CO2 laser pulse shortening by laser ablation of a metal target

A repeatable and flexible technique for pulse shortening of laser pulses has been applied to transversely excited atmospheric (TEA) CO(2) laser pulses. The technique involves focusing the laser output onto a highly reflective metal target so that plasma is formed, which then operates as a shutter due to strong laser absorption and scattering. Precise control of the focused laser intensity allows for timing of the shutter so that different temporal portions of the pulse can be reflected from the target surface before plasma formation occurs. This type of shutter enables one to reduce the pulse duration down to ~2 ns and to remove the low power, long duration tails that are present in TEA CO(2) pulses. The transmitted energy is reduced as the pulse duration is decreased but the reflected power is ~10 MW for all pulse durations. A simple laser heating model verifies that the pulse shortening depends directly on the plasma formation time, which in turn is dependent on the applied laser intensity. It is envisaged that this plasma shutter will be used as a tool for pulse shaping in the search for laser pulse conditions to optimize conversion efficiency from laser energy to useable extreme ultraviolet (EUV) radiation for EUV source development.     

Time-of-flight electron velocity spectrometer using transverse electric field deflectors

A time-of-flight electron velocity spectrometer using two transverse electric field deflectors as fast electronic shutters has been constructed. Square-wave voltage pulses applied to the two shutters limit the transmitted current to electrons in selected narrow velocity ranges. Analysis of the magnitude of this transmitted electron current as a function of the time delay between the two shutter openings leads to the electron velocity or energy spectrum in the incident charged particle beam. Time resolutions of 5 ns (FWHM) can be obtained with the present apparatus for electrons in the 5-100 eV range.     

Studying dynistor switches with nanosecond switching times

The results of studying the process of switching deep-level dynistors (DLDs) with 16- and 24-mm-diameter structures in the modes of switching micro- and nanosecond pulses with amplitudes of several kiloamperes are presented. It is shown that the dynistor switching process is highly uniform. The results of DLD tests at a high repetition rate of switched current pulses are presented. The principle of constructing high-power DLD switches with independent triggering of dynistors, which is based on the use of a single-turn saturable-core choke in the power circuit and a saturable-core isolating transformer in the DLD triggering circuits, is described. A DLD switch with an operating voltage of 8 kV is considered, which can switch current pulses at a frequency of 2 kHz with an amplitude of 1.5 kA and a duration of 200 ns.     

Design and experimental study of a power supply for micro-wire EDM

This paper presents the development and application of a new power supply in micro-wire EDM. A transistor-controlled power supply composed of a low-energy discharge circuit and an iso-frequency pulse control circuit was designed to provide the functions of high frequency and lower energy pulse control. Pulse states are classified as open circuit, normal spark, arc discharge and short circuit by means of the level of gap voltage and associated discharge current. A power supply test revealed that a high current-limiting resistance results in a decrease of discharge current. Peak current decreases with an increase of pulse-control frequency. Experimental results not only demonstrate that the iso-frequency pulse generator can provide low-energy pulses with a frequency of 185 kHz and a discharge current of 0.7 A, they also verify the applicability of the developed power supply in micro-wire EDM.     

A Small Dynistor Generator of High-Power Nanosecond Pulses

A generator of high-power nanosecond current pulses on the basis of a dynistor, which is switched on within 1 ns, is described. Its dimensions are 70 × 80 × 25 mm; at a power voltage of 2.2 kV, the generator switches weakly damped alternating bell-shaped current pulses with an amplitude of 5 kA and a duration of 400 ns.     

A high-frequency semiconductor generator of high-voltage nanosecond pulses

A generator of high-voltage rectangular nanosecond pulses equipped with switches in the form of assemblies of deep-level dynistors connected in series is described. A control circuit for dynistors based on an assembly of inversely switched-off diodes connected in series is considered. The generator can operate at a frequency of 10 Hz and form (at a 20-pF load) rectangular voltage pulses with short (4 ns) leading and trailing edges and a short (25 ns) delay relative to an external control signal. The amplitude and duration of output pulses are controlled smoothly in the ranges 7–9 kV and 100–600 ns, respectively. The spread of moments of operation is within 0.5 ns.     

Optimization of high-voltage devices for energy compression of nanosecond pulses

Designs of compact converters intended for compression of high-voltage pulses with durations of a few nanoseconds and operating in a traveling wave mode were examined. The energy compression unit contained two lines-high-impedance and forming-with a high -pressure gas spark discharger used as a switch. A traditional serial connection of lines was replaced by a parallel connection to increase the energy compression efficiency. The power of the initial pulse (amplitude, 145 kV; half-height duration, 4 ns; and rise time, 1.5 ns) at a load of 45 Ω was increased by a factor of 1.8, while the calculated value was 2.5. The amplitude was as great as -195 kV, and the power was 17% higher relative to the circuit with a serial connection of lines. When shaped, the pulse was compressed in time to 0.8 ns. Two modifications of devices converting the initial pulse with an amplitude of -160 kV and a rise time of 0.3 ns into pulses with amplitudes of -210 and -250 kV and durations of 0.80 and 0.45 ns, respectively, were tested. Waveguide components of the converters were developed, with which it was possible to minimize the dimensions of the device in order to avoid excitation of higher harmonics while maintaining the electric strength.     

谈中频电源中晶闸管的损坏与保护

阐述了中频电源中晶闸管的损坏原因及其保护措施,确保电源运行的安全条件,这不仅有利于对中频电源的使用与维护,减少晶闸管的损坏;也有利于对电源控制线路的改进。     

Nanosecond Ozonators

The main advantage of nanosecond ozonators is that they can operate at high atmospheric humidity without compressors, air preparation systems, and expensive electrode chambers. The energy cost per unit for ozone production is the same as in the case of ordinary ozonators. The electrode system of nanosecond ozonators can be placed directly in an air-and-water mixture. At a short (250 ns) duration of pulses, ozone can be synthesized in the barrier-free electric discharge. Most promising for practical applications are nanosecond ozonators with barrier electric discharge. The electrical circuit for the power supply of a nanosecond ozonator is given.     

啮合式电动机调速系统设计

针对新型啮合式电动机的特点,以TMS320F2407为控制器设计了一种高效可靠的调速系统。文章介绍了系统的整体结构和工作方式,该系统主要由DSP控制器及外围电路、功率变换电路、电流电压检测电路、过压过流保护电路及位置速度检测电路等模块组成。     

An experimental stand for investigating protective devices for high-voltage overhead lines

An experimental stand for investigating and testing lightning protection devices for aerial power lines is described. The stand is composed of an oscillation circuit modeling a power line with an industrial frequency of 50 Hz, a voltage of up to 10 kV, and a current amplitude in the circuit as high as 10 kA; a generator of short single current pulses with a voltage of up to 25 kV and a current amplitude of up to 30 kA, modeling a lightning discharge; and commutation, control, and diagnostic systems. The stand is used to investigate elements of multi-chamber arrester systems for protecting high-voltage overhead lines.     

A power supply for simulating lightning-current pulses

The circuit diagram of a power-supply unit for simulating a positive lightning on a system of grounding current pulses is presented. The main criteria that governed the development of this facility are expounded. The design and order of operation of an experimental specimen of a power supply developed at the VNIIEF on the basis of a BMΓ-320 cascade magnetic-cumulation generator are considered. A calculation technique is described with which a device for the formation of current pulses of up to 90 kA in a standard grounding system has been developed.     

A compact, low jitter, nanosecond rise time, high voltage pulse generator with variable amplitude

In this paper, a compact, low jitter, nanosecond rise time, command triggered, high peak power, gas-switch pulse generator system is developed for high energy physics experiment. The main components of the system are a high voltage capacitor, the spark gap switch and R = 50 Ω load resistance built into a structure to obtain a fast high power pulse. The pulse drive unit, comprised of a vacuum planar triode and a stack of avalanche transistors, is command triggered by a single or multiple TTL (transistor-transistor logic) level pulses generated by a trigger pulse control unit implemented using the 555 timer circuit. The control unit also accepts user input TTL trigger signal. The vacuum planar triode in the pulse driving unit that close the first stage switches is applied to drive the spark gap reducing jitter. By adjusting the charge voltage of a high voltage capacitor charging power supply, the pulse amplitude varies from 5 kV to 10 kV, with a rise time of <3 ns and the maximum peak current up to 200 A (into 50 Ω). The jitter of the pulse generator system is less than 1 ns. The maximum pulse repetition rate is set at 10 Hz that limited only by the gas-switch and available capacitor recovery time.     

以c8051F020为核心的CCD驱动与采集系统的设计

介绍了以单片机为核心设计CCD驱动系统的新方法.该方法采用新型高集成度(集成AD及RAM)、超高速(单周期指令50 ns)单片机c8051F020为微处理器,在根本上克服了传统单片机CCD驱动系统中驱动频率慢的弱点;驱动脉冲由单片机的通用输入输出口产生,各路驱动脉冲间的时序关系由软件控制,免除外围电路中使用单稳态触发器;采用该方法的驱动电路只需使用2颗芯片(单片机与CCD),电路连接简单且板面积大为减小.该驱动系统在采用单片机片内集成的500 kHz模数转换器时工作频率接近500 kHz,积分时间由单片机内部的定时器作为标准时钟源确定,精度可以达到50 ns.     

A nanosecond SOS generator with a peak power of 4 GW

A high-current nanosecond generator with a peak power of up to 4 GW, an output voltage of 0.4–1 MV, a pulse duration of 8–10 ns, and pulse repetition rates of 300 Hz in a continuous mode and up to 1 kHz in the burst mode is described. The average output power at a pulse repetition rate of 1 kHz reaches 30 kW. The generator has an all-solid-state energy-switching system. A semiconductor opening switch on SOS diodes forms output pulses. The electric circuit and design of the generator are described, and the experimental results are presented. A device for eliminating prepulses across the load is proposed. The results of its testing and numerical simulation are presented.     

An accurate and economical approach for induction motor field efficiency estimation using bacterial foraging algorithm

As the demand of electrical energy increases, it is vital to replace inefficient motors with new energy efficient ones. The first step towards achieving this goal is to estimate the existing motors efficiencies accurately to determine how much energy saving will be achieved by using energy efficient motors. This paper proposes an economical and accurate approach for motor field efficiency estimation using bacterial foraging algorithm. The approach relies on the measurement of the stator current, stator voltage, input power, stator resistance and rotor speed of the motor without conducting no-load and locked-rotor tests. The BF algorithm is used to determine the equivalent circuit parameters of the motor. The efficiency is then estimated using these parameters. The advantages of the proposed method over the existing methods are simple procedure, efficiency can be estimated accurately without conducting any invasive tests and inexpensive. The approach has been tested on a 5 HP motor and the results are compared with particle swarm optimization method, immune algorithm method, torque gauge method, equivalent circuit method, slip method, current method and segregated loss method. The results demonstrate that the proposed approach can accurately estimate the field efficiency of motor. Accordingly, it is suitable for conducting energy audits and management of the motor.     

A generator of high-power nanosecond pulses based on a modular two-level summator

A modular approach to designing generators of high-power high-voltage nanosecond pulses on the basis of a two-level wave summator and transistor formers of partial pulses is considered. The design and parameters of the modules that are oriented at the development of generators of voltage pulses of up to 300 kV at a current of up to 4 kA are described. The capabilities of these modules are demonstrated based on the example of a pulse generator with a power of 10 MW, a varied pulse duration of 50–150 ns, and a pulse repetition rate of up to 2 kHz.     

A Device Generating Nonequilibrium Phonons of Terahertz Frequencies

A device generating nonequilibrium phonons with an equivalent temperature of up to 130 K in solids is described. The method of heat pulses is used. The heat pulses are initiated by current pulses with a width of 10–100 ns and a rise time of 2 ns.     

Semiconductor switches of laser pumping pulses of nanosecond duration

Switches of megawatt nanosecond pulses based on high-voltage (12 kV) assemblies of drift step-recovery diodes (DSRDs) and deep-level dynistors (DLDs) are described. Circuit diagrams allowing their use in laser technology are considered. Results of testing of the diode and dynistor switches in power supply circuits of nitrogen lasers at a frequency of 100 Hz are presented. Their high efficiency in shaping of pumping current pulses with a rise time of 10 ns and amplitudes of 500 A (a DSRD switch) and 900 A (a DLD switch) is shown.     

Magnetic torque maximization in a camera shutter module by the topology optimization

In recent years, there has been a stronger demand for the weight reduction of components of various portable electronic devices. This work is motivated by the need to reduce the weight of a camera shutter module without much decreasing the torque generated by its magnetic circuit. Because the camera shutter speed is most significantly affected by the torque, the magnitude of the generated torque should also be considered in the design for the weight reduction. Thus, we formulate the design problem as a torque maximization problem under various mass constraints. Specifically, we propose to formulate it as a topology optimization problem of magnetic circuits and find optimal shapes of yokes (and magnets) in the circuits. For the maximization formulation, the objective function is chosen as the average of clockwise and counterclockwise torques over a whole range of rotation angles of a magnet corresponding to the shutter opening angle. Limits on the mass of the yoke and magnet in a magnetic circuit are imposed as constraints. The torque generated by a magnetic circuit is calculated by the modified Maxwell stress tensor method. A series of mass constraint ratios is considered to investigate the effects of the mass usage on the magnitude of torque generated by optimized circuits. The region occupied by the yoke (and the magnet) is designated as a design domain, while coils are assumed to belong to a non-design domain. By demonstrating that the optimized magnetic circuits outperform a nominal circuit, the use of the average torque as an objective function including a corresponding treatment of a rotating magnet proposed in this work is shown to be effective for the topology optimization of magnetic circuits in a camera shutter module.