Breakdown Voltage Distributions in Ne-Filled Diode at 1.33 mbar with Corona Appearance in Pre-breakdown Regime

The electrical breakdown of a gas subject to an up-ramping external voltage is studied, experimentally and theoretically, under conditions leading to the appearance of a positive corona at the anode in the pre-breakdown regime. Experimentally, voltage ramps with various rates k in the interval ranging from 0.3 V/s to 26 kV/s are applied to the diode, with the histogram of breakdown voltages being recorded for each rate. The theoretical model gives attention to the pre-breakdown multiplication causing the corona, which tends to reduce the statistical time delay $t_{S}$ before the primary electron is released and hence to make $t_{S}$ comparable to the formative time $t_{F}$ . The multiplication being therefore expected to affect the voltage dependence of the electron yield, a nonlinear equation relating the yield to the overvoltage is introduced. The resulting theoretical expression for the breakdown voltage distribution agrees well with the experimental histograms. Especially noteworthy is the good agreement with the low-voltage tail of the distribution, a segment of the data that has challenged previous theoretical analyses of the problem.     

Dependence of the Breakdown Potential on the Voltage Rise Rate in a Long Discharge Tube at Low Pressure

Technical Physics - We have measured the dynamic breakdown voltage in a long (80 cm) discharge tube in neon, argon, their mixture, and in argon with mercury vapor at pressures of 80–400 Pa in...     

Inter‐Electrode Distance and Breakdown Voltage in Low Pressure Argon Discharges

This work deals with the Paschen law in electrical breakdown of gases at pd values around the Paschen minimum. From the Townsend model, it is possible to deduce theoretical forms of the coefficients in Paschen's law, of which our calculated values are in the range of the tabulated values from the literature. These formulae show that the breakdown voltage must be influenced by the inter‐electrode distance, while the product pd remains a key parameter. This is confirmed by the Paschen curves measured in an argon discharge for inter‐electrode distances varying from 2 to 9 cm (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigation of the Early Multiplication Processes of the Glow Discharge Formation in Neon Filled Diode at 1.33 mbar Pressure

The results of the investigation of the glow discharge time and space development in the neon‐filled diode at 1.33 mbar are presented. The glow is of the diffusion type with saturation current value of 0.2 mA. The temporal development of the light intensity, emitted perpendicularly on the diode axis from many different parts of the diode, is registered. Using this temporal development, the spatial development of the emitted light is examined. Electrically registered (by the oscilloscope) the total current through the diode reaches the saturation for 1.5 ms, which corresponds to the classical presumption of the formative time delay. The prebreakdown current is registered measuring the emitted light from diode gap. The investigation of light shows the increase of excitation in the gap at least 3 ms before any significant current has been registered (I < 1 µA). The negative glow appears in the diode gap near the anode and in the next a few milliseconds covers the cathode indicating the presence of the multiplication processes in the diode. The stationary regime in the diode is established for about 10 ms. Using this detection method, three stages of the discharge formation can be easily distinguished. These results indicate that the prebreakdown processes in the diode gap can be associated with the first stage of the breakdown formation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A Model for Diffuse Breakdown in High Pressure Gases at Homogeneous Electric Field Strengs

A model of the breakdown in high pressure gases is presented taking into consideration the finite voltage rise time at the discharge electrodes and a finite initial charge carrier density in the gap. Several types of breakdown could be distinguished important for several applications. Thus, the range of existence of high pressure laser discharges at a given preionization density and circuit parameters can be calculated. Moreover, the change in the breakdown characteristics of high pressure gases at high temperatures is explained. This behaviour seems to be important for understanding the physical processes in circuit breaker chambers.     

Experimental Analysis on Electrical Breakdown of Acrylic VHB Tape under Quasi-Static and Pulsed Voltage

Technical Physics - The dependence of electrical breakdown on the rate of change of voltage between the electrodes is investigated for VHB4905, a very common polyacrylate adhesive tape produced by...     

Effect of Tensile Stresses on the Breakdown Voltage of Thin Films

Technical Physics - We consider the problem of electric breakdown of external varnish-and-paint coatings of aircrafts. It is shown that the formation of the breakdown channel in the dielectric...     

He-Ne激光器放电点火电压的实验研究

寻找能降低He—Ne激光器点火电压的外加催离剂．实验对He—Ne激光器的点火电压在阴、阳极被可见光照射、低放射源作用于放电管和阴极附近加强电场的条件下进行了测量．对不同外加条件作用下He—Ne激光器点火电压实验数据的误差进行了分析．实验结果指出，用可见光照射阴极或阳极不能降低He—Ne激光器的点火电压；能明显降低点火电压的因素可以是低放射源或外加强电场．     

不同气压下激光诱导击穿Cu合金等离子体光谱自吸收现象研究

采用波长532 nm激光（脉宽为8 ns）诱导激发铜合金等离子体光谱,研究了激光能量分别为100,80,60和40 mJ时,常压下谱线（CuⅠ 324.754 nm）自吸收现象;在激光能量为100和40 mJ的条件下,研究了低环境压力对铜合金等离子体元素发射谱线自吸收现象和谱线特性的影响。结果表明：常压下谱线（CuⅠ 324.754 nm）存在严重的自吸收现象,自吸收程度随激光能量减小而降低。适度降低环境压强,谱线的自吸收程度大大降低,谱线的信背比增大,且在一定的低气压条件下,自吸收现象可以基本消除。在5.0×104 Pa气压下,两种能量下谱线的信背比均达到最大值,分别为8.90和8.66,相对于常压分别增大了11.23和12.62倍,此时谱线强度的相对标准偏差分别为2.9%和1.3%;两种能量下等离子体元素发射谱线的线宽随着气压的下降迅速减小,当气压为5.0×104 Pa时,等离子体元素发射谱线的线宽分别为0.08和0.06 nm,是常压下线宽的19%和20%。研究表明：低压环境能明显提高光谱分析的灵敏度和精密度,使得在分析较高含量元素时允许选择灵敏谱线,为采用LIBS技术准确测定高含量元素提供了有效方法。     

Reflected shock experiments on the equation-of-state properties of liquid deuterium at 100-600 GPa (1-6 mbar)

New laser-driven shock experiments have been used to study the equation-of-state (EOS) properties of liquid deuterium. Reflected shocks are utilized to increase the shock pressure and to enhance the sensitivity to differences in compressibility. The results of these experiments differ substantially from the predictions of the Sesame EOS. EOS models showing large dissociation effects with much greater compressibility (up to a factor of 2) agree with the data. By use of independent techniques, this experiment offers the first confirmation of an earlier observation of enhanced compressibility in liquid deuterium.     

Investigation of the electrical breakdown mechanism in neon at 13.3 mbar pressure using the time delay method

The results of the investigation of electrical breakdown in neon filled diode at 13.3 mbar pressure in function of distances between electrodes (0.1 < d < 20 mm), using electrical breakdown time delay method, are presented in this paper. The Paschen curve, as well as the electrical breakdown time delay mean values, and discharge formative time dependence of distance between electrodes are analyzed. The electrical breakdown time delay distributions and Laue diagrams, both as the functions of the distances between electrodes, were used in consideration. The shapes of the established distributions indicate the complex nature of the discharge formation mechanism. The results also indicate that on the right hand side of the Paschen curve (pd > 15 mbar · cm) the transition regime between Townsend and streamer mechanism of electrical breakdown is dominant.     

Investigation of the Statistical and Formative Time Lags Associated with the Breakdown of a Gas in a Gap at High Overvoltage

The results of an investigation of the statistical behavior of the observational time lag to breakdown in an overvolted sparkchamber are presented as a function of pressure (up to 1350 torr of nitrogen), electrode separation (1 and 2 cm) and percent overvoltage (up to 2800 percent). Rogowski contoured, graphite, brass, and aluminum electrodes have been investigated. Automated diagnostic equipment has allowed the reduction of large amounts of data. The results indicate: 1) the shapes of the distributions are strong functions of pressure, 2) the electron emission rate associated with graphite is an order of magnitude greater than that associated with aluminum and brass, 3) the cathode emission rate is much higher than the "apparent" rate determined from a simple stochastic model, and 4) the formative time (taken as the minimum observed time lag) is an order of magnitude greater than that predicted by the streamer model of breakdown.     

Statistical Property of Breakdown between Electrode and Shield in High-Voltage Vacuum Interrupter

Statistical property of the breakdown between stainless or copper electrode and stainless arc shield is studied by applying (250 × 2000)-?s switching impulses to model vacuum interrupters. Higher breakdown voltages are obtained in negative polarity than in positive polarity. The effective area of breakdown which takes the electric-field distribution on the anode surface into account is introduced to explain the polarity effect of breakdown voltage using Weibull statistics.     

Demonstrating a Decrease in the Breakdown Voltage of a Discharge Gap under the Action of Light

Russian Physics Journal -     

Book Review: Statistical Physics of Fracture and Breakdown in Disordered Systems

Journal of Statistical Physics -     

Breakdown of perturbative QED at the new colliders

It is shown that the radiative corrections to e⁻e⁺ → Zγ arising from QED of order (α/π) are very large. It seems not to be possible to predict the total cross section for this process to within a factor of 2. Methods better than perturbation theory are needed if the process is to be predicted with any accuracy.     

Structural phase transitions and the equation of state of SnTe at high pressures up to 2 mbar

Synchrotron X-ray diffraction studies of the structure of SnTe have been performed at room temperature and high pressures under the conditions of quasihydrostatic compression up to 193.5 GPa created in diamond anvil cells. Two structural phase transitions have been detected at P ≈ 3 and 23 GPa. The first phase transition is accompanied by a stepwise decrease in the volume of the unit cell by 4% because of the orthorhombic distortion of the initial SnTe-B1 cubic structure of the NaCl type. It has been found that two intermediate rhombic phases of SnTe with the space groups Cmcm and Pnma coexist in the pressure range of 3–23 GPa. The second phase transition at 23 GPa occurs from the intermediate rhombic modification to the SnTe-B2 cubic phase with the CsCl structure type. This phase transition is accompanied by an abrupt decrease in the volume of the unit cell by 8%. The pressure dependence of the volumes per formula unit at room temperature has been determined.     

Fluctuation-Coupling of Cathode Cavity Pressure and Arc Voltage in a dc Plasma Torch with a Long Inter-Electrode Channel at Reduced Pressure

Fluctuations of cathode cavity pressure and arc voltage are observed experimentally in adc plasma torch with a long inter-electrode channel. The results show that they have the same frequency of around 4kHz under typical experimental conditions. The observed phase difference between the pressure and the voltage, which is influenced by the path length between the pressure sensor and the cathode cavity, varies with different input powers. Combined with numerical simulation, the position of the pressure perturbation origin is estimated, and the results show that it is located at 0.01-0.05m upstream of the inter-electrode channel outlet.     

大气压直流激励空气等离子体羽发光的时空演化

在针-针电极结构的放电装置中以环境空气作为工作气体,大气压下产生了刷形等离子体羽。尽管使用的是直流电源,但放电发光呈现出脉冲性质,发光脉冲频率几乎不受气体流速的影响,但与电源输出功率成正相关关系。等离子体羽的长度与气体流速或者电源功率成正相关关系。通道出口附近,777.4 nm的氧原子谱线强度分布是非对称的,阴极附近处的谱线强度高于阳极附近处的谱线强度。远离通道出口位置,谱线强度逐渐趋于轴对称分布。电学特性和10 μs曝光高速影像结果表明,空气等离子体羽实际上是由拱形放电丝在远离通道出口的运动过程中叠加而成,同时放电从弧光放电丝向均匀辉光放电转化。