Installation for air cleaning from organic impurities by plasma formed by barrier discharge of nanosecond duration

A prototype installation for air cleaning by plasma, which consists of a barrier-type discharge reactor and a high-voltage nanosecond-pulse supply generator, which is based on drift step recovery diodes, is considered. A stable corona-type barrier discharge was obtained at a 3-kHz supply-pulse repetition frequency. The discharge remained nonlocalized even at a small gas-discharge gap (∼6 mm) due to a short (∼25 ns) pulse duration, which allows a quite uniform effect on the air flow. The high rise rate (∼6 kV/ns) of the applied supply voltage pulses determines the high voltage amplitude (∼25 kV) at the reactor at the breakdown moment and allows maintenance of high electric-field intensity and a high intensity of plasma chemical processes. Thus, an electrical power lower than 8 W is required at the reactor input to produce 1 g of ozone per hour. The concentration of methylmercaptan in air during waste-water smell deodorizing at State Unitary Enterprise “Vodokanal of St. Petersburg” was reduced down to an allowable level of 0.5 mg/m³ at the electrical power consumption no higher than 0.25 W per cubic meter of air.     

Semiconductor formers of high-voltage pulses of nanosecond duration

A small former of high-voltage pulses of nanosecond duration based on new semiconductor devices—deep-level dynistors (DLDs)—is described. The former has been developed on the basis of the Marx voltage-multiplication principle and allows formation of 8-kV voltage pulses across an 8-Ω load at a 2.5-kV input-voltage level. A DLD-based former with an output diode opening switch based on assemblies of drift step-recovery diodes connected in series is described. The results of its being tested are presented. Voltage pulses with an amplitude of 25 kV and a rise time of 1 ns are obtained across a 100-Ω load.     

Detection of x-ray emission in a nanosecond discharge in air at atmospheric pressure

Measurement of x-ray emission is an important parameter to investigate runaway behavior of fast electrons produced in nanosecond-pulse gas discharge. An online detection system of x rays is described in this paper, and the system consists of an x-ray detector with NaI (Tl) scintillator and photomultiplier tube, and an integrated multichannel analyzer. The system is responsible for detecting x-ray emission signal, processing the detected signals, and scaling the energy distribution. The calibration results show that every channel of the detection system represents a given x-ray energy and various x rays can be divided into different energy ranges between 10 and 130 keV. For a repetitive nanosecond-pulse breakdown between highly nonuniform gaps in open air, an energy distribution is obtained using the online detection system. It shows that the x-ray emission is a continuous spectrum and the x rays of above 60 keV dominate in the detected energy distribution.     

Analysis of ultrasonic waves excited in a metal plate by nanosecond laser pulses

Laser excitation of ultrasonic waves in ferromagnetic plates has been experimentally studied. The obtained results can be recommended for use in the development of methods and equipment for testing thin-walled metal articles.     

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.     

A source of short X-ray pulses

A small-sized source of short X-ray pulses is described, whose basic components are a three-electrode X-ray tube operating at 30 kV and 0.5 A and a fast GaAs modulator connected coaxially to the tube grid. The limiting operating parameters of the source are a subnanosecond pulse duration and a pulse repetition rate as high as 100 kHz.     

A high-power semiconductor switch of high-voltage pulses with a rise time of nanosecond duration

The results of studies of new fast-acting semiconductor devices—deep-level dynistors intended for use in high-power devices of nano-and microsecond pulsed-power technology—are presented. The possibility of switching multikiloampere current pulses having a rise rate of 200 kA/μs with the use of a single device with a 12-mm-diameter structure is shown. A high-power switch based on an assembly of dynistors with an operating voltage of 12 kV connected in series is described. The switch is capable of switching current pulses with a 1200-A amplitude and a 4-ns rise time.     

Low-pressure gas-discharge current interrupters in a generator of high-voltage nanosecond pulses with an inductive energy storage

Designs of grid units with slotted and multiple-aperture configurations of holes that allow an increase in the stability of the current-cutoff process and a reduction in the time to turn the device off in a high-voltage pulse generator with an inductive energy storage were created. Compared to a TGI2-500/20 thyratron, these designs made it possible to reduce the time instability of the instant of the current interruption by factors of 2 and 5 for switches with the multiple-aperture and slotted configurations of the grids, respectively. These constructions allowed the minimum time for disabling a device to be reduced by 25%.     

A megavolt frequency generator pulses with an FWHM duration of 30 ns

A generator of a pulse voltage with an amplitude of up to 1 MV based on a ten-stage voltage multiplier is described. The generator contains a control panel, a unit for periodical triggering of spark gaps in the generator stages, and a rectifier outputting a voltage of ± 50 kV for charging capacitors in stages. The generator has an output discharge capacitance of 500 pF, a stored energy of 250 J, a self-inductance of <0.7 μH, a guaranteed service life of 10⁵ charging-discharging cycles, a rise time of the first voltage half-wave of 15 ns at a load of 200 pF, and a repetition rate of 1 Hz. To reduce the self-inductance of the source, insulating housings of capacitors and spark gaps are used in its layout.     

Adjustment of the nanosecond laser pulse duration by using a carbon nanotube suspension

It is shown that the scanning of an optical cell with an aqueous suspension of carbon nanotubes along the optical axis of a focused laser beam leads to a smooth change in the duration of nanosecond laser pulses transmitted through the suspension. Pulses shorten owing to the pulse trailing edge cutoff, when the cell approaches the beam waist. In experiments, pulses of a YAG:Nd³⁺ laser with passive Q-switching and duration of 16 ns were continuously controlled in the range 16–10 ns.     

Possibilities for reducing the duration of acoustic pulses generated by a piezoelectric plate using a damper or an electric <Emphasis Type="Italic">RL</Emphasis> circuit for a plate excited by electric pulses of different durations

Calculation formulas were obtained for determining the shape of an acoustic pulse radiated by a piezoelectric plate that has a mechanical damper and a correcting electric circuit and is excited by electric pulses with durations that are multiples of an integer number of half periods at the antiresonance frequency ω₀. Calculations were performed for particular cases when either an electric circuit or a damper is present. The optimal parameters of the electric circuit that provide the shortest duration of radiated signals were determined. The durations and amplitudes of radiated signals obtained using the damper or the electric circuit were compared. Conclusions concerning the degree of efficiency of applying an electric RL load were made.     

Correction of shape and energy compression of high-voltage nanosecond pulses by compact converters with a traveling wave mode

The results of investigations of converters ensuring correction of the shape and energy compression of high-voltage (～200 kV) pulses with durations of several nanoseconds and the formation of pulses with subnanosecond rise times across a load of ～50 Ω are described. The converters are assembled on the basis of forming and transmitting coaxial lines and a high-pressure nitrogen spark gap. Correcting devices are open-circuit strip-line stubs connected to different points of the transmitting or forming line. Depending on the stub connection point, a series or parallel discharge of the forming line and stub to the load is initiated after switching of the spark gap. As a result, the pulse may become either longer or shorter; in the latter case, its amplitude increases. The design of the stubs built into the insulating gap of the coaxial line does not increase the size of the device at all.     

Fixation for biological ultrastructure. II. Cross-linking of bovine serum albumin by nanosecond pulses of ionizing radiation

Very large doses of ionizing radiation were delivered quickly to concentrated albumin solutions by pulses of 500 keV in air. The electrons penetrated the aluminium foil bottom of the test cell and into the solution. A dose of 4.6 Mrad (4.6 × 10⁴ Gy) produced a gel in the albumin solution comparable to the long-term effect of 0.36% glutaraldehyde in the same albumin solution. The cross-links created by the radiation leading to gel formation are probably irreversible and quite different from those leading to gelation in the glutaraldehyde-albumin reaction. Single large pulses of ionizing radiation may be useful for fast fixation of cells and tissues for microscopy.     

Investigation of the electrical strength of liquid dielectrics in vacuum under the action of high-voltage nanosecond pulses

The results of an experimental study of the electrical strength of insulators that are coated with a thin liquid-dielectric layer (1?C2 mm) are presented. Studies were performed in a vacuum at a pressure of 10^?4?C10^?5 Torr and a high-voltage pulse duration of ??100 ns on an experimental setup, which is based on a PG-1 high-voltage nanosecond generator with an output voltage of up to 500 kV at a load of up to 40 ??. It was established that a castor or transformer oil coating on an insulator allows an increase in the amplitude of a voltage pulse, which is applied to the insulator, by a factor of at least 1.7 as compared to the clean insulator without its breakdown over the surface in vacuum.     

Modifying the surfaces of fluorocarbon polymer implants in the plasma of a high-voltage nanosecond discharge

The possibility in principle is shown for rapidly and efficiently modifying the surface of medical articles made of polytetrafluoroethylene (PTFE) by placing them in a bulk plasma discharge formed in a highly overvoltage gap. As an example, by processing PTFE films with nanosecond discharges at a frequency of 3 kHz over a few seconds, it is possible to substantially improve the conditions for cytoadherence and increase the permeability of an implant, which is an important factor for its integration into adjacent tissues.     

Influence of discharge gap on the discharge stability in a short vacuum arc ion source

The influence of the discharge gap between cathode and anode on the discharge stability in a short vacuum arc (SVA) ion source is presented in this paper. Planar cathode and cylindrical hollow anode made of titanium are investigated. There is a great need in present accelerator injection research for SVA source to produce the small deviation of the ion current beam. Current research shows that increasing the short discharge gap can reduce the level of ion current deviation and ion charge deviation from 29% and 31% to 15% and 17%, respectively. A microplasma plume generation mechanism in SVA and scanning electron microscopic results can be used to explain this interesting phenomenon.     

A high-power generator of nanosecond pulses with an amplitude of up to 500 kV and a repetition rate of up to 50 Hz

A pulsed-power high-voltage generator, which is combined with an electric-discharge chamber, is designed for selective disintegration of quartz raw minerals and other nonconductive natural and artificial materials. The main parameters of the generator are as follows: the voltage-pulse amplitude, up to 500 kV; the discharge-current amplitude, up to 30 kA; the duration of current pulses (the half-period an oscillatory discharge), 70–90 ns; and the pulse repetition rate, up to 50 Hz. The generator is characterized by a high efficiency, a long service life, the possibility of long continuous operation, and the fulfillment of the electromagnetic compatibility requirements. The experience of the operation of three constructed installations testifies to their high reliability: the number of accumulated pulses in a typical mode (450 kV, 20 Hz) exceeded 108 pulses without a repair or replacement of units.     

X荧光光谱法测定玩具饰品中的重金属含量

采用X荧光光谱法测定了塑料、金属、陶瓷等多类玩具饰品表面中的重金属Cr、Cd、Pb、Hg含量。仪器预热初始化后,对不同大小,不同形状,不同属性的样品无需做任何的预处理,直接无损测定其表面重金属的含量。单个样品测定时间为2～3分钟,可连续不间断测定,检测限低,可达2mg/kg,相对标准偏差低于4.6%。所用仪器为国产仪器,仪器成本及运行和维护成本低,应用于现场实时分析,便于推广。该法具有分析速度快、操作简单、对样品无任何损坏等特点,用于玩具饰品中重金属Cr、Cd、Pb、Hg含量的测定,简单,实用。     

X-ray analysis and mapping by wavelength dispersive X-ray spectroscopy in an electron microscope

A compact and easy-to-use wavelength dispersive X-ray spectrometer using a multi-capillary X-ray lens attached to a scanning (transmission) electron microscope has been tested for thin-film analysis. B-K spectra from thin-film boron compounds (B4C, h-BN, and B2O3) samples showed prominent peak shifts and detailed structural differences. Mapping images of a thin W/Si double-layer sample resolved each element clearly. Additionally, a thin SiO2 film grown on a Si substrate was imaged with O-K X-rays. Energy and spatial resolution of the system is also discussed.