged substrates to be neutralized in the chamber. While this new neutralization method is certainly effective in high vacuum process, the lifetime and performance of the VUV ionizer are not validated. To understand the lifetime and performance of VUV ionizer, we conducted the experiments in the vacuum chamber of an 8th generation display facility with various operating time of UV lamp. We analyzed the characteristic of VUV lamp and suggested the neutralization mechanism of VUV ionizer in a low pressure. Based on the experiments, this new neutralization method performs well under the high vacuum environment and is able to completely reduce the electrostatic potential down to 0 V within a short time.     

Effect of beam-plasma interaction on ion transport through a cyclotron injector

The influence of collective effects associated with transverse plasma oscillations excited by a beam of negative ions on the neutralization of the space charge due to fast ions is studied. Conditions for the dynamic deneutralization of an unstable ion beam are refined. Analytic expressions for the plasma ion density distribution and for the stationary electric field in a partially neutralized beam are obtained. The equation of motion of a beam in the self-electric field and in an external magnetic field is used to determine the effect of secondary charged particles on the transport of negative ions through the injector of a cyclotron.     

Precisely balanced ionizer using atmospheric pressure glow discharge in air

Ion balance of an ionizer previously developed has been improved, using an atmospheric pressure glow discharge in air as a bipolar ion source. Although the glow ionizer itself has had good performance in ion balance, further we have investigated the possibility of precise control of the ion balance by controlling the discharge itself or the ion flow from the discharge to the object to be neutralized. To control the discharge, we have adjusted the voltage waveform to produce the glow discharge: a dc bias voltage superimposed on a sinusoidal waveform or widths of positive and negative rectangular pulses. Also an adjustable potential of a grid electrode additionally arranged has been employed to control the ion flow. By controlling any of them, we have succeeded in precisely controlling the ion balance of the glow ionizer.     

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.     

Modelling of ions for seeding technique to electrify the atmosphere

There are number of ways in which weak electrification can affect the microphysics of clouds, with consequences for cloud lifetime, radiative properties, and precipitation efficiency. Kauffman [2011] suggested ions produced by direct current generators will add to and enhance the catalysing effects that cosmic ray ions are now known to produce in among other things, lowering nucleation barriers, stimulating charged particle growth and stability and increasing the scavenging rate in clouds. Thus to electrify the atmosphere ions can be generated artificially in abundance along with large electric field.Ions can be generated by the corona effect using Atmospheric electrifiers (a device used to generate negative ions) which makes use of corona discharge phenomenon to charge the air particles. Exact assessment of electric field and charge density distributions and the flow dynamics inside the electrifiers is essential to understand the particle behaviour inside the electrifiers.In this paper, a novel model of governing equations to evaluate the space charge density, electric field intensity and velocity of ionized airflow is suggested as a function of applied voltage. The Poisson and charge conservation equations are derived and hence can be used to estimate the electric field and charge density distributions. Navier stokes equation can be used to get the velocity of ionized airflow because of electric force on the air. Simulation is carried out to validate the proposed model and verify that velocity is function of input voltage and is proportional to it.     

Effect of needle cone angle and air flow rate on electrostatic discharge characteristics of a corona-needle ionizer

In this study, the corona-needle ionizer was designed, constructed, and characterized. Experimental characterizations of the electrostatic discharge in terms of current–voltage relationships of the corona ionizer, including the effects of discharge electrode cone angle and air flow rate were presented. It was found that the charging current and ion concentration in the charging zone increased monotonically with corona voltage. Conversely, discharge currents decreased with increasing angle of the needle cone. The negative corona was found to have higher current than the positive corona. At higher air flow rates, the ion current and concentration were found to be relatively high for the same corona voltage. The effect of air flow rate was more pronounced than the corona voltage. It was also shown that the ion penetration through the ionizer decreased with increasing corona voltage, and increased with increasing air flow rate. The highest ion penetration through the ionizer of the 10° needle cone angle was found to be about 93.7 and 7.7% for positive and negative coronas, respectively. The highest ion penetration for the needle cone angle of 20° was found to be 96.6 and 6.1% for positive and negative coronas, respectively.     

Scaling laws for the spatial distributions of the plasma parameters in the positive column of a dc oxygen discharge

Comprehensive self-consistent simulations of the positive column plasma of a dc oxygen discharge are performed with the help of commercial CFDRC software (), which enables one to carry out computations in an arbitrary 3D geometry using fluid equations for heavy components and a kinetic equation for electrons. The main scaling laws for the spatial distributions of charged particles are determined. These scaling laws are found to be quite different in the parameter ranges that are dominated by different physical processes. At low pressures, both the electrons and negative ions in the inner discharge region obey a Boltzmann distribution; as a result, a flat profile of the electron density and a parabolic profile of the ion density are established there. In the ion balance, transport processes prevail, so that ion heating in an electric field dramatically affects the spatial distribution of the charged particles. At elevated pressures, the volume processes prevail in the balance of negative ions and the profiles of the charged particle densities in the inner region turn out to be similar to each other.     

Continuously balanced pulse-DC ioniser to minimise the offset voltage

In our previous work, the AC type of ionisers was employed to demonstrate a prospective theory obtained by numerical simulations in which continuously emitting quasi-neutralised positive and negative ions from corona ionisers can transport ions effectively to a charged object and yield zero offset voltage. In this paper, we show that this can also be applied to pulse-DC ionisers, resulting in significant improvements in the offset voltage as well as charge-decay times. In addition, we present an implementation method with an electronic circuit design to create such an ion emission from a pulse-DC ioniser.     

Linear propagation of dust acoustic modes in the presence of an electron beam

The physical and optical properties of plasmas are depended on dynamics of species in the discharge volume. Then, the presence of an electron beam, as a separate component, in a dusty plasma can modify the plasma structures through altering the discharge parameters. In this report, the linear propagation of acoustic modes in a collisionless dusty plasma contains electrons, ions and charged dust grains is investigated in the presence of an electron beam. Our analysis indicates that the electron beam can modify the dispersion relations of dust acoustic modes which resulted different data transportation in dusty plasmas. The obtained results are also examined for negative and positive charged dust grains with different number densities. The charge of dust grains represents an important role in the dynamics of the low frequency waves. Additionally, our findings reveal that the propagation of acoustic waves in dusty plasmas can be controlled by adjusting the electron number density of the beam and the cathode potential. Lastly, we obtian the destabilizing effects, originated from dust charge fluctuation, by reconsidering the dispersion relations of both dust acoustic modes.     

Detection of positive and negative ions in a wire ionization counter filled with atmospheric air

The physical processes occurring during the detection of individual ions in a wire counter filled with atmospheric air are studied, and the amplitude distribution of electric pulses is measured. It is shown that a positive ion is detected due to electron emission from the surface of a negatively charged wire, whereas a negative ion is detected due to electron detachment near a positively charged wire. The secondary processes accompanying the neutralization of positive ions at a negatively charged external electrode and negatively charged wire are considered. It is established that, in contrast to standard proportional counters, these secondary processes result in an increase in the number of electric pulses rather than in an increase in the electric pulse amplitude. The wire counter allows the detection of both ions produced inside the detector and ions injected into the detector from the ambient air. Possible applications of air-filled wire detectors are described.     

Ion imbalances on an ionizer-controlled work surface

This paper presents results of investigations carried out to test the influence of charged objects introduced into the vicinity of an ionizer-controlled work surface. The qualitative and quantitative distribution of ions on the ionizer-controlled surface was the main focus of the experiment. Tests were conducted using an ionizer equipped with a feedback control signal loop from a sensor at the output of the ionizer (factory installed internal feedback).     

Elimination of dust particle sedimentation in industry environment

This paper deals with dust particle elimination on industry plastic foils in industry environment and with technical air cleaning for this environment. We describe electro-physical processes that are in progress during electric charge neutralization. These charges arise during foil manufacturing process. We describe a method for electric parameter measurement for such foils, surface charge measurement on foils and methods of their neutralization. We describe an unconventional type of contamination separator for various technical areas. The application of negative or positive unipolar discharge is used in area of air cleaning in medical and other environments.     

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).     

Experimental Measurements on the Current Balance at the Cathode of a Cylindrical Hollow Cathode Glow Discharge

The contribution of positive ions, photons and metastable particles to the secondary emission of electrons from the cathode of an argon glow discharge with cylindrical cathode is measured by sampling the plasma species through a small orifice in the cathode wall and analyzing them in a high vacuum region. Additional experiments are made with a second apparatus which enables the sampling fo plasma species from the negative glow and the dark space. The paper describes the experimental techniques used in both cases and presents estimates on the validity of the results obtained. The positive ions are found to be the dominant contribution to the discharge current at the cathode. The secondary emission of electrons is — in decreasing order of importance — due to impact fo singly charged ions, doubly charged ions and metastable atoms.     

Wake potential with mobile positive/negative ions in multicomponent dusty plasmas

We employ the test charge approach to calculate the electrostatic potential for a test charge in a multicomponent dusty plasma, whose constituents are the Boltzmann distributed electrons, mobile positive and negative ions, and immobile positive/negative charged dust particles. By using the modified dielectric constant of the dust-ion-acoustic (DIA) waves, the Debye screening and wake potentials are obtained. It is found that the presence of mobile negative ions significantly modify the DIA speed and the wake potential. The present results are relevant to polar mesosphere and microelectronic in the context of charged particle attraction and repulsion.     

Simple analytic relations for estimating parameters of the positive column of an electronegative glow discharge in a halogen-containing gas mixture

Asymptotic analysis of the continuity equations for the positive charge plasma of a low- and moderate-pressure dc electronegative discharge is performed under the simple assumption of independence of the rates of plasma-chemical processes from coordinates. As a novelty, the ion diffusion is taken into account for the case when the ion-ion recombination dominates among the perishing mechanism of negative ions. The resultant simple analytic expressions make it possible to estimate (with an error not exceeding 15–25%) the geometrical parameters of spatial distributions of charged particle concentrations in this plasma, as well as the energy parameters, without resorting to complicated numerical simulation.     

Si基Si3N4/SiO2双层膜驻极体的电荷储存与输运

利用等温表面电位衰减及热刺激放电(thermally stimulated discharge,TSD)方法探讨了恒栅压电晕充电经常压化学气相沉积(APCVD)的Si基Si3N4和热生长SiO₂双层薄膜驻极体电荷的存储特性.结果表明:在常温环境中,300℃高温下,以及95%相对湿度时的60℃条件下,所有试样表现出极好的电荷储存稳定性.对于负电晕充电试样,其电荷输运受慢再捕获效应(slow retrapping effect)控制;用热离子发射模型来描述了正电晕充电Si₃N₄/SiO₂驻极体的正电荷输运特性. 关键词： 驻极体 薄膜 电荷储存 热离子发射