Progress in Switching Technology for Mets Systems

Three distinct sets of switching requirements have emerged from design optimization studies of large superconducting magnetic energy storage systems, such as the METS system to power the adiabatic plasma compression field in the proposed ?-pinch SFTR. Extremely low joule loss cryogenic disconnects are required between storage coils in the liquid helium environment to allow charging the coils in series over a prolonged time, then to isolate the coils for parallel fast discharging into the load. Another switch must break the current in the series charging loop and absorb the energy from the stray inductance. This action will allow the subsequent opening of the cryogenic disconnects under near zero current condition. The current now has been transferred to the many paralled circuits, each containing a high current, high voltage interrupter. The opening and arc commutation of the interrupter starts the energy transfer into the load. The primary activities associated with the cryogenic disconnect have been testing and development of contact materials, configurations, and closing forces for carrying 26 kA with a resistance less than 40 n?, and development of an actuating system that is both reliable and fast acting in a liquid helium environment. The charging loop switch will include a continuous duty switch and a vacuum interrupter. The continuous duty switch resistance can be an order of magnitude larger than that of the cryogenic disconnect because it does not present a refrigeration load.     

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     

The Jon Beam Opening Switch

Plasma opening switches (POS's) have shown excellent characteristics in pulsed power applications. Proposed POS scaling predicts that the fastest opening time for a given conducted current should occur using a high-velocity low-density plasma as the switch medium. The ion beam opening switch (IBOS) uses a charge-neutral ion beam of 100-300 kV, ? 120 A/cm2 as the switch "plasma." Its velocity of up to 600 cm/?s and density of ~1012/cm3 make this a very fast low-density plasma compared with typical 10 cm/?s and 1013/cm3 POS plasmas. The IBOS has conducted ? 70 kA flowing in a parallel-plate transmission line driven by a 4-? pulser. IBOS opening time is load dependent, being ? 4 ns into a 15-nH load and about twice as long into a 4-? electron diode load. However, switch impedance is not zero during the entire conduction time, rising to ? 3 ? by the time of peak current. Peak current conducted before opening does not vary linearly with either injected ion current or switch axial length. Instead, the conduction current scales with plasma density in the switch, and is nearly independent of switch area until the area is restricted to a narrow (~1 cm) strip.     

Plasma Erosion Opening Switch in the Double-Pulse Operation Mode of a High-Current Electron Accelerator

This paper reports the results of investigations of the operation of a fast current opening switch, with a 1013-1016 plasma density produced either by dielectric surface flashover or by explosive emission of graphite. A series of two pulses was applied to two diodes in parallel. The first pulse produced plasma in the first diode which closed that diode gap by the arrival time of the second pulse. The first, shorted, diode then acted as an erosion switch for the second pulse. A factor of 2.5-3 power multiplication was obtained under optimum conditions. The opening-switch resistance during the magnetic insulation phase, neglecting the electron losses between the switch and the generating diode, exceeded 100 ?. The duration of the rapid opening phase was less than 5 ns under optimum conditions. This method of plasma production does not require external plasma sources, and permits a wide variation of plasma density, which in turn allows high inductor currents and stored energies.     

Plasma erosion opening switch using laser-produced plasma

In order to construct a practical inductive energy storage pulsed power generator, an opening switch which can repeatedly conduct a large current and then rapidly interrupt this current is necessary. Though the plasma erosion opening switch (PEOS) can interrupt a large current rapidly, the effective number of switch operations is limited because of the decrease of the carbon sprayed on the insulator with each shot. A PEOS using a laser-produced plasma, which can possibly be operated for hundreds of thousands of shots without maintenance, is proposed, and its operation as an opening switch is confirmed experimentally     

High-voltage microwave-triggered switches

The operation of three types of experimental high voltage microwave-triggered switches developed by the University of St. Andrews and DRA Malvern is described. The POLOTRON and the microwave-triggered three-gap-switch (MTGS) are closing switches and the microwave-triggered tacitron, (MITTON) is a closing and opening switch. The switches are robust hydrogen thyratron type devices, with an annular geometry, where closure is achieved using microwave fields to ionize the low pressure gas within the switch. In the case of the MITTON, the switch is opened by the application of a negative bias voltage to a large area metal grid. The POLOTRON is designed for fast switching applications. Its annular geometry results in an inherent low inductance and anode fall-times of less than 3 ns have been measured for a cold-cathode POLOTRON at charging voltages up to 30 kV. The MTGS, also a cold cathode switch, was developed for use in the DUOTRON transient generator (a voltage doubler). Output voltages of up to 16 kV have been measured at repetition rates of 90 Hz. The MITTON has closing characteristics similar to the POLOTRON and anode voltage fall-times of less than 10 ns have been measured at voltages up to 16 kV. Opening times of 0.5 μs have been achieved with an anode voltage of 10 kV and current of 10 A     

Closing/opening switch for inductive energy storage applications

A magnetically delayed vacuum switch operating sequentially in a closing mode and then in an opening mode enables the design of a compact electron-beam generator based on an inductive energy store and having only a single switch. Furthermore, the system can be entirely vacuum insulated, with no power feedthrough requiring low inductance or operating at high-impulse voltage levels. Feasibility of the unique power-switching configuration has been explored theoretically, experimentally, and computationally. In a proof-of-principle experiment, a voltage impulse twice the magnitude of the DC charge voltage was observed at a power level of 20 MW. A computational model of the experiment produced results consistent with the experiment, and furthermore, predicted the possibility of achieving much higher power levels in an optimally configured system     

650kV/2ns高压脉冲发生器研制

研制了一套峰值650kV、脉宽2ns的窄脉冲发生器,具有结构紧凑、体积小巧、便于移动和产生优质的纳秒高压脉冲等优点。该发生器基于三谐振脉冲变压器原理和脉冲形成压缩实现窄脉冲输出,采用紧凑双锥形绕组铁芯变压器、LC调谐回路和27pF,30Ω脉冲形成线组成三谐振回路,油介质自击穿开关导通后在负载上获得高压脉冲。实验结果表明,该窄脉冲发生器可在80Ω电阻负载上输出脉冲峰值约650kV,脉宽约2ns,与理论分析的结果相吻合。     

600 A重复频率脉冲恒流源研制北大核心CSCD

针对国内脉冲恒流源幅值较小、重复频率较低等问题,设计了基于电流闭环反馈控制的恒流电路,建立了相应的数学模型,并采用Pspice仿真验证了电路的功能,最终研制了1台600 A重复频率工作的脉冲恒流电源。电源采取储能放电配合高速开关的工作模式,使用功率场效应三极管作为线性调整开关,可大范围自动恒流,适用于激光二极管负载。输出的脉冲电流幅值最高600 A,上升时间小于40μs,电压幅值最高320 V,脉宽100~600μs可调,工作重复频率最高200 Hz。电源体积较小,结构紧凑,效率可达90%以上。     

Design and testing of a 5 MW battery-based inductive power supply

A 5 MW battery-based inductive power supply (IFS) was designed and tested. The battery consisted of 636 low-resistance, sealed, lead-acid batteries organized in strings that are connected to busbars via small-size contactors. A vacuum breaker serves as a closing switch, while an explosively driven opening switch interrupts the circuit, transferring the coil current to the load. In case of load malfunction, the energy stored in the coil is dumped into a dissipative load. The systems for control and measurement are decoupled from the high-current carrying conductors. In this paper, optimization of the battery-coil matching is discussed. The current sharing between the strings is analyzed. IFS parasitic inductance for different arrangements was calculated and reduced by careful design to 4 μH. PSpice simulations of the IFS accounting for nonlinearity in the components are presented. Main components, such as batteries, contactors, and protective equipment were tested under high current conditions. The IFS was evaluated both with a resistive and an electro-thermal load with stored energy up to 0.5 MJ. Power amplification of 100 was obtained. It was found that the experimental results agree closely with calculations, and the IFS performs according to the design specifications. Methods of developing a more compact IFS using advanced battery technology are analyzed     

陶瓷储能平行平板层叠Blumlein线

采用一种具有高储能密度的玻璃陶瓷板介质作为平行平板层叠Blumlein线(SBL)的储能介质,设计了一种平行平板SBL。针对该SBL的特点,设计了一种层叠轨道间隙触发开关。在实现多通道时,模拟与实验研究结果均表明该开关的上升时间小于10 ns。为验证这种设计理念,制造了一台2级平行平板SBL样机,实验结果表明,该结构适合于实现脉冲功率系统的模块化设计。     

The Atlas project-a new pulsed power facility for high energydensity physics experiments

Atlas is a facility being designed at Los Alamos National Laboratory (LANL) to perform high-energy-density experiments in support of weapon physics and basic research programs. It is designed to be an international user facility, providing experimental opportunities to researchers from national laboratories and academic institutions. For hydrodynamic experiments, it will be capable of achieving a pressure exceeding 30 Mbar in a several cubic centimeter volume. With the development of a suitable opening switch, it will be capable of producing more than 3 MJ of soft X-rays. The capacitor bank design consists of a 36 MJ array of 240 kV Marx modules. The system is designed to deliver a peak current of 45-50 MA with a 4-5-μs rise time. The Marx modules are designed to be reconfigured to a 480-kV configuration for opening switch development. The capacitor bank is resistively damped to limit fault currents and capacitor voltage reversal. An experimental program for testing and certifying prototype components is currently under way. The capacitor bank design contains 300 closing switches. These switches are a modified version of a railgap switch originally designed for the DNA-ACE machines. Because of the large number of switches in the system, individual switch prefire rates must be less than 10^-4 to protect the expensive target assemblies. Experiments are under way to determine if the switch-prefire probability can be reduced with rapid capacitor charging     

集成模块化Cantor网络的控制和光学实现

提出光学集成模块化Ｃａｎｔｏｒ网络，并建立了Ｃａｎｔｏｒ网络的快速控制体系，该网络是基于极化多通道技术，利用晶体的双折射效应和电光特性实现网络的互连变换，该网络易安装，抗干扰。     

快脉冲高电压大电流测量探头标定方法

基于脉冲形成原理提出了一种快脉冲高电压大电流测量探头的在线标定方法。利用闪光二号加速器输出线和二极管作为脉冲形成线,结合研制的低电感开关和负载,产生一个前沿小于3 ns、脉宽20 ns的准方波,对二极管电压测量探头微分型电容分压器和电流测量探头微分环进行了在线标定,得到测量探头在实际使用环境中的时间响应小于4 ns。该方法消除了非在线标定环境和实际环境无法统一对标定结果的影响,可推广应用于传输线型脉冲功率装置的探头标定。     

“强光一号”等离子体开关及负载稳定性分析

"强光一号"等离子体断路开关(POS)及负载二极管系统工作性能不够稳定,通过分析数据指出POS等离子体源参数差异性是导致系统不稳定的主要原因。POS等离子体源参数重复性测量结果表明,在开关断路时刻等离子体源瞬时发射等离子体密度重复性极差在10%左右,而开关区间累积等离子体密度极差超过100%。开关区间累积等离子体密度和阴极重粒子发射会对POS断路性能产生显著影响。计算表明开关区间累积等离子体密度差异对POS断路电流阈值影响达到200kA,与运行数据统计结果一致;在断路电流阈值相同的条件下,阴极物质逸出对二极管电压影响显著,MCNP程序计算结果表明,产生辐射剂量差别可以达到80%,与统计数据相当。     

Feasibility studies on performance enhancement in electrically exploding foil accelerators

Electrically exploding foil (EEF) technique offers a unique small-scale device to accelerate thin plastic foils (liner) to high (>10 km) velocities. Besides direct application as a macroparticle accelerator for various applications, such systems can also serve as plasma injectors or pre-accelerators to electromagnetic launchers. Though empirical models for scaling of liner velocity in such devices suggest the important role of burst current density in exploding foil, but behavior of slow and fast (dI/dt/spl ges/10/sup 12/ A/s) systems appear to differ significantly. In this paper, based on some established models and realistic current profiles, it is inferred that higher energy of a capacitor bank may not translate to higher velocity in "optimized" EEF systems, if its rise time is poor. A possible way to overcome this problem could be to use an additional stage of metallic foil as an opening switch. The consequent fast rising current may be expected to enhance the liner velocity by a factor of 2-5 in typical capacitor banks. Analysis and relevant experiments are described to investigate the issues.     

150 kV全固态高压脉冲发生器设计

设计了一种基于全固态MOSFET半导体开关器件的Marx脉冲发生器。充电回路用快恢复二极管代替充电电阻,减小了充电部分功率损耗;将主电路和驱动电路集成在一起,采用自取电模式给驱动电路供电;由光纤传输驱动信号,抑制了放电回路对触发信号的干扰;采用顺/逆时针方向环形分布的紧凑型拓扑结构,不仅减小了回路电感,而且实现了脉冲发生器的小型化与模块化。所设计的Marx发生器充电部分仅需提供900 V低压,用180级单元串联,获得最高幅值为150 kV、脉宽1~5 s可调的高压快脉冲,前沿控制在500 ns以内。利用该脉冲发生器在50 k电阻和5 pF电容并联的等效负载上进行了一系列实验;比较分析了脉冲发生器工作过程中影响脉冲上升沿的几个主要因素,包括回路电感、MOSFET驱动电压及主回路分布电容等,并讨论了提升脉冲前沿的技术措施。     

一种智能光网络中的亚毫秒光开关阵列

设计研制了一种亚毫秒级微机械光开关阵列.该阵列驱动电压为5V,开关时间小于750μs, 插入损耗在0.6 dB～0.8 dB之间,串扰<－70 dB.具有结构简单、成本低廉、可大规模集成的优点,能很好地解决智能光网络节点连接设备OADM快速信号转换和串扰问题.详细介绍了该光开关阵列实现原理,报告了器件性能测试,并应用FEA软件分析了开关单元中磁场和开关驱动过程.     

基于反向开关晶体管的重复频率脉冲电流源

 介绍一种基于新型大功率半导体反向导通型双晶复合晶体管(RSD)开关的重复频率脉冲电流源。重复频率脉冲源主要包括半导体RSD开关、快速可控硅和磁开关等元件。初步实验产生的脉冲峰值电流约6.2 kA，脉冲宽度约10 μs，电流上升率可达18 kA/μs，工作电压约1 kV，可工作于单次和重复频率1，10和100 Hz等状态。     

4×4自由空间光开关结构及其矩阵分析

光开关是全光通信网络中的一种重要的光无源器件。提出了一种4×4自由空间光开关的结构设计方法,并进行了矩阵理论分析。该4×4光开关具有新颖的光模块化结构,该光开关结构仅由偏振分束组合棱镜,λ／4波片,λ／2波片,直角棱镜,全反镜和偏振光调制器组成,对光开关的控制与输入光束的偏振态无关。所有的输出端口可以和输入端口无阻塞地互连交换。这种新型的光开关结构具有光学元件少,结构紧凑,模块化,与偏振无关的特点。基于4×4光开关的矩阵分析得到了路由控制表,为4×4光开关从任意输人端口到任意输出端口的路由控制状态提供了理论分析手段,从而可以方便地实现无阻塞地光交换开关矩阵的路由控制功能。