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.     

Design and performance of a pulse transformer based on Fe-based nanocrystalline core

A dry-type pulse transformer based on Fe-based nanocrystalline core with a load of 0.88 nF, output voltage of more than 65 kV, and winding ratio of 46 is designed and constructed. The dynamic characteristics of Fe-based nanocrystalline core under the impulse with the pulse width of several microseconds were studied. The pulse width and incremental flux density have an important effect on the pulse permeability, so the pulse permeability is measured under a certain pulse width and incremental flux density. The minimal volume of the toroidal pulse transformer core is determined by the coupling coefficient, the capacitors of the resonant charging circuit, incremental flux density, and pulse permeability. The factors of the charging time, ratio, and energy transmission efficiency in the resonant charging circuit based on magnetic core-type pulse transformer are analyzed. Experimental results of the pulse transformer are in good agreement with the theoretical calculation. When the primary capacitor is 3.17 μF and charge voltage is 1.8 kV, a voltage across the secondary capacitor of 0.88 nF with peak value of 68.5 kV, rise time (10%-90%) of 1.80 μs is obtained.     

750 kV电容式电压互感器现场检验系统的研究

针对目前750 kV电容式电压互感器(CVT)测试中传统比较测差法和"低校高"法存在的问题,研究并开发出750 kV CVT测试和检验系统。通过对750 kV CVT的工作原理、等效电路和误差组成的分析,提出了750 kV CVT空载误差、负荷误差的测试方法和测试线路,研制了30.6 kV带升压器标准电压互感器、变频电子电源和低频互感器检验仪,组成了一套完整的检验系统。通过现场试验,测试数据准确可靠,可以满足0.2级750 kV CVT量值溯源的要求,具有较高的实用和推广价值。     

Analysis of a modular generator for high-voltage, high-frequency pulsed applications, using low voltage semiconductors (< 1 kV) and series connected step-up (1:10) transformers

This article discusses the operation of a modular generator topology, which has been developed for high-frequency (kHz), high-voltage (kV) pulsed applications. The proposed generator uses individual modules, each one consisting of a pulse circuit based on a modified forward converter, which takes advantage of the required low duty cycle to operate with a low voltage clamp reset circuit for the step-up transformer. This reduces the maximum voltage on the semiconductor devices of both primary and secondary transformer sides. The secondary winding of each step-up transformer is series connected, delivering a fraction of the total voltage. Each individual pulsed module is supplied via an isolation transformer. The assembled modular laboratorial prototype, with three 5 kV modules, 800 V semiconductor switches, and 1:10 step-up transformers, has 80% efficiency, and is capable of delivering, into resistive loads, -15 kV1 A pulses with 5 micros width, 10 kHz repetition rate, with less than 1 micros pulse rise time. Experimental results for resistive loads are presented and discussed.     

Mega-ampere submicrosecond generator GIT-32

The GIT-32 current generator was developed for experiments with current carrying pulsed plasma. The main parts of the generator are capacitor bank, multichannel multigap spark switches, low inductive current driving lines, and central load part. The generator consists of four identical sections, connected in parallel to one load. The capacitor bank is assembled from 32 IEK-100-0.17 (0.17 microF, 40 nH, 100 kV) capacitors, connected in parallel. It stores approximately 18 kJ at 80 kV charging voltage. Each two capacitors are commuted to a load by a multigap spark switch with eight parallel channels. Switches operate in ambient air at atmospheric pressure. The GIT-32 generator was tested with 10, 15, and 20 nH inductive loads. At 10 nH load and 80 kV of charging voltage it provides 1 MA of current amplitude and 490 ns rise time with 0.8 Omega damping resistors in discharge circuit of each capacitor and 1.34 MA530 ns without resistors. The net generator inductance without a load was optimized to be as low as 12 nH, which results in extremely low self-impedance of the generator ( approximately 0.05 Omega). It ensures effective energy coupling with low impedance loads like Z pinch. The generator operates reliably without any adjustments in 40-80 kV range of charging voltage. Maximum jitter (relative to a triggering pulse) at 40 kV charging voltage is about 7 ns and lower at higher charging voltages. Operation and handling are very simple, because no oil and no purified gases are required for the generator. The GIT-32 generator has dimensions of 3200 x 3200 x 400 mm(3) and total weight of about 2500 kg, thus manifesting itself as a simple, robust, and cost effective apparatus.     

An accelerating voltage generator for compact pulsed neutron sources

A multistage generator of high-voltage pulses with a scroll geometry of spark switches, which is produced according to the Marx scheme, is presented. The device is designed for a small pulsed neutron source and makes it possible to obtain accelerating-voltage pulses with amplitudes of up to 450 kV at a stored energy of up to 50 J and a load current of up to 1.5 kA.     

A low-impedance high-voltage bipolar pulse former

The results on the formation of bipolar pulses with amplitudes of up to 100 kV, a duration of 2 ns, and a pulse repetition rate of 100 Hz across a 12.5-Ω load are presented. Lines with a characteristic impedance of 6.25 Ω were switched using multichannel ring switches with 70-mm-diameter electrodes in a nitrogen medium at a pressure of 40–60 atm. At a pressure of 40 atm, the rms deviation of the operation time of the sharpening switch reaches 40 ps at a voltage-pulse rise rate of 7 × 10¹³ V/s at the electrodes. As the pressure increases, the stability of the output bipolar pulses deteriorates; this is probably associated with a disturbance of the multichannel-switching mode in the sharpening switch. The performed simulation of the pulse-former operation showed that the energy loss in the switches reaches 40% of the stored energy in the output line of the Sinus-160 generator.     

Note: A portable pulsed neutron source based on the smallest sealed-type plasma focus device

Development and operation of a portable and compact pulsed neutron source based on sealed-type plasma focus (PF) device are reported. The unit is the smallest sealed-type neutron producing PF device. The effective volume of the PF unit is 33 cm(3) only. A compact size single capacitor (4 μF) is used as the energy driver. A battery based power supply unit is used for charging the capacitor and triggering the spark gap. The PF unit is operated at 10 kV (200 J) and at a deuterium gas filling pressure of 8 mb. The device is operated over a time span of 200 days and the neutron emissions have been observed for 200 shots without changing the gas in between the shots. The maximum yield of this device is 7.8 × 10(4) neutrons/pulse. Beyond 200 shots the yield is below the threshold (1050 neutrons/pulse) of our (3)He detector. The neutron energy is evaluated using time of flight technique and the value is (2.49 ± 0.27) MeV. The measured neutron pulse width is (24 ± 5) ns. Multishot and long duration operations envisage the potentiality of such portable device for repetitive mode of operation.     

Fusion neutron detector for time-of-flight measurements in z-pinch and plasma focus experiments

We have developed and tested sensitive neutron detectors for neutron time-of-flight measurements in z-pinch and plasma focus experiments with neutron emission times in tens of nanoseconds and with neutron yields between 10(6) and 10(12) per one shot. The neutron detectors are composed of a BC-408 fast plastic scintillator and Hamamatsu H1949-51 photomultiplier tube (PMT). During the calibration procedure, a PMT delay was determined for various operating voltages. The temporal resolution of the neutron detector was measured for the most commonly used PMT voltage of 1.4 kV. At the PF-1000 plasma focus, a novel method of the acquisition of a pulse height distribution has been used. This pulse height analysis enabled to determine the single neutron sensitivity for various neutron energies and to calibrate the neutron detector for absolute neutron yields at about 2.45 MeV.     

A SOS-Generator for technological applications

A solid-state nanosecond SOS-generator for electrophysical technology applications is described. In the input part of the generator, the energy arrives at the high-voltage magnetic compressor through IGBT modules and a step-up pulse transformer. The input part of the generator is equipped with an unused energy recuperation circuit, and, when the output pulse is formed, the microsecond pumping mode of the semiconductor opening switch (SOS) is realized. As a result, the complete efficiency of the generator operating into a matched load is increased from ∼40 to 60–62%. The other characteristics of the generator are as follows: the peak voltage is up to 60 kV, the current is up to 6 kA, the pulse duration is about 40 ns, the pulse repetition rate in the continuous mode is 1 kHz, and the average output power is up to 9 kW.     

High-voltage isolation transformer for sub-nanosecond rise time pulses constructed with annular parallel-strip transmission lines

A novel annular parallel-strip transmission line was devised to construct high-voltage high-speed pulse isolation transformers. The transmission lines can easily realize stable high-voltage operation and good impedance matching between primary and secondary circuits. The time constant for the step response of the transformer was calculated by introducing a simple low-frequency equivalent circuit model. Results show that the relation between the time constant and low-cut-off frequency of the transformer conforms to the theory of the general first-order linear time-invariant system. Results also show that the test transformer composed of the new transmission lines can transmit about 600 ps rise time pulses across the dc potential difference of more than 150 kV with insertion loss of -2.5 dB. The measured effective time constant of 12 ns agreed exactly with the theoretically predicted value. For practical applications involving the delivery of synchronized trigger signals to a dc high-voltage electron gun station, the transformer described in this paper exhibited advantages over methods using fiber optic cables for the signal transfer system. This transformer has no jitter or breakdown problems that invariably occur in active circuit components.     

A high-voltage pulse generator for electric-discharge technologies

The electric circuit and design of a high-volta ge pulse generator with an output voltage of ≥3 50 kV is described. The generator operates in the nanosecond range of pulse durations (~300 ns) at a repetition rate of up to 10 pulses/s in a continuous mode and is intended for electric-discharge technologies. The energy stored in the generator is ~600 J, and the energy released in a pulse is ≥300 J. A discharge of a capacitive storage through a toroidal pulsed transformer and a discharge gap is used in the generator.     

A Marx generator with a doubled output voltage

A generator of high-voltage pulses with doubling of the output voltage built according to the Marx scheme on the basis of ten stages connected in series is described. IGBT transistors are used as switches in the circuit. A specific feature of the generator circuit design is the substitution of charging diodes for charging resistors and connection of the supplying voltage through an inductor. This made it possible to double the amplitude of pulses across a load, which is proportional to the number of connected stages, and minimize the power loss during charging of storage capacitors. In an experiment performed at a supply voltage of 500 V, a pulse voltage of 7.4 kV was obtained across a load of 400 Ω.     

Generators of high-voltage pulses with a repetition rate of 50000 pulses per second

We study the schematic and mechanical features of frequency (∼50000 pulses/s) generators of high-voltage (up to 10 kV) pulses of the microsecond range. We analyze (with the purpose of decreasing energy consumed from the power network) the energy transfer process from a low-voltage discharge circuit (with insulated-gate bipolar transistors as commutators) by means of a step-up pulse transformer to the load. We implement the design of a generator with pulse front sharpening in the load (into a reactor with pulsed corona discharge) using a multigap air discharger. The maximum achieved pulse repetition rate with a sharpened front was ∼27 000 pulses/s and a voltage of ∼3 kV.     

A magnetic-thyristor pulse generator for electric-discharge technologies

A generator is described that is intended for operation in the area of electric-discharge technologies. Depending on the electrical strength of the load, the generator produces voltages of up to 50 kV, the dissipated energy of the pulse is up to 200 J, and the pulse repetition rate is up to 100 Hz. The generator is based on the direct discharge of capacitors to a discharge gap through a coaxial cable with a length of up to 200 m and without additional switching components. The circuit stabilizing the pulse energy due to recuperation of the unused energy in the filter capacitor of the power supply is used to stabilize the energy dissipated by the load.     

10kV配电网可靠性计算与分析

基于分段开关的配置情况,通过网络等值法对梅州城区10 kV配电系统的康居乙线进行了详细的可靠性计算与分析,从而得到配电线路各负荷点和系统的可靠性指标,并计算出了用户停电损失费用.经算例验证,合理配置分段开关是提高配电网可靠性的有效措施,同时表明了该算法在研究复杂配电系统方面具有很好的适用性.     

基于安时积分和无迹卡尔曼滤波的锂离子电池SOC估算方法研究

基于Thevenin等效模型建立二阶RC等效电路模型,通过混合脉冲动力功率特性测试实验获取电池脉冲放电数据,进行电池等效电路参数辨识。为弥补锂离子电池荷电状态在90%~100%区间时电池模型参数辨识拟合误差而引起其估算误差的缺陷,综合采用安时积分与无迹卡尔曼滤波估算电池荷电状态。使用硬件在环仿真测试平台及环境模拟测试平台进行电池管理系统设计,在不同工况下对电池进行荷电状态估算,结果表明荷电状态估算误差范围为-1.5%~1.0%,该方法估算精度较高,效果理想。     

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.     

A high voltage pulsed power supply for capillary discharge waveguide applications

We present an all solid-state, high voltage pulsed power supply for inducing stable plasma formation (density ～10(18) cm(-3)) in gas-filled capillary discharge waveguides. The pulser (pulse duration of 1 μs) is based on transistor switching and wound transmission line transformer technology. For a capillary of length 40 mm and diameter 265 μm and gas backing pressure of 100 mbar, a fast voltage pulse risetime of 95 ns initiates breakdown at 13 kV along the capillary. A peak current of ～280 A indicates near complete ionization, and the r.m.s. temporal jitter in the current pulse is only 4 ns. Temporally stable plasma formation is crucial for deploying capillary waveguides as plasma channels in laser-plasma interaction experiments, such as the laser wakefield accelerator.     

A low-frequency high-power arbitrary-shape voltage pulse generator

A circuit diagram and design of the arbitrary-shape bipolar voltage pulse generator with amplitudes up to 800 V and a peak output on a matched load of 400 kW are described. The generator is based on car rechargeable batteries and power insulated-gate bipolar transistors (IGBTs). Results of the experiments aimed at producing high-power harmonic signals with frequencies of 50 Hz and 1 kHz are presented.