Multichannel closing switch for water energy stores

This paper describes a megavolt closing spark gap switch designed to switch water energy stores in pulse power generators. A peculiarity of the closing spark gap switch is the multichannel regime of the current flow in all discharge gaps that prolongs the lifetime of the switch, decreases its inductance and resistance, and finally, reduces the losses of the stored energy transfered to a load. Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 91–99, December, 1999.     

平面火花隙三电极开关研制及性能测试

 研制了一种适用于平行板传输连接的平面火花隙三电极开关，开关正负电极为半圆形状，触发电极为细条状。将之替代立体式（半球形电极）火花隙三电极开关并应用于爆炸箔起爆装置中，装置回路参数将得以优化。实验测试了空气间隙为4.12， 3.14和2.2 mm的平面火花隙三电极开关的性能。结果表明，在开关间隙间距一定的情况下，随着电压的升高，开关间隙的放电时延和分散时间呈指数降低，开关电感小于15 nH；对于不同范围内的应用电压，使用不同间隙间距的开关，其分散时间不大于10 ns。该开关应用于较低充电电压（小于10 kV）的脉冲功率装置中，与立体式火花隙三电极开关相比，回路电感降低了约50 nH，放电周期缩短近1/3，峰值电流增加约1/3。     

An Innovative Simple Method for Study of the Characteristics of the Trigatron Plasma Switch

A simple Semi‐Analytical method used to fit the experimentally recorded current of the closed switch discharge circuit into the free running under damped LC oscillator model and the arc plasma conductivity, electron density of the plasma and efficiency of the spark gap switch energy transfer have been driven from the model by some simple calculations. The charging voltage, switch pressure and the spark gap has been changed between 6 to 15 kV, 1 to 1.5 bar and 1.4 or 2.8 mm, respectively. The obtained values for plasma conductivity and electron density of plasma are (5‐25)(Ω mm)^–1, (0.5–3.5)·10²⁴m^–3, respectively. The efficiency of the switch is plotted Vs. Pd and E/P which in both cases the peak value has been about 80 present.     

Expansion of spark channels in air and possibilities of plasma crowbar in high pulsed current and magnetic field technique

The radial expansion velocities and diameters of spark channels in air are measured by the plasma-metal contact method. An LC discharge circuit with energy up to 50 kJ and with current frequencies ranging from ∼10² to ∼10⁴ Hz served as the source of the channels. It is concluded on the basis of the results obtained that the previously proposed automatic plasma crowbar based on the expansion of spark channels in gases is a universal switch for an inductive load in LC discharge circuits that could find very wide applications in high pulsed current and magnetic field technology. Zh. Tekh. Fiz. 68, 133–136 (February 1998)     

Investigation of some versions of the pos-load transmission line

Experiments on switching current into an inductive load with a plasma opening switch have been performed. The geometry of the transitory region between the plasma opening switch and the load for which complete switching of current is possible has been determined experimentally. It has been demonstrated that a decrease in the electrode gap spacing in the transmission line results in shunting of the load and reclosure of the switch. Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 20–25, December, 1999.     

Critical Parameters of the Pumping Scheme of Ar+8 Lasers Excited by Z Pinches in Long Capilaries

The present study is focused on the demonstration of the most critical parameters of the pumping scheme of a table‐top Ar⁺⁸‐laser excited by discharges with relatively low current and voltage (I ≤ 20 kA, U ≤ 200 kV) in long (L ～ 0.5 m) capillaries. The most critical parameters of the pumping scheme were analyzed and then adjusted experimentally. The table‐top size is attributed to the use of a low‐inductance co‐axial discharge configuration that decreases the voltage and current necessary for laser excitation. Low inductance is achieved by using a capillary, water‐capacitor and water spark‐gap placed into a chamber filled with deionized water. The capillary z‐pinch is produced by the water capacitor, which is pulse‐charged by a six‐stage Marx generator, optimized for the low‐inductance discharge configuration. Optimization is performed by adjusting the value of the charging inductance and the peak charging voltage with a water spark‐gap. At the optimal conditions laser pulses with a Gaussian‐like intensity distribution and divergence angle ～ 1 mrad and energy ～ 10 μJ are generated. The physical method for generation of a laser beam with such parameters is based on the use of a long (L = 0.45 m) capillary plasma (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

微型平面式气体火花开关的设计和制作

基于表面微加工技术,设计并制作了一种微型平面式气体火花开关,其尺寸仅为1.5 cm0.5 cm,对制作的微型火花开关进行电路测试,得到其输出电流峰值约为3 450 A,上升时间164 ns。结合实验结果,对开关器件进行电路系统仿真并提取参数,得到系统电感为26.5 nH,电阻为0.066 ,与传统机械结构的立体式火花开关相比,器件参数得到显著优化。     

Factors affecting and methods of improving the pulse repetitionfrequency of pulse-charged and DC-charged high-pressure gasswitches

The results of this paper describe some of the factors which affect the repetitive operation of high-pressure gas switches (spark gaps) for both pulse-charged and DC-charged operation. Also discussed are methods which may be employed to improve the pulse repetition frequency (PRF) of spark gaps operating under such conditions. Under pulse-charged conditions, the voltage recovery process of the spark gap has been shown to be restricted following partial density recovery by the residual ion population. This restriction may be minimized by applying a suitable bias voltage across the gap to remove the ion influence. It is also possible to manipulate the voltage-pressure (V-p) breakdown characteristic of a spark gap in order to improve the rate of rise of recovery voltage by reducing the recovery voltage dependence upon gas pressure. The combination of these effects has been shown to reduce the voltage recovery time of pulse-charged spark gaps from several hundred milliseconds to several milliseconds. Under DC-charged conditions, where no “dead time” is available for voltage recovery, it is possible to employ corona discharge effects, which occur in highly nonuniform fields, to stabilize and control the breakdown process. The use of corona stabilization has enabled the operation of a self-closing spark gap at a PRF of more than 5 kHz, without employing gas flow techniques. A triggered version of a corona-stabilized spark gap has also been developed which has demonstrated single run capabilities of 10⁷ (4 h continuous operation at 700 pps) and a lifetime of ~10 shots (maintenance free, sealed switch). The triggered corona switch has also demonstrated controlled switching up to a PRF of 1.2 kHz     

Modeling of pulsed spark discharge in water and its application to well cleaning

This paper presents a simulation model for the generation of strong pressure wave by means of pulsed spark discharge in water and its application to well cleaning. In the simulation model, one-dimensional time-dependent magnetohydrodynamic equations are coupled to a capacitive discharge circuit equation. A cylindrical conducting spark channel formed by electrical breakdown of water gap between a pair of electrodes is treated as a load of which resistance and inductance are allowed to change with time. For describing the spark channel properties accurately, precise calculations on thermodynamic properties and electrical conductivity are included in the simulation model. The simulation results show an excellent agreement with the experimentally measured shock pressure as well as the current and voltage waveforms. The simulation reveals that Joule heating of the spark channel during the very early phase of electrical discharge plays a key role in the formation of shock wave in water. The voltage on a capacitor at breakdown, the circuit inductance, and the resistance of the spark channel are found to be the most important parameters for the shock wave formation. With this technique, a pilot test for the cleaning of a clogged well has been performed in a water well which was constructed as a test-bed for riverbank filtration near the Anseong-cheon (river) in Korea. Well treatments have been carried out with an electrical energy of 510 J stored on a pulsed power system, at which the maximum shock pressure is measured to be around 7 MPa at the position of the well screen, i.e. 0.1 m away from the spark gap. A slug test shows 2.9 times improvement in the hydraulic conductivity of the well, which, combined with a visual inspection inside the well using an underwater camera, clearly demonstrates that the strong pressure wave generated by underwater spark discharge can effectively remove almost all incrustations formed in the well screen and thus improve well performance. Operating parameters for controlling the strength of shock pressure are discussed using the simulation model for extensive applications of the present technique to various types of water wells.     

Compact pulsed power generator using an inductive energy storagesystem with two-staged opening switches

The pulsed power generator, named ASO-I, is extremely compact and light in comparison with a conventional pulsed power generator, which consists of a Marx bank and a water pulse forming line. The ASO-I has a two-staged opening switch, consisting of fuses in water and a plasma erosion opening switch, and can be operated hundreds of times a day at an output power of 230 kV and 35 kA. The parallel fuses are effective for power multiplication, and small differences in length of the parallel fuses do not influence the output power. The risetime of current through the short-circuit load decreases with the increase of the gap length of the spark gap, which is placed between the fuses and the load. The plasma erosion opening switch can be operated as a second opening switch, and the risetime of the current through the short-circuit load decreases from 250 to 10 ns. The maximum resistance of the plasma erosion opening switch is 3.5 Ω with an open-circuit load     

Wide-aperture electric-discharge XeCl lasers

Experimental investigations have been performed for aXeCl laser with the active region aperture equal to 6.5×7 and 15×15 cm. To pump the laser, two types of generator were used: a generator connected in a double-loop circuit with a peaking capacitor and a multichannel spark gap switch and a magnetic thyratron generator. The working mixtureNe−Xe−HCl was preionized with soft x rays and a low-current electron beam, providing an initial electron density ranging from 10⁶ to 5·10¹³ cm⁻³. Conditions in which a homogeneous space discharge is initiated have been studied. It has been investigated how the degree of ionization of the gas and the aperture of the active region affect the discharge and lasing characteristics of the laser. The laser efficiency reaches 4% with an energy of ≈ 6 J extracted from one liter of the active region. Institute of High-Current Electronics, Siberian Division of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 54–59, April, 2000.     

大电流两电极气体开关研究

 由于引燃管难以满足现在能源系统对放电开关承受大电流的要求，因此研制了大电荷转移量两电极气体开关。这种新型气体开关电极间距可调，无触发极，采用同轴结构，并将主电极置于金属腔体内，减少了放电对绝缘支撑的污染。主电极为铜钨合金材料，设计为平顶圆柱状，以提高烧蚀均匀度和热传导效率，减少电极材料喷溅，延长其寿命。绝缘支撑采用碗状结构，提高了机械强度，增加了沿面击穿距离。该开关工作电压达25 kV，放电电流超过100 kA（脉冲宽度600 μs），单次脉冲电荷转移量达50 C。实验结果显示该气体开关触发性能稳定，电极表面烧蚀均匀，多次大电流实验后电极表面保持完好，可应用于强激光能源系统。     

吹气对氮气火花隙开关重复频率运行性能的影响

 基于紧凑重复频率Tesla变压器实验平台,运用设计加工的紧凑型内部气流循环式火花隙开关,对吹气提高火花隙开关重复频率运行性能进行系统的实验研究,结果表明：重复频率小于50 Hz时,火花隙开关击穿电压不稳定度(RMS)小于5%,不需要吹气;在给定吹气速度下,火花隙开关重复频率运行存在临界重复频率;火花隙开关重复频率运行存在最佳吹气速度,且最佳吹气速度与重复频率之间满足线性关系,并可由实验确定;在优化吹气速度条件下,当气压处于0.7~1.5 MPa范围时,该火花隙开关击穿电压不稳定度(RMS)小于3%;在2.0 MPa的压强范围内,该吹气式火花隙开关可稳定工作至重复频率300 Hz,击穿电压400 kV。     

开关火花电阻对脉冲前沿的影响

 分析气体火花开关的电阻特性是研究开关能量损耗、电弧通道的热等离子过程、开关间隙绝缘恢复及输出脉冲特性的重要基础。基于气体开关的导通机理,建立了开关导通工作的电路模型,给出了与形成线、传输线联通的开关等效电路和开关电流表达式,分析了开关电感、电阻对电流增长（脉冲前沿）的影响。研究结果表明：对于大间距、高电压气体开关,火花电阻是影响开关输出脉冲前沿的主要因素。     

石墨型高能两电极气体开关

 为大型激光装置能源模块研制了一种采用石墨电极的两电极气体开关,阐述了石墨应用于高能两电极气体开关的技术关键,对气体开关中气体间隙的最优结构进行了电场强度分析。参考美国国家点火装置(NIF)能源模块中ST-300气体开关的已知参数,对研制成功的石墨型两电极开关进行了电气特性试验,证明了石墨型气体开关能够实现峰值电流达300 kA以上,单次转移电荷量100 C以上,寿命超过1 000次,满足1.2 MJ大型激光装置能源模块的工程技术要求。     

High-power nanosecond bipolar voltage pulses

This paper presents the design and testing results for a generator of bipolar voltage pulses of amplitude ±200 kV, duration ∼3.5 ns, and repetition rate up to 100 Hz across a 12.5-Ω matched load. The mode of multichannel switching of spark gaps with subnanosecond time delays between the operation of the channels has been realized. A numerical simulation of the generator operation has been performed with its design represented by homogeneous lines and with the parameters of spark gaps described in terms of the Felsenthal-Praud criterion for the breakdown delay and by the Rompe-Weitzel spark model. It has been demonstrated that mixtures of ordinary and inert gases as well as hydrogen show promise as fill gases for spark gaps to reduce losses. The generator is intended to excite wideband transmitting antennas. Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 41–46, December, 1999.     

Uncontrollable multichannel commutator in the output cascade of the SNOP-3 generator

A multichannel uncontrollable submersible commutator is described. The commutator is tested in the output cascade of the SNOP-3 generator in the discharge of a signal-forming line with a wave resistance of 0.65 Ω to a transmission line with the same wave resistance and an inductive load of 30 nH. The inductance and ohmic resistance of the commutator are determined (15–20 nH and 0.2 Ω, respectively). With the inductive load of 30 nH, a rate of current increase of 3·10¹³ A/sec is obtained. A special commutator design with a screened grounded plane is tested; this design permits reduction in the prepulse voltage at the load to 0.25% of the voltage at the signal-forming line. Institute of High-Power Electronics, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 67–72, December, 1995.     

High Current Operation of a Semi-insulating Gallium Arsenide Photoconductive Semiconductor Switch Triggering a Spark Gap

A transient peak current as high as 5.6 kA is obtained by a GaAs photoconductive semiconductor switch （PCSS） in series with a spark gap. Based on the characteristics of the GaAs PCSS, mechanisms of discharge between the PCSS and the spark gap are discussed. It is implied that a hybrid operation mode of photo-activated charge domain occurs due to the superposition of the bias voltage and the instantaneous radio frequency voltage.     

Continuing Studies of Plasma Erosion Switches for Power Conditioning on Multiterawatt Pulsed Power Accelerators

Recent PITHON experiments with plasma erosion switches (PES) have extended the range of operation of the switches by about 50 percent, in terms of closed time and charge passing through the switch. The quantity of charge passed through the switch has been increased to as much as 35 mC. Currents as large as 1 MA and voltages as great as 1.8 MV have been switched off to be diverted to a downstream load. The impedance of the erosion switch can be described as having three stages: 1) essentially zero impedance, 2) a transitional opening phase, and 3) an impedance which is very large (greater than 5 ?) in comparson with the subohm downstream load. Current diagnostics, consisting of Rogowski coils and segmented shunts, have been successfully developed to monitor the current which propagates to the load region. These monitors have measured rise times as short as 38 ns and slew rates as great as 1014 A/s at the load. With wire array loads, the pulse conditioning of the switch has been observed to reduce the magnitude of the current losses in the feed which are present when no switch is used. Correlations have been made between the switch closed time, voltage, current, and power with the feed inductance and the generator power injected into the magnetic insulated transmission line (MITL).     

小型场畸变气体开关的击穿抖动特性

基于高功率重复频率脉冲功率源的应用需求,研制了一种三电极场畸变结构气体火花间隙开关,并开展了重复频率条件下的触发特性研究。实验研究了场畸变火花间隙开关的触发特性随重复频率、气体成分、工作压强和工作系数的变化关系,计算了气体开关的触发击穿时延和抖动参数,分析了影响开关触发特性的主要因素。实验结果表明:气体开关触发击穿的抖动随着重复频率增加而增大;填充气体中SF₆和N₂体积比1∶1时,混合气体的综合性能较好;工作系数主要影响开关第二放电火花间隙(间隙2)的击穿抖动。