Ignition Voltage Research Articles

Flexible, Lightweight Arrays of Microcavity Plasma Devices: Control of Cavity Geometry in Thin Substrates

Adaptation of wet chemical processing or replica molding techniques to microcavity plasma device technology has yielded lightweight and flexible arrays in the Al/Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> materials system and plastic substrates, respectively. Microplasma arrays fabricated from two bonded sections of Al mesh with an integral dielectric barrier of nanoporous alumina have an overall thickness of <100 mum, resulting in lamps that are flexible and conformable to a variety of surfaces. Operating these arrays in both flat and curved configurations reveals few changes to the voltage-current characteristics but a reduction of a factor of two in the luminance of curved or bent structures relative to that for a flat array. Truncated paraboloid cavities have also been formed in 30-70-mum-thick Al foil by a sequence of wet chemical processes. Microcavities with an emitting aperture diameter as small as 50 mum have been realized, and arrays comprising 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> cavities exhibit ignition voltages of ~140-150 V (rms) for Ne pressures between 400 and 700 torr and a 20-kHz sinusoidal voltage waveform. Mixtures of Ne and Xe with Xe content up to 67% have been operated successfully. Ignition voltages of only 70-90 V (rms) have been measured for 30 times 30 arrays of 200 times 200-mum <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> microcavities formed in ultraviolet curable polymer by replica molding and operating in 400-600 torr of Ne. For 3% N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Ar mixtures at total pressures of 400-700 torr, the ignition voltages rise to ~150-220 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RMS</sub> for a driving frequency of 20 kHz, the array emission is spatially uniform, and rms currents above 85 mA can be drawn in the steady state by these plastic-based arrays.

P‐84: Cold Cathode Fluorescent Lamps with MgO‐Coated Electrode

AbstractCold cathode fluorescent lamps (CCFLs) adopting MgO‐Coated Electrode are investigated to be a high performance with respect to the reduction of lamp voltage and ignition voltage, the increase of luminance and efficiency, and the reduction of heat‐generation at the electrode in comparison with the conventional CCFLs.

An Application of AC Glow Discharge Stabilized by Fast Air Flow for Water Treatment

A scheme for a plasma-solution reactor on the basis of a glow discharge stabilized by a fast air flow is suggested as a novel water treatment technique. The discharge ignition voltage is about 2.7 kV, and the input power can be as low as 3 W. It is found that plasma is generated in pulsed mode where the duration of each individual pulse is 15-20 mus. A maximal destruction rate of methylene blue dye of 3.27 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> mol/l middots has been received in an acidic medium at a discharge power level of 6 W. A comparison of the efficiency of plasma interaction in different solutions has been carried out. The chemical effectiveness of the plasma treatment decreases with an increase of solution pH. It is shown that the developed glow discharge two phase reactor can be effectively used for destruction of water pollutants.

A Comparative Study of Medium-Voltage Power Converter Topologies for Plasma Torch Under Dynamic Operating Conditions

This paper compares several medium-voltage power conversion systems for plasma torch application. The thermal plasma torch rated for 3 MW, 2 kA with the physical size of 1 m long is selected. The dynamic characteristics of the dc arc in a plasma torch are investigated using advanced 3-D magnetohydrodynamics simulation. The arc voltage noise of plusmn10% due to the periodic pressure wave is modeled as a sawtooth waveform in arc power loss term. The parameters of the Cassie-Mayr arc model are calculated based on 3-D simulation. A 12-pulse thyristor rectifier and two-phase staggered three-level step-down dc-dc converter having 12-pulse front-end diode rectifier are compared under the same dynamic operating condition. The three-level dc-dc converter has superior dynamic performance over the 12-pulse thyristor rectifier under the existence of arc disturbance noise. This power converter topology provides higher ignition voltage around 5 kV during ignition phase and higher arc stability.

FEM Simulation of the temperature distribution and power density at platinum cathode craters caused by high voltage ignition discharges

Craters caused by high voltage ignition discharges on the surface of materials are important features of the erosion processes of electrodes. In this paper, a thermal simulation of the crater formation on a platinum cathode is carried out by means of the finite element method (FEM). The model is based on the modelling of cathode spots and includes phenomena such as ion bombardment, electron emission, vaporization, melting and heat conduction. The surface of the cathode is submitted to various ion power densities (1010–1012 W m−2) of different durations (0.1, 1 and 10 µs) over a disc of a radius a = 10 µm. By comparing the results of the simulation with experimental data of molten depths and molten volumes, characteristic values of the time, the ion power density and the current involved in the crater formation are determined. These values are related to the electrical characteristic of an ignition discharge, permitting the identification of the phase producing the crater. Furthermore, the contribution of the different heat dissipation mechanisms is evaluated and discussed.

Decrease in the ignition pressure of anomalous glow discharge in a magnetron with an ion-beam-irradiated cathode

The influence of an ion beam injected along the axis of the anode electrode of a planar magnetron on the initiation of an anomalous low-pressure glow discharge in a magnetron has been considered. The characteristics of the discharge ignition at pressures <8 × 10−2 Pa and the properties of a planar magnetron with an ion-beam-irradiated cathode are determined. It is established that the discharge ignition voltage decreases with an increase in the ion energy and exhibits a threshold behavior as a function of the ion-beam current. It is shown that there is a prospect for extending the functional capabilities of planar magnetrons through matching of the modes of sputtering of the magnetron anode and cathode by an ion beam and plasma ions of an anomalous glow discharge, respectively.

Microplasma stamps for selective surface modification: design and characterization

Microplasma stamps are based upon the principle of dielectric barrier discharges. They are applied to a new type of area-selective surface modification process at atmospheric pressure. This process integrates the surface treatment and lateral microstructuring within one process step. For this purpose the plasma is ignited in cavities which are formed temporarily by compressing the microplasma stamp and the substrate to be treated. The advantage of the microplasma stamp designs described in this work is the use of polydimethylsiloxane (PDMS) as a dielectric barrier. Because of its flexibility, PDMS enables a good adjustment to varying surfaces and with it ensures completely closed cavities. In this work the design of two different microplasma stamps is presented. Both designs are characterized considering the influence of the aspect ratio on the ignition and breakdown voltage as well as the ignition under varying conditions. All experiments have been carried out at atmospheric pressure with medium frequency excitation (33 kHz). Furthermore the experimental results are verified by simulations using an SIPDP and FEM model.

Microstructure Characterisation of Electrical Discharge Craters using FIB/SEM Dual Beam Techniques

This paper presents the characterisation of erosion craters caused by high voltage ignition discharges on the surface of electrodes. By means of FIB/SEM dual beam techniques such as FIB-cross sectioning, FIB-nanotomography and FIB-EBSD, the microstructure modification below the crater surface is investigated, providing new insights into erosion crater phenomena. It demonstrates also that the use of FIB/SEM is ideally suited for assessing the microstructural nature of sub-micron surface degradation features.

Design and optimization of dielectric barrier discharge microplasma stamps

Microplasma stamps based upon the principle of dielectric barrier discharges are applied to a new type of area-selective surface modification process at atmospheric pressure. This process integrates the surface treatment and lateral microstructuring within one process step. For this purpose the plasma is ignited in cavities which are formed temporarily by compressing the microplasma stamp and the substrate to be treated. In this work we compare different microplasma stamp designs with the objective of minimizing the ignition voltage to the smallest possible value. Several experiments with regard to the ignition voltage have been conducted, operating in air at atmospheric pressure with medium frequency excitation (33 kHz). They contrast the influence of different types of electrical contacts as well as different electrode types and cavity sizes (diameter 100–500 µm) on the ignition voltage. Furthermore the influence of different substrates to be treated and the compression force have been analysed.

TIC rectifier with output voltage phase control. I. Cesium thyratron with a low direct potential drop

The results of investigation of the ignition voltage for a low-voltage cesium arc and direct voltage drops in the discharge in cesium triodes with fine-mesh (∼0.2 mm) and coarse-mesh (∼2 mm) control grids are presented. It is shown that in a cesium vapor pressure range of 0.05–0.1 Torr and for discharge currents of 5–10 A/cm2, direct voltage drops can be reduced to 0.7–0.5 V even for a fine-mesh grid. For a coarse-mesh grid whose holdoff voltage is sufficient for rectifying low voltages (∼15–20 V), direct voltage drops are almost the same as for a diode even for currents of 1 A/cm2 and lower. The critical factor of holdoff voltage loss is the grid emission level (∼1 mA/cm2).

Diamond-Shaped Microplasma Device Using Thick Photoresist as a Barrier Rib in Ne–Ar Gas Mixtures

The discharge characteristics of the diamond-shaped microplasma devices with pure neon, neon-1% argon, and neon-5% argon gas mixtures are investigated. The 5 times 5 arrays of diamond-shaped microplasma devices operating at pressures from 300 to 800 torr have been characterized. The diamond-shaped microplasma devices, offer advantages such as having a high yield process, low ignition voltage, stable glow discharge, and low cost. The electrical properties of neon discharges have been examined with different argon fractions. The diamond-shaped microplasma device operates at voltages as low as 190 V, at 800 torr.

Bipolar Pulsed Electrical Discharges in Liquid

Electrical discharges in water offer a unique plasma source which can be utilized in various novel applications. These discharges are distinguished for the rapid in situ production of highly reactive species when high voltage of about 10-20 kV is applied. Images of the plasma discharges in the water, which are generated by using high-frequency bipolar pulse power supply at relatively low ignition voltages, are presented here.

14-in Diagonal Size Nanotip-Enhanced Plasma Lamp in Liquid Crystal Display

The characteristics of nanotip-enhanced plasma lamps (NTL) as a backlight for liquid crystal displays have been investigated on a 14-in panel. Using a direct-current pulse bipolar waveform driving, the NTL operates with lower ignition and sustain voltages below 300 V compared with conventional plasma lamps due to the tiny discharge gap between the indium tin oxide electrode and nanotip electrodes. Luminous efficiencies of 16 lm/W at the lowest ignition voltage of 150 V have been realized for NTL, which correspond to 3780 of luminance in 260 V with 50 torr of pure xenon gas.

Pulse, dc and ac breakdown in high pressure gas discharge lamps

An optical study of pulse, dc, and ac (50–400 kHz) ignition of metal halide lamps has been performed by investigating intensified CCD camera images of the discharges. The ceramic lamp burners were filled with xenon gas at pressures of 300 and 700 mbar. In comparison with dc and pulse ignition, igniting with an ac voltage decreases the ignition voltage by up to 56% and the breakdown time scales get much longer (∼10−3 s compared with ∼10−7 s for pulse ignition). Increasing the ac frequency decreases the ignition voltages and changes the ionization channel shapes. External irradiation of UV light can have either an increasing or a decreasing effect on ignition voltages.

Ignition of mercury-free high intensity discharge lamps

To achieve a better understanding of the ignition behaviour of D4 lamps for automotive headlights the ignition of mercury-free metal iodide test lamps characterized by a high xenon pressure, a small electrode distance and small electrode–wall distances is investigated. The ignition of these lamps is dominated by a high voltage requirement. Nevertheless lamps are found that show a surprisingly low ignition voltage. Electrical measurements and simultaneous optical observations of the ultra-fast streamer processes show that the breakdown takes place in two different modes. One of the ignition modes which requires a high ignition voltage is characterized by a breakdown in the volume between the electrode tips. The other mode is characterized by streamer discharges along the wall. In this case the cathode, its base and the wall around is involved in the ignition process and the lamp breaks down at low voltages.

Alternating nonsteady gas-discharge modes in an atmospheric-pressure air flow blown through a point-plane gap

The electric and spectral characteristics of a nonsteady discharge in an atmospheric air flow blown through a point-plane interelectrode gap were investigated experimentally. The discharge was produced by applying a constant positive voltage to the point electrode, the amplitude of the applied voltage being much higher than the corona ignition voltage. The nonsteady character of the discharge is due to the spontaneously repeating streamer-spark breakdown, followed by the formation of either a diffuse ultracorona or a filamentary glow discharge. In the latter case, the length of the plasma column increases progressively, being blown off by the gas flow from the discharge gap. The extinction of a filamentary discharge is unrelated to the break of the current channel: the discharge decays abruptly when the filament length reaches its critical value. The distribution of active particles (O, OH, and N*2) carried out from the discharge gap is determined from the data of spectral measurements.

Forced oscillation in LC circuit used for the ignition of discharge lamps

A practical method to reduce device strain in the ballast prior to the discharge process (at the high voltage stage) is presented. An ignitor for high-intensity discharge lamps based on forced oscillation via an external periodic voltage square wave supplied by an inverter digitally controlled is presented. The frequency and amplitude of the ignition voltage of an LC parallel resonant circuit are determined by the design of the proposed ignitor, as shown. Thus, the ignition is achieved without excessive voltage applied to the lamp.

Spatio-temporal breakdown in surface DBDs: evidence of collective effect

This paper presents an experimental investigation of the plasma ignition in a dielectric barrier surface discharge in air at atmospheric pressure. CCD pictures of the discharge are compared with electrical measurements. A detailed study of the current peaks during the positive half period of the applied voltage has been performed. CCD pictures of single discharges events have been taken. They show synchronous breakdowns of plasma filaments, corresponding to current intensities of several amperes. It is shown that each plasma filament transfers a current of about 40 mA. The influence of adsorbed electrons on the synchronization of the plasma filaments is discussed. The length of the filaments increases during the half period and can be plotted as a linear function of the difference between applied and ignition voltages. The differences between the discharges of positive and negative half periods are presented. The discharges of the negative half period consist of diffuse spots of shorter lengths and are characterized by low currents (several milliamperes), and individual breakdowns.

풀 브리지 인버터에 적합한 메탈 핼라이드 램프용 점화기의 해석 및 설계

본 논문은 반도체 소자의 사용없이 구성된 LC 공진 타입의 점화기를 분석하고 설계하였다. 일반적으로 사용되고 있는 점화기는 다이악, 아크갭, SCR과 같은 반도체 소자가 사용된다. 이러한 반도체 소자의 사용으로 인해 회로의 구성이 복잡해지며 신뢰성이 저하된다. 따라서 본 논문에서는 수동 소자로만 구성된 점화기 회로를 분석 및 설계하였으며 제안한 점화기는 램프의 정상 상태에서는 영향을 미치지 않는다. 수학적 분석, 컴퓨터 시뮬레이션과 l[㎾] 메탈 핼라이드 램프용 전자식 안정기를 제작하여 실제 적용해 봄으로서 제안한 점화기의 유용함을 증명하였다.

Stability conditions of argon and helium gas mixtures in an atmospheric pressure plasma jet

Non-equilibrium plasmas can be generated by atmospheric pressure glow discharges, amongst others by atmospheric pressure plasma jets (APPJ), which feature a capacitive radio-frequency discharge between bare metallic electrodes. We investigated the stability conditions for discharges in an APPJ operated with helium–argon mixtures. Uniform α-discharges can be sustained in mixtures ranging from pure helium to pure argon. The ignition voltage increases drastically with argon content. There is also an upper limit for the existence of the α-mode, where α-sheath breakdown occurs. Critical plasma parameters for the α-mode were determined by equivalent circuit models and discussed in respect to dependences on the different models. A critical electron density of 2.4×10 11 cm −3 was obtained for pure helium. It increases steadily with argon content and reaches a value of 1.2×10 12 cm −3 for pure argon. Sheath thicknesses for α-sheath breakdown were calculated in the range of 0.17–0.29 mm for helium–argon mixtures.