Dependence Of Discharge Current Research Articles

Оценка тока разряда и извлекаемого тока из пеннинговского ионного источника

A Penning ion source for a miniature linear accelerator is investigated. A discharge current dependence on the anode voltage for several pressure values is calculated. The estimates are based partly on simplified theoretical models, partly on experimental data obtained on previous work. The ion current component is selected from the obtained dependences and the ion current component value, extracted from the ion source, is estimated. The extracted current dependences and the ion extraction efficiency coefficient value on the voltage at the anode at different source output aperture diameters are calculated.

The Characteristics of Closed-Loop Inductively Coupled Low Mercury Pressure Discharge

The characteristics of inductively coupled ferrite-free low mercury pressure discharges generated in closed-loop 815-mm-long quartz tubes 16.6 mm in diameter are studied. Discharges were excited at a frequency of 13.56 MHz with plasma power ranging from 10–270 W in a mixture of mercury vapor (~0.01 Torr) and argon (0.5, 1.0 and 2.0 Torr) by means of an induction coil placed over the discharge tube wall external perimeter. With a growth of plasma power, the lower the argon pressure, the faster the growth rates of the RF voltage across the induction coil and the current through it. The plasma impedance as a function of plasma power calculated within the framework of the inductively-coupled discharge transformer model has a minimum, which shifts toward higher plasma power values with increasing the argon pressure. The lower the argon pressure the higher the RF electric field averaged over the plasma cross section, and the lower the plasma power at which the dependence of discharge current on plasma power reaches its maximum.

The Characteristics of Closed-Loop Inductively Coupled Low Mercury Pressure Discharge

The characteristics of inductively coupled ferrite-free low mercury pressure discharges generated in closed-loop 815-mm-long quartz tubes 16.6 mm in diameter are studied. Discharges were excited at a frequency of 13.56 MHz with plasma power ranging from 10–270 W in a mixture of mercury vapor (~0.01 Torr) and argon (0.5, 1.0 and 2.0 Torr) by means of an induction coil placed over the discharge tube wall external perimeter. With a growth of plasma power, the lower the argon pressure, the faster the growth rates of the RF voltage across the induction coil and the current through it. The plasma impedance as a function of plasma power calculated within the framework of the inductively-coupled discharge transformer model has a minimum, which shifts toward higher plasma power values with increasing the argon pressure. The lower the argon pressure the higher the RF electric field averaged over the plasma cross section, and the lower the plasma power at which the dependence of discharge current on plasma power reaches its maximum.

Temperature Compensation With Highly Integrated Ionization Sensor Array Used in Simultaneous Detection of Mixed Gases

On-line detection of fault characteristic gases released by the insulation oil of transformers is developed as a scientific basis for estimating explosion accidents. However, the performance of most gas sensors, such as H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> sensors, is usually affected by temperature, and there exists large detection error when the temperature of transformer oil changes in operation. And the existing temperature compensation methods suffer from problems such as low integration, large volume, and high costs. Herein, a sensor array based on three triple-electrode sensors with carbon nanotubes was fabricated. Each of the three sensors has three vertically stacked electrodes with various interelectrode distances. The first and second sensors were used to detect H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , respectively, and the third sensor was used to measure temperature. All the detection mechanisms are based on the dependence of discharge current on gas concentration and temperature. The sensor array could detect H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> mixture and temperature due to the exponential function between the output currents and electrode separations. The proposed sensor exhibited low relative and repeatability error values less than 5.1% and 4.9%, respectively, and displayed humidity compensation potential like temperature. High integration makes the sensor array superior among the other mechanism sensors.

The Current–Voltage Characteristics of Corona Discharge in Wire to Cylinder in Parallel Electrode Arrangement

Corona discharges are currently increasing in importance due to the wide range of applications in which they are involved. As the performance of the corona discharge is related to the operational conditions of the devices where it is used, the corona discharge current dependence on controllable parameters must be well understood. A series of measurements for positive and negative corona varying the distance between the electrodes was carried out for wire to cylinder in a parallel configuration. The experimental data were examined by using two empirical formulae, showing that the two expressions hold for both polarities. The empirical formulae have estimated current with the mean relative error less than 3% for positive corona and 6% for negative corona. Furthermore, the inception voltage and the dimensional parameters dependencies on the distance were also investigated, indicating that both are proportional to the exponent of the electrode gap. The validity of a prediction model to estimate the corona discharge current for a larger gap of 40 mm was also observed. Finally, a propulsion application of the derived equations was studied for positive and negative polarities. The investigation provides useful information about corona discharges for wire to cylinder in the parallel configuration, which could be used in applications such as propulsion systems.

Pressure and discharge current dependence of production rate of single-walled carbon nanotubes by the bipolar pulsed arc-discharge method

ABSTRACTBipolar pulsed arc-discharge method has been studied for the efficient production of high quality single-walled carbon nanotubes (SWNTs). Gas pressure and discharge current dependence of this method has been carried out to obtain the optimum production condition. The experimental results show no cathode deposition, and almost all the sublimated carbon becomes soot containing SWNTs. The production rate increases with increasing gas pressure and discharge current. The high production rate with high quality SWNTs is obtained around the conditions of helium gas pressure, p (He) = 50 – 70 kPa and discharge current, Id ≃ 55 A. The morphology of the SWNTs is measured by a TEM and the quality is analyzed by a Raman spectrometer.

Validation of Numerical Model of Penning Gas Discharge based on 2D/3V PIC-MCC Method

The data obtained in the experiments conducted in University of California, Berkley are used to validate numerical model of Penning gas discharge. Numerical model is based on 2D/3V axisymmetric electrostatic particle-in-cell method implemented on unstructured grids. Elementary processes in the gas discharge plasma are simulated using Monte-Carlo collision method. Electrodynamic structure of the Penning gas discharge is obtained using mentioned numerical model under conditions relevant to experimental and analyzed. Distributions of the potential, electric field, electrons and ions number densities, temperatures, distribution functions are presented in the study. Validation of numerical model is performed by comparison of the dependence of discharge current on applied magnetic field.

High Density Fluorine Negative-Ion Source Generated by Utilizing Magnetized SF&amp;lt;sub&amp;gt;6&amp;lt;/sub&amp;gt;

In a magnetized plasma column generated from an electronegative gas, negative-ions accumulate around the plasma column via radial diffusion. In this study, a dc discharge is applied in SF6 gas to produce a plasma column, and the radial density profile of negative-ions is measured by Langmuir probes using the modified Bohm criterion. The gas pressure and discharge current dependences of negative-ion density are also measured. It is found that the negative-ion density of 8.0 × 1017 m-3 is obtained around the plasma column at r = 1.0 cm when SF6 pressure is 0.13 Pa and discharge current is 0.50 A. The negative-ion density has radial gradient, and the electron density is much lower in this region.

The development and analysis of plasma microfluidic devices

Microfluidic devices were studied here to determine the potential for lab-on-a-chip applications based on the dielectric barrier discharge (DBD) mode of activation. This type of discharge is usually formed between two parallel electrodes, with a separation between 0.1 and 1mm, where one or both electrodes are covered with a dielectric barrier. Different working conditions were considered: A sinusoidal voltage of up to 9kV peak to peak with frequencies from 10kHz to 40kHz has been applied to the electrodes imbedded in PDMS layers. The micro channel width was maintained at 50 and 100μm, and the pressure was varied between 35kPa and 103kPa above atmospheric pressure, using helium, neon and nitrogen gases respectively, for the formation of the microplasma discharges. This generated micro discharge currents in the range of 0.1 to 12mA at a flow rate of 0.012lmin−1, and can be seen as current filaments of about 100ns duration on the time resolved electrical waveform. Current–Voltage (I–V) measurement results obtained show a sharp peak in the discharge current at the breakdown voltage. Results also confirm the dependence of discharge current on frequency, gas composition, microchip geometry and flow rate.

One-Dimensional Fluid Simulation of Atmospheric-Pressure Helium DC Glow Discharges

Atmospheric-pressure glow discharges (APGDs) have been widely used for material processing such as etching, deposition and surface modification and biomedical applications because of the material processing without thermal damage, discharge uniformity over the large area, and so on. In order to suitably utilize APGDs for these applications, further understanding of fundamental properties in APGDs is strongly required. In this paper, the APGDs in helium produced by DC power supply have been simulated using a spatially one-dimensional fluid model. The structure of discharges can be distinguished into five specific regions: a cathode fall, a negative glow, a Faraday dark space, a positive column, and an anode fall. The structure is similar to that of typical low-pressure dc glow discharges. Reasonably good agreement between measured and calculated current-voltage characteristics can be obtained in the present current range (∼10 mA). The discharge-current dependence of the spatial structure, and the mechanism of gas-heating and power-consumption are also discussed.

Positive dc corona between coaxial electrodes in mixtures of carbon dioxide and oxygen

The positive corona discharge has been generated in a reactor equipped with a system of stainless steel cylindrical coaxial electrodes. The discharge has been fed with mixtures of carbon dioxide and oxygen (0–100% of oxygen) in flow-stopped regime. The time dependence of discharge current has been measured for a period of 1 h. The effect of the mixture composition on the discharge current and the onset voltage of the discharge has been investigated. A slight increase in the onset voltage was observed with increasing amount of oxygen in the gas mixture up to 20% of oxygen, where the maximum was reached. Then, with further increase of oxygen concentration, the onset voltage decreased. These results correspond to the measured discharge currents. The lowest currents were observed for a mixture containing 20% of oxygen, where the onset voltage is highest, and the highest currents were observed for pure oxygen, where the onset voltage is lowest. These observations are in agreement with Townsend's formula expressing the current–voltage characteristics of the discharge.

Relaxation of atomic state multipoles by radiation re-absorption: Neon [formula omitted] atoms in a discharge plasma

In a positive column of a glow discharge in the magnetic field of 36.4 G, a linearly polarized laser pulse or a circularly polarized laser pulse has produced polarized neon atoms (alignment or orientation) in the 2 p 2 (Paschen notation) level from the 1 s 3 level. The subsequent fluorescence to the 1 s 2 level was observed with its polarized components resolved. Depopulation, disorientation and disalignment rates of the 2 p 2 atom were measured and their discharge current dependences were examined for a discharge current from 0.4 to 2.0 mA. The degrees of radiation re-absorption, or the optical thickness, of the transition lines from the 2 p 2 level to the 1 s 2 - 1 s 5 levels were measured as functions of the discharge current. A Monte Carlo simulation was performed by which the depopulation, disorientation and disalignment rates by the radiation re-absorption for these transitions were determined. The calculated rates were compared with the observed ones and found to reproduce the their discharge current dependences. D’Yankonov and Perel's analytical expression for these rates was quantified from comparison with the Monte Carlo results.

Heat capacity of liquid hafnium from the melting point to the boiling point at atmospheric pressure

The spectroscopic and probe methods are used to measure the microscopic parameters of plasma of pulsed and stationary transverse discharges in a supersonic air jet flowing into a submerged space. The measurements are performed for the Mach number of flow M = 2, submerged space pressure p = 5 to 30 kPa, degree of the jet being off-design n ∼ 2, and discharge current I = 1 to 10 A. The discharge current dependences of the average values of gas temperature, charged particle concentration, and reduced electric field are measured for a discharge mode close to that of current generator. The measured values of gas temperature lie in the range of 1 to 3 kK, those of charged particles concentration — of 1013 to 1014 cm-3 , and of reduced electric field — of 40 to 20 Td. The axial distribution of temperature is characterized by high values of temperature even at short distances from the electrodes and by a slow decrease along the flow.

Optical emission diagnostics of the linear magnetron sputtering discharge

Spectroscopic study of properties of plasma produced in a new type of d.c. planar magnetron sputtering system—linear magnetron, with a titanium cathode and argon–nitrogen mixtures are presented here. High energy species (Ti, Ar, Ar+, N2, N2+, TiN) have been identified in plasma. Optical emission spectroscopy data were obtained showing the effects of operating parameters (pressure, current, argon percentage in Ar–N2 gas mixture, axial position) on emission intensities of the species. In particular, the discharge current dependence of the emission intensities have been determined. Electron excitation temperatures were calculated from argon and titanium atomic lines. The results were used to characterize the excitation and ionization processes as well as sputtering conditions in the linear magnetron sputtering device.

Recent DOE Sponsored Electrochemical Capacitor Test Results

ABSTRACTElectrochemical capacitors (ultracapacitors) are being developed for hybrid vehicles as candidate power assist devices for the fast response engine and for other energy storage systems that can utilize the high power densities available from these devices. Ultracapacitors show promise toward being able to accept high regenerative pulses and high power delivery capabilities while exhibiting very high cycle life. This paper will present recent test data from two U.S. Department of Energy (DOE) supported ultracapacitor projects designed to meet the fast response engine requirements. Constant-current and constant-power test results will be presented that have been acquired from recent prototype capacitors supplied by SAFT America, Inc. (ten devices), and Maxwell Energy Products, Inc. (two devices). The SAFT capacitors are rated at 0.5 V to 3 V with capacitance ratings ranging from 135 F to 138 F. Capacitor cells rated at 2.3 V and 101.4 F were also evaluated that were produced by Maxwell Energy Products, Inc. Both sets of devices used proprietary carbon electrodes with non-aqueous electrolytes in their design. From the constant-current discharge tests, the discharge current dependence of the capacitance, equivalent series resistance, and RC-time constant were determined as well as the capacitors’ voltage dependence of the capacitance. Constant-power discharge tests permitted the specific energy as a function of the specific power to be determined, and also the discharge/charge round trip efficiency as a function of the magnitude of the constant-power discharge.

The spatial profiles of charged particles in a multipolar magnetically confined Ar- plasma

The spatial profiles of charged particles in multipolar magnetically confined Ar- plasmas produced by dc discharges are investigated by varying the total pressure from 2 to 10 mTorr, the discharge current from 10 to 90 mA and the oxygen content from 4 to 20%. The measured spatial negative ion and electron density profiles, which are approximated as a parabolic distribution and a uniform one except in the vicinity of the chamber wall, respectively, allow us to divide the entire discharge into three regions: (i) an electronegative region, (ii) an electropositive region and (iii) the sheath. The ratio of the negative ion density to the electron density measured at the centre increases with increasing oxygen content and pressure, but decreases with increasing discharge current. Oxygen content- and discharge current-dependences of the electronegative region's length are similar to those of the ratio, although the length does not strongly depend on the pressure. A global model, in which the flux balance equations for charged particles and a power balance equation for electrons are taken into account, to estimate plasma parameters such as the individual charged particle density and electron temperature is proposed, and then compared with the experimental results.

Measurement of the lifetime of the copper metastable state in a steady-state discharge using saturated absorption spectroscopy

A new method using saturated laser absorption spectroscopy was developed to determine the lifetime of metastable states in a steady-state discharge. The lifetime of the metastable Cu 4s 2 2D so13 2 state in d.c. hollow cathode discharge was measured as a function of the discharge current. The observed lifetime is much shorter than is expected for the diffusion loss process and the short lifetime was ascribed to the electron collisional destruction process. The discharge current dependence of the lifetime and the density of the Cu 4s 2 2D so13 2 state was consistent with this conclusion.

Test results for a sputter-ion pump with a new cell structure

A test model of a sputter-ion pump using a new cell structure was fabricated, where the magnets reside within the Penning cell assembly. The magnetic field intensity in the cell, pressure (P) dependence of discharge current, and pumping speed are measured. An axial magnetic field larger than 700 G is created inside the cells using commercial magnets with a remanent magnetism of 12 kG. The discharge current (I) is proportional to P1.0–P1.6 in the measured pressure range from 7.5×10 −9 to 1×10−6 Torr. Pumping speed for nitrogen is proportional to P0.6 on the average in the pressure range from 2×10−8 to 1×10−6 Torr and can be written as 0.05 I/P for P≥1×10−7 Torr. The test model is almost less than a half, in both volume and weight, compared to conventional ion pumps with almost the same nominal pumping speeds. It was confirmed experimentally that the new cell structure has the possibility of becoming a compact and light ion pump. The problem remains to optimize the cell sizes to moderate the pressure dependence of the discharge current, i.e., the pumping speed.

Discharge Current Dependences of Laser Parameters of Regular and Sequence Band Transitions of CO2

From gain measurement, laser parameters such as rotational temperature, inversion densities, absolute population densities, and excitation and deexcitation rates are determined as functions of the discharge current. The rotational temperature is well defined in both bands and is very close to the gas translational temperature. It is found by rate equation analysis in an ordinary discharge condition, the rates of excitation to the lower laser levels are much larger than those to the upper laser levels. The deexcitation rates of the lower laser levels are evaluated and found to be the most important processes in maintaining the laser gain in both bands.

QSPA Kh-50 full-scale high-power asistationary plasma accelerator

Abstract A full-scale high-power two-stage quasistationary plasma accelerator with active anode and cathode transformers (QSPA Kh-50) is described. Plasma streams with the velocity (4 to 4.2) × 107 cm/s, the energy flux density above 1 kJ/cm2 in the vicinity of the plasma stream axis and the total energy content in plasma of approximately 250 to 270 kJ were produced. Some integral functional relations obtained under QSPA Kh-50 operation (e.g., the current-voltage characteristic, Ud ≃ 1 2.8 d ; the discharge current dependence of the plasma velocity v ≃ 1 β d, 1.5 < β < 2.5; the time dependence of the velocity of certain plasma stream layers v(t)≃ 21/2 CA 0 = H0 /(2πρ)1/2; the effect of the screening magnetic fields in the cathode and anode transformers on the plasma stream velocity value, etc.) support, for the most part, the concept of a QSPA.