An PBЕ-73C vacuum spark gap with a control circuit based on an inductive energy storage

The design and operating principle of a small (50 mm in diameter and 100 mm in height) РВЕ-73C vacuum spark gap are described. It is shown that it can be efficiently switched using a control circuit with a low (∼900 V) supply voltage, which is based on an inductive energy storage and a diode opening switch that forms a high-voltage igniting pulse with a rise time of nanosecond duration. The РВЕ-73C switching process is investigated at different rise times of igniting voltage pulses and different igniting current amplitudes. The results of tests of the spark gap operating in regimes of switching current pulses with an amplitude of 12 kA and a rise time of 800 ns are presented.     

Switches of High-power Current Pulses with a Submicrosecond Rise Time on the Basis of Series-connected IGBT Transistors

The results of comparative investigations of assemblies of series-connected IGBT transistors (IRGPS60B120KD) with control circuits that are based on pulse transformers and ADuM21N microcircuits, which have a high insulation strength, are presented. The conditions for efficient switching of high-power current pulses with a submicrosecond rise time are determined. A small switch with an operating voltage of 12 kV that consists of two parallel-connected transistor assemblies is described. It provides switching of microsecond current pulses with an amplitude of 500 A and a rise time of 200 ns at a frequency of 100 Hz under natural cooling. The possibility of scaling the results is shown.     

Excitation of high-intensity laser radiation of semiconductor targets by a subnanosecond electron beam

The results of the excitation of СdS semiconductor targets by a subnanosecond electron beam (EB) with an electron energy of 60–230 keV are presented. The maximum intensity of laser radiation from targets for a 1-mm EB diameter exceeded 10⁷ W/cm² at an efficiency of ~10%. Lasing was initiated at the leading edge of the EB current; laser radiation then reproduced the shape of the excitation pulse. At low excitation levels, a single-mode lasing regime with the wavelength λ = 522 nm was observed. The maximum power of laser radiation (10 MW) was achieved on a multielement CdS semiconductor target. The duration of laser pulses changed in the range of 100–500 ps.     

A triangular-shaped current used in devices for reversing neutron polarization

Possibilities of using a triangular-shaped current in an inductance coil in devices for reversing neutron polarization (flippers) are considered. Tests of the flipper with a triangular-shaped current on the neutron beam demonstrated that the efficiency of neutron spin flipping is not worse (within a measurement error) than the efficiency of a flipper with a sinusoidal current. It was shown theoretically and confirmed in practice that setting (switching on) and drop (switching off) of the current in the coil can happen “instantly“ (with an accuracy of up to a period) in response to switching-on and switching-off of the control signals.     

A comparative study of switching possibilities of silicon diodes with different axial distribution shapes of recombination centers

Three groups of silicon p ⁺-n-n ⁺ diodes with a small turn-off time ensured by charged particle irradiation were studied in the high-power (3 kA) and short (50 μs) current pulse switching modes. The diodes of the first group were irradiated by electrons with a 550-keV energy, those of the second group were irradiated by protons with a 2.5-MeV energy and then by electrons with a 6-MeV energy, and those of the third group were irradiated by electrons with a 6-MeV energy. The studied diodes have a 16-mm semiconductor element diameter and 3-kV maximum permissible disabled voltage. The radiation doses were selected in such a way as to obtain an approximately equal current carrier lifetime near the p ⁺-n junction (4 μs), measured by the Lacks method, when the forward current density is 1 A/cm². It was determined that, when diodes of the first group change to the OFF position, the peak power of energy losses is two and more times smaller than that of diodes of the second and third groups, when they are switched off. The diodes of the first group also feature a substantially smaller voltage, when the forward current is at maximum (by two times as compared with diodes of the second group and by seven times as compared with diodes of the third group) and significantly smaller (by several times) voltage spike at a sharp forward current increase instant.     

High-frequency pulse generators based on SOS diodes with subnanosecond current cutoff time

Compact high-voltage generators with a pulse power of 100–500 MW, an output voltage of 150–400 kV, a pulse duration of 3–6 ns, and pulse repetition rates of 300–400 Hz and up to 5 kHz in a steady-state and a 30-s-long burst mode, respectively, are described. The output power-amplification unit is based on an inductive storage and SOS diodes with subnanosecond current cutoff time. Physical processes in the semiconductor structure of a SOS diode operating in the subnanosecond current cutoff mode are considered. The generator circuit designs and their test results are presented.     

Small switches of high-power microsecond pulses on the basis of high-voltage integrated pulse thyristors and reverse switch-on dynistors

A high-voltage switch on the basis of a small unit of series-connected high-voltage integrated pulse thyristors (HVIPTs), which were developed at the Ioffe Physical Technical Institute, was designed and investigated. At a power voltage of 25 kV, current pulses of microsecond duration with an amplitude of 2.8 kA and a rise time of 0.8 μs were switched. The attained current density through an HVIPT (5.6 kA/cm²) appreciably exceeds the permissible current density for conventional thyristors. It is shown that the developed HVIPT unit can be used in the triggering circuit of a high-power assembly of reverse switch-on dynistors (RSDs) at an operating voltage of 25 kV, which consists of 14 series-connected dynistors with a diameter of their structures of 24 mm. The RSD switch with a triggering circuit on the basis of HVIPTs allowed switching of rapidly rising current pulses with an amplitude of 20 kA and a duration of 150 μs. The small dimensions of the HVIPT unit (4 × 10 × 32 cm) and the RSD assembly (7 × 7 × 34 cm) determine the wide prospects for using them in high-power pulse technology.     

A Pseudospark Gap in the Inductive-Energy-Storage Circuit

A pseudospark gap is described that is capable of interrupting a current of up to 1 kA and shaping voltage pulses with an amplitude of up to 110 kV and rise time of 100 ns. Analytical expressions for calculating the energy released in the device at the switching-off stage and the efficiency of the generator with an inductive energy storage system are obtained. The characteristics of the pseudospark gap and of a similar-design thyratron connected in the same circuit are compared. It is found that the turn-off time of the pseudospark gap is shorter than that of the thyratron by a factor of 2.5.     

A 1-MJ capacitive energy storage

A capacitive energy storage is intended for generating high-power current pulses. The setup consists of two capacitive energy storage modules, a control console, and a cable collector for connecting a load to the setup. Each module is a capacitive energy storage with a 0.5-MJ stored energy and 18-kV voltage, which is based on eight capacitor cells with reverse switch-on dynistors as switches. The module volume is 1.3 m³. The semiconductor switches in the capacitor cells are activated by light pulses, which are transmitted from the control console through fiber-optic cables. The unit is designed for operating in the programmable discharge mode, at which the semiconductor switches in the capacitor cells are switched on nonsimultaneously but in accordance with a specified program. When the discharge of all the cells is switched on simultaneously and the load is short-circuited, the maximal amplitude of the output current pulse is 800 kA. The rise time of the discharge current pulse of the cell is 150 μs.     

Thermal imaging diagnostics of powerful ion beams

Thermal imaging diagnostics of the total energy of a pulsed ion beam and energy-density distribution over the cross section is described. The diagnostics was tested on the TEMП-4M accelerator in the conditions of formation of two pulses: (i) the first plasma-forming pulse is negative (300–500 ns, 100–150 kV) and (ii) the second generated one is positive (150 ns, 250–300 kV). The beam composition includes carbon ions (85%) and protons, and the power density is 0.2–3.0 J/cm² (for various diodes). The diagnostics was applied in studies of the powerful ion beam, formed by an ion diode with self insulation (two-pulse mode) and external magnetic insulation in the single-pulse mode. The diagnostics was intended to measure the beam energy density in a range of 0.05–5.00 J/cm² in the absence of erosion and ablation processes on the target. When an infrared camera with a 140 × 160-pixel matrix is used, the spatial resolution is 0.9 mm. The measurement time does not exceed 0.1 s.     

A Multichannel Automatized System for Measuring Current Pulses in the LIA-30 Electron Accelerator

In the LIA-30 high-power linear pulsed induction electron accelerator (40 MeV, 100 kA, 25 ns), the energy is stored, and pulses of the accelerating voltage are shaped by 288 water-insulated radial lines arranged in succession along a common air-free acceleration channel. The lines are simultaneously charged up to 500 kV from 72 shielded Marx generators. To measure the parameters (amplitude, pulse shape, pulse rise time, pulse fall time, and pulse duration) of the synchronized pulses of the charging current with amplitudes as high as 60 kA and duration of 0.85 s in each of the 72 charging circuits, an automatized measuring system is used. The current pulse is sensed at the output of each generator by a self-integrating Rogovsky coil galvanically isolated from the generator. The signal from the coil is transmitted over a cable to an analog-to-digital converter, sampled with a period of 50 ns, and recorded in memory. Upon operating the accelerator, the signals are reproduced in succession or selectively on the display screen, and their shapes are compared to the shape of a standard pulse.     

An experimental setup for exciting semiconductors and dielectrics with picosecond electron-beam and electric-field pulses

An experimental facility for forming high-voltage pulses with amplitudes of 30–250 kV and durations of 100–500 ps and electron beams with a current density of up to 1000 A/cm² is described. The facility was built using the principle of energy compression of a pulse from a nanosecond high-voltage generator accompanied by the subsequent pulse sharpening and cutting. The setup is equipped with two test coaxial chambers for exciting radiation in semiconductor crystals by an electron beam or an electric field in air at atmospheric pressure and T = 300 K. Generation of laser radiation in the visible range under field and electron pumping was attained in ZnSSe, ZnSe, ZnCdS, and CdS (462, 480, 515, and 525 nm, respectively). Under the exposure to an electric field (up to 10⁶ V cm^?1), the lasing region was as large as 300–500μm. The radiation divergence was within 5°. The maximum integral radiation power (6 kW at λ = 480 nm) was obtained under field pumping of a zinc selenide sample with a single dielectric mirror.     

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.     

开环PWM控制储能电容恒流充电方法

针对储能电容闭环PWM控制恒流充电和LC谐振式恒流充电的不足,提出了开环PWM控制储能电容恒流充电方法。通过对充电过程的计算机仿真,得出用于恒流充电开环PWM控制的占空比数据。应用中设计的开关电源将系列占空比数据存入单片机,然后顺序给出进行开环PWM控制,能够给800μF电容快速充电到1000V。根据实际测量的电流波形,对可控的占空比大小和变化趋势作适当的调整,能够控制充电电流达到理想快速短时恒流充电方式。     

A high-current nanosecond electron accelerator with a semiconductor opening switch

A compact nanosecond electron accelerator with an output energy of up to 4000 keV, a pulsed power of 100–180 MW, a beam current of 0.25–1.1 kA, and a pulse energy of 5–7 J is described. The accelerator operates with a pulse repetition rate of 200 Hz and ensures an average beam power of up to 1 kW. A nanosecond generator with a solid-state switching system, which is based on magnetic stages of pulse compression and a semiconductor opening switch, is used as a supplying device. The design and electric circuit of the accelerator are described, and test results are presented.     

Experimental study on energy consumption of energy-saving pulse power for WEDM

Wire electrical discharge machining (WEDM) is widely used in aerospace, mold manufacturing, automotive, and other fields. But now, traditional WEDM pulse power contains current-limiting resistor, and its energy utilization rate is low. Meanwhile, discharge energy of WEDM pulse power cannot be accurately controlled, and there is no unified understanding of distribution about discharge energy. In this paper, the pulse power improves energy utilization rate by removing current-limiting resistor and adopting single-arm pulse width modulation control method which controls peak current and modulates long short-circuit pulse width. Experiments proved that the energy-saving pulse power improves energy utilization rate by, approximately, 67.6 % than traditional pulse power. The paper analyzed a single-pulse energy waveform of the energy-saving pulse power and calculated each spark pulse energy and total energy provided by pulse power. It found that gap spark discharge energy only accounted for about 51 % of the energy provided by the pulse power, and other energy was mainly consumed in switching loss of power switch and parasitic resistance of pulse power.     

High-current pulse switching by thyristors triggered in the impact-ionization wave mode

The operation of a thyristor switch triggered in the impact-ionization wave mode was investigated. The switch contained two series-connected Т253-800-24 thyristors of the tablet design with a semiconductor- structure diameter of 56 mm. When a triggering pulse is applied to the switch at a voltage rise rate dU/dt of more than 1 kV/ns, the transition time of the thyristors to the conducting state was shorter than 1 ns. It was shown that the maximum amplitude of the no-failure current increases with an increase in dU/dt at the triggering stage. The possible mechanism of the influence of the dU/dt value on the thyristor breakdown current is discussed. In the safe operating mode at dU/dt = 6 kV/ns (3 kV/ns per single thyristor), the switch discharged a storage capacitor with a capacitance of 1 mF, which was charged to a voltage of 5 kV, through a resistive load of 18 mΩ. The following results were obtained: the discharge-current amplitude was 200 kA, the initial current rise rate was 58 kA/μs, the pulse duration (FWHM) was 25 μs, and the switching efficiency of 0.97.     

High-Power Generator of Long Quasi-Rectangular Pulses with Nanosecond Rise Times Based on Inversely Recovered Diodes

The operating principle of a new semiconductor device, an inversely recovered diode, is considered. After passing a small direct current in the forward direction, the diode is capable of rapidly (a few nanoseconds) interrupting a high-power reverse-current pulse and switching it to a parallel load circuit. A high-power pulse generator based on an inversely recovered diode and transistor switch is described. The generator forms quasi-rectangular voltage pulses with an amplitude of 500 V, a rise time of 4 ns, and a variable duration adjusted from several tens to several thousands of nanoseconds across a load of 10 .     

Prospects of using reverse switch-on dynistors in the modes of switching submicrosecond current pulses

The results of studying reverse switch-on dynistors (RSDs) with an operating voltage of 2 kV and a 12-mm diameter of structures that switch high-power current pulses of submicrosecond duration are presented. It is shown that, in this time interval, the switching energy losses in RSDs are much lower than those for thyristors and IGBT transistors having almost the same area of semiconductor structures and a maximum acceptable blocked voltage. The switching time at which the use of RSDs becomes low-efficient is determined (<0.4 μs).     

A plasma cathode for a radio-frequency gun

A plasma ferroelectric cathode is used to form electron beams with a high pulse charge and a high charge in an electron bunch in an rf electron gun of a 10-cm wavelength range. The design of the cathode is described, and the results of calculations of the densities of the cathode-emitted and the gun-outputted currents are presented. The operation of the cathode in the rf gun was studied experimentally: the electron energy, the pulse current, and the transverse emittance of the beam were measured. The electron beam obtained at the output of the single-resonator gun had a pulse current of up to 10 A, a pulse duration of 60 ns, and an electron energy of ?500 keV. The normalized beam emittance was 40 mm mrad.