Breakdown Time Delay Research Articles

A system for gas electrical breakdown time delay measurements based on a microcontroller

A new system, called gasmem v1.0, for the measurements of gas electrical breakdown time delay (td), with significantly better characteristics than older systems, has been developed and realized. It is based on the PIC 18F4550 microcontroller and could measure the minimal td of about 1.5 μs with the resolution of 83.33 ns. The relaxation (afterglow) period (τ) could vary from 1 to 232 ms (≈50 days). The successive series of td measurements with various τ could be performed, giving very reliable td data that are stored on the personal computer (PC) hard drive via the USB interface. The td and τ values enable the drawing of memory curves (⟨td⟩ = f(τ)) and the analysis of memory effects in the gases. The randomness of td values measured by the gasmem system for more τ values was tested using the nonparametric Wald–Wolfowitz test showing the stochastic nature of obtained results. The memory curves obtained by this system have shown very high reproducibility. In addition, the system has a capability of operating as a stand-alone system (independently of a PC), with the possibility for the implementation of a touch screen for controlling the system and additional memory (e.g. memory card) for data storage.

Experimental Investigation of Breakdown Voltage and Electrical Breakdown Time Delay of Commercial Gas Discharge Tubes

This article presents the experimental results of DC dynamic breakdown voltage Ub for small voltage increase rates and electrical breakdown time delay td of commercial gas discharge tubes. It was shown that Ub is a stochastic value with Gauss distribution for voltage increase rates ≥2 V/s. In order to determine the static breakdown voltage Us as a deterministic quantity, the mean values of the dynamic breakdown voltage Ub as a function of voltage increase rate k were extrapolated until the intersection with Ub axis using linear fit. The intersection point (for k = 0) correspond to Us value. Additional experiments were performed in order to verify the temperature stability of these components over the wide temperature range from 25 to 250 °C. The experimental results of electrical breakdown time delay are also presented in the paper. Electrical breakdown time delay if often refereed as delay response and it is also very important parameter of gas filled devices. It was shown when the voltage higher then 310 V is applied to those components, the mean value of electrical breakdown time delay td insignificantly varies to the value of relaxation time τ≈1 s, while the breakdown probability is close to one for the voltages higher then 380 V. These facts show that the commercial gas discharge tubes are very reliable for the protection for voltages higher then 380 V.

Modeling of a Ne-Xe-HCl DC Discharge for Excimer Lamp

A mathematical model was developed to describe a DC discharge of a Ne-Xe-HCl for excilamp. To achieve our aims we used a one-dimensional model of the cathode sheath coupled to a zero dimensional model of plasma with the external circuit. The spatial profiles of the electron density, ion density and the electric field were shown to exhibit distinct structures of glow discharge. A current in DC discharge increase in monotonous way until reaching 52 A at 225 ns. The breakdown delay times have been calculated, the plasma breakdown is occurring at 160.75ns. The orders of the values of the electric field (105 V/cm) are a condition of the good operation of the excimer lamp. This model permits us to have a good resolution of the sheath region, and to provide a quantitative analysis of the time evolution of the electrical and chemical discharge properties.

Analysis of statistical nature of electrical breakdown time delay in nitrogen at 6.6 mbar pressure in presence of positive ions and N(4S) atoms

AbstractOn the basis of the mean value of electrical breakdown time delay $ \overline t_d $ and the standard deviation of electrical breakdown time delay σ dependence on the afterglow period τ, the mechanisms which dominantly influence to breakdown initiation in nitrogen were separated. It was shown that the positive ions formed in mutual collision of long‐lived metastable molecules have a dominant role in breakdown initiation for τ values up to 70 ms. The metastable molecules were derived from previous breakdown and discharge. In this case σ ≪ td and the total time delay td is approximately equal to formative time tf which decreases in value with the increase of overvoltage. When positive ions have a dominant role in the breakdown initiation the Gaussian distribution describes data of td ≈ tf very well. For τ > 1 s, N (4S) atoms formed in previous breakdown and discharge, have a dominant role in the breakdown initiation. Then, σ ≈$ \overline t_d $ and Laue's distribution, which is valid for statistical time delay ts, describes td data very well (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A Way for High-Voltage $\mu\hbox{s}$ -Range Square Pulse Generation

In this paper, a new way for high-voltage μs -range quasi-square pulse generation based on a ns source pulser and a chopping spark gap is introduced. The source pulser delivered high-voltage source pulse with front edge at ns range to the chopping gap, and the chopping gap chopped the long flat back edge of the source pulse, so that a quasi-square pulse was formed on a high-impedance load. The breakdown-delay characteristics of the chopping gap, which was the most important, were studied in detail. Results of the experiments showed that when the pulse voltage peaked by the first peaking gap was a little lower than or approximate to the breakdown voltage of the chopping gap, the chopping gap broke down at the back edge of the peaked pulse so that the breakdown-delay time can increase from 30 ns to several μs. The breakdown-delay time of chopping gap is confined to the flat top of the peaked pulse. By using this mechanism of breakdown delay, a quasi-square pulse with pulse width of 1.95 μs, amplitude of 55 kV, and front edge of 22 ns was produced on a 1.15-kΩ load. Repetitive chopping pulses at 0.2 Hz were provided to demonstrate the feasibility of the chopping gap. By contrast to the conventional chopping, four essential conditions were concluded. Based on these results, a controllable trigatron-type chopping gap system is introduced to ensure chopping stability. It provides an important new way for μs-range high-voltage square pulse generation.

Erosion and Lifetime Evaluation of Molybdenum Electrode Under High Energy Impulse Current

One of the factors of the functional life of the electrodes used in pulse current discharge depends on the erosion of electrodes. There are many areas that have not been investigated and many areas that require additional study. Some studies have presented results related to the erosion of electrodes made of Cu, Cu–W, Ti, graphite, stainless steel, etc. There is little information available on the erosion of molybdenum electrodes. The erosion of electrodes is related with the electrode material (conductivity, melting point, and density) and the Coulomb charge transferred per impulse. In this paper, molybdenum (Mo) was selected as the main electrode material, considering these factors in addition to high erosion resistance due to high work function and better formability. The performance of pulse discharge devices is mainly characterized by static breakdown voltage, prebreakdown voltage, recovery time, delay time, jitter, and reliability. The degradation of these performance parameters (PPs) is related to many critical factors affecting electrode erosion, consisting of peak current, electrode material, electrode geometry, electrode surface roughness, and gas type. The degree with which the electrode-erosion factors (EEFs) affect the PPs of the pulse discharge device relatively varies and has complex interrelationships, and the relative importance weight of each EEF in order to maximize the life of the pulse discharging device is calculated using quality function deployment and analytic network process methodology. This paper presents experimental work carried out to investigate the erosion characteristics of a molybdenum electrode. Testing was performed at 10–11-kA current discharge every 35 s at a rate of 300 discharges per day with a total of 10 000 shots. The experimental results for Mo electrodes indicate approximately 60 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu \hbox{g/C}$</tex></formula> for 5000-C transfers. For 10–11-kA current transfer with Mo electrodes, we can take about <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$8.5 \times 10^{5}$</tex></formula> shots with wear of 0.3 g without appreciable local wear.

The influence of additional electrons on memory effect in nitrogen at low pressures

Memory effect in nitrogen based on experimental data of electrical breakdown time delay as a function of afterglow period in the presence of additional electrons has been investigated. The additional electrons were supplied as a result of extraction from the auxiliary electrode pair or nitrogen irradiation with the radioactive source of low activity. The results show that these electrons have an important role in the recombination of positive ions formed in mutual metastable molecules' collisions and collisions between metastable and highly vibrationally excited molecules in the early afterglow. As a consequence of the ion–electron recombination N(4S) atoms are formed which, as well as N(4S) atoms formed in previous discharge, have a significant influence on the memory effect in late afterglow. The presence of N(4S) atoms in the late afterglow is tracked by monitoring the secondary emission which they induce via catalytic recombination on the cathode of a nitrogen-filled tube. Also, it has been shown that the contribution of secondary electrons which originate from N(4S) atoms and Compton electrons when the radioactive source is and isn't present can be distinguished.

Investigation of the delay time distribution of high power microwave surface flashover

Characterizing and modeling the statistics associated with the initiation of gas breakdown has proven to be difficult due to a variety of rather unexplored phenomena involved. Experimental conditions for high power microwave window breakdown for pressures on the order of 100 to several 100 torr are complex: there are little to no naturally occurring free electrons in the breakdown region. The initial electron generation rate, from an external source, for example, is time dependent and so is the charge carrier amplification in the increasing radio frequency (RF) field amplitude with a rise time of 50 ns, which can be on the same order as the breakdown delay time. The probability of reaching a critical electron density within a given time period is composed of the statistical waiting time for the appearance of initiating electrons in the high-field region and the build-up of an avalanche with an inherent statistical distribution of the electron number. High power microwave breakdown and its delay time is of critical importance, since it limits the transmission through necessary windows, especially for high power, high altitude, low pressure applications. The delay time distribution of pulsed high power microwave surface flashover has been examined for nitrogen and argon as test gases for pressures ranging from 60 to 400 torr, with and without external UV illumination. A model has been developed for predicting the discharge delay time for these conditions. The results provide indications that field induced electron generation, other than standard field emission, plays a dominant role, which might be valid for other gas discharge types as well.

Generation of Liquid-Cathode Atmospheric Pulsed Microdischarges Assisted with a DC Discharge

We discuss the reduction of the amplitude of repetitive pulsed voltages to generate atmospheric-pressure microdischarges with a liquid cathode. The pulsed voltage was applied to a low-current DC glow discharge in a nozzle-to-liquid electrodes system. The pulsed microdischarges were operated at a voltage of less than 2.2 kV. The delay time of breakdown for the pulsed microdischarges increased with repetition frequency. At high repetitive operation, the liquid surface under the nozzle electrode deformed.

Numerical simulation of outgassing in the breakdown on dielectric surface irradiated by high power microwave

A simple outgassing model for dielectric surface breakdown due to the high power microwave (HPM) irradiation was establised. By using the PIC (particle-in-cell)-MCC(Monto Carlo collisions) method, the numerical simulation program of the dielectrics surface breakdown was developed, and the simulation of breakdown for different outgassing speeds was performed. The temporal evolution of the electron number and delay time of the process of breakdown in the case of different outgassing speeds were obtained. The numerical results show that when the speed of outgassing is small, the breakdown does not occur for an HPM pulse of a given duration, because the formation of the gas layer on the dielectric surface is slow. When the speed of outgassing is greater than a certain value, the breakdown occurs and the breakdown delay time shortens with the gas desorption rate increasing in a certain range. Finally, the numerical simulation results were compared with the experimental results of the direct current dielectric surface breakdown, and the trends of their development agree very well.

New models and distributions of the electrical breakdown time delay in neon

The measurements of the electrical breakdown time delay td for a wide range of working voltages and at different preionization levels are presented. The statistical breakdown time delay ts and the discharge formative time tf are experimentally separated and theoretical models of their dependencies on the overvoltage and number densities of residual charges during relaxation are suggested. Several empirical and semiempirical models are used to describe the formative time delay dependence on working voltages tf (U). The empirical and theoretical models from the literature are also applied to the experimental data, without and with empirical corrections. Moreover, several new distributions are experimentally obtained: Gauss-exponential, Gaussian and double Gaussian ones for the statistical time delay, as well as Gaussian and double Gaussian distributions for the formative time. The measurements of the breakdown time delay at different preionization levels (afterglow periods) td (τ) obtained with a galvanic layer of gold and a sub-layer of nickel on the copper cathode are compared to the measurements with a vacuum deposited gold layer on the cathode surface. It was found that the surface charges retaining on a galvanic layer of gold influence the breakdown time delay which leads to double Gaussian distributions of the formative and statistical time delay.

Electrical breakdown in nitrogen at low pressure – physical processes and statistics

The results of investigation of the electrical breakdown in nitrogen, obtained in combined approach based on measuring of the current-voltage characteristic and statistical analysis of the breakdown time delay are presented in this report. Measurement of the current-voltage characteristics with additional monitoring of spatial and temporal distribution of the emission from discharge provides information concerned on development of different regime of low-pressure gas discharge and on processes of the electrical breakdown and discharge maintenance. Also, two new distributions of the statistical time delay of electrical breakdown in nitrogen, the Gaussian and Gauss-exponential ones, are presented. Distributions are theoretically founded on binomial distribution for the occurrence of initiating electrons and described by using analytical and numerical models. Moreover, the correlation coefficient between the statistical and formative time delay of electrical breakdown in nitrogen is determined. Starting from bivariate normal (Gaussian) distribution of two random variables, the analytical distribution of the electrical breakdown time delay is theoretically founded on correlation of the dependent statistical and formative time delay.

Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices

This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.

Breakdown probability of neon under the influence of field electron emission and surface charges on the cathode surface

Improved relations are suggested to determine of the breakdown probability in neon under the influence of field electron emission and surface charges on the gold plated cathode surfaces. The influence of field electron emission from a vacuum deposited gold layer is confirmed by the Fowler–Nordheim plot based on an analysis of the breakdown time delay dependence on the voltage td¯(U). Surface regions with a reduced conductivity on a hard galvanic layer of gold caused by diffusion of nickel atoms from a nickel sublayer are confirmed by scanning electron microscopy and energy dispersive x-ray spectrum.

One-pulse driven plasma Pockels cell with DKDP crystal for repetition-rate application

Pockels cell (PPC), which can use a thin crystal to perform the uniform electro-optical effect, is ideal component as average-power optical switch with large aperture. In this paper, the key problems in PPC are analyzed for repetition-rate application, and thermo-optical effects are simulated by means of numerical modeling when average power is loaded on the electro-optical crystal. By reformative design and employing a capacity to share the gas discharge voltage, the DKDP PPC driven by one pulse is realized. As gas breakdown delay time is stable, and discharge plasma is uniformly filled the full aperture, it meets the demand of plasma electrode for the repetition-rate PPC with DKDP crystal. The switch efficiency of PPC at the whole aperture is better than 99%.

Method of Improving Cathode Surface

We suggest a method of controlled improvement of cathode surface quality by high-voltage pulses in a vacuum. This method includes surface inspection, pulse amplitude calculation, and pulse action with predetermined amplitude upon a vacuum gap cathode. The cathode surface is controlled by the electric field intensity amplification factor beta at the cathode microinhomogeneities. The pulse amplitude is calculated from specific pulse duration and the beta-factor. The amplitude is calculated so that the pulse duration is equal to the breakdown delay time. By applying a series of pulses which have the same duration as the breakdown delay time, the cathode surface can be improved to have smaller beta-factor values with a minimum of high voltage pulses required to achieve maximum surface quality. This method is experimentally verified for both all-metal and spray-coated film electrodes of electronic devices. It is shown that a significant decrease of beta-factor results from the application of 3 - 5 high voltage pulses using this method.

Fluctuations and correlations of the formative and statistical time delay in neon

The fluctuations and correlations of the formative tf and statistical time delay ts in neon are studied by electrical breakdown time delay measurements. The measurements were carried out at different preionization levels (afterglow periods) and the Gaussian distributions for the formative time were obtained to about 20 ms in afterglow. The formative time increases linearly with the afterglow period consistently with an exponential decay. After that, double-Gaussian (bi-normal) distributions for the formative time were obtained corresponding to and decay. For the statistical time delay Gaussian, Gauss-exponential and exponential distributions were obtained. It was found that the formative and statistical time delay are dependent variables for ts < tf and their correlations are estimated. The linear correlation coefficient is ρ ≈ 1 at high electron yields (rates of electron production) and ρ ≈ 0 at low electron yields.

Modelling of time delay of electrical breakdown for nitrogen-filled tubes at pressures of 6.6 and 13.3 mbar in the increase region of the memory curve

Experimentally measured electrical breakdown time delay data versus the afterglow period (representing ‘memory curves’) for nitrogen-filled tubes at pressures of 6.6 and 13.3 mbar have been shown. The influence of N(4S) nitrogen atoms on secondary electron emission from the cathode (the SEE process) in late afterglow has been discussed. N(4S) atom concentration decay over relaxation time τ, N(4S)(τ), has been analysed by a numerical model and two analytical models. N(4S) decay analytical models are combined with different yield models that describe the SEE process by N(4S) and these combinations are employed to fit the experimental data. It has been shown that in late afterglow solving of very simple analytical equations instead of numerical solving of partial differential equations for N(4S)(τ) fitting can be used and that the combination of the first and the second order of the SEE process by N(4S) in yield modelling should be used in the case of 13.3 mbar pressure.

Breakdown Delay Times for Subnanosecond Gas Discharges at Pressures Below One Atmosphere

With a RADAN 303-A pulser (a rise time of 150 ps and a maximum voltage of 150 kV into matched load), fast breakdown in argon and air is investigated. An oil-filled coaxial transmission line is coupled with a lens to a biconical section and a radial millimeter-size gap operated at subatmospheric pressure. Diagnostics include capacitive voltage dividers which allow the determination of voltage across and current through the gap with a temporal resolution defined by the digitizer (20 Gs/s, 6 GHz) used. A scintillator-photomultiplier combination with different metal absorber foils and a temporal resolution of 2 ns is used as X-ray detector to obtain a rough energy spectrum of the X-rays and electrons in the range of 10-150 keV. Discharges are characterized by runaway electrons over much of the pressure range, with a strong excitation and ionization layer at the cathode surface, and ldquofree-fallrdquo conditions with negligible gaseous ionization for the rest of the gap. High-energy electrons (> 60 keV) are observed up to atmospheric pressure. Time-to-breakdown curves versus pressure have been measured for different applied voltage rise times. They resemble Paschen curves with a steep increase toward low pressure and a slow increase toward high pressure. The major experimental findings and particularly the time-to-breakdown curves are confirmed using simple force-equation modeling. Monte Carlo calculations simulating collisional ionizations and developing electron avalanches in three dimensions have been used to verify and explain the experimental results.

Method for increasing quality of the cathode surface of a vacuum gap

A method for controlled processing of the cathode surface in vacuum has been developed. The control is effected in a steady-state regime by monitoring the amplification factor of the electric-field strength at cathode microinhomogeneities. High-voltage pulses of nanosecond durations with amplitudes ensuring a breakdown delay time equal to the duration of the applied pulse, td = tp, are used to affect the surface. This method allows the surface quality to be substantially improved after application of a minimum number of pulses. The application of five pulses at tp = 10 ns with amplitudes ensuring the condition td = tp to stainless-steel electrodes results in a decrease in the field-amplification factor by a factor exceeding 5 (from 136 to 26) and in an increase in the emission area by more than four orders of magnitude (from 4.6 × 10−19 to 10−14 m2).