Cavity Discharge Research Articles

Breakdown threshold of dielectric barrier discharges in ferroelectrets: where Paschen's law fails

The piezoelectric activity of charged cellular foams (so-called ferroelectrets) is compared against simulations based on a multi-layer electromechanical model and Townsend's model of Paschen breakdown, with the distribution of void heights determined from scanning electron micrographs. While the calculated space charge hysteresis curves are in good agreement with experimental data, the onset of piezoelectric activity is observed at significantly higher electric fields than predicted by Paschen's law. One likely explanation is that the commonly accepted Paschen curve for electric breakdown in air poorly describes the critical electric field for dielectric barrier discharges in micrometer-size cavities.

G070041 プラズマジェットイグニッションにおける流体力学的効果が希薄予混合気の燃焼促進に与える影響([G07004]エンジンシステム部門一般セッション(4):エンジンシステム)

This study clarified the influence of high temperature gas jet on combustion enhancement effect for lean mixture in the plasma jet ignition by the use of combustion bomb. The hot gas jet was generated by the plasma and was ejected after the plasma jet finished injecting. The combustion chamber had a cylindrical shape with 80 mm of diameter and 40 mm of thickness and its volume was about 201 cm3, and the igniter was attached to the bottom of combustion chamber. The igniter was composed by central electrode, orifice and cavity. Tests were carried out with propane-air mixture at equivalence ratio of 0.6 and cavity depth, orifice diameter and discharge energy were varied. The hot gas jet was visualized by schlieren method in the absence of combustion, and combustion development processes were also visualized and the combustion pressure was measured. The voltage throughout electrical discharge and the plasma luminescence was also measured. The electrical discharge began early and the intense luminescence was emitted from plasma jet as the supplied energy increased. The electrical discharge and light emission durations were not so influenced by igniter configuration. The initial flame kernel and hot gas jet were similarly developed. For small diameter orifice and large volume cavity, flame propagation was enhanced and combustion duration was shortened, because the hot gas jet velocity increased. Because the discharging duration was very short as compared with combustion period, the hot gas jet was more effective against the combustion enhancement than the plasma generated by electrical discharge.

Characteristics of High Speed Electro-thermal Jet Activated by Pulsed DC Discharge

Experimental study of synthetic jet produced by pulsed direct current (DC) discharge is presented. High velocity jet is activated electro-thermally by high frequency pulsed DC discharge in small cavity. A cavity of 2.38 mm diameter cylinder bounded by circular electrode is made in a ceramic plate and a small orifice of 1.78 mm diameter is drilled in the middle of cavity. High frequency pulsed DC discharge instantaneously heats air in the cavity and produces high velocity jet at the exit of the orifice. Schlieren imaging at high framing rate of 100 kHz reveals the presence of supersonic precursor shock followed by the jet emerging from the orifice. The jet velocity reaches as high as about 300 m/s. Jet with smaller cavity volume produces lesser effect and jet velocity reaches maximum at certain cavity volume with given discharge current and orifice size. As duty time of pulse increases from 5 to 20 μs at fixed frequency of 5 kHz, the jet velocity also increases and becomes nearly constant with further increase in duty time. At fixed duty time of 20 μs, higher frequency pulsing of 10 kHz produces degradation of the jet as the discharge pulse continues. The jet developed in this study is demonstrated to be strong enough to penetrate deep into supersonic boundary layer and to produce a bow shock when the jet is issued into Mach 3 supersonic flow.

Modeling of the three-dimensional structure of hydrological fields in a karst cavity under the action of submarine discharge of underground waters

We discuss the results of numerical simulation of the process of submarine discharge in a karst cavity. It is assumed that fresh water percolates through cracks in the lateral boundaries of the cavity, and its temperature is, generally speaking, not equal to the temperature of water in the grotto. The calculations are carried out within the framework of a three-dimensional model on the σ -coordinates in the hydrostatic approximation by using the procedure of “convective adjustment” guaranteeing the existence of stable density stratification with conservation of the amounts of heat and salt. The comparison with the data of observations shows that the model gives a qualitatively correct description of the structure of the fields of temperature, salinity, and current velocities formed as a result of submarine discharge in the cavity. The possibilities of subsequent improvement of the model are discussed.

Evaluating pressure due to the electrohydraulic effect in an infinite elastic medium

Assuming a homogeneous pressure distribution in the volume of water, the pressure developed upon discharge in a spherical water-filled cavity surrounded by an infinite elastic medium is calculated as a function of the action integral S = ∫ 0 i 2(t dt, where i is the current in the discharge channel. It is shown that the maximum pressure in discharge significantly decreases for relatively soft chamber wall materials (minerals, concrete) as compared to the approximation of undeformable cavity walls.

Plasma production by means of discharge in a spherical cavity

The work is devoted to the study of plasma, appearing as a result of cumulation of shock wave with form close to spherical. The shock wave was obtained by triggering of fast discharge (dI/dt about 1012 A/s) on inner surface of cavity, made from insulator. Spherical cavity with radius 4.5 mm was filled with Ar at 80 Pa. Inductive storage with semiconductive opening switch was used as a current driver. Spherical plasma with diameter about 1 mm, emitting in vacuum ultraviolet (vuv), was detected by means of pinhole measurements with time gated microchannel plate camera, starting about 50 ns from the beginning of the discharge. vuv spectra have shown the presence spectral lines of ArV–ArVIII ions, which gives the estimation of electron temperature as 30 eV. The plasma ball reveals no instabilities, keeps its characteristics and emits vuv radiation during 300 ns. After 600 ns from the beginning of the discharge plasma emits a flux of electrons with energies about 1 keV with temporal structure about 100 ns.

A numerical simulation of surface wave excitation in a rectangular planar-type plasma source

The principle of surface wave plasma discharge in a rectangular cavity is introduced simply based on surface plasmon polariton theory. The distribution of surface-wave electric field at the interface of the plasma-dielectric slab is investigated by using the three-dimensional finite-difference time-domain method (3D-FDTD) with different slot-antenna structures. And the experimental image of discharge with a novel slot antenna array and the simulation of the electric field with this slot antenna array are both displayed. Combined with the distribution of surface wave excitation and experimental results, the numerical simulation performed by using 3D-FDTD is shown to be a useful tool in the computer-aided antenna design for large area planar-type surface-wave plasma sources.

Systemic Adenovirus Infection in Sulawesi Tortoises (Indotestudo Forsteni) Caused by a Novel Siadenovirus

A novel siadenovirus was identified in the Sulawesi tortoise (Indotestudo forsteni). A group of 105 Sulawesi tortoises was obtained by the Turtle Survival Alliance. Many of the tortoises were in poor health. Clinical signs included anorexia, lethargy, mucosal ulcerations and palatine erosions of the oral cavity, nasal and ocular discharge, and diarrhea. Initial diagnostic tests included fecal testing for parasites, complete blood count and plasma biochemical analysis, mycoplasma serology, and polymerase chain reaction (PCR) testing for intranuclear coccidia and chelonian herpesvirus. Treatment included administration of antibiotics, antiparasitic medications, parenteral fluids, and nutritional support. Tissue samples from animals that died were submitted for histopathologic evaluation. Histopathologic examination revealed systemic inflammation and necrosis associated with intranuclear inclusions consistent with a systemic viral infection in 35 tortoises out of 50 examined. Fecal testing results and histopathologic findings revealed intestinal and hepatic amoebiasis and nematodiasis in 31 animals. Two of 5 tortoises tested by PCR were positive for Chlamydophila sp. Aeromonas hydrophila and Escherichia coli were cultured from multiple organs of 2 animals. The mycoplasma serology and PCR results for intranuclear coccidia and chelonian herpesvirus were negative. Polymerase chain reaction testing of tissues, plasma, and choanal/cloacal samples from 41 out of 42 tortoises tested were positive for an adenovirus, which was characterized by sequence analysis and molecular phylogenetic inference as a novel adenovirus of the genus Siadenovirus. The present report details the clinical and anatomic pathologic findings associated with systemic infection of Sulawesi tortoises by this novel Siadenovirus, which extends the known reptilian adenoviruses to the chelonians and extends the known genera of reptilian Adenoviridae beyond Atadenovirus to include the genus Siadenovirus.

Partial Discharge Activity of Inter-turn Insulation under Different Parameters of Square Wave Voltage

Partial discharge (PD) activity of inter-turn insulation of electric motor winding is investigated under different parameters of square wave voltage, and the memory effect of deposited space charge in a cavity on PD activity is also studied. Under different frequency and rise time of square wave, discharge number, maximum discharge magnitude and phase resolved PD pattern is investigated. Increase in frequency and decrease in rise time both results in increase in maximum discharge magnitude and discharge number at square wave. Comparing the results of phase resolved PD patterns at different frequency of square wave, most of PD moves to zero point of square wave voltage with the increase in frequency. Meanwhile, with the reduction in rise time of square wave, a similar phenomenon can be observed. Through the analysis of a PD process at square wave voltage, the memory effect of deposited space charge after a discharge in cavity leads to superposition of electric field when the polarity of square wave voltage rapidly reverses. With the increase in frequency and reduction in rise time at square wave, superposition of electric field enhances. As a result, available discharge time prolongs during the rise time of square wave and overvoltage across the cavity increases. They result in the increase in discharge number and maximum discharge magnitude. Furthermore, for this reason, the position of PD shifts to zero point of square wave voltage.

Investigation of Water-Vapor Plasma Excited by Microwaves as Ultraviolet Light Source

The potential of using water-vapor plasmas excited by microwaves as a ultraviolet (UV) light source has been investigated by using various pressures and input powers. The UV irradiation power increased and saturated at a pressure range dependent on the input power. On the other hand, other visible and infrared emissions corresponding to four atomic lines, i.e., the Balmer series of hydrogen at 486.1 nm ( Hbeta) and 656.3 nm (Halpha) and oxygen atoms at 777.2 and 844.6 nm, were clearly decreased with an increase in the total gas pressure. It was found that pressures (1.4-2.0 kPa) near the saturated water-vapor pressure were found to give the most intense UV irradiation. With a vapor pressure of 1.6 kPa and a total microwave power of 300 W, the power density of UV (Gammauv) was measured to be 10.5 muWmiddotcm-2 at a distance of 30 cm from the center of the discharge tube as measured through an optical viewing port on the cavity discharge applicator. This value for (Gammauv) is comparable to that for a mercury lamp. However, the (etauv) efficiency was estimated to be considerably lower than that of a mercury lamp.

Partial discharges in a cavity at variable applied frequency part 1: measurements

In this paper partial discharges (PD) in disc-shaped cavities in polycarbonate are measured at variable frequency (0.01-100 Hz) of the applied voltage. The advantage of PD measurements at variable frequency is that more information about the insulation system may be extracted than from traditional PD measurements at a single frequency (usually 50/60 Hz). The PD activity in the cavity is seen to depend on the applied frequency. Moreover, the PD frequency dependence changes with the applied voltage amplitude, the cavity diameter, and the cavity location (insulated or electrode bounded). It is suggested that the PD frequency dependence is governed by the statistical time lag of PD and the surface charge decay in the cavity. This is the first of two papers addressing the frequency dependence of PD in a cavity. In the second paper a physical model of PD in a cavity at variable applied frequency is presented.

A Novel Structure of Slot-Antenna Array for Producing Large-Area Planar Surface-Wave Plasmas

The principle of surface wave plasma discharge in a rectangular cavity is introduced and the distribution of the electromagnetic field within a rectangular waveguide is analysed. A novel structure of a slot antenna array is presented. In comparison with the traditional slotantenna, it is shown that the designed slot antenna array can excite effectively the surface wave coupling into the chamber, and generate a stable large-area high-density plasma. These results are useful for exploring the optimized design of the slot-antenna for surface wave plasmas.

Characterization of a supersonic microwave discharge in Ar/H2/Air mixtures

Detailed characterization of a microwave cavity discharge in the supersonic flow of Ar/H2/Air mixtures at static pressures of 1–10 Torr and Mach number 2 is mostly based on emission spectroscopy techniques. In the conditions close to real combustion environments, effects of hydrogen and air admixture to plasma parameters and population of excited species in the discharge are demonstrated. The effects resulting in ionization loss are discussed from the aspects of dominant mechanisms and consequences for the plasma assisted hydrogen oxidation.

Reliability of ultra-thin titanium dioxide (TiO 2) films on strained-Si

Ultra-thin high-k titanium oxide (equivalent oxide thickness ~ 2.2 nm) films have been deposited on strained-Si/relaxed-Si 0.8Ge 0.2 heterolayers using titanium tetrakis iso-propoxides (TTIP) as an organometallic source at low temperature (< 200 °C) by plasma enhanced chemical vapor deposition (PECVD) technique in a microwave (700 W, 2.45 GHz) plasma cavity discharge system at a pressure of 66.67 Pa. The trapping/detrapping behavior of charge carriers in ultra-thin TiO 2 gate dielectric during constant current (CCS) and voltage stressing (CVS) has been investigated. Normalized trapping centroid and trapped charge density variation with injected fluences have been investigated and also empirically modeled. Oxide lifetime is predicted using empirical reliability model developed. Dielectric breakdown and reliability of the dielectric films have been studied using constant voltage stressing. A high time-dependent dielectric breakdown (TDDB, t bd > 1000 s) is observed under high constant voltage stress.

Reliability of ultra thin ZrO 2 films on strained-Si

Ultra thin high- k zirconium oxide (equivalent oxide thickness ∼1.57 nm) films have been deposited on strained-Si/relaxed-Si 0.8Ge 0.2 heterolayers using zirconium tetra- tert-butoxide (ZTB) as an organometallic source at low temperature (<200 °C) by plasma enhanced chemical vapour deposition (PECVD) technique in a microwave (700 W, 2.45 GHz) plasma cavity discharge system at a pressure of 66.67 Pa. The trapping/detrapping behavior of charge carriers in ultra thin ZrO 2 gate dielectric during constant current (CCS) and voltage stressing (CVS) has been investigated. Stress induced leakage current (SILC) through ZrO 2 is modeled by taking into account the inelastic trap-assisted tunneling (ITAT) mechanism via traps located below the conduction band of ZrO 2 layer. Trap generation rate and trap cross-section are extracted. A capture cross-section in the range of ∼10 −19 cm 2 as compared to ∼10 −16 cm 2 in SiO 2 has been observed. The trapping charge density, Q ot and charge centroid, X t are also empirically modeled. The time dependence of defect density variation is calculated within the dispersive transport model, assuming that these defects are produced during random hopping transport of positively charge species in the insulating layer. Dielectric breakdown and reliability of the dielectric films have been studied using constant voltage stressing. A high time-dependent dielectric breakdown (TDDB, t bd > 1500 s) is observed under high constant voltage stress.

TiO2/GeOxNy stacked gate dielectrics for Ge-MOSFETs

In this work, we present the results of physical and electrical characterization of Ti-based high-k gate dielectrics on Ge substrates. Titanium tetrakis iso- propoxide (TTIP) was used as the organometallic source for the deposition of ultra-thin TiO2 films on p-Ge (1 0 0) at low temperature (<200 °C) by plasma enhanced chemical vapor deposition (PECVD) technique in a microwave (700 W, 2.45 GHz) plasma cavity discharge system at a pressure of ∼65 Pa. The presence of an ultra-thin lossy GeO2 interfacial layer between the deposited high-k film and the substrate, results in frequency-dependent capacitance–voltage (C–V) characteristics in strong accumulation and a high interface state density (∼1013 cm−2 eV−1). To improve the electrical properties, nitrogen engineering has been employed to convert the lossy GeO2 interfacial layer to its oxynitride, thus forming TiO2/GeOxNy/Ge stacked-gate structure with improved interface/electrical properties. Different N sources, such as NO, NH3 and NO/NH3, have been used for nitrogen engineering. XPS and Raman spectroscopy analyses have been used for surface morphological study. Electrical properties, such as gate leakage current density, interface state density, charge trapping, flatband voltage shift, etc, have been studied in detail for TiO2/GeOxNy/Ge MIS capacitors using the current–voltage (I–V), capacitance–voltage (C–V), conductance–voltage (G–V) and stress (both constant voltage and current) measurements. Although a significant improvement in electrical characteristics has been observed after nitridation in general, the formation of the interfacial GeOxNy layer, obtained from NO-plasma nitridation, is found to provide the maximum improvement among all the nitridation techniques used in this study. It is shown that the insertion of an ultra-thin oxynitride (GeOxNy) interfacial layer is advantageous for producing gate-quality TiO2 high-k dielectric stacks on Ge substrates.

Reactive Oxygen Emission from Microwave Discharge Plasmas

Metastable oxygen atoms and molecules have received increased interest because of their function in surface modification, bio-decontamination and many other industrial applications, in addition to the role in the upper atmospheric layer chemistry. We review work on production and detection of metastable oxygen and we describe our experiments, including the development of techniques for measurement of metastable molecular oxygen. We show that either metastable oxygen molecules or metastable oxygen atoms can be produced in large quantities in electrical discharges, carefully tailored to promote the required kinetics. Although the two species may coexist, colder discharge regimes favor production of molecules, while at higher temperature conditions atomic oxygen prevails. We found that microwave cavity discharges in He/O2 mixtures favor molecular production, but that an arc-seeded microwave torch in air shows preference of atomic production. Result on the specific yield of molecular oxygen in the microwave cavity discharge shows qualitative agreement with the models.

Inguinal Site Infection as a Rare Cause of Secondary Peritonitis: Report of a Case

Many rare conditions may cause secondary peritonitis. Injection site infection as a primary source of peritonitis has not been reported. Case report and review of the pertinent English-language literature. We describe a 39-year-old intravenous drug user who presented with peritonitis. During the surgical exploration, all abdominal organs were intact, but there was an orifice in the pelvic peritoneum that was related to an inguinal site infection. Cultures of both the inguinal area and the peritoneal cavity discharge revealed Staphylococcus aureus. Physicians should be aware of secondary peritonitis induced by self-injection of illicit substances in proximity to the peritoneal envelope.

Electrical properties of SiO 2/TiO 2 high- k gate dielectric stack

The trapping/detrapping behavior of charge carriers in ultrathin SiO 2/TiO 2 stacked gate dielectric during constant current (CCS) and voltage stressing (CVS) has been investigated. Titanium tetrakis iso-propoxides (TTIP) was used as the organometallic source for the deposition of ultra-thin TiO 2 films at low temperature (<200 °C) on strained-Si/relaxed-Si 0.8Ge 0.2 heterolayers by plasma-enhanced chemical vapor deposition (PECVD) in a microwave (700 W, 2.45 GHz) plasma cavity discharge system at a pressure of 66.67 Pa. Stress-induced leakage current (SILC) through SiO 2/TiO 2 stacked gate dielectric is modeled by taking into account the inelastic trap-assisted tunneling (ITAT) mechanism via traps located below the conduction band of TiO 2 layer. The increase in the gate current density observed during CVS from room temperature up to 125 oC has been analyzed and modeled considering both the buildup of charges in the layer as well as the SILC contribution. Trap generation rate and trap cross-section are extracted. A capture cross-section in the range of ∼10 −19 cm 2 as compared to ∼10 −16 cm 2 in SiO 2 has been observed. A temperature-dependent trap generation rate and defects have also been investigated using time-dependent current density variation during CVS. The time dependence of defect density variation is calculated within the dispersive transport model, assuming that these defects are produced during random hopping transport of positively charge species in the insulating high- k stacked layers. SILC generation kinetics, i.e. defect generation probability under different injected fluences for various high-constant stress voltages in both polarities have been studied. An empirical relation between trap generation probability and applied stress voltage for various injected fluences has been developed.

Reduction of Acoustic Waves Induced by Discharge in High Repetition Rate ArF Excimer Laser Cavity to Obtain Narrow-Bandwidth Laser Light

The suppression of acoustic waves caused by discharge in a laser chamber, which is a technical challenge we face in the development of next-generation 6 kHz ArF lasers for lithography, is studied. In this paper, we describe, firstly, that the acoustic waves produced in an ArF laser medium were observed by a Schlieren method and analyzed by computer simulation. The simulation results successfully explained the gas density fluctuation pattern obtained in Schlieren photographs. On the basis of these results, the inner configuration of a laser chamber for 6-kHz-repetition-rate operation was newly designed. The new laser chamber provided narrow-bandwidth laser light up to a repetition rate of 6 kHz as a result of a marked suppression of acoustic waves.