Duration Of Leading Edge Research Articles

RESEARCH OF THE INDIUM ARSENIDE IMPULSE PROPERTIES

Indium arsenide is a promising material for creation of high-performance electronic and optoelectronic devices. A high level of knowledge of indium arsenide properties will make it possible to predict the potential possibilities of its application, as well as multicomponent semiconductors based on it. The problem of studying the properties of InAs in the regime of a strong electric field is relevant.
 In scientific and technical sources, data on the impulse properties of indium arsenide in the regime of a strong electric field are poorly presented. The purpose of the work is to study the field-velocity dependence in the pulsed mode of a strong electric field and to analyze the response to changes in its amplitude, pulse duration, and leading edge duration.
 The method of relaxation equations was used to analyze the field-velocity characteristic in the regime of a strong electric field. In the electric field static regime, the highest value of the drift velocity was 3·105 m/s (with a field amplitude of 2 kV/cm), in the saturation section it was 0.9·105 m/s.
 An analysis of the field-velocity dependence in the pulsed mode of a strong electric field showed that with an increase in the field amplitude, the maximum value of the drift velocity increases, and the duration of the "overshoot" shortens. Fields of 5–30 kV/cm correspond to an increase in the highest velocity value by a factor of 2.7–8. The spatial distribution of the drift velocity gave an estimate of the average velocity and distance traveled by charge carriers at different field values.
 An increase in the duration of the leading edge duration of the field pulse caused a delay in transient processes. At 12 kV/cm < E, the peak value of the drift velocity additionally decreases. The duration of a strong electric field pulse has a significant effect only at values less than the formation time of the drift velocity maximum. Such values of the pulse duration lead to a decrease in the rate of drift and relaxation processes.
 Comparison of the field-velocity dependences in the high-field pulsed mode showed that the maximum value of the drift velocity of InAs electrons exceeds the corresponding values: GaAs, InP – by several times; GaN - an order of magnitude. The duration of the “ overshoot ” of the drift velocity for InAs is somewhat longer than for GaAs, InP, GaN.

Evaluation of the Electric Field Strength in a Pre-Breakdown Ionization Wave in a Long Discharge Tube from the Emission Spectrum

The paper presents the results of studying the characteristics of a slow ionization wave (IW) arising at the initial stage of breakdown in a long discharge tube under reduced pressure. The discharge tube is a Philips TUV-30W mercury lamp with an electrode spacing of 80 cm and an inner diameter of 23 mm. The tube is filled with argon at a pressure of 2–4 Torr (nominal data) and mercury vapor. One of the electrodes is grounded, and, to the second one, positive or negative voltage pulses with an amplitude of 2 kV, a leading edge duration of ≈0.5 μs, and a repetition frequency of 1 Hz are applied. The IW velocity and the time dependence of the intensities of the Ar, Ar+, and Hg lines in the IW at different distances from the high-voltage electrode are measured. It is shown that the velocity of a positive IW (3 × 107–5 × 107 cm/s) is higher than the velocity of a negative IW (1 × 107–1.8 × 107 cm/s). The magnitude of the electric field in the front of an IW is evaluated from the comparison of the measured and calculated intensity ratios of the Ar, Ar+, and Hg lines. It is shown that, in a positive IW, the magnitude of the reduced electric field (260–450 Td) is noticeably larger than in a negative one (120–165 Td).

Frequency and energy characteristics of a Cu – Ne laser at different durations of the leading edge of the excitation pulse

The lasing characteristics of a copper vapour laser in a tube with forced heating, having a length of 50 cm and a diameter of 2 cm, excited by a train of pulses are investigated. Comparative studies of the frequency and energy characteristics of the laser are performed with a leading edge duration of the excitation pulse of ∼25 ns (when the capacitance discharges through a thyratron and a magnetic compression line) and ∼3 and 1 ns (using circuits with a high-speed switch – kivotron). It is shown that a decrease in the leading edge duration gives rise to an increase in the optimal pulse repetition rate up to ∼30 kHz, the generation efficiency up to 3.2 % and the generation power per unit length over 100 W m−1. The results obtained confirm the concept of limiting the frequency and energy characteristics of a copper vapour laser due to the insufficient rate of energy input into the plasma at high prepulse electron concentrations.

Metrological Assurance of Devices Intended to Measure the Parameters of Pulsed Electric and Magnetic Fields of Natural and Artificial Origin

Issues are examined related to the improvement of State Primary Special Standard GET 148–2013, for units of pulsed electric and magnetic field strength having a pulse leading-edge duration in the range from 0.1 to 10.0 nsec, as well as the improvement of secondary standards. The goal of the improvement is to provide metrological assurance of devices intended to measure the parameters of pulsed electric and magnetic fields of natural and artificial origin in the range up to 1 MV/m with a pulse leading-edge time not exceeding 100 psec.

The formation of correlated states and optimization of the tunnel effect for low-energy particles under nonmonochromatic and pulsed action on a potential barrier

We consider peculiarities of the formation of a coherent correlated state (CCS) of a low-energy particle under frequency modulation of parameters of a harmonic oscillator that contains this particle by a broadband nonmonochromatic or asymmetric pulsed action. It is shown that in the case of modulation with frequency-normalized intensity, the maximum efficiency of CCS formation corresponds to a narrow-band action, while broadband modulation is optimal for the action with a constant spectral density. As in the case of monochromatic modulation, the maximum correlation coefficient, |r|max, under the nonmonochromatic action corresponds to parametric resonance at frequency Ω ≈ 2ω0. Under a pulsed action, the maximum efficiency of CCS formation and, hence, the maximum probability of the tunnel effect, correspond to pulsed modulation with a short leading edge and a long trailing edge. In particular, under the action of a pulsed magnetic field with an amplitude of 10 kOe and the leading edge duration of 2 × 10–7 s on a gas with deuterium ions, a CCS can be formed with the correlation coefficient |r|max ≈ 0.9998, for which the tunneling effect probability under the dd interaction at temperature T ≈ 300–500 K increases from Dr = 0 ≈ 10−80 to \({D_{|r{|_{\max }} = 0.9998}} \approx 0.1\). This process can occur in a gas with particle number density n < ncr ≈ 1017 cm−3. The method of CCS formation makes it possible to explain the results of an experiment in which substantial isotope changes were detected when a pulsed electric current and magnetic-field generation occurred.

Underwater Acoustic Altimeter

A model for determining the reflected-pulse shape during vertical sounding of the sea surface by an underwater ultrasonic sonar with a wide antenna pattern is developed. The reflected-pulse shape dependence on the parameters of an underwater acoustic altimeter and the measurement schemes is studied. The wave-height retrieval algorithm whose input parameter is the reflectedpulse leading-edge duration is developed. The algorithm efficiency is confirmed by numerical simulation. The obtained formula for the wave height involves the coefficients which depend on many characteristics among which the submersion depth, the beamwidth, and the soundingpulse duration are the main parameters. Therefore, the formula should be specified according to variations in the measurement scheme and the acoustic-system parameters.

Digital Multiparameter System for Characterizing the Neutron-Gamma Field in the LR-O Experimental Reactor

Abstract The present paper points toward the possibility of reducing the proportion of analog processing in an apparatus employed to measure the neutron and photon energy spectra. The digitization of the detector output pulses makes it possible to process the information contained in the pulses either instantaneously or subsequently. The present paper deals with the method of digitizing the leading edge of the pulses generated by a stilbene organic scintillator or an NE-213 scintillator. The neutron versus gamma discrimination can be carried out on the basis of the pulse leading edge duration. Coping with this task requires a digitizer featuring quite a high sampling frequency, which must exceed 1 GHz. The requirements for the amplitude digitization frequency are less severe, however, the amplitude resolution must be better than 8 bits. Both of the above requirements can be met with present-day components. The digitization is expected to result in reducing the apparatus size and improving its functionality.

Effect of the pulse leading-edge time on the dielectric strength of a vacuum gap

Optimal regimes for electrode conditioning in a vacuum by applying voltage pulses with different waveforms are considered. For nanosecond pulses with a constant duration (t p = const), the impulse dielectric strength for an oblique voltage wave is shown to be more than four times higher than for a rectangular pulse with an infinitely short leading-edge duration. The dependences of the dielectric strength on the conditioning pulse duration in the range 10−10 < t p < 10−3 s for pulses with different rise rates are obtained. The dielectric strength increases from 2 × 107 V/m for microsecond pulses to 1010 V/m for subnanosecond pulses.

Influence of ultrashort pulses of electromagnetic radiation on parameters of metal-insulator-semiconductor structures

The effect of pulsed electromagnetic radiation with a leading-edge duration of 1.4×10−9 s and a total pulse duration of ∼11.5×10−9 s, a repetition rate of 10 kHz, and various pulse energies (≲2.4×10−4 J) on Al/SiO2/Si structures is studied. Capacitance-voltage characteristics of such structures were measured before, during, and after exposure to ultrashort pulses. Changes dependent on the pulse energy caused by insulator polarization and a transformation of the nonequilibrium defect structure of the interface with the semiconductor as a result of the irradiation were found, as well as irreversible changes associated with a breakdown observed after the radiation was switched off.

Evolution of a capillary discharge induced by a semiconductor current generator

Results are presented from the intermediate stage of work on creating a current generator in a circuit with an inductive energy storage and a semiconductor opening switch made of 40 SDL-800 diodes. A six-diode generator prototype has been created with a current pulse amplitude of ∼4.5 kA and a leading edge duration of ∼10–20 ns at an inductive load of 30–35 nH. The generator was used to study discharges in capillaries filled with argon or hydrogen. It is shown that, in a 2-mm-diameter capillary, the initial azimuthal asymmetry of a structure arising during the breakdown ceases as the discharge evolves, whereas in a 0.8-mm-diameter capillary, it is retained. Time-resolved spectroscopic studies of the plasma reveal the presence of line emission of highly ionized argon (ArVII and ArVIII) in the hottest phase of the discharge, which indicates that a temperature of 20–40 eV has been achieved.

A High-Voltage Pulse Generator with Inductive Energy Storage and Thyratron

A high-voltage pulse generator with an inductive energy storage is described. Its operation is based on the current interruption by a thyratron. It was shown that a TГИ2-500/20 thyratron is capable of reliably interrupting the current with an amplitude of 800–850 A in an inductive energy storage, forming from a low-voltage (0.5–2 kV) power source voltage pulses with an amplitude of up to 90 kV and leading edge duration of 200–250 ns at the load.

Influence of the chemical composition of the hydrogen-containing component in an RH active medium and of the initiation method on the parameters of a pulsed chemical SF6–RH laser

The influence of the composition of the active medium on the lasing characteristics and energy deposition efficiency was studied under conditions of electron-beam and electric-discharge initiation in SF6–H2 and SF6–HI pulsed hydrogen fluoride chemical lasers.The best radiation energy characteristics were achieved for an SF6–HI active medium using electron-beam initiation and for an SF6–H2 active medium when the pump reaction was initiated by a self-sustained volume discharge. The following pulse parameters were obtained for an SF6–HI laser:energy 1.5 J, half-height pulse duration 60 ns,and leading edge duration 20 ns.

Simulation studies in both the frequency and time domains of InGaAsP-InP avalanche photodetectors

The purpose of this brief is to analyze the relation between the physical structure of the quaternary InGaAsP avalanche photodetector and the speed of temporal response. The small-signal time-domain differential equations dealing with the current multiplication in a p-n junction structure operating in the avalanche mode are obtained. The structure is a mesa diode made of an n-type quaternary material In 1-x Ga x As y P 1-y grown on a heavily doped InP substrate. For the first time, both magnitude and phase of the frequency response are computed in a frequency band extending up to 256 GHz, from which the time-domain impulse responses are obtained. Simulation studies are performed using light pulses with an FDHM of 48.8 ps and a base duration of 97.7 ps. The FDHM of the detected waveform is less than 70 ps, and the leading edge duration is less than 100 ps.